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 /* Install the new kernel and uninstall the old */ 163 image = xchg(dest_image, image); 164 165 out: 166 if ((flags & KEXEC_ON_CRASH) && kexec_crash_image) 167 arch_kexec_protect_crashkres(); 168 169 kimage_free(image); 170 return ret; 171 } 172 173 /* 174 * Exec Kernel system call: for obvious reasons only root may call it. 175 * 176 * This call breaks up into three pieces. 177 * - A generic part which loads the new kernel from the current 178 * address space, and very carefully places the data in the 179 * allocated pages. 180 * 181 * - A generic part that interacts with the kernel and tells all of 182 * the devices to shut down. Preventing on-going dmas, and placing 183 * the devices in a consistent state so a later kernel can 184 * reinitialize them. 185 * 186 * - A machine specific part that includes the syscall number 187 * and then copies the image to it's final destination. And 188 * jumps into the image at entry. 189 * 190 * kexec does not sync, or unmount filesystems so if you need 191 * that to happen you need to do that yourself. 192 */ 193 194 static inline int kexec_load_check(unsigned long nr_segments, 195 unsigned long flags) 196 { 197 int result; 198 199 /* We only trust the superuser with rebooting the system. */ 200 if (!capable(CAP_SYS_BOOT) || kexec_load_disabled) 201 return -EPERM; 202 203 /* Permit LSMs and IMA to fail the kexec */ 204 result = security_kernel_load_data(LOADING_KEXEC_IMAGE); 205 if (result < 0) 206 return result; 207 208 /* 209 * kexec can be used to circumvent module loading restrictions, so 210 * prevent loading in that case 211 */ 212 result = security_locked_down(LOCKDOWN_KEXEC); 213 if (result) 214 return result; 215 216 /* 217 * Verify we have a legal set of flags 218 * This leaves us room for future extensions. 219 */ 220 if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK)) 221 return -EINVAL; 222 223 /* Put an artificial cap on the number 224 * of segments passed to kexec_load. 225 */ 226 if (nr_segments > KEXEC_SEGMENT_MAX) 227 return -EINVAL; 228 229 return 0; 230 } 231 232 SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments, 233 struct kexec_segment __user *, segments, unsigned long, flags) 234 { 235 int result; 236 237 result = kexec_load_check(nr_segments, flags); 238 if (result) 239 return result; 240 241 /* Verify we are on the appropriate architecture */ 242 if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) && 243 ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT)) 244 return -EINVAL; 245 246 /* Because we write directly to the reserved memory 247 * region when loading crash kernels we need a mutex here to 248 * prevent multiple crash kernels from attempting to load 249 * simultaneously, and to prevent a crash kernel from loading 250 * over the top of a in use crash kernel. 251 * 252 * KISS: always take the mutex. 253 */ 254 if (!mutex_trylock(&kexec_mutex)) 255 return -EBUSY; 256 257 result = do_kexec_load(entry, nr_segments, segments, flags); 258 259 mutex_unlock(&kexec_mutex); 260 261 return result; 262 } 263 264 #ifdef CONFIG_COMPAT 265 COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry, 266 compat_ulong_t, nr_segments, 267 struct compat_kexec_segment __user *, segments, 268 compat_ulong_t, flags) 269 { 270 struct compat_kexec_segment in; 271 struct kexec_segment out, __user *ksegments; 272 unsigned long i, result; 273 274 result = kexec_load_check(nr_segments, flags); 275 if (result) 276 return result; 277 278 /* Don't allow clients that don't understand the native 279 * architecture to do anything. 280 */ 281 if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT) 282 return -EINVAL; 283 284 ksegments = compat_alloc_user_space(nr_segments * sizeof(out)); 285 for (i = 0; i < nr_segments; i++) { 286 result = copy_from_user(&in, &segments[i], sizeof(in)); 287 if (result) 288 return -EFAULT; 289 290 out.buf = compat_ptr(in.buf); 291 out.bufsz = in.bufsz; 292 out.mem = in.mem; 293 out.memsz = in.memsz; 294 295 result = copy_to_user(&ksegments[i], &out, sizeof(out)); 296 if (result) 297 return -EFAULT; 298 } 299 300 /* Because we write directly to the reserved memory 301 * region when loading crash kernels we need a mutex here to 302 * prevent multiple crash kernels from attempting to load 303 * simultaneously, and to prevent a crash kernel from loading 304 * over the top of a in use crash kernel. 305 * 306 * KISS: always take the mutex. 307 */ 308 if (!mutex_trylock(&kexec_mutex)) 309 return -EBUSY; 310 311 result = do_kexec_load(entry, nr_segments, ksegments, flags); 312 313 mutex_unlock(&kexec_mutex); 314 315 return result; 316 } 317 #endif 318