Re: [PATCH bpf-next 2/2] selftests/bpf: Test BPF_KPROBE_SYSCALL/BPF_KRETPROBE_SYSCALL macros

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Mon, Dec 20, 2021 at 9:54 PM Hengqi Chen <hengqi.chen@gmail.com> wrote:
>
> Add tests for the newly added BPF_KPROBE_SYSCALL/BPF_KRETPROBE_SYSCALL macros.
>
> Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> ---
>  .../selftests/bpf/prog_tests/kprobe_syscall.c | 40 ++++++++++++++++++
>  .../selftests/bpf/progs/test_kprobe_syscall.c | 41 +++++++++++++++++++
>  2 files changed, 81 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/kprobe_syscall.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_kprobe_syscall.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/kprobe_syscall.c b/tools/testing/selftests/bpf/prog_tests/kprobe_syscall.c
> new file mode 100644
> index 000000000000..a1fad70bbb69
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/kprobe_syscall.c
> @@ -0,0 +1,40 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2021 Hengqi Chen */
> +
> +#include <test_progs.h>
> +#include <sys/types.h>
> +#include <sys/socket.h>
> +#include "test_kprobe_syscall.skel.h"
> +
> +void test_kprobe_syscall(void)
> +{
> +       struct test_kprobe_syscall *skel;
> +       int err, fd = 0;
> +
> +       skel = test_kprobe_syscall__open();
> +       if (!ASSERT_OK_PTR(skel, "could not open BPF object"))
> +               return;
> +
> +       skel->rodata->my_pid = getpid();
> +
> +       err = test_kprobe_syscall__load(skel);
> +       if (!ASSERT_OK(err, "could not load BPF object"))
> +               goto cleanup;
> +
> +       err = test_kprobe_syscall__attach(skel);
> +       if (!ASSERT_OK(err, "could not attach BPF object"))
> +               goto cleanup;
> +
> +       fd = socket(AF_UNIX, SOCK_STREAM, 0);
> +
> +       ASSERT_GT(fd, 0, "socket failed");
> +       ASSERT_EQ(skel->bss->domain, AF_UNIX, "BPF_KPROBE_SYSCALL failed");
> +       ASSERT_EQ(skel->bss->type, SOCK_STREAM, "BPF_KPROBE_SYSCALL failed");
> +       ASSERT_EQ(skel->bss->protocol, 0, "BPF_KPROBE_SYSCALL failed");
> +       ASSERT_EQ(skel->bss->fd, fd, "BPF_KRETPROBE_SYSCALL failed");
> +
> +cleanup:
> +       if (fd)
> +               close(fd);
> +       test_kprobe_syscall__destroy(skel);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/test_kprobe_syscall.c b/tools/testing/selftests/bpf/progs/test_kprobe_syscall.c
> new file mode 100644
> index 000000000000..ecef9d19007c
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_kprobe_syscall.c
> @@ -0,0 +1,41 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2021 Hengqi Chen */
> +
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +#include <bpf/bpf_core_read.h>
> +
> +const volatile pid_t my_pid = 0;
> +int domain = 0;
> +int type = 0;
> +int protocol = 0;
> +int fd = 0;
> +
> +SEC("kprobe/__x64_sys_socket")
> +int BPF_KPROBE_SYSCALL(socket_enter, int d, int t, int p)
> +{
> +       pid_t pid = bpf_get_current_pid_tgid() >> 32;
> +
> +       if (pid != my_pid)
> +               return 0;
> +
> +       domain = d;
> +       type = t;
> +       protocol = p;
> +       return 0;
> +}
> +
> +SEC("kretprobe/__x64_sys_socket")

oh, please also use SYS_PREFIX instead of hard-coding __x64. This is
very x86-64-specific and we have other architectures tested by
selftests, so this makes it automatically fail on non-x86_64.

If you get a chance, try also cleaning up other __x64_ uses in the
selftests as a separate patch. Thank you!

> +int BPF_KRETPROBE_SYSCALL(socket_exit, int ret)
> +{
> +       pid_t pid = bpf_get_current_pid_tgid() >> 32;
> +
> +       if (pid != my_pid)
> +               return 0;
> +
> +       fd = ret;
> +       return 0;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> --
> 2.30.2