1#define pr_fmt(fmt) "SMP alternatives: " fmt 2 3#include <linux/module.h> 4#include <linux/sched.h> 5#include <linux/mutex.h> 6#include <linux/list.h> 7#include <linux/stringify.h> 8#include <linux/mm.h> 9#include <linux/vmalloc.h> 10#include <linux/memory.h> 11#include <linux/stop_machine.h> 12#include <linux/slab.h> 13#include <linux/kdebug.h> 14#include <asm/alternative.h> 15#include <asm/sections.h> 16#include <asm/pgtable.h> 17#include <asm/mce.h> 18#include <asm/nmi.h> 19#include <asm/cacheflush.h> 20#include <asm/tlbflush.h> 21#include <asm/io.h> 22#include <asm/fixmap.h> 23 24#define MAX_PATCH_LEN (255-1) 25 26static int __initdata_or_module debug_alternative; 27 28static int __init debug_alt(char *str) 29{ 30 debug_alternative = 1; 31 return 1; 32} 33__setup("debug-alternative", debug_alt); 34 35static int noreplace_smp; 36 37static int __init setup_noreplace_smp(char *str) 38{ 39 noreplace_smp = 1; 40 return 1; 41} 42__setup("noreplace-smp", setup_noreplace_smp); 43 44#ifdef CONFIG_PARAVIRT 45static int __initdata_or_module noreplace_paravirt = 0; 46 47static int __init setup_noreplace_paravirt(char *str) 48{ 49 noreplace_paravirt = 1; 50 return 1; 51} 52__setup("noreplace-paravirt", setup_noreplace_paravirt); 53#endif 54 55#define DPRINTK(fmt, args...) \ 56do { \ 57 if (debug_alternative) \ 58 printk(KERN_DEBUG "%s: " fmt "\n", __func__, ##args); \ 59} while (0) 60 61#define DUMP_BYTES(buf, len, fmt, args...) \ 62do { \ 63 if (unlikely(debug_alternative)) { \ 64 int j; \ 65 \ 66 if (!(len)) \ 67 break; \ 68 \ 69 printk(KERN_DEBUG fmt, ##args); \ 70 for (j = 0; j < (len) - 1; j++) \ 71 printk(KERN_CONT "%02hhx ", buf[j]); \ 72 printk(KERN_CONT "%02hhx\n", buf[j]); \ 73 } \ 74} while (0) 75 76/* 77 * Each GENERIC_NOPX is of X bytes, and defined as an array of bytes 78 * that correspond to that nop. Getting from one nop to the next, we 79 * add to the array the offset that is equal to the sum of all sizes of 80 * nops preceding the one we are after. 81 * 82 * Note: The GENERIC_NOP5_ATOMIC is at the end, as it breaks the 83 * nice symmetry of sizes of the previous nops. 84 */ 85#if defined(GENERIC_NOP1) && !defined(CONFIG_X86_64) 86static const unsigned char intelnops[] = 87{ 88 GENERIC_NOP1, 89 GENERIC_NOP2, 90 GENERIC_NOP3, 91 GENERIC_NOP4, 92 GENERIC_NOP5, 93 GENERIC_NOP6, 94 GENERIC_NOP7, 95 GENERIC_NOP8, 96 GENERIC_NOP5_ATOMIC 97}; 98static const unsigned char * const intel_nops[ASM_NOP_MAX+2] = 99{ 100 NULL, 101 intelnops, 102 intelnops + 1, 103 intelnops + 1 + 2, 104 intelnops + 1 + 2 + 3, 105 intelnops + 1 + 2 + 3 + 4, 106 intelnops + 1 + 2 + 3 + 4 + 5, 107 intelnops + 1 + 2 + 3 + 4 + 5 + 6, 108 intelnops + 1 + 2 + 3 + 4 + 5 + 6 + 7, 109 intelnops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8, 110}; 111#endif 112 113#ifdef K8_NOP1 114static const unsigned char k8nops[] = 115{ 116 K8_NOP1, 117 K8_NOP2, 118 K8_NOP3, 119 K8_NOP4, 120 K8_NOP5, 121 K8_NOP6, 122 K8_NOP7, 123 K8_NOP8, 124 K8_NOP5_ATOMIC 125}; 126static const unsigned char * const k8_nops[ASM_NOP_MAX+2] = 127{ 128 NULL, 129 k8nops, 130 k8nops + 1, 131 k8nops + 1 + 2, 132 k8nops + 1 + 2 + 3, 133 k8nops + 1 + 2 + 3 + 4, 134 k8nops + 1 + 2 + 3 + 4 + 5, 135 k8nops + 1 + 2 + 3 + 4 + 5 + 6, 136 k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7, 137 k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8, 138}; 139#endif 140 141#if defined(K7_NOP1) && !defined(CONFIG_X86_64) 142static const unsigned char k7nops[] = 143{ 144 K7_NOP1, 145 K7_NOP2, 146 K7_NOP3, 147 K7_NOP4, 148 K7_NOP5, 149 K7_NOP6, 150 K7_NOP7, 151 K7_NOP8, 152 K7_NOP5_ATOMIC 153}; 154static const unsigned char * const k7_nops[ASM_NOP_MAX+2] = 155{ 156 NULL, 157 k7nops, 158 k7nops + 1, 159 k7nops + 1 + 2, 160 k7nops + 1 + 2 + 3, 161 k7nops + 1 + 2 + 3 + 4, 162 k7nops + 1 + 2 + 3 + 4 + 5, 163 k7nops + 1 + 2 + 3 + 4 + 5 + 6, 164 k7nops + 1 + 2 + 3 + 4 + 5 + 6 + 7, 165 k7nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8, 166}; 167#endif 168 169#ifdef P6_NOP1 170static const unsigned char p6nops[] = 171{ 172 P6_NOP1, 173 P6_NOP2, 174 P6_NOP3, 175 P6_NOP4, 176 P6_NOP5, 177 P6_NOP6, 178 P6_NOP7, 179 P6_NOP8, 180 P6_NOP5_ATOMIC 181}; 182static const unsigned char * const p6_nops[ASM_NOP_MAX+2] = 183{ 184 NULL, 185 p6nops, 186 p6nops + 1, 187 p6nops + 1 + 2, 188 p6nops + 1 + 2 + 3, 189 p6nops + 1 + 2 + 3 + 4, 190 p6nops + 1 + 2 + 3 + 4 + 5, 191 p6nops + 1 + 2 + 3 + 4 + 5 + 6, 192 p6nops + 1 + 2 + 3 + 4 + 5 + 6 + 7, 193 p6nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8, 194}; 195#endif 196 197/* Initialize these to a safe default */ 198#ifdef CONFIG_X86_64 199const unsigned char * const *ideal_nops = p6_nops; 200#else 201const unsigned char * const *ideal_nops = intel_nops; 202#endif 203 204void __init arch_init_ideal_nops(void) 205{ 206 switch (boot_cpu_data.x86_vendor) { 207 case X86_VENDOR_INTEL: 208 /* 209 * Due to a decoder implementation quirk, some 210 * specific Intel CPUs actually perform better with 211 * the "k8_nops" than with the SDM-recommended NOPs. 212 */ 213 if (boot_cpu_data.x86 == 6 && 214 boot_cpu_data.x86_model >= 0x0f && 215 boot_cpu_data.x86_model != 0x1c && 216 boot_cpu_data.x86_model != 0x26 && 217 boot_cpu_data.x86_model != 0x27 && 218 boot_cpu_data.x86_model < 0x30) { 219 ideal_nops = k8_nops; 220 } else if (boot_cpu_has(X86_FEATURE_NOPL)) { 221 ideal_nops = p6_nops; 222 } else { 223#ifdef CONFIG_X86_64 224 ideal_nops = k8_nops; 225#else 226 ideal_nops = intel_nops; 227#endif 228 } 229 break; 230 default: 231#ifdef CONFIG_X86_64 232 ideal_nops = k8_nops; 233#else 234 if (boot_cpu_has(X86_FEATURE_K8)) 235 ideal_nops = k8_nops; 236 else if (boot_cpu_has(X86_FEATURE_K7)) 237 ideal_nops = k7_nops; 238 else 239 ideal_nops = intel_nops; 240#endif 241 } 242} 243 244/* Use this to add nops to a buffer, then text_poke the whole buffer. */ 245static void __init_or_module add_nops(void *insns, unsigned int len) 246{ 247 while (len > 0) { 248 unsigned int noplen = len; 249 if (noplen > ASM_NOP_MAX) 250 noplen = ASM_NOP_MAX; 251 memcpy(insns, ideal_nops[noplen], noplen); 252 insns += noplen; 253 len -= noplen; 254 } 255} 256 257extern struct alt_instr __alt_instructions[], __alt_instructions_end[]; 258extern s32 __smp_locks[], __smp_locks_end[]; 259void *text_poke_early(void *addr, const void *opcode, size_t len); 260 261/* 262 * Are we looking at a near JMP with a 1 or 4-byte displacement. 263 */ 264static inline bool is_jmp(const u8 opcode) 265{ 266 return opcode == 0xeb || opcode == 0xe9; 267} 268 269static void __init_or_module 270recompute_jump(struct alt_instr *a, u8 *orig_insn, u8 *repl_insn, u8 *insnbuf) 271{ 272 u8 *next_rip, *tgt_rip; 273 s32 n_dspl, o_dspl; 274 int repl_len; 275 276 if (a->replacementlen != 5) 277 return; 278 279 o_dspl = *(s32 *)(insnbuf + 1); 280 281 /* next_rip of the replacement JMP */ 282 next_rip = repl_insn + a->replacementlen; 283 /* target rip of the replacement JMP */ 284 tgt_rip = next_rip + o_dspl; 285 n_dspl = tgt_rip - orig_insn; 286 287 DPRINTK("target RIP: %p, new_displ: 0x%x", tgt_rip, n_dspl); 288 289 if (tgt_rip - orig_insn >= 0) { 290 if (n_dspl - 2 <= 127) 291 goto two_byte_jmp; 292 else 293 goto five_byte_jmp; 294 /* negative offset */ 295 } else { 296 if (((n_dspl - 2) & 0xff) == (n_dspl - 2)) 297 goto two_byte_jmp; 298 else 299 goto five_byte_jmp; 300 } 301 302two_byte_jmp: 303 n_dspl -= 2; 304 305 insnbuf[0] = 0xeb; 306 insnbuf[1] = (s8)n_dspl; 307 add_nops(insnbuf + 2, 3); 308 309 repl_len = 2; 310 goto done; 311 312five_byte_jmp: 313 n_dspl -= 5; 314 315 insnbuf[0] = 0xe9; 316 *(s32 *)&insnbuf[1] = n_dspl; 317 318 repl_len = 5; 319 320done: 321 322 DPRINTK("final displ: 0x%08x, JMP 0x%lx", 323 n_dspl, (unsigned long)orig_insn + n_dspl + repl_len); 324} 325 326static void __init_or_module optimize_nops(struct alt_instr *a, u8 *instr) 327{ 328 unsigned long flags; 329 330 if (instr[0] != 0x90) 331 return; 332 333 local_irq_save(flags); 334 add_nops(instr + (a->instrlen - a->padlen), a->padlen); 335 sync_core(); 336 local_irq_restore(flags); 337 338 DUMP_BYTES(instr, a->instrlen, "%p: [%d:%d) optimized NOPs: ", 339 instr, a->instrlen - a->padlen, a->padlen); 340} 341 342/* 343 * Replace instructions with better alternatives for this CPU type. This runs 344 * before SMP is initialized to avoid SMP problems with self modifying code. 345 * This implies that asymmetric systems where APs have less capabilities than 346 * the boot processor are not handled. Tough. Make sure you disable such 347 * features by hand. 348 */ 349void __init_or_module apply_alternatives(struct alt_instr *start, 350 struct alt_instr *end) 351{ 352 struct alt_instr *a; 353 u8 *instr, *replacement; 354 u8 insnbuf[MAX_PATCH_LEN]; 355 356 DPRINTK("alt table %p -> %p", start, end); 357 /* 358 * The scan order should be from start to end. A later scanned 359 * alternative code can overwrite previously scanned alternative code. 360 * Some kernel functions (e.g. memcpy, memset, etc) use this order to 361 * patch code. 362 * 363 * So be careful if you want to change the scan order to any other 364 * order. 365 */ 366 for (a = start; a < end; a++) { 367 int insnbuf_sz = 0; 368 369 instr = (u8 *)&a->instr_offset + a->instr_offset; 370 replacement = (u8 *)&a->repl_offset + a->repl_offset; 371 BUG_ON(a->instrlen > sizeof(insnbuf)); 372 BUG_ON(a->cpuid >= (NCAPINTS + NBUGINTS) * 32); 373 if (!boot_cpu_has(a->cpuid)) { 374 if (a->padlen > 1) 375 optimize_nops(a, instr); 376 377 continue; 378 } 379 380 DPRINTK("feat: %d*32+%d, old: (%p, len: %d), repl: (%p, len: %d), pad: %d", 381 a->cpuid >> 5, 382 a->cpuid & 0x1f, 383 instr, a->instrlen, 384 replacement, a->replacementlen, a->padlen); 385 386 DUMP_BYTES(instr, a->instrlen, "%p: old_insn: ", instr); 387 DUMP_BYTES(replacement, a->replacementlen, "%p: rpl_insn: ", replacement); 388 389 memcpy(insnbuf, replacement, a->replacementlen); 390 insnbuf_sz = a->replacementlen; 391 392 /* 0xe8 is a relative jump; fix the offset. */ 393 if (*insnbuf == 0xe8 && a->replacementlen == 5) { 394 *(s32 *)(insnbuf + 1) += replacement - instr; 395 DPRINTK("Fix CALL offset: 0x%x, CALL 0x%lx", 396 *(s32 *)(insnbuf + 1), 397 (unsigned long)instr + *(s32 *)(insnbuf + 1) + 5); 398 } 399 400 if (a->replacementlen && is_jmp(replacement[0])) 401 recompute_jump(a, instr, replacement, insnbuf); 402 403 if (a->instrlen > a->replacementlen) { 404 add_nops(insnbuf + a->replacementlen, 405 a->instrlen - a->replacementlen); 406 insnbuf_sz += a->instrlen - a->replacementlen; 407 } 408 DUMP_BYTES(insnbuf, insnbuf_sz, "%p: final_insn: ", instr); 409 410 text_poke_early(instr, insnbuf, insnbuf_sz); 411 } 412} 413 414#ifdef CONFIG_SMP 415static void alternatives_smp_lock(const s32 *start, const s32 *end, 416 u8 *text, u8 *text_end) 417{ 418 const s32 *poff; 419 420 mutex_lock(&text_mutex); 421 for (poff = start; poff < end; poff++) { 422 u8 *ptr = (u8 *)poff + *poff; 423 424 if (!*poff || ptr < text || ptr >= text_end) 425 continue; 426 /* turn DS segment override prefix into lock prefix */ 427 if (*ptr == 0x3e) 428 text_poke(ptr, ((unsigned char []){0xf0}), 1); 429 } 430 mutex_unlock(&text_mutex); 431} 432 433static void alternatives_smp_unlock(const s32 *start, const s32 *end, 434 u8 *text, u8 *text_end) 435{ 436 const s32 *poff; 437 438 mutex_lock(&text_mutex); 439 for (poff = start; poff < end; poff++) { 440 u8 *ptr = (u8 *)poff + *poff; 441 442 if (!*poff || ptr < text || ptr >= text_end) 443 continue; 444 /* turn lock prefix into DS segment override prefix */ 445 if (*ptr == 0xf0) 446 text_poke(ptr, ((unsigned char []){0x3E}), 1); 447 } 448 mutex_unlock(&text_mutex); 449} 450 451struct smp_alt_module { 452 /* what is this ??? */ 453 struct module *mod; 454 char *name; 455 456 /* ptrs to lock prefixes */ 457 const s32 *locks; 458 const s32 *locks_end; 459 460 /* .text segment, needed to avoid patching init code ;) */ 461 u8 *text; 462 u8 *text_end; 463 464 struct list_head next; 465}; 466static LIST_HEAD(smp_alt_modules); 467static DEFINE_MUTEX(smp_alt); 468static bool uniproc_patched = false; /* protected by smp_alt */ 469 470void __init_or_module alternatives_smp_module_add(struct module *mod, 471 char *name, 472 void *locks, void *locks_end, 473 void *text, void *text_end) 474{ 475 struct smp_alt_module *smp; 476 477 mutex_lock(&smp_alt); 478 if (!uniproc_patched) 479 goto unlock; 480 481 if (num_possible_cpus() == 1) 482 /* Don't bother remembering, we'll never have to undo it. */ 483 goto smp_unlock; 484 485 smp = kzalloc(sizeof(*smp), GFP_KERNEL); 486 if (NULL == smp) 487 /* we'll run the (safe but slow) SMP code then ... */ 488 goto unlock; 489 490 smp->mod = mod; 491 smp->name = name; 492 smp->locks = locks; 493 smp->locks_end = locks_end; 494 smp->text = text; 495 smp->text_end = text_end; 496 DPRINTK("locks %p -> %p, text %p -> %p, name %s\n", 497 smp->locks, smp->locks_end, 498 smp->text, smp->text_end, smp->name); 499 500 list_add_tail(&smp->next, &smp_alt_modules); 501smp_unlock: 502 alternatives_smp_unlock(locks, locks_end, text, text_end); 503unlock: 504 mutex_unlock(&smp_alt); 505} 506 507void __init_or_module alternatives_smp_module_del(struct module *mod) 508{ 509 struct smp_alt_module *item; 510 511 mutex_lock(&smp_alt); 512 list_for_each_entry(item, &smp_alt_modules, next) { 513 if (mod != item->mod) 514 continue; 515 list_del(&item->next); 516 kfree(item); 517 break; 518 } 519 mutex_unlock(&smp_alt); 520} 521 522void alternatives_enable_smp(void) 523{ 524 struct smp_alt_module *mod; 525 526 /* Why bother if there are no other CPUs? */ 527 BUG_ON(num_possible_cpus() == 1); 528 529 mutex_lock(&smp_alt); 530 531 if (uniproc_patched) { 532 pr_info("switching to SMP code\n"); 533 BUG_ON(num_online_cpus() != 1); 534 clear_cpu_cap(&boot_cpu_data, X86_FEATURE_UP); 535 clear_cpu_cap(&cpu_data(0), X86_FEATURE_UP); 536 list_for_each_entry(mod, &smp_alt_modules, next) 537 alternatives_smp_lock(mod->locks, mod->locks_end, 538 mod->text, mod->text_end); 539 uniproc_patched = false; 540 } 541 mutex_unlock(&smp_alt); 542} 543 544/* Return 1 if the address range is reserved for smp-alternatives */ 545int alternatives_text_reserved(void *start, void *end) 546{ 547 struct smp_alt_module *mod; 548 const s32 *poff; 549 u8 *text_start = start; 550 u8 *text_end = end; 551 552 list_for_each_entry(mod, &smp_alt_modules, next) { 553 if (mod->text > text_end || mod->text_end < text_start) 554 continue; 555 for (poff = mod->locks; poff < mod->locks_end; poff++) { 556 const u8 *ptr = (const u8 *)poff + *poff; 557 558 if (text_start <= ptr && text_end > ptr) 559 return 1; 560 } 561 } 562 563 return 0; 564} 565#endif /* CONFIG_SMP */ 566 567#ifdef CONFIG_PARAVIRT 568void __init_or_module apply_paravirt(struct paravirt_patch_site *start, 569 struct paravirt_patch_site *end) 570{ 571 struct paravirt_patch_site *p; 572 char insnbuf[MAX_PATCH_LEN]; 573 574 if (noreplace_paravirt) 575 return; 576 577 for (p = start; p < end; p++) { 578 unsigned int used; 579 580 BUG_ON(p->len > MAX_PATCH_LEN); 581 /* prep the buffer with the original instructions */ 582 memcpy(insnbuf, p->instr, p->len); 583 used = pv_init_ops.patch(p->instrtype, p->clobbers, insnbuf, 584 (unsigned long)p->instr, p->len); 585 586 BUG_ON(used > p->len); 587 588 /* Pad the rest with nops */ 589 add_nops(insnbuf + used, p->len - used); 590 text_poke_early(p->instr, insnbuf, p->len); 591 } 592} 593extern struct paravirt_patch_site __start_parainstructions[], 594 __stop_parainstructions[]; 595#endif /* CONFIG_PARAVIRT */ 596 597void __init alternative_instructions(void) 598{ 599 /* The patching is not fully atomic, so try to avoid local interruptions 600 that might execute the to be patched code. 601 Other CPUs are not running. */ 602 stop_nmi(); 603 604 /* 605 * Don't stop machine check exceptions while patching. 606 * MCEs only happen when something got corrupted and in this 607 * case we must do something about the corruption. 608 * Ignoring it is worse than a unlikely patching race. 609 * Also machine checks tend to be broadcast and if one CPU 610 * goes into machine check the others follow quickly, so we don't 611 * expect a machine check to cause undue problems during to code 612 * patching. 613 */ 614 615 apply_alternatives(__alt_instructions, __alt_instructions_end); 616 617#ifdef CONFIG_SMP 618 /* Patch to UP if other cpus not imminent. */ 619 if (!noreplace_smp && (num_present_cpus() == 1 || setup_max_cpus <= 1)) { 620 uniproc_patched = true; 621 alternatives_smp_module_add(NULL, "core kernel", 622 __smp_locks, __smp_locks_end, 623 _text, _etext); 624 } 625 626 if (!uniproc_patched || num_possible_cpus() == 1) 627 free_init_pages("SMP alternatives", 628 (unsigned long)__smp_locks, 629 (unsigned long)__smp_locks_end); 630#endif 631 632 apply_paravirt(__parainstructions, __parainstructions_end); 633 634 restart_nmi(); 635} 636 637/** 638 * text_poke_early - Update instructions on a live kernel at boot time 639 * @addr: address to modify 640 * @opcode: source of the copy 641 * @len: length to copy 642 * 643 * When you use this code to patch more than one byte of an instruction 644 * you need to make sure that other CPUs cannot execute this code in parallel. 645 * Also no thread must be currently preempted in the middle of these 646 * instructions. And on the local CPU you need to be protected again NMI or MCE 647 * handlers seeing an inconsistent instruction while you patch. 648 */ 649void *__init_or_module text_poke_early(void *addr, const void *opcode, 650 size_t len) 651{ 652 unsigned long flags; 653 local_irq_save(flags); 654 memcpy(addr, opcode, len); 655 sync_core(); 656 local_irq_restore(flags); 657 /* Could also do a CLFLUSH here to speed up CPU recovery; but 658 that causes hangs on some VIA CPUs. */ 659 return addr; 660} 661 662/** 663 * text_poke - Update instructions on a live kernel 664 * @addr: address to modify 665 * @opcode: source of the copy 666 * @len: length to copy 667 * 668 * Only atomic text poke/set should be allowed when not doing early patching. 669 * It means the size must be writable atomically and the address must be aligned 670 * in a way that permits an atomic write. It also makes sure we fit on a single 671 * page. 672 * 673 * Note: Must be called under text_mutex. 674 */ 675void *text_poke(void *addr, const void *opcode, size_t len) 676{ 677 unsigned long flags; 678 char *vaddr; 679 struct page *pages[2]; 680 int i; 681 682 if (!core_kernel_text((unsigned long)addr)) { 683 pages[0] = vmalloc_to_page(addr); 684 pages[1] = vmalloc_to_page(addr + PAGE_SIZE); 685 } else { 686 pages[0] = virt_to_page(addr); 687 WARN_ON(!PageReserved(pages[0])); 688 pages[1] = virt_to_page(addr + PAGE_SIZE); 689 } 690 BUG_ON(!pages[0]); 691 local_irq_save(flags); 692 set_fixmap(FIX_TEXT_POKE0, page_to_phys(pages[0])); 693 if (pages[1]) 694 set_fixmap(FIX_TEXT_POKE1, page_to_phys(pages[1])); 695 vaddr = (char *)fix_to_virt(FIX_TEXT_POKE0); 696 memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len); 697 clear_fixmap(FIX_TEXT_POKE0); 698 if (pages[1]) 699 clear_fixmap(FIX_TEXT_POKE1); 700 local_flush_tlb(); 701 sync_core(); 702 /* Could also do a CLFLUSH here to speed up CPU recovery; but 703 that causes hangs on some VIA CPUs. */ 704 for (i = 0; i < len; i++) 705 BUG_ON(((char *)addr)[i] != ((char *)opcode)[i]); 706 local_irq_restore(flags); 707 return addr; 708} 709 710static void do_sync_core(void *info) 711{ 712 sync_core(); 713} 714 715static bool bp_patching_in_progress; 716static void *bp_int3_handler, *bp_int3_addr; 717 718int poke_int3_handler(struct pt_regs *regs) 719{ 720 /* bp_patching_in_progress */ 721 smp_rmb(); 722 723 if (likely(!bp_patching_in_progress)) 724 return 0; 725 726 if (user_mode(regs) || regs->ip != (unsigned long)bp_int3_addr) 727 return 0; 728 729 /* set up the specified breakpoint handler */ 730 regs->ip = (unsigned long) bp_int3_handler; 731 732 return 1; 733 734} 735 736/** 737 * text_poke_bp() -- update instructions on live kernel on SMP 738 * @addr: address to patch 739 * @opcode: opcode of new instruction 740 * @len: length to copy 741 * @handler: address to jump to when the temporary breakpoint is hit 742 * 743 * Modify multi-byte instruction by using int3 breakpoint on SMP. 744 * We completely avoid stop_machine() here, and achieve the 745 * synchronization using int3 breakpoint. 746 * 747 * The way it is done: 748 * - add a int3 trap to the address that will be patched 749 * - sync cores 750 * - update all but the first byte of the patched range 751 * - sync cores 752 * - replace the first byte (int3) by the first byte of 753 * replacing opcode 754 * - sync cores 755 * 756 * Note: must be called under text_mutex. 757 */ 758void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler) 759{ 760 unsigned char int3 = 0xcc; 761 762 bp_int3_handler = handler; 763 bp_int3_addr = (u8 *)addr + sizeof(int3); 764 bp_patching_in_progress = true; 765 /* 766 * Corresponding read barrier in int3 notifier for 767 * making sure the in_progress flags is correctly ordered wrt. 768 * patching 769 */ 770 smp_wmb(); 771 772 text_poke(addr, &int3, sizeof(int3)); 773 774 on_each_cpu(do_sync_core, NULL, 1); 775 776 if (len - sizeof(int3) > 0) { 777 /* patch all but the first byte */ 778 text_poke((char *)addr + sizeof(int3), 779 (const char *) opcode + sizeof(int3), 780 len - sizeof(int3)); 781 /* 782 * According to Intel, this core syncing is very likely 783 * not necessary and we'd be safe even without it. But 784 * better safe than sorry (plus there's not only Intel). 785 */ 786 on_each_cpu(do_sync_core, NULL, 1); 787 } 788 789 /* patch the first byte */ 790 text_poke(addr, opcode, sizeof(int3)); 791 792 on_each_cpu(do_sync_core, NULL, 1); 793 794 bp_patching_in_progress = false; 795 smp_wmb(); 796 797 return addr; 798} 799 800