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Linux/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
270 

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