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TOMOYO Linux Cross Reference
Linux/kernel/kexec.c

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

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