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