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

[Shuah Khan <skhan@linuxfoundation.org>]

On 9/26/26 06:31, Masami Hiramatsu (Google) wrote:
> On Fri, 25 Sep 2026 16:35:41 +0300
> Eva Kurchatova <eva.kurchatova@virtuozzo.com> 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@kernel.org>
> 
> 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@virtuozzo.com>

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

thanks,
-- Shuah