1 /* 2 * This file is subject to the terms and conditions of the GNU General Public 3 * License. See the file "COPYING" in the main directory of this archive 4 * for more details. 5 * 6 * Support for Kernel relocation at boot time 7 * 8 * Copyright (C) 2015, Imagination Technologies Ltd. 9 * Authors: Matt Redfearn (matt.redfearn@mips.com) 10 */ 11 #include <asm/bootinfo.h> 12 #include <asm/cacheflush.h> 13 #include <asm/fw/fw.h> 14 #include <asm/sections.h> 15 #include <asm/setup.h> 16 #include <asm/timex.h> 17 #include <linux/elf.h> 18 #include <linux/kernel.h> 19 #include <linux/libfdt.h> 20 #include <linux/of_fdt.h> 21 #include <linux/sched/task.h> 22 #include <linux/start_kernel.h> 23 #include <linux/string.h> 24 #include <linux/printk.h> 25 26 #define RELOCATED(x) ((void *)((long)x + offset)) 27 28 extern u32 _relocation_start[]; /* End kernel image / start relocation table */ 29 extern u32 _relocation_end[]; /* End relocation table */ 30 31 extern long __start___ex_table; /* Start exception table */ 32 extern long __stop___ex_table; /* End exception table */ 33 34 extern void __weak plat_fdt_relocated(void *new_location); 35 36 /* 37 * This function may be defined for a platform to perform any post-relocation 38 * fixup necessary. 39 * Return non-zero to abort relocation 40 */ 41 int __weak plat_post_relocation(long offset) 42 { 43 return 0; 44 } 45 46 static inline u32 __init get_synci_step(void) 47 { 48 u32 res; 49 50 __asm__("rdhwr %0, $1" : "=r" (res)); 51 52 return res; 53 } 54 55 static void __init sync_icache(void *kbase, unsigned long kernel_length) 56 { 57 void *kend = kbase + kernel_length; 58 u32 step = get_synci_step(); 59 60 do { 61 __asm__ __volatile__( 62 "synci 0(%0)" 63 : /* no output */ 64 : "r" (kbase)); 65 66 kbase += step; 67 } while (step && kbase < kend); 68 69 /* Completion barrier */ 70 __sync(); 71 } 72 73 static void __init apply_r_mips_64_rel(u32 *loc_new, long offset) 74 { 75 *(u64 *)loc_new += offset; 76 } 77 78 static void __init apply_r_mips_32_rel(u32 *loc_new, long offset) 79 { 80 *loc_new += offset; 81 } 82 83 static int __init apply_r_mips_26_rel(u32 *loc_orig, u32 *loc_new, long offset) 84 { 85 unsigned long target_addr = (*loc_orig) & 0x03ffffff; 86 87 if (offset % 4) { 88 pr_err("Dangerous R_MIPS_26 REL relocation\n"); 89 return -ENOEXEC; 90 } 91 92 /* Original target address */ 93 target_addr <<= 2; 94 target_addr += (unsigned long)loc_orig & 0xf0000000; 95 96 /* Get the new target address */ 97 target_addr += offset; 98 99 if ((target_addr & 0xf0000000) != ((unsigned long)loc_new & 0xf0000000)) { 100 pr_err("R_MIPS_26 REL relocation overflow\n"); 101 return -ENOEXEC; 102 } 103 104 target_addr -= (unsigned long)loc_new & 0xf0000000; 105 target_addr >>= 2; 106 107 *loc_new = (*loc_new & ~0x03ffffff) | (target_addr & 0x03ffffff); 108 109 return 0; 110 } 111 112 113 static void __init apply_r_mips_hi16_rel(u32 *loc_orig, u32 *loc_new, 114 long offset) 115 { 116 unsigned long insn = *loc_orig; 117 unsigned long target = (insn & 0xffff) << 16; /* high 16bits of target */ 118 119 target += offset; 120 121 *loc_new = (insn & ~0xffff) | ((target >> 16) & 0xffff); 122 } 123 124 static int __init reloc_handler(u32 type, u32 *loc_orig, u32 *loc_new, 125 long offset) 126 { 127 switch (type) { 128 case R_MIPS_64: 129 apply_r_mips_64_rel(loc_new, offset); 130 break; 131 case R_MIPS_32: 132 apply_r_mips_32_rel(loc_new, offset); 133 break; 134 case R_MIPS_26: 135 return apply_r_mips_26_rel(loc_orig, loc_new, offset); 136 case R_MIPS_HI16: 137 apply_r_mips_hi16_rel(loc_orig, loc_new, offset); 138 break; 139 default: 140 pr_err("Unhandled relocation type %d at 0x%pK\n", type, 141 loc_orig); 142 return -ENOEXEC; 143 } 144 145 return 0; 146 } 147 148 static int __init do_relocations(void *kbase_old, void *kbase_new, long offset) 149 { 150 u32 *r; 151 u32 *loc_orig; 152 u32 *loc_new; 153 int type; 154 int res; 155 156 for (r = _relocation_start; r < _relocation_end; r++) { 157 /* Sentinel for last relocation */ 158 if (*r == 0) 159 break; 160 161 type = (*r >> 24) & 0xff; 162 loc_orig = kbase_old + ((*r & 0x00ffffff) << 2); 163 loc_new = RELOCATED(loc_orig); 164 165 res = reloc_handler(type, loc_orig, loc_new, offset); 166 if (res) 167 return res; 168 } 169 170 return 0; 171 } 172 173 /* 174 * The exception table is filled in by the relocs tool after vmlinux is linked. 175 * It must be relocated separately since there will not be any relocation 176 * information for it filled in by the linker. 177 */ 178 static int __init relocate_exception_table(long offset) 179 { 180 unsigned long *etable_start, *etable_end, *e; 181 182 etable_start = RELOCATED(&__start___ex_table); 183 etable_end = RELOCATED(&__stop___ex_table); 184 185 for (e = etable_start; e < etable_end; e++) 186 *e += offset; 187 188 return 0; 189 } 190 191 #ifdef CONFIG_RANDOMIZE_BASE 192 193 static inline __init unsigned long rotate_xor(unsigned long hash, 194 const void *area, size_t size) 195 { 196 size_t i; 197 unsigned long *ptr = (unsigned long *)area; 198 199 for (i = 0; i < size / sizeof(hash); i++) { 200 /* Rotate by odd number of bits and XOR. */ 201 hash = (hash << ((sizeof(hash) * 8) - 7)) | (hash >> 7); 202 hash ^= ptr[i]; 203 } 204 205 return hash; 206 } 207 208 static inline __init unsigned long get_random_boot(void) 209 { 210 unsigned long entropy = random_get_entropy(); 211 unsigned long hash = 0; 212 213 /* Attempt to create a simple but unpredictable starting entropy. */ 214 hash = rotate_xor(hash, linux_banner, strlen(linux_banner)); 215 216 /* Add in any runtime entropy we can get */ 217 hash = rotate_xor(hash, &entropy, sizeof(entropy)); 218 219 #if defined(CONFIG_USE_OF) 220 /* Get any additional entropy passed in device tree */ 221 if (initial_boot_params) { 222 int node, len; 223 u64 *prop; 224 225 node = fdt_path_offset(initial_boot_params, "/chosen"); 226 if (node >= 0) { 227 prop = fdt_getprop_w(initial_boot_params, node, 228 "kaslr-seed", &len); 229 if (prop && (len == sizeof(u64))) 230 hash = rotate_xor(hash, prop, sizeof(*prop)); 231 } 232 } 233 #endif /* CONFIG_USE_OF */ 234 235 return hash; 236 } 237 238 static inline __init bool kaslr_disabled(void) 239 { 240 char *str; 241 242 #if defined(CONFIG_CMDLINE_BOOL) 243 const char *builtin_cmdline = CONFIG_CMDLINE; 244 245 str = strstr(builtin_cmdline, "nokaslr"); 246 if (str == builtin_cmdline || 247 (str > builtin_cmdline && *(str - 1) == ' ')) 248 return true; 249 #endif 250 str = strstr(arcs_cmdline, "nokaslr"); 251 if (str == arcs_cmdline || (str > arcs_cmdline && *(str - 1) == ' ')) 252 return true; 253 254 return false; 255 } 256 257 static inline void __init *determine_relocation_address(void) 258 { 259 /* Choose a new address for the kernel */ 260 unsigned long kernel_length; 261 void *dest = &_text; 262 unsigned long offset; 263 264 if (kaslr_disabled()) 265 return dest; 266 267 kernel_length = (long)_end - (long)(&_text); 268 269 offset = get_random_boot() << 16; 270 offset &= (CONFIG_RANDOMIZE_BASE_MAX_OFFSET - 1); 271 if (offset < kernel_length) 272 offset += ALIGN(kernel_length, 0xffff); 273 274 return RELOCATED(dest); 275 } 276 277 #else 278 279 static inline void __init *determine_relocation_address(void) 280 { 281 /* 282 * Choose a new address for the kernel 283 * For now we'll hard code the destination 284 */ 285 return (void *)0xffffffff81000000; 286 } 287 288 #endif 289 290 static inline int __init relocation_addr_valid(void *loc_new) 291 { 292 if ((unsigned long)loc_new & 0x0000ffff) { 293 /* Inappropriately aligned new location */ 294 return 0; 295 } 296 if ((unsigned long)loc_new < (unsigned long)&_end) { 297 /* New location overlaps original kernel */ 298 return 0; 299 } 300 return 1; 301 } 302 303 #if defined(CONFIG_USE_OF) 304 void __weak *plat_get_fdt(void) 305 { 306 return NULL; 307 } 308 #endif 309 310 void *__init relocate_kernel(void) 311 { 312 void *loc_new; 313 unsigned long kernel_length; 314 unsigned long bss_length; 315 long offset = 0; 316 int res = 1; 317 /* Default to original kernel entry point */ 318 void *kernel_entry = start_kernel; 319 void *fdt = NULL; 320 321 /* Get the command line */ 322 fw_init_cmdline(); 323 #if defined(CONFIG_USE_OF) 324 /* Deal with the device tree */ 325 fdt = plat_get_fdt(); 326 early_init_dt_scan(fdt); 327 if (boot_command_line[0]) { 328 /* Boot command line was passed in device tree */ 329 strlcpy(arcs_cmdline, boot_command_line, COMMAND_LINE_SIZE); 330 } 331 #endif /* CONFIG_USE_OF */ 332 333 kernel_length = (long)(&_relocation_start) - (long)(&_text); 334 bss_length = (long)&__bss_stop - (long)&__bss_start; 335 336 loc_new = determine_relocation_address(); 337 338 /* Sanity check relocation address */ 339 if (relocation_addr_valid(loc_new)) 340 offset = (unsigned long)loc_new - (unsigned long)(&_text); 341 342 /* Reset the command line now so we don't end up with a duplicate */ 343 arcs_cmdline[0] = '\0'; 344 345 if (offset) { 346 void (*fdt_relocated_)(void *) = NULL; 347 #if defined(CONFIG_USE_OF) 348 unsigned long fdt_phys = virt_to_phys(fdt); 349 350 /* 351 * If built-in dtb is used then it will have been relocated 352 * during kernel _text relocation. If appended DTB is used 353 * then it will not be relocated, but it should remain 354 * intact in the original location. If dtb is loaded by 355 * the bootloader then it may need to be moved if it crosses 356 * the target memory area 357 */ 358 359 if (fdt_phys >= virt_to_phys(RELOCATED(&_text)) && 360 fdt_phys <= virt_to_phys(RELOCATED(&_end))) { 361 void *fdt_relocated = 362 RELOCATED(ALIGN((long)&_end, PAGE_SIZE)); 363 memcpy(fdt_relocated, fdt, fdt_totalsize(fdt)); 364 fdt = fdt_relocated; 365 fdt_relocated_ = RELOCATED(&plat_fdt_relocated); 366 } 367 #endif /* CONFIG_USE_OF */ 368 369 /* Copy the kernel to it's new location */ 370 memcpy(loc_new, &_text, kernel_length); 371 372 /* Perform relocations on the new kernel */ 373 res = do_relocations(&_text, loc_new, offset); 374 if (res < 0) 375 goto out; 376 377 /* Sync the caches ready for execution of new kernel */ 378 sync_icache(loc_new, kernel_length); 379 380 res = relocate_exception_table(offset); 381 if (res < 0) 382 goto out; 383 384 /* 385 * The original .bss has already been cleared, and 386 * some variables such as command line parameters 387 * stored to it so make a copy in the new location. 388 */ 389 memcpy(RELOCATED(&__bss_start), &__bss_start, bss_length); 390 391 /* 392 * If fdt was stored outside of the kernel image and 393 * had to be moved then update platform's state data 394 * with the new fdt location 395 */ 396 if (fdt_relocated_) 397 fdt_relocated_(fdt); 398 399 /* 400 * Last chance for the platform to abort relocation. 401 * This may also be used by the platform to perform any 402 * initialisation required now that the new kernel is 403 * resident in memory and ready to be executed. 404 */ 405 if (plat_post_relocation(offset)) 406 goto out; 407 408 /* The current thread is now within the relocated image */ 409 __current_thread_info = RELOCATED(&init_thread_union); 410 411 /* Return the new kernel's entry point */ 412 kernel_entry = RELOCATED(start_kernel); 413 } 414 out: 415 return kernel_entry; 416 } 417 418 /* 419 * Show relocation information on panic. 420 */ 421 static void show_kernel_relocation(const char *level) 422 { 423 unsigned long offset; 424 425 offset = __pa_symbol(_text) - __pa_symbol(VMLINUX_LOAD_ADDRESS); 426 427 if (IS_ENABLED(CONFIG_RELOCATABLE) && offset > 0) { 428 printk(level); 429 pr_cont("Kernel relocated by 0x%pK\n", (void *)offset); 430 pr_cont(" .text @ 0x%pK\n", _text); 431 pr_cont(" .data @ 0x%pK\n", _sdata); 432 pr_cont(" .bss @ 0x%pK\n", __bss_start); 433 } 434 } 435 436 static int kernel_location_notifier_fn(struct notifier_block *self, 437 unsigned long v, void *p) 438 { 439 show_kernel_relocation(KERN_EMERG); 440 return NOTIFY_DONE; 441 } 442 443 static struct notifier_block kernel_location_notifier = { 444 .notifier_call = kernel_location_notifier_fn 445 }; 446 447 static int __init register_kernel_offset_dumper(void) 448 { 449 atomic_notifier_chain_register(&panic_notifier_list, 450 &kernel_location_notifier); 451 return 0; 452 } 453 __initcall(register_kernel_offset_dumper); 454