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

From: Hengqi Chen <hengqi.chen@gmail.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: bpf <bpf@vger.kernel.org>, Andrii Nakryiko <andrii@kernel.org>
Subject: Re: [PATCH bpf-next 2/2] selftests/bpf: Test BPF_KPROBE_SYSCALL/BPF_KRETPROBE_SYSCALL macros
Date: Thu, 23 Dec 2021 20:16:01 +0800	[thread overview]
Message-ID: <77103ff7-5994-2ab4-a069-02eb5a57c44f@gmail.com> (raw)
In-Reply-To: <CAEf4BzZ+UHAoAVwgjafAcfZa=c7cSLiLUY8OvpfKk9N4gO7zYQ@mail.gmail.com>

On 2021/12/22 8:37 AM, Andrii Nakryiko wrote:
> 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.
> 

I just followed some existing selftests, didn't realize SYS_PREFIX.
Will update to use SYS_PREFIX.

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

OK, will do.

>> +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