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 < 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 static int do_kexec_load(unsigned long entry, unsigned long nr_segments, 107 struct kexec_segment __user *segments, unsigned long flags) 108 { 109 struct kimage **dest_image, *image; 110 unsigned long i; 111 int ret; 112 113 if (flags & KEXEC_ON_CRASH) { 114 dest_image = &kexec_crash_image; 115 if (kexec_crash_image) 116 arch_kexec_unprotect_crashkres(); 117 } else { 118 dest_image = &kexec_image; 119 } 120 121 if (nr_segments == 0) { 122 /* Uninstall image */ 123 kimage_free(xchg(dest_image, NULL)); 124 return 0; 125 } 126 if (flags & KEXEC_ON_CRASH) { 127 /* 128 * Loading another kernel to switch to if this one 129 * crashes. Free any current crash dump kernel before 130 * we corrupt it. 131 */ 132 kimage_free(xchg(&kexec_crash_image, NULL)); 133 } 134 135 ret = kimage_alloc_init(&image, entry, nr_segments, segments, flags); 136 if (ret) 137 return ret; 138 139 if (flags & KEXEC_PRESERVE_CONTEXT) 140 image->preserve_context = 1; 141 142 ret = machine_kexec_prepare(image); 143 if (ret) 144 goto out; 145 146 for (i = 0; i < nr_segments; i++) { 147 ret = kimage_load_segment(image, &image->segment[i]); 148 if (ret) 149 goto out; 150 } 151 152 kimage_terminate(image); 153 154 /* Install the new kernel and uninstall the old */ 155 image = xchg(dest_image, image); 156 157 out: 158 if ((flags & KEXEC_ON_CRASH) && kexec_crash_image) 159 arch_kexec_protect_crashkres(); 160 161 kimage_free(image); 162 return ret; 163 } 164 165 /* 166 * Exec Kernel system call: for obvious reasons only root may call it. 167 * 168 * This call breaks up into three pieces. 169 * - A generic part which loads the new kernel from the current 170 * address space, and very carefully places the data in the 171 * allocated pages. 172 * 173 * - A generic part that interacts with the kernel and tells all of 174 * the devices to shut down. Preventing on-going dmas, and placing 175 * the devices in a consistent state so a later kernel can 176 * reinitialize them. 177 * 178 * - A machine specific part that includes the syscall number 179 * and then copies the image to it's final destination. And 180 * jumps into the image at entry. 181 * 182 * kexec does not sync, or unmount filesystems so if you need 183 * that to happen you need to do that yourself. 184 */ 185 186 SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments, 187 struct kexec_segment __user *, segments, unsigned long, flags) 188 { 189 int result; 190 191 /* We only trust the superuser with rebooting the system. */ 192 if (!capable(CAP_SYS_BOOT) || kexec_load_disabled) 193 return -EPERM; 194 195 /* 196 * Verify we have a legal set of flags 197 * This leaves us room for future extensions. 198 */ 199 if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK)) 200 return -EINVAL; 201 202 /* Verify we are on the appropriate architecture */ 203 if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) && 204 ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT)) 205 return -EINVAL; 206 207 /* Put an artificial cap on the number 208 * of segments passed to kexec_load. 209 */ 210 if (nr_segments > KEXEC_SEGMENT_MAX) 211 return -EINVAL; 212 213 /* Because we write directly to the reserved memory 214 * region when loading crash kernels we need a mutex here to 215 * prevent multiple crash kernels from attempting to load 216 * simultaneously, and to prevent a crash kernel from loading 217 * over the top of a in use crash kernel. 218 * 219 * KISS: always take the mutex. 220 */ 221 if (!mutex_trylock(&kexec_mutex)) 222 return -EBUSY; 223 224 result = do_kexec_load(entry, nr_segments, segments, flags); 225 226 mutex_unlock(&kexec_mutex); 227 228 return result; 229 } 230 231 #ifdef CONFIG_COMPAT 232 COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry, 233 compat_ulong_t, nr_segments, 234 struct compat_kexec_segment __user *, segments, 235 compat_ulong_t, flags) 236 { 237 struct compat_kexec_segment in; 238 struct kexec_segment out, __user *ksegments; 239 unsigned long i, result; 240 241 /* Don't allow clients that don't understand the native 242 * architecture to do anything. 243 */ 244 if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT) 245 return -EINVAL; 246 247 if (nr_segments > KEXEC_SEGMENT_MAX) 248 return -EINVAL; 249 250 ksegments = compat_alloc_user_space(nr_segments * sizeof(out)); 251 for (i = 0; i < nr_segments; i++) { 252 result = copy_from_user(&in, &segments[i], sizeof(in)); 253 if (result) 254 return -EFAULT; 255 256 out.buf = compat_ptr(in.buf); 257 out.bufsz = in.bufsz; 258 out.mem = in.mem; 259 out.memsz = in.memsz; 260 261 result = copy_to_user(&ksegments[i], &out, sizeof(out)); 262 if (result) 263 return -EFAULT; 264 } 265 266 return sys_kexec_load(entry, nr_segments, ksegments, flags); 267 } 268 #endif 269