projects/linux·blob v4.6 · refs

257 lines · 6.6 KiB

1/*
2 * kexec.c - kexec_load system call
3 * Copyright (C) 2002-2004 Eric Biederman <[email protected]>
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
23static 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
40static 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;
99out_free_control_pages:
100 kimage_free_page_list(&image->control_pages);
101out_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
127SYSCALL_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
137 /*
138 * Verify we have a legal set of flags
139 * This leaves us room for future extensions.
140 */
141 if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK))
142 return -EINVAL;
143
144 /* Verify we are on the appropriate architecture */
145 if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) &&
146 ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT))
147 return -EINVAL;
148
149 /* Put an artificial cap on the number
150 * of segments passed to kexec_load.
151 */
152 if (nr_segments > KEXEC_SEGMENT_MAX)
153 return -EINVAL;
154
155 image = NULL;
156 result = 0;
157
158 /* Because we write directly to the reserved memory
159 * region when loading crash kernels we need a mutex here to
160 * prevent multiple crash kernels from attempting to load
161 * simultaneously, and to prevent a crash kernel from loading
162 * over the top of a in use crash kernel.
163 *
164 * KISS: always take the mutex.
165 */
166 if (!mutex_trylock(&kexec_mutex))
167 return -EBUSY;
168
169 dest_image = &kexec_image;
170 if (flags & KEXEC_ON_CRASH)
171 dest_image = &kexec_crash_image;
172 if (nr_segments > 0) {
173 unsigned long i;
174
175 if (flags & KEXEC_ON_CRASH) {
176 /*
177 * Loading another kernel to switch to if this one
178 * crashes. Free any current crash dump kernel before
179 * we corrupt it.
180 */
181
182 kimage_free(xchg(&kexec_crash_image, NULL));
183 result = kimage_alloc_init(&image, entry, nr_segments,
184 segments, flags);
185 crash_map_reserved_pages();
186 } else {
187 /* Loading another kernel to reboot into. */
188
189 result = kimage_alloc_init(&image, entry, nr_segments,
190 segments, flags);
191 }
192 if (result)
193 goto out;
194
195 if (flags & KEXEC_PRESERVE_CONTEXT)
196 image->preserve_context = 1;
197 result = machine_kexec_prepare(image);
198 if (result)
199 goto out;
200
201 for (i = 0; i < nr_segments; i++) {
202 result = kimage_load_segment(image, &image->segment[i]);
203 if (result)
204 goto out;
205 }
206 kimage_terminate(image);
207 if (flags & KEXEC_ON_CRASH)
208 crash_unmap_reserved_pages();
209 }
210 /* Install the new kernel, and Uninstall the old */
211 image = xchg(dest_image, image);
212
213out:
214 mutex_unlock(&kexec_mutex);
215 kimage_free(image);
216
217 return result;
218}
219
220#ifdef CONFIG_COMPAT
221COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
222 compat_ulong_t, nr_segments,
223 struct compat_kexec_segment __user *, segments,
224 compat_ulong_t, flags)
225{
226 struct compat_kexec_segment in;
227 struct kexec_segment out, __user *ksegments;
228 unsigned long i, result;
229
230 /* Don't allow clients that don't understand the native
231 * architecture to do anything.
232 */
233 if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT)
234 return -EINVAL;
235
236 if (nr_segments > KEXEC_SEGMENT_MAX)
237 return -EINVAL;
238
239 ksegments = compat_alloc_user_space(nr_segments * sizeof(out));
240 for (i = 0; i < nr_segments; i++) {
241 result = copy_from_user(&in, &segments[i], sizeof(in));
242 if (result)
243 return -EFAULT;
244
245 out.buf = compat_ptr(in.buf);
246 out.bufsz = in.bufsz;
247 out.mem = in.mem;
248 out.memsz = in.memsz;
249
250 result = copy_to_user(&ksegments[i], &out, sizeof(out));
251 if (result)
252 return -EFAULT;
253 }
254
255 return sys_kexec_load(entry, nr_segments, ksegments, flags);
256}
257#endif