tools/nolibc: add getuid() and geteuid()

This can be useful to avoid attempting some privileged operations,
starting from the nolibc-test tool that gets two failures when not
privileged.

We call getuid32() and geteuid32() when they are defined, and fall
back to getuid() and geteuid() otherwise.

Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/include/nolibc/sys.h

@@ -410,6 +410,27 @@ int getdents64(int fd, struct linux_dirent64 *dirp, int count)
 }
 
 
+/*
+ * uid_t geteuid(void);
+ */
+
+static __attribute__((unused))
+uid_t sys_geteuid(void)
+{
+#ifdef __NR_geteuid32
+	return my_syscall0(__NR_geteuid32);
+#else
+	return my_syscall0(__NR_geteuid);
+#endif
+}
+
+static __attribute__((unused))
+uid_t geteuid(void)
+{
+	return sys_geteuid();
+}
+
+
 /*
  * pid_t getpgid(pid_t pid);
  */
@@ -544,6 +565,27 @@ int gettimeofday(struct timeval *tv, struct timezone *tz)
 }
 
 
+/*
+ * uid_t getuid(void);
+ */
+
+static __attribute__((unused))
+uid_t sys_getuid(void)
+{
+#ifdef __NR_getuid32
+	return my_syscall0(__NR_getuid32);
+#else
+	return my_syscall0(__NR_getuid);
+#endif
+}
+
+static __attribute__((unused))
+uid_t getuid(void)
+{
+	return sys_getuid();
+}
+
+
 /*
  * int ioctl(int fd, unsigned long req, void *value);
  */