bpf.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Yonghong Song <yhs@fb.com>
To: <bpf@vger.kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Andrii Nakryiko <andrii@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>, <kernel-team@fb.com>
Subject: [PATCH bpf-next v2] selftests/bpf: fix probe_user test failure with clang build kernel
Date: Tue, 28 Sep 2021 20:30:00 -0700	[thread overview]
Message-ID: <20210929033000.3711921-1-yhs@fb.com> (raw)

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:
  $ #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>
 .../selftests/bpf/prog_tests/probe_user.c     |  4 +--
 .../selftests/bpf/progs/test_probe_user.c     | 28 +++++++++++++++++--
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/probe_user.c b/tools/testing/selftests/bpf/prog_tests/probe_user.c
index 95bd12097358..52fe157e2a90 100644
--- 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"))
-	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 89b3532ccc75..8812a90da4eb 100644
--- 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 SYS_PREFIX "__x64_"
+#elif defined(__TARGET_ARCH_s390)
+#define SYS_PREFIX "__s390x_"
+#elif defined(__TARGET_ARCH_arm64)
+#define SYS_PREFIX "__arm64_"
+#define SYS_PREFIX ""
 static struct sockaddr_in old;
+SEC("kprobe/" SYS_PREFIX "sys_connect")
 int BPF_KPROBE(handle_sys_connect)
-	void *ptr = (void *)PT_REGS_PARM2(ctx);
+	struct pt_regs *real_regs;
 	struct sockaddr_in new;
+	void *ptr;
+	ptr = (void *)PT_REGS_PARM2(ctx);
+	real_regs = (struct pt_regs *)PT_REGS_PARM1(ctx);
+	bpf_probe_read_kernel(&ptr, sizeof(ptr), &PT_REGS_PARM2(real_regs));
 	bpf_probe_read_user(&old, sizeof(old), ptr);
 	__builtin_memset(&new, 0xab, sizeof(new));

             reply	other threads:[~2021-09-29  3:30 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-29  3:30 Yonghong Song [this message]
2021-09-29  6:23 ` Andrii Nakryiko

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210929033000.3711921-1-yhs@fb.com \
    --to=yhs@fb.com \
    --cc=andrii@kernel.org \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=kernel-team@fb.com \
    --subject='Re: [PATCH bpf-next v2] selftests/bpf: fix probe_user test failure with clang build kernel' \


* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).