On 01/26, Jianlin Lv 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
IOW, the "offset != 0" check removed by this patch is obviously wrong, right?
Agreed, but...
> --- 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 (!strchr(symbol, ':') && is_return && !(flags &
> TPARG_FL_FENTRY)) {
but why did you add the strchr(':') check instead?
I was really puzzled until I found the this email from Masami:
https://lore.kernel.org/lkml/20210120131406.5a992c1e434681750a0cd...@kernel.org/
So I leave this to you and Masami, but perhaps you can document this check at
least in the changelog?
Oleg.
