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

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

[Qiang Wang]

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")
Co-developed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Qiang Wang <wangqiang.wq.frank@bytedance.com>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
---
 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

[PATCH 2/2] libbpf: Support repeated legacy kprobes on same function

[Qiang Wang]

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 <zhouchengming@bytedance.com>
Signed-off-by: Qiang Wang <wangqiang.wq.frank@bytedance.com>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
---
 tools/lib/bpf/libbpf.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index b7d6c951fa09..0c41a45ffd54 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -9634,7 +9634,9 @@ 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

Re: [PATCH 2/2] libbpf: Support repeated legacy kprobes on same function

[Hengqi Chen]

On 2021/12/25 4:32 PM, Qiang Wang wrote:
> 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 <zhouchengming@bytedance.com>
> Signed-off-by: Qiang Wang <wangqiang.wq.frank@bytedance.com>
> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
> ---
>  tools/lib/bpf/libbpf.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index b7d6c951fa09..0c41a45ffd54 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -9634,7 +9634,9 @@ 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;

Add empty line after variable declaration.

> +	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset

Missing a comma after offset.

> +		 __sync_fetch_and_add(&index, 1));
>  }
>  
>  static int add_kprobe_event_legacy(const char *probe_name, bool retprobe,

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

[Hengqi Chen]

On 2021/12/25 4:32 PM, Qiang Wang 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")
> Co-developed-by: Chengming Zhou <zhouchengming@bytedance.com>
> Signed-off-by: Qiang Wang <wangqiang.wq.frank@bytedance.com>
> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
> ---
>  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);
>  

Reviewed-by: Hengqi Chen <hengqi.chen@gmail.com>
Tested-by: Hengqi Chen <hengqi.chen@gmail.com>