linux-kernel - [PATCH bpf-next] samples/bpf: Fix tracex2 error: No such file or directory

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Date:   Sat, 29 Oct 2022 17:11:13 +0800
From:   Rong Tao <rtoax@...mail.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Rong Tao <rongtao@...tc.cn>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        bpf@...r.kernel.org (open list:BPF [GENERAL] (Safe Dynamic Programs and
        Tools)), linux-kernel@...r.kernel.org (open list)
Subject: [PATCH bpf-next] samples/bpf: Fix tracex2 error: No such file or directory

From: Rong Tao <rongtao@...tc.cn>

since commit c504e5c2f964("net: skb: introduce kfree_skb_reason()")
kfree_skb() is replaced by kfree_skb_reason() and kfree_skb() is set to
the inline function. So, we replace kprobe/kfree_skb with
kprobe/kfree_skb_reason to solve the tracex2 error.

 $ cd samples/bpf
 $ sudo ./tracex2
 libbpf: prog 'bpf_prog2': failed to create kprobe 'kfree_skb+0x0' perf event: No such file or directory
 ERROR: bpf_program__attach failed

Signed-off-by: Rong Tao <rongtao@...tc.cn>
---
 samples/bpf/tracex2_kern.c | 4 ++--
 samples/bpf/tracex2_user.c | 3 ++-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/samples/bpf/tracex2_kern.c b/samples/bpf/tracex2_kern.c
index 5bc696bac27d..93e0b7680b4f 100644
--- a/samples/bpf/tracex2_kern.c
+++ b/samples/bpf/tracex2_kern.c
@@ -22,14 +22,14 @@ struct {
 /* kprobe is NOT a stable ABI. If kernel internals change this bpf+kprobe
  * example will no longer be meaningful
  */
-SEC("kprobe/kfree_skb")
+SEC("kprobe/kfree_skb_reason")
 int bpf_prog2(struct pt_regs *ctx)
 {
 	long loc = 0;
 	long init_val = 1;
 	long *value;
 
-	/* read ip of kfree_skb caller.
+	/* read ip of kfree_skb_reason caller.
 	 * non-portable version of __builtin_return_address(0)
 	 */
 	BPF_KPROBE_READ_RET_IP(loc, ctx);
diff --git a/samples/bpf/tracex2_user.c b/samples/bpf/tracex2_user.c
index dd6205c6b6a7..089e408abd7a 100644
--- a/samples/bpf/tracex2_user.c
+++ b/samples/bpf/tracex2_user.c
@@ -146,7 +146,8 @@ int main(int ac, char **argv)
 	signal(SIGINT, int_exit);
 	signal(SIGTERM, int_exit);
 
-	/* start 'ping' in the background to have some kfree_skb events */
+	/* start 'ping' in the background to have some kfree_skb_reason
+	 * events */
 	f = popen("ping -4 -c5 localhost", "r");
 	(void) f;
 
-- 
2.31.1