kernel/kexec.c

   1 /*
   2  * kexec.c - kexec_load system call
   3  * Copyright (C) 2002-2004 Eric Biederman  <ebiederm@xmission.com>
   4  *
   5  * This source code is licensed under the GNU General Public License,
   6  * Version 2.  See the file COPYING for more details.
   7  */
   8
   9 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  10
  11 #include <linux/capability.h>
  12 #include <linux/mm.h>
  13 #include <linux/file.h>
  14 #include <linux/kexec.h>
  15 #include <linux/mutex.h>
  16 #include <linux/list.h>
  17 #include <linux/syscalls.h>
  18 #include <linux/vmalloc.h>
  19 #include <linux/slab.h>
  20
  21 #include "kexec_internal.h"
  22
  23 static int copy_user_segment_list(struct kimage *image,
  24                                   unsigned long nr_segments,
  25                                   struct kexec_segment __user *segments)
  26 {
  27         int ret;
  28         size_t segment_bytes;
  29
  30         /* Read in the segments */
  31         image->nr_segments = nr_segments;
  32         segment_bytes = nr_segments * sizeof(*segments);
  33         ret = copy_from_user(image->segment, segments, segment_bytes);
  34         if (ret)
  35                 ret = -EFAULT;
  36
  37         return ret;
  38 }
  39
  40 static int kimage_alloc_init(struct kimage **rimage, unsigned long entry,
  41                              unsigned long nr_segments,
  42                              struct kexec_segment __user *segments,
  43                              unsigned long flags)
  44 {
  45         int ret;
  46         struct kimage *image;
  47         bool kexec_on_panic = flags & KEXEC_ON_CRASH;
  48
  49         if (kexec_on_panic) {
  50                 /* Verify we have a valid entry point */
  51                 if ((entry < crashk_res.start) || (entry > crashk_res.end))
  52                         return -EADDRNOTAVAIL;
  53         }
  54
  55         /* Allocate and initialize a controlling structure */
  56         image = do_kimage_alloc_init();
  57         if (!image)
  58                 return -ENOMEM;
  59
  60         image->start = entry;
  61
  62         ret = copy_user_segment_list(image, nr_segments, segments);
  63         if (ret)
  64                 goto out_free_image;
  65
  66         ret = sanity_check_segment_list(image);
  67         if (ret)
  68                 goto out_free_image;
  69
  70          /* Enable the special crash kernel control page allocation policy. */
  71         if (kexec_on_panic) {
  72                 image->control_page = crashk_res.start;
  73                 image->type = KEXEC_TYPE_CRASH;
  74         }
  75
  76         /*
  77          * Find a location for the control code buffer, and add it
  78          * the vector of segments so that it's pages will also be
  79          * counted as destination pages.
  80          */
  81         ret = -ENOMEM;
  82         image->control_code_page = kimage_alloc_control_pages(image,
  83                                            get_order(KEXEC_CONTROL_PAGE_SIZE));
  84         if (!image->control_code_page) {
  85                 pr_err("Could not allocate control_code_buffer\n");
  86                 goto out_free_image;
  87         }
  88
  89         if (!kexec_on_panic) {
  90                 image->swap_page = kimage_alloc_control_pages(image, 0);
  91                 if (!image->swap_page) {
  92                         pr_err("Could not allocate swap buffer\n");
  93                         goto out_free_control_pages;
  94                 }
  95         }
  96
  97         *rimage = image;
  98         return 0;
  99 out_free_control_pages:
 100         kimage_free_page_list(&image->control_pages);
 101 out_free_image:
 102         kfree(image);
 103         return ret;
 104 }
 105
 106 /*
 107  * Exec Kernel system call: for obvious reasons only root may call it.
 108  *
 109  * This call breaks up into three pieces.
 110  * - A generic part which loads the new kernel from the current
 111  *   address space, and very carefully places the data in the
 112  *   allocated pages.
 113  *
 114  * - A generic part that interacts with the kernel and tells all of
 115  *   the devices to shut down.  Preventing on-going dmas, and placing
 116  *   the devices in a consistent state so a later kernel can
 117  *   reinitialize them.
 118  *
 119  * - A machine specific part that includes the syscall number
 120  *   and then copies the image to it's final destination.  And
 121  *   jumps into the image at entry.
 122  *
 123  * kexec does not sync, or unmount filesystems so if you need
 124  * that to happen you need to do that yourself.
 125  */
 126
 127 SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 128                 struct kexec_segment __user *, segments, unsigned long, flags)
 129 {
 130         struct kimage **dest_image, *image;
 131         int result;
 132
 133         /* We only trust the superuser with rebooting the system. */
 134         if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
 135                 return -EPERM;
 136
 137         /*
 138          * Verify we have a legal set of flags
 139          * This leaves us room for future extensions.
 140          */
 141         if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK))
 142                 return -EINVAL;
 143
 144         /* Verify we are on the appropriate architecture */
 145         if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) &&
 146                 ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT))
 147                 return -EINVAL;
 148
 149         /* Put an artificial cap on the number
 150          * of segments passed to kexec_load.
 151          */
 152         if (nr_segments > KEXEC_SEGMENT_MAX)
 153                 return -EINVAL;
 154
 155         image = NULL;
 156         result = 0;
 157
 158         /* Because we write directly to the reserved memory
 159          * region when loading crash kernels we need a mutex here to
 160          * prevent multiple crash  kernels from attempting to load
 161          * simultaneously, and to prevent a crash kernel from loading
 162          * over the top of a in use crash kernel.
 163          *
 164          * KISS: always take the mutex.
 165          */
 166         if (!mutex_trylock(&kexec_mutex))
 167                 return -EBUSY;
 168
 169         dest_image = &kexec_image;
 170         if (flags & KEXEC_ON_CRASH)
 171                 dest_image = &kexec_crash_image;
 172         if (nr_segments > 0) {
 173                 unsigned long i;
 174
 175                 if (flags & KEXEC_ON_CRASH) {
 176                         /*
 177                          * Loading another kernel to switch to if this one
 178                          * crashes.  Free any current crash dump kernel before
 179                          * we corrupt it.
 180                          */
 181
 182                         kimage_free(xchg(&kexec_crash_image, NULL));
 183                         result = kimage_alloc_init(&image, entry, nr_segments,
 184                                                    segments, flags);
 185                         crash_map_reserved_pages();
 186                 } else {
 187                         /* Loading another kernel to reboot into. */
 188
 189                         result = kimage_alloc_init(&image, entry, nr_segments,
 190                                                    segments, flags);
 191                 }
 192                 if (result)
 193                         goto out;
 194
 195                 if (flags & KEXEC_PRESERVE_CONTEXT)
 196                         image->preserve_context = 1;
 197                 result = machine_kexec_prepare(image);
 198                 if (result)
 199                         goto out;
 200
 201                 for (i = 0; i < nr_segments; i++) {
 202                         result = kimage_load_segment(image, &image->segment[i]);
 203                         if (result)
 204                                 goto out;
 205                 }
 206                 kimage_terminate(image);
 207                 if (flags & KEXEC_ON_CRASH)
 208                         crash_unmap_reserved_pages();
 209         }
 210         /* Install the new kernel, and  Uninstall the old */
 211         image = xchg(dest_image, image);
 212
 213 out:
 214         mutex_unlock(&kexec_mutex);
 215         kimage_free(image);
 216
 217         return result;
 218 }
 219
 220 #ifdef CONFIG_COMPAT
 221 COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
 222                        compat_ulong_t, nr_segments,
 223                        struct compat_kexec_segment __user *, segments,
 224                        compat_ulong_t, flags)
 225 {
 226         struct compat_kexec_segment in;
 227         struct kexec_segment out, __user *ksegments;
 228         unsigned long i, result;
 229
 230         /* Don't allow clients that don't understand the native
 231          * architecture to do anything.
 232          */
 233         if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT)
 234                 return -EINVAL;
 235
 236         if (nr_segments > KEXEC_SEGMENT_MAX)
 237                 return -EINVAL;
 238
 239         ksegments = compat_alloc_user_space(nr_segments * sizeof(out));
 240         for (i = 0; i < nr_segments; i++) {
 241                 result = copy_from_user(&in, &segments[i], sizeof(in));
 242                 if (result)
 243                         return -EFAULT;
 244
 245                 out.buf   = compat_ptr(in.buf);
 246                 out.bufsz = in.bufsz;
 247                 out.mem   = in.mem;
 248                 out.memsz = in.memsz;
 249
 250                 result = copy_to_user(&ksegments[i], &out, sizeof(out));
 251                 if (result)
 252                         return -EFAULT;
 253         }
 254
 255         return sys_kexec_load(entry, nr_segments, ksegments, flags);
 256 }
 257 #endif