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1// SPDX-License-Identifier: GPL-2.0-only
2#define pr_fmt(fmt) "SMP alternatives: " fmt
3
4#include <linux/module.h>
5#include <linux/sched.h>
6#include <linux/mutex.h>
7#include <linux/list.h>
8#include <linux/stringify.h>
9#include <linux/mm.h>
10#include <linux/vmalloc.h>
11#include <linux/memory.h>
12#include <linux/stop_machine.h>
13#include <linux/slab.h>
14#include <linux/kdebug.h>
15#include <linux/kprobes.h>
16#include <linux/mmu_context.h>
17#include <linux/bsearch.h>
18#include <asm/text-patching.h>
19#include <asm/alternative.h>
20#include <asm/sections.h>
21#include <asm/pgtable.h>
22#include <asm/mce.h>
23#include <asm/nmi.h>
24#include <asm/cacheflush.h>
25#include <asm/tlbflush.h>
26#include <asm/io.h>
27#include <asm/fixmap.h>
28
29int __read_mostly alternatives_patched;
30
31EXPORT_SYMBOL_GPL(alternatives_patched);
32
33#define MAX_PATCH_LEN (255-1)
34
35static int __initdata_or_module debug_alternative;
36
37static int __init debug_alt(char *str)
38{
39 debug_alternative = 1;
40 return 1;
41}
42__setup("debug-alternative", debug_alt);
43
44static int noreplace_smp;
45
46static int __init setup_noreplace_smp(char *str)
47{
48 noreplace_smp = 1;
49 return 1;
50}
51__setup("noreplace-smp", setup_noreplace_smp);
52
53#define DPRINTK(fmt, args...) \
54do { \
55 if (debug_alternative) \
56 printk(KERN_DEBUG "%s: " fmt "\n", __func__, ##args); \
57} while (0)
58
59#define DUMP_BYTES(buf, len, fmt, args...) \
60do { \
61 if (unlikely(debug_alternative)) { \
62 int j; \
63 \
64 if (!(len)) \
65 break; \
66 \
67 printk(KERN_DEBUG fmt, ##args); \
68 for (j = 0; j < (len) - 1; j++) \
69 printk(KERN_CONT "%02hhx ", buf[j]); \
70 printk(KERN_CONT "%02hhx\n", buf[j]); \
71 } \
72} while (0)
73
74/*
75 * Each GENERIC_NOPX is of X bytes, and defined as an array of bytes
76 * that correspond to that nop. Getting from one nop to the next, we
77 * add to the array the offset that is equal to the sum of all sizes of
78 * nops preceding the one we are after.
79 *
80 * Note: The GENERIC_NOP5_ATOMIC is at the end, as it breaks the
81 * nice symmetry of sizes of the previous nops.
82 */
83#if defined(GENERIC_NOP1) && !defined(CONFIG_X86_64)
84static const unsigned char intelnops[] =
85{
86 GENERIC_NOP1,
87 GENERIC_NOP2,
88 GENERIC_NOP3,
89 GENERIC_NOP4,
90 GENERIC_NOP5,
91 GENERIC_NOP6,
92 GENERIC_NOP7,
93 GENERIC_NOP8,
94 GENERIC_NOP5_ATOMIC
95};
96static const unsigned char * const intel_nops[ASM_NOP_MAX+2] =
97{
98 NULL,
99 intelnops,
100 intelnops + 1,
101 intelnops + 1 + 2,
102 intelnops + 1 + 2 + 3,
103 intelnops + 1 + 2 + 3 + 4,
104 intelnops + 1 + 2 + 3 + 4 + 5,
105 intelnops + 1 + 2 + 3 + 4 + 5 + 6,
106 intelnops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
107 intelnops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
108};
109#endif
110
111#ifdef K8_NOP1
112static const unsigned char k8nops[] =
113{
114 K8_NOP1,
115 K8_NOP2,
116 K8_NOP3,
117 K8_NOP4,
118 K8_NOP5,
119 K8_NOP6,
120 K8_NOP7,
121 K8_NOP8,
122 K8_NOP5_ATOMIC
123};
124static const unsigned char * const k8_nops[ASM_NOP_MAX+2] =
125{
126 NULL,
127 k8nops,
128 k8nops + 1,
129 k8nops + 1 + 2,
130 k8nops + 1 + 2 + 3,
131 k8nops + 1 + 2 + 3 + 4,
132 k8nops + 1 + 2 + 3 + 4 + 5,
133 k8nops + 1 + 2 + 3 + 4 + 5 + 6,
134 k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
135 k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
136};
137#endif
138
139#if defined(K7_NOP1) && !defined(CONFIG_X86_64)
140static const unsigned char k7nops[] =
141{
142 K7_NOP1,
143 K7_NOP2,
144 K7_NOP3,
145 K7_NOP4,
146 K7_NOP5,
147 K7_NOP6,
148 K7_NOP7,
149 K7_NOP8,
150 K7_NOP5_ATOMIC
151};
152static const unsigned char * const k7_nops[ASM_NOP_MAX+2] =
153{
154 NULL,
155 k7nops,
156 k7nops + 1,
157 k7nops + 1 + 2,
158 k7nops + 1 + 2 + 3,
159 k7nops + 1 + 2 + 3 + 4,
160 k7nops + 1 + 2 + 3 + 4 + 5,
161 k7nops + 1 + 2 + 3 + 4 + 5 + 6,
162 k7nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
163 k7nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
164};
165#endif
166
167#ifdef P6_NOP1
168static const unsigned char p6nops[] =
169{
170 P6_NOP1,
171 P6_NOP2,
172 P6_NOP3,
173 P6_NOP4,
174 P6_NOP5,
175 P6_NOP6,
176 P6_NOP7,
177 P6_NOP8,
178 P6_NOP5_ATOMIC
179};
180static const unsigned char * const p6_nops[ASM_NOP_MAX+2] =
181{
182 NULL,
183 p6nops,
184 p6nops + 1,
185 p6nops + 1 + 2,
186 p6nops + 1 + 2 + 3,
187 p6nops + 1 + 2 + 3 + 4,
188 p6nops + 1 + 2 + 3 + 4 + 5,
189 p6nops + 1 + 2 + 3 + 4 + 5 + 6,
190 p6nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
191 p6nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
192};
193#endif
194
195/* Initialize these to a safe default */
196#ifdef CONFIG_X86_64
197const unsigned char * const *ideal_nops = p6_nops;
198#else
199const unsigned char * const *ideal_nops = intel_nops;
200#endif
201
202void __init arch_init_ideal_nops(void)
203{
204 switch (boot_cpu_data.x86_vendor) {
205 case X86_VENDOR_INTEL:
206 /*
207 * Due to a decoder implementation quirk, some
208 * specific Intel CPUs actually perform better with
209 * the "k8_nops" than with the SDM-recommended NOPs.
210 */
211 if (boot_cpu_data.x86 == 6 &&
212 boot_cpu_data.x86_model >= 0x0f &&
213 boot_cpu_data.x86_model != 0x1c &&
214 boot_cpu_data.x86_model != 0x26 &&
215 boot_cpu_data.x86_model != 0x27 &&
216 boot_cpu_data.x86_model < 0x30) {
217 ideal_nops = k8_nops;
218 } else if (boot_cpu_has(X86_FEATURE_NOPL)) {
219 ideal_nops = p6_nops;
220 } else {
221#ifdef CONFIG_X86_64
222 ideal_nops = k8_nops;
223#else
224 ideal_nops = intel_nops;
225#endif
226 }
227 break;
228
229 case X86_VENDOR_HYGON:
230 ideal_nops = p6_nops;
231 return;
232
233 case X86_VENDOR_AMD:
234 if (boot_cpu_data.x86 > 0xf) {
235 ideal_nops = p6_nops;
236 return;
237 }
238
239 /* fall through */
240
241 default:
242#ifdef CONFIG_X86_64
243 ideal_nops = k8_nops;
244#else
245 if (boot_cpu_has(X86_FEATURE_K8))
246 ideal_nops = k8_nops;
247 else if (boot_cpu_has(X86_FEATURE_K7))
248 ideal_nops = k7_nops;
249 else
250 ideal_nops = intel_nops;
251#endif
252 }
253}
254
255/* Use this to add nops to a buffer, then text_poke the whole buffer. */
256static void __init_or_module add_nops(void *insns, unsigned int len)
257{
258 while (len > 0) {
259 unsigned int noplen = len;
260 if (noplen > ASM_NOP_MAX)
261 noplen = ASM_NOP_MAX;
262 memcpy(insns, ideal_nops[noplen], noplen);
263 insns += noplen;
264 len -= noplen;
265 }
266}
267
268extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
269extern s32 __smp_locks[], __smp_locks_end[];
270void text_poke_early(void *addr, const void *opcode, size_t len);
271
272/*
273 * Are we looking at a near JMP with a 1 or 4-byte displacement.
274 */
275static inline bool is_jmp(const u8 opcode)
276{
277 return opcode == 0xeb || opcode == 0xe9;
278}
279
280static void __init_or_module
281recompute_jump(struct alt_instr *a, u8 *orig_insn, u8 *repl_insn, u8 *insn_buff)
282{
283 u8 *next_rip, *tgt_rip;
284 s32 n_dspl, o_dspl;
285 int repl_len;
286
287 if (a->replacementlen != 5)
288 return;
289
290 o_dspl = *(s32 *)(insn_buff + 1);
291
292 /* next_rip of the replacement JMP */
293 next_rip = repl_insn + a->replacementlen;
294 /* target rip of the replacement JMP */
295 tgt_rip = next_rip + o_dspl;
296 n_dspl = tgt_rip - orig_insn;
297
298 DPRINTK("target RIP: %px, new_displ: 0x%x", tgt_rip, n_dspl);
299
300 if (tgt_rip - orig_insn >= 0) {
301 if (n_dspl - 2 <= 127)
302 goto two_byte_jmp;
303 else
304 goto five_byte_jmp;
305 /* negative offset */
306 } else {
307 if (((n_dspl - 2) & 0xff) == (n_dspl - 2))
308 goto two_byte_jmp;
309 else
310 goto five_byte_jmp;
311 }
312
313two_byte_jmp:
314 n_dspl -= 2;
315
316 insn_buff[0] = 0xeb;
317 insn_buff[1] = (s8)n_dspl;
318 add_nops(insn_buff + 2, 3);
319
320 repl_len = 2;
321 goto done;
322
323five_byte_jmp:
324 n_dspl -= 5;
325
326 insn_buff[0] = 0xe9;
327 *(s32 *)&insn_buff[1] = n_dspl;
328
329 repl_len = 5;
330
331done:
332
333 DPRINTK("final displ: 0x%08x, JMP 0x%lx",
334 n_dspl, (unsigned long)orig_insn + n_dspl + repl_len);
335}
336
337/*
338 * "noinline" to cause control flow change and thus invalidate I$ and
339 * cause refetch after modification.
340 */
341static void __init_or_module noinline optimize_nops(struct alt_instr *a, u8 *instr)
342{
343 unsigned long flags;
344 int i;
345
346 for (i = 0; i < a->padlen; i++) {
347 if (instr[i] != 0x90)
348 return;
349 }
350
351 local_irq_save(flags);
352 add_nops(instr + (a->instrlen - a->padlen), a->padlen);
353 local_irq_restore(flags);
354
355 DUMP_BYTES(instr, a->instrlen, "%px: [%d:%d) optimized NOPs: ",
356 instr, a->instrlen - a->padlen, a->padlen);
357}
358
359/*
360 * Replace instructions with better alternatives for this CPU type. This runs
361 * before SMP is initialized to avoid SMP problems with self modifying code.
362 * This implies that asymmetric systems where APs have less capabilities than
363 * the boot processor are not handled. Tough. Make sure you disable such
364 * features by hand.
365 *
366 * Marked "noinline" to cause control flow change and thus insn cache
367 * to refetch changed I$ lines.
368 */
369void __init_or_module noinline apply_alternatives(struct alt_instr *start,
370 struct alt_instr *end)
371{
372 struct alt_instr *a;
373 u8 *instr, *replacement;
374 u8 insn_buff[MAX_PATCH_LEN];
375
376 DPRINTK("alt table %px, -> %px", start, end);
377 /*
378 * The scan order should be from start to end. A later scanned
379 * alternative code can overwrite previously scanned alternative code.
380 * Some kernel functions (e.g. memcpy, memset, etc) use this order to
381 * patch code.
382 *
383 * So be careful if you want to change the scan order to any other
384 * order.
385 */
386 for (a = start; a < end; a++) {
387 int insn_buff_sz = 0;
388
389 instr = (u8 *)&a->instr_offset + a->instr_offset;
390 replacement = (u8 *)&a->repl_offset + a->repl_offset;
391 BUG_ON(a->instrlen > sizeof(insn_buff));
392 BUG_ON(a->cpuid >= (NCAPINTS + NBUGINTS) * 32);
393 if (!boot_cpu_has(a->cpuid)) {
394 if (a->padlen > 1)
395 optimize_nops(a, instr);
396
397 continue;
398 }
399
400 DPRINTK("feat: %d*32+%d, old: (%pS (%px) len: %d), repl: (%px, len: %d), pad: %d",
401 a->cpuid >> 5,
402 a->cpuid & 0x1f,
403 instr, instr, a->instrlen,
404 replacement, a->replacementlen, a->padlen);
405
406 DUMP_BYTES(instr, a->instrlen, "%px: old_insn: ", instr);
407 DUMP_BYTES(replacement, a->replacementlen, "%px: rpl_insn: ", replacement);
408
409 memcpy(insn_buff, replacement, a->replacementlen);
410 insn_buff_sz = a->replacementlen;
411
412 /*
413 * 0xe8 is a relative jump; fix the offset.
414 *
415 * Instruction length is checked before the opcode to avoid
416 * accessing uninitialized bytes for zero-length replacements.
417 */
418 if (a->replacementlen == 5 && *insn_buff == 0xe8) {
419 *(s32 *)(insn_buff + 1) += replacement - instr;
420 DPRINTK("Fix CALL offset: 0x%x, CALL 0x%lx",
421 *(s32 *)(insn_buff + 1),
422 (unsigned long)instr + *(s32 *)(insn_buff + 1) + 5);
423 }
424
425 if (a->replacementlen && is_jmp(replacement[0]))
426 recompute_jump(a, instr, replacement, insn_buff);
427
428 if (a->instrlen > a->replacementlen) {
429 add_nops(insn_buff + a->replacementlen,
430 a->instrlen - a->replacementlen);
431 insn_buff_sz += a->instrlen - a->replacementlen;
432 }
433 DUMP_BYTES(insn_buff, insn_buff_sz, "%px: final_insn: ", instr);
434
435 text_poke_early(instr, insn_buff, insn_buff_sz);
436 }
437}
438
439#ifdef CONFIG_SMP
440static void alternatives_smp_lock(const s32 *start, const s32 *end,
441 u8 *text, u8 *text_end)
442{
443 const s32 *poff;
444
445 for (poff = start; poff < end; poff++) {
446 u8 *ptr = (u8 *)poff + *poff;
447
448 if (!*poff || ptr < text || ptr >= text_end)
449 continue;
450 /* turn DS segment override prefix into lock prefix */
451 if (*ptr == 0x3e)
452 text_poke(ptr, ((unsigned char []){0xf0}), 1);
453 }
454}
455
456static void alternatives_smp_unlock(const s32 *start, const s32 *end,
457 u8 *text, u8 *text_end)
458{
459 const s32 *poff;
460
461 for (poff = start; poff < end; poff++) {
462 u8 *ptr = (u8 *)poff + *poff;
463
464 if (!*poff || ptr < text || ptr >= text_end)
465 continue;
466 /* turn lock prefix into DS segment override prefix */
467 if (*ptr == 0xf0)
468 text_poke(ptr, ((unsigned char []){0x3E}), 1);
469 }
470}
471
472struct smp_alt_module {
473 /* what is this ??? */
474 struct module *mod;
475 char *name;
476
477 /* ptrs to lock prefixes */
478 const s32 *locks;
479 const s32 *locks_end;
480
481 /* .text segment, needed to avoid patching init code ;) */
482 u8 *text;
483 u8 *text_end;
484
485 struct list_head next;
486};
487static LIST_HEAD(smp_alt_modules);
488static bool uniproc_patched = false; /* protected by text_mutex */
489
490void __init_or_module alternatives_smp_module_add(struct module *mod,
491 char *name,
492 void *locks, void *locks_end,
493 void *text, void *text_end)
494{
495 struct smp_alt_module *smp;
496
497 mutex_lock(&text_mutex);
498 if (!uniproc_patched)
499 goto unlock;
500
501 if (num_possible_cpus() == 1)
502 /* Don't bother remembering, we'll never have to undo it. */
503 goto smp_unlock;
504
505 smp = kzalloc(sizeof(*smp), GFP_KERNEL);
506 if (NULL == smp)
507 /* we'll run the (safe but slow) SMP code then ... */
508 goto unlock;
509
510 smp->mod = mod;
511 smp->name = name;
512 smp->locks = locks;
513 smp->locks_end = locks_end;
514 smp->text = text;
515 smp->text_end = text_end;
516 DPRINTK("locks %p -> %p, text %p -> %p, name %s\n",
517 smp->locks, smp->locks_end,
518 smp->text, smp->text_end, smp->name);
519
520 list_add_tail(&smp->next, &smp_alt_modules);
521smp_unlock:
522 alternatives_smp_unlock(locks, locks_end, text, text_end);
523unlock:
524 mutex_unlock(&text_mutex);
525}
526
527void __init_or_module alternatives_smp_module_del(struct module *mod)
528{
529 struct smp_alt_module *item;
530
531 mutex_lock(&text_mutex);
532 list_for_each_entry(item, &smp_alt_modules, next) {
533 if (mod != item->mod)
534 continue;
535 list_del(&item->next);
536 kfree(item);
537 break;
538 }
539 mutex_unlock(&text_mutex);
540}
541
542void alternatives_enable_smp(void)
543{
544 struct smp_alt_module *mod;
545
546 /* Why bother if there are no other CPUs? */
547 BUG_ON(num_possible_cpus() == 1);
548
549 mutex_lock(&text_mutex);
550
551 if (uniproc_patched) {
552 pr_info("switching to SMP code\n");
553 BUG_ON(num_online_cpus() != 1);
554 clear_cpu_cap(&boot_cpu_data, X86_FEATURE_UP);
555 clear_cpu_cap(&cpu_data(0), X86_FEATURE_UP);
556 list_for_each_entry(mod, &smp_alt_modules, next)
557 alternatives_smp_lock(mod->locks, mod->locks_end,
558 mod->text, mod->text_end);
559 uniproc_patched = false;
560 }
561 mutex_unlock(&text_mutex);
562}
563
564/*
565 * Return 1 if the address range is reserved for SMP-alternatives.
566 * Must hold text_mutex.
567 */
568int alternatives_text_reserved(void *start, void *end)
569{
570 struct smp_alt_module *mod;
571 const s32 *poff;
572 u8 *text_start = start;
573 u8 *text_end = end;
574
575 lockdep_assert_held(&text_mutex);
576
577 list_for_each_entry(mod, &smp_alt_modules, next) {
578 if (mod->text > text_end || mod->text_end < text_start)
579 continue;
580 for (poff = mod->locks; poff < mod->locks_end; poff++) {
581 const u8 *ptr = (const u8 *)poff + *poff;
582
583 if (text_start <= ptr && text_end > ptr)
584 return 1;
585 }
586 }
587
588 return 0;
589}
590#endif /* CONFIG_SMP */
591
592#ifdef CONFIG_PARAVIRT
593void __init_or_module apply_paravirt(struct paravirt_patch_site *start,
594 struct paravirt_patch_site *end)
595{
596 struct paravirt_patch_site *p;
597 char insn_buff[MAX_PATCH_LEN];
598
599 for (p = start; p < end; p++) {
600 unsigned int used;
601
602 BUG_ON(p->len > MAX_PATCH_LEN);
603 /* prep the buffer with the original instructions */
604 memcpy(insn_buff, p->instr, p->len);
605 used = pv_ops.init.patch(p->type, insn_buff, (unsigned long)p->instr, p->len);
606
607 BUG_ON(used > p->len);
608
609 /* Pad the rest with nops */
610 add_nops(insn_buff + used, p->len - used);
611 text_poke_early(p->instr, insn_buff, p->len);
612 }
613}
614extern struct paravirt_patch_site __start_parainstructions[],
615 __stop_parainstructions[];
616#endif /* CONFIG_PARAVIRT */
617
618/*
619 * Self-test for the INT3 based CALL emulation code.
620 *
621 * This exercises int3_emulate_call() to make sure INT3 pt_regs are set up
622 * properly and that there is a stack gap between the INT3 frame and the
623 * previous context. Without this gap doing a virtual PUSH on the interrupted
624 * stack would corrupt the INT3 IRET frame.
625 *
626 * See entry_{32,64}.S for more details.
627 */
628
629/*
630 * We define the int3_magic() function in assembly to control the calling
631 * convention such that we can 'call' it from assembly.
632 */
633
634extern void int3_magic(unsigned int *ptr); /* defined in asm */
635
636asm (
637" .pushsection .init.text, \"ax\", @progbits\n"
638" .type int3_magic, @function\n"
639"int3_magic:\n"
640" movl $1, (%" _ASM_ARG1 ")\n"
641" ret\n"
642" .size int3_magic, .-int3_magic\n"
643" .popsection\n"
644);
645
646extern __initdata unsigned long int3_selftest_ip; /* defined in asm below */
647
648static int __init
649int3_exception_notify(struct notifier_block *self, unsigned long val, void *data)
650{
651 struct die_args *args = data;
652 struct pt_regs *regs = args->regs;
653
654 if (!regs || user_mode(regs))
655 return NOTIFY_DONE;
656
657 if (val != DIE_INT3)
658 return NOTIFY_DONE;
659
660 if (regs->ip - INT3_INSN_SIZE != int3_selftest_ip)
661 return NOTIFY_DONE;
662
663 int3_emulate_call(regs, (unsigned long)&int3_magic);
664 return NOTIFY_STOP;
665}
666
667static void __init int3_selftest(void)
668{
669 static __initdata struct notifier_block int3_exception_nb = {
670 .notifier_call = int3_exception_notify,
671 .priority = INT_MAX-1, /* last */
672 };
673 unsigned int val = 0;
674
675 BUG_ON(register_die_notifier(&int3_exception_nb));
676
677 /*
678 * Basically: int3_magic(&val); but really complicated :-)
679 *
680 * Stick the address of the INT3 instruction into int3_selftest_ip,
681 * then trigger the INT3, padded with NOPs to match a CALL instruction
682 * length.
683 */
684 asm volatile ("1: int3; nop; nop; nop; nop\n\t"
685 ".pushsection .init.data,\"aw\"\n\t"
686 ".align " __ASM_SEL(4, 8) "\n\t"
687 ".type int3_selftest_ip, @object\n\t"
688 ".size int3_selftest_ip, " __ASM_SEL(4, 8) "\n\t"
689 "int3_selftest_ip:\n\t"
690 __ASM_SEL(.long, .quad) " 1b\n\t"
691 ".popsection\n\t"
692 : ASM_CALL_CONSTRAINT
693 : __ASM_SEL_RAW(a, D) (&val)
694 : "memory");
695
696 BUG_ON(val != 1);
697
698 unregister_die_notifier(&int3_exception_nb);
699}
700
701void __init alternative_instructions(void)
702{
703 int3_selftest();
704
705 /*
706 * The patching is not fully atomic, so try to avoid local
707 * interruptions that might execute the to be patched code.
708 * Other CPUs are not running.
709 */
710 stop_nmi();
711
712 /*
713 * Don't stop machine check exceptions while patching.
714 * MCEs only happen when something got corrupted and in this
715 * case we must do something about the corruption.
716 * Ignoring it is worse than an unlikely patching race.
717 * Also machine checks tend to be broadcast and if one CPU
718 * goes into machine check the others follow quickly, so we don't
719 * expect a machine check to cause undue problems during to code
720 * patching.
721 */
722
723 apply_alternatives(__alt_instructions, __alt_instructions_end);
724
725#ifdef CONFIG_SMP
726 /* Patch to UP if other cpus not imminent. */
727 if (!noreplace_smp && (num_present_cpus() == 1 || setup_max_cpus <= 1)) {
728 uniproc_patched = true;
729 alternatives_smp_module_add(NULL, "core kernel",
730 __smp_locks, __smp_locks_end,
731 _text, _etext);
732 }
733
734 if (!uniproc_patched || num_possible_cpus() == 1) {
735 free_init_pages("SMP alternatives",
736 (unsigned long)__smp_locks,
737 (unsigned long)__smp_locks_end);
738 }
739#endif
740
741 apply_paravirt(__parainstructions, __parainstructions_end);
742
743 restart_nmi();
744 alternatives_patched = 1;
745}
746
747/**
748 * text_poke_early - Update instructions on a live kernel at boot time
749 * @addr: address to modify
750 * @opcode: source of the copy
751 * @len: length to copy
752 *
753 * When you use this code to patch more than one byte of an instruction
754 * you need to make sure that other CPUs cannot execute this code in parallel.
755 * Also no thread must be currently preempted in the middle of these
756 * instructions. And on the local CPU you need to be protected against NMI or
757 * MCE handlers seeing an inconsistent instruction while you patch.
758 */
759void __init_or_module text_poke_early(void *addr, const void *opcode,
760 size_t len)
761{
762 unsigned long flags;
763
764 if (boot_cpu_has(X86_FEATURE_NX) &&
765 is_module_text_address((unsigned long)addr)) {
766 /*
767 * Modules text is marked initially as non-executable, so the
768 * code cannot be running and speculative code-fetches are
769 * prevented. Just change the code.
770 */
771 memcpy(addr, opcode, len);
772 } else {
773 local_irq_save(flags);
774 memcpy(addr, opcode, len);
775 local_irq_restore(flags);
776 sync_core();
777
778 /*
779 * Could also do a CLFLUSH here to speed up CPU recovery; but
780 * that causes hangs on some VIA CPUs.
781 */
782 }
783}
784
785__ro_after_init struct mm_struct *poking_mm;
786__ro_after_init unsigned long poking_addr;
787
788static void *__text_poke(void *addr, const void *opcode, size_t len)
789{
790 bool cross_page_boundary = offset_in_page(addr) + len > PAGE_SIZE;
791 struct page *pages[2] = {NULL};
792 temp_mm_state_t prev;
793 unsigned long flags;
794 pte_t pte, *ptep;
795 spinlock_t *ptl;
796 pgprot_t pgprot;
797
798 /*
799 * While boot memory allocator is running we cannot use struct pages as
800 * they are not yet initialized. There is no way to recover.
801 */
802 BUG_ON(!after_bootmem);
803
804 if (!core_kernel_text((unsigned long)addr)) {
805 pages[0] = vmalloc_to_page(addr);
806 if (cross_page_boundary)
807 pages[1] = vmalloc_to_page(addr + PAGE_SIZE);
808 } else {
809 pages[0] = virt_to_page(addr);
810 WARN_ON(!PageReserved(pages[0]));
811 if (cross_page_boundary)
812 pages[1] = virt_to_page(addr + PAGE_SIZE);
813 }
814 /*
815 * If something went wrong, crash and burn since recovery paths are not
816 * implemented.
817 */
818 BUG_ON(!pages[0] || (cross_page_boundary && !pages[1]));
819
820 local_irq_save(flags);
821
822 /*
823 * Map the page without the global bit, as TLB flushing is done with
824 * flush_tlb_mm_range(), which is intended for non-global PTEs.
825 */
826 pgprot = __pgprot(pgprot_val(PAGE_KERNEL) & ~_PAGE_GLOBAL);
827
828 /*
829 * The lock is not really needed, but this allows to avoid open-coding.
830 */
831 ptep = get_locked_pte(poking_mm, poking_addr, &ptl);
832
833 /*
834 * This must not fail; preallocated in poking_init().
835 */
836 VM_BUG_ON(!ptep);
837
838 pte = mk_pte(pages[0], pgprot);
839 set_pte_at(poking_mm, poking_addr, ptep, pte);
840
841 if (cross_page_boundary) {
842 pte = mk_pte(pages[1], pgprot);
843 set_pte_at(poking_mm, poking_addr + PAGE_SIZE, ptep + 1, pte);
844 }
845
846 /*
847 * Loading the temporary mm behaves as a compiler barrier, which
848 * guarantees that the PTE will be set at the time memcpy() is done.
849 */
850 prev = use_temporary_mm(poking_mm);
851
852 kasan_disable_current();
853 memcpy((u8 *)poking_addr + offset_in_page(addr), opcode, len);
854 kasan_enable_current();
855
856 /*
857 * Ensure that the PTE is only cleared after the instructions of memcpy
858 * were issued by using a compiler barrier.
859 */
860 barrier();
861
862 pte_clear(poking_mm, poking_addr, ptep);
863 if (cross_page_boundary)
864 pte_clear(poking_mm, poking_addr + PAGE_SIZE, ptep + 1);
865
866 /*
867 * Loading the previous page-table hierarchy requires a serializing
868 * instruction that already allows the core to see the updated version.
869 * Xen-PV is assumed to serialize execution in a similar manner.
870 */
871 unuse_temporary_mm(prev);
872
873 /*
874 * Flushing the TLB might involve IPIs, which would require enabled
875 * IRQs, but not if the mm is not used, as it is in this point.
876 */
877 flush_tlb_mm_range(poking_mm, poking_addr, poking_addr +
878 (cross_page_boundary ? 2 : 1) * PAGE_SIZE,
879 PAGE_SHIFT, false);
880
881 /*
882 * If the text does not match what we just wrote then something is
883 * fundamentally screwy; there's nothing we can really do about that.
884 */
885 BUG_ON(memcmp(addr, opcode, len));
886
887 pte_unmap_unlock(ptep, ptl);
888 local_irq_restore(flags);
889 return addr;
890}
891
892/**
893 * text_poke - Update instructions on a live kernel
894 * @addr: address to modify
895 * @opcode: source of the copy
896 * @len: length to copy
897 *
898 * Only atomic text poke/set should be allowed when not doing early patching.
899 * It means the size must be writable atomically and the address must be aligned
900 * in a way that permits an atomic write. It also makes sure we fit on a single
901 * page.
902 *
903 * Note that the caller must ensure that if the modified code is part of a
904 * module, the module would not be removed during poking. This can be achieved
905 * by registering a module notifier, and ordering module removal and patching
906 * trough a mutex.
907 */
908void *text_poke(void *addr, const void *opcode, size_t len)
909{
910 lockdep_assert_held(&text_mutex);
911
912 return __text_poke(addr, opcode, len);
913}
914
915/**
916 * text_poke_kgdb - Update instructions on a live kernel by kgdb
917 * @addr: address to modify
918 * @opcode: source of the copy
919 * @len: length to copy
920 *
921 * Only atomic text poke/set should be allowed when not doing early patching.
922 * It means the size must be writable atomically and the address must be aligned
923 * in a way that permits an atomic write. It also makes sure we fit on a single
924 * page.
925 *
926 * Context: should only be used by kgdb, which ensures no other core is running,
927 * despite the fact it does not hold the text_mutex.
928 */
929void *text_poke_kgdb(void *addr, const void *opcode, size_t len)
930{
931 return __text_poke(addr, opcode, len);
932}
933
934static void do_sync_core(void *info)
935{
936 sync_core();
937}
938
939static struct bp_patching_desc {
940 struct text_poke_loc *vec;
941 int nr_entries;
942} bp_patching;
943
944static int patch_cmp(const void *key, const void *elt)
945{
946 struct text_poke_loc *tp = (struct text_poke_loc *) elt;
947
948 if (key < tp->addr)
949 return -1;
950 if (key > tp->addr)
951 return 1;
952 return 0;
953}
954NOKPROBE_SYMBOL(patch_cmp);
955
956int poke_int3_handler(struct pt_regs *regs)
957{
958 struct text_poke_loc *tp;
959 unsigned char int3 = 0xcc;
960 void *ip;
961
962 /*
963 * Having observed our INT3 instruction, we now must observe
964 * bp_patching.nr_entries.
965 *
966 * nr_entries != 0 INT3
967 * WMB RMB
968 * write INT3 if (nr_entries)
969 *
970 * Idem for other elements in bp_patching.
971 */
972 smp_rmb();
973
974 if (likely(!bp_patching.nr_entries))
975 return 0;
976
977 if (user_mode(regs))
978 return 0;
979
980 /*
981 * Discount the sizeof(int3). See text_poke_bp_batch().
982 */
983 ip = (void *) regs->ip - sizeof(int3);
984
985 /*
986 * Skip the binary search if there is a single member in the vector.
987 */
988 if (unlikely(bp_patching.nr_entries > 1)) {
989 tp = bsearch(ip, bp_patching.vec, bp_patching.nr_entries,
990 sizeof(struct text_poke_loc),
991 patch_cmp);
992 if (!tp)
993 return 0;
994 } else {
995 tp = bp_patching.vec;
996 if (tp->addr != ip)
997 return 0;
998 }
999
1000 /* set up the specified breakpoint detour */
1001 regs->ip = (unsigned long) tp->detour;
1002
1003 return 1;
1004}
1005NOKPROBE_SYMBOL(poke_int3_handler);
1006
1007/**
1008 * text_poke_bp_batch() -- update instructions on live kernel on SMP
1009 * @tp: vector of instructions to patch
1010 * @nr_entries: number of entries in the vector
1011 *
1012 * Modify multi-byte instruction by using int3 breakpoint on SMP.
1013 * We completely avoid stop_machine() here, and achieve the
1014 * synchronization using int3 breakpoint.
1015 *
1016 * The way it is done:
1017 * - For each entry in the vector:
1018 * - add a int3 trap to the address that will be patched
1019 * - sync cores
1020 * - For each entry in the vector:
1021 * - update all but the first byte of the patched range
1022 * - sync cores
1023 * - For each entry in the vector:
1024 * - replace the first byte (int3) by the first byte of
1025 * replacing opcode
1026 * - sync cores
1027 */
1028void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries)
1029{
1030 int patched_all_but_first = 0;
1031 unsigned char int3 = 0xcc;
1032 unsigned int i;
1033
1034 lockdep_assert_held(&text_mutex);
1035
1036 bp_patching.vec = tp;
1037 bp_patching.nr_entries = nr_entries;
1038
1039 /*
1040 * Corresponding read barrier in int3 notifier for making sure the
1041 * nr_entries and handler are correctly ordered wrt. patching.
1042 */
1043 smp_wmb();
1044
1045 /*
1046 * First step: add a int3 trap to the address that will be patched.
1047 */
1048 for (i = 0; i < nr_entries; i++)
1049 text_poke(tp[i].addr, &int3, sizeof(int3));
1050
1051 on_each_cpu(do_sync_core, NULL, 1);
1052
1053 /*
1054 * Second step: update all but the first byte of the patched range.
1055 */
1056 for (i = 0; i < nr_entries; i++) {
1057 if (tp[i].len - sizeof(int3) > 0) {
1058 text_poke((char *)tp[i].addr + sizeof(int3),
1059 (const char *)tp[i].opcode + sizeof(int3),
1060 tp[i].len - sizeof(int3));
1061 patched_all_but_first++;
1062 }
1063 }
1064
1065 if (patched_all_but_first) {
1066 /*
1067 * According to Intel, this core syncing is very likely
1068 * not necessary and we'd be safe even without it. But
1069 * better safe than sorry (plus there's not only Intel).
1070 */
1071 on_each_cpu(do_sync_core, NULL, 1);
1072 }
1073
1074 /*
1075 * Third step: replace the first byte (int3) by the first byte of
1076 * replacing opcode.
1077 */
1078 for (i = 0; i < nr_entries; i++)
1079 text_poke(tp[i].addr, tp[i].opcode, sizeof(int3));
1080
1081 on_each_cpu(do_sync_core, NULL, 1);
1082 /*
1083 * sync_core() implies an smp_mb() and orders this store against
1084 * the writing of the new instruction.
1085 */
1086 bp_patching.vec = NULL;
1087 bp_patching.nr_entries = 0;
1088}
1089
1090/**
1091 * text_poke_bp() -- update instructions on live kernel on SMP
1092 * @addr: address to patch
1093 * @opcode: opcode of new instruction
1094 * @len: length to copy
1095 * @handler: address to jump to when the temporary breakpoint is hit
1096 *
1097 * Update a single instruction with the vector in the stack, avoiding
1098 * dynamically allocated memory. This function should be used when it is
1099 * not possible to allocate memory.
1100 */
1101void text_poke_bp(void *addr, const void *opcode, size_t len, void *handler)
1102{
1103 struct text_poke_loc tp = {
1104 .detour = handler,
1105 .addr = addr,
1106 .len = len,
1107 };
1108
1109 if (len > POKE_MAX_OPCODE_SIZE) {
1110 WARN_ONCE(1, "len is larger than %d\n", POKE_MAX_OPCODE_SIZE);
1111 return;
1112 }
1113
1114 memcpy((void *)tp.opcode, opcode, len);
1115
1116 text_poke_bp_batch(&tp, 1);
1117}
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
24int __read_mostly alternatives_patched;
25
26EXPORT_SYMBOL_GPL(alternatives_patched);
27
28#define MAX_PATCH_LEN (255-1)
29
30static int __initdata_or_module debug_alternative;
31
32static int __init debug_alt(char *str)
33{
34 debug_alternative = 1;
35 return 1;
36}
37__setup("debug-alternative", debug_alt);
38
39static int noreplace_smp;
40
41static int __init setup_noreplace_smp(char *str)
42{
43 noreplace_smp = 1;
44 return 1;
45}
46__setup("noreplace-smp", setup_noreplace_smp);
47
48#ifdef CONFIG_PARAVIRT
49static int __initdata_or_module noreplace_paravirt = 0;
50
51static int __init setup_noreplace_paravirt(char *str)
52{
53 noreplace_paravirt = 1;
54 return 1;
55}
56__setup("noreplace-paravirt", setup_noreplace_paravirt);
57#endif
58
59#define DPRINTK(fmt, args...) \
60do { \
61 if (debug_alternative) \
62 printk(KERN_DEBUG "%s: " fmt "\n", __func__, ##args); \
63} while (0)
64
65#define DUMP_BYTES(buf, len, fmt, args...) \
66do { \
67 if (unlikely(debug_alternative)) { \
68 int j; \
69 \
70 if (!(len)) \
71 break; \
72 \
73 printk(KERN_DEBUG fmt, ##args); \
74 for (j = 0; j < (len) - 1; j++) \
75 printk(KERN_CONT "%02hhx ", buf[j]); \
76 printk(KERN_CONT "%02hhx\n", buf[j]); \
77 } \
78} while (0)
79
80/*
81 * Each GENERIC_NOPX is of X bytes, and defined as an array of bytes
82 * that correspond to that nop. Getting from one nop to the next, we
83 * add to the array the offset that is equal to the sum of all sizes of
84 * nops preceding the one we are after.
85 *
86 * Note: The GENERIC_NOP5_ATOMIC is at the end, as it breaks the
87 * nice symmetry of sizes of the previous nops.
88 */
89#if defined(GENERIC_NOP1) && !defined(CONFIG_X86_64)
90static const unsigned char intelnops[] =
91{
92 GENERIC_NOP1,
93 GENERIC_NOP2,
94 GENERIC_NOP3,
95 GENERIC_NOP4,
96 GENERIC_NOP5,
97 GENERIC_NOP6,
98 GENERIC_NOP7,
99 GENERIC_NOP8,
100 GENERIC_NOP5_ATOMIC
101};
102static const unsigned char * const intel_nops[ASM_NOP_MAX+2] =
103{
104 NULL,
105 intelnops,
106 intelnops + 1,
107 intelnops + 1 + 2,
108 intelnops + 1 + 2 + 3,
109 intelnops + 1 + 2 + 3 + 4,
110 intelnops + 1 + 2 + 3 + 4 + 5,
111 intelnops + 1 + 2 + 3 + 4 + 5 + 6,
112 intelnops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
113 intelnops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
114};
115#endif
116
117#ifdef K8_NOP1
118static const unsigned char k8nops[] =
119{
120 K8_NOP1,
121 K8_NOP2,
122 K8_NOP3,
123 K8_NOP4,
124 K8_NOP5,
125 K8_NOP6,
126 K8_NOP7,
127 K8_NOP8,
128 K8_NOP5_ATOMIC
129};
130static const unsigned char * const k8_nops[ASM_NOP_MAX+2] =
131{
132 NULL,
133 k8nops,
134 k8nops + 1,
135 k8nops + 1 + 2,
136 k8nops + 1 + 2 + 3,
137 k8nops + 1 + 2 + 3 + 4,
138 k8nops + 1 + 2 + 3 + 4 + 5,
139 k8nops + 1 + 2 + 3 + 4 + 5 + 6,
140 k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
141 k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
142};
143#endif
144
145#if defined(K7_NOP1) && !defined(CONFIG_X86_64)
146static const unsigned char k7nops[] =
147{
148 K7_NOP1,
149 K7_NOP2,
150 K7_NOP3,
151 K7_NOP4,
152 K7_NOP5,
153 K7_NOP6,
154 K7_NOP7,
155 K7_NOP8,
156 K7_NOP5_ATOMIC
157};
158static const unsigned char * const k7_nops[ASM_NOP_MAX+2] =
159{
160 NULL,
161 k7nops,
162 k7nops + 1,
163 k7nops + 1 + 2,
164 k7nops + 1 + 2 + 3,
165 k7nops + 1 + 2 + 3 + 4,
166 k7nops + 1 + 2 + 3 + 4 + 5,
167 k7nops + 1 + 2 + 3 + 4 + 5 + 6,
168 k7nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
169 k7nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
170};
171#endif
172
173#ifdef P6_NOP1
174static const unsigned char p6nops[] =
175{
176 P6_NOP1,
177 P6_NOP2,
178 P6_NOP3,
179 P6_NOP4,
180 P6_NOP5,
181 P6_NOP6,
182 P6_NOP7,
183 P6_NOP8,
184 P6_NOP5_ATOMIC
185};
186static const unsigned char * const p6_nops[ASM_NOP_MAX+2] =
187{
188 NULL,
189 p6nops,
190 p6nops + 1,
191 p6nops + 1 + 2,
192 p6nops + 1 + 2 + 3,
193 p6nops + 1 + 2 + 3 + 4,
194 p6nops + 1 + 2 + 3 + 4 + 5,
195 p6nops + 1 + 2 + 3 + 4 + 5 + 6,
196 p6nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
197 p6nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
198};
199#endif
200
201/* Initialize these to a safe default */
202#ifdef CONFIG_X86_64
203const unsigned char * const *ideal_nops = p6_nops;
204#else
205const unsigned char * const *ideal_nops = intel_nops;
206#endif
207
208void __init arch_init_ideal_nops(void)
209{
210 switch (boot_cpu_data.x86_vendor) {
211 case X86_VENDOR_INTEL:
212 /*
213 * Due to a decoder implementation quirk, some
214 * specific Intel CPUs actually perform better with
215 * the "k8_nops" than with the SDM-recommended NOPs.
216 */
217 if (boot_cpu_data.x86 == 6 &&
218 boot_cpu_data.x86_model >= 0x0f &&
219 boot_cpu_data.x86_model != 0x1c &&
220 boot_cpu_data.x86_model != 0x26 &&
221 boot_cpu_data.x86_model != 0x27 &&
222 boot_cpu_data.x86_model < 0x30) {
223 ideal_nops = k8_nops;
224 } else if (boot_cpu_has(X86_FEATURE_NOPL)) {
225 ideal_nops = p6_nops;
226 } else {
227#ifdef CONFIG_X86_64
228 ideal_nops = k8_nops;
229#else
230 ideal_nops = intel_nops;
231#endif
232 }
233 break;
234
235 case X86_VENDOR_AMD:
236 if (boot_cpu_data.x86 > 0xf) {
237 ideal_nops = p6_nops;
238 return;
239 }
240
241 /* fall through */
242
243 default:
244#ifdef CONFIG_X86_64
245 ideal_nops = k8_nops;
246#else
247 if (boot_cpu_has(X86_FEATURE_K8))
248 ideal_nops = k8_nops;
249 else if (boot_cpu_has(X86_FEATURE_K7))
250 ideal_nops = k7_nops;
251 else
252 ideal_nops = intel_nops;
253#endif
254 }
255}
256
257/* Use this to add nops to a buffer, then text_poke the whole buffer. */
258static void __init_or_module add_nops(void *insns, unsigned int len)
259{
260 while (len > 0) {
261 unsigned int noplen = len;
262 if (noplen > ASM_NOP_MAX)
263 noplen = ASM_NOP_MAX;
264 memcpy(insns, ideal_nops[noplen], noplen);
265 insns += noplen;
266 len -= noplen;
267 }
268}
269
270extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
271extern s32 __smp_locks[], __smp_locks_end[];
272void *text_poke_early(void *addr, const void *opcode, size_t len);
273
274/*
275 * Are we looking at a near JMP with a 1 or 4-byte displacement.
276 */
277static inline bool is_jmp(const u8 opcode)
278{
279 return opcode == 0xeb || opcode == 0xe9;
280}
281
282static void __init_or_module
283recompute_jump(struct alt_instr *a, u8 *orig_insn, u8 *repl_insn, u8 *insnbuf)
284{
285 u8 *next_rip, *tgt_rip;
286 s32 n_dspl, o_dspl;
287 int repl_len;
288
289 if (a->replacementlen != 5)
290 return;
291
292 o_dspl = *(s32 *)(insnbuf + 1);
293
294 /* next_rip of the replacement JMP */
295 next_rip = repl_insn + a->replacementlen;
296 /* target rip of the replacement JMP */
297 tgt_rip = next_rip + o_dspl;
298 n_dspl = tgt_rip - orig_insn;
299
300 DPRINTK("target RIP: %p, new_displ: 0x%x", tgt_rip, n_dspl);
301
302 if (tgt_rip - orig_insn >= 0) {
303 if (n_dspl - 2 <= 127)
304 goto two_byte_jmp;
305 else
306 goto five_byte_jmp;
307 /* negative offset */
308 } else {
309 if (((n_dspl - 2) & 0xff) == (n_dspl - 2))
310 goto two_byte_jmp;
311 else
312 goto five_byte_jmp;
313 }
314
315two_byte_jmp:
316 n_dspl -= 2;
317
318 insnbuf[0] = 0xeb;
319 insnbuf[1] = (s8)n_dspl;
320 add_nops(insnbuf + 2, 3);
321
322 repl_len = 2;
323 goto done;
324
325five_byte_jmp:
326 n_dspl -= 5;
327
328 insnbuf[0] = 0xe9;
329 *(s32 *)&insnbuf[1] = n_dspl;
330
331 repl_len = 5;
332
333done:
334
335 DPRINTK("final displ: 0x%08x, JMP 0x%lx",
336 n_dspl, (unsigned long)orig_insn + n_dspl + repl_len);
337}
338
339static void __init_or_module optimize_nops(struct alt_instr *a, u8 *instr)
340{
341 unsigned long flags;
342
343 if (instr[0] != 0x90)
344 return;
345
346 local_irq_save(flags);
347 add_nops(instr + (a->instrlen - a->padlen), a->padlen);
348 sync_core();
349 local_irq_restore(flags);
350
351 DUMP_BYTES(instr, a->instrlen, "%p: [%d:%d) optimized NOPs: ",
352 instr, a->instrlen - a->padlen, a->padlen);
353}
354
355/*
356 * Replace instructions with better alternatives for this CPU type. This runs
357 * before SMP is initialized to avoid SMP problems with self modifying code.
358 * This implies that asymmetric systems where APs have less capabilities than
359 * the boot processor are not handled. Tough. Make sure you disable such
360 * features by hand.
361 */
362void __init_or_module apply_alternatives(struct alt_instr *start,
363 struct alt_instr *end)
364{
365 struct alt_instr *a;
366 u8 *instr, *replacement;
367 u8 insnbuf[MAX_PATCH_LEN];
368
369 DPRINTK("alt table %p -> %p", start, end);
370 /*
371 * The scan order should be from start to end. A later scanned
372 * alternative code can overwrite previously scanned alternative code.
373 * Some kernel functions (e.g. memcpy, memset, etc) use this order to
374 * patch code.
375 *
376 * So be careful if you want to change the scan order to any other
377 * order.
378 */
379 for (a = start; a < end; a++) {
380 int insnbuf_sz = 0;
381
382 instr = (u8 *)&a->instr_offset + a->instr_offset;
383 replacement = (u8 *)&a->repl_offset + a->repl_offset;
384 BUG_ON(a->instrlen > sizeof(insnbuf));
385 BUG_ON(a->cpuid >= (NCAPINTS + NBUGINTS) * 32);
386 if (!boot_cpu_has(a->cpuid)) {
387 if (a->padlen > 1)
388 optimize_nops(a, instr);
389
390 continue;
391 }
392
393 DPRINTK("feat: %d*32+%d, old: (%p, len: %d), repl: (%p, len: %d), pad: %d",
394 a->cpuid >> 5,
395 a->cpuid & 0x1f,
396 instr, a->instrlen,
397 replacement, a->replacementlen, a->padlen);
398
399 DUMP_BYTES(instr, a->instrlen, "%p: old_insn: ", instr);
400 DUMP_BYTES(replacement, a->replacementlen, "%p: rpl_insn: ", replacement);
401
402 memcpy(insnbuf, replacement, a->replacementlen);
403 insnbuf_sz = a->replacementlen;
404
405 /* 0xe8 is a relative jump; fix the offset. */
406 if (*insnbuf == 0xe8 && a->replacementlen == 5) {
407 *(s32 *)(insnbuf + 1) += replacement - instr;
408 DPRINTK("Fix CALL offset: 0x%x, CALL 0x%lx",
409 *(s32 *)(insnbuf + 1),
410 (unsigned long)instr + *(s32 *)(insnbuf + 1) + 5);
411 }
412
413 if (a->replacementlen && is_jmp(replacement[0]))
414 recompute_jump(a, instr, replacement, insnbuf);
415
416 if (a->instrlen > a->replacementlen) {
417 add_nops(insnbuf + a->replacementlen,
418 a->instrlen - a->replacementlen);
419 insnbuf_sz += a->instrlen - a->replacementlen;
420 }
421 DUMP_BYTES(insnbuf, insnbuf_sz, "%p: final_insn: ", instr);
422
423 text_poke_early(instr, insnbuf, insnbuf_sz);
424 }
425}
426
427#ifdef CONFIG_SMP
428static void alternatives_smp_lock(const s32 *start, const s32 *end,
429 u8 *text, u8 *text_end)
430{
431 const s32 *poff;
432
433 mutex_lock(&text_mutex);
434 for (poff = start; poff < end; poff++) {
435 u8 *ptr = (u8 *)poff + *poff;
436
437 if (!*poff || ptr < text || ptr >= text_end)
438 continue;
439 /* turn DS segment override prefix into lock prefix */
440 if (*ptr == 0x3e)
441 text_poke(ptr, ((unsigned char []){0xf0}), 1);
442 }
443 mutex_unlock(&text_mutex);
444}
445
446static void alternatives_smp_unlock(const s32 *start, const s32 *end,
447 u8 *text, u8 *text_end)
448{
449 const s32 *poff;
450
451 mutex_lock(&text_mutex);
452 for (poff = start; poff < end; poff++) {
453 u8 *ptr = (u8 *)poff + *poff;
454
455 if (!*poff || ptr < text || ptr >= text_end)
456 continue;
457 /* turn lock prefix into DS segment override prefix */
458 if (*ptr == 0xf0)
459 text_poke(ptr, ((unsigned char []){0x3E}), 1);
460 }
461 mutex_unlock(&text_mutex);
462}
463
464struct smp_alt_module {
465 /* what is this ??? */
466 struct module *mod;
467 char *name;
468
469 /* ptrs to lock prefixes */
470 const s32 *locks;
471 const s32 *locks_end;
472
473 /* .text segment, needed to avoid patching init code ;) */
474 u8 *text;
475 u8 *text_end;
476
477 struct list_head next;
478};
479static LIST_HEAD(smp_alt_modules);
480static DEFINE_MUTEX(smp_alt);
481static bool uniproc_patched = false; /* protected by smp_alt */
482
483void __init_or_module alternatives_smp_module_add(struct module *mod,
484 char *name,
485 void *locks, void *locks_end,
486 void *text, void *text_end)
487{
488 struct smp_alt_module *smp;
489
490 mutex_lock(&smp_alt);
491 if (!uniproc_patched)
492 goto unlock;
493
494 if (num_possible_cpus() == 1)
495 /* Don't bother remembering, we'll never have to undo it. */
496 goto smp_unlock;
497
498 smp = kzalloc(sizeof(*smp), GFP_KERNEL);
499 if (NULL == smp)
500 /* we'll run the (safe but slow) SMP code then ... */
501 goto unlock;
502
503 smp->mod = mod;
504 smp->name = name;
505 smp->locks = locks;
506 smp->locks_end = locks_end;
507 smp->text = text;
508 smp->text_end = text_end;
509 DPRINTK("locks %p -> %p, text %p -> %p, name %s\n",
510 smp->locks, smp->locks_end,
511 smp->text, smp->text_end, smp->name);
512
513 list_add_tail(&smp->next, &smp_alt_modules);
514smp_unlock:
515 alternatives_smp_unlock(locks, locks_end, text, text_end);
516unlock:
517 mutex_unlock(&smp_alt);
518}
519
520void __init_or_module alternatives_smp_module_del(struct module *mod)
521{
522 struct smp_alt_module *item;
523
524 mutex_lock(&smp_alt);
525 list_for_each_entry(item, &smp_alt_modules, next) {
526 if (mod != item->mod)
527 continue;
528 list_del(&item->next);
529 kfree(item);
530 break;
531 }
532 mutex_unlock(&smp_alt);
533}
534
535void alternatives_enable_smp(void)
536{
537 struct smp_alt_module *mod;
538
539 /* Why bother if there are no other CPUs? */
540 BUG_ON(num_possible_cpus() == 1);
541
542 mutex_lock(&smp_alt);
543
544 if (uniproc_patched) {
545 pr_info("switching to SMP code\n");
546 BUG_ON(num_online_cpus() != 1);
547 clear_cpu_cap(&boot_cpu_data, X86_FEATURE_UP);
548 clear_cpu_cap(&cpu_data(0), X86_FEATURE_UP);
549 list_for_each_entry(mod, &smp_alt_modules, next)
550 alternatives_smp_lock(mod->locks, mod->locks_end,
551 mod->text, mod->text_end);
552 uniproc_patched = false;
553 }
554 mutex_unlock(&smp_alt);
555}
556
557/* Return 1 if the address range is reserved for smp-alternatives */
558int alternatives_text_reserved(void *start, void *end)
559{
560 struct smp_alt_module *mod;
561 const s32 *poff;
562 u8 *text_start = start;
563 u8 *text_end = end;
564
565 list_for_each_entry(mod, &smp_alt_modules, next) {
566 if (mod->text > text_end || mod->text_end < text_start)
567 continue;
568 for (poff = mod->locks; poff < mod->locks_end; poff++) {
569 const u8 *ptr = (const u8 *)poff + *poff;
570
571 if (text_start <= ptr && text_end > ptr)
572 return 1;
573 }
574 }
575
576 return 0;
577}
578#endif /* CONFIG_SMP */
579
580#ifdef CONFIG_PARAVIRT
581void __init_or_module apply_paravirt(struct paravirt_patch_site *start,
582 struct paravirt_patch_site *end)
583{
584 struct paravirt_patch_site *p;
585 char insnbuf[MAX_PATCH_LEN];
586
587 if (noreplace_paravirt)
588 return;
589
590 for (p = start; p < end; p++) {
591 unsigned int used;
592
593 BUG_ON(p->len > MAX_PATCH_LEN);
594 /* prep the buffer with the original instructions */
595 memcpy(insnbuf, p->instr, p->len);
596 used = pv_init_ops.patch(p->instrtype, p->clobbers, insnbuf,
597 (unsigned long)p->instr, p->len);
598
599 BUG_ON(used > p->len);
600
601 /* Pad the rest with nops */
602 add_nops(insnbuf + used, p->len - used);
603 text_poke_early(p->instr, insnbuf, p->len);
604 }
605}
606extern struct paravirt_patch_site __start_parainstructions[],
607 __stop_parainstructions[];
608#endif /* CONFIG_PARAVIRT */
609
610void __init alternative_instructions(void)
611{
612 /* The patching is not fully atomic, so try to avoid local interruptions
613 that might execute the to be patched code.
614 Other CPUs are not running. */
615 stop_nmi();
616
617 /*
618 * Don't stop machine check exceptions while patching.
619 * MCEs only happen when something got corrupted and in this
620 * case we must do something about the corruption.
621 * Ignoring it is worse than a unlikely patching race.
622 * Also machine checks tend to be broadcast and if one CPU
623 * goes into machine check the others follow quickly, so we don't
624 * expect a machine check to cause undue problems during to code
625 * patching.
626 */
627
628 apply_alternatives(__alt_instructions, __alt_instructions_end);
629
630#ifdef CONFIG_SMP
631 /* Patch to UP if other cpus not imminent. */
632 if (!noreplace_smp && (num_present_cpus() == 1 || setup_max_cpus <= 1)) {
633 uniproc_patched = true;
634 alternatives_smp_module_add(NULL, "core kernel",
635 __smp_locks, __smp_locks_end,
636 _text, _etext);
637 }
638
639 if (!uniproc_patched || num_possible_cpus() == 1)
640 free_init_pages("SMP alternatives",
641 (unsigned long)__smp_locks,
642 (unsigned long)__smp_locks_end);
643#endif
644
645 apply_paravirt(__parainstructions, __parainstructions_end);
646
647 restart_nmi();
648 alternatives_patched = 1;
649}
650
651/**
652 * text_poke_early - Update instructions on a live kernel at boot time
653 * @addr: address to modify
654 * @opcode: source of the copy
655 * @len: length to copy
656 *
657 * When you use this code to patch more than one byte of an instruction
658 * you need to make sure that other CPUs cannot execute this code in parallel.
659 * Also no thread must be currently preempted in the middle of these
660 * instructions. And on the local CPU you need to be protected again NMI or MCE
661 * handlers seeing an inconsistent instruction while you patch.
662 */
663void *__init_or_module text_poke_early(void *addr, const void *opcode,
664 size_t len)
665{
666 unsigned long flags;
667 local_irq_save(flags);
668 memcpy(addr, opcode, len);
669 sync_core();
670 local_irq_restore(flags);
671 /* Could also do a CLFLUSH here to speed up CPU recovery; but
672 that causes hangs on some VIA CPUs. */
673 return addr;
674}
675
676/**
677 * text_poke - Update instructions on a live kernel
678 * @addr: address to modify
679 * @opcode: source of the copy
680 * @len: length to copy
681 *
682 * Only atomic text poke/set should be allowed when not doing early patching.
683 * It means the size must be writable atomically and the address must be aligned
684 * in a way that permits an atomic write. It also makes sure we fit on a single
685 * page.
686 *
687 * Note: Must be called under text_mutex.
688 */
689void *text_poke(void *addr, const void *opcode, size_t len)
690{
691 unsigned long flags;
692 char *vaddr;
693 struct page *pages[2];
694 int i;
695
696 if (!core_kernel_text((unsigned long)addr)) {
697 pages[0] = vmalloc_to_page(addr);
698 pages[1] = vmalloc_to_page(addr + PAGE_SIZE);
699 } else {
700 pages[0] = virt_to_page(addr);
701 WARN_ON(!PageReserved(pages[0]));
702 pages[1] = virt_to_page(addr + PAGE_SIZE);
703 }
704 BUG_ON(!pages[0]);
705 local_irq_save(flags);
706 set_fixmap(FIX_TEXT_POKE0, page_to_phys(pages[0]));
707 if (pages[1])
708 set_fixmap(FIX_TEXT_POKE1, page_to_phys(pages[1]));
709 vaddr = (char *)fix_to_virt(FIX_TEXT_POKE0);
710 memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len);
711 clear_fixmap(FIX_TEXT_POKE0);
712 if (pages[1])
713 clear_fixmap(FIX_TEXT_POKE1);
714 local_flush_tlb();
715 sync_core();
716 /* Could also do a CLFLUSH here to speed up CPU recovery; but
717 that causes hangs on some VIA CPUs. */
718 for (i = 0; i < len; i++)
719 BUG_ON(((char *)addr)[i] != ((char *)opcode)[i]);
720 local_irq_restore(flags);
721 return addr;
722}
723
724static void do_sync_core(void *info)
725{
726 sync_core();
727}
728
729static bool bp_patching_in_progress;
730static void *bp_int3_handler, *bp_int3_addr;
731
732int poke_int3_handler(struct pt_regs *regs)
733{
734 /* bp_patching_in_progress */
735 smp_rmb();
736
737 if (likely(!bp_patching_in_progress))
738 return 0;
739
740 if (user_mode(regs) || regs->ip != (unsigned long)bp_int3_addr)
741 return 0;
742
743 /* set up the specified breakpoint handler */
744 regs->ip = (unsigned long) bp_int3_handler;
745
746 return 1;
747
748}
749
750/**
751 * text_poke_bp() -- update instructions on live kernel on SMP
752 * @addr: address to patch
753 * @opcode: opcode of new instruction
754 * @len: length to copy
755 * @handler: address to jump to when the temporary breakpoint is hit
756 *
757 * Modify multi-byte instruction by using int3 breakpoint on SMP.
758 * We completely avoid stop_machine() here, and achieve the
759 * synchronization using int3 breakpoint.
760 *
761 * The way it is done:
762 * - add a int3 trap to the address that will be patched
763 * - sync cores
764 * - update all but the first byte of the patched range
765 * - sync cores
766 * - replace the first byte (int3) by the first byte of
767 * replacing opcode
768 * - sync cores
769 *
770 * Note: must be called under text_mutex.
771 */
772void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler)
773{
774 unsigned char int3 = 0xcc;
775
776 bp_int3_handler = handler;
777 bp_int3_addr = (u8 *)addr + sizeof(int3);
778 bp_patching_in_progress = true;
779 /*
780 * Corresponding read barrier in int3 notifier for
781 * making sure the in_progress flags is correctly ordered wrt.
782 * patching
783 */
784 smp_wmb();
785
786 text_poke(addr, &int3, sizeof(int3));
787
788 on_each_cpu(do_sync_core, NULL, 1);
789
790 if (len - sizeof(int3) > 0) {
791 /* patch all but the first byte */
792 text_poke((char *)addr + sizeof(int3),
793 (const char *) opcode + sizeof(int3),
794 len - sizeof(int3));
795 /*
796 * According to Intel, this core syncing is very likely
797 * not necessary and we'd be safe even without it. But
798 * better safe than sorry (plus there's not only Intel).
799 */
800 on_each_cpu(do_sync_core, NULL, 1);
801 }
802
803 /* patch the first byte */
804 text_poke(addr, opcode, sizeof(int3));
805
806 on_each_cpu(do_sync_core, NULL, 1);
807
808 bp_patching_in_progress = false;
809 smp_wmb();
810
811 return addr;
812}
813