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