1 #include <linux/module.h> 2 #include <linux/sched.h> 3 #include <linux/mutex.h> 4 #include <linux/list.h> 5 #include <linux/stringify.h> 6 #include <linux/kprobes.h> 7 #include <linux/mm.h> 8 #include <linux/vmalloc.h> 9 #include <linux/memory.h> 10 #include <linux/stop_machine.h> 11 #include <linux/slab.h> 12 #include <asm/alternative.h> 13 #include <asm/sections.h> 14 #include <asm/pgtable.h> 15 #include <asm/mce.h> 16 #include <asm/nmi.h> 17 #include <asm/vsyscall.h> 18 #include <asm/cacheflush.h> 19 #include <asm/tlbflush.h> 20 #include <asm/io.h> 21 #include <asm/fixmap.h> 22 23 #define MAX_PATCH_LEN (255-1) 24 25 #ifdef CONFIG_HOTPLUG_CPU 26 static int smp_alt_once; 27 28 static int __init bootonly(char *str) 29 { 30 smp_alt_once = 1; 31 return 1; 32 } 33 __setup("smp-alt-boot", bootonly); 34 #else 35 #define smp_alt_once 1 36 #endif 37 38 static int __initdata_or_module debug_alternative; 39 40 static int __init debug_alt(char *str) 41 { 42 debug_alternative = 1; 43 return 1; 44 } 45 __setup("debug-alternative", debug_alt); 46 47 static int noreplace_smp; 48 49 static int __init setup_noreplace_smp(char *str) 50 { 51 noreplace_smp = 1; 52 return 1; 53 } 54 __setup("noreplace-smp", setup_noreplace_smp); 55 56 #ifdef CONFIG_PARAVIRT 57 static int __initdata_or_module noreplace_paravirt = 0; 58 59 static int __init setup_noreplace_paravirt(char *str) 60 { 61 noreplace_paravirt = 1; 62 return 1; 63 } 64 __setup("noreplace-paravirt", setup_noreplace_paravirt); 65 #endif 66 67 #define DPRINTK(fmt, args...) if (debug_alternative) \ 68 printk(KERN_DEBUG fmt, args) 69 70 #if defined(GENERIC_NOP1) && !defined(CONFIG_X86_64) 71 /* Use inline assembly to define this because the nops are defined 72 as inline assembly strings in the include files and we cannot 73 get them easily into strings. */ 74 asm("\t" __stringify(__INITRODATA_OR_MODULE) "\nintelnops: " 75 GENERIC_NOP1 GENERIC_NOP2 GENERIC_NOP3 GENERIC_NOP4 GENERIC_NOP5 GENERIC_NOP6 76 GENERIC_NOP7 GENERIC_NOP8 77 "\t.previous"); 78 extern const unsigned char intelnops[]; 79 static const unsigned char *const __initconst_or_module 80 intel_nops[ASM_NOP_MAX+1] = { 81 NULL, 82 intelnops, 83 intelnops + 1, 84 intelnops + 1 + 2, 85 intelnops + 1 + 2 + 3, 86 intelnops + 1 + 2 + 3 + 4, 87 intelnops + 1 + 2 + 3 + 4 + 5, 88 intelnops + 1 + 2 + 3 + 4 + 5 + 6, 89 intelnops + 1 + 2 + 3 + 4 + 5 + 6 + 7, 90 }; 91 #endif 92 93 #ifdef K8_NOP1 94 asm("\t" __stringify(__INITRODATA_OR_MODULE) "\nk8nops: " 95 K8_NOP1 K8_NOP2 K8_NOP3 K8_NOP4 K8_NOP5 K8_NOP6 96 K8_NOP7 K8_NOP8 97 "\t.previous"); 98 extern const unsigned char k8nops[]; 99 static const unsigned char *const __initconst_or_module 100 k8_nops[ASM_NOP_MAX+1] = { 101 NULL, 102 k8nops, 103 k8nops + 1, 104 k8nops + 1 + 2, 105 k8nops + 1 + 2 + 3, 106 k8nops + 1 + 2 + 3 + 4, 107 k8nops + 1 + 2 + 3 + 4 + 5, 108 k8nops + 1 + 2 + 3 + 4 + 5 + 6, 109 k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7, 110 }; 111 #endif 112 113 #if defined(K7_NOP1) && !defined(CONFIG_X86_64) 114 asm("\t" __stringify(__INITRODATA_OR_MODULE) "\nk7nops: " 115 K7_NOP1 K7_NOP2 K7_NOP3 K7_NOP4 K7_NOP5 K7_NOP6 116 K7_NOP7 K7_NOP8 117 "\t.previous"); 118 extern const unsigned char k7nops[]; 119 static const unsigned char *const __initconst_or_module 120 k7_nops[ASM_NOP_MAX+1] = { 121 NULL, 122 k7nops, 123 k7nops + 1, 124 k7nops + 1 + 2, 125 k7nops + 1 + 2 + 3, 126 k7nops + 1 + 2 + 3 + 4, 127 k7nops + 1 + 2 + 3 + 4 + 5, 128 k7nops + 1 + 2 + 3 + 4 + 5 + 6, 129 k7nops + 1 + 2 + 3 + 4 + 5 + 6 + 7, 130 }; 131 #endif 132 133 #ifdef P6_NOP1 134 asm("\t" __stringify(__INITRODATA_OR_MODULE) "\np6nops: " 135 P6_NOP1 P6_NOP2 P6_NOP3 P6_NOP4 P6_NOP5 P6_NOP6 136 P6_NOP7 P6_NOP8 137 "\t.previous"); 138 extern const unsigned char p6nops[]; 139 static const unsigned char *const __initconst_or_module 140 p6_nops[ASM_NOP_MAX+1] = { 141 NULL, 142 p6nops, 143 p6nops + 1, 144 p6nops + 1 + 2, 145 p6nops + 1 + 2 + 3, 146 p6nops + 1 + 2 + 3 + 4, 147 p6nops + 1 + 2 + 3 + 4 + 5, 148 p6nops + 1 + 2 + 3 + 4 + 5 + 6, 149 p6nops + 1 + 2 + 3 + 4 + 5 + 6 + 7, 150 }; 151 #endif 152 153 #ifdef CONFIG_X86_64 154 155 extern char __vsyscall_0; 156 static const unsigned char *const *__init_or_module find_nop_table(void) 157 { 158 if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL && 159 boot_cpu_has(X86_FEATURE_NOPL)) 160 return p6_nops; 161 else 162 return k8_nops; 163 } 164 165 #else /* CONFIG_X86_64 */ 166 167 static const unsigned char *const *__init_or_module find_nop_table(void) 168 { 169 if (boot_cpu_has(X86_FEATURE_K8)) 170 return k8_nops; 171 else if (boot_cpu_has(X86_FEATURE_K7)) 172 return k7_nops; 173 else if (boot_cpu_has(X86_FEATURE_NOPL)) 174 return p6_nops; 175 else 176 return intel_nops; 177 } 178 179 #endif /* CONFIG_X86_64 */ 180 181 /* Use this to add nops to a buffer, then text_poke the whole buffer. */ 182 static void __init_or_module add_nops(void *insns, unsigned int len) 183 { 184 const unsigned char *const *noptable = find_nop_table(); 185 186 while (len > 0) { 187 unsigned int noplen = len; 188 if (noplen > ASM_NOP_MAX) 189 noplen = ASM_NOP_MAX; 190 memcpy(insns, noptable[noplen], noplen); 191 insns += noplen; 192 len -= noplen; 193 } 194 } 195 196 extern struct alt_instr __alt_instructions[], __alt_instructions_end[]; 197 extern s32 __smp_locks[], __smp_locks_end[]; 198 static void *text_poke_early(void *addr, const void *opcode, size_t len); 199 200 /* Replace instructions with better alternatives for this CPU type. 201 This runs before SMP is initialized to avoid SMP problems with 202 self modifying code. This implies that assymetric systems where 203 APs have less capabilities than the boot processor are not handled. 204 Tough. Make sure you disable such features by hand. */ 205 206 void __init_or_module apply_alternatives(struct alt_instr *start, 207 struct alt_instr *end) 208 { 209 struct alt_instr *a; 210 u8 insnbuf[MAX_PATCH_LEN]; 211 212 DPRINTK("%s: alt table %p -> %p\n", __func__, start, end); 213 for (a = start; a < end; a++) { 214 u8 *instr = a->instr; 215 BUG_ON(a->replacementlen > a->instrlen); 216 BUG_ON(a->instrlen > sizeof(insnbuf)); 217 BUG_ON(a->cpuid >= NCAPINTS*32); 218 if (!boot_cpu_has(a->cpuid)) 219 continue; 220 #ifdef CONFIG_X86_64 221 /* vsyscall code is not mapped yet. resolve it manually. */ 222 if (instr >= (u8 *)VSYSCALL_START && instr < (u8*)VSYSCALL_END) { 223 instr = __va(instr - (u8*)VSYSCALL_START + (u8*)__pa_symbol(&__vsyscall_0)); 224 DPRINTK("%s: vsyscall fixup: %p => %p\n", 225 __func__, a->instr, instr); 226 } 227 #endif 228 memcpy(insnbuf, a->replacement, a->replacementlen); 229 if (*insnbuf == 0xe8 && a->replacementlen == 5) 230 *(s32 *)(insnbuf + 1) += a->replacement - a->instr; 231 add_nops(insnbuf + a->replacementlen, 232 a->instrlen - a->replacementlen); 233 text_poke_early(instr, insnbuf, a->instrlen); 234 } 235 } 236 237 #ifdef CONFIG_SMP 238 239 static void alternatives_smp_lock(const s32 *start, const s32 *end, 240 u8 *text, u8 *text_end) 241 { 242 const s32 *poff; 243 244 mutex_lock(&text_mutex); 245 for (poff = start; poff < end; poff++) { 246 u8 *ptr = (u8 *)poff + *poff; 247 248 if (!*poff || ptr < text || ptr >= text_end) 249 continue; 250 /* turn DS segment override prefix into lock prefix */ 251 if (*ptr == 0x3e) 252 text_poke(ptr, ((unsigned char []){0xf0}), 1); 253 }; 254 mutex_unlock(&text_mutex); 255 } 256 257 static void alternatives_smp_unlock(const s32 *start, const s32 *end, 258 u8 *text, u8 *text_end) 259 { 260 const s32 *poff; 261 262 if (noreplace_smp) 263 return; 264 265 mutex_lock(&text_mutex); 266 for (poff = start; poff < end; poff++) { 267 u8 *ptr = (u8 *)poff + *poff; 268 269 if (!*poff || ptr < text || ptr >= text_end) 270 continue; 271 /* turn lock prefix into DS segment override prefix */ 272 if (*ptr == 0xf0) 273 text_poke(ptr, ((unsigned char []){0x3E}), 1); 274 }; 275 mutex_unlock(&text_mutex); 276 } 277 278 struct smp_alt_module { 279 /* what is this ??? */ 280 struct module *mod; 281 char *name; 282 283 /* ptrs to lock prefixes */ 284 const s32 *locks; 285 const s32 *locks_end; 286 287 /* .text segment, needed to avoid patching init code ;) */ 288 u8 *text; 289 u8 *text_end; 290 291 struct list_head next; 292 }; 293 static LIST_HEAD(smp_alt_modules); 294 static DEFINE_MUTEX(smp_alt); 295 static int smp_mode = 1; /* protected by smp_alt */ 296 297 void __init_or_module alternatives_smp_module_add(struct module *mod, 298 char *name, 299 void *locks, void *locks_end, 300 void *text, void *text_end) 301 { 302 struct smp_alt_module *smp; 303 304 if (noreplace_smp) 305 return; 306 307 if (smp_alt_once) { 308 if (boot_cpu_has(X86_FEATURE_UP)) 309 alternatives_smp_unlock(locks, locks_end, 310 text, text_end); 311 return; 312 } 313 314 smp = kzalloc(sizeof(*smp), GFP_KERNEL); 315 if (NULL == smp) 316 return; /* we'll run the (safe but slow) SMP code then ... */ 317 318 smp->mod = mod; 319 smp->name = name; 320 smp->locks = locks; 321 smp->locks_end = locks_end; 322 smp->text = text; 323 smp->text_end = text_end; 324 DPRINTK("%s: locks %p -> %p, text %p -> %p, name %s\n", 325 __func__, smp->locks, smp->locks_end, 326 smp->text, smp->text_end, smp->name); 327 328 mutex_lock(&smp_alt); 329 list_add_tail(&smp->next, &smp_alt_modules); 330 if (boot_cpu_has(X86_FEATURE_UP)) 331 alternatives_smp_unlock(smp->locks, smp->locks_end, 332 smp->text, smp->text_end); 333 mutex_unlock(&smp_alt); 334 } 335 336 void __init_or_module alternatives_smp_module_del(struct module *mod) 337 { 338 struct smp_alt_module *item; 339 340 if (smp_alt_once || noreplace_smp) 341 return; 342 343 mutex_lock(&smp_alt); 344 list_for_each_entry(item, &smp_alt_modules, next) { 345 if (mod != item->mod) 346 continue; 347 list_del(&item->next); 348 mutex_unlock(&smp_alt); 349 DPRINTK("%s: %s\n", __func__, item->name); 350 kfree(item); 351 return; 352 } 353 mutex_unlock(&smp_alt); 354 } 355 356 void alternatives_smp_switch(int smp) 357 { 358 struct smp_alt_module *mod; 359 360 #ifdef CONFIG_LOCKDEP 361 /* 362 * Older binutils section handling bug prevented 363 * alternatives-replacement from working reliably. 364 * 365 * If this still occurs then you should see a hang 366 * or crash shortly after this line: 367 */ 368 printk("lockdep: fixing up alternatives.\n"); 369 #endif 370 371 if (noreplace_smp || smp_alt_once) 372 return; 373 BUG_ON(!smp && (num_online_cpus() > 1)); 374 375 mutex_lock(&smp_alt); 376 377 /* 378 * Avoid unnecessary switches because it forces JIT based VMs to 379 * throw away all cached translations, which can be quite costly. 380 */ 381 if (smp == smp_mode) { 382 /* nothing */ 383 } else if (smp) { 384 printk(KERN_INFO "SMP alternatives: switching to SMP code\n"); 385 clear_cpu_cap(&boot_cpu_data, X86_FEATURE_UP); 386 clear_cpu_cap(&cpu_data(0), X86_FEATURE_UP); 387 list_for_each_entry(mod, &smp_alt_modules, next) 388 alternatives_smp_lock(mod->locks, mod->locks_end, 389 mod->text, mod->text_end); 390 } else { 391 printk(KERN_INFO "SMP alternatives: switching to UP code\n"); 392 set_cpu_cap(&boot_cpu_data, X86_FEATURE_UP); 393 set_cpu_cap(&cpu_data(0), X86_FEATURE_UP); 394 list_for_each_entry(mod, &smp_alt_modules, next) 395 alternatives_smp_unlock(mod->locks, mod->locks_end, 396 mod->text, mod->text_end); 397 } 398 smp_mode = smp; 399 mutex_unlock(&smp_alt); 400 } 401 402 /* Return 1 if the address range is reserved for smp-alternatives */ 403 int alternatives_text_reserved(void *start, void *end) 404 { 405 struct smp_alt_module *mod; 406 const s32 *poff; 407 u8 *text_start = start; 408 u8 *text_end = end; 409 410 list_for_each_entry(mod, &smp_alt_modules, next) { 411 if (mod->text > text_end || mod->text_end < text_start) 412 continue; 413 for (poff = mod->locks; poff < mod->locks_end; poff++) { 414 const u8 *ptr = (const u8 *)poff + *poff; 415 416 if (text_start <= ptr && text_end > ptr) 417 return 1; 418 } 419 } 420 421 return 0; 422 } 423 #endif 424 425 #ifdef CONFIG_PARAVIRT 426 void __init_or_module apply_paravirt(struct paravirt_patch_site *start, 427 struct paravirt_patch_site *end) 428 { 429 struct paravirt_patch_site *p; 430 char insnbuf[MAX_PATCH_LEN]; 431 432 if (noreplace_paravirt) 433 return; 434 435 for (p = start; p < end; p++) { 436 unsigned int used; 437 438 BUG_ON(p->len > MAX_PATCH_LEN); 439 /* prep the buffer with the original instructions */ 440 memcpy(insnbuf, p->instr, p->len); 441 used = pv_init_ops.patch(p->instrtype, p->clobbers, insnbuf, 442 (unsigned long)p->instr, p->len); 443 444 BUG_ON(used > p->len); 445 446 /* Pad the rest with nops */ 447 add_nops(insnbuf + used, p->len - used); 448 text_poke_early(p->instr, insnbuf, p->len); 449 } 450 } 451 extern struct paravirt_patch_site __start_parainstructions[], 452 __stop_parainstructions[]; 453 #endif /* CONFIG_PARAVIRT */ 454 455 void __init alternative_instructions(void) 456 { 457 /* The patching is not fully atomic, so try to avoid local interruptions 458 that might execute the to be patched code. 459 Other CPUs are not running. */ 460 stop_nmi(); 461 462 /* 463 * Don't stop machine check exceptions while patching. 464 * MCEs only happen when something got corrupted and in this 465 * case we must do something about the corruption. 466 * Ignoring it is worse than a unlikely patching race. 467 * Also machine checks tend to be broadcast and if one CPU 468 * goes into machine check the others follow quickly, so we don't 469 * expect a machine check to cause undue problems during to code 470 * patching. 471 */ 472 473 apply_alternatives(__alt_instructions, __alt_instructions_end); 474 475 /* switch to patch-once-at-boottime-only mode and free the 476 * tables in case we know the number of CPUs will never ever 477 * change */ 478 #ifdef CONFIG_HOTPLUG_CPU 479 if (num_possible_cpus() < 2) 480 smp_alt_once = 1; 481 #endif 482 483 #ifdef CONFIG_SMP 484 if (smp_alt_once) { 485 if (1 == num_possible_cpus()) { 486 printk(KERN_INFO "SMP alternatives: switching to UP code\n"); 487 set_cpu_cap(&boot_cpu_data, X86_FEATURE_UP); 488 set_cpu_cap(&cpu_data(0), X86_FEATURE_UP); 489 490 alternatives_smp_unlock(__smp_locks, __smp_locks_end, 491 _text, _etext); 492 } 493 } else { 494 alternatives_smp_module_add(NULL, "core kernel", 495 __smp_locks, __smp_locks_end, 496 _text, _etext); 497 498 /* Only switch to UP mode if we don't immediately boot others */ 499 if (num_present_cpus() == 1 || setup_max_cpus <= 1) 500 alternatives_smp_switch(0); 501 } 502 #endif 503 apply_paravirt(__parainstructions, __parainstructions_end); 504 505 if (smp_alt_once) 506 free_init_pages("SMP alternatives", 507 (unsigned long)__smp_locks, 508 (unsigned long)__smp_locks_end); 509 510 restart_nmi(); 511 } 512 513 /** 514 * text_poke_early - Update instructions on a live kernel at boot time 515 * @addr: address to modify 516 * @opcode: source of the copy 517 * @len: length to copy 518 * 519 * When you use this code to patch more than one byte of an instruction 520 * you need to make sure that other CPUs cannot execute this code in parallel. 521 * Also no thread must be currently preempted in the middle of these 522 * instructions. And on the local CPU you need to be protected again NMI or MCE 523 * handlers seeing an inconsistent instruction while you patch. 524 */ 525 static void *__init_or_module text_poke_early(void *addr, const void *opcode, 526 size_t len) 527 { 528 unsigned long flags; 529 local_irq_save(flags); 530 memcpy(addr, opcode, len); 531 sync_core(); 532 local_irq_restore(flags); 533 /* Could also do a CLFLUSH here to speed up CPU recovery; but 534 that causes hangs on some VIA CPUs. */ 535 return addr; 536 } 537 538 /** 539 * text_poke - Update instructions on a live kernel 540 * @addr: address to modify 541 * @opcode: source of the copy 542 * @len: length to copy 543 * 544 * Only atomic text poke/set should be allowed when not doing early patching. 545 * It means the size must be writable atomically and the address must be aligned 546 * in a way that permits an atomic write. It also makes sure we fit on a single 547 * page. 548 * 549 * Note: Must be called under text_mutex. 550 */ 551 void *__kprobes text_poke(void *addr, const void *opcode, size_t len) 552 { 553 unsigned long flags; 554 char *vaddr; 555 struct page *pages[2]; 556 int i; 557 558 if (!core_kernel_text((unsigned long)addr)) { 559 pages[0] = vmalloc_to_page(addr); 560 pages[1] = vmalloc_to_page(addr + PAGE_SIZE); 561 } else { 562 pages[0] = virt_to_page(addr); 563 WARN_ON(!PageReserved(pages[0])); 564 pages[1] = virt_to_page(addr + PAGE_SIZE); 565 } 566 BUG_ON(!pages[0]); 567 local_irq_save(flags); 568 set_fixmap(FIX_TEXT_POKE0, page_to_phys(pages[0])); 569 if (pages[1]) 570 set_fixmap(FIX_TEXT_POKE1, page_to_phys(pages[1])); 571 vaddr = (char *)fix_to_virt(FIX_TEXT_POKE0); 572 memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len); 573 clear_fixmap(FIX_TEXT_POKE0); 574 if (pages[1]) 575 clear_fixmap(FIX_TEXT_POKE1); 576 local_flush_tlb(); 577 sync_core(); 578 /* Could also do a CLFLUSH here to speed up CPU recovery; but 579 that causes hangs on some VIA CPUs. */ 580 for (i = 0; i < len; i++) 581 BUG_ON(((char *)addr)[i] != ((char *)opcode)[i]); 582 local_irq_restore(flags); 583 return addr; 584 } 585 586 /* 587 * Cross-modifying kernel text with stop_machine(). 588 * This code originally comes from immediate value. 589 */ 590 static atomic_t stop_machine_first; 591 static int wrote_text; 592 593 struct text_poke_params { 594 void *addr; 595 const void *opcode; 596 size_t len; 597 }; 598 599 static int __kprobes stop_machine_text_poke(void *data) 600 { 601 struct text_poke_params *tpp = data; 602 603 if (atomic_dec_and_test(&stop_machine_first)) { 604 text_poke(tpp->addr, tpp->opcode, tpp->len); 605 smp_wmb(); /* Make sure other cpus see that this has run */ 606 wrote_text = 1; 607 } else { 608 while (!wrote_text) 609 cpu_relax(); 610 smp_mb(); /* Load wrote_text before following execution */ 611 } 612 613 flush_icache_range((unsigned long)tpp->addr, 614 (unsigned long)tpp->addr + tpp->len); 615 return 0; 616 } 617 618 /** 619 * text_poke_smp - Update instructions on a live kernel on SMP 620 * @addr: address to modify 621 * @opcode: source of the copy 622 * @len: length to copy 623 * 624 * Modify multi-byte instruction by using stop_machine() on SMP. This allows 625 * user to poke/set multi-byte text on SMP. Only non-NMI/MCE code modifying 626 * should be allowed, since stop_machine() does _not_ protect code against 627 * NMI and MCE. 628 * 629 * Note: Must be called under get_online_cpus() and text_mutex. 630 */ 631 void *__kprobes text_poke_smp(void *addr, const void *opcode, size_t len) 632 { 633 struct text_poke_params tpp; 634 635 tpp.addr = addr; 636 tpp.opcode = opcode; 637 tpp.len = len; 638 atomic_set(&stop_machine_first, 1); 639 wrote_text = 0; 640 stop_machine(stop_machine_text_poke, (void *)&tpp, NULL); 641 return addr; 642 } 643 644