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