Re: [PATCHv4 13/13] selftests/bpf: Add tests for forked/cloned optimized uprobes

[Jiri Olsa <olsajiri@gmail.com>]

On Thu, May 28, 2026 at 03:00:05PM +0200, Jakub Sitnicki wrote:
> On Tue, May 26, 2026 at 10:58 PM +02, Jiri Olsa wrote:
> > Adding tests for forked/cloned optimized uprobes and make
> > sure the child can properly execute optimized probe for
> > both fork (dups mm) and clone with CLONE_VM.
> >
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >  .../selftests/bpf/prog_tests/uprobe_syscall.c | 88 +++++++++++++++++++
> >  1 file changed, 88 insertions(+)
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> > index efff0c515184..033d32b4cc27 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> > @@ -4,6 +4,8 @@
> >  
> >  #ifdef __x86_64__
> >  
> > +#define _GNU_SOURCE
> > +#include <sched.h>
> >  #include <unistd.h>
> >  #include <asm/ptrace.h>
> >  #include <linux/compiler.h>
> > @@ -936,6 +938,88 @@ static void test_uprobe_error(void)
> >  	ASSERT_EQ(errno, EPROTO, "errno");
> >  }
> >  
> > +__attribute__((aligned(16)))
> > +__nocf_check __weak __naked void uprobe_fork_test(void)
> > +{
> > +	asm volatile (
> > +		".byte 0x66, 0x2e, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00\n" /* nop10 */
> > +		"ret\n"
> > +	);
> > +}
> > +
> > +static int child_func(void *arg)
> 
> Nit: Could annotate with noreturn:
> 
> #include <stdnoreturn.h>
> 
> /* ... */
> 
> static noreturn int child_func(void *arg)

yep, will change, thanks

jirka

> 
> > +{
> > +	struct uprobe_syscall_executed *skel = arg;
> > +
> > +	/* Make sure the child's probe is still there and optimized.. */
> > +	if (memcmp(uprobe_fork_test, lea_rsp, sizeof(lea_rsp)))
> > +		_exit(1);
> > +
> > +	skel->bss->pid = getpid();
> > +
> > +	/* .. and it executes properly. */
> > +	uprobe_fork_test();
> > +
> > +	if (skel->bss->executed != 3)
> > +		_exit(2);
> > +
> > +	_exit(0);
> > +}
> 
> [...]
> 
> Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>