Loading...
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// 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/perf_event.h>
7#include <linux/mutex.h>
8#include <linux/list.h>
9#include <linux/stringify.h>
10#include <linux/highmem.h>
11#include <linux/mm.h>
12#include <linux/vmalloc.h>
13#include <linux/memory.h>
14#include <linux/stop_machine.h>
15#include <linux/slab.h>
16#include <linux/kdebug.h>
17#include <linux/kprobes.h>
18#include <linux/mmu_context.h>
19#include <linux/bsearch.h>
20#include <linux/sync_core.h>
21#include <asm/text-patching.h>
22#include <asm/alternative.h>
23#include <asm/sections.h>
24#include <asm/mce.h>
25#include <asm/nmi.h>
26#include <asm/cacheflush.h>
27#include <asm/tlbflush.h>
28#include <asm/insn.h>
29#include <asm/io.h>
30#include <asm/fixmap.h>
31
32int __read_mostly alternatives_patched;
33
34EXPORT_SYMBOL_GPL(alternatives_patched);
35
36#define MAX_PATCH_LEN (255-1)
37
38static int __initdata_or_module debug_alternative;
39
40static int __init debug_alt(char *str)
41{
42 debug_alternative = 1;
43 return 1;
44}
45__setup("debug-alternative", debug_alt);
46
47static int noreplace_smp;
48
49static 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#define DPRINTK(fmt, args...) \
57do { \
58 if (debug_alternative) \
59 printk(KERN_DEBUG pr_fmt(fmt) "\n", ##args); \
60} while (0)
61
62#define DUMP_BYTES(buf, len, fmt, args...) \
63do { \
64 if (unlikely(debug_alternative)) { \
65 int j; \
66 \
67 if (!(len)) \
68 break; \
69 \
70 printk(KERN_DEBUG pr_fmt(fmt), ##args); \
71 for (j = 0; j < (len) - 1; j++) \
72 printk(KERN_CONT "%02hhx ", buf[j]); \
73 printk(KERN_CONT "%02hhx\n", buf[j]); \
74 } \
75} while (0)
76
77/*
78 * Each GENERIC_NOPX is of X bytes, and defined as an array of bytes
79 * that correspond to that nop. Getting from one nop to the next, we
80 * add to the array the offset that is equal to the sum of all sizes of
81 * nops preceding the one we are after.
82 *
83 * Note: The GENERIC_NOP5_ATOMIC is at the end, as it breaks the
84 * nice symmetry of sizes of the previous nops.
85 */
86#if defined(GENERIC_NOP1) && !defined(CONFIG_X86_64)
87static const unsigned char intelnops[] =
88{
89 GENERIC_NOP1,
90 GENERIC_NOP2,
91 GENERIC_NOP3,
92 GENERIC_NOP4,
93 GENERIC_NOP5,
94 GENERIC_NOP6,
95 GENERIC_NOP7,
96 GENERIC_NOP8,
97 GENERIC_NOP5_ATOMIC
98};
99static const unsigned char * const intel_nops[ASM_NOP_MAX+2] =
100{
101 NULL,
102 intelnops,
103 intelnops + 1,
104 intelnops + 1 + 2,
105 intelnops + 1 + 2 + 3,
106 intelnops + 1 + 2 + 3 + 4,
107 intelnops + 1 + 2 + 3 + 4 + 5,
108 intelnops + 1 + 2 + 3 + 4 + 5 + 6,
109 intelnops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
110 intelnops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
111};
112#endif
113
114#ifdef K8_NOP1
115static const unsigned char k8nops[] =
116{
117 K8_NOP1,
118 K8_NOP2,
119 K8_NOP3,
120 K8_NOP4,
121 K8_NOP5,
122 K8_NOP6,
123 K8_NOP7,
124 K8_NOP8,
125 K8_NOP5_ATOMIC
126};
127static const unsigned char * const k8_nops[ASM_NOP_MAX+2] =
128{
129 NULL,
130 k8nops,
131 k8nops + 1,
132 k8nops + 1 + 2,
133 k8nops + 1 + 2 + 3,
134 k8nops + 1 + 2 + 3 + 4,
135 k8nops + 1 + 2 + 3 + 4 + 5,
136 k8nops + 1 + 2 + 3 + 4 + 5 + 6,
137 k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
138 k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
139};
140#endif
141
142#if defined(K7_NOP1) && !defined(CONFIG_X86_64)
143static const unsigned char k7nops[] =
144{
145 K7_NOP1,
146 K7_NOP2,
147 K7_NOP3,
148 K7_NOP4,
149 K7_NOP5,
150 K7_NOP6,
151 K7_NOP7,
152 K7_NOP8,
153 K7_NOP5_ATOMIC
154};
155static const unsigned char * const k7_nops[ASM_NOP_MAX+2] =
156{
157 NULL,
158 k7nops,
159 k7nops + 1,
160 k7nops + 1 + 2,
161 k7nops + 1 + 2 + 3,
162 k7nops + 1 + 2 + 3 + 4,
163 k7nops + 1 + 2 + 3 + 4 + 5,
164 k7nops + 1 + 2 + 3 + 4 + 5 + 6,
165 k7nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
166 k7nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
167};
168#endif
169
170#ifdef P6_NOP1
171static const unsigned char p6nops[] =
172{
173 P6_NOP1,
174 P6_NOP2,
175 P6_NOP3,
176 P6_NOP4,
177 P6_NOP5,
178 P6_NOP6,
179 P6_NOP7,
180 P6_NOP8,
181 P6_NOP5_ATOMIC
182};
183static const unsigned char * const p6_nops[ASM_NOP_MAX+2] =
184{
185 NULL,
186 p6nops,
187 p6nops + 1,
188 p6nops + 1 + 2,
189 p6nops + 1 + 2 + 3,
190 p6nops + 1 + 2 + 3 + 4,
191 p6nops + 1 + 2 + 3 + 4 + 5,
192 p6nops + 1 + 2 + 3 + 4 + 5 + 6,
193 p6nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
194 p6nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
195};
196#endif
197
198/* Initialize these to a safe default */
199#ifdef CONFIG_X86_64
200const unsigned char * const *ideal_nops = p6_nops;
201#else
202const unsigned char * const *ideal_nops = intel_nops;
203#endif
204
205void __init arch_init_ideal_nops(void)
206{
207 switch (boot_cpu_data.x86_vendor) {
208 case X86_VENDOR_INTEL:
209 /*
210 * Due to a decoder implementation quirk, some
211 * specific Intel CPUs actually perform better with
212 * the "k8_nops" than with the SDM-recommended NOPs.
213 */
214 if (boot_cpu_data.x86 == 6 &&
215 boot_cpu_data.x86_model >= 0x0f &&
216 boot_cpu_data.x86_model != 0x1c &&
217 boot_cpu_data.x86_model != 0x26 &&
218 boot_cpu_data.x86_model != 0x27 &&
219 boot_cpu_data.x86_model < 0x30) {
220 ideal_nops = k8_nops;
221 } else if (boot_cpu_has(X86_FEATURE_NOPL)) {
222 ideal_nops = p6_nops;
223 } else {
224#ifdef CONFIG_X86_64
225 ideal_nops = k8_nops;
226#else
227 ideal_nops = intel_nops;
228#endif
229 }
230 break;
231
232 case X86_VENDOR_HYGON:
233 ideal_nops = p6_nops;
234 return;
235
236 case X86_VENDOR_AMD:
237 if (boot_cpu_data.x86 > 0xf) {
238 ideal_nops = p6_nops;
239 return;
240 }
241
242 fallthrough;
243
244 default:
245#ifdef CONFIG_X86_64
246 ideal_nops = k8_nops;
247#else
248 if (boot_cpu_has(X86_FEATURE_K8))
249 ideal_nops = k8_nops;
250 else if (boot_cpu_has(X86_FEATURE_K7))
251 ideal_nops = k7_nops;
252 else
253 ideal_nops = intel_nops;
254#endif
255 }
256}
257
258/* Use this to add nops to a buffer, then text_poke the whole buffer. */
259static void __init_or_module add_nops(void *insns, unsigned int len)
260{
261 while (len > 0) {
262 unsigned int noplen = len;
263 if (noplen > ASM_NOP_MAX)
264 noplen = ASM_NOP_MAX;
265 memcpy(insns, ideal_nops[noplen], noplen);
266 insns += noplen;
267 len -= noplen;
268 }
269}
270
271extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
272extern s32 __smp_locks[], __smp_locks_end[];
273void text_poke_early(void *addr, const void *opcode, size_t len);
274
275/*
276 * Are we looking at a near JMP with a 1 or 4-byte displacement.
277 */
278static inline bool is_jmp(const u8 opcode)
279{
280 return opcode == 0xeb || opcode == 0xe9;
281}
282
283static void __init_or_module
284recompute_jump(struct alt_instr *a, u8 *orig_insn, u8 *repl_insn, u8 *insn_buff)
285{
286 u8 *next_rip, *tgt_rip;
287 s32 n_dspl, o_dspl;
288 int repl_len;
289
290 if (a->replacementlen != 5)
291 return;
292
293 o_dspl = *(s32 *)(insn_buff + 1);
294
295 /* next_rip of the replacement JMP */
296 next_rip = repl_insn + a->replacementlen;
297 /* target rip of the replacement JMP */
298 tgt_rip = next_rip + o_dspl;
299 n_dspl = tgt_rip - orig_insn;
300
301 DPRINTK("target RIP: %px, new_displ: 0x%x", tgt_rip, n_dspl);
302
303 if (tgt_rip - orig_insn >= 0) {
304 if (n_dspl - 2 <= 127)
305 goto two_byte_jmp;
306 else
307 goto five_byte_jmp;
308 /* negative offset */
309 } else {
310 if (((n_dspl - 2) & 0xff) == (n_dspl - 2))
311 goto two_byte_jmp;
312 else
313 goto five_byte_jmp;
314 }
315
316two_byte_jmp:
317 n_dspl -= 2;
318
319 insn_buff[0] = 0xeb;
320 insn_buff[1] = (s8)n_dspl;
321 add_nops(insn_buff + 2, 3);
322
323 repl_len = 2;
324 goto done;
325
326five_byte_jmp:
327 n_dspl -= 5;
328
329 insn_buff[0] = 0xe9;
330 *(s32 *)&insn_buff[1] = n_dspl;
331
332 repl_len = 5;
333
334done:
335
336 DPRINTK("final displ: 0x%08x, JMP 0x%lx",
337 n_dspl, (unsigned long)orig_insn + n_dspl + repl_len);
338}
339
340/*
341 * "noinline" to cause control flow change and thus invalidate I$ and
342 * cause refetch after modification.
343 */
344static void __init_or_module noinline optimize_nops(struct alt_instr *a, u8 *instr)
345{
346 unsigned long flags;
347 int i;
348
349 for (i = 0; i < a->padlen; i++) {
350 if (instr[i] != 0x90)
351 return;
352 }
353
354 local_irq_save(flags);
355 add_nops(instr + (a->instrlen - a->padlen), a->padlen);
356 local_irq_restore(flags);
357
358 DUMP_BYTES(instr, a->instrlen, "%px: [%d:%d) optimized NOPs: ",
359 instr, a->instrlen - a->padlen, a->padlen);
360}
361
362/*
363 * Replace instructions with better alternatives for this CPU type. This runs
364 * before SMP is initialized to avoid SMP problems with self modifying code.
365 * This implies that asymmetric systems where APs have less capabilities than
366 * the boot processor are not handled. Tough. Make sure you disable such
367 * features by hand.
368 *
369 * Marked "noinline" to cause control flow change and thus insn cache
370 * to refetch changed I$ lines.
371 */
372void __init_or_module noinline apply_alternatives(struct alt_instr *start,
373 struct alt_instr *end)
374{
375 struct alt_instr *a;
376 u8 *instr, *replacement;
377 u8 insn_buff[MAX_PATCH_LEN];
378
379 DPRINTK("alt table %px, -> %px", start, end);
380 /*
381 * The scan order should be from start to end. A later scanned
382 * alternative code can overwrite previously scanned alternative code.
383 * Some kernel functions (e.g. memcpy, memset, etc) use this order to
384 * patch code.
385 *
386 * So be careful if you want to change the scan order to any other
387 * order.
388 */
389 for (a = start; a < end; a++) {
390 int insn_buff_sz = 0;
391
392 instr = (u8 *)&a->instr_offset + a->instr_offset;
393 replacement = (u8 *)&a->repl_offset + a->repl_offset;
394 BUG_ON(a->instrlen > sizeof(insn_buff));
395 BUG_ON(a->cpuid >= (NCAPINTS + NBUGINTS) * 32);
396 if (!boot_cpu_has(a->cpuid)) {
397 if (a->padlen > 1)
398 optimize_nops(a, instr);
399
400 continue;
401 }
402
403 DPRINTK("feat: %d*32+%d, old: (%pS (%px) len: %d), repl: (%px, len: %d), pad: %d",
404 a->cpuid >> 5,
405 a->cpuid & 0x1f,
406 instr, instr, a->instrlen,
407 replacement, a->replacementlen, a->padlen);
408
409 DUMP_BYTES(instr, a->instrlen, "%px: old_insn: ", instr);
410 DUMP_BYTES(replacement, a->replacementlen, "%px: rpl_insn: ", replacement);
411
412 memcpy(insn_buff, replacement, a->replacementlen);
413 insn_buff_sz = a->replacementlen;
414
415 /*
416 * 0xe8 is a relative jump; fix the offset.
417 *
418 * Instruction length is checked before the opcode to avoid
419 * accessing uninitialized bytes for zero-length replacements.
420 */
421 if (a->replacementlen == 5 && *insn_buff == 0xe8) {
422 *(s32 *)(insn_buff + 1) += replacement - instr;
423 DPRINTK("Fix CALL offset: 0x%x, CALL 0x%lx",
424 *(s32 *)(insn_buff + 1),
425 (unsigned long)instr + *(s32 *)(insn_buff + 1) + 5);
426 }
427
428 if (a->replacementlen && is_jmp(replacement[0]))
429 recompute_jump(a, instr, replacement, insn_buff);
430
431 if (a->instrlen > a->replacementlen) {
432 add_nops(insn_buff + a->replacementlen,
433 a->instrlen - a->replacementlen);
434 insn_buff_sz += a->instrlen - a->replacementlen;
435 }
436 DUMP_BYTES(insn_buff, insn_buff_sz, "%px: final_insn: ", instr);
437
438 text_poke_early(instr, insn_buff, insn_buff_sz);
439 }
440}
441
442#ifdef CONFIG_SMP
443static void alternatives_smp_lock(const s32 *start, const s32 *end,
444 u8 *text, u8 *text_end)
445{
446 const s32 *poff;
447
448 for (poff = start; poff < end; poff++) {
449 u8 *ptr = (u8 *)poff + *poff;
450
451 if (!*poff || ptr < text || ptr >= text_end)
452 continue;
453 /* turn DS segment override prefix into lock prefix */
454 if (*ptr == 0x3e)
455 text_poke(ptr, ((unsigned char []){0xf0}), 1);
456 }
457}
458
459static void alternatives_smp_unlock(const s32 *start, const s32 *end,
460 u8 *text, u8 *text_end)
461{
462 const s32 *poff;
463
464 for (poff = start; poff < end; poff++) {
465 u8 *ptr = (u8 *)poff + *poff;
466
467 if (!*poff || ptr < text || ptr >= text_end)
468 continue;
469 /* turn lock prefix into DS segment override prefix */
470 if (*ptr == 0xf0)
471 text_poke(ptr, ((unsigned char []){0x3E}), 1);
472 }
473}
474
475struct smp_alt_module {
476 /* what is this ??? */
477 struct module *mod;
478 char *name;
479
480 /* ptrs to lock prefixes */
481 const s32 *locks;
482 const s32 *locks_end;
483
484 /* .text segment, needed to avoid patching init code ;) */
485 u8 *text;
486 u8 *text_end;
487
488 struct list_head next;
489};
490static LIST_HEAD(smp_alt_modules);
491static bool uniproc_patched = false; /* protected by text_mutex */
492
493void __init_or_module alternatives_smp_module_add(struct module *mod,
494 char *name,
495 void *locks, void *locks_end,
496 void *text, void *text_end)
497{
498 struct smp_alt_module *smp;
499
500 mutex_lock(&text_mutex);
501 if (!uniproc_patched)
502 goto unlock;
503
504 if (num_possible_cpus() == 1)
505 /* Don't bother remembering, we'll never have to undo it. */
506 goto smp_unlock;
507
508 smp = kzalloc(sizeof(*smp), GFP_KERNEL);
509 if (NULL == smp)
510 /* we'll run the (safe but slow) SMP code then ... */
511 goto unlock;
512
513 smp->mod = mod;
514 smp->name = name;
515 smp->locks = locks;
516 smp->locks_end = locks_end;
517 smp->text = text;
518 smp->text_end = text_end;
519 DPRINTK("locks %p -> %p, text %p -> %p, name %s\n",
520 smp->locks, smp->locks_end,
521 smp->text, smp->text_end, smp->name);
522
523 list_add_tail(&smp->next, &smp_alt_modules);
524smp_unlock:
525 alternatives_smp_unlock(locks, locks_end, text, text_end);
526unlock:
527 mutex_unlock(&text_mutex);
528}
529
530void __init_or_module alternatives_smp_module_del(struct module *mod)
531{
532 struct smp_alt_module *item;
533
534 mutex_lock(&text_mutex);
535 list_for_each_entry(item, &smp_alt_modules, next) {
536 if (mod != item->mod)
537 continue;
538 list_del(&item->next);
539 kfree(item);
540 break;
541 }
542 mutex_unlock(&text_mutex);
543}
544
545void alternatives_enable_smp(void)
546{
547 struct smp_alt_module *mod;
548
549 /* Why bother if there are no other CPUs? */
550 BUG_ON(num_possible_cpus() == 1);
551
552 mutex_lock(&text_mutex);
553
554 if (uniproc_patched) {
555 pr_info("switching to SMP code\n");
556 BUG_ON(num_online_cpus() != 1);
557 clear_cpu_cap(&boot_cpu_data, X86_FEATURE_UP);
558 clear_cpu_cap(&cpu_data(0), X86_FEATURE_UP);
559 list_for_each_entry(mod, &smp_alt_modules, next)
560 alternatives_smp_lock(mod->locks, mod->locks_end,
561 mod->text, mod->text_end);
562 uniproc_patched = false;
563 }
564 mutex_unlock(&text_mutex);
565}
566
567/*
568 * Return 1 if the address range is reserved for SMP-alternatives.
569 * Must hold text_mutex.
570 */
571int alternatives_text_reserved(void *start, void *end)
572{
573 struct smp_alt_module *mod;
574 const s32 *poff;
575 u8 *text_start = start;
576 u8 *text_end = end;
577
578 lockdep_assert_held(&text_mutex);
579
580 list_for_each_entry(mod, &smp_alt_modules, next) {
581 if (mod->text > text_end || mod->text_end < text_start)
582 continue;
583 for (poff = mod->locks; poff < mod->locks_end; poff++) {
584 const u8 *ptr = (const u8 *)poff + *poff;
585
586 if (text_start <= ptr && text_end > ptr)
587 return 1;
588 }
589 }
590
591 return 0;
592}
593#endif /* CONFIG_SMP */
594
595#ifdef CONFIG_PARAVIRT
596void __init_or_module apply_paravirt(struct paravirt_patch_site *start,
597 struct paravirt_patch_site *end)
598{
599 struct paravirt_patch_site *p;
600 char insn_buff[MAX_PATCH_LEN];
601
602 for (p = start; p < end; p++) {
603 unsigned int used;
604
605 BUG_ON(p->len > MAX_PATCH_LEN);
606 /* prep the buffer with the original instructions */
607 memcpy(insn_buff, p->instr, p->len);
608 used = pv_ops.init.patch(p->type, insn_buff, (unsigned long)p->instr, p->len);
609
610 BUG_ON(used > p->len);
611
612 /* Pad the rest with nops */
613 add_nops(insn_buff + used, p->len - used);
614 text_poke_early(p->instr, insn_buff, p->len);
615 }
616}
617extern struct paravirt_patch_site __start_parainstructions[],
618 __stop_parainstructions[];
619#endif /* CONFIG_PARAVIRT */
620
621/*
622 * Self-test for the INT3 based CALL emulation code.
623 *
624 * This exercises int3_emulate_call() to make sure INT3 pt_regs are set up
625 * properly and that there is a stack gap between the INT3 frame and the
626 * previous context. Without this gap doing a virtual PUSH on the interrupted
627 * stack would corrupt the INT3 IRET frame.
628 *
629 * See entry_{32,64}.S for more details.
630 */
631
632/*
633 * We define the int3_magic() function in assembly to control the calling
634 * convention such that we can 'call' it from assembly.
635 */
636
637extern void int3_magic(unsigned int *ptr); /* defined in asm */
638
639asm (
640" .pushsection .init.text, \"ax\", @progbits\n"
641" .type int3_magic, @function\n"
642"int3_magic:\n"
643" movl $1, (%" _ASM_ARG1 ")\n"
644" ret\n"
645" .size int3_magic, .-int3_magic\n"
646" .popsection\n"
647);
648
649extern __initdata unsigned long int3_selftest_ip; /* defined in asm below */
650
651static int __init
652int3_exception_notify(struct notifier_block *self, unsigned long val, void *data)
653{
654 struct die_args *args = data;
655 struct pt_regs *regs = args->regs;
656
657 if (!regs || user_mode(regs))
658 return NOTIFY_DONE;
659
660 if (val != DIE_INT3)
661 return NOTIFY_DONE;
662
663 if (regs->ip - INT3_INSN_SIZE != int3_selftest_ip)
664 return NOTIFY_DONE;
665
666 int3_emulate_call(regs, (unsigned long)&int3_magic);
667 return NOTIFY_STOP;
668}
669
670static void __init int3_selftest(void)
671{
672 static __initdata struct notifier_block int3_exception_nb = {
673 .notifier_call = int3_exception_notify,
674 .priority = INT_MAX-1, /* last */
675 };
676 unsigned int val = 0;
677
678 BUG_ON(register_die_notifier(&int3_exception_nb));
679
680 /*
681 * Basically: int3_magic(&val); but really complicated :-)
682 *
683 * Stick the address of the INT3 instruction into int3_selftest_ip,
684 * then trigger the INT3, padded with NOPs to match a CALL instruction
685 * length.
686 */
687 asm volatile ("1: int3; nop; nop; nop; nop\n\t"
688 ".pushsection .init.data,\"aw\"\n\t"
689 ".align " __ASM_SEL(4, 8) "\n\t"
690 ".type int3_selftest_ip, @object\n\t"
691 ".size int3_selftest_ip, " __ASM_SEL(4, 8) "\n\t"
692 "int3_selftest_ip:\n\t"
693 __ASM_SEL(.long, .quad) " 1b\n\t"
694 ".popsection\n\t"
695 : ASM_CALL_CONSTRAINT
696 : __ASM_SEL_RAW(a, D) (&val)
697 : "memory");
698
699 BUG_ON(val != 1);
700
701 unregister_die_notifier(&int3_exception_nb);
702}
703
704void __init alternative_instructions(void)
705{
706 int3_selftest();
707
708 /*
709 * The patching is not fully atomic, so try to avoid local
710 * interruptions that might execute the to be patched code.
711 * Other CPUs are not running.
712 */
713 stop_nmi();
714
715 /*
716 * Don't stop machine check exceptions while patching.
717 * MCEs only happen when something got corrupted and in this
718 * case we must do something about the corruption.
719 * Ignoring it is worse than an unlikely patching race.
720 * Also machine checks tend to be broadcast and if one CPU
721 * goes into machine check the others follow quickly, so we don't
722 * expect a machine check to cause undue problems during to code
723 * patching.
724 */
725
726 apply_alternatives(__alt_instructions, __alt_instructions_end);
727
728#ifdef CONFIG_SMP
729 /* Patch to UP if other cpus not imminent. */
730 if (!noreplace_smp && (num_present_cpus() == 1 || setup_max_cpus <= 1)) {
731 uniproc_patched = true;
732 alternatives_smp_module_add(NULL, "core kernel",
733 __smp_locks, __smp_locks_end,
734 _text, _etext);
735 }
736
737 if (!uniproc_patched || num_possible_cpus() == 1) {
738 free_init_pages("SMP alternatives",
739 (unsigned long)__smp_locks,
740 (unsigned long)__smp_locks_end);
741 }
742#endif
743
744 apply_paravirt(__parainstructions, __parainstructions_end);
745
746 restart_nmi();
747 alternatives_patched = 1;
748}
749
750/**
751 * text_poke_early - Update instructions on a live kernel at boot time
752 * @addr: address to modify
753 * @opcode: source of the copy
754 * @len: length to copy
755 *
756 * When you use this code to patch more than one byte of an instruction
757 * you need to make sure that other CPUs cannot execute this code in parallel.
758 * Also no thread must be currently preempted in the middle of these
759 * instructions. And on the local CPU you need to be protected against NMI or
760 * MCE handlers seeing an inconsistent instruction while you patch.
761 */
762void __init_or_module text_poke_early(void *addr, const void *opcode,
763 size_t len)
764{
765 unsigned long flags;
766
767 if (boot_cpu_has(X86_FEATURE_NX) &&
768 is_module_text_address((unsigned long)addr)) {
769 /*
770 * Modules text is marked initially as non-executable, so the
771 * code cannot be running and speculative code-fetches are
772 * prevented. Just change the code.
773 */
774 memcpy(addr, opcode, len);
775 } else {
776 local_irq_save(flags);
777 memcpy(addr, opcode, len);
778 local_irq_restore(flags);
779 sync_core();
780
781 /*
782 * Could also do a CLFLUSH here to speed up CPU recovery; but
783 * that causes hangs on some VIA CPUs.
784 */
785 }
786}
787
788typedef struct {
789 struct mm_struct *mm;
790} temp_mm_state_t;
791
792/*
793 * Using a temporary mm allows to set temporary mappings that are not accessible
794 * by other CPUs. Such mappings are needed to perform sensitive memory writes
795 * that override the kernel memory protections (e.g., W^X), without exposing the
796 * temporary page-table mappings that are required for these write operations to
797 * other CPUs. Using a temporary mm also allows to avoid TLB shootdowns when the
798 * mapping is torn down.
799 *
800 * Context: The temporary mm needs to be used exclusively by a single core. To
801 * harden security IRQs must be disabled while the temporary mm is
802 * loaded, thereby preventing interrupt handler bugs from overriding
803 * the kernel memory protection.
804 */
805static inline temp_mm_state_t use_temporary_mm(struct mm_struct *mm)
806{
807 temp_mm_state_t temp_state;
808
809 lockdep_assert_irqs_disabled();
810 temp_state.mm = this_cpu_read(cpu_tlbstate.loaded_mm);
811 switch_mm_irqs_off(NULL, mm, current);
812
813 /*
814 * If breakpoints are enabled, disable them while the temporary mm is
815 * used. Userspace might set up watchpoints on addresses that are used
816 * in the temporary mm, which would lead to wrong signals being sent or
817 * crashes.
818 *
819 * Note that breakpoints are not disabled selectively, which also causes
820 * kernel breakpoints (e.g., perf's) to be disabled. This might be
821 * undesirable, but still seems reasonable as the code that runs in the
822 * temporary mm should be short.
823 */
824 if (hw_breakpoint_active())
825 hw_breakpoint_disable();
826
827 return temp_state;
828}
829
830static inline void unuse_temporary_mm(temp_mm_state_t prev_state)
831{
832 lockdep_assert_irqs_disabled();
833 switch_mm_irqs_off(NULL, prev_state.mm, current);
834
835 /*
836 * Restore the breakpoints if they were disabled before the temporary mm
837 * was loaded.
838 */
839 if (hw_breakpoint_active())
840 hw_breakpoint_restore();
841}
842
843__ro_after_init struct mm_struct *poking_mm;
844__ro_after_init unsigned long poking_addr;
845
846static void *__text_poke(void *addr, const void *opcode, size_t len)
847{
848 bool cross_page_boundary = offset_in_page(addr) + len > PAGE_SIZE;
849 struct page *pages[2] = {NULL};
850 temp_mm_state_t prev;
851 unsigned long flags;
852 pte_t pte, *ptep;
853 spinlock_t *ptl;
854 pgprot_t pgprot;
855
856 /*
857 * While boot memory allocator is running we cannot use struct pages as
858 * they are not yet initialized. There is no way to recover.
859 */
860 BUG_ON(!after_bootmem);
861
862 if (!core_kernel_text((unsigned long)addr)) {
863 pages[0] = vmalloc_to_page(addr);
864 if (cross_page_boundary)
865 pages[1] = vmalloc_to_page(addr + PAGE_SIZE);
866 } else {
867 pages[0] = virt_to_page(addr);
868 WARN_ON(!PageReserved(pages[0]));
869 if (cross_page_boundary)
870 pages[1] = virt_to_page(addr + PAGE_SIZE);
871 }
872 /*
873 * If something went wrong, crash and burn since recovery paths are not
874 * implemented.
875 */
876 BUG_ON(!pages[0] || (cross_page_boundary && !pages[1]));
877
878 /*
879 * Map the page without the global bit, as TLB flushing is done with
880 * flush_tlb_mm_range(), which is intended for non-global PTEs.
881 */
882 pgprot = __pgprot(pgprot_val(PAGE_KERNEL) & ~_PAGE_GLOBAL);
883
884 /*
885 * The lock is not really needed, but this allows to avoid open-coding.
886 */
887 ptep = get_locked_pte(poking_mm, poking_addr, &ptl);
888
889 /*
890 * This must not fail; preallocated in poking_init().
891 */
892 VM_BUG_ON(!ptep);
893
894 local_irq_save(flags);
895
896 pte = mk_pte(pages[0], pgprot);
897 set_pte_at(poking_mm, poking_addr, ptep, pte);
898
899 if (cross_page_boundary) {
900 pte = mk_pte(pages[1], pgprot);
901 set_pte_at(poking_mm, poking_addr + PAGE_SIZE, ptep + 1, pte);
902 }
903
904 /*
905 * Loading the temporary mm behaves as a compiler barrier, which
906 * guarantees that the PTE will be set at the time memcpy() is done.
907 */
908 prev = use_temporary_mm(poking_mm);
909
910 kasan_disable_current();
911 memcpy((u8 *)poking_addr + offset_in_page(addr), opcode, len);
912 kasan_enable_current();
913
914 /*
915 * Ensure that the PTE is only cleared after the instructions of memcpy
916 * were issued by using a compiler barrier.
917 */
918 barrier();
919
920 pte_clear(poking_mm, poking_addr, ptep);
921 if (cross_page_boundary)
922 pte_clear(poking_mm, poking_addr + PAGE_SIZE, ptep + 1);
923
924 /*
925 * Loading the previous page-table hierarchy requires a serializing
926 * instruction that already allows the core to see the updated version.
927 * Xen-PV is assumed to serialize execution in a similar manner.
928 */
929 unuse_temporary_mm(prev);
930
931 /*
932 * Flushing the TLB might involve IPIs, which would require enabled
933 * IRQs, but not if the mm is not used, as it is in this point.
934 */
935 flush_tlb_mm_range(poking_mm, poking_addr, poking_addr +
936 (cross_page_boundary ? 2 : 1) * PAGE_SIZE,
937 PAGE_SHIFT, false);
938
939 /*
940 * If the text does not match what we just wrote then something is
941 * fundamentally screwy; there's nothing we can really do about that.
942 */
943 BUG_ON(memcmp(addr, opcode, len));
944
945 local_irq_restore(flags);
946 pte_unmap_unlock(ptep, ptl);
947 return addr;
948}
949
950/**
951 * text_poke - Update instructions on a live kernel
952 * @addr: address to modify
953 * @opcode: source of the copy
954 * @len: length to copy
955 *
956 * Only atomic text poke/set should be allowed when not doing early patching.
957 * It means the size must be writable atomically and the address must be aligned
958 * in a way that permits an atomic write. It also makes sure we fit on a single
959 * page.
960 *
961 * Note that the caller must ensure that if the modified code is part of a
962 * module, the module would not be removed during poking. This can be achieved
963 * by registering a module notifier, and ordering module removal and patching
964 * trough a mutex.
965 */
966void *text_poke(void *addr, const void *opcode, size_t len)
967{
968 lockdep_assert_held(&text_mutex);
969
970 return __text_poke(addr, opcode, len);
971}
972
973/**
974 * text_poke_kgdb - Update instructions on a live kernel by kgdb
975 * @addr: address to modify
976 * @opcode: source of the copy
977 * @len: length to copy
978 *
979 * Only atomic text poke/set should be allowed when not doing early patching.
980 * It means the size must be writable atomically and the address must be aligned
981 * in a way that permits an atomic write. It also makes sure we fit on a single
982 * page.
983 *
984 * Context: should only be used by kgdb, which ensures no other core is running,
985 * despite the fact it does not hold the text_mutex.
986 */
987void *text_poke_kgdb(void *addr, const void *opcode, size_t len)
988{
989 return __text_poke(addr, opcode, len);
990}
991
992static void do_sync_core(void *info)
993{
994 sync_core();
995}
996
997void text_poke_sync(void)
998{
999 on_each_cpu(do_sync_core, NULL, 1);
1000}
1001
1002struct text_poke_loc {
1003 s32 rel_addr; /* addr := _stext + rel_addr */
1004 s32 rel32;
1005 u8 opcode;
1006 const u8 text[POKE_MAX_OPCODE_SIZE];
1007 u8 old;
1008};
1009
1010struct bp_patching_desc {
1011 struct text_poke_loc *vec;
1012 int nr_entries;
1013 atomic_t refs;
1014};
1015
1016static struct bp_patching_desc *bp_desc;
1017
1018static __always_inline
1019struct bp_patching_desc *try_get_desc(struct bp_patching_desc **descp)
1020{
1021 struct bp_patching_desc *desc = __READ_ONCE(*descp); /* rcu_dereference */
1022
1023 if (!desc || !arch_atomic_inc_not_zero(&desc->refs))
1024 return NULL;
1025
1026 return desc;
1027}
1028
1029static __always_inline void put_desc(struct bp_patching_desc *desc)
1030{
1031 smp_mb__before_atomic();
1032 arch_atomic_dec(&desc->refs);
1033}
1034
1035static __always_inline void *text_poke_addr(struct text_poke_loc *tp)
1036{
1037 return _stext + tp->rel_addr;
1038}
1039
1040static __always_inline int patch_cmp(const void *key, const void *elt)
1041{
1042 struct text_poke_loc *tp = (struct text_poke_loc *) elt;
1043
1044 if (key < text_poke_addr(tp))
1045 return -1;
1046 if (key > text_poke_addr(tp))
1047 return 1;
1048 return 0;
1049}
1050
1051noinstr int poke_int3_handler(struct pt_regs *regs)
1052{
1053 struct bp_patching_desc *desc;
1054 struct text_poke_loc *tp;
1055 int len, ret = 0;
1056 void *ip;
1057
1058 if (user_mode(regs))
1059 return 0;
1060
1061 /*
1062 * Having observed our INT3 instruction, we now must observe
1063 * bp_desc:
1064 *
1065 * bp_desc = desc INT3
1066 * WMB RMB
1067 * write INT3 if (desc)
1068 */
1069 smp_rmb();
1070
1071 desc = try_get_desc(&bp_desc);
1072 if (!desc)
1073 return 0;
1074
1075 /*
1076 * Discount the INT3. See text_poke_bp_batch().
1077 */
1078 ip = (void *) regs->ip - INT3_INSN_SIZE;
1079
1080 /*
1081 * Skip the binary search if there is a single member in the vector.
1082 */
1083 if (unlikely(desc->nr_entries > 1)) {
1084 tp = __inline_bsearch(ip, desc->vec, desc->nr_entries,
1085 sizeof(struct text_poke_loc),
1086 patch_cmp);
1087 if (!tp)
1088 goto out_put;
1089 } else {
1090 tp = desc->vec;
1091 if (text_poke_addr(tp) != ip)
1092 goto out_put;
1093 }
1094
1095 len = text_opcode_size(tp->opcode);
1096 ip += len;
1097
1098 switch (tp->opcode) {
1099 case INT3_INSN_OPCODE:
1100 /*
1101 * Someone poked an explicit INT3, they'll want to handle it,
1102 * do not consume.
1103 */
1104 goto out_put;
1105
1106 case CALL_INSN_OPCODE:
1107 int3_emulate_call(regs, (long)ip + tp->rel32);
1108 break;
1109
1110 case JMP32_INSN_OPCODE:
1111 case JMP8_INSN_OPCODE:
1112 int3_emulate_jmp(regs, (long)ip + tp->rel32);
1113 break;
1114
1115 default:
1116 BUG();
1117 }
1118
1119 ret = 1;
1120
1121out_put:
1122 put_desc(desc);
1123 return ret;
1124}
1125
1126#define TP_VEC_MAX (PAGE_SIZE / sizeof(struct text_poke_loc))
1127static struct text_poke_loc tp_vec[TP_VEC_MAX];
1128static int tp_vec_nr;
1129
1130/**
1131 * text_poke_bp_batch() -- update instructions on live kernel on SMP
1132 * @tp: vector of instructions to patch
1133 * @nr_entries: number of entries in the vector
1134 *
1135 * Modify multi-byte instruction by using int3 breakpoint on SMP.
1136 * We completely avoid stop_machine() here, and achieve the
1137 * synchronization using int3 breakpoint.
1138 *
1139 * The way it is done:
1140 * - For each entry in the vector:
1141 * - add a int3 trap to the address that will be patched
1142 * - sync cores
1143 * - For each entry in the vector:
1144 * - update all but the first byte of the patched range
1145 * - sync cores
1146 * - For each entry in the vector:
1147 * - replace the first byte (int3) by the first byte of
1148 * replacing opcode
1149 * - sync cores
1150 */
1151static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries)
1152{
1153 struct bp_patching_desc desc = {
1154 .vec = tp,
1155 .nr_entries = nr_entries,
1156 .refs = ATOMIC_INIT(1),
1157 };
1158 unsigned char int3 = INT3_INSN_OPCODE;
1159 unsigned int i;
1160 int do_sync;
1161
1162 lockdep_assert_held(&text_mutex);
1163
1164 smp_store_release(&bp_desc, &desc); /* rcu_assign_pointer */
1165
1166 /*
1167 * Corresponding read barrier in int3 notifier for making sure the
1168 * nr_entries and handler are correctly ordered wrt. patching.
1169 */
1170 smp_wmb();
1171
1172 /*
1173 * First step: add a int3 trap to the address that will be patched.
1174 */
1175 for (i = 0; i < nr_entries; i++) {
1176 tp[i].old = *(u8 *)text_poke_addr(&tp[i]);
1177 text_poke(text_poke_addr(&tp[i]), &int3, INT3_INSN_SIZE);
1178 }
1179
1180 text_poke_sync();
1181
1182 /*
1183 * Second step: update all but the first byte of the patched range.
1184 */
1185 for (do_sync = 0, i = 0; i < nr_entries; i++) {
1186 u8 old[POKE_MAX_OPCODE_SIZE] = { tp[i].old, };
1187 int len = text_opcode_size(tp[i].opcode);
1188
1189 if (len - INT3_INSN_SIZE > 0) {
1190 memcpy(old + INT3_INSN_SIZE,
1191 text_poke_addr(&tp[i]) + INT3_INSN_SIZE,
1192 len - INT3_INSN_SIZE);
1193 text_poke(text_poke_addr(&tp[i]) + INT3_INSN_SIZE,
1194 (const char *)tp[i].text + INT3_INSN_SIZE,
1195 len - INT3_INSN_SIZE);
1196 do_sync++;
1197 }
1198
1199 /*
1200 * Emit a perf event to record the text poke, primarily to
1201 * support Intel PT decoding which must walk the executable code
1202 * to reconstruct the trace. The flow up to here is:
1203 * - write INT3 byte
1204 * - IPI-SYNC
1205 * - write instruction tail
1206 * At this point the actual control flow will be through the
1207 * INT3 and handler and not hit the old or new instruction.
1208 * Intel PT outputs FUP/TIP packets for the INT3, so the flow
1209 * can still be decoded. Subsequently:
1210 * - emit RECORD_TEXT_POKE with the new instruction
1211 * - IPI-SYNC
1212 * - write first byte
1213 * - IPI-SYNC
1214 * So before the text poke event timestamp, the decoder will see
1215 * either the old instruction flow or FUP/TIP of INT3. After the
1216 * text poke event timestamp, the decoder will see either the
1217 * new instruction flow or FUP/TIP of INT3. Thus decoders can
1218 * use the timestamp as the point at which to modify the
1219 * executable code.
1220 * The old instruction is recorded so that the event can be
1221 * processed forwards or backwards.
1222 */
1223 perf_event_text_poke(text_poke_addr(&tp[i]), old, len,
1224 tp[i].text, len);
1225 }
1226
1227 if (do_sync) {
1228 /*
1229 * According to Intel, this core syncing is very likely
1230 * not necessary and we'd be safe even without it. But
1231 * better safe than sorry (plus there's not only Intel).
1232 */
1233 text_poke_sync();
1234 }
1235
1236 /*
1237 * Third step: replace the first byte (int3) by the first byte of
1238 * replacing opcode.
1239 */
1240 for (do_sync = 0, i = 0; i < nr_entries; i++) {
1241 if (tp[i].text[0] == INT3_INSN_OPCODE)
1242 continue;
1243
1244 text_poke(text_poke_addr(&tp[i]), tp[i].text, INT3_INSN_SIZE);
1245 do_sync++;
1246 }
1247
1248 if (do_sync)
1249 text_poke_sync();
1250
1251 /*
1252 * Remove and synchronize_rcu(), except we have a very primitive
1253 * refcount based completion.
1254 */
1255 WRITE_ONCE(bp_desc, NULL); /* RCU_INIT_POINTER */
1256 if (!atomic_dec_and_test(&desc.refs))
1257 atomic_cond_read_acquire(&desc.refs, !VAL);
1258}
1259
1260static void text_poke_loc_init(struct text_poke_loc *tp, void *addr,
1261 const void *opcode, size_t len, const void *emulate)
1262{
1263 struct insn insn;
1264
1265 memcpy((void *)tp->text, opcode, len);
1266 if (!emulate)
1267 emulate = opcode;
1268
1269 kernel_insn_init(&insn, emulate, MAX_INSN_SIZE);
1270 insn_get_length(&insn);
1271
1272 BUG_ON(!insn_complete(&insn));
1273 BUG_ON(len != insn.length);
1274
1275 tp->rel_addr = addr - (void *)_stext;
1276 tp->opcode = insn.opcode.bytes[0];
1277
1278 switch (tp->opcode) {
1279 case INT3_INSN_OPCODE:
1280 break;
1281
1282 case CALL_INSN_OPCODE:
1283 case JMP32_INSN_OPCODE:
1284 case JMP8_INSN_OPCODE:
1285 tp->rel32 = insn.immediate.value;
1286 break;
1287
1288 default: /* assume NOP */
1289 switch (len) {
1290 case 2: /* NOP2 -- emulate as JMP8+0 */
1291 BUG_ON(memcmp(emulate, ideal_nops[len], len));
1292 tp->opcode = JMP8_INSN_OPCODE;
1293 tp->rel32 = 0;
1294 break;
1295
1296 case 5: /* NOP5 -- emulate as JMP32+0 */
1297 BUG_ON(memcmp(emulate, ideal_nops[NOP_ATOMIC5], len));
1298 tp->opcode = JMP32_INSN_OPCODE;
1299 tp->rel32 = 0;
1300 break;
1301
1302 default: /* unknown instruction */
1303 BUG();
1304 }
1305 break;
1306 }
1307}
1308
1309/*
1310 * We hard rely on the tp_vec being ordered; ensure this is so by flushing
1311 * early if needed.
1312 */
1313static bool tp_order_fail(void *addr)
1314{
1315 struct text_poke_loc *tp;
1316
1317 if (!tp_vec_nr)
1318 return false;
1319
1320 if (!addr) /* force */
1321 return true;
1322
1323 tp = &tp_vec[tp_vec_nr - 1];
1324 if ((unsigned long)text_poke_addr(tp) > (unsigned long)addr)
1325 return true;
1326
1327 return false;
1328}
1329
1330static void text_poke_flush(void *addr)
1331{
1332 if (tp_vec_nr == TP_VEC_MAX || tp_order_fail(addr)) {
1333 text_poke_bp_batch(tp_vec, tp_vec_nr);
1334 tp_vec_nr = 0;
1335 }
1336}
1337
1338void text_poke_finish(void)
1339{
1340 text_poke_flush(NULL);
1341}
1342
1343void __ref text_poke_queue(void *addr, const void *opcode, size_t len, const void *emulate)
1344{
1345 struct text_poke_loc *tp;
1346
1347 if (unlikely(system_state == SYSTEM_BOOTING)) {
1348 text_poke_early(addr, opcode, len);
1349 return;
1350 }
1351
1352 text_poke_flush(addr);
1353
1354 tp = &tp_vec[tp_vec_nr++];
1355 text_poke_loc_init(tp, addr, opcode, len, emulate);
1356}
1357
1358/**
1359 * text_poke_bp() -- update instructions on live kernel on SMP
1360 * @addr: address to patch
1361 * @opcode: opcode of new instruction
1362 * @len: length to copy
1363 * @handler: address to jump to when the temporary breakpoint is hit
1364 *
1365 * Update a single instruction with the vector in the stack, avoiding
1366 * dynamically allocated memory. This function should be used when it is
1367 * not possible to allocate memory.
1368 */
1369void __ref text_poke_bp(void *addr, const void *opcode, size_t len, const void *emulate)
1370{
1371 struct text_poke_loc tp;
1372
1373 if (unlikely(system_state == SYSTEM_BOOTING)) {
1374 text_poke_early(addr, opcode, len);
1375 return;
1376 }
1377
1378 text_poke_loc_init(&tp, addr, opcode, len, emulate);
1379 text_poke_bp_batch(&tp, 1);
1380}