text: // SPDX-License-Identifier: GPL-2.0
  #include <linux/unistd.h>
  #include <linux/kernel.h>
  #include <linux/fs.h>
  #include <linux/minix_fs.h>
  #include <linux/romfs_fs.h>
  #include <linux/initrd.h>
  #include <linux/sched.h>
  #include <linux/freezer.h>
  #include <linux/kmod.h>
  
  #include "do_mounts.h"
  
  unsigned long initrd_start, initrd_end;
  int initrd_below_start_ok;
  unsigned int real_root_dev;	/* do_proc_dointvec cannot handle kdev_t */
  static int __initdata mount_initrd = 1;
  
  static int __init no_initrd(char *str)
  {
  	mount_initrd = 0;
  	return 1;
  }
  
  __setup("noinitrd", no_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);
  	/* move initrd over / and chdir/chroot in initrd root */
  	ksys_chdir("/root");
  	ksys_mount(".", "/", NULL, MS_MOVE, NULL);
  	ksys_chroot(".");
  	ksys_setsid();
  	return 0;
  }
  
  static void __init handle_initrd(void)
  {
  	struct subprocess_info *info;
  	static char *argv[] = { "linuxrc", NULL, };
  	extern char *envp_init[];
  	int error;
  
  	real_root_dev = new_encode_dev(ROOT_DEV);
  	create_dev("/dev/root.old", Root_RAM0);
  	/* mount initrd on rootfs' /root */
  	mount_block_root("/dev/root.old", root_mountflags & ~MS_RDONLY);
  	ksys_mkdir("/old", 0700);
  	ksys_chdir("/old");
  
  	/* try loading default modules from initrd */
  	load_default_modules();
  
  	/*
  	 * In case that a resume from disk is carried out by linuxrc or one of
  	 * its children, we need to tell the freezer not to wait for us.
  	 */
  	current->flags |= PF_FREEZER_SKIP;
  
  	info = call_usermodehelper_setup("/linuxrc", argv, envp_init,
  					 GFP_KERNEL, init_linuxrc, NULL, NULL);
  	if (!info)
  		return;
  	call_usermodehelper_exec(info, UMH_WAIT_PROC);
  
  	current->flags &= ~PF_FREEZER_SKIP;
  
  	/* move initrd to rootfs' /old */
  	ksys_mount("..", ".", NULL, MS_MOVE, NULL);
  	/* switch root and cwd back to / of rootfs */
  	ksys_chroot("..");
  
  	if (new_decode_dev(real_root_dev) == Root_RAM0) {
  		ksys_chdir("/old");
  		return;
  	}
  
  	ksys_chdir("/");
  	ROOT_DEV = new_decode_dev(real_root_dev);
  	mount_root();
  
  	printk(KERN_NOTICE "Trying to move old root to /initrd ... ");
  	error = ksys_mount("/old", "/root/initrd", NULL, MS_MOVE, NULL);
  	if (!error)
  		printk("okay\n");
  	else {
  		int fd = ksys_open("/dev/root.old", O_RDWR, 0);
  		if (error == -ENOENT)
  			printk("/initrd does not exist. Ignored.\n");
  		else
  			printk("failed\n");
  		printk(KERN_NOTICE "Unmounting old root\n");
  		ksys_umount("/old", MNT_DETACH);
  		printk(KERN_NOTICE "Trying to free ramdisk memory ... ");
  		if (fd < 0) {
  			error = fd;
  		} else {
  			error = ksys_ioctl(fd, BLKFLSBUF, 0);
  			ksys_close(fd);
  		}
  		printk(!error ? "okay\n" : "failed\n");
  	}
  }
  
  bool __init initrd_load(void)
  {
  	if (mount_initrd) {
  		create_dev("/dev/ram", Root_RAM0);
  		/*
  		 * Load the initrd data into /dev/ram0. Execute it as initrd
  		 * unless /dev/ram0 is supposed to be our actual root device,
  		 * in that case the ram disk is just set up here, and gets
  		 * mounted in the normal path.
  		 */
  		if (rd_load_image("/initrd.image") && ROOT_DEV != Root_RAM0) {
  			ksys_unlink("/initrd.image");
  			handle_initrd();
  			return true;
  		}
  	}
  	ksys_unlink("/initrd.image");
  	return false;
  }
  