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/module.h>
  16 #include <linux/mutex.h>
  17 #include <linux/list.h>
  18 #include <linux/syscalls.h>
  19 #include <linux/vmalloc.h>
  20 #include <linux/slab.h>
  21
  22 #include "kexec_internal.h"
  23
  24 static int copy_user_segment_list(struct kimage *image,
  25                                   unsigned long nr_segments,
  26                                   struct kexec_segment __user *segments)
  27 {
  28         int ret;
  29         size_t segment_bytes;
  30
  31         /* Read in the segments */
  32         image->nr_segments = nr_segments;
  33         segment_bytes = nr_segments * sizeof(*segments);
  34         ret = copy_from_user(image->segment, segments, segment_bytes);
  35         if (ret)
  36                 ret = -EFAULT;
  37
  38         return ret;
  39 }
  40
  41 static int kimage_alloc_init(struct kimage **rimage, unsigned long entry,
  42                              unsigned long nr_segments,
  43                              struct kexec_segment __user *segments,
  44                              unsigned long flags)
  45 {
  46         int ret;
  47         struct kimage *image;
  48         bool kexec_on_panic = flags & KEXEC_ON_CRASH;
  49
  50         if (kexec_on_panic) {
  51                 /* Verify we have a valid entry point */
  52                 if ((entry < phys_to_boot_phys(crashk_res.start)) ||
  53                     (entry > phys_to_boot_phys(crashk_res.end)))
  54                         return -EADDRNOTAVAIL;
  55         }
  56
  57         /* Allocate and initialize a controlling structure */
  58         image = do_kimage_alloc_init();
  59         if (!image)
  60                 return -ENOMEM;
  61
  62         image->start = entry;
  63
  64         ret = copy_user_segment_list(image, nr_segments, segments);
  65         if (ret)
  66                 goto out_free_image;
  67
  68         if (kexec_on_panic) {
  69                 /* Enable special crash kernel control page alloc policy. */
  70                 image->control_page = crashk_res.start;
  71                 image->type = KEXEC_TYPE_CRASH;
  72         }
  73
  74         ret = sanity_check_segment_list(image);
  75         if (ret)
  76                 goto out_free_image;
  77
  78         /*
  79          * Find a location for the control code buffer, and add it
  80          * the vector of segments so that it's pages will also be
  81          * counted as destination pages.
  82          */
  83         ret = -ENOMEM;
  84         image->control_code_page = kimage_alloc_control_pages(image,
  85                                            get_order(KEXEC_CONTROL_PAGE_SIZE));
  86         if (!image->control_code_page) {
  87                 pr_err("Could not allocate control_code_buffer\n");
  88                 goto out_free_image;
  89         }
  90
  91         if (!kexec_on_panic) {
  92                 image->swap_page = kimage_alloc_control_pages(image, 0);
  93                 if (!image->swap_page) {
  94                         pr_err("Could not allocate swap buffer\n");
  95                         goto out_free_control_pages;
  96                 }
  97         }
  98
  99         *rimage = image;
 100         return 0;
 101 out_free_control_pages:
 102         kimage_free_page_list(&image->control_pages);
 103 out_free_image:
 104         kfree(image);
 105         return ret;
 106 }
 107
 108 static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
 109                 struct kexec_segment __user *segments, unsigned long flags)
 110 {
 111         struct kimage **dest_image, *image;
 112         unsigned long i;
 113         int ret;
 114
 115         if (flags & KEXEC_ON_CRASH) {
 116                 dest_image = &kexec_crash_image;
 117                 if (kexec_crash_image)
 118                         arch_kexec_unprotect_crashkres();
 119         } else {
 120                 dest_image = &kexec_image;
 121         }
 122
 123         if (nr_segments == 0) {
 124                 /* Uninstall image */
 125                 kimage_free(xchg(dest_image, NULL));
 126                 return 0;
 127         }
 128         if (flags & KEXEC_ON_CRASH) {
 129                 /*
 130                  * Loading another kernel to switch to if this one
 131                  * crashes.  Free any current crash dump kernel before
 132                  * we corrupt it.
 133                  */
 134                 kimage_free(xchg(&kexec_crash_image, NULL));
 135         }
 136
 137         ret = kimage_alloc_init(&image, entry, nr_segments, segments, flags);
 138         if (ret)
 139                 return ret;
 140
 141         if (flags & KEXEC_PRESERVE_CONTEXT)
 142                 image->preserve_context = 1;
 143
 144         ret = machine_kexec_prepare(image);
 145         if (ret)
 146                 goto out;
 147
 148         for (i = 0; i < nr_segments; i++) {
 149                 ret = kimage_load_segment(image, &image->segment[i]);
 150                 if (ret)
 151                         goto out;
 152         }
 153
 154         kimage_terminate(image);
 155
 156         /* Install the new kernel and uninstall the old */
 157         image = xchg(dest_image, image);
 158
 159 out:
 160         if ((flags & KEXEC_ON_CRASH) && kexec_crash_image)
 161                 arch_kexec_protect_crashkres();
 162
 163         kimage_free(image);
 164         return ret;
 165 }
 166
 167 /*
 168  * Exec Kernel system call: for obvious reasons only root may call it.
 169  *
 170  * This call breaks up into three pieces.
 171  * - A generic part which loads the new kernel from the current
 172  *   address space, and very carefully places the data in the
 173  *   allocated pages.
 174  *
 175  * - A generic part that interacts with the kernel and tells all of
 176  *   the devices to shut down.  Preventing on-going dmas, and placing
 177  *   the devices in a consistent state so a later kernel can
 178  *   reinitialize them.
 179  *
 180  * - A machine specific part that includes the syscall number
 181  *   and then copies the image to it's final destination.  And
 182  *   jumps into the image at entry.
 183  *
 184  * kexec does not sync, or unmount filesystems so if you need
 185  * that to happen you need to do that yourself.
 186  */
 187
 188 SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 189                 struct kexec_segment __user *, segments, unsigned long, flags)
 190 {
 191         int result;
 192
 193         /* We only trust the superuser with rebooting the system. */
 194         if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
 195                 return -EPERM;
 196
 197         /*
 198          * kexec can be used to circumvent module loading restrictions, so
 199          * prevent loading in that case
 200          */
 201         if (secure_modules())
 202                 return -EPERM;
 203
 204         /*
 205          * Verify we have a legal set of flags
 206          * This leaves us room for future extensions.
 207          */
 208         if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK))
 209                 return -EINVAL;
 210
 211         /* Verify we are on the appropriate architecture */
 212         if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) &&
 213                 ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT))
 214                 return -EINVAL;
 215
 216         /* Put an artificial cap on the number
 217          * of segments passed to kexec_load.
 218          */
 219         if (nr_segments > KEXEC_SEGMENT_MAX)
 220                 return -EINVAL;
 221
 222         /* Because we write directly to the reserved memory
 223          * region when loading crash kernels we need a mutex here to
 224          * prevent multiple crash  kernels from attempting to load
 225          * simultaneously, and to prevent a crash kernel from loading
 226          * over the top of a in use crash kernel.
 227          *
 228          * KISS: always take the mutex.
 229          */
 230         if (!mutex_trylock(&kexec_mutex))
 231                 return -EBUSY;
 232
 233         result = do_kexec_load(entry, nr_segments, segments, flags);
 234
 235         mutex_unlock(&kexec_mutex);
 236
 237         return result;
 238 }
 239
 240 #ifdef CONFIG_COMPAT
 241 COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
 242                        compat_ulong_t, nr_segments,
 243                        struct compat_kexec_segment __user *, segments,
 244                        compat_ulong_t, flags)
 245 {
 246         struct compat_kexec_segment in;
 247         struct kexec_segment out, __user *ksegments;
 248         unsigned long i, result;
 249
 250         /* Don't allow clients that don't understand the native
 251          * architecture to do anything.
 252          */
 253         if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT)
 254                 return -EINVAL;
 255
 256         if (nr_segments > KEXEC_SEGMENT_MAX)
 257                 return -EINVAL;
 258
 259         ksegments = compat_alloc_user_space(nr_segments * sizeof(out));
 260         for (i = 0; i < nr_segments; i++) {
 261                 result = copy_from_user(&in, &segments[i], sizeof(in));
 262                 if (result)
 263                         return -EFAULT;
 264
 265                 out.buf   = compat_ptr(in.buf);
 266                 out.bufsz = in.bufsz;
 267                 out.mem   = in.mem;
 268                 out.memsz = in.memsz;
 269
 270                 result = copy_to_user(&ksegments[i], &out, sizeof(out));
 271                 if (result)
 272                         return -EFAULT;
 273         }
 274
 275         return sys_kexec_load(entry, nr_segments, ksegments, flags);
 276 }
 277 #endif