linux-kernel - Re: [PATCH perf/core 18/22] selftests/bpf: Add uprobe_regs

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Message-ID: <aAoz1ZBL2WahMa4m@krava>
Date: Thu, 24 Apr 2025 14:51:33 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Oleg Nesterov <oleg@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
	Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
	x86@...nel.org, Song Liu <songliubraving@...com>,
	Yonghong Song <yhs@...com>,
	John Fastabend <john.fastabend@...il.com>,
	Hao Luo <haoluo@...gle.com>, Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Alan Maguire <alan.maguire@...cle.com>,
	David Laight <David.Laight@...lab.com>,
	Thomas Weißschuh <thomas@...ch.de>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH perf/core 18/22] selftests/bpf: Add uprobe_regs_equal test

On Wed, Apr 23, 2025 at 10:46:24AM -0700, Andrii Nakryiko wrote:
> On Mon, Apr 21, 2025 at 2:48 PM Jiri Olsa <jolsa@...nel.org> wrote:
> >
> > Changing uretprobe_regs_trigger to allow the test for both
> > uprobe and uretprobe and renaming it to uprobe_regs_equal.
> >
> > We check that both uprobe and uretprobe probes (bpf programs)
> > see expected registers with few exceptions.
> >
> > Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> > ---
> >  .../selftests/bpf/prog_tests/uprobe_syscall.c | 58 ++++++++++++++-----
> >  .../selftests/bpf/progs/uprobe_syscall.c      |  4 +-
> >  2 files changed, 45 insertions(+), 17 deletions(-)
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> > index f001986981ab..6d88c5b0f6aa 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> > @@ -18,15 +18,17 @@
> >
> >  #pragma GCC diagnostic ignored "-Wattributes"
> >
> > -__naked unsigned long uretprobe_regs_trigger(void)
> > +__attribute__((aligned(16)))
> > +__nocf_check __weak __naked unsigned long uprobe_regs_trigger(void)
> >  {
> >         asm volatile (
> > -               "movq $0xdeadbeef, %rax\n"
> > +               ".byte 0x0f, 0x1f, 0x44, 0x00, 0x00     \n"
> 
> Is it me not being hardcore enough... But is anyone supposed to know
> that this is nop5? ;) maybe add /* nop5 */ comment on the side?

ok, will add the comment :)

> 
> > +               "movq $0xdeadbeef, %rax                 \n"
> 
> ret\n doesn't align newline, and uprobe_regs below don't either. So
> maybe don't align them at all here?

ok

thanks,
jirka