selftests/bpf: More open-coded gettid syscall cleanup

Commit 0e2fb01 ("selftests/bpf: Clean up open-coded gettid syscall
invocations") addressed the issue that older libc may not have a gettid()
function call wrapper for the associated syscall.

A few more instances have crept into tests, use sys_gettid() instead, and
poison raw gettid() usage to avoid future issues.

Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20250911163056.543071-1-alan.maguire@oracle.com

Author: alan-maguire

tools/testing/selftests/bpf/bpf_util.h

@@ -67,6 +67,9 @@ static inline void bpf_strlcpy(char *dst, const char *src, size_t sz)
 #define sys_gettid() syscall(SYS_gettid)
 #endif
 
+/* and poison usage to ensure it does not creep back in. */
+#pragma GCC poison gettid
+
 #ifndef ENOTSUPP
 #define ENOTSUPP 524
 #endif

tools/testing/selftests/bpf/network_helpers.c

@@ -457,7 +457,7 @@ int append_tid(char *str, size_t sz)
 	if (end + 8 > sz)
 		return -1;
 
-	sprintf(&str[end], "%07d", gettid());
+	sprintf(&str[end], "%07ld", sys_gettid());
 	str[end + 7] = '\0';
 
 	return 0;

tools/testing/selftests/bpf/prog_tests/cgroup_xattr.c

@@ -44,7 +44,7 @@ static void test_read_cgroup_xattr(void)
 	if (!ASSERT_OK_PTR(skel, "read_cgroupfs_xattr__open_and_load"))
 		goto out;
 
-	skel->bss->target_pid = gettid();
+	skel->bss->target_pid = sys_gettid();
 
 	if (!ASSERT_OK(read_cgroupfs_xattr__attach(skel), "read_cgroupfs_xattr__attach"))
 		goto out;

tools/testing/selftests/bpf/prog_tests/kernel_flag.c

@@ -16,7 +16,7 @@ void test_kernel_flag(void)
 	if (!ASSERT_OK_PTR(lsm_skel, "lsm_skel"))
 		return;
 
-	lsm_skel->bss->monitored_tid = gettid();
+	lsm_skel->bss->monitored_tid = sys_gettid();
 
 	ret = test_kernel_flag__attach(lsm_skel);
 	if (!ASSERT_OK(ret, "test_kernel_flag__attach"))

tools/testing/selftests/bpf/prog_tests/task_local_data.h

@@ -158,7 +158,7 @@ static int __tld_init_data_p(int map_fd)
 	void *data_alloc = NULL;
 	int err, tid_fd = -1;
 
-	tid_fd = syscall(SYS_pidfd_open, gettid(), O_EXCL);
+	tid_fd = syscall(SYS_pidfd_open, sys_gettid(), O_EXCL);
 	if (tid_fd < 0) {
 		err = -errno;
 		goto out;

tools/testing/selftests/bpf/prog_tests/test_task_local_data.c

@@ -63,7 +63,7 @@ void *test_task_local_data_basic_thread(void *arg)
 	if (!ASSERT_OK_PTR(value2, "tld_get_data"))
 		goto out;
 
-	tid = gettid();
+	tid = sys_gettid();
 
 	*value0 = tid + 0;
 	*value1 = tid + 1;