Re: [PATCH] selftests/ftrace: skip gcov symbols when picking a function to probe

[Shuah Khan]

On 9/26/26 06:31, Masami Hiramatsu (Google) wrote:
> On Fri, 25 Sep 2026 16:35:41 +0300
> Eva Kurchatova <eva.kurchatova@xxxxxxxxxxxxx> wrote:
>
> > kprobe_eventname.tc takes the last kallsyms entry whose name ends in
> > vfs_read and puts a probe on it. On a kernel built with
> > CONFIG_GCOV_PROFILE_ALL=y the counter symbol gcc emits for the function
> > sorts after it:
> >
> >    ffffffff819bd1e0 T vfs_read
> >    ffffffff845013e0 t __gcov_.vfs_read
> >
> > so the test picks __gcov_.vfs_read, which is not a function entry, and
> > the write fails:
> >
> >    kprobe_eventname.tc: line 10: echo: write error: Invalid argument
> >
> > Leave those symbols out of the choice. The test then picks vfs_read and
> > passes; without a coverage build nothing changes, as no such symbol
> > exists there.
> >
> > This is the same class of problem as commit 23a4b108accc
> > ("tracing/selftests: Fix kprobe event name test for .isra. functions"),
> > where a compiler-generated symbol was picked instead of a real function.
>
> Oops, good catch! This looks good to me.
>
> Acked-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
>
> Shuah, can you pick this fix via your selftest tree? I think this is a
> kind of selftest fix/improvement.
>
> Thanks,
>
> > Signed-off-by: Eva Kurchatova <eva.kurchatova@xxxxxxxxxxxxx>

Applied to linux-kselftest next branch for the next merge window.

thanks,
-- Shuah