Re: [PATCH Linux-next] perf test: Fix test case perf trace BTF general tests

Namhyung Kim
2025-11-20T00:52:31Z

On Wed, Nov 19, 2025 at 12:59:03PM -0500, Steven Rostedt wrote:
> On Tue, 18 Nov 2025 20:36:46 -0800
> Namhyung Kim <namhyung@kernel.org> wrote:
>
> > > Really? It still uses libtraceevent right? I made sure that this didn't
> > > break trace-cmd and thought that perf would work too.
> >
> > It doesn't completely break perf trace but added new parameter for the
> > write syscall at the end. IIUC perf trace iterates the format fields
> > after __syscall_nr and take them all as syscall parameters.
>
> Is this a regression? Or can perf be fixed?
>
> I just ran it and I have this:
>
> 542.337 ( 0.131 ms): sshd-session/1189 write(fd: 7<socket:[9749]>, buf: , count: 268) = 268
>
> I haven't tried it without the patches. Does it usually show what "buf" is?
> Now with the reading of user space, it can show the content too!

Yep, it reads the content using BPF. This is on my 6.16 kernel.

$ sudo perf trace -e write -- /bin/echo hello
hello
0.000 ( 0.014 ms): echo/61922 write(fd: 1, buf: hello\10, count: 6) = 6

Thanks,
Namhyung