[PATCH bpf-next] libbpf: Fix uretprobe.multi.s programs auto attachment

[PATCH bpf-next] libbpf: Fix uretprobe.multi.s programs auto attachment

[Jiri Olsa]

As reported by Andrii we don't currently recognize uretprobe.multi.s
programs as return probes due to using (wrong) strcmp function.

Using strncmp instead to match uretprobe.multi as prefix.

Tests are passing, because the return program was executed
as entry program and all counts were incremented properly.

Reported-by: Andrii Nakryiko <andrii@kernel.org>
Closes: https://lore.kernel.org/bpf/CAEf4BzYpH_2f0eHwQG205Q_4hewbtC9OrVSA-_jn6ysz53QbBg@mail.gmail.com/
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 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 4f29e06c2641..08e110392516 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -11688,7 +11688,7 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru
 		ret = 0;
 		break;
 	case 3:
-		opts.retprobe = strcmp(probe_type, "uretprobe.multi") == 0;
+		opts.retprobe = strncmp(probe_type, "uretprobe.multi", sizeof("uretprobe.multi") - 1) == 0;
 		*link = bpf_program__attach_uprobe_multi(prog, -1, binary_path, func_name, &opts);
 		ret = libbpf_get_error(*link);
 		break;
-- 
2.46.0

Re: [PATCH bpf-next] libbpf: Fix uretprobe.multi.s programs auto attachment

[Andrii Nakryiko]

On Tue, Sep 10, 2024 at 5:53 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> As reported by Andrii we don't currently recognize uretprobe.multi.s
> programs as return probes due to using (wrong) strcmp function.
>
> Using strncmp instead to match uretprobe.multi as prefix.
>
> Tests are passing, because the return program was executed
> as entry program and all counts were incremented properly.
>
> Reported-by: Andrii Nakryiko <andrii@kernel.org>
> Closes: https://lore.kernel.org/bpf/CAEf4BzYpH_2f0eHwQG205Q_4hewbtC9OrVSA-_jn6ysz53QbBg@mail.gmail.com/
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>  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 4f29e06c2641..08e110392516 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -11688,7 +11688,7 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru
>                 ret = 0;
>                 break;
>         case 3:
> -               opts.retprobe = strcmp(probe_type, "uretprobe.multi") == 0;
> +               opts.retprobe = strncmp(probe_type, "uretprobe.multi", sizeof("uretprobe.multi") - 1) == 0;

I replaced this with `opts.retprobe = str_has_pfx(probe_type,
"uretprobe.multi");`, less duplication


>                 *link = bpf_program__attach_uprobe_multi(prog, -1, binary_path, func_name, &opts);
>                 ret = libbpf_get_error(*link);
>                 break;
> --
> 2.46.0
>

Re: [PATCH bpf-next] libbpf: Fix uretprobe.multi.s programs auto attachment

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <andrii@kernel.org>:

On Tue, 10 Sep 2024 14:53:36 +0200 you wrote:
> As reported by Andrii we don't currently recognize uretprobe.multi.s
> programs as return probes due to using (wrong) strcmp function.
> 
> Using strncmp instead to match uretprobe.multi as prefix.
> 
> Tests are passing, because the return program was executed
> as entry program and all counts were incremented properly.
> 
> [...]

Here is the summary with links:
  - [bpf-next] libbpf: Fix uretprobe.multi.s programs auto attachment
    https://git.kernel.org/bpf/bpf-next/c/8c8b47597403

You are awesome, thank you!
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