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2024-05-13 9d77db3c730780c8ef5ccd4b66403ff5675cfe4e 
 kernel/arch/x86/kernel/alternative.c
....@@ -1,26 +1,34 @@
1
+// SPDX-License-Identifier: GPL-2.0-only
12 #define pr_fmt(fmt) "SMP alternatives: " fmt
23 
34 #include <linux/module.h>
45 #include <linux/sched.h>
6
+#include <linux/perf_event.h>
57 #include <linux/mutex.h>
68 #include <linux/list.h>
79 #include <linux/stringify.h>
10
+#include <linux/highmem.h>
811 #include <linux/mm.h>
912 #include <linux/vmalloc.h>
1013 #include <linux/memory.h>
1114 #include <linux/stop_machine.h>
1215 #include <linux/slab.h>
1316 #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>
1421 #include <asm/text-patching.h>
1522 #include <asm/alternative.h>
1623 #include <asm/sections.h>
17
-#include <asm/pgtable.h>
1824 #include <asm/mce.h>
1925 #include <asm/nmi.h>
2026 #include <asm/cacheflush.h>
2127 #include <asm/tlbflush.h>
28
+#include <asm/insn.h>
2229 #include <asm/io.h>
2330 #include <asm/fixmap.h>
31
+#include <asm/asm-prototypes.h>
2432 
2533 int __read_mostly alternatives_patched;
2634 
....@@ -49,7 +57,7 @@
4957 #define DPRINTK(fmt, args...)						\
5058 do {									\
5159 	if (debug_alternative)						\
52
-		printk(KERN_DEBUG "%s: " fmt "\n", __func__, ##args);	\
60
+		printk(KERN_DEBUG pr_fmt(fmt) "\n", ##args);		\
5361 } while (0)
5462 
5563 #define DUMP_BYTES(buf, len, fmt, args...)				\
....@@ -60,7 +68,7 @@
6068 		if (!(len))						\
6169 			break;						\
6270 									\
63
-		printk(KERN_DEBUG fmt, ##args);				\
71
+		printk(KERN_DEBUG pr_fmt(fmt), ##args);			\
6472 		for (j = 0; j < (len) - 1; j++)				\
6573 			printk(KERN_CONT "%02hhx ", buf[j]);		\
6674 		printk(KERN_CONT "%02hhx\n", buf[j]);			\
....@@ -222,13 +230,17 @@
222230 		}
223231 		break;
224232 
233
+	case X86_VENDOR_HYGON:
234
+		ideal_nops = p6_nops;
235
+		return;
236
+
225237 	case X86_VENDOR_AMD:
226238 		if (boot_cpu_data.x86 > 0xf) {
227239 			ideal_nops = p6_nops;
228240 			return;
229241 		}
230242 
231
-		/* fall through */
243
+		fallthrough;
232244 
233245 	default:
234246 #ifdef CONFIG_X86_64
....@@ -257,9 +269,11 @@
257269 	}
258270 }
259271 
272
+extern s32 __retpoline_sites[], __retpoline_sites_end[];
273
+extern s32 __return_sites[], __return_sites_end[];
260274 extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
261275 extern s32 __smp_locks[], __smp_locks_end[];
262
-void *text_poke_early(void *addr, const void *opcode, size_t len);
276
+void text_poke_early(void *addr, const void *opcode, size_t len);
263277 
264278 /*
265279  * Are we looking at a near JMP with a 1 or 4-byte displacement.
....@@ -270,7 +284,7 @@
270284 }
271285 
272286 static void __init_or_module
273
-recompute_jump(struct alt_instr *a, u8 *orig_insn, u8 *repl_insn, u8 *insnbuf)
287
+recompute_jump(struct alt_instr *a, u8 *orig_insn, u8 *repl_insn, u8 *insn_buff)
274288 {
275289 	u8 *next_rip, *tgt_rip;
276290 	s32 n_dspl, o_dspl;
....@@ -279,7 +293,7 @@
279293 	if (a->replacementlen != 5)
280294 		return;
281295 
282
-	o_dspl = *(s32 *)(insnbuf + 1);
296
+	o_dspl = *(s32 *)(insn_buff + 1);
283297 
284298 	/* next_rip of the replacement JMP */
285299 	next_rip = repl_insn + a->replacementlen;
....@@ -305,9 +319,9 @@
305319 two_byte_jmp:
306320 	n_dspl -= 2;
307321 
308
-	insnbuf[0] = 0xeb;
309
-	insnbuf[1] = (s8)n_dspl;
310
-	add_nops(insnbuf + 2, 3);
322
+	insn_buff[0] = 0xeb;
323
+	insn_buff[1] = (s8)n_dspl;
324
+	add_nops(insn_buff + 2, 3);
311325 
312326 	repl_len = 2;
313327 	goto done;
....@@ -315,8 +329,8 @@
315329 five_byte_jmp:
316330 	n_dspl -= 5;
317331 
318
-	insnbuf[0] = 0xe9;
319
-	*(s32 *)&insnbuf[1] = n_dspl;
332
+	insn_buff[0] = 0xe9;
333
+	*(s32 *)&insn_buff[1] = n_dspl;
320334 
321335 	repl_len = 5;
322336 
....@@ -327,25 +341,69 @@
327341 }
328342 
329343 /*
344
+ * optimize_nops_range() - Optimize a sequence of single byte NOPs (0x90)
345
+ *
346
+ * @instr: instruction byte stream
347
+ * @instrlen: length of the above
348
+ * @off: offset within @instr where the first NOP has been detected
349
+ *
350
+ * Return: number of NOPs found (and replaced).
351
+ */
352
+static __always_inline int optimize_nops_range(u8 *instr, u8 instrlen, int off)
353
+{
354
+	unsigned long flags;
355
+	int i = off, nnops;
356
+
357
+	while (i < instrlen) {
358
+		if (instr[i] != 0x90)
359
+			break;
360
+
361
+		i++;
362
+	}
363
+
364
+	nnops = i - off;
365
+
366
+	if (nnops <= 1)
367
+		return nnops;
368
+
369
+	local_irq_save(flags);
370
+	add_nops(instr + off, nnops);
371
+	local_irq_restore(flags);
372
+
373
+	DUMP_BYTES(instr, instrlen, "%px: [%d:%d) optimized NOPs: ", instr, off, i);
374
+
375
+	return nnops;
376
+}
377
+
378
+/*
330379  * "noinline" to cause control flow change and thus invalidate I$ and
331380  * cause refetch after modification.
332381  */
333
-static void __init_or_module noinline optimize_nops(struct alt_instr *a, u8 *instr)
382
+static void __init_or_module noinline optimize_nops(u8 *instr, size_t len)
334383 {
335
-	unsigned long flags;
336
-	int i;
384
+	struct insn insn;
385
+	int i = 0;
337386 
338
-	for (i = 0; i < a->padlen; i++) {
339
-		if (instr[i] != 0x90)
387
+	/*
388
+	 * Jump over the non-NOP insns and optimize single-byte NOPs into bigger
389
+	 * ones.
390
+	 */
391
+	for (;;) {
392
+		if (insn_decode_kernel(&insn, &instr[i]))
393
+			return;
394
+
395
+		/*
396
+		 * See if this and any potentially following NOPs can be
397
+		 * optimized.
398
+		 */
399
+		if (insn.length == 1 && insn.opcode.bytes[0] == 0x90)
400
+			i += optimize_nops_range(instr, len, i);
401
+		else
402
+			i += insn.length;
403
+
404
+		if (i >= len)
340405 			return;
341406 	}
342
-
343
-	local_irq_save(flags);
344
-	add_nops(instr + (a->instrlen - a->padlen), a->padlen);
345
-	local_irq_restore(flags);
346
-
347
-	DUMP_BYTES(instr, a->instrlen, "%px: [%d:%d) optimized NOPs: ",
348
-		   instr, a->instrlen - a->padlen, a->padlen);
349407 }
350408 
351409 /*
....@@ -363,7 +421,7 @@
363421 {
364422 	struct alt_instr *a;
365423 	u8 *instr, *replacement;
366
-	u8 insnbuf[MAX_PATCH_LEN];
424
+	u8 insn_buff[MAX_PATCH_LEN];
367425 
368426 	DPRINTK("alt table %px, -> %px", start, end);
369427 	/*
....@@ -376,30 +434,36 @@
376434 	 * order.
377435 	 */
378436 	for (a = start; a < end; a++) {
379
-		int insnbuf_sz = 0;
437
+		int insn_buff_sz = 0;
438
+		/* Mask away "NOT" flag bit for feature to test. */
439
+		u16 feature = a->cpuid & ~ALTINSTR_FLAG_INV;
380440 
381441 		instr = (u8 *)&a->instr_offset + a->instr_offset;
382442 		replacement = (u8 *)&a->repl_offset + a->repl_offset;
383
-		BUG_ON(a->instrlen > sizeof(insnbuf));
384
-		BUG_ON(a->cpuid >= (NCAPINTS + NBUGINTS) * 32);
385
-		if (!boot_cpu_has(a->cpuid)) {
386
-			if (a->padlen > 1)
387
-				optimize_nops(a, instr);
443
+		BUG_ON(a->instrlen > sizeof(insn_buff));
444
+		BUG_ON(feature >= (NCAPINTS + NBUGINTS) * 32);
388445 
389
-			continue;
390
-		}
446
+		/*
447
+		 * Patch if either:
448
+		 * - feature is present
449
+		 * - feature not present but ALTINSTR_FLAG_INV is set to mean,
450
+		 *   patch if feature is *NOT* present.
451
+		 */
452
+		if (!boot_cpu_has(feature) == !(a->cpuid & ALTINSTR_FLAG_INV))
453
+			goto next;
391454 
392
-		DPRINTK("feat: %d*32+%d, old: (%px len: %d), repl: (%px, len: %d), pad: %d",
393
-			a->cpuid >> 5,
394
-			a->cpuid & 0x1f,
395
-			instr, a->instrlen,
396
-			replacement, a->replacementlen, a->padlen);
455
+		DPRINTK("feat: %s%d*32+%d, old: (%pS (%px) len: %d), repl: (%px, len: %d)",
456
+			(a->cpuid & ALTINSTR_FLAG_INV) ? "!" : "",
457
+			feature >> 5,
458
+			feature & 0x1f,
459
+			instr, instr, a->instrlen,
460
+			replacement, a->replacementlen);
397461 
398462 		DUMP_BYTES(instr, a->instrlen, "%px: old_insn: ", instr);
399463 		DUMP_BYTES(replacement, a->replacementlen, "%px: rpl_insn: ", replacement);
400464 
401
-		memcpy(insnbuf, replacement, a->replacementlen);
402
-		insnbuf_sz = a->replacementlen;
465
+		memcpy(insn_buff, replacement, a->replacementlen);
466
+		insn_buff_sz = a->replacementlen;
403467 
404468 		/*
405469 		 * 0xe8 is a relative jump; fix the offset.
....@@ -407,26 +471,271 @@
407471 		 * Instruction length is checked before the opcode to avoid
408472 		 * accessing uninitialized bytes for zero-length replacements.
409473 		 */
410
-		if (a->replacementlen == 5 && *insnbuf == 0xe8) {
411
-			*(s32 *)(insnbuf + 1) += replacement - instr;
474
+		if (a->replacementlen == 5 && *insn_buff == 0xe8) {
475
+			*(s32 *)(insn_buff + 1) += replacement - instr;
412476 			DPRINTK("Fix CALL offset: 0x%x, CALL 0x%lx",
413
-				*(s32 *)(insnbuf + 1),
414
-				(unsigned long)instr + *(s32 *)(insnbuf + 1) + 5);
477
+				*(s32 *)(insn_buff + 1),
478
+				(unsigned long)instr + *(s32 *)(insn_buff + 1) + 5);
415479 		}
416480 
417481 		if (a->replacementlen && is_jmp(replacement[0]))
418
-			recompute_jump(a, instr, replacement, insnbuf);
482
+			recompute_jump(a, instr, replacement, insn_buff);
419483 
420
-		if (a->instrlen > a->replacementlen) {
421
-			add_nops(insnbuf + a->replacementlen,
422
-				 a->instrlen - a->replacementlen);
423
-			insnbuf_sz += a->instrlen - a->replacementlen;
424
-		}
425
-		DUMP_BYTES(insnbuf, insnbuf_sz, "%px: final_insn: ", instr);
484
+		for (; insn_buff_sz < a->instrlen; insn_buff_sz++)
485
+			insn_buff[insn_buff_sz] = 0x90;
426486 
427
-		text_poke_early(instr, insnbuf, insnbuf_sz);
487
+		DUMP_BYTES(insn_buff, insn_buff_sz, "%px: final_insn: ", instr);
488
+
489
+		text_poke_early(instr, insn_buff, insn_buff_sz);
490
+
491
+next:
492
+		optimize_nops(instr, a->instrlen);
428493 	}
429494 }
495
+
496
+#if defined(CONFIG_RETPOLINE) && defined(CONFIG_STACK_VALIDATION)
497
+
498
+/*
499
+ * CALL/JMP *%\reg
500
+ */
501
+static int emit_indirect(int op, int reg, u8 *bytes)
502
+{
503
+	int i = 0;
504
+	u8 modrm;
505
+
506
+	switch (op) {
507
+	case CALL_INSN_OPCODE:
508
+		modrm = 0x10; /* Reg = 2; CALL r/m */
509
+		break;
510
+
511
+	case JMP32_INSN_OPCODE:
512
+		modrm = 0x20; /* Reg = 4; JMP r/m */
513
+		break;
514
+
515
+	default:
516
+		WARN_ON_ONCE(1);
517
+		return -1;
518
+	}
519
+
520
+	if (reg >= 8) {
521
+		bytes[i++] = 0x41; /* REX.B prefix */
522
+		reg -= 8;
523
+	}
524
+
525
+	modrm |= 0xc0; /* Mod = 3 */
526
+	modrm += reg;
527
+
528
+	bytes[i++] = 0xff; /* opcode */
529
+	bytes[i++] = modrm;
530
+
531
+	return i;
532
+}
533
+
534
+/*
535
+ * Rewrite the compiler generated retpoline thunk calls.
536
+ *
537
+ * For spectre_v2=off (!X86_FEATURE_RETPOLINE), rewrite them into immediate
538
+ * indirect instructions, avoiding the extra indirection.
539
+ *
540
+ * For example, convert:
541
+ *
542
+ *   CALL __x86_indirect_thunk_\reg
543
+ *
544
+ * into:
545
+ *
546
+ *   CALL *%\reg
547
+ *
548
+ * It also tries to inline spectre_v2=retpoline,amd when size permits.
549
+ */
550
+static int patch_retpoline(void *addr, struct insn *insn, u8 *bytes)
551
+{
552
+	retpoline_thunk_t *target;
553
+	int reg, ret, i = 0;
554
+	u8 op, cc;
555
+
556
+	target = addr + insn->length + insn->immediate.value;
557
+	reg = target - __x86_indirect_thunk_array;
558
+
559
+	if (WARN_ON_ONCE(reg & ~0xf))
560
+		return -1;
561
+
562
+	/* If anyone ever does: CALL/JMP *%rsp, we're in deep trouble. */
563
+	BUG_ON(reg == 4);
564
+
565
+	if (cpu_feature_enabled(X86_FEATURE_RETPOLINE) &&
566
+	    !cpu_feature_enabled(X86_FEATURE_RETPOLINE_LFENCE))
567
+		return -1;
568
+
569
+	op = insn->opcode.bytes[0];
570
+
571
+	/*
572
+	 * Convert:
573
+	 *
574
+	 *   Jcc.d32 __x86_indirect_thunk_\reg
575
+	 *
576
+	 * into:
577
+	 *
578
+	 *   Jncc.d8 1f
579
+	 *   [ LFENCE ]
580
+	 *   JMP *%\reg
581
+	 *   [ NOP ]
582
+	 * 1:
583
+	 */
584
+	/* Jcc.d32 second opcode byte is in the range: 0x80-0x8f */
585
+	if (op == 0x0f && (insn->opcode.bytes[1] & 0xf0) == 0x80) {
586
+		cc = insn->opcode.bytes[1] & 0xf;
587
+		cc ^= 1; /* invert condition */
588
+
589
+		bytes[i++] = 0x70 + cc;        /* Jcc.d8 */
590
+		bytes[i++] = insn->length - 2; /* sizeof(Jcc.d8) == 2 */
591
+
592
+		/* Continue as if: JMP.d32 __x86_indirect_thunk_\reg */
593
+		op = JMP32_INSN_OPCODE;
594
+	}
595
+
596
+	/*
597
+	 * For RETPOLINE_AMD: prepend the indirect CALL/JMP with an LFENCE.
598
+	 */
599
+	if (cpu_feature_enabled(X86_FEATURE_RETPOLINE_LFENCE)) {
600
+		bytes[i++] = 0x0f;
601
+		bytes[i++] = 0xae;
602
+		bytes[i++] = 0xe8; /* LFENCE */
603
+	}
604
+
605
+	ret = emit_indirect(op, reg, bytes + i);
606
+	if (ret < 0)
607
+		return ret;
608
+	i += ret;
609
+
610
+	for (; i < insn->length;)
611
+		bytes[i++] = 0x90;
612
+
613
+	return i;
614
+}
615
+
616
+/*
617
+ * Generated by 'objtool --retpoline'.
618
+ */
619
+void __init_or_module noinline apply_retpolines(s32 *start, s32 *end)
620
+{
621
+	s32 *s;
622
+
623
+	for (s = start; s < end; s++) {
624
+		void *addr = (void *)s + *s;
625
+		struct insn insn;
626
+		int len, ret;
627
+		u8 bytes[16];
628
+		u8 op1, op2;
629
+
630
+		ret = insn_decode_kernel(&insn, addr);
631
+		if (WARN_ON_ONCE(ret < 0))
632
+			continue;
633
+
634
+		op1 = insn.opcode.bytes[0];
635
+		op2 = insn.opcode.bytes[1];
636
+
637
+		switch (op1) {
638
+		case CALL_INSN_OPCODE:
639
+		case JMP32_INSN_OPCODE:
640
+			break;
641
+
642
+		case 0x0f: /* escape */
643
+			if (op2 >= 0x80 && op2 <= 0x8f)
644
+				break;
645
+			fallthrough;
646
+		default:
647
+			WARN_ON_ONCE(1);
648
+			continue;
649
+		}
650
+
651
+		DPRINTK("retpoline at: %pS (%px) len: %d to: %pS",
652
+			addr, addr, insn.length,
653
+			addr + insn.length + insn.immediate.value);
654
+
655
+		len = patch_retpoline(addr, &insn, bytes);
656
+		if (len == insn.length) {
657
+			optimize_nops(bytes, len);
658
+			DUMP_BYTES(((u8*)addr),  len, "%px: orig: ", addr);
659
+			DUMP_BYTES(((u8*)bytes), len, "%px: repl: ", addr);
660
+			text_poke_early(addr, bytes, len);
661
+		}
662
+	}
663
+}
664
+
665
+#ifdef CONFIG_RETHUNK
666
+/*
667
+ * Rewrite the compiler generated return thunk tail-calls.
668
+ *
669
+ * For example, convert:
670
+ *
671
+ *   JMP __x86_return_thunk
672
+ *
673
+ * into:
674
+ *
675
+ *   RET
676
+ */
677
+static int patch_return(void *addr, struct insn *insn, u8 *bytes)
678
+{
679
+	int i = 0;
680
+
681
+	if (cpu_feature_enabled(X86_FEATURE_RETHUNK))
682
+		return -1;
683
+
684
+	bytes[i++] = RET_INSN_OPCODE;
685
+
686
+	for (; i < insn->length;)
687
+		bytes[i++] = INT3_INSN_OPCODE;
688
+
689
+	return i;
690
+}
691
+
692
+void __init_or_module noinline apply_returns(s32 *start, s32 *end)
693
+{
694
+	s32 *s;
695
+
696
+	for (s = start; s < end; s++) {
697
+		void *dest = NULL, *addr = (void *)s + *s;
698
+		struct insn insn;
699
+		int len, ret;
700
+		u8 bytes[16];
701
+		u8 op;
702
+
703
+		ret = insn_decode_kernel(&insn, addr);
704
+		if (WARN_ON_ONCE(ret < 0))
705
+			continue;
706
+
707
+		op = insn.opcode.bytes[0];
708
+		if (op == JMP32_INSN_OPCODE)
709
+			dest = addr + insn.length + insn.immediate.value;
710
+
711
+		if (__static_call_fixup(addr, op, dest) ||
712
+		    WARN_ONCE(dest != &__x86_return_thunk,
713
+			      "missing return thunk: %pS-%pS: %*ph",
714
+			      addr, dest, 5, addr))
715
+			continue;
716
+
717
+		DPRINTK("return thunk at: %pS (%px) len: %d to: %pS",
718
+			addr, addr, insn.length,
719
+			addr + insn.length + insn.immediate.value);
720
+
721
+		len = patch_return(addr, &insn, bytes);
722
+		if (len == insn.length) {
723
+			DUMP_BYTES(((u8*)addr),  len, "%px: orig: ", addr);
724
+			DUMP_BYTES(((u8*)bytes), len, "%px: repl: ", addr);
725
+			text_poke_early(addr, bytes, len);
726
+		}
727
+	}
728
+}
729
+#else
730
+void __init_or_module noinline apply_returns(s32 *start, s32 *end) { }
731
+#endif /* CONFIG_RETHUNK */
732
+
733
+#else /* !RETPOLINES || !CONFIG_STACK_VALIDATION */
734
+
735
+void __init_or_module noinline apply_retpolines(s32 *start, s32 *end) { }
736
+void __init_or_module noinline apply_returns(s32 *start, s32 *end) { }
737
+
738
+#endif /* CONFIG_RETPOLINE && CONFIG_STACK_VALIDATION */
430739 
431740 #ifdef CONFIG_SMP
432741 static void alternatives_smp_lock(const s32 *start, const s32 *end,
....@@ -586,45 +895,125 @@
586895 				     struct paravirt_patch_site *end)
587896 {
588897 	struct paravirt_patch_site *p;
589
-	char insnbuf[MAX_PATCH_LEN];
898
+	char insn_buff[MAX_PATCH_LEN];
590899 
591900 	for (p = start; p < end; p++) {
592901 		unsigned int used;
593902 
594903 		BUG_ON(p->len > MAX_PATCH_LEN);
595904 		/* prep the buffer with the original instructions */
596
-		memcpy(insnbuf, p->instr, p->len);
597
-		used = pv_init_ops.patch(p->instrtype, p->clobbers, insnbuf,
598
-					 (unsigned long)p->instr, p->len);
905
+		memcpy(insn_buff, p->instr, p->len);
906
+		used = pv_ops.init.patch(p->type, insn_buff, (unsigned long)p->instr, p->len);
599907 
600908 		BUG_ON(used > p->len);
601909 
602910 		/* Pad the rest with nops */
603
-		add_nops(insnbuf + used, p->len - used);
604
-		text_poke_early(p->instr, insnbuf, p->len);
911
+		add_nops(insn_buff + used, p->len - used);
912
+		text_poke_early(p->instr, insn_buff, p->len);
605913 	}
606914 }
607915 extern struct paravirt_patch_site __start_parainstructions[],
608916 	__stop_parainstructions[];
609917 #endif	/* CONFIG_PARAVIRT */
610918 
919
+/*
920
+ * Self-test for the INT3 based CALL emulation code.
921
+ *
922
+ * This exercises int3_emulate_call() to make sure INT3 pt_regs are set up
923
+ * properly and that there is a stack gap between the INT3 frame and the
924
+ * previous context. Without this gap doing a virtual PUSH on the interrupted
925
+ * stack would corrupt the INT3 IRET frame.
926
+ *
927
+ * See entry_{32,64}.S for more details.
928
+ */
929
+static void __init __no_sanitize_address notrace int3_magic(unsigned int *ptr)
930
+{
931
+	*ptr = 1;
932
+}
933
+
934
+extern __initdata unsigned long int3_selftest_ip; /* defined in asm below */
935
+
936
+static int __init
937
+int3_exception_notify(struct notifier_block *self, unsigned long val, void *data)
938
+{
939
+	struct die_args *args = data;
940
+	struct pt_regs *regs = args->regs;
941
+
942
+	if (!regs || user_mode(regs))
943
+		return NOTIFY_DONE;
944
+
945
+	if (val != DIE_INT3)
946
+		return NOTIFY_DONE;
947
+
948
+	if (regs->ip - INT3_INSN_SIZE != int3_selftest_ip)
949
+		return NOTIFY_DONE;
950
+
951
+	int3_emulate_call(regs, (unsigned long)&int3_magic);
952
+	return NOTIFY_STOP;
953
+}
954
+
955
+static void __init int3_selftest(void)
956
+{
957
+	static __initdata struct notifier_block int3_exception_nb = {
958
+		.notifier_call	= int3_exception_notify,
959
+		.priority	= INT_MAX-1, /* last */
960
+	};
961
+	unsigned int val = 0;
962
+
963
+	BUG_ON(register_die_notifier(&int3_exception_nb));
964
+
965
+	/*
966
+	 * Basically: int3_magic(&val); but really complicated :-)
967
+	 *
968
+	 * Stick the address of the INT3 instruction into int3_selftest_ip,
969
+	 * then trigger the INT3, padded with NOPs to match a CALL instruction
970
+	 * length.
971
+	 */
972
+	asm volatile ("1: int3; nop; nop; nop; nop\n\t"
973
+		      ".pushsection .init.data,\"aw\"\n\t"
974
+		      ".align " __ASM_SEL(4, 8) "\n\t"
975
+		      ".type int3_selftest_ip, @object\n\t"
976
+		      ".size int3_selftest_ip, " __ASM_SEL(4, 8) "\n\t"
977
+		      "int3_selftest_ip:\n\t"
978
+		      __ASM_SEL(.long, .quad) " 1b\n\t"
979
+		      ".popsection\n\t"
980
+		      : ASM_CALL_CONSTRAINT
981
+		      : __ASM_SEL_RAW(a, D) (&val)
982
+		      : "memory");
983
+
984
+	BUG_ON(val != 1);
985
+
986
+	unregister_die_notifier(&int3_exception_nb);
987
+}
988
+
611989 void __init alternative_instructions(void)
612990 {
613
-	/* The patching is not fully atomic, so try to avoid local interruptions
614
-	   that might execute the to be patched code.
615
-	   Other CPUs are not running. */
991
+	int3_selftest();
992
+
993
+	/*
994
+	 * The patching is not fully atomic, so try to avoid local
995
+	 * interruptions that might execute the to be patched code.
996
+	 * Other CPUs are not running.
997
+	 */
616998 	stop_nmi();
617999 
6181000 	/*
6191001 	 * Don't stop machine check exceptions while patching.
6201002 	 * MCEs only happen when something got corrupted and in this
6211003 	 * case we must do something about the corruption.
622
-	 * Ignoring it is worse than a unlikely patching race.
1004
+	 * Ignoring it is worse than an unlikely patching race.
6231005 	 * Also machine checks tend to be broadcast and if one CPU
6241006 	 * goes into machine check the others follow quickly, so we don't
6251007 	 * expect a machine check to cause undue problems during to code
6261008 	 * patching.
6271009 	 */
1010
+
1011
+	/*
1012
+	 * Rewrite the retpolines, must be done before alternatives since
1013
+	 * those can rewrite the retpoline thunks.
1014
+	 */
1015
+	apply_retpolines(__retpoline_sites, __retpoline_sites_end);
1016
+	apply_returns(__return_sites, __return_sites_end);
6281017 
6291018 	apply_alternatives(__alt_instructions, __alt_instructions_end);
6301019 
....@@ -637,10 +1026,11 @@
6371026 					    _text, _etext);
6381027 	}
6391028 
640
-	if (!uniproc_patched || num_possible_cpus() == 1)
1029
+	if (!uniproc_patched || num_possible_cpus() == 1) {
6411030 		free_init_pages("SMP alternatives",
6421031 				(unsigned long)__smp_locks,
6431032 				(unsigned long)__smp_locks_end);
1033
+	}
6441034 #endif
6451035 
6461036 	apply_paravirt(__parainstructions, __parainstructions_end);
....@@ -658,11 +1048,11 @@
6581048  * When you use this code to patch more than one byte of an instruction
6591049  * you need to make sure that other CPUs cannot execute this code in parallel.
6601050  * Also no thread must be currently preempted in the middle of these
661
- * instructions. And on the local CPU you need to be protected again NMI or MCE
662
- * handlers seeing an inconsistent instruction while you patch.
1051
+ * instructions. And on the local CPU you need to be protected against NMI or
1052
+ * MCE handlers seeing an inconsistent instruction while you patch.
6631053  */
664
-void *__init_or_module text_poke_early(void *addr, const void *opcode,
665
-				       size_t len)
1054
+void __init_or_module text_poke_early(void *addr, const void *opcode,
1055
+				      size_t len)
6661056 {
6671057 	unsigned long flags;
6681058 
....@@ -685,6 +1075,176 @@
6851075 		 * that causes hangs on some VIA CPUs.
6861076 		 */
6871077 	}
1078
+}
1079
+
1080
+typedef struct {
1081
+	struct mm_struct *mm;
1082
+} temp_mm_state_t;
1083
+
1084
+/*
1085
+ * Using a temporary mm allows to set temporary mappings that are not accessible
1086
+ * by other CPUs. Such mappings are needed to perform sensitive memory writes
1087
+ * that override the kernel memory protections (e.g., W^X), without exposing the
1088
+ * temporary page-table mappings that are required for these write operations to
1089
+ * other CPUs. Using a temporary mm also allows to avoid TLB shootdowns when the
1090
+ * mapping is torn down.
1091
+ *
1092
+ * Context: The temporary mm needs to be used exclusively by a single core. To
1093
+ *          harden security IRQs must be disabled while the temporary mm is
1094
+ *          loaded, thereby preventing interrupt handler bugs from overriding
1095
+ *          the kernel memory protection.
1096
+ */
1097
+static inline temp_mm_state_t use_temporary_mm(struct mm_struct *mm)
1098
+{
1099
+	temp_mm_state_t temp_state;
1100
+
1101
+	lockdep_assert_irqs_disabled();
1102
+
1103
+	/*
1104
+	 * Make sure not to be in TLB lazy mode, as otherwise we'll end up
1105
+	 * with a stale address space WITHOUT being in lazy mode after
1106
+	 * restoring the previous mm.
1107
+	 */
1108
+	if (this_cpu_read(cpu_tlbstate.is_lazy))
1109
+		leave_mm(smp_processor_id());
1110
+
1111
+	temp_state.mm = this_cpu_read(cpu_tlbstate.loaded_mm);
1112
+	switch_mm_irqs_off(NULL, mm, current);
1113
+
1114
+	/*
1115
+	 * If breakpoints are enabled, disable them while the temporary mm is
1116
+	 * used. Userspace might set up watchpoints on addresses that are used
1117
+	 * in the temporary mm, which would lead to wrong signals being sent or
1118
+	 * crashes.
1119
+	 *
1120
+	 * Note that breakpoints are not disabled selectively, which also causes
1121
+	 * kernel breakpoints (e.g., perf's) to be disabled. This might be
1122
+	 * undesirable, but still seems reasonable as the code that runs in the
1123
+	 * temporary mm should be short.
1124
+	 */
1125
+	if (hw_breakpoint_active())
1126
+		hw_breakpoint_disable();
1127
+
1128
+	return temp_state;
1129
+}
1130
+
1131
+static inline void unuse_temporary_mm(temp_mm_state_t prev_state)
1132
+{
1133
+	lockdep_assert_irqs_disabled();
1134
+	switch_mm_irqs_off(NULL, prev_state.mm, current);
1135
+
1136
+	/*
1137
+	 * Restore the breakpoints if they were disabled before the temporary mm
1138
+	 * was loaded.
1139
+	 */
1140
+	if (hw_breakpoint_active())
1141
+		hw_breakpoint_restore();
1142
+}
1143
+
1144
+__ro_after_init struct mm_struct *poking_mm;
1145
+__ro_after_init unsigned long poking_addr;
1146
+
1147
+static void *__text_poke(void *addr, const void *opcode, size_t len)
1148
+{
1149
+	bool cross_page_boundary = offset_in_page(addr) + len > PAGE_SIZE;
1150
+	struct page *pages[2] = {NULL};
1151
+	temp_mm_state_t prev;
1152
+	unsigned long flags;
1153
+	pte_t pte, *ptep;
1154
+	spinlock_t *ptl;
1155
+	pgprot_t pgprot;
1156
+
1157
+	/*
1158
+	 * While boot memory allocator is running we cannot use struct pages as
1159
+	 * they are not yet initialized. There is no way to recover.
1160
+	 */
1161
+	BUG_ON(!after_bootmem);
1162
+
1163
+	if (!core_kernel_text((unsigned long)addr)) {
1164
+		pages[0] = vmalloc_to_page(addr);
1165
+		if (cross_page_boundary)
1166
+			pages[1] = vmalloc_to_page(addr + PAGE_SIZE);
1167
+	} else {
1168
+		pages[0] = virt_to_page(addr);
1169
+		WARN_ON(!PageReserved(pages[0]));
1170
+		if (cross_page_boundary)
1171
+			pages[1] = virt_to_page(addr + PAGE_SIZE);
1172
+	}
1173
+	/*
1174
+	 * If something went wrong, crash and burn since recovery paths are not
1175
+	 * implemented.
1176
+	 */
1177
+	BUG_ON(!pages[0] || (cross_page_boundary && !pages[1]));
1178
+
1179
+	/*
1180
+	 * Map the page without the global bit, as TLB flushing is done with
1181
+	 * flush_tlb_mm_range(), which is intended for non-global PTEs.
1182
+	 */
1183
+	pgprot = __pgprot(pgprot_val(PAGE_KERNEL) & ~_PAGE_GLOBAL);
1184
+
1185
+	/*
1186
+	 * The lock is not really needed, but this allows to avoid open-coding.
1187
+	 */
1188
+	ptep = get_locked_pte(poking_mm, poking_addr, &ptl);
1189
+
1190
+	/*
1191
+	 * This must not fail; preallocated in poking_init().
1192
+	 */
1193
+	VM_BUG_ON(!ptep);
1194
+
1195
+	local_irq_save(flags);
1196
+
1197
+	pte = mk_pte(pages[0], pgprot);
1198
+	set_pte_at(poking_mm, poking_addr, ptep, pte);
1199
+
1200
+	if (cross_page_boundary) {
1201
+		pte = mk_pte(pages[1], pgprot);
1202
+		set_pte_at(poking_mm, poking_addr + PAGE_SIZE, ptep + 1, pte);
1203
+	}
1204
+
1205
+	/*
1206
+	 * Loading the temporary mm behaves as a compiler barrier, which
1207
+	 * guarantees that the PTE will be set at the time memcpy() is done.
1208
+	 */
1209
+	prev = use_temporary_mm(poking_mm);
1210
+
1211
+	kasan_disable_current();
1212
+	memcpy((u8 *)poking_addr + offset_in_page(addr), opcode, len);
1213
+	kasan_enable_current();
1214
+
1215
+	/*
1216
+	 * Ensure that the PTE is only cleared after the instructions of memcpy
1217
+	 * were issued by using a compiler barrier.
1218
+	 */
1219
+	barrier();
1220
+
1221
+	pte_clear(poking_mm, poking_addr, ptep);
1222
+	if (cross_page_boundary)
1223
+		pte_clear(poking_mm, poking_addr + PAGE_SIZE, ptep + 1);
1224
+
1225
+	/*
1226
+	 * Loading the previous page-table hierarchy requires a serializing
1227
+	 * instruction that already allows the core to see the updated version.
1228
+	 * Xen-PV is assumed to serialize execution in a similar manner.
1229
+	 */
1230
+	unuse_temporary_mm(prev);
1231
+
1232
+	/*
1233
+	 * Flushing the TLB might involve IPIs, which would require enabled
1234
+	 * IRQs, but not if the mm is not used, as it is in this point.
1235
+	 */
1236
+	flush_tlb_mm_range(poking_mm, poking_addr, poking_addr +
1237
+			   (cross_page_boundary ? 2 : 1) * PAGE_SIZE,
1238
+			   PAGE_SHIFT, false);
1239
+
1240
+	/*
1241
+	 * If the text does not match what we just wrote then something is
1242
+	 * fundamentally screwy; there's nothing we can really do about that.
1243
+	 */
1244
+	BUG_ON(memcmp(addr, opcode, len));
1245
+
1246
+	local_irq_restore(flags);
1247
+	pte_unmap_unlock(ptep, ptl);
6881248 	return addr;
6891249 }
6901250 
....@@ -698,48 +1258,36 @@
6981258  * It means the size must be writable atomically and the address must be aligned
6991259  * in a way that permits an atomic write. It also makes sure we fit on a single
7001260  * page.
1261
+ *
1262
+ * Note that the caller must ensure that if the modified code is part of a
1263
+ * module, the module would not be removed during poking. This can be achieved
1264
+ * by registering a module notifier, and ordering module removal and patching
1265
+ * trough a mutex.
7011266  */
7021267 void *text_poke(void *addr, const void *opcode, size_t len)
7031268 {
704
-	unsigned long flags;
705
-	char *vaddr;
706
-	struct page *pages[2];
707
-	int i;
708
-
709
-	/*
710
-	 * While boot memory allocator is runnig we cannot use struct
711
-	 * pages as they are not yet initialized.
712
-	 */
713
-	BUG_ON(!after_bootmem);
714
-
7151269 	lockdep_assert_held(&text_mutex);
7161270 
717
-	if (!core_kernel_text((unsigned long)addr)) {
718
-		pages[0] = vmalloc_to_page(addr);
719
-		pages[1] = vmalloc_to_page(addr + PAGE_SIZE);
720
-	} else {
721
-		pages[0] = virt_to_page(addr);
722
-		WARN_ON(!PageReserved(pages[0]));
723
-		pages[1] = virt_to_page(addr + PAGE_SIZE);
724
-	}
725
-	BUG_ON(!pages[0]);
726
-	local_irq_save(flags);
727
-	set_fixmap(FIX_TEXT_POKE0, page_to_phys(pages[0]));
728
-	if (pages[1])
729
-		set_fixmap(FIX_TEXT_POKE1, page_to_phys(pages[1]));
730
-	vaddr = (char *)fix_to_virt(FIX_TEXT_POKE0);
731
-	memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len);
732
-	clear_fixmap(FIX_TEXT_POKE0);
733
-	if (pages[1])
734
-		clear_fixmap(FIX_TEXT_POKE1);
735
-	local_flush_tlb();
736
-	sync_core();
737
-	/* Could also do a CLFLUSH here to speed up CPU recovery; but
738
-	   that causes hangs on some VIA CPUs. */
739
-	for (i = 0; i < len; i++)
740
-		BUG_ON(((char *)addr)[i] != ((char *)opcode)[i]);
741
-	local_irq_restore(flags);
742
-	return addr;
1271
+	return __text_poke(addr, opcode, len);
1272
+}
1273
+
1274
+/**
1275
+ * text_poke_kgdb - Update instructions on a live kernel by kgdb
1276
+ * @addr: address to modify
1277
+ * @opcode: source of the copy
1278
+ * @len: length to copy
1279
+ *
1280
+ * Only atomic text poke/set should be allowed when not doing early patching.
1281
+ * It means the size must be writable atomically and the address must be aligned
1282
+ * in a way that permits an atomic write. It also makes sure we fit on a single
1283
+ * page.
1284
+ *
1285
+ * Context: should only be used by kgdb, which ensures no other core is running,
1286
+ *	    despite the fact it does not hold the text_mutex.
1287
+ */
1288
+void *text_poke_kgdb(void *addr, const void *opcode, size_t len)
1289
+{
1290
+	return __text_poke(addr, opcode, len);
7431291 }
7441292 
7451293 static void do_sync_core(void *info)
....@@ -747,34 +1295,390 @@
7471295 	sync_core();
7481296 }
7491297 
750
-static bool bp_patching_in_progress;
751
-static void *bp_int3_handler, *bp_int3_addr;
752
-
753
-int poke_int3_handler(struct pt_regs *regs)
1298
+void text_poke_sync(void)
7541299 {
1300
+	on_each_cpu(do_sync_core, NULL, 1);
1301
+}
1302
+
1303
+struct text_poke_loc {
1304
+	/* addr := _stext + rel_addr */
1305
+	s32 rel_addr;
1306
+	s32 disp;
1307
+	u8 len;
1308
+	u8 opcode;
1309
+	const u8 text[POKE_MAX_OPCODE_SIZE];
1310
+	/* see text_poke_bp_batch() */
1311
+	u8 old;
1312
+};
1313
+
1314
+struct bp_patching_desc {
1315
+	struct text_poke_loc *vec;
1316
+	int nr_entries;
1317
+	atomic_t refs;
1318
+};
1319
+
1320
+static struct bp_patching_desc bp_desc;
1321
+
1322
+static __always_inline
1323
+struct bp_patching_desc *try_get_desc(void)
1324
+{
1325
+	struct bp_patching_desc *desc = &bp_desc;
1326
+
1327
+	if (!arch_atomic_inc_not_zero(&desc->refs))
1328
+		return NULL;
1329
+
1330
+	return desc;
1331
+}
1332
+
1333
+static __always_inline void put_desc(void)
1334
+{
1335
+	struct bp_patching_desc *desc = &bp_desc;
1336
+
1337
+	smp_mb__before_atomic();
1338
+	arch_atomic_dec(&desc->refs);
1339
+}
1340
+
1341
+static __always_inline void *text_poke_addr(struct text_poke_loc *tp)
1342
+{
1343
+	return _stext + tp->rel_addr;
1344
+}
1345
+
1346
+static __always_inline int patch_cmp(const void *key, const void *elt)
1347
+{
1348
+	struct text_poke_loc *tp = (struct text_poke_loc *) elt;
1349
+
1350
+	if (key < text_poke_addr(tp))
1351
+		return -1;
1352
+	if (key > text_poke_addr(tp))
1353
+		return 1;
1354
+	return 0;
1355
+}
1356
+
1357
+noinstr int poke_int3_handler(struct pt_regs *regs)
1358
+{
1359
+	struct bp_patching_desc *desc;
1360
+	struct text_poke_loc *tp;
1361
+	int ret = 0;
1362
+	void *ip;
1363
+
1364
+	if (user_mode(regs))
1365
+		return 0;
1366
+
7551367 	/*
7561368 	 * Having observed our INT3 instruction, we now must observe
757
-	 * bp_patching_in_progress.
1369
+	 * bp_desc with non-zero refcount:
7581370 	 *
759
-	 * 	in_progress = TRUE		INT3
760
-	 * 	WMB				RMB
761
-	 * 	write INT3			if (in_progress)
762
-	 *
763
-	 * Idem for bp_int3_handler.
1371
+	 *	bp_desc.refs = 1		INT3
1372
+	 *	WMB				RMB
1373
+	 *	write INT3			if (bp_desc.refs != 0)
7641374 	 */
7651375 	smp_rmb();
7661376 
767
-	if (likely(!bp_patching_in_progress))
1377
+	desc = try_get_desc();
1378
+	if (!desc)
7681379 		return 0;
7691380 
770
-	if (user_mode(regs) || regs->ip != (unsigned long)bp_int3_addr)
771
-		return 0;
1381
+	/*
1382
+	 * Discount the INT3. See text_poke_bp_batch().
1383
+	 */
1384
+	ip = (void *) regs->ip - INT3_INSN_SIZE;
7721385 
773
-	/* set up the specified breakpoint handler */
774
-	regs->ip = (unsigned long) bp_int3_handler;
1386
+	/*
1387
+	 * Skip the binary search if there is a single member in the vector.
1388
+	 */
1389
+	if (unlikely(desc->nr_entries > 1)) {
1390
+		tp = __inline_bsearch(ip, desc->vec, desc->nr_entries,
1391
+				      sizeof(struct text_poke_loc),
1392
+				      patch_cmp);
1393
+		if (!tp)
1394
+			goto out_put;
1395
+	} else {
1396
+		tp = desc->vec;
1397
+		if (text_poke_addr(tp) != ip)
1398
+			goto out_put;
1399
+	}
7751400 
776
-	return 1;
1401
+	ip += tp->len;
7771402 
1403
+	switch (tp->opcode) {
1404
+	case INT3_INSN_OPCODE:
1405
+		/*
1406
+		 * Someone poked an explicit INT3, they'll want to handle it,
1407
+		 * do not consume.
1408
+		 */
1409
+		goto out_put;
1410
+
1411
+	case RET_INSN_OPCODE:
1412
+		int3_emulate_ret(regs);
1413
+		break;
1414
+
1415
+	case CALL_INSN_OPCODE:
1416
+		int3_emulate_call(regs, (long)ip + tp->disp);
1417
+		break;
1418
+
1419
+	case JMP32_INSN_OPCODE:
1420
+	case JMP8_INSN_OPCODE:
1421
+		int3_emulate_jmp(regs, (long)ip + tp->disp);
1422
+		break;
1423
+
1424
+	default:
1425
+		BUG();
1426
+	}
1427
+
1428
+	ret = 1;
1429
+
1430
+out_put:
1431
+	put_desc();
1432
+	return ret;
1433
+}
1434
+
1435
+#define TP_VEC_MAX (PAGE_SIZE / sizeof(struct text_poke_loc))
1436
+static struct text_poke_loc tp_vec[TP_VEC_MAX];
1437
+static int tp_vec_nr;
1438
+
1439
+/**
1440
+ * text_poke_bp_batch() -- update instructions on live kernel on SMP
1441
+ * @tp:			vector of instructions to patch
1442
+ * @nr_entries:		number of entries in the vector
1443
+ *
1444
+ * Modify multi-byte instruction by using int3 breakpoint on SMP.
1445
+ * We completely avoid stop_machine() here, and achieve the
1446
+ * synchronization using int3 breakpoint.
1447
+ *
1448
+ * The way it is done:
1449
+ *	- For each entry in the vector:
1450
+ *		- add a int3 trap to the address that will be patched
1451
+ *	- sync cores
1452
+ *	- For each entry in the vector:
1453
+ *		- update all but the first byte of the patched range
1454
+ *	- sync cores
1455
+ *	- For each entry in the vector:
1456
+ *		- replace the first byte (int3) by the first byte of
1457
+ *		  replacing opcode
1458
+ *	- sync cores
1459
+ */
1460
+static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries)
1461
+{
1462
+	unsigned char int3 = INT3_INSN_OPCODE;
1463
+	unsigned int i;
1464
+	int do_sync;
1465
+
1466
+	lockdep_assert_held(&text_mutex);
1467
+
1468
+	bp_desc.vec = tp;
1469
+	bp_desc.nr_entries = nr_entries;
1470
+
1471
+	/*
1472
+	 * Corresponds to the implicit memory barrier in try_get_desc() to
1473
+	 * ensure reading a non-zero refcount provides up to date bp_desc data.
1474
+	 */
1475
+	atomic_set_release(&bp_desc.refs, 1);
1476
+
1477
+	/*
1478
+	 * Corresponding read barrier in int3 notifier for making sure the
1479
+	 * nr_entries and handler are correctly ordered wrt. patching.
1480
+	 */
1481
+	smp_wmb();
1482
+
1483
+	/*
1484
+	 * First step: add a int3 trap to the address that will be patched.
1485
+	 */
1486
+	for (i = 0; i < nr_entries; i++) {
1487
+		tp[i].old = *(u8 *)text_poke_addr(&tp[i]);
1488
+		text_poke(text_poke_addr(&tp[i]), &int3, INT3_INSN_SIZE);
1489
+	}
1490
+
1491
+	text_poke_sync();
1492
+
1493
+	/*
1494
+	 * Second step: update all but the first byte of the patched range.
1495
+	 */
1496
+	for (do_sync = 0, i = 0; i < nr_entries; i++) {
1497
+		u8 old[POKE_MAX_OPCODE_SIZE] = { tp[i].old, };
1498
+		int len = tp[i].len;
1499
+
1500
+		if (len - INT3_INSN_SIZE > 0) {
1501
+			memcpy(old + INT3_INSN_SIZE,
1502
+			       text_poke_addr(&tp[i]) + INT3_INSN_SIZE,
1503
+			       len - INT3_INSN_SIZE);
1504
+			text_poke(text_poke_addr(&tp[i]) + INT3_INSN_SIZE,
1505
+				  (const char *)tp[i].text + INT3_INSN_SIZE,
1506
+				  len - INT3_INSN_SIZE);
1507
+			do_sync++;
1508
+		}
1509
+
1510
+		/*
1511
+		 * Emit a perf event to record the text poke, primarily to
1512
+		 * support Intel PT decoding which must walk the executable code
1513
+		 * to reconstruct the trace. The flow up to here is:
1514
+		 *   - write INT3 byte
1515
+		 *   - IPI-SYNC
1516
+		 *   - write instruction tail
1517
+		 * At this point the actual control flow will be through the
1518
+		 * INT3 and handler and not hit the old or new instruction.
1519
+		 * Intel PT outputs FUP/TIP packets for the INT3, so the flow
1520
+		 * can still be decoded. Subsequently:
1521
+		 *   - emit RECORD_TEXT_POKE with the new instruction
1522
+		 *   - IPI-SYNC
1523
+		 *   - write first byte
1524
+		 *   - IPI-SYNC
1525
+		 * So before the text poke event timestamp, the decoder will see
1526
+		 * either the old instruction flow or FUP/TIP of INT3. After the
1527
+		 * text poke event timestamp, the decoder will see either the
1528
+		 * new instruction flow or FUP/TIP of INT3. Thus decoders can
1529
+		 * use the timestamp as the point at which to modify the
1530
+		 * executable code.
1531
+		 * The old instruction is recorded so that the event can be
1532
+		 * processed forwards or backwards.
1533
+		 */
1534
+		perf_event_text_poke(text_poke_addr(&tp[i]), old, len,
1535
+				     tp[i].text, len);
1536
+	}
1537
+
1538
+	if (do_sync) {
1539
+		/*
1540
+		 * According to Intel, this core syncing is very likely
1541
+		 * not necessary and we'd be safe even without it. But
1542
+		 * better safe than sorry (plus there's not only Intel).
1543
+		 */
1544
+		text_poke_sync();
1545
+	}
1546
+
1547
+	/*
1548
+	 * Third step: replace the first byte (int3) by the first byte of
1549
+	 * replacing opcode.
1550
+	 */
1551
+	for (do_sync = 0, i = 0; i < nr_entries; i++) {
1552
+		if (tp[i].text[0] == INT3_INSN_OPCODE)
1553
+			continue;
1554
+
1555
+		text_poke(text_poke_addr(&tp[i]), tp[i].text, INT3_INSN_SIZE);
1556
+		do_sync++;
1557
+	}
1558
+
1559
+	if (do_sync)
1560
+		text_poke_sync();
1561
+
1562
+	/*
1563
+	 * Remove and wait for refs to be zero.
1564
+	 */
1565
+	if (!atomic_dec_and_test(&bp_desc.refs))
1566
+		atomic_cond_read_acquire(&bp_desc.refs, !VAL);
1567
+}
1568
+
1569
+static void text_poke_loc_init(struct text_poke_loc *tp, void *addr,
1570
+			       const void *opcode, size_t len, const void *emulate)
1571
+{
1572
+	struct insn insn;
1573
+	int ret, i;
1574
+
1575
+	memcpy((void *)tp->text, opcode, len);
1576
+	if (!emulate)
1577
+		emulate = opcode;
1578
+
1579
+	ret = insn_decode_kernel(&insn, emulate);
1580
+	BUG_ON(ret < 0);
1581
+
1582
+	tp->rel_addr = addr - (void *)_stext;
1583
+	tp->len = len;
1584
+	tp->opcode = insn.opcode.bytes[0];
1585
+
1586
+	switch (tp->opcode) {
1587
+	case RET_INSN_OPCODE:
1588
+	case JMP32_INSN_OPCODE:
1589
+	case JMP8_INSN_OPCODE:
1590
+		/*
1591
+		 * Control flow instructions without implied execution of the
1592
+		 * next instruction can be padded with INT3.
1593
+		 */
1594
+		for (i = insn.length; i < len; i++)
1595
+			BUG_ON(tp->text[i] != INT3_INSN_OPCODE);
1596
+		break;
1597
+
1598
+	default:
1599
+		BUG_ON(len != insn.length);
1600
+	};
1601
+
1602
+
1603
+	switch (tp->opcode) {
1604
+	case INT3_INSN_OPCODE:
1605
+	case RET_INSN_OPCODE:
1606
+		break;
1607
+
1608
+	case CALL_INSN_OPCODE:
1609
+	case JMP32_INSN_OPCODE:
1610
+	case JMP8_INSN_OPCODE:
1611
+		tp->disp = insn.immediate.value;
1612
+		break;
1613
+
1614
+	default: /* assume NOP */
1615
+		switch (len) {
1616
+		case 2: /* NOP2 -- emulate as JMP8+0 */
1617
+			BUG_ON(memcmp(emulate, ideal_nops[len], len));
1618
+			tp->opcode = JMP8_INSN_OPCODE;
1619
+			tp->disp = 0;
1620
+			break;
1621
+
1622
+		case 5: /* NOP5 -- emulate as JMP32+0 */
1623
+			BUG_ON(memcmp(emulate, ideal_nops[NOP_ATOMIC5], len));
1624
+			tp->opcode = JMP32_INSN_OPCODE;
1625
+			tp->disp = 0;
1626
+			break;
1627
+
1628
+		default: /* unknown instruction */
1629
+			BUG();
1630
+		}
1631
+		break;
1632
+	}
1633
+}
1634
+
1635
+/*
1636
+ * We hard rely on the tp_vec being ordered; ensure this is so by flushing
1637
+ * early if needed.
1638
+ */
1639
+static bool tp_order_fail(void *addr)
1640
+{
1641
+	struct text_poke_loc *tp;
1642
+
1643
+	if (!tp_vec_nr)
1644
+		return false;
1645
+
1646
+	if (!addr) /* force */
1647
+		return true;
1648
+
1649
+	tp = &tp_vec[tp_vec_nr - 1];
1650
+	if ((unsigned long)text_poke_addr(tp) > (unsigned long)addr)
1651
+		return true;
1652
+
1653
+	return false;
1654
+}
1655
+
1656
+static void text_poke_flush(void *addr)
1657
+{
1658
+	if (tp_vec_nr == TP_VEC_MAX || tp_order_fail(addr)) {
1659
+		text_poke_bp_batch(tp_vec, tp_vec_nr);
1660
+		tp_vec_nr = 0;
1661
+	}
1662
+}
1663
+
1664
+void text_poke_finish(void)
1665
+{
1666
+	text_poke_flush(NULL);
1667
+}
1668
+
1669
+void __ref text_poke_queue(void *addr, const void *opcode, size_t len, const void *emulate)
1670
+{
1671
+	struct text_poke_loc *tp;
1672
+
1673
+	if (unlikely(system_state == SYSTEM_BOOTING)) {
1674
+		text_poke_early(addr, opcode, len);
1675
+		return;
1676
+	}
1677
+
1678
+	text_poke_flush(addr);
1679
+
1680
+	tp = &tp_vec[tp_vec_nr++];
1681
+	text_poke_loc_init(tp, addr, opcode, len, emulate);
7781682 }
7791683 
7801684 /**
....@@ -784,62 +1688,19 @@
7841688  * @len:	length to copy
7851689  * @handler:	address to jump to when the temporary breakpoint is hit
7861690  *
787
- * Modify multi-byte instruction by using int3 breakpoint on SMP.
788
- * We completely avoid stop_machine() here, and achieve the
789
- * synchronization using int3 breakpoint.
790
- *
791
- * The way it is done:
792
- *	- add a int3 trap to the address that will be patched
793
- *	- sync cores
794
- *	- update all but the first byte of the patched range
795
- *	- sync cores
796
- *	- replace the first byte (int3) by the first byte of
797
- *	  replacing opcode
798
- *	- sync cores
1691
+ * Update a single instruction with the vector in the stack, avoiding
1692
+ * dynamically allocated memory. This function should be used when it is
1693
+ * not possible to allocate memory.
7991694  */
800
-void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler)
1695
+void __ref text_poke_bp(void *addr, const void *opcode, size_t len, const void *emulate)
8011696 {
802
-	unsigned char int3 = 0xcc;
1697
+	struct text_poke_loc tp;
8031698 
804
-	bp_int3_handler = handler;
805
-	bp_int3_addr = (u8 *)addr + sizeof(int3);
806
-	bp_patching_in_progress = true;
807
-
808
-	lockdep_assert_held(&text_mutex);
809
-
810
-	/*
811
-	 * Corresponding read barrier in int3 notifier for making sure the
812
-	 * in_progress and handler are correctly ordered wrt. patching.
813
-	 */
814
-	smp_wmb();
815
-
816
-	text_poke(addr, &int3, sizeof(int3));
817
-
818
-	on_each_cpu(do_sync_core, NULL, 1);
819
-
820
-	if (len - sizeof(int3) > 0) {
821
-		/* patch all but the first byte */
822
-		text_poke((char *)addr + sizeof(int3),
823
-			  (const char *) opcode + sizeof(int3),
824
-			  len - sizeof(int3));
825
-		/*
826
-		 * According to Intel, this core syncing is very likely
827
-		 * not necessary and we'd be safe even without it. But
828
-		 * better safe than sorry (plus there's not only Intel).
829
-		 */
830
-		on_each_cpu(do_sync_core, NULL, 1);
1699
+	if (unlikely(system_state == SYSTEM_BOOTING)) {
1700
+		text_poke_early(addr, opcode, len);
1701
+		return;
8311702 	}
8321703 
833
-	/* patch the first byte */
834
-	text_poke(addr, opcode, sizeof(int3));
835
-
836
-	on_each_cpu(do_sync_core, NULL, 1);
837
-	/*
838
-	 * sync_core() implies an smp_mb() and orders this store against
839
-	 * the writing of the new instruction.
840
-	 */
841
-	bp_patching_in_progress = false;
842
-
843
-	return addr;
1704
+	text_poke_loc_init(&tp, addr, opcode, len, emulate);
1705
+	text_poke_bp_batch(&tp, 1);
8441706 }
845
-