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 ret = sanity_check_segment_list(image); 67 if (ret) 68 goto out_free_image; 69 70 /* Enable the special crash kernel control page allocation policy. */ 71 if (kexec_on_panic) { 72 image->control_page = crashk_res.start; 73 image->type = KEXEC_TYPE_CRASH; 74 } 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; 136 137 /* 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); 212 213 out: 214 mutex_unlock(&kexec_mutex); 215 kimage_free(image); 216 217 return result; 218 } 219 220 #ifdef CONFIG_COMPAT 221 COMPAT_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 258