init: unify opening /dev/console as stdin/stdout/stderr

Merge the two instances where /dev/console is opened as
stdin/stdout/stderr.
Signed-off-by: NDominik Brodowski <linux@dominikbrodowski.net>

include/linux/initrd.h

@@ -28,3 +28,5 @@ extern unsigned int real_root_dev;
 
 extern char __initramfs_start[];
 extern unsigned long __initramfs_size;
+
+void console_on_rootfs(void);

init/do_mounts_initrd.c

@@ -48,10 +48,7 @@ early_param("initrd", early_initrd);
 static int init_linuxrc(struct subprocess_info *info, struct cred *new)
 {
 	ksys_unshare(CLONE_FS | CLONE_FILES);
-	/* stdin/stdout/stderr for /linuxrc */
-	ksys_open("/dev/console", O_RDWR, 0);
-	ksys_dup(0);
-	ksys_dup(0);
+	console_on_rootfs();
 	/* move initrd over / and chdir/chroot in initrd root */
 	ksys_chdir("/root");
 	do_mount(".", "/", NULL, MS_MOVE, NULL);

init/main.c

@@ -1155,6 +1155,17 @@ static int __ref kernel_init(void *unused)
 	      "See Linux Documentation/admin-guide/init.rst for guidance.");
 }
 
+void console_on_rootfs(void)
+{
+	/* Open the /dev/console as stdin, this should never fail */
+	if (ksys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
+		pr_err("Warning: unable to open an initial console.\n");
+
+	/* create stdout/stderr */
+	(void) ksys_dup(0);
+	(void) ksys_dup(0);
+}
+
 static noinline void __init kernel_init_freeable(void)
 {
 	/*
@@ -1190,12 +1201,8 @@ static noinline void __init kernel_init_freeable(void)
 
 	do_basic_setup();
 
-	/* Open the /dev/console on the rootfs, this should never fail */
-	if (ksys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
-		pr_err("Warning: unable to open an initial console.\n");
+	console_on_rootfs();
 
-	(void) ksys_dup(0);
-	(void) ksys_dup(0);
 	/*
 	 * check if there is an early userspace init.  If yes, let it do all
 	 * the work