[PATCH v4] selftests/landlock:Fix two build issues

[Hu Yadi]

From: "Hu.Yadi" <hu.yadi@xxxxxxx>

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,
         ^~~~~~~

Fixes: 04f9070e99a4 ("selftests/landlock: Add tests for pseudo filesystems")
Fixes: a549d055a22e ("selftests/landlock: Add network tests")

this patch is to fix them

Signed-off-by: Hu.Yadi <hu.yadi@xxxxxxx>
Suggested-by: Jiao <jiaoxupo@xxxxxxx>
Reviewed-by: Berlin <berlin@xxxxxxx>
---
Changes v4 -> v3:
  fix gettid error from kernel test robot
  https://lore.kernel.org/oe-kbuild-all/202401151147.T1s11iHJ-lkp@xxxxxxxxx/
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 | 7 ++++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

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..d50f2920ed82 100644
--- a/tools/testing/selftests/landlock/net_test.c
+++ b/tools/testing/selftests/landlock/net_test.c
@@ -21,6 +21,11 @@

 #include "common.h"

+static pid_t landlock_gettid(void)
+{
+        return syscall(__NR_gettid);
+}
+
 const short sock_port_start = (1 << 10);

 static const char loopback_ipv4[] = "127.0.0.1";
@@ -88,7 +93,7 @@ static int set_service(struct service_fixture *const srv,
 	case AF_UNIX:
 		srv->unix_addr.sun_family = prot.domain;
 		sprintf(srv->unix_addr.sun_path,
-			"_selftests-landlock-net-tid%d-index%d", gettid(),
+			"_selftests-landlock-net-tid%d-index%d", landlock_gettid(),
 			index);
 		srv->unix_addr_len = SUN_LEN(&srv->unix_addr);
 		srv->unix_addr.sun_path[0] = '\0';
--
2.23.0