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From: Jiri Olsa <jolsa@redhat.com>
To: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andriin@fb.com>
Cc: netdev@vger.kernel.org, bpf@vger.kernel.org,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@chromium.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Alan Maguire <alan.maguire@oracle.com>
Subject: [PATCHv4 bpf-next 1/8] bpf, x86: Store caller's ip in trampoline stack
Date: Wed, 14 Jul 2021 11:43:53 +0200	[thread overview]
Message-ID: <20210714094400.396467-2-jolsa@kernel.org> (raw)
In-Reply-To: <20210714094400.396467-1-jolsa@kernel.org>

Storing caller's ip in trampoline's stack. Trampoline programs
can reach the IP in (ctx - 8) address, so there's no change in
program's arguments interface.

The IP address is takes from [fp + 8], which is return address
from the initial 'call fentry' call to trampoline.

This IP address will be returned via bpf_get_func_ip helper
helper, which is added in following patches.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 arch/x86/net/bpf_jit_comp.c | 19 +++++++++++++++++++
 include/linux/bpf.h         |  5 +++++
 2 files changed, 24 insertions(+)

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index e835164189f1..c320b3ce7b58 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1951,6 +1951,9 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
 	if (flags & BPF_TRAMP_F_CALL_ORIG)
 		stack_size += 8; /* room for return value of orig_call */
 
+	if (flags & BPF_TRAMP_F_IP_ARG)
+		stack_size += 8; /* room for IP address argument */
+
 	if (flags & BPF_TRAMP_F_SKIP_FRAME)
 		/* skip patched call instruction and point orig_call to actual
 		 * body of the kernel function.
@@ -1964,6 +1967,22 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
 	EMIT4(0x48, 0x83, 0xEC, stack_size); /* sub rsp, stack_size */
 	EMIT1(0x53);		 /* push rbx */
 
+	if (flags & BPF_TRAMP_F_IP_ARG) {
+		/* Store IP address of the traced function:
+		 * mov rax, QWORD PTR [rbp + 8]
+		 * sub rax, X86_PATCH_SIZE
+		 * mov QWORD PTR [rbp - stack_size], rax
+		 */
+		emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, 8);
+		EMIT4(0x48, 0x83, 0xe8, X86_PATCH_SIZE);
+		emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -stack_size);
+
+		/* Continue with stack_size for regs storage, stack will
+		 * be correctly restored with 'leave' instruction.
+		 */
+		stack_size -= 8;
+	}
+
 	save_regs(m, &prog, nr_args, stack_size);
 
 	if (flags & BPF_TRAMP_F_CALL_ORIG) {
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 4afbff308ca3..1ebb7690af91 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -554,6 +554,11 @@ struct btf_func_model {
  */
 #define BPF_TRAMP_F_SKIP_FRAME		BIT(2)
 
+/* Store IP address of the caller on the trampoline stack,
+ * so it's available for trampoline's programs.
+ */
+#define BPF_TRAMP_F_IP_ARG		BIT(3)
+
 /* Each call __bpf_prog_enter + call bpf_func + call __bpf_prog_exit is ~50
  * bytes on x86.  Pick a number to fit into BPF_IMAGE_SIZE / 2
  */
-- 
2.31.1


  reply	other threads:[~2021-07-14  9:44 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-14  9:43 [PATCHv4 bpf-next 0/8] bpf, x86: Add bpf_get_func_ip helper Jiri Olsa
2021-07-14  9:43 ` Jiri Olsa [this message]
2021-07-14  9:43 ` [PATCHv4 bpf-next 2/8] bpf: Enable BPF_TRAMP_F_IP_ARG for trampolines with call_get_func_ip Jiri Olsa
2021-07-14  9:43 ` [PATCHv4 bpf-next 3/8] bpf: Add bpf_get_func_ip helper for tracing programs Jiri Olsa
2021-07-16  1:09   ` Alexei Starovoitov
2021-07-18 19:30     ` Jiri Olsa
2021-07-14  9:43 ` [PATCHv4 bpf-next 4/8] bpf: Add bpf_get_func_ip helper for kprobe programs Jiri Olsa
2021-07-14  9:43 ` [PATCHv4 bpf-next 5/8] selftests/bpf: Add test for bpf_get_func_ip helper Jiri Olsa
2021-07-14  9:43 ` [PATCHv4 bpf-next 6/8] libbpf: Add bpf_program__attach_kprobe_opts function Jiri Olsa
2021-07-17  1:41   ` Andrii Nakryiko
2021-07-18 19:32     ` Jiri Olsa
2021-07-18 21:30       ` Andrii Nakryiko
2021-07-14  9:43 ` [PATCHv4 bpf-next 7/8] libbpf: Allow specification of "kprobe/function+offset" Jiri Olsa
2021-07-17  1:42   ` Andrii Nakryiko
2021-07-18 19:32     ` Jiri Olsa
2021-07-14  9:44 ` [PATCHv4 bpf-next 8/8] selftests/bpf: Add test for bpf_get_func_ip in kprobe+offset probe Jiri Olsa

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