linux-kernel - Re: [PATCH] tracing: precise log info for kretprobe addr err

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Date:   Tue, 19 Jan 2021 10:41:06 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Jianlin Lv <Jianlin.Lv@....com>, mingo@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing: precise log info for kretprobe addr err

Masami,

Looks fine to me. What do you think?

-- Steve


On Tue, 19 Jan 2021 23:10:14 +0800
Jianlin Lv <Jianlin.Lv@....com> wrote:

> When trying to create kretprobe with the wrong function symbol in tracefs;
> The error is triggered in the register_trace_kprobe() and recorded as
> FAIL_REG_PROBE issue,
> 
> Example:
>   $ cd /sys/kernel/debug/tracing
>   $ echo 'r:myprobe ERROR_SYMBOL_XXX ret=%x0' >> kprobe_events
>     bash: echo: write error: Invalid argument
>   $ cat error_log
>     [142797.347877] trace_kprobe: error: Failed to register probe event
>     Command: r:myprobe ERROR_SYMBOL_XXX ret=%x0
>                        ^
> 
> This error can be detected in the parameter parsing stage, the effect of
> applying this patch is as follows:
> 
>   $ echo 'r:myprobe ERROR_SYMBOL_XXX ret=%x0' >> kprobe_events
>     bash: echo: write error: Invalid argument
>   $ cat error_log
>     [415.89]trace_kprobe: error: Retprobe address must be an function entry
>     Command: r:myprobe ERROR_SYMBOL_XXX ret=%x0
>                        ^
> 
> Signed-off-by: Jianlin Lv <Jianlin.Lv@....com>
> ---
>  kernel/trace/trace_kprobe.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index e6fba1798771..3dfd1b6711a3 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -830,7 +830,7 @@ static int trace_kprobe_create(int argc, const char *argv[])
>  			flags |= TPARG_FL_RETURN;
>  		if (kprobe_on_func_entry(NULL, symbol, offset))
>  			flags |= TPARG_FL_FENTRY;
> -		if (offset && is_return && !(flags & TPARG_FL_FENTRY)) {
> +		if (is_return && !(flags & TPARG_FL_FENTRY)) {
>  			trace_probe_log_err(0, BAD_RETPROBE);
>  			goto parse_error;
>  		}