[PATCH v3] selftests/landlock:Fix two build issues

[Hu Yadi]

From: "Hu.Yadi" <hu.yadi at h3c.com>

Two issues comes up while building selftest/landlock on my side
(gcc 7.3/glibc-2.28/kernel-4.19)

the first one is as to gettid

net_test.c: In function ‘set_service’:
net_test.c:91:45: warning: implicit declaration of function ‘gettid’; [-Wimplicit-function-declaration]
    "_selftests-landlock-net-tid%d-index%d", gettid(),
                                             ^~~~~~
                                             getgid
net_test.c:(.text+0x4e0): undefined reference to `gettid'

the second is compiler error
gcc -Wall -O2 -isystem   fs_test.c -lcap -o selftests/landlock/fs_test
fs_test.c:4575:9: error: initializer element is not constant
  .mnt = mnt_tmp,
         ^~~~~~~

this patch is to fix them

Signed-off-by: Hu.Yadi <hu.yadi at h3c.com>
Suggested-by: Jiao <jiaoxupo at h3c.com>
Reviewed-by: Berlin <berlin at h3c.com>
---
Changes v3 -> v2:
 - add helper of gettid instead of __NR_gettid
 - add gcc/glibc version info in comments
Changes v1 -> v2:
 - fix whitespace error
 - replace SYS_gettid with _NR_gettid

 tools/testing/selftests/landlock/fs_test.c  | 5 ++++-
 tools/testing/selftests/landlock/net_test.c | 9 +++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 18e1f86a6234..a992cf7c0ad1 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -4572,7 +4572,10 @@ FIXTURE_VARIANT(layout3_fs)
 /* clang-format off */
 FIXTURE_VARIANT_ADD(layout3_fs, tmpfs) {
 	/* clang-format on */
-	.mnt = mnt_tmp,
+	.mnt = {
+		.type = "tmpfs",
+		.data = "size=4m,mode=700",
+	},
 	.file_path = file1_s1d1,
 };
 
diff --git a/tools/testing/selftests/landlock/net_test.c b/tools/testing/selftests/landlock/net_test.c
index 929e21c4db05..12a6744568e2 100644
--- a/tools/testing/selftests/landlock/net_test.c
+++ b/tools/testing/selftests/landlock/net_test.c
@@ -21,6 +21,15 @@
 
 #include "common.h"
 
+#ifndef gettid
+static pid_t gettid(void)
+{
+        return syscall(__NR_gettid);
+}
+
+#endif
+
+
 const short sock_port_start = (1 << 10);
 
 static const char loopback_ipv4[] = "127.0.0.1";
-- 
2.23.0