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From:   Jianlin Lv <Jianlin.Lv@arm.com>
To:     Masami Hiramatsu <mhiramat@kernel.org>
CC:     Steven Rostedt <rostedt@goodmis.org>,
        Oleg Nesterov <oleg@redhat.com>,
        Ingo Molnar <mingo@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] tracing/kprobe: Fix to support kretprobe events on
 unloaded modules
Thread-Topic: [PATCH] tracing/kprobe: Fix to support kretprobe events on
 unloaded modules
Thread-Index: AQHW9MJs+vYjq8+NoEaLklcIBcQCxqo8DlQAgAAb34CAAg1+MIAAaKwAgADKnoA=
Date:   Sat, 30 Jan 2021 02:07:13 +0000
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> -----Original Message-----
> From: Masami Hiramatsu <mhiramat@kernel.org>
> Sent: Friday, January 29, 2021 9:45 PM
> To: Jianlin Lv <Jianlin.Lv@arm.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>; Oleg Nesterov
> <oleg@redhat.com>; Ingo Molnar <mingo@redhat.com>; linux-
> kernel@vger.kernel.org
> Subject: Re: [PATCH] tracing/kprobe: Fix to support kretprobe events on
> unloaded modules
>
> Hi Jianlin,
>
> On Fri, 29 Jan 2021 07:45:32 +0000
> Jianlin Lv <Jianlin.Lv@arm.com> wrote:
> >
> >
> > I have verified this patch on server and it solves the kretprobe issue
> > on unloaded modules very well.
> >
> > One comments is this patch did not cover the issue I reported before,
> > https://lore.kernel.org/lkml/20210127151507.4185234-1-Jianlin.Lv@arm.c
> > om/ if echo wrong function symbol to tracefs, error_log show as :
> >
> > # echo 'r:myprobe ERROR_SYMBOL_XXX ret=3D%x0' >> kprobe_events # cat
> > error_log
> > [   87.746191] trace_kprobe: error: Invalid probed address or symbol
> >   Command: r:myprobe ERROR_SYMBOL_XXX ret=3D%x0
>
> This is the correct error message because the symbol is not exist, a bad
> symbol.
>
> Thank you,
>

Yes, it would be nice if errors could be detected before registering Kprobe=
.

Of course, this patch is looks good for me.

Jianlin

> >
> > Based on the current patch,  The following changes will make the error
> > log more accurate.
> >
> > @@ -828,9 +828,10 @@
> > static int trace_kprobe_create(int argc, const char *argv[]) if
> > (is_return) flags |=3D TPARG_FL_RETURN;
> > -    if (kprobe_on_func_entry(NULL, symbol, offset))
> > +    if (!kprobe_on_func_entry(NULL, symbol, offset))
> >         flags |=3D TPARG_FL_FENTRY;
> > -    if (offset && is_return && !(flags & TPARG_FL_FENTRY)) {
> > +    /* Check whether symbol is really bad or from a module */
> > +    if (!strchr(symbol, ':') && is_return && !(flags &
> > + TPARG_FL_FENTRY)) {
> >         trace_probe_log_err(0, BAD_RETPROBE);
> >         goto parse_error;
> >
> > If you don`t mind, I can send v5 of my patch after this patch be merged=
.
> >
> > Jianlin
> >
> >
> > IMPORTANT NOTICE: The contents of this email and any attachments are
> confidential and may also be privileged. If you are not the intended reci=
pient,
> please notify the sender immediately and do not disclose the contents to =
any
> other person, use it for any purpose, or store or copy the information in=
 any
> medium. Thank you.
>
>
> --
> Masami Hiramatsu <mhiramat@kernel.org>
IMPORTANT NOTICE: The contents of this email and any attachments are confid=
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