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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 2/8] bpf: Enable BPF_TRAMP_F_IP_ARG for trampolines with call_get_func_ip
Date: Wed, 14 Jul 2021 11:43:54 +0200	[thread overview]
Message-ID: <20210714094400.396467-3-jolsa@kernel.org> (raw)
In-Reply-To: <20210714094400.396467-1-jolsa@kernel.org>

Enabling BPF_TRAMP_F_IP_ARG for trampolines that actually need it.

The BPF_TRAMP_F_IP_ARG adds extra 3 instructions to trampoline code
and is used only by programs with bpf_get_func_ip helper, which is
added in following patch and sets call_get_func_ip bit.

This patch ensures that BPF_TRAMP_F_IP_ARG flag is used only for
trampolines that have programs with call_get_func_ip set.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 include/linux/filter.h  |  3 ++-
 kernel/bpf/trampoline.c | 12 +++++++++---
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 472f97074da0..ba36989f711a 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -559,7 +559,8 @@ struct bpf_prog {
 				kprobe_override:1, /* Do we override a kprobe? */
 				has_callchain_buf:1, /* callchain buffer allocated? */
 				enforce_expected_attach_type:1, /* Enforce expected_attach_type checking at attach time */
-				call_get_stack:1; /* Do we call bpf_get_stack() or bpf_get_stackid() */
+				call_get_stack:1, /* Do we call bpf_get_stack() or bpf_get_stackid() */
+				call_get_func_ip:1; /* Do we call get_func_ip() */
 	enum bpf_prog_type	type;		/* Type of BPF program */
 	enum bpf_attach_type	expected_attach_type; /* For some prog types */
 	u32			len;		/* Number of filter blocks */
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 28a3630c48ee..b2535acfe9db 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -172,7 +172,7 @@ static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
 }
 
 static struct bpf_tramp_progs *
-bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total)
+bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total, bool *ip_arg)
 {
 	const struct bpf_prog_aux *aux;
 	struct bpf_tramp_progs *tprogs;
@@ -189,8 +189,10 @@ bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total)
 		*total += tr->progs_cnt[kind];
 		progs = tprogs[kind].progs;
 
-		hlist_for_each_entry(aux, &tr->progs_hlist[kind], tramp_hlist)
+		hlist_for_each_entry(aux, &tr->progs_hlist[kind], tramp_hlist) {
+			*ip_arg |= aux->prog->call_get_func_ip;
 			*progs++ = aux->prog;
+		}
 	}
 	return tprogs;
 }
@@ -333,9 +335,10 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr)
 	struct bpf_tramp_image *im;
 	struct bpf_tramp_progs *tprogs;
 	u32 flags = BPF_TRAMP_F_RESTORE_REGS;
+	bool ip_arg = false;
 	int err, total;
 
-	tprogs = bpf_trampoline_get_progs(tr, &total);
+	tprogs = bpf_trampoline_get_progs(tr, &total, &ip_arg);
 	if (IS_ERR(tprogs))
 		return PTR_ERR(tprogs);
 
@@ -357,6 +360,9 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr)
 	    tprogs[BPF_TRAMP_MODIFY_RETURN].nr_progs)
 		flags = BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
 
+	if (ip_arg)
+		flags |= BPF_TRAMP_F_IP_ARG;
+
 	err = arch_prepare_bpf_trampoline(im, im->image, im->image + PAGE_SIZE,
 					  &tr->func.model, flags, tprogs,
 					  tr->func.addr);
-- 
2.31.1


  parent 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 ` [PATCHv4 bpf-next 1/8] bpf, x86: Store caller's ip in trampoline stack Jiri Olsa
2021-07-14  9:43 ` Jiri Olsa [this message]
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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