Re: [PATCH bpf-next 10/13] selftests/bpf: Add uprobe/usdt optimized test

[Andrii Nakryiko]

On Wed, Dec 11, 2024 at 5:35 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
>
> Adding tests for optimized uprobe/usdt probes.
>
> Checking that we get expected trampoline and attached bpf programs
> get executed properly.
>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
>  .../selftests/bpf/prog_tests/uprobe_syscall.c | 203 ++++++++++++++++++
>  .../selftests/bpf/progs/uprobe_optimized.c    |  29 +++
>  2 files changed, 232 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/progs/uprobe_optimized.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> index c397336fe1ed..1dbc26a1130c 100644
> --- a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> +++ b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> @@ -14,6 +14,8 @@
>  #include <asm/prctl.h>
>  #include "uprobe_syscall.skel.h"
>  #include "uprobe_syscall_executed.skel.h"
> +#include "uprobe_optimized.skel.h"
> +#include "sdt.h"
>
>  __naked unsigned long uretprobe_regs_trigger(void)
>  {
> @@ -350,6 +352,186 @@ static void test_uretprobe_shadow_stack(void)
>
>         ARCH_PRCTL(ARCH_SHSTK_DISABLE, ARCH_SHSTK_SHSTK);
>  }
> +
> +#define TRAMP "[uprobes-trampoline]"
> +
> +static unsigned char nop5[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
> +
> +noinline void uprobe_test(void)
> +{
> +       asm volatile ("                                 \n"
> +               ".global uprobe_test_nop5               \n"
> +               ".type uprobe_test_nop5, STT_FUNC       \n"
> +               "uprobe_test_nop5:                      \n"
> +               ".byte 0x0f, 0x1f, 0x44, 0x00, 0x00     \n"
> +       );
> +}
> +
> +extern u8 uprobe_test_nop5[];
> +
> +noinline void usdt_test(void)
> +{
> +       STAP_PROBE(optimized_uprobe, usdt);
> +}
> +
> +static void *find_nop5(void *fn)
> +{
> +       int i;
> +
> +       for (i = 0; i < 10; i++) {
> +               if (!memcmp(nop5, fn + i, 5))
> +                       return fn + i;
> +       }
> +       return NULL;
> +}
> +
> +static int find_uprobes_trampoline(void **start, void **end)
> +{
> +       char line[128];
> +       int ret = -1;
> +       FILE *maps;
> +
> +       maps = fopen("/proc/self/maps", "r");
> +       if (!maps) {
> +               fprintf(stderr, "cannot open maps\n");
> +               return -1;
> +       }
> +
> +       while (fgets(line, sizeof(line), maps)) {
> +               int m = -1;
> +
> +               /* We care only about private r-x mappings. */
> +               if (sscanf(line, "%p-%p r-xp %*x %*x:%*x %*u %n", start, end, &m) != 2)
> +                       continue;
> +               if (m < 0)
> +                       continue;
> +               if (!strncmp(&line[m], TRAMP, sizeof(TRAMP)-1)) {
> +                       ret = 0;
> +                       break;
> +               }
> +       }

you could have used PROCMAP_QUERY ;)

> +
> +       fclose(maps);
> +       return ret;
> +}
> +

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