tools/nolibc: Implement gettid()

Allow test programs to determine their thread ID.
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/include/nolibc/nolibc.h

@@ -1571,6 +1571,12 @@ pid_t sys_getpid(void)
 	return my_syscall0(__NR_getpid);
 }
 
+static __attribute__((unused))
+pid_t sys_gettid(void)
+{
+	return my_syscall0(__NR_gettid);
+}
+
 static __attribute__((unused))
 int sys_gettimeofday(struct timeval *tv, struct timezone *tz)
 {
@@ -2029,6 +2035,18 @@ pid_t getpid(void)
 	return ret;
 }
 
+static __attribute__((unused))
+pid_t gettid(void)
+{
+	pid_t ret = sys_gettid();
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
 static __attribute__((unused))
 int gettimeofday(struct timeval *tv, struct timezone *tz)
 {