[PATCH bpf-next] bpf: Add __printf attribute to bpf_diag_source()

[PATCH bpf-next] bpf: Add __printf attribute to bpf_diag_source()

[Adrián García Casado]

Building kernel/bpf/diagnostics.o with W=1 triggers the following
compiler warning:

  kernel/bpf/diagnostics.c:828:9: warning: function 'bpf_diag_source'
  might be a candidate for 'gnu_printf' format attribute
  [-Wsuggest-attribute=format]

bpf_diag_source() forwards its format string and variadic arguments to
bpf_diag_vfmt(), which is annotated with __printf(2, 0).

Add the missing __printf(4, 5) attribute to bpf_diag_source() to silence
the W=1 warning and enable compile-time format string checking for its
callers.

Signed-off-by: Adrián García Casado <adriangarciacasado42@gmail.com>
---
 kernel/bpf/diagnostics.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/bpf/diagnostics.c b/kernel/bpf/diagnostics.c
index 0abbbe177e..2421f52eec 100644
--- a/kernel/bpf/diagnostics.c
+++ b/kernel/bpf/diagnostics.c
@@ -794,6 +794,7 @@ static void diag_print_insn_context(struct bpf_verifier_env *env, u32 insn_idx,
 	}
 }
 
+__printf(4, 5)
 static void bpf_diag_source(struct bpf_verifier_env *env, u32 insn_idx, const char *label,
 			    const char *fmt, ...)
 {
-- 
2.39.5

Re: [PATCH bpf-next] bpf: Add __printf attribute to bpf_diag_source()

[Alexei Starovoitov]

On Mon, Oct 19, 2026 at 12:59 PM Adrián García Casado <adriangarciacasado42@gmail.com> wrote:
> @@ -794,6 +794,7 @@ static void diag_print_insn_context(struct bpf_verifier_env *env, u32 insn_idx,
>  	}
>  }
>
> +__printf(4, 5)
>  static void bpf_diag_source(struct bpf_verifier_env *env, u32 insn_idx, const char *label,
>  			    const char *fmt, ...)

1. This doesn't apply to bpf-next. 
2. The warning was fixed a month ago:
commit 7f2b0b57a8d7 ("bpf: Add printf attributes").

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