Re: [PATCH] tracing: probes: error if BTF is required but unavailable

[Steven Rostedt <rostedt@goodmis.org>]

On Wed, 14 Oct 2026 10:37:40 +0200
Martin Kaiser <martin@kaiser.cx> wrote:

> traceprobe_expand_meta_args expands probe arguments based on BTF info.
> 
> Return an error if we have arguments that need expanding but BTF is not
> supported.
> 
> The params variable is now unused, it can be removed.
> 
> Fixes: d157d7694460 ("tracing/probes: Support BTF field access from $retval")

I agree with the change but I don't think it needs a fixes tag. It
currently errors out with -EINVAL if BTF is not supported. Your change
updates it to -ENOTSUPP. But this is a cleanup and not a fix.

~# cat error_log
trace_fprobe: error: BTF is not available or not supported
  Command: f vfs_read $arg*
                      ^
But other than that.

Reviewed-by: Steven Rostedt <rostedt@goodmis.org>

-- Steve


> Signed-off-by: Martin Kaiser <martin@kaiser.cx>
> ---
>  kernel/trace/trace_probe.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> index cfb710095f65..516c439932a0 100644
> --- a/kernel/trace/trace_probe.c
> +++ b/kernel/trace/trace_probe.c
> @@ -2287,7 +2287,6 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[],
>  					 int *new_argc, char *buf, int bufsize,
>  					 struct traceprobe_parse_context *ctx)
>  {
> -	const struct btf_param *params = NULL;
>  	int i, j, n, used, ret, args_idx = -1;
>  	const char **new_argv __free(kfree) = NULL;
>  
> @@ -2305,7 +2304,7 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[],
>  		if (args_idx != -1) {
>  			/* $arg* requires BTF info */
>  			trace_probe_log_err(0, NOSUP_BTFARG);
> -			return (const char **)params;
> +			return ERR_PTR(-EOPNOTSUPP);
>  		}
>  		*new_argc = argc;
>  		return NULL;