selftests/bpf: Test verifier log for global percpu data

Add two tests to verify the verifier log
"R%d points to percpu_array map which cannot be used as const string\n".

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Link: https://lore.kernel.org/bpf/20260813152324.97937-10-leon.hwang@linux.dev

2 files changed, 29 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/global_data_init.c b/tools/testing/selftests/bpf/prog_tests/global_data_init.c
index 9688b417a90b..d308ca3b3045 100644
--- a/tools/testing/selftests/bpf/prog_tests/global_data_init.c
+++ b/tools/testing/selftests/bpf/prog_tests/global_data_init.c
@@ -322,6 +322,11 @@ static void test_global_percpu_data_rdonly_direct_write(void)
 	close(map_fd);
 }
 
+static void test_global_percpu_data_verifier_log(void)
+{
+	RUN_TESTS(test_global_percpu_data);
+}
+
 void test_global_percpu_data(void)
 {
 	if (!feat_supported(NULL, FEAT_PERCPU_DATA)) {
@@ -337,4 +342,5 @@ void test_global_percpu_data(void)
 		test_global_percpu_data_rdonly_direct_read();
 	if (test__start_subtest("rdonly_direct_write"))
 		test_global_percpu_data_rdonly_direct_write();
+	test_global_percpu_data_verifier_log();
 }
diff --git a/tools/testing/selftests/bpf/progs/test_global_percpu_data.c b/tools/testing/selftests/bpf/progs/test_global_percpu_data.c
index 416841cd3569..d086e9417f9f 100644
--- a/tools/testing/selftests/bpf/progs/test_global_percpu_data.c
+++ b/tools/testing/selftests/bpf/progs/test_global_percpu_data.c
@@ -38,4 +38,27 @@ int update_percpu_data(void *ctx)
 	return 0;
 }
 
+static const char fmt[] SEC(".percpu.fmt") = "data %d\n";
+
+SEC("?kprobe")
+__failure __msg("R{{[0-9]+}} points to percpu_array map which cannot be used as const string")
+int verifier_strncmp(void *ctx)
+{
+	return bpf_strncmp("test", 5, fmt);
+}
+
+SEC("?kprobe")
+__failure __msg("R{{[0-9]+}} points to percpu_array map which cannot be used as const string")
+int verifier_snprintf(void *ctx)
+{
+	u64 args[] = { data };
+	char buf[128];
+	int len;
+
+	len = bpf_snprintf(buf, sizeof(buf), fmt, args, sizeof(args));
+	if (len > 0)
+		bpf_printk("snprintf: %s\n", buf);
+	return 0;
+}
+
 char _license[] SEC("license") = "GPL";