selftests/bpf: Add test for bpf_get_branch_snapshot

This test uses bpf_get_branch_snapshot from a fexit program. The test uses
a target function (bpf_testmod_loop_test) and compares the record against
kallsyms. If there isn't enough record matching kallsyms, the test fails.

Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210910183352.3151445-4-songliubraving@fb.com

1 files changed, 39 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
index cc1cd240445d..2ed01f615d20 100644
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -743,6 +743,45 @@ int cd_flavor_subdir(const char *exec_name)
 	return chdir(flavor);
 }
 
+int trigger_module_test_read(int read_sz)
+{
+	int fd, err;
+
+	fd = open("/sys/kernel/bpf_testmod", O_RDONLY);
+	err = -errno;
+	if (!ASSERT_GE(fd, 0, "testmod_file_open"))
+		return err;
+
+	read(fd, NULL, read_sz);
+	close(fd);
+
+	return 0;
+}
+
+int trigger_module_test_write(int write_sz)
+{
+	int fd, err;
+	char *buf = malloc(write_sz);
+
+	if (!buf)
+		return -ENOMEM;
+
+	memset(buf, 'a', write_sz);
+	buf[write_sz-1] = '\0';
+
+	fd = open("/sys/kernel/bpf_testmod", O_WRONLY);
+	err = -errno;
+	if (!ASSERT_GE(fd, 0, "testmod_file_open")) {
+		free(buf);
+		return err;
+	}
+
+	write(fd, buf, write_sz);
+	close(fd);
+	free(buf);
+	return 0;
+}
+
 #define MAX_BACKTRACE_SZ 128
 void crash_handler(int signum)
 {