Netdev Archive on lore.kernel.org
help / color / mirror / Atom feed
* [PATCH bpf-next 0/4] libbpf: Move CO-RE logic into separate file.
@ 2021-07-21  0:08 Alexei Starovoitov
  2021-07-21  0:08 ` [PATCH bpf-next 1/4] libbpf: Cleanup the layering between CORE and bpf_program Alexei Starovoitov
                   ` (5 more replies)
  0 siblings, 6 replies; 10+ messages in thread
From: Alexei Starovoitov @ 2021-07-21  0:08 UTC (permalink / raw)
  To: davem; +Cc: daniel, andrii, netdev, bpf, kernel-team

From: Alexei Starovoitov <ast@kernel.org>

Split CO-RE processing logic from libbpf into separate file
with an interface that doesn't dependend on libbpf internal details.
As the next step relo_core.c will be compiled with libbpf and with the kernel.
The _internal_ interface between libbpf/CO-RE and kernel/CO-RE will be:
int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
			     int insn_idx,
			     const struct bpf_core_relo *relo,
			     int relo_idx,
			     const struct btf *local_btf,
			     struct bpf_core_cand_list *cands);
where bpf_core_relo and bpf_core_cand_list are simple types
prepared by kernel and libbpf.

Though diff stat shows a lot of lines inserted/deleted they are moved lines.
Pls review with diff.colorMoved.

Alexei Starovoitov (4):
  libbpf: Cleanup the layering between CORE and bpf_program.
  libbpf: Split bpf_core_apply_relo() into bpf_program indepdent helper.
  libbpf: Move CO-RE types into relo_core.h.
  libbpf: Split CO-RE logic into relo_core.c.

 tools/lib/bpf/Build             |    2 +-
 tools/lib/bpf/libbpf.c          | 1344 +------------------------------
 tools/lib/bpf/libbpf_internal.h |   81 +-
 tools/lib/bpf/relo_core.c       | 1326 ++++++++++++++++++++++++++++++
 tools/lib/bpf/relo_core.h       |  102 +++
 5 files changed, 1473 insertions(+), 1382 deletions(-)
 create mode 100644 tools/lib/bpf/relo_core.c
 create mode 100644 tools/lib/bpf/relo_core.h

-- 
2.30.2


^ permalink raw reply	[flat|nested] 10+ messages in thread

* [PATCH bpf-next 1/4] libbpf: Cleanup the layering between CORE and bpf_program.
  2021-07-21  0:08 [PATCH bpf-next 0/4] libbpf: Move CO-RE logic into separate file Alexei Starovoitov
@ 2021-07-21  0:08 ` Alexei Starovoitov
  2021-07-21  0:08 ` [PATCH bpf-next 2/4] libbpf: Split bpf_core_apply_relo() into bpf_program indepdent helper Alexei Starovoitov
                   ` (4 subsequent siblings)
  5 siblings, 0 replies; 10+ messages in thread
From: Alexei Starovoitov @ 2021-07-21  0:08 UTC (permalink / raw)
  To: davem; +Cc: daniel, andrii, netdev, bpf, kernel-team

From: Alexei Starovoitov <ast@kernel.org>

CO-RE processing functions don't need to know 'struct bpf_program' details.
Cleanup the layering to eventually be able to move CO-RE logic into a separate file.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 tools/lib/bpf/libbpf.c | 74 ++++++++++++++++++++++--------------------
 1 file changed, 38 insertions(+), 36 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 4c153c379989..57af20574f06 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -5611,7 +5611,7 @@ static int bpf_core_spec_match(struct bpf_core_spec *local_spec,
 	return 1;
 }
 
-static int bpf_core_calc_field_relo(const struct bpf_program *prog,
+static int bpf_core_calc_field_relo(const char *prog_name,
 				    const struct bpf_core_relo *relo,
 				    const struct bpf_core_spec *spec,
 				    __u32 *val, __u32 *field_sz, __u32 *type_id,
@@ -5655,7 +5655,7 @@ static int bpf_core_calc_field_relo(const struct bpf_program *prog,
 			*val = sz;
 		} else {
 			pr_warn("prog '%s': relo %d at insn #%d can't be applied to array access\n",
-				prog->name, relo->kind, relo->insn_off / 8);
+				prog_name, relo->kind, relo->insn_off / 8);
 			return -EINVAL;
 		}
 		if (validate)
@@ -5677,7 +5677,7 @@ static int bpf_core_calc_field_relo(const struct bpf_program *prog,
 			if (byte_sz >= 8) {
 				/* bitfield can't be read with 64-bit read */
 				pr_warn("prog '%s': relo %d at insn #%d can't be satisfied for bitfield\n",
-					prog->name, relo->kind, relo->insn_off / 8);
+					prog_name, relo->kind, relo->insn_off / 8);
 				return -E2BIG;
 			}
 			byte_sz *= 2;
@@ -5827,7 +5827,7 @@ struct bpf_core_relo_res
  * with each other. Otherwise, libbpf will refuse to proceed due to ambiguity.
  * If instruction has to be poisoned, *poison will be set to true.
  */
-static int bpf_core_calc_relo(const struct bpf_program *prog,
+static int bpf_core_calc_relo(const char *prog_name,
 			      const struct bpf_core_relo *relo,
 			      int relo_idx,
 			      const struct bpf_core_spec *local_spec,
@@ -5845,10 +5845,10 @@ static int bpf_core_calc_relo(const struct bpf_program *prog,
 	res->orig_type_id = res->new_type_id = 0;
 
 	if (core_relo_is_field_based(relo->kind)) {
-		err = bpf_core_calc_field_relo(prog, relo, local_spec,
+		err = bpf_core_calc_field_relo(prog_name, relo, local_spec,
 					       &res->orig_val, &res->orig_sz,
 					       &res->orig_type_id, &res->validate);
-		err = err ?: bpf_core_calc_field_relo(prog, relo, targ_spec,
+		err = err ?: bpf_core_calc_field_relo(prog_name, relo, targ_spec,
 						      &res->new_val, &res->new_sz,
 						      &res->new_type_id, NULL);
 		if (err)
@@ -5906,7 +5906,7 @@ static int bpf_core_calc_relo(const struct bpf_program *prog,
 	} else if (err == -EOPNOTSUPP) {
 		/* EOPNOTSUPP means unknown/unsupported relocation */
 		pr_warn("prog '%s': relo #%d: unrecognized CO-RE relocation %s (%d) at insn #%d\n",
-			prog->name, relo_idx, core_relo_kind_str(relo->kind),
+			prog_name, relo_idx, core_relo_kind_str(relo->kind),
 			relo->kind, relo->insn_off / 8);
 	}
 
@@ -5917,11 +5917,11 @@ static int bpf_core_calc_relo(const struct bpf_program *prog,
  * Turn instruction for which CO_RE relocation failed into invalid one with
  * distinct signature.
  */
-static void bpf_core_poison_insn(struct bpf_program *prog, int relo_idx,
+static void bpf_core_poison_insn(const char *prog_name, int relo_idx,
 				 int insn_idx, struct bpf_insn *insn)
 {
 	pr_debug("prog '%s': relo #%d: substituting insn #%d w/ invalid insn\n",
-		 prog->name, relo_idx, insn_idx);
+		 prog_name, relo_idx, insn_idx);
 	insn->code = BPF_JMP | BPF_CALL;
 	insn->dst_reg = 0;
 	insn->src_reg = 0;
@@ -5977,6 +5977,7 @@ static int bpf_core_patch_insn(struct bpf_program *prog,
 			       int relo_idx,
 			       const struct bpf_core_relo_res *res)
 {
+	const char *prog_name = prog->name;
 	__u32 orig_val, new_val;
 	struct bpf_insn *insn;
 	int insn_idx;
@@ -5999,8 +6000,8 @@ static int bpf_core_patch_insn(struct bpf_program *prog,
 		 * verifier about "unknown opcode 00"
 		 */
 		if (is_ldimm64_insn(insn))
-			bpf_core_poison_insn(prog, relo_idx, insn_idx + 1, insn + 1);
-		bpf_core_poison_insn(prog, relo_idx, insn_idx, insn);
+			bpf_core_poison_insn(prog_name, relo_idx, insn_idx + 1, insn + 1);
+		bpf_core_poison_insn(prog_name, relo_idx, insn_idx, insn);
 		return 0;
 	}
 
@@ -6014,14 +6015,14 @@ static int bpf_core_patch_insn(struct bpf_program *prog,
 			return -EINVAL;
 		if (res->validate && insn->imm != orig_val) {
 			pr_warn("prog '%s': relo #%d: unexpected insn #%d (ALU/ALU64) value: got %u, exp %u -> %u\n",
-				prog->name, relo_idx,
+				prog_name, relo_idx,
 				insn_idx, insn->imm, orig_val, new_val);
 			return -EINVAL;
 		}
 		orig_val = insn->imm;
 		insn->imm = new_val;
 		pr_debug("prog '%s': relo #%d: patched insn #%d (ALU/ALU64) imm %u -> %u\n",
-			 prog->name, relo_idx, insn_idx,
+			 prog_name, relo_idx, insn_idx,
 			 orig_val, new_val);
 		break;
 	case BPF_LDX:
@@ -6029,25 +6030,25 @@ static int bpf_core_patch_insn(struct bpf_program *prog,
 	case BPF_STX:
 		if (res->validate && insn->off != orig_val) {
 			pr_warn("prog '%s': relo #%d: unexpected insn #%d (LDX/ST/STX) value: got %u, exp %u -> %u\n",
-				prog->name, relo_idx, insn_idx, insn->off, orig_val, new_val);
+				prog_name, relo_idx, insn_idx, insn->off, orig_val, new_val);
 			return -EINVAL;
 		}
 		if (new_val > SHRT_MAX) {
 			pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) value too big: %u\n",
-				prog->name, relo_idx, insn_idx, new_val);
+				prog_name, relo_idx, insn_idx, new_val);
 			return -ERANGE;
 		}
 		if (res->fail_memsz_adjust) {
 			pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) accesses field incorrectly. "
 				"Make sure you are accessing pointers, unsigned integers, or fields of matching type and size.\n",
-				prog->name, relo_idx, insn_idx);
+				prog_name, relo_idx, insn_idx);
 			goto poison;
 		}
 
 		orig_val = insn->off;
 		insn->off = new_val;
 		pr_debug("prog '%s': relo #%d: patched insn #%d (LDX/ST/STX) off %u -> %u\n",
-			 prog->name, relo_idx, insn_idx, orig_val, new_val);
+			 prog_name, relo_idx, insn_idx, orig_val, new_val);
 
 		if (res->new_sz != res->orig_sz) {
 			int insn_bytes_sz, insn_bpf_sz;
@@ -6055,20 +6056,20 @@ static int bpf_core_patch_insn(struct bpf_program *prog,
 			insn_bytes_sz = insn_bpf_size_to_bytes(insn);
 			if (insn_bytes_sz != res->orig_sz) {
 				pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) unexpected mem size: got %d, exp %u\n",
-					prog->name, relo_idx, insn_idx, insn_bytes_sz, res->orig_sz);
+					prog_name, relo_idx, insn_idx, insn_bytes_sz, res->orig_sz);
 				return -EINVAL;
 			}
 
 			insn_bpf_sz = insn_bytes_to_bpf_size(res->new_sz);
 			if (insn_bpf_sz < 0) {
 				pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) invalid new mem size: %u\n",
-					prog->name, relo_idx, insn_idx, res->new_sz);
+					prog_name, relo_idx, insn_idx, res->new_sz);
 				return -EINVAL;
 			}
 
 			insn->code = BPF_MODE(insn->code) | insn_bpf_sz | BPF_CLASS(insn->code);
 			pr_debug("prog '%s': relo #%d: patched insn #%d (LDX/ST/STX) mem_sz %u -> %u\n",
-				 prog->name, relo_idx, insn_idx, res->orig_sz, res->new_sz);
+				 prog_name, relo_idx, insn_idx, res->orig_sz, res->new_sz);
 		}
 		break;
 	case BPF_LD: {
@@ -6080,14 +6081,14 @@ static int bpf_core_patch_insn(struct bpf_program *prog,
 		    insn[1].code != 0 || insn[1].dst_reg != 0 ||
 		    insn[1].src_reg != 0 || insn[1].off != 0) {
 			pr_warn("prog '%s': relo #%d: insn #%d (LDIMM64) has unexpected form\n",
-				prog->name, relo_idx, insn_idx);
+				prog_name, relo_idx, insn_idx);
 			return -EINVAL;
 		}
 
 		imm = insn[0].imm + ((__u64)insn[1].imm << 32);
 		if (res->validate && imm != orig_val) {
 			pr_warn("prog '%s': relo #%d: unexpected insn #%d (LDIMM64) value: got %llu, exp %u -> %u\n",
-				prog->name, relo_idx,
+				prog_name, relo_idx,
 				insn_idx, (unsigned long long)imm,
 				orig_val, new_val);
 			return -EINVAL;
@@ -6096,13 +6097,13 @@ static int bpf_core_patch_insn(struct bpf_program *prog,
 		insn[0].imm = new_val;
 		insn[1].imm = 0; /* currently only 32-bit values are supported */
 		pr_debug("prog '%s': relo #%d: patched insn #%d (LDIMM64) imm64 %llu -> %u\n",
-			 prog->name, relo_idx, insn_idx,
+			 prog_name, relo_idx, insn_idx,
 			 (unsigned long long)imm, new_val);
 		break;
 	}
 	default:
 		pr_warn("prog '%s': relo #%d: trying to relocate unrecognized insn #%d, code:0x%x, src:0x%x, dst:0x%x, off:0x%x, imm:0x%x\n",
-			prog->name, relo_idx, insn_idx, insn->code,
+			prog_name, relo_idx, insn_idx, insn->code,
 			insn->src_reg, insn->dst_reg, insn->off, insn->imm);
 		return -EINVAL;
 	}
@@ -6238,6 +6239,7 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
 	const struct btf_type *local_type;
 	const char *local_name;
 	struct core_cand_list *cands = NULL;
+	const char *prog_name = prog->name;
 	__u32 local_id;
 	const char *spec_str;
 	int i, j, err;
@@ -6264,13 +6266,13 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
 	err = bpf_core_parse_spec(local_btf, local_id, spec_str, relo->kind, &local_spec);
 	if (err) {
 		pr_warn("prog '%s': relo #%d: parsing [%d] %s %s + %s failed: %d\n",
-			prog->name, relo_idx, local_id, btf_kind_str(local_type),
+			prog_name, relo_idx, local_id, btf_kind_str(local_type),
 			str_is_empty(local_name) ? "<anon>" : local_name,
 			spec_str, err);
 		return -EINVAL;
 	}
 
-	pr_debug("prog '%s': relo #%d: kind <%s> (%d), spec is ", prog->name,
+	pr_debug("prog '%s': relo #%d: kind <%s> (%d), spec is ", prog_name,
 		 relo_idx, core_relo_kind_str(relo->kind), relo->kind);
 	bpf_core_dump_spec(LIBBPF_DEBUG, &local_spec);
 	libbpf_print(LIBBPF_DEBUG, "\n");
@@ -6287,7 +6289,7 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
 	/* libbpf doesn't support candidate search for anonymous types */
 	if (str_is_empty(spec_str)) {
 		pr_warn("prog '%s': relo #%d: <%s> (%d) relocation doesn't support anonymous types\n",
-			prog->name, relo_idx, core_relo_kind_str(relo->kind), relo->kind);
+			prog_name, relo_idx, core_relo_kind_str(relo->kind), relo->kind);
 		return -EOPNOTSUPP;
 	}
 
@@ -6295,7 +6297,7 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
 		cands = bpf_core_find_cands(prog->obj, local_btf, local_id);
 		if (IS_ERR(cands)) {
 			pr_warn("prog '%s': relo #%d: target candidate search failed for [%d] %s %s: %ld\n",
-				prog->name, relo_idx, local_id, btf_kind_str(local_type),
+				prog_name, relo_idx, local_id, btf_kind_str(local_type),
 				local_name, PTR_ERR(cands));
 			return PTR_ERR(cands);
 		}
@@ -6311,13 +6313,13 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
 					  cands->cands[i].id, &cand_spec);
 		if (err < 0) {
 			pr_warn("prog '%s': relo #%d: error matching candidate #%d ",
-				prog->name, relo_idx, i);
+				prog_name, relo_idx, i);
 			bpf_core_dump_spec(LIBBPF_WARN, &cand_spec);
 			libbpf_print(LIBBPF_WARN, ": %d\n", err);
 			return err;
 		}
 
-		pr_debug("prog '%s': relo #%d: %s candidate #%d ", prog->name,
+		pr_debug("prog '%s': relo #%d: %s candidate #%d ", prog_name,
 			 relo_idx, err == 0 ? "non-matching" : "matching", i);
 		bpf_core_dump_spec(LIBBPF_DEBUG, &cand_spec);
 		libbpf_print(LIBBPF_DEBUG, "\n");
@@ -6325,7 +6327,7 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
 		if (err == 0)
 			continue;
 
-		err = bpf_core_calc_relo(prog, relo, relo_idx, &local_spec, &cand_spec, &cand_res);
+		err = bpf_core_calc_relo(prog_name, relo, relo_idx, &local_spec, &cand_spec, &cand_res);
 		if (err)
 			return err;
 
@@ -6337,7 +6339,7 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
 			 * should all resolve to the same bit offset
 			 */
 			pr_warn("prog '%s': relo #%d: field offset ambiguity: %u != %u\n",
-				prog->name, relo_idx, cand_spec.bit_offset,
+				prog_name, relo_idx, cand_spec.bit_offset,
 				targ_spec.bit_offset);
 			return -EINVAL;
 		} else if (cand_res.poison != targ_res.poison || cand_res.new_val != targ_res.new_val) {
@@ -6346,7 +6348,7 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
 			 * proceed due to ambiguity
 			 */
 			pr_warn("prog '%s': relo #%d: relocation decision ambiguity: %s %u != %s %u\n",
-				prog->name, relo_idx,
+				prog_name, relo_idx,
 				cand_res.poison ? "failure" : "success", cand_res.new_val,
 				targ_res.poison ? "failure" : "success", targ_res.new_val);
 			return -EINVAL;
@@ -6379,10 +6381,10 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
 	 */
 	if (j == 0) {
 		pr_debug("prog '%s': relo #%d: no matching targets found\n",
-			 prog->name, relo_idx);
+			 prog_name, relo_idx);
 
 		/* calculate single target relo result explicitly */
-		err = bpf_core_calc_relo(prog, relo, relo_idx, &local_spec, NULL, &targ_res);
+		err = bpf_core_calc_relo(prog_name, relo, relo_idx, &local_spec, NULL, &targ_res);
 		if (err)
 			return err;
 	}
@@ -6392,7 +6394,7 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
 	err = bpf_core_patch_insn(prog, relo, relo_idx, &targ_res);
 	if (err) {
 		pr_warn("prog '%s': relo #%d: failed to patch insn #%zu: %d\n",
-			prog->name, relo_idx, relo->insn_off / BPF_INSN_SZ, err);
+			prog_name, relo_idx, relo->insn_off / BPF_INSN_SZ, err);
 		return -EINVAL;
 	}
 
-- 
2.30.2


^ permalink raw reply	[flat|nested] 10+ messages in thread

* [PATCH bpf-next 2/4] libbpf: Split bpf_core_apply_relo() into bpf_program indepdent helper.
  2021-07-21  0:08 [PATCH bpf-next 0/4] libbpf: Move CO-RE logic into separate file Alexei Starovoitov
  2021-07-21  0:08 ` [PATCH bpf-next 1/4] libbpf: Cleanup the layering between CORE and bpf_program Alexei Starovoitov
@ 2021-07-21  0:08 ` Alexei Starovoitov
  2021-07-21  0:08 ` [PATCH bpf-next 3/4] libbpf: Move CO-RE types into relo_core.h Alexei Starovoitov
                   ` (3 subsequent siblings)
  5 siblings, 0 replies; 10+ messages in thread
From: Alexei Starovoitov @ 2021-07-21  0:08 UTC (permalink / raw)
  To: davem; +Cc: daniel, andrii, netdev, bpf, kernel-team

From: Alexei Starovoitov <ast@kernel.org>

bpf_core_apply_relo() doesn't need to know bpf_program internals
and hashmap details.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 tools/lib/bpf/libbpf.c | 117 +++++++++++++++++++++++++----------------
 1 file changed, 71 insertions(+), 46 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 57af20574f06..4f71b4218f14 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -5972,26 +5972,13 @@ static int insn_bytes_to_bpf_size(__u32 sz)
  * 5. *(T *)(rX + <off>) = rY, where T is one of {u8, u16, u32, u64};
  * 6. *(T *)(rX + <off>) = <imm>, where T is one of {u8, u16, u32, u64}.
  */
-static int bpf_core_patch_insn(struct bpf_program *prog,
-			       const struct bpf_core_relo *relo,
-			       int relo_idx,
-			       const struct bpf_core_relo_res *res)
+static int bpf_core_patch_insn(const char *prog_name, struct bpf_insn *insn,
+			       int insn_idx, const struct bpf_core_relo *relo,
+			       int relo_idx, const struct bpf_core_relo_res *res)
 {
-	const char *prog_name = prog->name;
 	__u32 orig_val, new_val;
-	struct bpf_insn *insn;
-	int insn_idx;
 	__u8 class;
 
-	if (relo->insn_off % BPF_INSN_SZ)
-		return -EINVAL;
-	insn_idx = relo->insn_off / BPF_INSN_SZ;
-	/* adjust insn_idx from section frame of reference to the local
-	 * program's frame of reference; (sub-)program code is not yet
-	 * relocated, so it's enough to just subtract in-section offset
-	 */
-	insn_idx = insn_idx - prog->sec_insn_off;
-	insn = &prog->insns[insn_idx];
 	class = BPF_CLASS(insn->code);
 
 	if (res->poison) {
@@ -6077,7 +6064,6 @@ static int bpf_core_patch_insn(struct bpf_program *prog,
 
 		if (!is_ldimm64_insn(insn) ||
 		    insn[0].src_reg != 0 || insn[0].off != 0 ||
-		    insn_idx + 1 >= prog->insns_cnt ||
 		    insn[1].code != 0 || insn[1].dst_reg != 0 ||
 		    insn[1].src_reg != 0 || insn[1].off != 0) {
 			pr_warn("prog '%s': relo #%d: insn #%d (LDIMM64) has unexpected form\n",
@@ -6227,19 +6213,17 @@ static void *u32_as_hash_key(__u32 x)
  *    between multiple relocations for the same type ID and is updated as some
  *    of the candidates are pruned due to structural incompatibility.
  */
-static int bpf_core_apply_relo(struct bpf_program *prog,
-			       const struct bpf_core_relo *relo,
-			       int relo_idx,
-			       const struct btf *local_btf,
-			       struct hashmap *cand_cache)
+static int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
+				    int insn_idx,
+				    const struct bpf_core_relo *relo,
+				    int relo_idx,
+				    const struct btf *local_btf,
+				    struct core_cand_list *cands)
 {
 	struct bpf_core_spec local_spec, cand_spec, targ_spec = {};
-	const void *type_key = u32_as_hash_key(relo->type_id);
 	struct bpf_core_relo_res cand_res, targ_res;
 	const struct btf_type *local_type;
 	const char *local_name;
-	struct core_cand_list *cands = NULL;
-	const char *prog_name = prog->name;
 	__u32 local_id;
 	const char *spec_str;
 	int i, j, err;
@@ -6257,12 +6241,6 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
 	if (str_is_empty(spec_str))
 		return -EINVAL;
 
-	if (prog->obj->gen_loader) {
-		pr_warn("// TODO core_relo: prog %td insn[%d] %s %s kind %d\n",
-			prog - prog->obj->programs, relo->insn_off / 8,
-			local_name, spec_str, relo->kind);
-		return -ENOTSUP;
-	}
 	err = bpf_core_parse_spec(local_btf, local_id, spec_str, relo->kind, &local_spec);
 	if (err) {
 		pr_warn("prog '%s': relo #%d: parsing [%d] %s %s + %s failed: %d\n",
@@ -6293,20 +6271,6 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
 		return -EOPNOTSUPP;
 	}
 
-	if (!hashmap__find(cand_cache, type_key, (void **)&cands)) {
-		cands = bpf_core_find_cands(prog->obj, local_btf, local_id);
-		if (IS_ERR(cands)) {
-			pr_warn("prog '%s': relo #%d: target candidate search failed for [%d] %s %s: %ld\n",
-				prog_name, relo_idx, local_id, btf_kind_str(local_type),
-				local_name, PTR_ERR(cands));
-			return PTR_ERR(cands);
-		}
-		err = hashmap__set(cand_cache, type_key, cands, NULL, NULL);
-		if (err) {
-			bpf_core_free_cands(cands);
-			return err;
-		}
-	}
 
 	for (i = 0, j = 0; i < cands->len; i++) {
 		err = bpf_core_spec_match(&local_spec, cands->cands[i].btf,
@@ -6391,7 +6355,7 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
 
 patch_insn:
 	/* bpf_core_patch_insn() should know how to handle missing targ_spec */
-	err = bpf_core_patch_insn(prog, relo, relo_idx, &targ_res);
+	err = bpf_core_patch_insn(prog_name, insn, insn_idx, relo, relo_idx, &targ_res);
 	if (err) {
 		pr_warn("prog '%s': relo #%d: failed to patch insn #%zu: %d\n",
 			prog_name, relo_idx, relo->insn_off / BPF_INSN_SZ, err);
@@ -6401,6 +6365,67 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
 	return 0;
 }
 
+static int bpf_core_apply_relo(struct bpf_program *prog,
+			       const struct bpf_core_relo *relo,
+			       int relo_idx,
+			       const struct btf *local_btf,
+			       struct hashmap *cand_cache)
+{
+	const void *type_key = u32_as_hash_key(relo->type_id);
+	struct core_cand_list *cands = NULL;
+	const char *prog_name = prog->name;
+	const struct btf_type *local_type;
+	const char *local_name;
+	__u32 local_id = relo->type_id;
+	struct bpf_insn *insn;
+	int insn_idx, err;
+
+	if (relo->insn_off % BPF_INSN_SZ)
+		return -EINVAL;
+	insn_idx = relo->insn_off / BPF_INSN_SZ;
+	/* adjust insn_idx from section frame of reference to the local
+	 * program's frame of reference; (sub-)program code is not yet
+	 * relocated, so it's enough to just subtract in-section offset
+	 */
+	insn_idx = insn_idx - prog->sec_insn_off;
+	if (insn_idx > prog->insns_cnt)
+		return -EINVAL;
+	insn = &prog->insns[insn_idx];
+
+	local_type = btf__type_by_id(local_btf, local_id);
+	if (!local_type)
+		return -EINVAL;
+
+	local_name = btf__name_by_offset(local_btf, local_type->name_off);
+	if (!local_name)
+		return -EINVAL;
+
+	if (prog->obj->gen_loader) {
+		pr_warn("// TODO core_relo: prog %td insn[%d] %s kind %d\n",
+			prog - prog->obj->programs, relo->insn_off / 8,
+			local_name, relo->kind);
+		return -ENOTSUP;
+	}
+
+	if (relo->kind != BPF_TYPE_ID_LOCAL &&
+	    !hashmap__find(cand_cache, type_key, (void **)&cands)) {
+		cands = bpf_core_find_cands(prog->obj, local_btf, local_id);
+		if (IS_ERR(cands)) {
+			pr_warn("prog '%s': relo #%d: target candidate search failed for [%d] %s %s: %ld\n",
+				prog_name, relo_idx, local_id, btf_kind_str(local_type),
+				local_name, PTR_ERR(cands));
+			return PTR_ERR(cands);
+		}
+		err = hashmap__set(cand_cache, type_key, cands, NULL, NULL);
+		if (err) {
+			bpf_core_free_cands(cands);
+			return err;
+		}
+	}
+
+	return bpf_core_apply_relo_insn(prog_name, insn, insn_idx, relo, relo_idx, local_btf, cands);
+}
+
 static int
 bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path)
 {
-- 
2.30.2


^ permalink raw reply	[flat|nested] 10+ messages in thread

* [PATCH bpf-next 3/4] libbpf: Move CO-RE types into relo_core.h.
  2021-07-21  0:08 [PATCH bpf-next 0/4] libbpf: Move CO-RE logic into separate file Alexei Starovoitov
  2021-07-21  0:08 ` [PATCH bpf-next 1/4] libbpf: Cleanup the layering between CORE and bpf_program Alexei Starovoitov
  2021-07-21  0:08 ` [PATCH bpf-next 2/4] libbpf: Split bpf_core_apply_relo() into bpf_program indepdent helper Alexei Starovoitov
@ 2021-07-21  0:08 ` Alexei Starovoitov
  2021-07-21  0:08 ` [PATCH bpf-next 4/4] libbpf: Split CO-RE logic into relo_core.c Alexei Starovoitov
                   ` (2 subsequent siblings)
  5 siblings, 0 replies; 10+ messages in thread
From: Alexei Starovoitov @ 2021-07-21  0:08 UTC (permalink / raw)
  To: davem; +Cc: daniel, andrii, netdev, bpf, kernel-team

From: Alexei Starovoitov <ast@kernel.org>

In order to make a clean split of CO-RE logic move its types
into independent header file.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 tools/lib/bpf/libbpf.c          | 32 ++++--------
 tools/lib/bpf/libbpf_internal.h | 71 +------------------------
 tools/lib/bpf/relo_core.h       | 92 +++++++++++++++++++++++++++++++++
 3 files changed, 102 insertions(+), 93 deletions(-)
 create mode 100644 tools/lib/bpf/relo_core.h

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 4f71b4218f14..7ae5992a79e2 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -5022,34 +5022,20 @@ static size_t bpf_core_essential_name_len(const char *name)
 	return n;
 }
 
-struct core_cand
-{
-	const struct btf *btf;
-	const struct btf_type *t;
-	const char *name;
-	__u32 id;
-};
-
-/* dynamically sized list of type IDs and its associated struct btf */
-struct core_cand_list {
-	struct core_cand *cands;
-	int len;
-};
-
-static void bpf_core_free_cands(struct core_cand_list *cands)
+static void bpf_core_free_cands(struct bpf_core_cand_list *cands)
 {
 	free(cands->cands);
 	free(cands);
 }
 
-static int bpf_core_add_cands(struct core_cand *local_cand,
+static int bpf_core_add_cands(struct bpf_core_cand *local_cand,
 			      size_t local_essent_len,
 			      const struct btf *targ_btf,
 			      const char *targ_btf_name,
 			      int targ_start_id,
-			      struct core_cand_list *cands)
+			      struct bpf_core_cand_list *cands)
 {
-	struct core_cand *new_cands, *cand;
+	struct bpf_core_cand *new_cands, *cand;
 	const struct btf_type *t;
 	const char *targ_name;
 	size_t targ_essent_len;
@@ -5185,11 +5171,11 @@ static int load_module_btfs(struct bpf_object *obj)
 	return 0;
 }
 
-static struct core_cand_list *
+static struct bpf_core_cand_list *
 bpf_core_find_cands(struct bpf_object *obj, const struct btf *local_btf, __u32 local_type_id)
 {
-	struct core_cand local_cand = {};
-	struct core_cand_list *cands;
+	struct bpf_core_cand local_cand = {};
+	struct bpf_core_cand_list *cands;
 	const struct btf *main_btf;
 	size_t local_essent_len;
 	int err, i;
@@ -6218,7 +6204,7 @@ static int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn
 				    const struct bpf_core_relo *relo,
 				    int relo_idx,
 				    const struct btf *local_btf,
-				    struct core_cand_list *cands)
+				    struct bpf_core_cand_list *cands)
 {
 	struct bpf_core_spec local_spec, cand_spec, targ_spec = {};
 	struct bpf_core_relo_res cand_res, targ_res;
@@ -6372,7 +6358,7 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
 			       struct hashmap *cand_cache)
 {
 	const void *type_key = u32_as_hash_key(relo->type_id);
-	struct core_cand_list *cands = NULL;
+	struct bpf_core_cand_list *cands = NULL;
 	const char *prog_name = prog->name;
 	const struct btf_type *local_type;
 	const char *local_name;
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 016ca7cb4f8a..3178d5685dce 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -14,6 +14,7 @@
 #include <errno.h>
 #include <linux/err.h>
 #include "libbpf_legacy.h"
+#include "relo_core.h"
 
 /* make sure libbpf doesn't use kernel-only integer typedefs */
 #pragma GCC poison u8 u16 u32 u64 s8 s16 s32 s64
@@ -366,76 +367,6 @@ struct bpf_line_info_min {
 	__u32	line_col;
 };
 
-/* bpf_core_relo_kind encodes which aspect of captured field/type/enum value
- * has to be adjusted by relocations.
- */
-enum bpf_core_relo_kind {
-	BPF_FIELD_BYTE_OFFSET = 0,	/* field byte offset */
-	BPF_FIELD_BYTE_SIZE = 1,	/* field size in bytes */
-	BPF_FIELD_EXISTS = 2,		/* field existence in target kernel */
-	BPF_FIELD_SIGNED = 3,		/* field signedness (0 - unsigned, 1 - signed) */
-	BPF_FIELD_LSHIFT_U64 = 4,	/* bitfield-specific left bitshift */
-	BPF_FIELD_RSHIFT_U64 = 5,	/* bitfield-specific right bitshift */
-	BPF_TYPE_ID_LOCAL = 6,		/* type ID in local BPF object */
-	BPF_TYPE_ID_TARGET = 7,		/* type ID in target kernel */
-	BPF_TYPE_EXISTS = 8,		/* type existence in target kernel */
-	BPF_TYPE_SIZE = 9,		/* type size in bytes */
-	BPF_ENUMVAL_EXISTS = 10,	/* enum value existence in target kernel */
-	BPF_ENUMVAL_VALUE = 11,		/* enum value integer value */
-};
-
-/* The minimum bpf_core_relo checked by the loader
- *
- * CO-RE relocation captures the following data:
- * - insn_off - instruction offset (in bytes) within a BPF program that needs
- *   its insn->imm field to be relocated with actual field info;
- * - type_id - BTF type ID of the "root" (containing) entity of a relocatable
- *   type or field;
- * - access_str_off - offset into corresponding .BTF string section. String
- *   interpretation depends on specific relocation kind:
- *     - for field-based relocations, string encodes an accessed field using
- *     a sequence of field and array indices, separated by colon (:). It's
- *     conceptually very close to LLVM's getelementptr ([0]) instruction's
- *     arguments for identifying offset to a field.
- *     - for type-based relocations, strings is expected to be just "0";
- *     - for enum value-based relocations, string contains an index of enum
- *     value within its enum type;
- *
- * Example to provide a better feel.
- *
- *   struct sample {
- *       int a;
- *       struct {
- *           int b[10];
- *       };
- *   };
- *
- *   struct sample *s = ...;
- *   int x = &s->a;     // encoded as "0:0" (a is field #0)
- *   int y = &s->b[5];  // encoded as "0:1:0:5" (anon struct is field #1, 
- *                      // b is field #0 inside anon struct, accessing elem #5)
- *   int z = &s[10]->b; // encoded as "10:1" (ptr is used as an array)
- *
- * type_id for all relocs in this example  will capture BTF type id of
- * `struct sample`.
- *
- * Such relocation is emitted when using __builtin_preserve_access_index()
- * Clang built-in, passing expression that captures field address, e.g.:
- *
- * bpf_probe_read(&dst, sizeof(dst),
- *		  __builtin_preserve_access_index(&src->a.b.c));
- *
- * In this case Clang will emit field relocation recording necessary data to
- * be able to find offset of embedded `a.b.c` field within `src` struct.
- *
- *   [0] https://llvm.org/docs/LangRef.html#getelementptr-instruction
- */
-struct bpf_core_relo {
-	__u32   insn_off;
-	__u32   type_id;
-	__u32   access_str_off;
-	enum bpf_core_relo_kind kind;
-};
 
 typedef int (*type_id_visit_fn)(__u32 *type_id, void *ctx);
 typedef int (*str_off_visit_fn)(__u32 *str_off, void *ctx);
diff --git a/tools/lib/bpf/relo_core.h b/tools/lib/bpf/relo_core.h
new file mode 100644
index 000000000000..62633e73c297
--- /dev/null
+++ b/tools/lib/bpf/relo_core.h
@@ -0,0 +1,92 @@
+/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
+/* Copyright (c) 2021 Facebook */
+
+#ifndef __RELO_CORE_H
+#define __RELO_CORE_H
+
+/* bpf_core_relo_kind encodes which aspect of captured field/type/enum value
+ * has to be adjusted by relocations.
+ */
+enum bpf_core_relo_kind {
+	BPF_FIELD_BYTE_OFFSET = 0,	/* field byte offset */
+	BPF_FIELD_BYTE_SIZE = 1,	/* field size in bytes */
+	BPF_FIELD_EXISTS = 2,		/* field existence in target kernel */
+	BPF_FIELD_SIGNED = 3,		/* field signedness (0 - unsigned, 1 - signed) */
+	BPF_FIELD_LSHIFT_U64 = 4,	/* bitfield-specific left bitshift */
+	BPF_FIELD_RSHIFT_U64 = 5,	/* bitfield-specific right bitshift */
+	BPF_TYPE_ID_LOCAL = 6,		/* type ID in local BPF object */
+	BPF_TYPE_ID_TARGET = 7,		/* type ID in target kernel */
+	BPF_TYPE_EXISTS = 8,		/* type existence in target kernel */
+	BPF_TYPE_SIZE = 9,		/* type size in bytes */
+	BPF_ENUMVAL_EXISTS = 10,	/* enum value existence in target kernel */
+	BPF_ENUMVAL_VALUE = 11,		/* enum value integer value */
+};
+
+/* The minimum bpf_core_relo checked by the loader
+ *
+ * CO-RE relocation captures the following data:
+ * - insn_off - instruction offset (in bytes) within a BPF program that needs
+ *   its insn->imm field to be relocated with actual field info;
+ * - type_id - BTF type ID of the "root" (containing) entity of a relocatable
+ *   type or field;
+ * - access_str_off - offset into corresponding .BTF string section. String
+ *   interpretation depends on specific relocation kind:
+ *     - for field-based relocations, string encodes an accessed field using
+ *     a sequence of field and array indices, separated by colon (:). It's
+ *     conceptually very close to LLVM's getelementptr ([0]) instruction's
+ *     arguments for identifying offset to a field.
+ *     - for type-based relocations, strings is expected to be just "0";
+ *     - for enum value-based relocations, string contains an index of enum
+ *     value within its enum type;
+ *
+ * Example to provide a better feel.
+ *
+ *   struct sample {
+ *       int a;
+ *       struct {
+ *           int b[10];
+ *       };
+ *   };
+ *
+ *   struct sample *s = ...;
+ *   int x = &s->a;     // encoded as "0:0" (a is field #0)
+ *   int y = &s->b[5];  // encoded as "0:1:0:5" (anon struct is field #1, 
+ *                      // b is field #0 inside anon struct, accessing elem #5)
+ *   int z = &s[10]->b; // encoded as "10:1" (ptr is used as an array)
+ *
+ * type_id for all relocs in this example  will capture BTF type id of
+ * `struct sample`.
+ *
+ * Such relocation is emitted when using __builtin_preserve_access_index()
+ * Clang built-in, passing expression that captures field address, e.g.:
+ *
+ * bpf_probe_read(&dst, sizeof(dst),
+ *		  __builtin_preserve_access_index(&src->a.b.c));
+ *
+ * In this case Clang will emit field relocation recording necessary data to
+ * be able to find offset of embedded `a.b.c` field within `src` struct.
+ *
+ *   [0] https://llvm.org/docs/LangRef.html#getelementptr-instruction
+ */
+struct bpf_core_relo {
+	__u32   insn_off;
+	__u32   type_id;
+	__u32   access_str_off;
+	enum bpf_core_relo_kind kind;
+};
+
+struct bpf_core_cand
+{
+	const struct btf *btf;
+	const struct btf_type *t;
+	const char *name;
+	__u32 id;
+};
+
+/* dynamically sized list of type IDs and its associated struct btf */
+struct bpf_core_cand_list {
+	struct bpf_core_cand *cands;
+	int len;
+};
+
+#endif
-- 
2.30.2


^ permalink raw reply	[flat|nested] 10+ messages in thread

* [PATCH bpf-next 4/4] libbpf: Split CO-RE logic into relo_core.c.
  2021-07-21  0:08 [PATCH bpf-next 0/4] libbpf: Move CO-RE logic into separate file Alexei Starovoitov
                   ` (2 preceding siblings ...)
  2021-07-21  0:08 ` [PATCH bpf-next 3/4] libbpf: Move CO-RE types into relo_core.h Alexei Starovoitov
@ 2021-07-21  0:08 ` Alexei Starovoitov
  2021-07-22 16:02 ` [PATCH bpf-next 0/4] libbpf: Move CO-RE logic into separate file Toke Høiland-Jørgensen
  2021-07-26 19:37 ` Andrii Nakryiko
  5 siblings, 0 replies; 10+ messages in thread
From: Alexei Starovoitov @ 2021-07-21  0:08 UTC (permalink / raw)
  To: davem; +Cc: daniel, andrii, netdev, bpf, kernel-team

From: Alexei Starovoitov <ast@kernel.org>

Move CO-RE logic into separate file.
The internal interface between libbpf and CO-RE is through
bpf_core_apply_relo_insn() function and few structs defined in relo_core.h.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 tools/lib/bpf/Build             |    2 +-
 tools/lib/bpf/libbpf.c          | 1297 +-----------------------------
 tools/lib/bpf/libbpf_internal.h |   10 +
 tools/lib/bpf/relo_core.c       | 1326 +++++++++++++++++++++++++++++++
 tools/lib/bpf/relo_core.h       |   10 +
 5 files changed, 1350 insertions(+), 1295 deletions(-)
 create mode 100644 tools/lib/bpf/relo_core.c

diff --git a/tools/lib/bpf/Build b/tools/lib/bpf/Build
index 430f6874fa41..94f0a146bb7b 100644
--- a/tools/lib/bpf/Build
+++ b/tools/lib/bpf/Build
@@ -1,3 +1,3 @@
 libbpf-y := libbpf.o bpf.o nlattr.o btf.o libbpf_errno.o str_error.o \
 	    netlink.o bpf_prog_linfo.o libbpf_probes.o xsk.o hashmap.o \
-	    btf_dump.o ringbuf.o strset.o linker.o gen_loader.o
+	    btf_dump.o ringbuf.o strset.o linker.o gen_loader.o relo_core.o
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 7ae5992a79e2..c8c7419b3efd 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -595,11 +595,6 @@ static bool insn_is_subprog_call(const struct bpf_insn *insn)
 	       insn->off == 0;
 }
 
-static bool is_ldimm64_insn(struct bpf_insn *insn)
-{
-	return insn->code == (BPF_LD | BPF_IMM | BPF_DW);
-}
-
 static bool is_call_insn(const struct bpf_insn *insn)
 {
 	return insn->code == (BPF_JMP | BPF_CALL);
@@ -4725,279 +4720,6 @@ bpf_object__create_maps(struct bpf_object *obj)
 	return err;
 }
 
-#define BPF_CORE_SPEC_MAX_LEN 64
-
-/* represents BPF CO-RE field or array element accessor */
-struct bpf_core_accessor {
-	__u32 type_id;		/* struct/union type or array element type */
-	__u32 idx;		/* field index or array index */
-	const char *name;	/* field name or NULL for array accessor */
-};
-
-struct bpf_core_spec {
-	const struct btf *btf;
-	/* high-level spec: named fields and array indices only */
-	struct bpf_core_accessor spec[BPF_CORE_SPEC_MAX_LEN];
-	/* original unresolved (no skip_mods_or_typedefs) root type ID */
-	__u32 root_type_id;
-	/* CO-RE relocation kind */
-	enum bpf_core_relo_kind relo_kind;
-	/* high-level spec length */
-	int len;
-	/* raw, low-level spec: 1-to-1 with accessor spec string */
-	int raw_spec[BPF_CORE_SPEC_MAX_LEN];
-	/* raw spec length */
-	int raw_len;
-	/* field bit offset represented by spec */
-	__u32 bit_offset;
-};
-
-static bool str_is_empty(const char *s)
-{
-	return !s || !s[0];
-}
-
-static bool is_flex_arr(const struct btf *btf,
-			const struct bpf_core_accessor *acc,
-			const struct btf_array *arr)
-{
-	const struct btf_type *t;
-
-	/* not a flexible array, if not inside a struct or has non-zero size */
-	if (!acc->name || arr->nelems > 0)
-		return false;
-
-	/* has to be the last member of enclosing struct */
-	t = btf__type_by_id(btf, acc->type_id);
-	return acc->idx == btf_vlen(t) - 1;
-}
-
-static const char *core_relo_kind_str(enum bpf_core_relo_kind kind)
-{
-	switch (kind) {
-	case BPF_FIELD_BYTE_OFFSET: return "byte_off";
-	case BPF_FIELD_BYTE_SIZE: return "byte_sz";
-	case BPF_FIELD_EXISTS: return "field_exists";
-	case BPF_FIELD_SIGNED: return "signed";
-	case BPF_FIELD_LSHIFT_U64: return "lshift_u64";
-	case BPF_FIELD_RSHIFT_U64: return "rshift_u64";
-	case BPF_TYPE_ID_LOCAL: return "local_type_id";
-	case BPF_TYPE_ID_TARGET: return "target_type_id";
-	case BPF_TYPE_EXISTS: return "type_exists";
-	case BPF_TYPE_SIZE: return "type_size";
-	case BPF_ENUMVAL_EXISTS: return "enumval_exists";
-	case BPF_ENUMVAL_VALUE: return "enumval_value";
-	default: return "unknown";
-	}
-}
-
-static bool core_relo_is_field_based(enum bpf_core_relo_kind kind)
-{
-	switch (kind) {
-	case BPF_FIELD_BYTE_OFFSET:
-	case BPF_FIELD_BYTE_SIZE:
-	case BPF_FIELD_EXISTS:
-	case BPF_FIELD_SIGNED:
-	case BPF_FIELD_LSHIFT_U64:
-	case BPF_FIELD_RSHIFT_U64:
-		return true;
-	default:
-		return false;
-	}
-}
-
-static bool core_relo_is_type_based(enum bpf_core_relo_kind kind)
-{
-	switch (kind) {
-	case BPF_TYPE_ID_LOCAL:
-	case BPF_TYPE_ID_TARGET:
-	case BPF_TYPE_EXISTS:
-	case BPF_TYPE_SIZE:
-		return true;
-	default:
-		return false;
-	}
-}
-
-static bool core_relo_is_enumval_based(enum bpf_core_relo_kind kind)
-{
-	switch (kind) {
-	case BPF_ENUMVAL_EXISTS:
-	case BPF_ENUMVAL_VALUE:
-		return true;
-	default:
-		return false;
-	}
-}
-
-/*
- * Turn bpf_core_relo into a low- and high-level spec representation,
- * validating correctness along the way, as well as calculating resulting
- * field bit offset, specified by accessor string. Low-level spec captures
- * every single level of nestedness, including traversing anonymous
- * struct/union members. High-level one only captures semantically meaningful
- * "turning points": named fields and array indicies.
- * E.g., for this case:
- *
- *   struct sample {
- *       int __unimportant;
- *       struct {
- *           int __1;
- *           int __2;
- *           int a[7];
- *       };
- *   };
- *
- *   struct sample *s = ...;
- *
- *   int x = &s->a[3]; // access string = '0:1:2:3'
- *
- * Low-level spec has 1:1 mapping with each element of access string (it's
- * just a parsed access string representation): [0, 1, 2, 3].
- *
- * High-level spec will capture only 3 points:
- *   - intial zero-index access by pointer (&s->... is the same as &s[0]...);
- *   - field 'a' access (corresponds to '2' in low-level spec);
- *   - array element #3 access (corresponds to '3' in low-level spec).
- *
- * Type-based relocations (TYPE_EXISTS/TYPE_SIZE,
- * TYPE_ID_LOCAL/TYPE_ID_TARGET) don't capture any field information. Their
- * spec and raw_spec are kept empty.
- *
- * Enum value-based relocations (ENUMVAL_EXISTS/ENUMVAL_VALUE) use access
- * string to specify enumerator's value index that need to be relocated.
- */
-static int bpf_core_parse_spec(const struct btf *btf,
-			       __u32 type_id,
-			       const char *spec_str,
-			       enum bpf_core_relo_kind relo_kind,
-			       struct bpf_core_spec *spec)
-{
-	int access_idx, parsed_len, i;
-	struct bpf_core_accessor *acc;
-	const struct btf_type *t;
-	const char *name;
-	__u32 id;
-	__s64 sz;
-
-	if (str_is_empty(spec_str) || *spec_str == ':')
-		return -EINVAL;
-
-	memset(spec, 0, sizeof(*spec));
-	spec->btf = btf;
-	spec->root_type_id = type_id;
-	spec->relo_kind = relo_kind;
-
-	/* type-based relocations don't have a field access string */
-	if (core_relo_is_type_based(relo_kind)) {
-		if (strcmp(spec_str, "0"))
-			return -EINVAL;
-		return 0;
-	}
-
-	/* parse spec_str="0:1:2:3:4" into array raw_spec=[0, 1, 2, 3, 4] */
-	while (*spec_str) {
-		if (*spec_str == ':')
-			++spec_str;
-		if (sscanf(spec_str, "%d%n", &access_idx, &parsed_len) != 1)
-			return -EINVAL;
-		if (spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
-			return -E2BIG;
-		spec_str += parsed_len;
-		spec->raw_spec[spec->raw_len++] = access_idx;
-	}
-
-	if (spec->raw_len == 0)
-		return -EINVAL;
-
-	t = skip_mods_and_typedefs(btf, type_id, &id);
-	if (!t)
-		return -EINVAL;
-
-	access_idx = spec->raw_spec[0];
-	acc = &spec->spec[0];
-	acc->type_id = id;
-	acc->idx = access_idx;
-	spec->len++;
-
-	if (core_relo_is_enumval_based(relo_kind)) {
-		if (!btf_is_enum(t) || spec->raw_len > 1 || access_idx >= btf_vlen(t))
-			return -EINVAL;
-
-		/* record enumerator name in a first accessor */
-		acc->name = btf__name_by_offset(btf, btf_enum(t)[access_idx].name_off);
-		return 0;
-	}
-
-	if (!core_relo_is_field_based(relo_kind))
-		return -EINVAL;
-
-	sz = btf__resolve_size(btf, id);
-	if (sz < 0)
-		return sz;
-	spec->bit_offset = access_idx * sz * 8;
-
-	for (i = 1; i < spec->raw_len; i++) {
-		t = skip_mods_and_typedefs(btf, id, &id);
-		if (!t)
-			return -EINVAL;
-
-		access_idx = spec->raw_spec[i];
-		acc = &spec->spec[spec->len];
-
-		if (btf_is_composite(t)) {
-			const struct btf_member *m;
-			__u32 bit_offset;
-
-			if (access_idx >= btf_vlen(t))
-				return -EINVAL;
-
-			bit_offset = btf_member_bit_offset(t, access_idx);
-			spec->bit_offset += bit_offset;
-
-			m = btf_members(t) + access_idx;
-			if (m->name_off) {
-				name = btf__name_by_offset(btf, m->name_off);
-				if (str_is_empty(name))
-					return -EINVAL;
-
-				acc->type_id = id;
-				acc->idx = access_idx;
-				acc->name = name;
-				spec->len++;
-			}
-
-			id = m->type;
-		} else if (btf_is_array(t)) {
-			const struct btf_array *a = btf_array(t);
-			bool flex;
-
-			t = skip_mods_and_typedefs(btf, a->type, &id);
-			if (!t)
-				return -EINVAL;
-
-			flex = is_flex_arr(btf, acc - 1, a);
-			if (!flex && access_idx >= a->nelems)
-				return -EINVAL;
-
-			spec->spec[spec->len].type_id = id;
-			spec->spec[spec->len].idx = access_idx;
-			spec->len++;
-
-			sz = btf__resolve_size(btf, id);
-			if (sz < 0)
-				return sz;
-			spec->bit_offset += access_idx * sz * 8;
-		} else {
-			pr_warn("relo for [%u] %s (at idx %d) captures type [%d] of unexpected kind %s\n",
-				type_id, spec_str, i, id, btf_kind_str(t));
-			return -EINVAL;
-		}
-	}
-
-	return 0;
-}
-
 static bool bpf_core_is_flavor_sep(const char *s)
 {
 	/* check X___Y name pattern, where X and Y are not underscores */
@@ -5010,7 +4732,7 @@ static bool bpf_core_is_flavor_sep(const char *s)
  * before last triple underscore. Struct name part after last triple
  * underscore is ignored by BPF CO-RE relocation during relocation matching.
  */
-static size_t bpf_core_essential_name_len(const char *name)
+size_t bpf_core_essential_name_len(const char *name)
 {
 	size_t n = strlen(name);
 	int i;
@@ -5229,165 +4951,6 @@ bpf_core_find_cands(struct bpf_object *obj, const struct btf *local_btf, __u32 l
 	return ERR_PTR(err);
 }
 
-/* Check two types for compatibility for the purpose of field access
- * relocation. const/volatile/restrict and typedefs are skipped to ensure we
- * are relocating semantically compatible entities:
- *   - any two STRUCTs/UNIONs are compatible and can be mixed;
- *   - any two FWDs are compatible, if their names match (modulo flavor suffix);
- *   - any two PTRs are always compatible;
- *   - for ENUMs, names should be the same (ignoring flavor suffix) or at
- *     least one of enums should be anonymous;
- *   - for ENUMs, check sizes, names are ignored;
- *   - for INT, size and signedness are ignored;
- *   - any two FLOATs are always compatible;
- *   - for ARRAY, dimensionality is ignored, element types are checked for
- *     compatibility recursively;
- *   - everything else shouldn't be ever a target of relocation.
- * These rules are not set in stone and probably will be adjusted as we get
- * more experience with using BPF CO-RE relocations.
- */
-static int bpf_core_fields_are_compat(const struct btf *local_btf,
-				      __u32 local_id,
-				      const struct btf *targ_btf,
-				      __u32 targ_id)
-{
-	const struct btf_type *local_type, *targ_type;
-
-recur:
-	local_type = skip_mods_and_typedefs(local_btf, local_id, &local_id);
-	targ_type = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id);
-	if (!local_type || !targ_type)
-		return -EINVAL;
-
-	if (btf_is_composite(local_type) && btf_is_composite(targ_type))
-		return 1;
-	if (btf_kind(local_type) != btf_kind(targ_type))
-		return 0;
-
-	switch (btf_kind(local_type)) {
-	case BTF_KIND_PTR:
-	case BTF_KIND_FLOAT:
-		return 1;
-	case BTF_KIND_FWD:
-	case BTF_KIND_ENUM: {
-		const char *local_name, *targ_name;
-		size_t local_len, targ_len;
-
-		local_name = btf__name_by_offset(local_btf,
-						 local_type->name_off);
-		targ_name = btf__name_by_offset(targ_btf, targ_type->name_off);
-		local_len = bpf_core_essential_name_len(local_name);
-		targ_len = bpf_core_essential_name_len(targ_name);
-		/* one of them is anonymous or both w/ same flavor-less names */
-		return local_len == 0 || targ_len == 0 ||
-		       (local_len == targ_len &&
-			strncmp(local_name, targ_name, local_len) == 0);
-	}
-	case BTF_KIND_INT:
-		/* just reject deprecated bitfield-like integers; all other
-		 * integers are by default compatible between each other
-		 */
-		return btf_int_offset(local_type) == 0 &&
-		       btf_int_offset(targ_type) == 0;
-	case BTF_KIND_ARRAY:
-		local_id = btf_array(local_type)->type;
-		targ_id = btf_array(targ_type)->type;
-		goto recur;
-	default:
-		pr_warn("unexpected kind %d relocated, local [%d], target [%d]\n",
-			btf_kind(local_type), local_id, targ_id);
-		return 0;
-	}
-}
-
-/*
- * Given single high-level named field accessor in local type, find
- * corresponding high-level accessor for a target type. Along the way,
- * maintain low-level spec for target as well. Also keep updating target
- * bit offset.
- *
- * Searching is performed through recursive exhaustive enumeration of all
- * fields of a struct/union. If there are any anonymous (embedded)
- * structs/unions, they are recursively searched as well. If field with
- * desired name is found, check compatibility between local and target types,
- * before returning result.
- *
- * 1 is returned, if field is found.
- * 0 is returned if no compatible field is found.
- * <0 is returned on error.
- */
-static int bpf_core_match_member(const struct btf *local_btf,
-				 const struct bpf_core_accessor *local_acc,
-				 const struct btf *targ_btf,
-				 __u32 targ_id,
-				 struct bpf_core_spec *spec,
-				 __u32 *next_targ_id)
-{
-	const struct btf_type *local_type, *targ_type;
-	const struct btf_member *local_member, *m;
-	const char *local_name, *targ_name;
-	__u32 local_id;
-	int i, n, found;
-
-	targ_type = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id);
-	if (!targ_type)
-		return -EINVAL;
-	if (!btf_is_composite(targ_type))
-		return 0;
-
-	local_id = local_acc->type_id;
-	local_type = btf__type_by_id(local_btf, local_id);
-	local_member = btf_members(local_type) + local_acc->idx;
-	local_name = btf__name_by_offset(local_btf, local_member->name_off);
-
-	n = btf_vlen(targ_type);
-	m = btf_members(targ_type);
-	for (i = 0; i < n; i++, m++) {
-		__u32 bit_offset;
-
-		bit_offset = btf_member_bit_offset(targ_type, i);
-
-		/* too deep struct/union/array nesting */
-		if (spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
-			return -E2BIG;
-
-		/* speculate this member will be the good one */
-		spec->bit_offset += bit_offset;
-		spec->raw_spec[spec->raw_len++] = i;
-
-		targ_name = btf__name_by_offset(targ_btf, m->name_off);
-		if (str_is_empty(targ_name)) {
-			/* embedded struct/union, we need to go deeper */
-			found = bpf_core_match_member(local_btf, local_acc,
-						      targ_btf, m->type,
-						      spec, next_targ_id);
-			if (found) /* either found or error */
-				return found;
-		} else if (strcmp(local_name, targ_name) == 0) {
-			/* matching named field */
-			struct bpf_core_accessor *targ_acc;
-
-			targ_acc = &spec->spec[spec->len++];
-			targ_acc->type_id = targ_id;
-			targ_acc->idx = i;
-			targ_acc->name = targ_name;
-
-			*next_targ_id = m->type;
-			found = bpf_core_fields_are_compat(local_btf,
-							   local_member->type,
-							   targ_btf, m->type);
-			if (!found)
-				spec->len--; /* pop accessor */
-			return found;
-		}
-		/* member turned out not to be what we looked for */
-		spec->bit_offset -= bit_offset;
-		spec->raw_len--;
-	}
-
-	return 0;
-}
-
 /* Check local and target types for compatibility. This check is used for
  * type-based CO-RE relocations and follow slightly different rules than
  * field-based relocations. This function assumes that root types were already
@@ -5407,8 +4970,8 @@ static int bpf_core_match_member(const struct btf *local_btf,
  * These rules are not set in stone and probably will be adjusted as we get
  * more experience with using BPF CO-RE relocations.
  */
-static int bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
-				     const struct btf *targ_btf, __u32 targ_id)
+int bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
+			      const struct btf *targ_btf, __u32 targ_id)
 {
 	const struct btf_type *local_type, *targ_type;
 	int depth = 32; /* max recursion depth */
@@ -5482,658 +5045,6 @@ static int bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id
 	}
 }
 
-/*
- * Try to match local spec to a target type and, if successful, produce full
- * target spec (high-level, low-level + bit offset).
- */
-static int bpf_core_spec_match(struct bpf_core_spec *local_spec,
-			       const struct btf *targ_btf, __u32 targ_id,
-			       struct bpf_core_spec *targ_spec)
-{
-	const struct btf_type *targ_type;
-	const struct bpf_core_accessor *local_acc;
-	struct bpf_core_accessor *targ_acc;
-	int i, sz, matched;
-
-	memset(targ_spec, 0, sizeof(*targ_spec));
-	targ_spec->btf = targ_btf;
-	targ_spec->root_type_id = targ_id;
-	targ_spec->relo_kind = local_spec->relo_kind;
-
-	if (core_relo_is_type_based(local_spec->relo_kind)) {
-		return bpf_core_types_are_compat(local_spec->btf,
-						 local_spec->root_type_id,
-						 targ_btf, targ_id);
-	}
-
-	local_acc = &local_spec->spec[0];
-	targ_acc = &targ_spec->spec[0];
-
-	if (core_relo_is_enumval_based(local_spec->relo_kind)) {
-		size_t local_essent_len, targ_essent_len;
-		const struct btf_enum *e;
-		const char *targ_name;
-
-		/* has to resolve to an enum */
-		targ_type = skip_mods_and_typedefs(targ_spec->btf, targ_id, &targ_id);
-		if (!btf_is_enum(targ_type))
-			return 0;
-
-		local_essent_len = bpf_core_essential_name_len(local_acc->name);
-
-		for (i = 0, e = btf_enum(targ_type); i < btf_vlen(targ_type); i++, e++) {
-			targ_name = btf__name_by_offset(targ_spec->btf, e->name_off);
-			targ_essent_len = bpf_core_essential_name_len(targ_name);
-			if (targ_essent_len != local_essent_len)
-				continue;
-			if (strncmp(local_acc->name, targ_name, local_essent_len) == 0) {
-				targ_acc->type_id = targ_id;
-				targ_acc->idx = i;
-				targ_acc->name = targ_name;
-				targ_spec->len++;
-				targ_spec->raw_spec[targ_spec->raw_len] = targ_acc->idx;
-				targ_spec->raw_len++;
-				return 1;
-			}
-		}
-		return 0;
-	}
-
-	if (!core_relo_is_field_based(local_spec->relo_kind))
-		return -EINVAL;
-
-	for (i = 0; i < local_spec->len; i++, local_acc++, targ_acc++) {
-		targ_type = skip_mods_and_typedefs(targ_spec->btf, targ_id,
-						   &targ_id);
-		if (!targ_type)
-			return -EINVAL;
-
-		if (local_acc->name) {
-			matched = bpf_core_match_member(local_spec->btf,
-							local_acc,
-							targ_btf, targ_id,
-							targ_spec, &targ_id);
-			if (matched <= 0)
-				return matched;
-		} else {
-			/* for i=0, targ_id is already treated as array element
-			 * type (because it's the original struct), for others
-			 * we should find array element type first
-			 */
-			if (i > 0) {
-				const struct btf_array *a;
-				bool flex;
-
-				if (!btf_is_array(targ_type))
-					return 0;
-
-				a = btf_array(targ_type);
-				flex = is_flex_arr(targ_btf, targ_acc - 1, a);
-				if (!flex && local_acc->idx >= a->nelems)
-					return 0;
-				if (!skip_mods_and_typedefs(targ_btf, a->type,
-							    &targ_id))
-					return -EINVAL;
-			}
-
-			/* too deep struct/union/array nesting */
-			if (targ_spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
-				return -E2BIG;
-
-			targ_acc->type_id = targ_id;
-			targ_acc->idx = local_acc->idx;
-			targ_acc->name = NULL;
-			targ_spec->len++;
-			targ_spec->raw_spec[targ_spec->raw_len] = targ_acc->idx;
-			targ_spec->raw_len++;
-
-			sz = btf__resolve_size(targ_btf, targ_id);
-			if (sz < 0)
-				return sz;
-			targ_spec->bit_offset += local_acc->idx * sz * 8;
-		}
-	}
-
-	return 1;
-}
-
-static int bpf_core_calc_field_relo(const char *prog_name,
-				    const struct bpf_core_relo *relo,
-				    const struct bpf_core_spec *spec,
-				    __u32 *val, __u32 *field_sz, __u32 *type_id,
-				    bool *validate)
-{
-	const struct bpf_core_accessor *acc;
-	const struct btf_type *t;
-	__u32 byte_off, byte_sz, bit_off, bit_sz, field_type_id;
-	const struct btf_member *m;
-	const struct btf_type *mt;
-	bool bitfield;
-	__s64 sz;
-
-	*field_sz = 0;
-
-	if (relo->kind == BPF_FIELD_EXISTS) {
-		*val = spec ? 1 : 0;
-		return 0;
-	}
-
-	if (!spec)
-		return -EUCLEAN; /* request instruction poisoning */
-
-	acc = &spec->spec[spec->len - 1];
-	t = btf__type_by_id(spec->btf, acc->type_id);
-
-	/* a[n] accessor needs special handling */
-	if (!acc->name) {
-		if (relo->kind == BPF_FIELD_BYTE_OFFSET) {
-			*val = spec->bit_offset / 8;
-			/* remember field size for load/store mem size */
-			sz = btf__resolve_size(spec->btf, acc->type_id);
-			if (sz < 0)
-				return -EINVAL;
-			*field_sz = sz;
-			*type_id = acc->type_id;
-		} else if (relo->kind == BPF_FIELD_BYTE_SIZE) {
-			sz = btf__resolve_size(spec->btf, acc->type_id);
-			if (sz < 0)
-				return -EINVAL;
-			*val = sz;
-		} else {
-			pr_warn("prog '%s': relo %d at insn #%d can't be applied to array access\n",
-				prog_name, relo->kind, relo->insn_off / 8);
-			return -EINVAL;
-		}
-		if (validate)
-			*validate = true;
-		return 0;
-	}
-
-	m = btf_members(t) + acc->idx;
-	mt = skip_mods_and_typedefs(spec->btf, m->type, &field_type_id);
-	bit_off = spec->bit_offset;
-	bit_sz = btf_member_bitfield_size(t, acc->idx);
-
-	bitfield = bit_sz > 0;
-	if (bitfield) {
-		byte_sz = mt->size;
-		byte_off = bit_off / 8 / byte_sz * byte_sz;
-		/* figure out smallest int size necessary for bitfield load */
-		while (bit_off + bit_sz - byte_off * 8 > byte_sz * 8) {
-			if (byte_sz >= 8) {
-				/* bitfield can't be read with 64-bit read */
-				pr_warn("prog '%s': relo %d at insn #%d can't be satisfied for bitfield\n",
-					prog_name, relo->kind, relo->insn_off / 8);
-				return -E2BIG;
-			}
-			byte_sz *= 2;
-			byte_off = bit_off / 8 / byte_sz * byte_sz;
-		}
-	} else {
-		sz = btf__resolve_size(spec->btf, field_type_id);
-		if (sz < 0)
-			return -EINVAL;
-		byte_sz = sz;
-		byte_off = spec->bit_offset / 8;
-		bit_sz = byte_sz * 8;
-	}
-
-	/* for bitfields, all the relocatable aspects are ambiguous and we
-	 * might disagree with compiler, so turn off validation of expected
-	 * value, except for signedness
-	 */
-	if (validate)
-		*validate = !bitfield;
-
-	switch (relo->kind) {
-	case BPF_FIELD_BYTE_OFFSET:
-		*val = byte_off;
-		if (!bitfield) {
-			*field_sz = byte_sz;
-			*type_id = field_type_id;
-		}
-		break;
-	case BPF_FIELD_BYTE_SIZE:
-		*val = byte_sz;
-		break;
-	case BPF_FIELD_SIGNED:
-		/* enums will be assumed unsigned */
-		*val = btf_is_enum(mt) ||
-		       (btf_int_encoding(mt) & BTF_INT_SIGNED);
-		if (validate)
-			*validate = true; /* signedness is never ambiguous */
-		break;
-	case BPF_FIELD_LSHIFT_U64:
-#if __BYTE_ORDER == __LITTLE_ENDIAN
-		*val = 64 - (bit_off + bit_sz - byte_off  * 8);
-#else
-		*val = (8 - byte_sz) * 8 + (bit_off - byte_off * 8);
-#endif
-		break;
-	case BPF_FIELD_RSHIFT_U64:
-		*val = 64 - bit_sz;
-		if (validate)
-			*validate = true; /* right shift is never ambiguous */
-		break;
-	case BPF_FIELD_EXISTS:
-	default:
-		return -EOPNOTSUPP;
-	}
-
-	return 0;
-}
-
-static int bpf_core_calc_type_relo(const struct bpf_core_relo *relo,
-				   const struct bpf_core_spec *spec,
-				   __u32 *val)
-{
-	__s64 sz;
-
-	/* type-based relos return zero when target type is not found */
-	if (!spec) {
-		*val = 0;
-		return 0;
-	}
-
-	switch (relo->kind) {
-	case BPF_TYPE_ID_TARGET:
-		*val = spec->root_type_id;
-		break;
-	case BPF_TYPE_EXISTS:
-		*val = 1;
-		break;
-	case BPF_TYPE_SIZE:
-		sz = btf__resolve_size(spec->btf, spec->root_type_id);
-		if (sz < 0)
-			return -EINVAL;
-		*val = sz;
-		break;
-	case BPF_TYPE_ID_LOCAL:
-	/* BPF_TYPE_ID_LOCAL is handled specially and shouldn't get here */
-	default:
-		return -EOPNOTSUPP;
-	}
-
-	return 0;
-}
-
-static int bpf_core_calc_enumval_relo(const struct bpf_core_relo *relo,
-				      const struct bpf_core_spec *spec,
-				      __u32 *val)
-{
-	const struct btf_type *t;
-	const struct btf_enum *e;
-
-	switch (relo->kind) {
-	case BPF_ENUMVAL_EXISTS:
-		*val = spec ? 1 : 0;
-		break;
-	case BPF_ENUMVAL_VALUE:
-		if (!spec)
-			return -EUCLEAN; /* request instruction poisoning */
-		t = btf__type_by_id(spec->btf, spec->spec[0].type_id);
-		e = btf_enum(t) + spec->spec[0].idx;
-		*val = e->val;
-		break;
-	default:
-		return -EOPNOTSUPP;
-	}
-
-	return 0;
-}
-
-struct bpf_core_relo_res
-{
-	/* expected value in the instruction, unless validate == false */
-	__u32 orig_val;
-	/* new value that needs to be patched up to */
-	__u32 new_val;
-	/* relocation unsuccessful, poison instruction, but don't fail load */
-	bool poison;
-	/* some relocations can't be validated against orig_val */
-	bool validate;
-	/* for field byte offset relocations or the forms:
-	 *     *(T *)(rX + <off>) = rY
-	 *     rX = *(T *)(rY + <off>),
-	 * we remember original and resolved field size to adjust direct
-	 * memory loads of pointers and integers; this is necessary for 32-bit
-	 * host kernel architectures, but also allows to automatically
-	 * relocate fields that were resized from, e.g., u32 to u64, etc.
-	 */
-	bool fail_memsz_adjust;
-	__u32 orig_sz;
-	__u32 orig_type_id;
-	__u32 new_sz;
-	__u32 new_type_id;
-};
-
-/* Calculate original and target relocation values, given local and target
- * specs and relocation kind. These values are calculated for each candidate.
- * If there are multiple candidates, resulting values should all be consistent
- * with each other. Otherwise, libbpf will refuse to proceed due to ambiguity.
- * If instruction has to be poisoned, *poison will be set to true.
- */
-static int bpf_core_calc_relo(const char *prog_name,
-			      const struct bpf_core_relo *relo,
-			      int relo_idx,
-			      const struct bpf_core_spec *local_spec,
-			      const struct bpf_core_spec *targ_spec,
-			      struct bpf_core_relo_res *res)
-{
-	int err = -EOPNOTSUPP;
-
-	res->orig_val = 0;
-	res->new_val = 0;
-	res->poison = false;
-	res->validate = true;
-	res->fail_memsz_adjust = false;
-	res->orig_sz = res->new_sz = 0;
-	res->orig_type_id = res->new_type_id = 0;
-
-	if (core_relo_is_field_based(relo->kind)) {
-		err = bpf_core_calc_field_relo(prog_name, relo, local_spec,
-					       &res->orig_val, &res->orig_sz,
-					       &res->orig_type_id, &res->validate);
-		err = err ?: bpf_core_calc_field_relo(prog_name, relo, targ_spec,
-						      &res->new_val, &res->new_sz,
-						      &res->new_type_id, NULL);
-		if (err)
-			goto done;
-		/* Validate if it's safe to adjust load/store memory size.
-		 * Adjustments are performed only if original and new memory
-		 * sizes differ.
-		 */
-		res->fail_memsz_adjust = false;
-		if (res->orig_sz != res->new_sz) {
-			const struct btf_type *orig_t, *new_t;
-
-			orig_t = btf__type_by_id(local_spec->btf, res->orig_type_id);
-			new_t = btf__type_by_id(targ_spec->btf, res->new_type_id);
-
-			/* There are two use cases in which it's safe to
-			 * adjust load/store's mem size:
-			 *   - reading a 32-bit kernel pointer, while on BPF
-			 *   size pointers are always 64-bit; in this case
-			 *   it's safe to "downsize" instruction size due to
-			 *   pointer being treated as unsigned integer with
-			 *   zero-extended upper 32-bits;
-			 *   - reading unsigned integers, again due to
-			 *   zero-extension is preserving the value correctly.
-			 *
-			 * In all other cases it's incorrect to attempt to
-			 * load/store field because read value will be
-			 * incorrect, so we poison relocated instruction.
-			 */
-			if (btf_is_ptr(orig_t) && btf_is_ptr(new_t))
-				goto done;
-			if (btf_is_int(orig_t) && btf_is_int(new_t) &&
-			    btf_int_encoding(orig_t) != BTF_INT_SIGNED &&
-			    btf_int_encoding(new_t) != BTF_INT_SIGNED)
-				goto done;
-
-			/* mark as invalid mem size adjustment, but this will
-			 * only be checked for LDX/STX/ST insns
-			 */
-			res->fail_memsz_adjust = true;
-		}
-	} else if (core_relo_is_type_based(relo->kind)) {
-		err = bpf_core_calc_type_relo(relo, local_spec, &res->orig_val);
-		err = err ?: bpf_core_calc_type_relo(relo, targ_spec, &res->new_val);
-	} else if (core_relo_is_enumval_based(relo->kind)) {
-		err = bpf_core_calc_enumval_relo(relo, local_spec, &res->orig_val);
-		err = err ?: bpf_core_calc_enumval_relo(relo, targ_spec, &res->new_val);
-	}
-
-done:
-	if (err == -EUCLEAN) {
-		/* EUCLEAN is used to signal instruction poisoning request */
-		res->poison = true;
-		err = 0;
-	} else if (err == -EOPNOTSUPP) {
-		/* EOPNOTSUPP means unknown/unsupported relocation */
-		pr_warn("prog '%s': relo #%d: unrecognized CO-RE relocation %s (%d) at insn #%d\n",
-			prog_name, relo_idx, core_relo_kind_str(relo->kind),
-			relo->kind, relo->insn_off / 8);
-	}
-
-	return err;
-}
-
-/*
- * Turn instruction for which CO_RE relocation failed into invalid one with
- * distinct signature.
- */
-static void bpf_core_poison_insn(const char *prog_name, int relo_idx,
-				 int insn_idx, struct bpf_insn *insn)
-{
-	pr_debug("prog '%s': relo #%d: substituting insn #%d w/ invalid insn\n",
-		 prog_name, relo_idx, insn_idx);
-	insn->code = BPF_JMP | BPF_CALL;
-	insn->dst_reg = 0;
-	insn->src_reg = 0;
-	insn->off = 0;
-	/* if this instruction is reachable (not a dead code),
-	 * verifier will complain with the following message:
-	 * invalid func unknown#195896080
-	 */
-	insn->imm = 195896080; /* => 0xbad2310 => "bad relo" */
-}
-
-static int insn_bpf_size_to_bytes(struct bpf_insn *insn)
-{
-	switch (BPF_SIZE(insn->code)) {
-	case BPF_DW: return 8;
-	case BPF_W: return 4;
-	case BPF_H: return 2;
-	case BPF_B: return 1;
-	default: return -1;
-	}
-}
-
-static int insn_bytes_to_bpf_size(__u32 sz)
-{
-	switch (sz) {
-	case 8: return BPF_DW;
-	case 4: return BPF_W;
-	case 2: return BPF_H;
-	case 1: return BPF_B;
-	default: return -1;
-	}
-}
-
-/*
- * Patch relocatable BPF instruction.
- *
- * Patched value is determined by relocation kind and target specification.
- * For existence relocations target spec will be NULL if field/type is not found.
- * Expected insn->imm value is determined using relocation kind and local
- * spec, and is checked before patching instruction. If actual insn->imm value
- * is wrong, bail out with error.
- *
- * Currently supported classes of BPF instruction are:
- * 1. rX = <imm> (assignment with immediate operand);
- * 2. rX += <imm> (arithmetic operations with immediate operand);
- * 3. rX = <imm64> (load with 64-bit immediate value);
- * 4. rX = *(T *)(rY + <off>), where T is one of {u8, u16, u32, u64};
- * 5. *(T *)(rX + <off>) = rY, where T is one of {u8, u16, u32, u64};
- * 6. *(T *)(rX + <off>) = <imm>, where T is one of {u8, u16, u32, u64}.
- */
-static int bpf_core_patch_insn(const char *prog_name, struct bpf_insn *insn,
-			       int insn_idx, const struct bpf_core_relo *relo,
-			       int relo_idx, const struct bpf_core_relo_res *res)
-{
-	__u32 orig_val, new_val;
-	__u8 class;
-
-	class = BPF_CLASS(insn->code);
-
-	if (res->poison) {
-poison:
-		/* poison second part of ldimm64 to avoid confusing error from
-		 * verifier about "unknown opcode 00"
-		 */
-		if (is_ldimm64_insn(insn))
-			bpf_core_poison_insn(prog_name, relo_idx, insn_idx + 1, insn + 1);
-		bpf_core_poison_insn(prog_name, relo_idx, insn_idx, insn);
-		return 0;
-	}
-
-	orig_val = res->orig_val;
-	new_val = res->new_val;
-
-	switch (class) {
-	case BPF_ALU:
-	case BPF_ALU64:
-		if (BPF_SRC(insn->code) != BPF_K)
-			return -EINVAL;
-		if (res->validate && insn->imm != orig_val) {
-			pr_warn("prog '%s': relo #%d: unexpected insn #%d (ALU/ALU64) value: got %u, exp %u -> %u\n",
-				prog_name, relo_idx,
-				insn_idx, insn->imm, orig_val, new_val);
-			return -EINVAL;
-		}
-		orig_val = insn->imm;
-		insn->imm = new_val;
-		pr_debug("prog '%s': relo #%d: patched insn #%d (ALU/ALU64) imm %u -> %u\n",
-			 prog_name, relo_idx, insn_idx,
-			 orig_val, new_val);
-		break;
-	case BPF_LDX:
-	case BPF_ST:
-	case BPF_STX:
-		if (res->validate && insn->off != orig_val) {
-			pr_warn("prog '%s': relo #%d: unexpected insn #%d (LDX/ST/STX) value: got %u, exp %u -> %u\n",
-				prog_name, relo_idx, insn_idx, insn->off, orig_val, new_val);
-			return -EINVAL;
-		}
-		if (new_val > SHRT_MAX) {
-			pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) value too big: %u\n",
-				prog_name, relo_idx, insn_idx, new_val);
-			return -ERANGE;
-		}
-		if (res->fail_memsz_adjust) {
-			pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) accesses field incorrectly. "
-				"Make sure you are accessing pointers, unsigned integers, or fields of matching type and size.\n",
-				prog_name, relo_idx, insn_idx);
-			goto poison;
-		}
-
-		orig_val = insn->off;
-		insn->off = new_val;
-		pr_debug("prog '%s': relo #%d: patched insn #%d (LDX/ST/STX) off %u -> %u\n",
-			 prog_name, relo_idx, insn_idx, orig_val, new_val);
-
-		if (res->new_sz != res->orig_sz) {
-			int insn_bytes_sz, insn_bpf_sz;
-
-			insn_bytes_sz = insn_bpf_size_to_bytes(insn);
-			if (insn_bytes_sz != res->orig_sz) {
-				pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) unexpected mem size: got %d, exp %u\n",
-					prog_name, relo_idx, insn_idx, insn_bytes_sz, res->orig_sz);
-				return -EINVAL;
-			}
-
-			insn_bpf_sz = insn_bytes_to_bpf_size(res->new_sz);
-			if (insn_bpf_sz < 0) {
-				pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) invalid new mem size: %u\n",
-					prog_name, relo_idx, insn_idx, res->new_sz);
-				return -EINVAL;
-			}
-
-			insn->code = BPF_MODE(insn->code) | insn_bpf_sz | BPF_CLASS(insn->code);
-			pr_debug("prog '%s': relo #%d: patched insn #%d (LDX/ST/STX) mem_sz %u -> %u\n",
-				 prog_name, relo_idx, insn_idx, res->orig_sz, res->new_sz);
-		}
-		break;
-	case BPF_LD: {
-		__u64 imm;
-
-		if (!is_ldimm64_insn(insn) ||
-		    insn[0].src_reg != 0 || insn[0].off != 0 ||
-		    insn[1].code != 0 || insn[1].dst_reg != 0 ||
-		    insn[1].src_reg != 0 || insn[1].off != 0) {
-			pr_warn("prog '%s': relo #%d: insn #%d (LDIMM64) has unexpected form\n",
-				prog_name, relo_idx, insn_idx);
-			return -EINVAL;
-		}
-
-		imm = insn[0].imm + ((__u64)insn[1].imm << 32);
-		if (res->validate && imm != orig_val) {
-			pr_warn("prog '%s': relo #%d: unexpected insn #%d (LDIMM64) value: got %llu, exp %u -> %u\n",
-				prog_name, relo_idx,
-				insn_idx, (unsigned long long)imm,
-				orig_val, new_val);
-			return -EINVAL;
-		}
-
-		insn[0].imm = new_val;
-		insn[1].imm = 0; /* currently only 32-bit values are supported */
-		pr_debug("prog '%s': relo #%d: patched insn #%d (LDIMM64) imm64 %llu -> %u\n",
-			 prog_name, relo_idx, insn_idx,
-			 (unsigned long long)imm, new_val);
-		break;
-	}
-	default:
-		pr_warn("prog '%s': relo #%d: trying to relocate unrecognized insn #%d, code:0x%x, src:0x%x, dst:0x%x, off:0x%x, imm:0x%x\n",
-			prog_name, relo_idx, insn_idx, insn->code,
-			insn->src_reg, insn->dst_reg, insn->off, insn->imm);
-		return -EINVAL;
-	}
-
-	return 0;
-}
-
-/* Output spec definition in the format:
- * [<type-id>] (<type-name>) + <raw-spec> => <offset>@<spec>,
- * where <spec> is a C-syntax view of recorded field access, e.g.: x.a[3].b
- */
-static void bpf_core_dump_spec(int level, const struct bpf_core_spec *spec)
-{
-	const struct btf_type *t;
-	const struct btf_enum *e;
-	const char *s;
-	__u32 type_id;
-	int i;
-
-	type_id = spec->root_type_id;
-	t = btf__type_by_id(spec->btf, type_id);
-	s = btf__name_by_offset(spec->btf, t->name_off);
-
-	libbpf_print(level, "[%u] %s %s", type_id, btf_kind_str(t), str_is_empty(s) ? "<anon>" : s);
-
-	if (core_relo_is_type_based(spec->relo_kind))
-		return;
-
-	if (core_relo_is_enumval_based(spec->relo_kind)) {
-		t = skip_mods_and_typedefs(spec->btf, type_id, NULL);
-		e = btf_enum(t) + spec->raw_spec[0];
-		s = btf__name_by_offset(spec->btf, e->name_off);
-
-		libbpf_print(level, "::%s = %u", s, e->val);
-		return;
-	}
-
-	if (core_relo_is_field_based(spec->relo_kind)) {
-		for (i = 0; i < spec->len; i++) {
-			if (spec->spec[i].name)
-				libbpf_print(level, ".%s", spec->spec[i].name);
-			else if (i > 0 || spec->spec[i].idx > 0)
-				libbpf_print(level, "[%u]", spec->spec[i].idx);
-		}
-
-		libbpf_print(level, " (");
-		for (i = 0; i < spec->raw_len; i++)
-			libbpf_print(level, "%s%d", i == 0 ? "" : ":", spec->raw_spec[i]);
-
-		if (spec->bit_offset % 8)
-			libbpf_print(level, " @ offset %u.%u)",
-				     spec->bit_offset / 8, spec->bit_offset % 8);
-		else
-			libbpf_print(level, " @ offset %u)", spec->bit_offset / 8);
-		return;
-	}
-}
-
 static size_t bpf_core_hash_fn(const void *key, void *ctx)
 {
 	return (size_t)key;
@@ -6149,208 +5060,6 @@ static void *u32_as_hash_key(__u32 x)
 	return (void *)(uintptr_t)x;
 }
 
-/*
- * CO-RE relocate single instruction.
- *
- * The outline and important points of the algorithm:
- * 1. For given local type, find corresponding candidate target types.
- *    Candidate type is a type with the same "essential" name, ignoring
- *    everything after last triple underscore (___). E.g., `sample`,
- *    `sample___flavor_one`, `sample___flavor_another_one`, are all candidates
- *    for each other. Names with triple underscore are referred to as
- *    "flavors" and are useful, among other things, to allow to
- *    specify/support incompatible variations of the same kernel struct, which
- *    might differ between different kernel versions and/or build
- *    configurations.
- *
- *    N.B. Struct "flavors" could be generated by bpftool's BTF-to-C
- *    converter, when deduplicated BTF of a kernel still contains more than
- *    one different types with the same name. In that case, ___2, ___3, etc
- *    are appended starting from second name conflict. But start flavors are
- *    also useful to be defined "locally", in BPF program, to extract same
- *    data from incompatible changes between different kernel
- *    versions/configurations. For instance, to handle field renames between
- *    kernel versions, one can use two flavors of the struct name with the
- *    same common name and use conditional relocations to extract that field,
- *    depending on target kernel version.
- * 2. For each candidate type, try to match local specification to this
- *    candidate target type. Matching involves finding corresponding
- *    high-level spec accessors, meaning that all named fields should match,
- *    as well as all array accesses should be within the actual bounds. Also,
- *    types should be compatible (see bpf_core_fields_are_compat for details).
- * 3. It is supported and expected that there might be multiple flavors
- *    matching the spec. As long as all the specs resolve to the same set of
- *    offsets across all candidates, there is no error. If there is any
- *    ambiguity, CO-RE relocation will fail. This is necessary to accomodate
- *    imprefection of BTF deduplication, which can cause slight duplication of
- *    the same BTF type, if some directly or indirectly referenced (by
- *    pointer) type gets resolved to different actual types in different
- *    object files. If such situation occurs, deduplicated BTF will end up
- *    with two (or more) structurally identical types, which differ only in
- *    types they refer to through pointer. This should be OK in most cases and
- *    is not an error.
- * 4. Candidate types search is performed by linearly scanning through all
- *    types in target BTF. It is anticipated that this is overall more
- *    efficient memory-wise and not significantly worse (if not better)
- *    CPU-wise compared to prebuilding a map from all local type names to
- *    a list of candidate type names. It's also sped up by caching resolved
- *    list of matching candidates per each local "root" type ID, that has at
- *    least one bpf_core_relo associated with it. This list is shared
- *    between multiple relocations for the same type ID and is updated as some
- *    of the candidates are pruned due to structural incompatibility.
- */
-static int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
-				    int insn_idx,
-				    const struct bpf_core_relo *relo,
-				    int relo_idx,
-				    const struct btf *local_btf,
-				    struct bpf_core_cand_list *cands)
-{
-	struct bpf_core_spec local_spec, cand_spec, targ_spec = {};
-	struct bpf_core_relo_res cand_res, targ_res;
-	const struct btf_type *local_type;
-	const char *local_name;
-	__u32 local_id;
-	const char *spec_str;
-	int i, j, err;
-
-	local_id = relo->type_id;
-	local_type = btf__type_by_id(local_btf, local_id);
-	if (!local_type)
-		return -EINVAL;
-
-	local_name = btf__name_by_offset(local_btf, local_type->name_off);
-	if (!local_name)
-		return -EINVAL;
-
-	spec_str = btf__name_by_offset(local_btf, relo->access_str_off);
-	if (str_is_empty(spec_str))
-		return -EINVAL;
-
-	err = bpf_core_parse_spec(local_btf, local_id, spec_str, relo->kind, &local_spec);
-	if (err) {
-		pr_warn("prog '%s': relo #%d: parsing [%d] %s %s + %s failed: %d\n",
-			prog_name, relo_idx, local_id, btf_kind_str(local_type),
-			str_is_empty(local_name) ? "<anon>" : local_name,
-			spec_str, err);
-		return -EINVAL;
-	}
-
-	pr_debug("prog '%s': relo #%d: kind <%s> (%d), spec is ", prog_name,
-		 relo_idx, core_relo_kind_str(relo->kind), relo->kind);
-	bpf_core_dump_spec(LIBBPF_DEBUG, &local_spec);
-	libbpf_print(LIBBPF_DEBUG, "\n");
-
-	/* TYPE_ID_LOCAL relo is special and doesn't need candidate search */
-	if (relo->kind == BPF_TYPE_ID_LOCAL) {
-		targ_res.validate = true;
-		targ_res.poison = false;
-		targ_res.orig_val = local_spec.root_type_id;
-		targ_res.new_val = local_spec.root_type_id;
-		goto patch_insn;
-	}
-
-	/* libbpf doesn't support candidate search for anonymous types */
-	if (str_is_empty(spec_str)) {
-		pr_warn("prog '%s': relo #%d: <%s> (%d) relocation doesn't support anonymous types\n",
-			prog_name, relo_idx, core_relo_kind_str(relo->kind), relo->kind);
-		return -EOPNOTSUPP;
-	}
-
-
-	for (i = 0, j = 0; i < cands->len; i++) {
-		err = bpf_core_spec_match(&local_spec, cands->cands[i].btf,
-					  cands->cands[i].id, &cand_spec);
-		if (err < 0) {
-			pr_warn("prog '%s': relo #%d: error matching candidate #%d ",
-				prog_name, relo_idx, i);
-			bpf_core_dump_spec(LIBBPF_WARN, &cand_spec);
-			libbpf_print(LIBBPF_WARN, ": %d\n", err);
-			return err;
-		}
-
-		pr_debug("prog '%s': relo #%d: %s candidate #%d ", prog_name,
-			 relo_idx, err == 0 ? "non-matching" : "matching", i);
-		bpf_core_dump_spec(LIBBPF_DEBUG, &cand_spec);
-		libbpf_print(LIBBPF_DEBUG, "\n");
-
-		if (err == 0)
-			continue;
-
-		err = bpf_core_calc_relo(prog_name, relo, relo_idx, &local_spec, &cand_spec, &cand_res);
-		if (err)
-			return err;
-
-		if (j == 0) {
-			targ_res = cand_res;
-			targ_spec = cand_spec;
-		} else if (cand_spec.bit_offset != targ_spec.bit_offset) {
-			/* if there are many field relo candidates, they
-			 * should all resolve to the same bit offset
-			 */
-			pr_warn("prog '%s': relo #%d: field offset ambiguity: %u != %u\n",
-				prog_name, relo_idx, cand_spec.bit_offset,
-				targ_spec.bit_offset);
-			return -EINVAL;
-		} else if (cand_res.poison != targ_res.poison || cand_res.new_val != targ_res.new_val) {
-			/* all candidates should result in the same relocation
-			 * decision and value, otherwise it's dangerous to
-			 * proceed due to ambiguity
-			 */
-			pr_warn("prog '%s': relo #%d: relocation decision ambiguity: %s %u != %s %u\n",
-				prog_name, relo_idx,
-				cand_res.poison ? "failure" : "success", cand_res.new_val,
-				targ_res.poison ? "failure" : "success", targ_res.new_val);
-			return -EINVAL;
-		}
-
-		cands->cands[j++] = cands->cands[i];
-	}
-
-	/*
-	 * For BPF_FIELD_EXISTS relo or when used BPF program has field
-	 * existence checks or kernel version/config checks, it's expected
-	 * that we might not find any candidates. In this case, if field
-	 * wasn't found in any candidate, the list of candidates shouldn't
-	 * change at all, we'll just handle relocating appropriately,
-	 * depending on relo's kind.
-	 */
-	if (j > 0)
-		cands->len = j;
-
-	/*
-	 * If no candidates were found, it might be both a programmer error,
-	 * as well as expected case, depending whether instruction w/
-	 * relocation is guarded in some way that makes it unreachable (dead
-	 * code) if relocation can't be resolved. This is handled in
-	 * bpf_core_patch_insn() uniformly by replacing that instruction with
-	 * BPF helper call insn (using invalid helper ID). If that instruction
-	 * is indeed unreachable, then it will be ignored and eliminated by
-	 * verifier. If it was an error, then verifier will complain and point
-	 * to a specific instruction number in its log.
-	 */
-	if (j == 0) {
-		pr_debug("prog '%s': relo #%d: no matching targets found\n",
-			 prog_name, relo_idx);
-
-		/* calculate single target relo result explicitly */
-		err = bpf_core_calc_relo(prog_name, relo, relo_idx, &local_spec, NULL, &targ_res);
-		if (err)
-			return err;
-	}
-
-patch_insn:
-	/* bpf_core_patch_insn() should know how to handle missing targ_spec */
-	err = bpf_core_patch_insn(prog_name, insn, insn_idx, relo, relo_idx, &targ_res);
-	if (err) {
-		pr_warn("prog '%s': relo #%d: failed to patch insn #%zu: %d\n",
-			prog_name, relo_idx, relo->insn_off / BPF_INSN_SZ, err);
-		return -EINVAL;
-	}
-
-	return 0;
-}
-
 static int bpf_core_apply_relo(struct bpf_program *prog,
 			       const struct bpf_core_relo *relo,
 			       int relo_idx,
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 3178d5685dce..f7b691d5f9eb 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -425,4 +425,14 @@ static inline void *libbpf_ptr(void *ret)
 	return ret;
 }
 
+static inline bool str_is_empty(const char *s)
+{
+	return !s || !s[0];
+}
+
+static inline bool is_ldimm64_insn(struct bpf_insn *insn)
+{
+	return insn->code == (BPF_LD | BPF_IMM | BPF_DW);
+}
+
 #endif /* __LIBBPF_LIBBPF_INTERNAL_H */
diff --git a/tools/lib/bpf/relo_core.c b/tools/lib/bpf/relo_core.c
new file mode 100644
index 000000000000..8fd5440dc17b
--- /dev/null
+++ b/tools/lib/bpf/relo_core.c
@@ -0,0 +1,1326 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <libgen.h>
+#include <inttypes.h>
+#include <limits.h>
+#include <string.h>
+#include <unistd.h>
+#include <endian.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <ctype.h>
+#include <asm/unistd.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/bpf.h>
+#include <linux/btf.h>
+#include <linux/filter.h>
+#include <linux/list.h>
+#include <linux/limits.h>
+#include <linux/perf_event.h>
+#include <linux/ring_buffer.h>
+#include <linux/version.h>
+#include <sys/epoll.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/vfs.h>
+#include <sys/utsname.h>
+#include <sys/resource.h>
+#include <libelf.h>
+#include <gelf.h>
+#include <zlib.h>
+
+#include "libbpf.h"
+#include "bpf.h"
+#include "btf.h"
+#include "str_error.h"
+#include "libbpf_internal.h"
+
+#define BPF_CORE_SPEC_MAX_LEN 64
+
+/* represents BPF CO-RE field or array element accessor */
+struct bpf_core_accessor {
+	__u32 type_id;		/* struct/union type or array element type */
+	__u32 idx;		/* field index or array index */
+	const char *name;	/* field name or NULL for array accessor */
+};
+
+struct bpf_core_spec {
+	const struct btf *btf;
+	/* high-level spec: named fields and array indices only */
+	struct bpf_core_accessor spec[BPF_CORE_SPEC_MAX_LEN];
+	/* original unresolved (no skip_mods_or_typedefs) root type ID */
+	__u32 root_type_id;
+	/* CO-RE relocation kind */
+	enum bpf_core_relo_kind relo_kind;
+	/* high-level spec length */
+	int len;
+	/* raw, low-level spec: 1-to-1 with accessor spec string */
+	int raw_spec[BPF_CORE_SPEC_MAX_LEN];
+	/* raw spec length */
+	int raw_len;
+	/* field bit offset represented by spec */
+	__u32 bit_offset;
+};
+
+static bool is_flex_arr(const struct btf *btf,
+			const struct bpf_core_accessor *acc,
+			const struct btf_array *arr)
+{
+	const struct btf_type *t;
+
+	/* not a flexible array, if not inside a struct or has non-zero size */
+	if (!acc->name || arr->nelems > 0)
+		return false;
+
+	/* has to be the last member of enclosing struct */
+	t = btf__type_by_id(btf, acc->type_id);
+	return acc->idx == btf_vlen(t) - 1;
+}
+
+static const char *core_relo_kind_str(enum bpf_core_relo_kind kind)
+{
+	switch (kind) {
+	case BPF_FIELD_BYTE_OFFSET: return "byte_off";
+	case BPF_FIELD_BYTE_SIZE: return "byte_sz";
+	case BPF_FIELD_EXISTS: return "field_exists";
+	case BPF_FIELD_SIGNED: return "signed";
+	case BPF_FIELD_LSHIFT_U64: return "lshift_u64";
+	case BPF_FIELD_RSHIFT_U64: return "rshift_u64";
+	case BPF_TYPE_ID_LOCAL: return "local_type_id";
+	case BPF_TYPE_ID_TARGET: return "target_type_id";
+	case BPF_TYPE_EXISTS: return "type_exists";
+	case BPF_TYPE_SIZE: return "type_size";
+	case BPF_ENUMVAL_EXISTS: return "enumval_exists";
+	case BPF_ENUMVAL_VALUE: return "enumval_value";
+	default: return "unknown";
+	}
+}
+
+static bool core_relo_is_field_based(enum bpf_core_relo_kind kind)
+{
+	switch (kind) {
+	case BPF_FIELD_BYTE_OFFSET:
+	case BPF_FIELD_BYTE_SIZE:
+	case BPF_FIELD_EXISTS:
+	case BPF_FIELD_SIGNED:
+	case BPF_FIELD_LSHIFT_U64:
+	case BPF_FIELD_RSHIFT_U64:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static bool core_relo_is_type_based(enum bpf_core_relo_kind kind)
+{
+	switch (kind) {
+	case BPF_TYPE_ID_LOCAL:
+	case BPF_TYPE_ID_TARGET:
+	case BPF_TYPE_EXISTS:
+	case BPF_TYPE_SIZE:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static bool core_relo_is_enumval_based(enum bpf_core_relo_kind kind)
+{
+	switch (kind) {
+	case BPF_ENUMVAL_EXISTS:
+	case BPF_ENUMVAL_VALUE:
+		return true;
+	default:
+		return false;
+	}
+}
+
+/*
+ * Turn bpf_core_relo into a low- and high-level spec representation,
+ * validating correctness along the way, as well as calculating resulting
+ * field bit offset, specified by accessor string. Low-level spec captures
+ * every single level of nestedness, including traversing anonymous
+ * struct/union members. High-level one only captures semantically meaningful
+ * "turning points": named fields and array indicies.
+ * E.g., for this case:
+ *
+ *   struct sample {
+ *       int __unimportant;
+ *       struct {
+ *           int __1;
+ *           int __2;
+ *           int a[7];
+ *       };
+ *   };
+ *
+ *   struct sample *s = ...;
+ *
+ *   int x = &s->a[3]; // access string = '0:1:2:3'
+ *
+ * Low-level spec has 1:1 mapping with each element of access string (it's
+ * just a parsed access string representation): [0, 1, 2, 3].
+ *
+ * High-level spec will capture only 3 points:
+ *   - intial zero-index access by pointer (&s->... is the same as &s[0]...);
+ *   - field 'a' access (corresponds to '2' in low-level spec);
+ *   - array element #3 access (corresponds to '3' in low-level spec).
+ *
+ * Type-based relocations (TYPE_EXISTS/TYPE_SIZE,
+ * TYPE_ID_LOCAL/TYPE_ID_TARGET) don't capture any field information. Their
+ * spec and raw_spec are kept empty.
+ *
+ * Enum value-based relocations (ENUMVAL_EXISTS/ENUMVAL_VALUE) use access
+ * string to specify enumerator's value index that need to be relocated.
+ */
+static int bpf_core_parse_spec(const struct btf *btf,
+			       __u32 type_id,
+			       const char *spec_str,
+			       enum bpf_core_relo_kind relo_kind,
+			       struct bpf_core_spec *spec)
+{
+	int access_idx, parsed_len, i;
+	struct bpf_core_accessor *acc;
+	const struct btf_type *t;
+	const char *name;
+	__u32 id;
+	__s64 sz;
+
+	if (str_is_empty(spec_str) || *spec_str == ':')
+		return -EINVAL;
+
+	memset(spec, 0, sizeof(*spec));
+	spec->btf = btf;
+	spec->root_type_id = type_id;
+	spec->relo_kind = relo_kind;
+
+	/* type-based relocations don't have a field access string */
+	if (core_relo_is_type_based(relo_kind)) {
+		if (strcmp(spec_str, "0"))
+			return -EINVAL;
+		return 0;
+	}
+
+	/* parse spec_str="0:1:2:3:4" into array raw_spec=[0, 1, 2, 3, 4] */
+	while (*spec_str) {
+		if (*spec_str == ':')
+			++spec_str;
+		if (sscanf(spec_str, "%d%n", &access_idx, &parsed_len) != 1)
+			return -EINVAL;
+		if (spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
+			return -E2BIG;
+		spec_str += parsed_len;
+		spec->raw_spec[spec->raw_len++] = access_idx;
+	}
+
+	if (spec->raw_len == 0)
+		return -EINVAL;
+
+	t = skip_mods_and_typedefs(btf, type_id, &id);
+	if (!t)
+		return -EINVAL;
+
+	access_idx = spec->raw_spec[0];
+	acc = &spec->spec[0];
+	acc->type_id = id;
+	acc->idx = access_idx;
+	spec->len++;
+
+	if (core_relo_is_enumval_based(relo_kind)) {
+		if (!btf_is_enum(t) || spec->raw_len > 1 || access_idx >= btf_vlen(t))
+			return -EINVAL;
+
+		/* record enumerator name in a first accessor */
+		acc->name = btf__name_by_offset(btf, btf_enum(t)[access_idx].name_off);
+		return 0;
+	}
+
+	if (!core_relo_is_field_based(relo_kind))
+		return -EINVAL;
+
+	sz = btf__resolve_size(btf, id);
+	if (sz < 0)
+		return sz;
+	spec->bit_offset = access_idx * sz * 8;
+
+	for (i = 1; i < spec->raw_len; i++) {
+		t = skip_mods_and_typedefs(btf, id, &id);
+		if (!t)
+			return -EINVAL;
+
+		access_idx = spec->raw_spec[i];
+		acc = &spec->spec[spec->len];
+
+		if (btf_is_composite(t)) {
+			const struct btf_member *m;
+			__u32 bit_offset;
+
+			if (access_idx >= btf_vlen(t))
+				return -EINVAL;
+
+			bit_offset = btf_member_bit_offset(t, access_idx);
+			spec->bit_offset += bit_offset;
+
+			m = btf_members(t) + access_idx;
+			if (m->name_off) {
+				name = btf__name_by_offset(btf, m->name_off);
+				if (str_is_empty(name))
+					return -EINVAL;
+
+				acc->type_id = id;
+				acc->idx = access_idx;
+				acc->name = name;
+				spec->len++;
+			}
+
+			id = m->type;
+		} else if (btf_is_array(t)) {
+			const struct btf_array *a = btf_array(t);
+			bool flex;
+
+			t = skip_mods_and_typedefs(btf, a->type, &id);
+			if (!t)
+				return -EINVAL;
+
+			flex = is_flex_arr(btf, acc - 1, a);
+			if (!flex && access_idx >= a->nelems)
+				return -EINVAL;
+
+			spec->spec[spec->len].type_id = id;
+			spec->spec[spec->len].idx = access_idx;
+			spec->len++;
+
+			sz = btf__resolve_size(btf, id);
+			if (sz < 0)
+				return sz;
+			spec->bit_offset += access_idx * sz * 8;
+		} else {
+			pr_warn("relo for [%u] %s (at idx %d) captures type [%d] of unexpected kind %s\n",
+				type_id, spec_str, i, id, btf_kind_str(t));
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+/* Check two types for compatibility for the purpose of field access
+ * relocation. const/volatile/restrict and typedefs are skipped to ensure we
+ * are relocating semantically compatible entities:
+ *   - any two STRUCTs/UNIONs are compatible and can be mixed;
+ *   - any two FWDs are compatible, if their names match (modulo flavor suffix);
+ *   - any two PTRs are always compatible;
+ *   - for ENUMs, names should be the same (ignoring flavor suffix) or at
+ *     least one of enums should be anonymous;
+ *   - for ENUMs, check sizes, names are ignored;
+ *   - for INT, size and signedness are ignored;
+ *   - any two FLOATs are always compatible;
+ *   - for ARRAY, dimensionality is ignored, element types are checked for
+ *     compatibility recursively;
+ *   - everything else shouldn't be ever a target of relocation.
+ * These rules are not set in stone and probably will be adjusted as we get
+ * more experience with using BPF CO-RE relocations.
+ */
+static int bpf_core_fields_are_compat(const struct btf *local_btf,
+				      __u32 local_id,
+				      const struct btf *targ_btf,
+				      __u32 targ_id)
+{
+	const struct btf_type *local_type, *targ_type;
+
+recur:
+	local_type = skip_mods_and_typedefs(local_btf, local_id, &local_id);
+	targ_type = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id);
+	if (!local_type || !targ_type)
+		return -EINVAL;
+
+	if (btf_is_composite(local_type) && btf_is_composite(targ_type))
+		return 1;
+	if (btf_kind(local_type) != btf_kind(targ_type))
+		return 0;
+
+	switch (btf_kind(local_type)) {
+	case BTF_KIND_PTR:
+	case BTF_KIND_FLOAT:
+		return 1;
+	case BTF_KIND_FWD:
+	case BTF_KIND_ENUM: {
+		const char *local_name, *targ_name;
+		size_t local_len, targ_len;
+
+		local_name = btf__name_by_offset(local_btf,
+						 local_type->name_off);
+		targ_name = btf__name_by_offset(targ_btf, targ_type->name_off);
+		local_len = bpf_core_essential_name_len(local_name);
+		targ_len = bpf_core_essential_name_len(targ_name);
+		/* one of them is anonymous or both w/ same flavor-less names */
+		return local_len == 0 || targ_len == 0 ||
+		       (local_len == targ_len &&
+			strncmp(local_name, targ_name, local_len) == 0);
+	}
+	case BTF_KIND_INT:
+		/* just reject deprecated bitfield-like integers; all other
+		 * integers are by default compatible between each other
+		 */
+		return btf_int_offset(local_type) == 0 &&
+		       btf_int_offset(targ_type) == 0;
+	case BTF_KIND_ARRAY:
+		local_id = btf_array(local_type)->type;
+		targ_id = btf_array(targ_type)->type;
+		goto recur;
+	default:
+		pr_warn("unexpected kind %d relocated, local [%d], target [%d]\n",
+			btf_kind(local_type), local_id, targ_id);
+		return 0;
+	}
+}
+
+/*
+ * Given single high-level named field accessor in local type, find
+ * corresponding high-level accessor for a target type. Along the way,
+ * maintain low-level spec for target as well. Also keep updating target
+ * bit offset.
+ *
+ * Searching is performed through recursive exhaustive enumeration of all
+ * fields of a struct/union. If there are any anonymous (embedded)
+ * structs/unions, they are recursively searched as well. If field with
+ * desired name is found, check compatibility between local and target types,
+ * before returning result.
+ *
+ * 1 is returned, if field is found.
+ * 0 is returned if no compatible field is found.
+ * <0 is returned on error.
+ */
+static int bpf_core_match_member(const struct btf *local_btf,
+				 const struct bpf_core_accessor *local_acc,
+				 const struct btf *targ_btf,
+				 __u32 targ_id,
+				 struct bpf_core_spec *spec,
+				 __u32 *next_targ_id)
+{
+	const struct btf_type *local_type, *targ_type;
+	const struct btf_member *local_member, *m;
+	const char *local_name, *targ_name;
+	__u32 local_id;
+	int i, n, found;
+
+	targ_type = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id);
+	if (!targ_type)
+		return -EINVAL;
+	if (!btf_is_composite(targ_type))
+		return 0;
+
+	local_id = local_acc->type_id;
+	local_type = btf__type_by_id(local_btf, local_id);
+	local_member = btf_members(local_type) + local_acc->idx;
+	local_name = btf__name_by_offset(local_btf, local_member->name_off);
+
+	n = btf_vlen(targ_type);
+	m = btf_members(targ_type);
+	for (i = 0; i < n; i++, m++) {
+		__u32 bit_offset;
+
+		bit_offset = btf_member_bit_offset(targ_type, i);
+
+		/* too deep struct/union/array nesting */
+		if (spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
+			return -E2BIG;
+
+		/* speculate this member will be the good one */
+		spec->bit_offset += bit_offset;
+		spec->raw_spec[spec->raw_len++] = i;
+
+		targ_name = btf__name_by_offset(targ_btf, m->name_off);
+		if (str_is_empty(targ_name)) {
+			/* embedded struct/union, we need to go deeper */
+			found = bpf_core_match_member(local_btf, local_acc,
+						      targ_btf, m->type,
+						      spec, next_targ_id);
+			if (found) /* either found or error */
+				return found;
+		} else if (strcmp(local_name, targ_name) == 0) {
+			/* matching named field */
+			struct bpf_core_accessor *targ_acc;
+
+			targ_acc = &spec->spec[spec->len++];
+			targ_acc->type_id = targ_id;
+			targ_acc->idx = i;
+			targ_acc->name = targ_name;
+
+			*next_targ_id = m->type;
+			found = bpf_core_fields_are_compat(local_btf,
+							   local_member->type,
+							   targ_btf, m->type);
+			if (!found)
+				spec->len--; /* pop accessor */
+			return found;
+		}
+		/* member turned out not to be what we looked for */
+		spec->bit_offset -= bit_offset;
+		spec->raw_len--;
+	}
+
+	return 0;
+}
+
+/*
+ * Try to match local spec to a target type and, if successful, produce full
+ * target spec (high-level, low-level + bit offset).
+ */
+static int bpf_core_spec_match(struct bpf_core_spec *local_spec,
+			       const struct btf *targ_btf, __u32 targ_id,
+			       struct bpf_core_spec *targ_spec)
+{
+	const struct btf_type *targ_type;
+	const struct bpf_core_accessor *local_acc;
+	struct bpf_core_accessor *targ_acc;
+	int i, sz, matched;
+
+	memset(targ_spec, 0, sizeof(*targ_spec));
+	targ_spec->btf = targ_btf;
+	targ_spec->root_type_id = targ_id;
+	targ_spec->relo_kind = local_spec->relo_kind;
+
+	if (core_relo_is_type_based(local_spec->relo_kind)) {
+		return bpf_core_types_are_compat(local_spec->btf,
+						 local_spec->root_type_id,
+						 targ_btf, targ_id);
+	}
+
+	local_acc = &local_spec->spec[0];
+	targ_acc = &targ_spec->spec[0];
+
+	if (core_relo_is_enumval_based(local_spec->relo_kind)) {
+		size_t local_essent_len, targ_essent_len;
+		const struct btf_enum *e;
+		const char *targ_name;
+
+		/* has to resolve to an enum */
+		targ_type = skip_mods_and_typedefs(targ_spec->btf, targ_id, &targ_id);
+		if (!btf_is_enum(targ_type))
+			return 0;
+
+		local_essent_len = bpf_core_essential_name_len(local_acc->name);
+
+		for (i = 0, e = btf_enum(targ_type); i < btf_vlen(targ_type); i++, e++) {
+			targ_name = btf__name_by_offset(targ_spec->btf, e->name_off);
+			targ_essent_len = bpf_core_essential_name_len(targ_name);
+			if (targ_essent_len != local_essent_len)
+				continue;
+			if (strncmp(local_acc->name, targ_name, local_essent_len) == 0) {
+				targ_acc->type_id = targ_id;
+				targ_acc->idx = i;
+				targ_acc->name = targ_name;
+				targ_spec->len++;
+				targ_spec->raw_spec[targ_spec->raw_len] = targ_acc->idx;
+				targ_spec->raw_len++;
+				return 1;
+			}
+		}
+		return 0;
+	}
+
+	if (!core_relo_is_field_based(local_spec->relo_kind))
+		return -EINVAL;
+
+	for (i = 0; i < local_spec->len; i++, local_acc++, targ_acc++) {
+		targ_type = skip_mods_and_typedefs(targ_spec->btf, targ_id,
+						   &targ_id);
+		if (!targ_type)
+			return -EINVAL;
+
+		if (local_acc->name) {
+			matched = bpf_core_match_member(local_spec->btf,
+							local_acc,
+							targ_btf, targ_id,
+							targ_spec, &targ_id);
+			if (matched <= 0)
+				return matched;
+		} else {
+			/* for i=0, targ_id is already treated as array element
+			 * type (because it's the original struct), for others
+			 * we should find array element type first
+			 */
+			if (i > 0) {
+				const struct btf_array *a;
+				bool flex;
+
+				if (!btf_is_array(targ_type))
+					return 0;
+
+				a = btf_array(targ_type);
+				flex = is_flex_arr(targ_btf, targ_acc - 1, a);
+				if (!flex && local_acc->idx >= a->nelems)
+					return 0;
+				if (!skip_mods_and_typedefs(targ_btf, a->type,
+							    &targ_id))
+					return -EINVAL;
+			}
+
+			/* too deep struct/union/array nesting */
+			if (targ_spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
+				return -E2BIG;
+
+			targ_acc->type_id = targ_id;
+			targ_acc->idx = local_acc->idx;
+			targ_acc->name = NULL;
+			targ_spec->len++;
+			targ_spec->raw_spec[targ_spec->raw_len] = targ_acc->idx;
+			targ_spec->raw_len++;
+
+			sz = btf__resolve_size(targ_btf, targ_id);
+			if (sz < 0)
+				return sz;
+			targ_spec->bit_offset += local_acc->idx * sz * 8;
+		}
+	}
+
+	return 1;
+}
+
+static int bpf_core_calc_field_relo(const char *prog_name,
+				    const struct bpf_core_relo *relo,
+				    const struct bpf_core_spec *spec,
+				    __u32 *val, __u32 *field_sz, __u32 *type_id,
+				    bool *validate)
+{
+	const struct bpf_core_accessor *acc;
+	const struct btf_type *t;
+	__u32 byte_off, byte_sz, bit_off, bit_sz, field_type_id;
+	const struct btf_member *m;
+	const struct btf_type *mt;
+	bool bitfield;
+	__s64 sz;
+
+	*field_sz = 0;
+
+	if (relo->kind == BPF_FIELD_EXISTS) {
+		*val = spec ? 1 : 0;
+		return 0;
+	}
+
+	if (!spec)
+		return -EUCLEAN; /* request instruction poisoning */
+
+	acc = &spec->spec[spec->len - 1];
+	t = btf__type_by_id(spec->btf, acc->type_id);
+
+	/* a[n] accessor needs special handling */
+	if (!acc->name) {
+		if (relo->kind == BPF_FIELD_BYTE_OFFSET) {
+			*val = spec->bit_offset / 8;
+			/* remember field size for load/store mem size */
+			sz = btf__resolve_size(spec->btf, acc->type_id);
+			if (sz < 0)
+				return -EINVAL;
+			*field_sz = sz;
+			*type_id = acc->type_id;
+		} else if (relo->kind == BPF_FIELD_BYTE_SIZE) {
+			sz = btf__resolve_size(spec->btf, acc->type_id);
+			if (sz < 0)
+				return -EINVAL;
+			*val = sz;
+		} else {
+			pr_warn("prog '%s': relo %d at insn #%d can't be applied to array access\n",
+				prog_name, relo->kind, relo->insn_off / 8);
+			return -EINVAL;
+		}
+		if (validate)
+			*validate = true;
+		return 0;
+	}
+
+	m = btf_members(t) + acc->idx;
+	mt = skip_mods_and_typedefs(spec->btf, m->type, &field_type_id);
+	bit_off = spec->bit_offset;
+	bit_sz = btf_member_bitfield_size(t, acc->idx);
+
+	bitfield = bit_sz > 0;
+	if (bitfield) {
+		byte_sz = mt->size;
+		byte_off = bit_off / 8 / byte_sz * byte_sz;
+		/* figure out smallest int size necessary for bitfield load */
+		while (bit_off + bit_sz - byte_off * 8 > byte_sz * 8) {
+			if (byte_sz >= 8) {
+				/* bitfield can't be read with 64-bit read */
+				pr_warn("prog '%s': relo %d at insn #%d can't be satisfied for bitfield\n",
+					prog_name, relo->kind, relo->insn_off / 8);
+				return -E2BIG;
+			}
+			byte_sz *= 2;
+			byte_off = bit_off / 8 / byte_sz * byte_sz;
+		}
+	} else {
+		sz = btf__resolve_size(spec->btf, field_type_id);
+		if (sz < 0)
+			return -EINVAL;
+		byte_sz = sz;
+		byte_off = spec->bit_offset / 8;
+		bit_sz = byte_sz * 8;
+	}
+
+	/* for bitfields, all the relocatable aspects are ambiguous and we
+	 * might disagree with compiler, so turn off validation of expected
+	 * value, except for signedness
+	 */
+	if (validate)
+		*validate = !bitfield;
+
+	switch (relo->kind) {
+	case BPF_FIELD_BYTE_OFFSET:
+		*val = byte_off;
+		if (!bitfield) {
+			*field_sz = byte_sz;
+			*type_id = field_type_id;
+		}
+		break;
+	case BPF_FIELD_BYTE_SIZE:
+		*val = byte_sz;
+		break;
+	case BPF_FIELD_SIGNED:
+		/* enums will be assumed unsigned */
+		*val = btf_is_enum(mt) ||
+		       (btf_int_encoding(mt) & BTF_INT_SIGNED);
+		if (validate)
+			*validate = true; /* signedness is never ambiguous */
+		break;
+	case BPF_FIELD_LSHIFT_U64:
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+		*val = 64 - (bit_off + bit_sz - byte_off  * 8);
+#else
+		*val = (8 - byte_sz) * 8 + (bit_off - byte_off * 8);
+#endif
+		break;
+	case BPF_FIELD_RSHIFT_U64:
+		*val = 64 - bit_sz;
+		if (validate)
+			*validate = true; /* right shift is never ambiguous */
+		break;
+	case BPF_FIELD_EXISTS:
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
+static int bpf_core_calc_type_relo(const struct bpf_core_relo *relo,
+				   const struct bpf_core_spec *spec,
+				   __u32 *val)
+{
+	__s64 sz;
+
+	/* type-based relos return zero when target type is not found */
+	if (!spec) {
+		*val = 0;
+		return 0;
+	}
+
+	switch (relo->kind) {
+	case BPF_TYPE_ID_TARGET:
+		*val = spec->root_type_id;
+		break;
+	case BPF_TYPE_EXISTS:
+		*val = 1;
+		break;
+	case BPF_TYPE_SIZE:
+		sz = btf__resolve_size(spec->btf, spec->root_type_id);
+		if (sz < 0)
+			return -EINVAL;
+		*val = sz;
+		break;
+	case BPF_TYPE_ID_LOCAL:
+	/* BPF_TYPE_ID_LOCAL is handled specially and shouldn't get here */
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
+static int bpf_core_calc_enumval_relo(const struct bpf_core_relo *relo,
+				      const struct bpf_core_spec *spec,
+				      __u32 *val)
+{
+	const struct btf_type *t;
+	const struct btf_enum *e;
+
+	switch (relo->kind) {
+	case BPF_ENUMVAL_EXISTS:
+		*val = spec ? 1 : 0;
+		break;
+	case BPF_ENUMVAL_VALUE:
+		if (!spec)
+			return -EUCLEAN; /* request instruction poisoning */
+		t = btf__type_by_id(spec->btf, spec->spec[0].type_id);
+		e = btf_enum(t) + spec->spec[0].idx;
+		*val = e->val;
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
+struct bpf_core_relo_res
+{
+	/* expected value in the instruction, unless validate == false */
+	__u32 orig_val;
+	/* new value that needs to be patched up to */
+	__u32 new_val;
+	/* relocation unsuccessful, poison instruction, but don't fail load */
+	bool poison;
+	/* some relocations can't be validated against orig_val */
+	bool validate;
+	/* for field byte offset relocations or the forms:
+	 *     *(T *)(rX + <off>) = rY
+	 *     rX = *(T *)(rY + <off>),
+	 * we remember original and resolved field size to adjust direct
+	 * memory loads of pointers and integers; this is necessary for 32-bit
+	 * host kernel architectures, but also allows to automatically
+	 * relocate fields that were resized from, e.g., u32 to u64, etc.
+	 */
+	bool fail_memsz_adjust;
+	__u32 orig_sz;
+	__u32 orig_type_id;
+	__u32 new_sz;
+	__u32 new_type_id;
+};
+
+/* Calculate original and target relocation values, given local and target
+ * specs and relocation kind. These values are calculated for each candidate.
+ * If there are multiple candidates, resulting values should all be consistent
+ * with each other. Otherwise, libbpf will refuse to proceed due to ambiguity.
+ * If instruction has to be poisoned, *poison will be set to true.
+ */
+static int bpf_core_calc_relo(const char *prog_name,
+			      const struct bpf_core_relo *relo,
+			      int relo_idx,
+			      const struct bpf_core_spec *local_spec,
+			      const struct bpf_core_spec *targ_spec,
+			      struct bpf_core_relo_res *res)
+{
+	int err = -EOPNOTSUPP;
+
+	res->orig_val = 0;
+	res->new_val = 0;
+	res->poison = false;
+	res->validate = true;
+	res->fail_memsz_adjust = false;
+	res->orig_sz = res->new_sz = 0;
+	res->orig_type_id = res->new_type_id = 0;
+
+	if (core_relo_is_field_based(relo->kind)) {
+		err = bpf_core_calc_field_relo(prog_name, relo, local_spec,
+					       &res->orig_val, &res->orig_sz,
+					       &res->orig_type_id, &res->validate);
+		err = err ?: bpf_core_calc_field_relo(prog_name, relo, targ_spec,
+						      &res->new_val, &res->new_sz,
+						      &res->new_type_id, NULL);
+		if (err)
+			goto done;
+		/* Validate if it's safe to adjust load/store memory size.
+		 * Adjustments are performed only if original and new memory
+		 * sizes differ.
+		 */
+		res->fail_memsz_adjust = false;
+		if (res->orig_sz != res->new_sz) {
+			const struct btf_type *orig_t, *new_t;
+
+			orig_t = btf__type_by_id(local_spec->btf, res->orig_type_id);
+			new_t = btf__type_by_id(targ_spec->btf, res->new_type_id);
+
+			/* There are two use cases in which it's safe to
+			 * adjust load/store's mem size:
+			 *   - reading a 32-bit kernel pointer, while on BPF
+			 *   size pointers are always 64-bit; in this case
+			 *   it's safe to "downsize" instruction size due to
+			 *   pointer being treated as unsigned integer with
+			 *   zero-extended upper 32-bits;
+			 *   - reading unsigned integers, again due to
+			 *   zero-extension is preserving the value correctly.
+			 *
+			 * In all other cases it's incorrect to attempt to
+			 * load/store field because read value will be
+			 * incorrect, so we poison relocated instruction.
+			 */
+			if (btf_is_ptr(orig_t) && btf_is_ptr(new_t))
+				goto done;
+			if (btf_is_int(orig_t) && btf_is_int(new_t) &&
+			    btf_int_encoding(orig_t) != BTF_INT_SIGNED &&
+			    btf_int_encoding(new_t) != BTF_INT_SIGNED)
+				goto done;
+
+			/* mark as invalid mem size adjustment, but this will
+			 * only be checked for LDX/STX/ST insns
+			 */
+			res->fail_memsz_adjust = true;
+		}
+	} else if (core_relo_is_type_based(relo->kind)) {
+		err = bpf_core_calc_type_relo(relo, local_spec, &res->orig_val);
+		err = err ?: bpf_core_calc_type_relo(relo, targ_spec, &res->new_val);
+	} else if (core_relo_is_enumval_based(relo->kind)) {
+		err = bpf_core_calc_enumval_relo(relo, local_spec, &res->orig_val);
+		err = err ?: bpf_core_calc_enumval_relo(relo, targ_spec, &res->new_val);
+	}
+
+done:
+	if (err == -EUCLEAN) {
+		/* EUCLEAN is used to signal instruction poisoning request */
+		res->poison = true;
+		err = 0;
+	} else if (err == -EOPNOTSUPP) {
+		/* EOPNOTSUPP means unknown/unsupported relocation */
+		pr_warn("prog '%s': relo #%d: unrecognized CO-RE relocation %s (%d) at insn #%d\n",
+			prog_name, relo_idx, core_relo_kind_str(relo->kind),
+			relo->kind, relo->insn_off / 8);
+	}
+
+	return err;
+}
+
+/*
+ * Turn instruction for which CO_RE relocation failed into invalid one with
+ * distinct signature.
+ */
+static void bpf_core_poison_insn(const char *prog_name, int relo_idx,
+				 int insn_idx, struct bpf_insn *insn)
+{
+	pr_debug("prog '%s': relo #%d: substituting insn #%d w/ invalid insn\n",
+		 prog_name, relo_idx, insn_idx);
+	insn->code = BPF_JMP | BPF_CALL;
+	insn->dst_reg = 0;
+	insn->src_reg = 0;
+	insn->off = 0;
+	/* if this instruction is reachable (not a dead code),
+	 * verifier will complain with the following message:
+	 * invalid func unknown#195896080
+	 */
+	insn->imm = 195896080; /* => 0xbad2310 => "bad relo" */
+}
+
+static int insn_bpf_size_to_bytes(struct bpf_insn *insn)
+{
+	switch (BPF_SIZE(insn->code)) {
+	case BPF_DW: return 8;
+	case BPF_W: return 4;
+	case BPF_H: return 2;
+	case BPF_B: return 1;
+	default: return -1;
+	}
+}
+
+static int insn_bytes_to_bpf_size(__u32 sz)
+{
+	switch (sz) {
+	case 8: return BPF_DW;
+	case 4: return BPF_W;
+	case 2: return BPF_H;
+	case 1: return BPF_B;
+	default: return -1;
+	}
+}
+
+/*
+ * Patch relocatable BPF instruction.
+ *
+ * Patched value is determined by relocation kind and target specification.
+ * For existence relocations target spec will be NULL if field/type is not found.
+ * Expected insn->imm value is determined using relocation kind and local
+ * spec, and is checked before patching instruction. If actual insn->imm value
+ * is wrong, bail out with error.
+ *
+ * Currently supported classes of BPF instruction are:
+ * 1. rX = <imm> (assignment with immediate operand);
+ * 2. rX += <imm> (arithmetic operations with immediate operand);
+ * 3. rX = <imm64> (load with 64-bit immediate value);
+ * 4. rX = *(T *)(rY + <off>), where T is one of {u8, u16, u32, u64};
+ * 5. *(T *)(rX + <off>) = rY, where T is one of {u8, u16, u32, u64};
+ * 6. *(T *)(rX + <off>) = <imm>, where T is one of {u8, u16, u32, u64}.
+ */
+static int bpf_core_patch_insn(const char *prog_name, struct bpf_insn *insn,
+			       int insn_idx, const struct bpf_core_relo *relo,
+			       int relo_idx, const struct bpf_core_relo_res *res)
+{
+	__u32 orig_val, new_val;
+	__u8 class;
+
+	class = BPF_CLASS(insn->code);
+
+	if (res->poison) {
+poison:
+		/* poison second part of ldimm64 to avoid confusing error from
+		 * verifier about "unknown opcode 00"
+		 */
+		if (is_ldimm64_insn(insn))
+			bpf_core_poison_insn(prog_name, relo_idx, insn_idx + 1, insn + 1);
+		bpf_core_poison_insn(prog_name, relo_idx, insn_idx, insn);
+		return 0;
+	}
+
+	orig_val = res->orig_val;
+	new_val = res->new_val;
+
+	switch (class) {
+	case BPF_ALU:
+	case BPF_ALU64:
+		if (BPF_SRC(insn->code) != BPF_K)
+			return -EINVAL;
+		if (res->validate && insn->imm != orig_val) {
+			pr_warn("prog '%s': relo #%d: unexpected insn #%d (ALU/ALU64) value: got %u, exp %u -> %u\n",
+				prog_name, relo_idx,
+				insn_idx, insn->imm, orig_val, new_val);
+			return -EINVAL;
+		}
+		orig_val = insn->imm;
+		insn->imm = new_val;
+		pr_debug("prog '%s': relo #%d: patched insn #%d (ALU/ALU64) imm %u -> %u\n",
+			 prog_name, relo_idx, insn_idx,
+			 orig_val, new_val);
+		break;
+	case BPF_LDX:
+	case BPF_ST:
+	case BPF_STX:
+		if (res->validate && insn->off != orig_val) {
+			pr_warn("prog '%s': relo #%d: unexpected insn #%d (LDX/ST/STX) value: got %u, exp %u -> %u\n",
+				prog_name, relo_idx, insn_idx, insn->off, orig_val, new_val);
+			return -EINVAL;
+		}
+		if (new_val > SHRT_MAX) {
+			pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) value too big: %u\n",
+				prog_name, relo_idx, insn_idx, new_val);
+			return -ERANGE;
+		}
+		if (res->fail_memsz_adjust) {
+			pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) accesses field incorrectly. "
+				"Make sure you are accessing pointers, unsigned integers, or fields of matching type and size.\n",
+				prog_name, relo_idx, insn_idx);
+			goto poison;
+		}
+
+		orig_val = insn->off;
+		insn->off = new_val;
+		pr_debug("prog '%s': relo #%d: patched insn #%d (LDX/ST/STX) off %u -> %u\n",
+			 prog_name, relo_idx, insn_idx, orig_val, new_val);
+
+		if (res->new_sz != res->orig_sz) {
+			int insn_bytes_sz, insn_bpf_sz;
+
+			insn_bytes_sz = insn_bpf_size_to_bytes(insn);
+			if (insn_bytes_sz != res->orig_sz) {
+				pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) unexpected mem size: got %d, exp %u\n",
+					prog_name, relo_idx, insn_idx, insn_bytes_sz, res->orig_sz);
+				return -EINVAL;
+			}
+
+			insn_bpf_sz = insn_bytes_to_bpf_size(res->new_sz);
+			if (insn_bpf_sz < 0) {
+				pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) invalid new mem size: %u\n",
+					prog_name, relo_idx, insn_idx, res->new_sz);
+				return -EINVAL;
+			}
+
+			insn->code = BPF_MODE(insn->code) | insn_bpf_sz | BPF_CLASS(insn->code);
+			pr_debug("prog '%s': relo #%d: patched insn #%d (LDX/ST/STX) mem_sz %u -> %u\n",
+				 prog_name, relo_idx, insn_idx, res->orig_sz, res->new_sz);
+		}
+		break;
+	case BPF_LD: {
+		__u64 imm;
+
+		if (!is_ldimm64_insn(insn) ||
+		    insn[0].src_reg != 0 || insn[0].off != 0 ||
+		    insn[1].code != 0 || insn[1].dst_reg != 0 ||
+		    insn[1].src_reg != 0 || insn[1].off != 0) {
+			pr_warn("prog '%s': relo #%d: insn #%d (LDIMM64) has unexpected form\n",
+				prog_name, relo_idx, insn_idx);
+			return -EINVAL;
+		}
+
+		imm = insn[0].imm + ((__u64)insn[1].imm << 32);
+		if (res->validate && imm != orig_val) {
+			pr_warn("prog '%s': relo #%d: unexpected insn #%d (LDIMM64) value: got %llu, exp %u -> %u\n",
+				prog_name, relo_idx,
+				insn_idx, (unsigned long long)imm,
+				orig_val, new_val);
+			return -EINVAL;
+		}
+
+		insn[0].imm = new_val;
+		insn[1].imm = 0; /* currently only 32-bit values are supported */
+		pr_debug("prog '%s': relo #%d: patched insn #%d (LDIMM64) imm64 %llu -> %u\n",
+			 prog_name, relo_idx, insn_idx,
+			 (unsigned long long)imm, new_val);
+		break;
+	}
+	default:
+		pr_warn("prog '%s': relo #%d: trying to relocate unrecognized insn #%d, code:0x%x, src:0x%x, dst:0x%x, off:0x%x, imm:0x%x\n",
+			prog_name, relo_idx, insn_idx, insn->code,
+			insn->src_reg, insn->dst_reg, insn->off, insn->imm);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/* Output spec definition in the format:
+ * [<type-id>] (<type-name>) + <raw-spec> => <offset>@<spec>,
+ * where <spec> is a C-syntax view of recorded field access, e.g.: x.a[3].b
+ */
+static void bpf_core_dump_spec(int level, const struct bpf_core_spec *spec)
+{
+	const struct btf_type *t;
+	const struct btf_enum *e;
+	const char *s;
+	__u32 type_id;
+	int i;
+
+	type_id = spec->root_type_id;
+	t = btf__type_by_id(spec->btf, type_id);
+	s = btf__name_by_offset(spec->btf, t->name_off);
+
+	libbpf_print(level, "[%u] %s %s", type_id, btf_kind_str(t), str_is_empty(s) ? "<anon>" : s);
+
+	if (core_relo_is_type_based(spec->relo_kind))
+		return;
+
+	if (core_relo_is_enumval_based(spec->relo_kind)) {
+		t = skip_mods_and_typedefs(spec->btf, type_id, NULL);
+		e = btf_enum(t) + spec->raw_spec[0];
+		s = btf__name_by_offset(spec->btf, e->name_off);
+
+		libbpf_print(level, "::%s = %u", s, e->val);
+		return;
+	}
+
+	if (core_relo_is_field_based(spec->relo_kind)) {
+		for (i = 0; i < spec->len; i++) {
+			if (spec->spec[i].name)
+				libbpf_print(level, ".%s", spec->spec[i].name);
+			else if (i > 0 || spec->spec[i].idx > 0)
+				libbpf_print(level, "[%u]", spec->spec[i].idx);
+		}
+
+		libbpf_print(level, " (");
+		for (i = 0; i < spec->raw_len; i++)
+			libbpf_print(level, "%s%d", i == 0 ? "" : ":", spec->raw_spec[i]);
+
+		if (spec->bit_offset % 8)
+			libbpf_print(level, " @ offset %u.%u)",
+				     spec->bit_offset / 8, spec->bit_offset % 8);
+		else
+			libbpf_print(level, " @ offset %u)", spec->bit_offset / 8);
+		return;
+	}
+}
+
+/*
+ * CO-RE relocate single instruction.
+ *
+ * The outline and important points of the algorithm:
+ * 1. For given local type, find corresponding candidate target types.
+ *    Candidate type is a type with the same "essential" name, ignoring
+ *    everything after last triple underscore (___). E.g., `sample`,
+ *    `sample___flavor_one`, `sample___flavor_another_one`, are all candidates
+ *    for each other. Names with triple underscore are referred to as
+ *    "flavors" and are useful, among other things, to allow to
+ *    specify/support incompatible variations of the same kernel struct, which
+ *    might differ between different kernel versions and/or build
+ *    configurations.
+ *
+ *    N.B. Struct "flavors" could be generated by bpftool's BTF-to-C
+ *    converter, when deduplicated BTF of a kernel still contains more than
+ *    one different types with the same name. In that case, ___2, ___3, etc
+ *    are appended starting from second name conflict. But start flavors are
+ *    also useful to be defined "locally", in BPF program, to extract same
+ *    data from incompatible changes between different kernel
+ *    versions/configurations. For instance, to handle field renames between
+ *    kernel versions, one can use two flavors of the struct name with the
+ *    same common name and use conditional relocations to extract that field,
+ *    depending on target kernel version.
+ * 2. For each candidate type, try to match local specification to this
+ *    candidate target type. Matching involves finding corresponding
+ *    high-level spec accessors, meaning that all named fields should match,
+ *    as well as all array accesses should be within the actual bounds. Also,
+ *    types should be compatible (see bpf_core_fields_are_compat for details).
+ * 3. It is supported and expected that there might be multiple flavors
+ *    matching the spec. As long as all the specs resolve to the same set of
+ *    offsets across all candidates, there is no error. If there is any
+ *    ambiguity, CO-RE relocation will fail. This is necessary to accomodate
+ *    imprefection of BTF deduplication, which can cause slight duplication of
+ *    the same BTF type, if some directly or indirectly referenced (by
+ *    pointer) type gets resolved to different actual types in different
+ *    object files. If such situation occurs, deduplicated BTF will end up
+ *    with two (or more) structurally identical types, which differ only in
+ *    types they refer to through pointer. This should be OK in most cases and
+ *    is not an error.
+ * 4. Candidate types search is performed by linearly scanning through all
+ *    types in target BTF. It is anticipated that this is overall more
+ *    efficient memory-wise and not significantly worse (if not better)
+ *    CPU-wise compared to prebuilding a map from all local type names to
+ *    a list of candidate type names. It's also sped up by caching resolved
+ *    list of matching candidates per each local "root" type ID, that has at
+ *    least one bpf_core_relo associated with it. This list is shared
+ *    between multiple relocations for the same type ID and is updated as some
+ *    of the candidates are pruned due to structural incompatibility.
+ */
+int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
+			     int insn_idx,
+			     const struct bpf_core_relo *relo,
+			     int relo_idx,
+			     const struct btf *local_btf,
+			     struct bpf_core_cand_list *cands)
+{
+	struct bpf_core_spec local_spec, cand_spec, targ_spec = {};
+	struct bpf_core_relo_res cand_res, targ_res;
+	const struct btf_type *local_type;
+	const char *local_name;
+	__u32 local_id;
+	const char *spec_str;
+	int i, j, err;
+
+	local_id = relo->type_id;
+	local_type = btf__type_by_id(local_btf, local_id);
+	if (!local_type)
+		return -EINVAL;
+
+	local_name = btf__name_by_offset(local_btf, local_type->name_off);
+	if (!local_name)
+		return -EINVAL;
+
+	spec_str = btf__name_by_offset(local_btf, relo->access_str_off);
+	if (str_is_empty(spec_str))
+		return -EINVAL;
+
+	err = bpf_core_parse_spec(local_btf, local_id, spec_str, relo->kind, &local_spec);
+	if (err) {
+		pr_warn("prog '%s': relo #%d: parsing [%d] %s %s + %s failed: %d\n",
+			prog_name, relo_idx, local_id, btf_kind_str(local_type),
+			str_is_empty(local_name) ? "<anon>" : local_name,
+			spec_str, err);
+		return -EINVAL;
+	}
+
+	pr_debug("prog '%s': relo #%d: kind <%s> (%d), spec is ", prog_name,
+		 relo_idx, core_relo_kind_str(relo->kind), relo->kind);
+	bpf_core_dump_spec(LIBBPF_DEBUG, &local_spec);
+	libbpf_print(LIBBPF_DEBUG, "\n");
+
+	/* TYPE_ID_LOCAL relo is special and doesn't need candidate search */
+	if (relo->kind == BPF_TYPE_ID_LOCAL) {
+		targ_res.validate = true;
+		targ_res.poison = false;
+		targ_res.orig_val = local_spec.root_type_id;
+		targ_res.new_val = local_spec.root_type_id;
+		goto patch_insn;
+	}
+
+	/* libbpf doesn't support candidate search for anonymous types */
+	if (str_is_empty(spec_str)) {
+		pr_warn("prog '%s': relo #%d: <%s> (%d) relocation doesn't support anonymous types\n",
+			prog_name, relo_idx, core_relo_kind_str(relo->kind), relo->kind);
+		return -EOPNOTSUPP;
+	}
+
+
+	for (i = 0, j = 0; i < cands->len; i++) {
+		err = bpf_core_spec_match(&local_spec, cands->cands[i].btf,
+					  cands->cands[i].id, &cand_spec);
+		if (err < 0) {
+			pr_warn("prog '%s': relo #%d: error matching candidate #%d ",
+				prog_name, relo_idx, i);
+			bpf_core_dump_spec(LIBBPF_WARN, &cand_spec);
+			libbpf_print(LIBBPF_WARN, ": %d\n", err);
+			return err;
+		}
+
+		pr_debug("prog '%s': relo #%d: %s candidate #%d ", prog_name,
+			 relo_idx, err == 0 ? "non-matching" : "matching", i);
+		bpf_core_dump_spec(LIBBPF_DEBUG, &cand_spec);
+		libbpf_print(LIBBPF_DEBUG, "\n");
+
+		if (err == 0)
+			continue;
+
+		err = bpf_core_calc_relo(prog_name, relo, relo_idx, &local_spec, &cand_spec, &cand_res);
+		if (err)
+			return err;
+
+		if (j == 0) {
+			targ_res = cand_res;
+			targ_spec = cand_spec;
+		} else if (cand_spec.bit_offset != targ_spec.bit_offset) {
+			/* if there are many field relo candidates, they
+			 * should all resolve to the same bit offset
+			 */
+			pr_warn("prog '%s': relo #%d: field offset ambiguity: %u != %u\n",
+				prog_name, relo_idx, cand_spec.bit_offset,
+				targ_spec.bit_offset);
+			return -EINVAL;
+		} else if (cand_res.poison != targ_res.poison || cand_res.new_val != targ_res.new_val) {
+			/* all candidates should result in the same relocation
+			 * decision and value, otherwise it's dangerous to
+			 * proceed due to ambiguity
+			 */
+			pr_warn("prog '%s': relo #%d: relocation decision ambiguity: %s %u != %s %u\n",
+				prog_name, relo_idx,
+				cand_res.poison ? "failure" : "success", cand_res.new_val,
+				targ_res.poison ? "failure" : "success", targ_res.new_val);
+			return -EINVAL;
+		}
+
+		cands->cands[j++] = cands->cands[i];
+	}
+
+	/*
+	 * For BPF_FIELD_EXISTS relo or when used BPF program has field
+	 * existence checks or kernel version/config checks, it's expected
+	 * that we might not find any candidates. In this case, if field
+	 * wasn't found in any candidate, the list of candidates shouldn't
+	 * change at all, we'll just handle relocating appropriately,
+	 * depending on relo's kind.
+	 */
+	if (j > 0)
+		cands->len = j;
+
+	/*
+	 * If no candidates were found, it might be both a programmer error,
+	 * as well as expected case, depending whether instruction w/
+	 * relocation is guarded in some way that makes it unreachable (dead
+	 * code) if relocation can't be resolved. This is handled in
+	 * bpf_core_patch_insn() uniformly by replacing that instruction with
+	 * BPF helper call insn (using invalid helper ID). If that instruction
+	 * is indeed unreachable, then it will be ignored and eliminated by
+	 * verifier. If it was an error, then verifier will complain and point
+	 * to a specific instruction number in its log.
+	 */
+	if (j == 0) {
+		pr_debug("prog '%s': relo #%d: no matching targets found\n",
+			 prog_name, relo_idx);
+
+		/* calculate single target relo result explicitly */
+		err = bpf_core_calc_relo(prog_name, relo, relo_idx, &local_spec, NULL, &targ_res);
+		if (err)
+			return err;
+	}
+
+patch_insn:
+	/* bpf_core_patch_insn() should know how to handle missing targ_spec */
+	err = bpf_core_patch_insn(prog_name, insn, insn_idx, relo, relo_idx, &targ_res);
+	if (err) {
+		pr_warn("prog '%s': relo #%d: failed to patch insn #%u: %d\n",
+			prog_name, relo_idx, relo->insn_off / 8, err);
+		return -EINVAL;
+	}
+
+	return 0;
+}
diff --git a/tools/lib/bpf/relo_core.h b/tools/lib/bpf/relo_core.h
index 62633e73c297..40534650d807 100644
--- a/tools/lib/bpf/relo_core.h
+++ b/tools/lib/bpf/relo_core.h
@@ -89,4 +89,14 @@ struct bpf_core_cand_list {
 	int len;
 };
 
+int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
+			     int insn_idx,
+			     const struct bpf_core_relo *relo,
+			     int relo_idx,
+			     const struct btf *local_btf,
+			     struct bpf_core_cand_list *cands);
+int bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
+			      const struct btf *targ_btf, __u32 targ_id);
+
+size_t bpf_core_essential_name_len(const char *name);
 #endif
-- 
2.30.2


^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [PATCH bpf-next 0/4] libbpf: Move CO-RE logic into separate file.
  2021-07-21  0:08 [PATCH bpf-next 0/4] libbpf: Move CO-RE logic into separate file Alexei Starovoitov
                   ` (3 preceding siblings ...)
  2021-07-21  0:08 ` [PATCH bpf-next 4/4] libbpf: Split CO-RE logic into relo_core.c Alexei Starovoitov
@ 2021-07-22 16:02 ` Toke Høiland-Jørgensen
  2021-07-24  0:23   ` Alexei Starovoitov
  2021-07-26 19:37 ` Andrii Nakryiko
  5 siblings, 1 reply; 10+ messages in thread
From: Toke Høiland-Jørgensen @ 2021-07-22 16:02 UTC (permalink / raw)
  To: Alexei Starovoitov, davem; +Cc: daniel, andrii, netdev, bpf, kernel-team

Alexei Starovoitov <alexei.starovoitov@gmail.com> writes:

> From: Alexei Starovoitov <ast@kernel.org>
>
> Split CO-RE processing logic from libbpf into separate file
> with an interface that doesn't dependend on libbpf internal details.
> As the next step relo_core.c will be compiled with libbpf and with the kernel.

Interesting! What's the use case for having it in the kernel as well? :)

-Toke


^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [PATCH bpf-next 0/4] libbpf: Move CO-RE logic into separate file.
  2021-07-22 16:02 ` [PATCH bpf-next 0/4] libbpf: Move CO-RE logic into separate file Toke Høiland-Jørgensen
@ 2021-07-24  0:23   ` Alexei Starovoitov
  0 siblings, 0 replies; 10+ messages in thread
From: Alexei Starovoitov @ 2021-07-24  0:23 UTC (permalink / raw)
  To: Toke Høiland-Jørgensen
  Cc: David S. Miller, Daniel Borkmann, Andrii Nakryiko,
	Network Development, bpf, Kernel Team

On Thu, Jul 22, 2021 at 9:02 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>
> Alexei Starovoitov <alexei.starovoitov@gmail.com> writes:
>
> > From: Alexei Starovoitov <ast@kernel.org>
> >
> > Split CO-RE processing logic from libbpf into separate file
> > with an interface that doesn't dependend on libbpf internal details.
> > As the next step relo_core.c will be compiled with libbpf and with the kernel.
>
> Interesting! What's the use case for having it in the kernel as well? :)

The main motivation is signed programs, of course.
Also there are other reasons:
- give the verifier precise path to the field in load/store instructions.
Currently it has to guess the field based on integer offset.
That guessing is random in case of a union.
- give the kermel ability to do CO-RE or symbolic field access.
The insn patching is a small part of the bpf_core_apply_relo_insn().
It can be done for x86 and any other archs just as well.
Imagine a true kernel struct randomization.
Not the existing one where gcc plugin does it at build time,
but the one where the kernel randomizes struct cred every single boot.
Or imagine kernel modules that are built once and then can be loaded
and run on a variety of kernels.

^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [PATCH bpf-next 0/4] libbpf: Move CO-RE logic into separate file.
  2021-07-21  0:08 [PATCH bpf-next 0/4] libbpf: Move CO-RE logic into separate file Alexei Starovoitov
                   ` (4 preceding siblings ...)
  2021-07-22 16:02 ` [PATCH bpf-next 0/4] libbpf: Move CO-RE logic into separate file Toke Høiland-Jørgensen
@ 2021-07-26 19:37 ` Andrii Nakryiko
  2021-07-28  4:49   ` Alexei Starovoitov
  5 siblings, 1 reply; 10+ messages in thread
From: Andrii Nakryiko @ 2021-07-26 19:37 UTC (permalink / raw)
  To: Alexei Starovoitov
  Cc: David S. Miller, Daniel Borkmann, Andrii Nakryiko, Networking,
	bpf, Kernel Team

On Tue, Jul 20, 2021 at 5:08 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> From: Alexei Starovoitov <ast@kernel.org>
>
> Split CO-RE processing logic from libbpf into separate file
> with an interface that doesn't dependend on libbpf internal details.
> As the next step relo_core.c will be compiled with libbpf and with the kernel.
> The _internal_ interface between libbpf/CO-RE and kernel/CO-RE will be:
> int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
>                              int insn_idx,
>                              const struct bpf_core_relo *relo,
>                              int relo_idx,
>                              const struct btf *local_btf,
>                              struct bpf_core_cand_list *cands);
> where bpf_core_relo and bpf_core_cand_list are simple types
> prepared by kernel and libbpf.
>
> Though diff stat shows a lot of lines inserted/deleted they are moved lines.
> Pls review with diff.colorMoved.
>
> Alexei Starovoitov (4):
>   libbpf: Cleanup the layering between CORE and bpf_program.
>   libbpf: Split bpf_core_apply_relo() into bpf_program indepdent helper.
>   libbpf: Move CO-RE types into relo_core.h.
>   libbpf: Split CO-RE logic into relo_core.c.
>

LGTM. Applied to bpf-next, fixed typo in patch 3 subject, and also
made few adjustments. Let me know if you object to any of them:

1. I felt like the original copyright year should be preserved when
moving code into a new file, so I've changed relo_core.h's year to
2019. Hope that's fine.
2. relo_core.c didn't have a Copyright line, so I added the /*
Copyright (c) 2019 Facebook */ as well.
3. I trimmed down the list of #includes in core_relo.c, because most
of them were absolutely irrelevant and just preserved as-is from
libbpf.c Everything seems to compile just fine without those.

>  tools/lib/bpf/Build             |    2 +-
>  tools/lib/bpf/libbpf.c          | 1344 +------------------------------
>  tools/lib/bpf/libbpf_internal.h |   81 +-
>  tools/lib/bpf/relo_core.c       | 1326 ++++++++++++++++++++++++++++++
>  tools/lib/bpf/relo_core.h       |  102 +++
>  5 files changed, 1473 insertions(+), 1382 deletions(-)
>  create mode 100644 tools/lib/bpf/relo_core.c
>  create mode 100644 tools/lib/bpf/relo_core.h
>
> --
> 2.30.2
>

^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [PATCH bpf-next 0/4] libbpf: Move CO-RE logic into separate file.
  2021-07-26 19:37 ` Andrii Nakryiko
@ 2021-07-28  4:49   ` Alexei Starovoitov
  2021-07-29 18:43     ` Andrii Nakryiko
  0 siblings, 1 reply; 10+ messages in thread
From: Alexei Starovoitov @ 2021-07-28  4:49 UTC (permalink / raw)
  To: Andrii Nakryiko
  Cc: David S. Miller, Daniel Borkmann, Andrii Nakryiko, Networking,
	bpf, Kernel Team

On Mon, Jul 26, 2021 at 12:38 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Tue, Jul 20, 2021 at 5:08 PM Alexei Starovoitov
> <alexei.starovoitov@gmail.com> wrote:
> >
> > From: Alexei Starovoitov <ast@kernel.org>
> >
> > Split CO-RE processing logic from libbpf into separate file
> > with an interface that doesn't dependend on libbpf internal details.
> > As the next step relo_core.c will be compiled with libbpf and with the kernel.
> > The _internal_ interface between libbpf/CO-RE and kernel/CO-RE will be:
> > int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
> >                              int insn_idx,
> >                              const struct bpf_core_relo *relo,
> >                              int relo_idx,
> >                              const struct btf *local_btf,
> >                              struct bpf_core_cand_list *cands);
> > where bpf_core_relo and bpf_core_cand_list are simple types
> > prepared by kernel and libbpf.
> >
> > Though diff stat shows a lot of lines inserted/deleted they are moved lines.
> > Pls review with diff.colorMoved.
> >
> > Alexei Starovoitov (4):
> >   libbpf: Cleanup the layering between CORE and bpf_program.
> >   libbpf: Split bpf_core_apply_relo() into bpf_program indepdent helper.
> >   libbpf: Move CO-RE types into relo_core.h.
> >   libbpf: Split CO-RE logic into relo_core.c.
> >
>
> LGTM. Applied to bpf-next, fixed typo in patch 3 subject, and also
> made few adjustments. Let me know if you object to any of them:
>
> 1. I felt like the original copyright year should be preserved when
> moving code into a new file, so I've changed relo_core.h's year to
> 2019. Hope that's fine.
> 2. relo_core.c didn't have a Copyright line, so I added the /*
> Copyright (c) 2019 Facebook */ as well.
> 3. I trimmed down the list of #includes in core_relo.c, because most
> of them were absolutely irrelevant and just preserved as-is from
> libbpf.c Everything seems to compile just fine without those.

Thanks! Much appreciate it.
It was on my todo list. I lazily copy-pasted them to avoid
accidental breakage on some archs that I don't have access to
(since I didn't wait for the kernel build bot to process them before I
sent them).
fyi intel folks can include your private tree as well, so you'd have to respin
your patches due to odd 32-bit build breakage. Just email them with
your git tree location.

^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [PATCH bpf-next 0/4] libbpf: Move CO-RE logic into separate file.
  2021-07-28  4:49   ` Alexei Starovoitov
@ 2021-07-29 18:43     ` Andrii Nakryiko
  0 siblings, 0 replies; 10+ messages in thread
From: Andrii Nakryiko @ 2021-07-29 18:43 UTC (permalink / raw)
  To: Alexei Starovoitov
  Cc: David S. Miller, Daniel Borkmann, Andrii Nakryiko, Networking,
	bpf, Kernel Team

On Tue, Jul 27, 2021 at 9:49 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Mon, Jul 26, 2021 at 12:38 PM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
> >
> > On Tue, Jul 20, 2021 at 5:08 PM Alexei Starovoitov
> > <alexei.starovoitov@gmail.com> wrote:
> > >
> > > From: Alexei Starovoitov <ast@kernel.org>
> > >
> > > Split CO-RE processing logic from libbpf into separate file
> > > with an interface that doesn't dependend on libbpf internal details.
> > > As the next step relo_core.c will be compiled with libbpf and with the kernel.
> > > The _internal_ interface between libbpf/CO-RE and kernel/CO-RE will be:
> > > int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
> > >                              int insn_idx,
> > >                              const struct bpf_core_relo *relo,
> > >                              int relo_idx,
> > >                              const struct btf *local_btf,
> > >                              struct bpf_core_cand_list *cands);
> > > where bpf_core_relo and bpf_core_cand_list are simple types
> > > prepared by kernel and libbpf.
> > >
> > > Though diff stat shows a lot of lines inserted/deleted they are moved lines.
> > > Pls review with diff.colorMoved.
> > >
> > > Alexei Starovoitov (4):
> > >   libbpf: Cleanup the layering between CORE and bpf_program.
> > >   libbpf: Split bpf_core_apply_relo() into bpf_program indepdent helper.
> > >   libbpf: Move CO-RE types into relo_core.h.
> > >   libbpf: Split CO-RE logic into relo_core.c.
> > >
> >
> > LGTM. Applied to bpf-next, fixed typo in patch 3 subject, and also
> > made few adjustments. Let me know if you object to any of them:
> >
> > 1. I felt like the original copyright year should be preserved when
> > moving code into a new file, so I've changed relo_core.h's year to
> > 2019. Hope that's fine.
> > 2. relo_core.c didn't have a Copyright line, so I added the /*
> > Copyright (c) 2019 Facebook */ as well.
> > 3. I trimmed down the list of #includes in core_relo.c, because most
> > of them were absolutely irrelevant and just preserved as-is from
> > libbpf.c Everything seems to compile just fine without those.
>
> Thanks! Much appreciate it.
> It was on my todo list. I lazily copy-pasted them to avoid
> accidental breakage on some archs that I don't have access to
> (since I didn't wait for the kernel build bot to process them before I
> sent them).
> fyi intel folks can include your private tree as well, so you'd have to respin
> your patches due to odd 32-bit build breakage. Just email them with
> your git tree location.

yeah, that's a good idea, I'll email them

^ permalink raw reply	[flat|nested] 10+ messages in thread

end of thread, other threads:[~2021-07-29 18:43 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-07-21  0:08 [PATCH bpf-next 0/4] libbpf: Move CO-RE logic into separate file Alexei Starovoitov
2021-07-21  0:08 ` [PATCH bpf-next 1/4] libbpf: Cleanup the layering between CORE and bpf_program Alexei Starovoitov
2021-07-21  0:08 ` [PATCH bpf-next 2/4] libbpf: Split bpf_core_apply_relo() into bpf_program indepdent helper Alexei Starovoitov
2021-07-21  0:08 ` [PATCH bpf-next 3/4] libbpf: Move CO-RE types into relo_core.h Alexei Starovoitov
2021-07-21  0:08 ` [PATCH bpf-next 4/4] libbpf: Split CO-RE logic into relo_core.c Alexei Starovoitov
2021-07-22 16:02 ` [PATCH bpf-next 0/4] libbpf: Move CO-RE logic into separate file Toke Høiland-Jørgensen
2021-07-24  0:23   ` Alexei Starovoitov
2021-07-26 19:37 ` Andrii Nakryiko
2021-07-28  4:49   ` Alexei Starovoitov
2021-07-29 18:43     ` Andrii Nakryiko

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox