[PATCH v2 1/2] libbpf: Use probe_name for legacy kprobe

Fix a bug in commit 46ed5fc33db9, which wrongly used the
func_name instead of probe_name to register legacy kprobe.

Fixes: 46ed5fc33db9 ("libbpf: Refactor and simplify legacy kprobe code")
Reviewed-by: Hengqi Chen <hengqi.chen@gmail.com>
Tested-by: Hengqi Chen <hengqi.chen@gmail.com>
Co-developed-by: Chengming Zhou <redacted>
Signed-off-by: Qiang Wang <redacted>
Signed-off-by: Chengming Zhou <redacted>
---
 tools/lib/bpf/libbpf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 7c74342bb668..b7d6c951fa09 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c

@@ -9735,7 +9735,7 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
 		gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name),
 					     func_name, offset);
 
-		legacy_probe = strdup(func_name);
+		legacy_probe = strdup(probe_name);
 		if (!legacy_probe)
 			return libbpf_err_ptr(-ENOMEM);
 

-- 
2.20.1

If repeated legacy kprobes on same function in one process,
libbpf will register using the same probe name and got -EBUSY
error. So append index to the probe name format to fix this
problem.

Co-developed-by: Chengming Zhou <redacted>
Signed-off-by: Qiang Wang <redacted>
Signed-off-by: Chengming Zhou <redacted>
---
 tools/lib/bpf/libbpf.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index b7d6c951fa09..698e8864da02 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c

@@ -9634,7 +9634,10 @@ static int append_to_file(const char *file, const char *fmt, ...)
 static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
 					 const char *kfunc_name, size_t offset)
 {
-	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), kfunc_name, offset);
+	static int index = 0;
+
+	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset,
+		 __sync_fetch_and_add(&index, 1));
 }
 
 static int add_kprobe_event_legacy(const char *probe_name, bool retprobe,

-- 
2.20.1

Hello:

This series was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko [off-list ref]:

On Mon, 27 Dec 2021 21:07:12 +0800 you wrote:

Fix a bug in commit 46ed5fc33db9, which wrongly used the
func_name instead of probe_name to register legacy kprobe.

Fixes: 46ed5fc33db9 ("libbpf: Refactor and simplify legacy kprobe code")
Reviewed-by: Hengqi Chen <hengqi.chen@gmail.com>
Tested-by: Hengqi Chen <hengqi.chen@gmail.com>
Co-developed-by: Chengming Zhou <redacted>
Signed-off-by: Qiang Wang <redacted>
Signed-off-by: Chengming Zhou <redacted>

[...]

Here is the summary with links:
  - [v2,1/2] libbpf: Use probe_name for legacy kprobe
    https://git.kernel.org/bpf/bpf-next/c/71cff670baff
  - [v2,2/2] libbpf: Support repeated legacy kprobes on same function
    https://git.kernel.org/bpf/bpf-next/c/51a33c60f1c2

You are awesome, thank you!
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