Messages in this thread | | | Date | Mon, 25 Jan 2021 19:19:27 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH v3] tracing: precise log info for kretprobe addr err |
| |
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/20210120131406.5a992c1e434681750a0cd5d4@kernel.org/
So I leave this to you and Masami, but perhaps you can document this check at least in the changelog?
Oleg.
| |