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/security.h>
  15 #include <linux/kexec.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         /*
 149          * Some architecture(like S390) may touch the crash memory before
 150          * machine_kexec_prepare(), we must copy vmcoreinfo data after it.
 151          */
 152         ret = kimage_crash_copy_vmcoreinfo(image);
 153         if (ret)
 154                 goto out;
 155
 156         for (i = 0; i < nr_segments; i++) {
 157                 ret = kimage_load_segment(image, &image->segment[i]);
 158                 if (ret)
 159                         goto out;
 160         }
 161
 162         kimage_terminate(image);
 163
 164         /* Install the new kernel and uninstall the old */
 165         image = xchg(dest_image, image);
 166
 167 out:
 168         if ((flags & KEXEC_ON_CRASH) && kexec_crash_image)
 169                 arch_kexec_protect_crashkres();
 170
 171         kimage_free(image);
 172         return ret;
 173 }
 174
 175 /*
 176  * Exec Kernel system call: for obvious reasons only root may call it.
 177  *
 178  * This call breaks up into three pieces.
 179  * - A generic part which loads the new kernel from the current
 180  *   address space, and very carefully places the data in the
 181  *   allocated pages.
 182  *
 183  * - A generic part that interacts with the kernel and tells all of
 184  *   the devices to shut down.  Preventing on-going dmas, and placing
 185  *   the devices in a consistent state so a later kernel can
 186  *   reinitialize them.
 187  *
 188  * - A machine specific part that includes the syscall number
 189  *   and then copies the image to it's final destination.  And
 190  *   jumps into the image at entry.
 191  *
 192  * kexec does not sync, or unmount filesystems so if you need
 193  * that to happen you need to do that yourself.
 194  */
 195
 196 static inline int kexec_load_check(unsigned long nr_segments,
 197                                    unsigned long flags)
 198 {
 199         int result;
 200
 201         /* We only trust the superuser with rebooting the system. */
 202         if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
 203                 return -EPERM;
 204
 205         /* Permit LSMs and IMA to fail the kexec */
 206         result = security_kernel_load_data(LOADING_KEXEC_IMAGE);
 207         if (result < 0)
 208                 return result;
 209
 210         /*
 211          * Verify we have a legal set of flags
 212          * This leaves us room for future extensions.
 213          */
 214         if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK))
 215                 return -EINVAL;
 216
 217         /* Put an artificial cap on the number
 218          * of segments passed to kexec_load.
 219          */
 220         if (nr_segments > KEXEC_SEGMENT_MAX)
 221                 return -EINVAL;
 222
 223         return 0;
 224 }
 225
 226 SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 227                 struct kexec_segment __user *, segments, unsigned long, flags)
 228 {
 229         int result;
 230
 231         result = kexec_load_check(nr_segments, flags);
 232         if (result)
 233                 return result;
 234
 235         /* Verify we are on the appropriate architecture */
 236         if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) &&
 237                 ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT))
 238                 return -EINVAL;
 239
 240         /* Because we write directly to the reserved memory
 241          * region when loading crash kernels we need a mutex here to
 242          * prevent multiple crash  kernels from attempting to load
 243          * simultaneously, and to prevent a crash kernel from loading
 244          * over the top of a in use crash kernel.
 245          *
 246          * KISS: always take the mutex.
 247          */
 248         if (!mutex_trylock(&kexec_mutex))
 249                 return -EBUSY;
 250
 251         result = do_kexec_load(entry, nr_segments, segments, flags);
 252
 253         mutex_unlock(&kexec_mutex);
 254
 255         return result;
 256 }
 257
 258 #ifdef CONFIG_COMPAT
 259 COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
 260                        compat_ulong_t, nr_segments,
 261                        struct compat_kexec_segment __user *, segments,
 262                        compat_ulong_t, flags)
 263 {
 264         struct compat_kexec_segment in;
 265         struct kexec_segment out, __user *ksegments;
 266         unsigned long i, result;
 267
 268         result = kexec_load_check(nr_segments, flags);
 269         if (result)
 270                 return result;
 271
 272         /* Don't allow clients that don't understand the native
 273          * architecture to do anything.
 274          */
 275         if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT)
 276                 return -EINVAL;
 277
 278         ksegments = compat_alloc_user_space(nr_segments * sizeof(out));
 279         for (i = 0; i < nr_segments; i++) {
 280                 result = copy_from_user(&in, &segments[i], sizeof(in));
 281                 if (result)
 282                         return -EFAULT;
 283
 284                 out.buf   = compat_ptr(in.buf);
 285                 out.bufsz = in.bufsz;
 286                 out.mem   = in.mem;
 287                 out.memsz = in.memsz;
 288
 289                 result = copy_to_user(&ksegments[i], &out, sizeof(out));
 290                 if (result)
 291                         return -EFAULT;
 292         }
 293
 294         /* Because we write directly to the reserved memory
 295          * region when loading crash kernels we need a mutex here to
 296          * prevent multiple crash  kernels from attempting to load
 297          * simultaneously, and to prevent a crash kernel from loading
 298          * over the top of a in use crash kernel.
 299          *
 300          * KISS: always take the mutex.
 301          */
 302         if (!mutex_trylock(&kexec_mutex))
 303                 return -EBUSY;
 304
 305         result = do_kexec_load(entry, nr_segments, ksegments, flags);
 306
 307         mutex_unlock(&kexec_mutex);
 308
 309         return result;
 310 }
 311 #endif