kernel/kexec.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * kexec.c - kexec_load system call
   4  * Copyright (C) 2002-2004 Eric Biederman  <ebiederm@xmission.com>
   5  */
   6
   7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   8
   9 #include <linux/capability.h>
  10 #include <linux/mm.h>
  11 #include <linux/file.h>
  12 #include <linux/security.h>
  13 #include <linux/kexec.h>
  14 #include <linux/mutex.h>
  15 #include <linux/list.h>
  16 #include <linux/syscalls.h>
  17 #include <linux/vmalloc.h>
  18 #include <linux/slab.h>
  19
  20 #include "kexec_internal.h"
  21
  22 static int kimage_alloc_init(struct kimage **rimage, unsigned long entry,
  23                              unsigned long nr_segments,
  24                              struct kexec_segment *segments,
  25                              unsigned long flags)
  26 {
  27         int ret;
  28         struct kimage *image;
  29         bool kexec_on_panic = flags & KEXEC_ON_CRASH;
  30
  31 #ifdef CONFIG_CRASH_DUMP
  32         if (kexec_on_panic) {
  33                 /* Verify we have a valid entry point */
  34                 if ((entry < phys_to_boot_phys(crashk_res.start)) ||
  35                     (entry > phys_to_boot_phys(crashk_res.end)))
  36                         return -EADDRNOTAVAIL;
  37         }
  38 #endif
  39
  40         /* Allocate and initialize a controlling structure */
  41         image = do_kimage_alloc_init();
  42         if (!image)
  43                 return -ENOMEM;
  44
  45         image->start = entry;
  46         image->nr_segments = nr_segments;
  47         memcpy(image->segment, segments, nr_segments * sizeof(*segments));
  48
  49 #ifdef CONFIG_CRASH_DUMP
  50         if (kexec_on_panic) {
  51                 /* Enable special crash kernel control page alloc policy. */
  52                 image->control_page = crashk_res.start;
  53                 image->type = KEXEC_TYPE_CRASH;
  54         }
  55 #endif
  56
  57         ret = sanity_check_segment_list(image);
  58         if (ret)
  59                 goto out_free_image;
  60
  61         /*
  62          * Find a location for the control code buffer, and add it
  63          * the vector of segments so that it's pages will also be
  64          * counted as destination pages.
  65          */
  66         ret = -ENOMEM;
  67         image->control_code_page = kimage_alloc_control_pages(image,
  68                                            get_order(KEXEC_CONTROL_PAGE_SIZE));
  69         if (!image->control_code_page) {
  70                 pr_err("Could not allocate control_code_buffer\n");
  71                 goto out_free_image;
  72         }
  73
  74         if (!kexec_on_panic) {
  75                 image->swap_page = kimage_alloc_control_pages(image, 0);
  76                 if (!image->swap_page) {
  77                         pr_err("Could not allocate swap buffer\n");
  78                         goto out_free_control_pages;
  79                 }
  80         }
  81
  82         *rimage = image;
  83         return 0;
  84 out_free_control_pages:
  85         kimage_free_page_list(&image->control_pages);
  86 out_free_image:
  87         kfree(image);
  88         return ret;
  89 }
  90
  91 static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
  92                 struct kexec_segment *segments, unsigned long flags)
  93 {
  94         struct kimage **dest_image, *image;
  95         unsigned long i;
  96         int ret;
  97
  98         /*
  99          * Because we write directly to the reserved memory region when loading
 100          * crash kernels we need a serialization here to prevent multiple crash
 101          * kernels from attempting to load simultaneously.
 102          */
 103         if (!kexec_trylock())
 104                 return -EBUSY;
 105
 106 #ifdef CONFIG_CRASH_DUMP
 107         if (flags & KEXEC_ON_CRASH) {
 108                 dest_image = &kexec_crash_image;
 109                 if (kexec_crash_image)
 110                         arch_kexec_unprotect_crashkres();
 111         } else
 112 #endif
 113                 dest_image = &kexec_image;
 114
 115         if (nr_segments == 0) {
 116                 /* Uninstall image */
 117                 kimage_free(xchg(dest_image, NULL));
 118                 ret = 0;
 119                 goto out_unlock;
 120         }
 121         if (flags & KEXEC_ON_CRASH) {
 122                 /*
 123                  * Loading another kernel to switch to if this one
 124                  * crashes.  Free any current crash dump kernel before
 125                  * we corrupt it.
 126                  */
 127                 kimage_free(xchg(&kexec_crash_image, NULL));
 128         }
 129
 130         ret = kimage_alloc_init(&image, entry, nr_segments, segments, flags);
 131         if (ret)
 132                 goto out_unlock;
 133
 134         if (flags & KEXEC_PRESERVE_CONTEXT)
 135                 image->preserve_context = 1;
 136
 137 #ifdef CONFIG_CRASH_HOTPLUG
 138         if (flags & KEXEC_UPDATE_ELFCOREHDR)
 139                 image->update_elfcorehdr = 1;
 140 #endif
 141
 142         ret = machine_kexec_prepare(image);
 143         if (ret)
 144                 goto out;
 145
 146         /*
 147          * Some architecture(like S390) may touch the crash memory before
 148          * machine_kexec_prepare(), we must copy vmcoreinfo data after it.
 149          */
 150         ret = kimage_crash_copy_vmcoreinfo(image);
 151         if (ret)
 152                 goto out;
 153
 154         for (i = 0; i < nr_segments; i++) {
 155                 ret = kimage_load_segment(image, &image->segment[i]);
 156                 if (ret)
 157                         goto out;
 158         }
 159
 160         kimage_terminate(image);
 161
 162         ret = machine_kexec_post_load(image);
 163         if (ret)
 164                 goto out;
 165
 166         /* Install the new kernel and uninstall the old */
 167         image = xchg(dest_image, image);
 168
 169 out:
 170 #ifdef CONFIG_CRASH_DUMP
 171         if ((flags & KEXEC_ON_CRASH) && kexec_crash_image)
 172                 arch_kexec_protect_crashkres();
 173 #endif
 174
 175         kimage_free(image);
 176 out_unlock:
 177         kexec_unlock();
 178         return ret;
 179 }
 180
 181 /*
 182  * Exec Kernel system call: for obvious reasons only root may call it.
 183  *
 184  * This call breaks up into three pieces.
 185  * - A generic part which loads the new kernel from the current
 186  *   address space, and very carefully places the data in the
 187  *   allocated pages.
 188  *
 189  * - A generic part that interacts with the kernel and tells all of
 190  *   the devices to shut down.  Preventing on-going dmas, and placing
 191  *   the devices in a consistent state so a later kernel can
 192  *   reinitialize them.
 193  *
 194  * - A machine specific part that includes the syscall number
 195  *   and then copies the image to it's final destination.  And
 196  *   jumps into the image at entry.
 197  *
 198  * kexec does not sync, or unmount filesystems so if you need
 199  * that to happen you need to do that yourself.
 200  */
 201
 202 static inline int kexec_load_check(unsigned long nr_segments,
 203                                    unsigned long flags)
 204 {
 205         int image_type = (flags & KEXEC_ON_CRASH) ?
 206                          KEXEC_TYPE_CRASH : KEXEC_TYPE_DEFAULT;
 207         int result;
 208
 209         /* We only trust the superuser with rebooting the system. */
 210         if (!kexec_load_permitted(image_type))
 211                 return -EPERM;
 212
 213         /* Permit LSMs and IMA to fail the kexec */
 214         result = security_kernel_load_data(LOADING_KEXEC_IMAGE, false);
 215         if (result < 0)
 216                 return result;
 217
 218         /*
 219          * kexec can be used to circumvent module loading restrictions, so
 220          * prevent loading in that case
 221          */
 222         result = security_locked_down(LOCKDOWN_KEXEC);
 223         if (result)
 224                 return result;
 225
 226         /*
 227          * Verify we have a legal set of flags
 228          * This leaves us room for future extensions.
 229          */
 230         if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK))
 231                 return -EINVAL;
 232
 233         /* Put an artificial cap on the number
 234          * of segments passed to kexec_load.
 235          */
 236         if (nr_segments > KEXEC_SEGMENT_MAX)
 237                 return -EINVAL;
 238
 239         return 0;
 240 }
 241
 242 SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 243                 struct kexec_segment __user *, segments, unsigned long, flags)
 244 {
 245         struct kexec_segment *ksegments;
 246         unsigned long result;
 247
 248         result = kexec_load_check(nr_segments, flags);
 249         if (result)
 250                 return result;
 251
 252         /* Verify we are on the appropriate architecture */
 253         if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) &&
 254                 ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT))
 255                 return -EINVAL;
 256
 257         ksegments = memdup_array_user(segments, nr_segments, sizeof(ksegments[0]));
 258         if (IS_ERR(ksegments))
 259                 return PTR_ERR(ksegments);
 260
 261         result = do_kexec_load(entry, nr_segments, ksegments, flags);
 262         kfree(ksegments);
 263
 264         return result;
 265 }
 266
 267 #ifdef CONFIG_COMPAT
 268 COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
 269                        compat_ulong_t, nr_segments,
 270                        struct compat_kexec_segment __user *, segments,
 271                        compat_ulong_t, flags)
 272 {
 273         struct compat_kexec_segment in;
 274         struct kexec_segment *ksegments;
 275         unsigned long i, result;
 276
 277         result = kexec_load_check(nr_segments, flags);
 278         if (result)
 279                 return result;
 280
 281         /* Don't allow clients that don't understand the native
 282          * architecture to do anything.
 283          */
 284         if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT)
 285                 return -EINVAL;
 286
 287         ksegments = kmalloc_array(nr_segments, sizeof(ksegments[0]),
 288                         GFP_KERNEL);
 289         if (!ksegments)
 290                 return -ENOMEM;
 291
 292         for (i = 0; i < nr_segments; i++) {
 293                 result = copy_from_user(&in, &segments[i], sizeof(in));
 294                 if (result)
 295                         goto fail;
 296
 297                 ksegments[i].buf   = compat_ptr(in.buf);
 298                 ksegments[i].bufsz = in.bufsz;
 299                 ksegments[i].mem   = in.mem;
 300                 ksegments[i].memsz = in.memsz;
 301         }
 302
 303         result = do_kexec_load(entry, nr_segments, ksegments, flags);
 304
 305 fail:
 306         kfree(ksegments);
 307         return result;
 308 }
 309 #endif