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 #include <linux/capability.h> 10 #include <linux/mm.h> 11 #include <linux/file.h> 12 #include <linux/kexec.h> 13 #include <linux/mutex.h> 14 #include <linux/list.h> 15 #include <linux/syscalls.h> 16 #include <linux/vmalloc.h> 17 #include <linux/slab.h> 18 19 #include "kexec_internal.h" 20 21 static int copy_user_segment_list(struct kimage *image, 22 unsigned long nr_segments, 23 struct kexec_segment __user *segments) 24 { 25 int ret; 26 size_t segment_bytes; 27 28 /* Read in the segments */ 29 image->nr_segments = nr_segments; 30 segment_bytes = nr_segments * sizeof(*segments); 31 ret = copy_from_user(image->segment, segments, segment_bytes); 32 if (ret) 33 ret = -EFAULT; 34 35 return ret; 36 } 37 38 static int kimage_alloc_init(struct kimage **rimage, unsigned long entry, 39 unsigned long nr_segments, 40 struct kexec_segment __user *segments, 41 unsigned long flags) 42 { 43 int ret; 44 struct kimage *image; 45 bool kexec_on_panic = flags & KEXEC_ON_CRASH; 46 47 if (kexec_on_panic) { 48 /* Verify we have a valid entry point */ 49 if ((entry < crashk_res.start) || (entry > crashk_res.end)) 50 return -EADDRNOTAVAIL; 51 } 52 53 /* Allocate and initialize a controlling structure */ 54 image = do_kimage_alloc_init(); 55 if (!image) 56 return -ENOMEM; 57 58 image->start = entry; 59 60 ret = copy_user_segment_list(image, nr_segments, segments); 61 if (ret) 62 goto out_free_image; 63 64 ret = sanity_check_segment_list(image); 65 if (ret) 66 goto out_free_image; 67 68 /* Enable the special crash kernel control page allocation policy. */ 69 if (kexec_on_panic) { 70 image->control_page = crashk_res.start; 71 image->type = KEXEC_TYPE_CRASH; 72 } 73 74 /* 75 * Find a location for the control code buffer, and add it 76 * the vector of segments so that it's pages will also be 77 * counted as destination pages. 78 */ 79 ret = -ENOMEM; 80 image->control_code_page = kimage_alloc_control_pages(image, 81 get_order(KEXEC_CONTROL_PAGE_SIZE)); 82 if (!image->control_code_page) { 83 pr_err("Could not allocate control_code_buffer\n"); 84 goto out_free_image; 85 } 86 87 if (!kexec_on_panic) { 88 image->swap_page = kimage_alloc_control_pages(image, 0); 89 if (!image->swap_page) { 90 pr_err("Could not allocate swap buffer\n"); 91 goto out_free_control_pages; 92 } 93 } 94 95 *rimage = image; 96 return 0; 97 out_free_control_pages: 98 kimage_free_page_list(&image->control_pages); 99 out_free_image: 100 kfree(image); 101 return ret; 102 } 103 104 /* 105 * Exec Kernel system call: for obvious reasons only root may call it. 106 * 107 * This call breaks up into three pieces. 108 * - A generic part which loads the new kernel from the current 109 * address space, and very carefully places the data in the 110 * allocated pages. 111 * 112 * - A generic part that interacts with the kernel and tells all of 113 * the devices to shut down. Preventing on-going dmas, and placing 114 * the devices in a consistent state so a later kernel can 115 * reinitialize them. 116 * 117 * - A machine specific part that includes the syscall number 118 * and then copies the image to it's final destination. And 119 * jumps into the image at entry. 120 * 121 * kexec does not sync, or unmount filesystems so if you need 122 * that to happen you need to do that yourself. 123 */ 124 125 SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments, 126 struct kexec_segment __user *, segments, unsigned long, flags) 127 { 128 struct kimage **dest_image, *image; 129 int result; 130 131 /* We only trust the superuser with rebooting the system. */ 132 if (!capable(CAP_SYS_BOOT) || kexec_load_disabled) 133 return -EPERM; 134 135 /* 136 * Verify we have a legal set of flags 137 * This leaves us room for future extensions. 138 */ 139 if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK)) 140 return -EINVAL; 141 142 /* Verify we are on the appropriate architecture */ 143 if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) && 144 ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT)) 145 return -EINVAL; 146 147 /* Put an artificial cap on the number 148 * of segments passed to kexec_load. 149 */ 150 if (nr_segments > KEXEC_SEGMENT_MAX) 151 return -EINVAL; 152 153 image = NULL; 154 result = 0; 155 156 /* Because we write directly to the reserved memory 157 * region when loading crash kernels we need a mutex here to 158 * prevent multiple crash kernels from attempting to load 159 * simultaneously, and to prevent a crash kernel from loading 160 * over the top of a in use crash kernel. 161 * 162 * KISS: always take the mutex. 163 */ 164 if (!mutex_trylock(&kexec_mutex)) 165 return -EBUSY; 166 167 dest_image = &kexec_image; 168 if (flags & KEXEC_ON_CRASH) 169 dest_image = &kexec_crash_image; 170 if (nr_segments > 0) { 171 unsigned long i; 172 173 if (flags & KEXEC_ON_CRASH) { 174 /* 175 * Loading another kernel to switch to if this one 176 * crashes. Free any current crash dump kernel before 177 * we corrupt it. 178 */ 179 180 kimage_free(xchg(&kexec_crash_image, NULL)); 181 result = kimage_alloc_init(&image, entry, nr_segments, 182 segments, flags); 183 crash_map_reserved_pages(); 184 } else { 185 /* Loading another kernel to reboot into. */ 186 187 result = kimage_alloc_init(&image, entry, nr_segments, 188 segments, flags); 189 } 190 if (result) 191 goto out; 192 193 if (flags & KEXEC_PRESERVE_CONTEXT) 194 image->preserve_context = 1; 195 result = machine_kexec_prepare(image); 196 if (result) 197 goto out; 198 199 for (i = 0; i < nr_segments; i++) { 200 result = kimage_load_segment(image, &image->segment[i]); 201 if (result) 202 goto out; 203 } 204 kimage_terminate(image); 205 if (flags & KEXEC_ON_CRASH) 206 crash_unmap_reserved_pages(); 207 } 208 /* Install the new kernel, and Uninstall the old */ 209 image = xchg(dest_image, image); 210 211 out: 212 mutex_unlock(&kexec_mutex); 213 kimage_free(image); 214 215 return result; 216 } 217 218 #ifdef CONFIG_COMPAT 219 COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry, 220 compat_ulong_t, nr_segments, 221 struct compat_kexec_segment __user *, segments, 222 compat_ulong_t, flags) 223 { 224 struct compat_kexec_segment in; 225 struct kexec_segment out, __user *ksegments; 226 unsigned long i, result; 227 228 /* Don't allow clients that don't understand the native 229 * architecture to do anything. 230 */ 231 if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT) 232 return -EINVAL; 233 234 if (nr_segments > KEXEC_SEGMENT_MAX) 235 return -EINVAL; 236 237 ksegments = compat_alloc_user_space(nr_segments * sizeof(out)); 238 for (i = 0; i < nr_segments; i++) { 239 result = copy_from_user(&in, &segments[i], sizeof(in)); 240 if (result) 241 return -EFAULT; 242 243 out.buf = compat_ptr(in.buf); 244 out.bufsz = in.bufsz; 245 out.mem = in.mem; 246 out.memsz = in.memsz; 247 248 result = copy_to_user(&ksegments[i], &out, sizeof(out)); 249 if (result) 250 return -EFAULT; 251 } 252 253 return sys_kexec_load(entry, nr_segments, ksegments, flags); 254 } 255 #endif 256