init/do_mounts_initrd.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/unistd.h>
   3 #include <linux/kernel.h>
   4 #include <linux/fs.h>
   5 #include <linux/minix_fs.h>
   6 #include <linux/romfs_fs.h>
   7 #include <linux/initrd.h>
   8 #include <linux/sched.h>
   9 #include <linux/freezer.h>
  10 #include <linux/kmod.h>
  11 #include <uapi/linux/mount.h>
  12
  13 #include "do_mounts.h"
  14
  15 unsigned long initrd_start, initrd_end;
  16 int initrd_below_start_ok;
  17 static unsigned int real_root_dev;      /* do_proc_dointvec cannot handle kdev_t */
  18 static int __initdata mount_initrd = 1;
  19
  20 phys_addr_t phys_initrd_start __initdata;
  21 unsigned long phys_initrd_size __initdata;
  22
  23 #ifdef CONFIG_SYSCTL
  24 static struct ctl_table kern_do_mounts_initrd_table[] = {
  25         {
  26                 .procname       = "real-root-dev",
  27                 .data           = &real_root_dev,
  28                 .maxlen         = sizeof(int),
  29                 .mode           = 0644,
  30                 .proc_handler   = proc_dointvec,
  31         },
  32         { }
  33 };
  34
  35 static __init int kernel_do_mounts_initrd_sysctls_init(void)
  36 {
  37         register_sysctl_init("kernel", kern_do_mounts_initrd_table);
  38         return 0;
  39 }
  40 late_initcall(kernel_do_mounts_initrd_sysctls_init);
  41 #endif /* CONFIG_SYSCTL */
  42
  43 static int __init no_initrd(char *str)
  44 {
  45         mount_initrd = 0;
  46         return 1;
  47 }
  48
  49 __setup("noinitrd", no_initrd);
  50
  51 static int __init early_initrdmem(char *p)
  52 {
  53         phys_addr_t start;
  54         unsigned long size;
  55         char *endp;
  56
  57         start = memparse(p, &endp);
  58         if (*endp == ',') {
  59                 size = memparse(endp + 1, NULL);
  60
  61                 phys_initrd_start = start;
  62                 phys_initrd_size = size;
  63         }
  64         return 0;
  65 }
  66 early_param("initrdmem", early_initrdmem);
  67
  68 static int __init early_initrd(char *p)
  69 {
  70         return early_initrdmem(p);
  71 }
  72 early_param("initrd", early_initrd);
  73
  74 static int __init init_linuxrc(struct subprocess_info *info, struct cred *new)
  75 {
  76         ksys_unshare(CLONE_FS | CLONE_FILES);
  77         console_on_rootfs();
  78         /* move initrd over / and chdir/chroot in initrd root */
  79         init_chdir("/root");
  80         init_mount(".", "/", NULL, MS_MOVE, NULL);
  81         init_chroot(".");
  82         ksys_setsid();
  83         return 0;
  84 }
  85
  86 static void __init handle_initrd(char *root_device_name)
  87 {
  88         struct subprocess_info *info;
  89         static char *argv[] = { "linuxrc", NULL, };
  90         extern char *envp_init[];
  91         int error;
  92
  93         pr_warn("using deprecated initrd support, will be removed in 2021.\n");
  94
  95         real_root_dev = new_encode_dev(ROOT_DEV);
  96         create_dev("/dev/root.old", Root_RAM0);
  97         /* mount initrd on rootfs' /root */
  98         mount_root_generic("/dev/root.old", root_device_name,
  99                            root_mountflags & ~MS_RDONLY);
 100         init_mkdir("/old", 0700);
 101         init_chdir("/old");
 102
 103         info = call_usermodehelper_setup("/linuxrc", argv, envp_init,
 104                                          GFP_KERNEL, init_linuxrc, NULL, NULL);
 105         if (!info)
 106                 return;
 107         call_usermodehelper_exec(info, UMH_WAIT_PROC|UMH_FREEZABLE);
 108
 109         /* move initrd to rootfs' /old */
 110         init_mount("..", ".", NULL, MS_MOVE, NULL);
 111         /* switch root and cwd back to / of rootfs */
 112         init_chroot("..");
 113
 114         if (new_decode_dev(real_root_dev) == Root_RAM0) {
 115                 init_chdir("/old");
 116                 return;
 117         }
 118
 119         init_chdir("/");
 120         ROOT_DEV = new_decode_dev(real_root_dev);
 121         mount_root(root_device_name);
 122
 123         printk(KERN_NOTICE "Trying to move old root to /initrd ... ");
 124         error = init_mount("/old", "/root/initrd", NULL, MS_MOVE, NULL);
 125         if (!error)
 126                 printk("okay\n");
 127         else {
 128                 if (error == -ENOENT)
 129                         printk("/initrd does not exist. Ignored.\n");
 130                 else
 131                         printk("failed\n");
 132                 printk(KERN_NOTICE "Unmounting old root\n");
 133                 init_umount("/old", MNT_DETACH);
 134         }
 135 }
 136
 137 bool __init initrd_load(char *root_device_name)
 138 {
 139         if (mount_initrd) {
 140                 create_dev("/dev/ram", Root_RAM0);
 141                 /*
 142                  * Load the initrd data into /dev/ram0. Execute it as initrd
 143                  * unless /dev/ram0 is supposed to be our actual root device,
 144                  * in that case the ram disk is just set up here, and gets
 145                  * mounted in the normal path.
 146                  */
 147                 if (rd_load_image("/initrd.image") && ROOT_DEV != Root_RAM0) {
 148                         init_unlink("/initrd.image");
 149                         handle_initrd(root_device_name);
 150                         return true;
 151                 }
 152         }
 153         init_unlink("/initrd.image");
 154         return false;
 155 }