tools/nolibc/errno: extract errno.h from sys.h

This allows us to provide a minimal errno.h to ease porting applications
that use it.
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/include/nolibc/errno.h

+/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
+/*
+ * Minimal errno definitions for NOLIBC
+ * Copyright (C) 2017-2022 Willy Tarreau <w@1wt.eu>
+ */
+
+#ifndef _NOLIBC_ERRNO_H
+#define _NOLIBC_ERRNO_H
+
+#include <asm/errno.h>
+
+/* this way it will be removed if unused */
+static int errno;
+
+#ifndef NOLIBC_IGNORE_ERRNO
+#define SET_ERRNO(v) do { errno = (v); } while (0)
+#else
+#define SET_ERRNO(v) do { } while (0)
+#endif
+
+
+/* errno codes all ensure that they will not conflict with a valid pointer
+ * because they all correspond to the highest addressable memory page.
+ */
+#define MAX_ERRNO 4095
+
+#endif /* _NOLIBC_ERRNO_H */

tools/include/nolibc/stdio.h

@@ -11,6 +11,7 @@
 
 #include "std.h"
 #include "arch.h"
+#include "errno.h"
 #include "types.h"
 #include "sys.h"
 #include "stdlib.h"

tools/include/nolibc/sys.h

@@ -14,29 +14,14 @@
 #include <asm/unistd.h>
 #include <asm/signal.h>  // for SIGCHLD
 #include <asm/ioctls.h>
-#include <asm/errno.h>
 #include <linux/fs.h>
 #include <linux/loop.h>
 #include <linux/time.h>
 
 #include "arch.h"
+#include "errno.h"
 #include "types.h"
 
-/* this way it will be removed if unused */
-static int errno;
-
-#ifndef NOLIBC_IGNORE_ERRNO
-#define SET_ERRNO(v) do { errno = (v); } while (0)
-#else
-#define SET_ERRNO(v) do { } while (0)
-#endif
-
-
-/* errno codes all ensure that they will not conflict with a valid pointer
- * because they all correspond to the highest addressable memory page.
- */
-#define MAX_ERRNO 4095
-
 
 /* Functions in this file only describe syscalls. They're declared static so
  * that the compiler usually decides to inline them while still being allowed