Re: [PATCHv4 bpf-next 5/7] selftests/bpf: Add uretprobe syscall call from user space test

[Andrii Nakryiko]

On Thu, May 2, 2024 at 5:24 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
>
> Adding test to verify that when called from outside of the
> trampoline provided by kernel, the uretprobe syscall will cause
> calling process to receive SIGILL signal and the attached bpf
> program is not executed.
>
> Reviewed-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
>  .../selftests/bpf/prog_tests/uprobe_syscall.c | 95 +++++++++++++++++++
>  .../bpf/progs/uprobe_syscall_executed.c       | 17 ++++
>  2 files changed, 112 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/progs/uprobe_syscall_executed.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> index 1a50cd35205d..c6fdb8c59ea3 100644
> --- a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> +++ b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> @@ -7,7 +7,10 @@
>  #include <unistd.h>
>  #include <asm/ptrace.h>
>  #include <linux/compiler.h>
> +#include <linux/stringify.h>
> +#include <sys/wait.h>
>  #include "uprobe_syscall.skel.h"
> +#include "uprobe_syscall_executed.skel.h"
>
>  __naked unsigned long uretprobe_regs_trigger(void)
>  {
> @@ -209,6 +212,91 @@ static void test_uretprobe_regs_change(void)
>         }
>  }
>
> +#ifndef __NR_uretprobe
> +#define __NR_uretprobe 462
> +#endif
> +
> +__naked unsigned long uretprobe_syscall_call_1(void)
> +{
> +       /*
> +        * Pretend we are uretprobe trampoline to trigger the return
> +        * probe invocation in order to verify we get SIGILL.
> +        */
> +       asm volatile (
> +               "pushq %rax\n"
> +               "pushq %rcx\n"
> +               "pushq %r11\n"
> +               "movq $" __stringify(__NR_uretprobe) ", %rax\n"
> +               "syscall\n"
> +               "popq %r11\n"
> +               "popq %rcx\n"
> +               "retq\n"
> +       );
> +}
> +
> +__naked unsigned long uretprobe_syscall_call(void)
> +{
> +       asm volatile (
> +               "call uretprobe_syscall_call_1\n"
> +               "retq\n"
> +       );
> +}
> +
> +static void test_uretprobe_syscall_call(void)
> +{
> +       LIBBPF_OPTS(bpf_uprobe_multi_opts, opts,
> +               .retprobe = true,
> +       );
> +       struct uprobe_syscall_executed *skel;
> +       int pid, status, err, go[2], c;
> +
> +       if (pipe(go))
> +               return;

very unlikely to fail, but still, ASSERT_OK() would be in order here

But regardless:

Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>

[...]