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 copy_user_segment_list(struct kimage *image, 23 unsigned long nr_segments, 24 struct kexec_segment __user *segments) 25 { 26 int ret; 27 size_t segment_bytes; 28 29 /* Read in the segments */ 30 image->nr_segments = nr_segments; 31 segment_bytes = nr_segments * sizeof(*segments); 32 ret = copy_from_user(image->segment, segments, segment_bytes); 33 if (ret) 34 ret = -EFAULT; 35 36 return ret; 37 } 38 39 static int kimage_alloc_init(struct kimage **rimage, unsigned long entry, 40 unsigned long nr_segments, 41 struct kexec_segment __user *segments, 42 unsigned long flags) 43 { 44 int ret; 45 struct kimage *image; 46 bool kexec_on_panic = flags & KEXEC_ON_CRASH; 47 48 if (kexec_on_panic) { 49 /* Verify we have a valid entry point */ 50 if ((entry < phys_to_boot_phys(crashk_res.start)) || 51 (entry > phys_to_boot_phys(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 /* 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 if ((flags & KEXEC_ON_CRASH) && kexec_crash_image) 171 arch_kexec_protect_crashkres(); 172 173 kimage_free(image); 174 return ret; 175 } 176 177 /* 178 * Exec Kernel system call: for obvious reasons only root may call it. 179 * 180 * This call breaks up into three pieces. 181 * - A generic part which loads the new kernel from the current 182 * address space, and very carefully places the data in the 183 * allocated pages. 184 * 185 * - A generic part that interacts with the kernel and tells all of 186 * the devices to shut down. Preventing on-going dmas, and placing 187 * the devices in a consistent state so a later kernel can 188 * reinitialize them. 189 * 190 * - A machine specific part that includes the syscall number 191 * and then copies the image to it's final destination. And 192 * jumps into the image at entry. 193 * 194 * kexec does not sync, or unmount filesystems so if you need 195 * that to happen you need to do that yourself. 196 */ 197 198 static inline int kexec_load_check(unsigned long nr_segments, 199 unsigned long flags) 200 { 201 int result; 202 203 /* We only trust the superuser with rebooting the system. */ 204 if (!capable(CAP_SYS_BOOT) || kexec_load_disabled) 205 return -EPERM; 206 207 /* Permit LSMs and IMA to fail the kexec */ 208 result = security_kernel_load_data(LOADING_KEXEC_IMAGE, false); 209 if (result < 0) 210 return result; 211 212 /* 213 * kexec can be used to circumvent module loading restrictions, so 214 * prevent loading in that case 215 */ 216 result = security_locked_down(LOCKDOWN_KEXEC); 217 if (result) 218 return result; 219 220 /* 221 * Verify we have a legal set of flags 222 * This leaves us room for future extensions. 223 */ 224 if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK)) 225 return -EINVAL; 226 227 /* Put an artificial cap on the number 228 * of segments passed to kexec_load. 229 */ 230 if (nr_segments > KEXEC_SEGMENT_MAX) 231 return -EINVAL; 232 233 return 0; 234 } 235 236 SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments, 237 struct kexec_segment __user *, segments, unsigned long, flags) 238 { 239 int result; 240 241 result = kexec_load_check(nr_segments, flags); 242 if (result) 243 return result; 244 245 /* Verify we are on the appropriate architecture */ 246 if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) && 247 ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT)) 248 return -EINVAL; 249 250 /* Because we write directly to the reserved memory 251 * region when loading crash kernels we need a mutex here to 252 * prevent multiple crash kernels from attempting to load 253 * simultaneously, and to prevent a crash kernel from loading 254 * over the top of a in use crash kernel. 255 * 256 * KISS: always take the mutex. 257 */ 258 if (!mutex_trylock(&kexec_mutex)) 259 return -EBUSY; 260 261 result = do_kexec_load(entry, nr_segments, segments, flags); 262 263 mutex_unlock(&kexec_mutex); 264 265 return result; 266 } 267 268 #ifdef CONFIG_COMPAT 269 COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry, 270 compat_ulong_t, nr_segments, 271 struct compat_kexec_segment __user *, segments, 272 compat_ulong_t, flags) 273 { 274 struct compat_kexec_segment in; 275 struct kexec_segment out, __user *ksegments; 276 unsigned long i, result; 277 278 result = kexec_load_check(nr_segments, flags); 279 if (result) 280 return result; 281 282 /* Don't allow clients that don't understand the native 283 * architecture to do anything. 284 */ 285 if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT) 286 return -EINVAL; 287 288 ksegments = compat_alloc_user_space(nr_segments * sizeof(out)); 289 for (i = 0; i < nr_segments; i++) { 290 result = copy_from_user(&in, &segments[i], sizeof(in)); 291 if (result) 292 return -EFAULT; 293 294 out.buf = compat_ptr(in.buf); 295 out.bufsz = in.bufsz; 296 out.mem = in.mem; 297 out.memsz = in.memsz; 298 299 result = copy_to_user(&ksegments[i], &out, sizeof(out)); 300 if (result) 301 return -EFAULT; 302 } 303 304 /* Because we write directly to the reserved memory 305 * region when loading crash kernels we need a mutex here to 306 * prevent multiple crash kernels from attempting to load 307 * simultaneously, and to prevent a crash kernel from loading 308 * over the top of a in use crash kernel. 309 * 310 * KISS: always take the mutex. 311 */ 312 if (!mutex_trylock(&kexec_mutex)) 313 return -EBUSY; 314 315 result = do_kexec_load(entry, nr_segments, ksegments, flags); 316 317 mutex_unlock(&kexec_mutex); 318 319 return result; 320 } 321 #endif 322