selftests/bpf: Fix probe_user test failure with clang build kernel

clang build kernel failed the selftest probe_user.
  $ ./test_progs -t probe_user
  $ ...
  $ test_probe_user:PASS:get_kprobe_res 0 nsec
  $ test_probe_user:FAIL:check_kprobe_res wrong kprobe res from probe read: 0.0.0.0:0
  $ #94 probe_user:FAIL

The test attached to kernel function __sys_connect(). In net/socket.c, we have
  int __sys_connect(int fd, struct sockaddr __user *uservaddr, int addrlen)
  {
        ......
  }
  ...
  SYSCALL_DEFINE3(connect, int, fd, struct sockaddr __user *, uservaddr,
                  int, addrlen)
  {
        return __sys_connect(fd, uservaddr, addrlen);
  }

The gcc compiler (8.5.0) does not inline __sys_connect() in syscall entry
function. But latest clang trunk did the inlining. So the bpf program
is not triggered.

To make the test more reliable, let us kprobe the syscall entry function
instead. Note that x86_64, arm64 and s390 have syscall wrappers and they have
to be handled specially.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210929033000.3711921-1-yhs@fb.com

diff --git a/tools/testing/selftests/bpf/prog_tests/probe_user.c b/tools/testing/selftests/bpf/prog_tests/probe_user.c
index 95bd1209735878e6968b55db6988ad0fbb5c14c1..52fe157e2a90266afbf4ddfe9896bdf13014d52c 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/probe_user.c
+++ b/tools/testing/selftests/bpf/prog_tests/probe_user.c
@@ -3,7 +3,7 @@
 
 void test_probe_user(void)
 {
-       const char *prog_name = "kprobe/__sys_connect";
+       const char *prog_name = "handle_sys_connect";
        const char *obj_file = "./test_probe_user.o";
        DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts, );
        int err, results_map_fd, sock_fd, duration = 0;
@@ -18,7 +18,7 @@ void test_probe_user(void)
        if (!ASSERT_OK_PTR(obj, "obj_open_file"))
                return;
 
-       kprobe_prog = bpf_object__find_program_by_title(obj, prog_name);
+       kprobe_prog = bpf_object__find_program_by_name(obj, prog_name);
        if (CHECK(!kprobe_prog, "find_probe",
                  "prog '%s' not found\n", prog_name))
                goto cleanup;

diff --git a/tools/testing/selftests/bpf/progs/test_probe_user.c b/tools/testing/selftests/bpf/progs/test_probe_user.c
index 89b3532ccc75e3f71a8b4a2516b044269e7248c9..8812a90da4eb87f6472fda3e82c068ab6f7eee10 100644 (file)
--- a/tools/testing/selftests/bpf/progs/test_probe_user.c
+++ b/tools/testing/selftests/bpf/progs/test_probe_user.c
@@ -8,13 +8,37 @@
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
 
+#if defined(__TARGET_ARCH_x86)
+#define SYSCALL_WRAPPER 1
+#define SYS_PREFIX "__x64_"
+#elif defined(__TARGET_ARCH_s390)
+#define SYSCALL_WRAPPER 1
+#define SYS_PREFIX "__s390x_"
+#elif defined(__TARGET_ARCH_arm64)
+#define SYSCALL_WRAPPER 1
+#define SYS_PREFIX "__arm64_"
+#else
+#define SYSCALL_WRAPPER 0
+#define SYS_PREFIX ""
+#endif
+
 static struct sockaddr_in old;
 
-SEC("kprobe/__sys_connect")
+SEC("kprobe/" SYS_PREFIX "sys_connect")
 int BPF_KPROBE(handle_sys_connect)
 {
-       void *ptr = (void *)PT_REGS_PARM2(ctx);
+#if SYSCALL_WRAPPER == 1
+       struct pt_regs *real_regs;
+#endif
        struct sockaddr_in new;
+       void *ptr;
+
+#if SYSCALL_WRAPPER == 0
+       ptr = (void *)PT_REGS_PARM2(ctx);
+#else
+       real_regs = (struct pt_regs *)PT_REGS_PARM1(ctx);
+       bpf_probe_read_kernel(&ptr, sizeof(ptr), &PT_REGS_PARM2(real_regs));
+#endif
 
        bpf_probe_read_user(&old, sizeof(old), ptr);
        __builtin_memset(&new, 0xab, sizeof(new));