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#include <asm/paravirt.h>
  32#include <asm/asm-prototypes.h>
 
  33
  34int __read_mostly alternatives_patched;
  35
  36EXPORT_SYMBOL_GPL(alternatives_patched);
  37
  38#define MAX_PATCH_LEN (255-1)
  39
  40static int __initdata_or_module debug_alternative;
 
 
 
 
 
 
 
  41
  42static int __init debug_alt(char *str)
  43{
  44	debug_alternative = 1;
 
 
 
 
 
  45	return 1;
  46}
  47__setup("debug-alternative", debug_alt);
  48
  49static int noreplace_smp;
  50
  51static int __init setup_noreplace_smp(char *str)
  52{
  53	noreplace_smp = 1;
  54	return 1;
  55}
  56__setup("noreplace-smp", setup_noreplace_smp);
  57
  58#define DPRINTK(fmt, args...)						\
  59do {									\
  60	if (debug_alternative)						\
  61		printk(KERN_DEBUG pr_fmt(fmt) "\n", ##args);		\
  62} while (0)
  63
  64#define DUMP_BYTES(buf, len, fmt, args...)				\
  65do {									\
  66	if (unlikely(debug_alternative)) {				\
  67		int j;							\
  68									\
  69		if (!(len))						\
  70			break;						\
  71									\
  72		printk(KERN_DEBUG pr_fmt(fmt), ##args);			\
  73		for (j = 0; j < (len) - 1; j++)				\
  74			printk(KERN_CONT "%02hhx ", buf[j]);		\
  75		printk(KERN_CONT "%02hhx\n", buf[j]);			\
  76	}								\
  77} while (0)
  78
  79static const unsigned char x86nops[] =
  80{
  81	BYTES_NOP1,
  82	BYTES_NOP2,
  83	BYTES_NOP3,
  84	BYTES_NOP4,
  85	BYTES_NOP5,
  86	BYTES_NOP6,
  87	BYTES_NOP7,
  88	BYTES_NOP8,
 
 
 
 
 
  89};
  90
  91const unsigned char * const x86_nops[ASM_NOP_MAX+1] =
  92{
  93	NULL,
  94	x86nops,
  95	x86nops + 1,
  96	x86nops + 1 + 2,
  97	x86nops + 1 + 2 + 3,
  98	x86nops + 1 + 2 + 3 + 4,
  99	x86nops + 1 + 2 + 3 + 4 + 5,
 100	x86nops + 1 + 2 + 3 + 4 + 5 + 6,
 101	x86nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
 
 
 
 
 
 102};
 103
 104/* Use this to add nops to a buffer, then text_poke the whole buffer. */
 105static void __init_or_module add_nops(void *insns, unsigned int len)
 
 
 
 
 
 
 
 
 106{
 107	while (len > 0) {
 108		unsigned int noplen = len;
 109		if (noplen > ASM_NOP_MAX)
 110			noplen = ASM_NOP_MAX;
 111		memcpy(insns, x86_nops[noplen], noplen);
 112		insns += noplen;
 113		len -= noplen;
 
 114	}
 
 
 
 
 
 
 
 
 
 
 
 115}
 116
 117extern s32 __retpoline_sites[], __retpoline_sites_end[];
 118extern s32 __return_sites[], __return_sites_end[];
 119extern s32 __cfi_sites[], __cfi_sites_end[];
 120extern s32 __ibt_endbr_seal[], __ibt_endbr_seal_end[];
 121extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
 122extern s32 __smp_locks[], __smp_locks_end[];
 123void text_poke_early(void *addr, const void *opcode, size_t len);
 124
 125/*
 126 * Are we looking at a near JMP with a 1 or 4-byte displacement.
 127 */
 128static inline bool is_jmp(const u8 opcode)
 129{
 130	return opcode == 0xeb || opcode == 0xe9;
 
 
 
 
 
 
 
 
 
 
 
 131}
 132
 133static void __init_or_module
 134recompute_jump(struct alt_instr *a, u8 *orig_insn, u8 *repl_insn, u8 *insn_buff)
 
 
 
 135{
 136	u8 *next_rip, *tgt_rip;
 137	s32 n_dspl, o_dspl;
 138	int repl_len;
 139
 140	if (a->replacementlen != 5)
 141		return;
 142
 143	o_dspl = *(s32 *)(insn_buff + 1);
 
 
 144
 145	/* next_rip of the replacement JMP */
 146	next_rip = repl_insn + a->replacementlen;
 147	/* target rip of the replacement JMP */
 148	tgt_rip  = next_rip + o_dspl;
 149	n_dspl = tgt_rip - orig_insn;
 150
 151	DPRINTK("target RIP: %px, new_displ: 0x%x", tgt_rip, n_dspl);
 152
 153	if (tgt_rip - orig_insn >= 0) {
 154		if (n_dspl - 2 <= 127)
 155			goto two_byte_jmp;
 156		else
 157			goto five_byte_jmp;
 158	/* negative offset */
 159	} else {
 160		if (((n_dspl - 2) & 0xff) == (n_dspl - 2))
 161			goto two_byte_jmp;
 162		else
 163			goto five_byte_jmp;
 164	}
 165
 166two_byte_jmp:
 167	n_dspl -= 2;
 168
 169	insn_buff[0] = 0xeb;
 170	insn_buff[1] = (s8)n_dspl;
 171	add_nops(insn_buff + 2, 3);
 172
 173	repl_len = 2;
 174	goto done;
 
 
 
 
 
 
 175
 176five_byte_jmp:
 177	n_dspl -= 5;
 
 
 
 
 
 178
 179	insn_buff[0] = 0xe9;
 180	*(s32 *)&insn_buff[1] = n_dspl;
 181
 182	repl_len = 5;
 
 
 183
 184done:
 
 
 
 185
 186	DPRINTK("final displ: 0x%08x, JMP 0x%lx",
 187		n_dspl, (unsigned long)orig_insn + n_dspl + repl_len);
 188}
 189
 190/*
 191 * optimize_nops_range() - Optimize a sequence of single byte NOPs (0x90)
 192 *
 193 * @instr: instruction byte stream
 194 * @instrlen: length of the above
 195 * @off: offset within @instr where the first NOP has been detected
 196 *
 197 * Return: number of NOPs found (and replaced).
 198 */
 199static __always_inline int optimize_nops_range(u8 *instr, u8 instrlen, int off)
 200{
 201	unsigned long flags;
 202	int i = off, nnops;
 203
 204	while (i < instrlen) {
 205		if (instr[i] != 0x90)
 206			break;
 207
 208		i++;
 209	}
 
 
 210
 211	nnops = i - off;
 
 
 212
 213	if (nnops <= 1)
 214		return nnops;
 
 215
 216	local_irq_save(flags);
 217	add_nops(instr + off, nnops);
 
 218	local_irq_restore(flags);
 219
 220	DUMP_BYTES(instr, instrlen, "%px: [%d:%d) optimized NOPs: ", instr, off, i);
 221
 222	return nnops;
 223}
 224
 225/*
 226 * "noinline" to cause control flow change and thus invalidate I$ and
 227 * cause refetch after modification.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 228 */
 229static void __init_or_module noinline optimize_nops(u8 *instr, size_t len)
 
 
 
 
 
 
 
 
 
 
 
 230{
 231	struct insn insn;
 232	int i = 0;
 
 
 
 
 
 233
 
 
 
 
 234	/*
 235	 * Jump over the non-NOP insns and optimize single-byte NOPs into bigger
 236	 * ones.
 237	 */
 238	for (;;) {
 239		if (insn_decode_kernel(&insn, &instr[i]))
 240			return;
 241
 242		/*
 243		 * See if this and any potentially following NOPs can be
 244		 * optimized.
 245		 */
 246		if (insn.length == 1 && insn.opcode.bytes[0] == 0x90)
 247			i += optimize_nops_range(instr, len, i);
 248		else
 249			i += insn.length;
 250
 251		if (i >= len)
 
 
 
 252			return;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 253	}
 254}
 255
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 256/*
 257 * Replace instructions with better alternatives for this CPU type. This runs
 258 * before SMP is initialized to avoid SMP problems with self modifying code.
 259 * This implies that asymmetric systems where APs have less capabilities than
 260 * the boot processor are not handled. Tough. Make sure you disable such
 261 * features by hand.
 262 *
 263 * Marked "noinline" to cause control flow change and thus insn cache
 264 * to refetch changed I$ lines.
 265 */
 266void __init_or_module noinline apply_alternatives(struct alt_instr *start,
 267						  struct alt_instr *end)
 268{
 269	struct alt_instr *a;
 270	u8 *instr, *replacement;
 271	u8 insn_buff[MAX_PATCH_LEN];
 272
 273	DPRINTK("alt table %px, -> %px", start, end);
 
 
 
 
 
 
 
 
 
 
 
 274	/*
 275	 * The scan order should be from start to end. A later scanned
 276	 * alternative code can overwrite previously scanned alternative code.
 277	 * Some kernel functions (e.g. memcpy, memset, etc) use this order to
 278	 * patch code.
 279	 *
 280	 * So be careful if you want to change the scan order to any other
 281	 * order.
 282	 */
 283	for (a = start; a < end; a++) {
 284		int insn_buff_sz = 0;
 285		/* Mask away "NOT" flag bit for feature to test. */
 286		u16 feature = a->cpuid & ~ALTINSTR_FLAG_INV;
 287
 288		instr = (u8 *)&a->instr_offset + a->instr_offset;
 289		replacement = (u8 *)&a->repl_offset + a->repl_offset;
 290		BUG_ON(a->instrlen > sizeof(insn_buff));
 291		BUG_ON(feature >= (NCAPINTS + NBUGINTS) * 32);
 292
 293		/*
 294		 * Patch if either:
 295		 * - feature is present
 296		 * - feature not present but ALTINSTR_FLAG_INV is set to mean,
 297		 *   patch if feature is *NOT* present.
 298		 */
 299		if (!boot_cpu_has(feature) == !(a->cpuid & ALTINSTR_FLAG_INV))
 300			goto next;
 
 
 301
 302		DPRINTK("feat: %s%d*32+%d, old: (%pS (%px) len: %d), repl: (%px, len: %d)",
 303			(a->cpuid & ALTINSTR_FLAG_INV) ? "!" : "",
 304			feature >> 5,
 305			feature & 0x1f,
 306			instr, instr, a->instrlen,
 307			replacement, a->replacementlen);
 308
 309		DUMP_BYTES(instr, a->instrlen, "%px:   old_insn: ", instr);
 310		DUMP_BYTES(replacement, a->replacementlen, "%px:   rpl_insn: ", replacement);
 311
 312		memcpy(insn_buff, replacement, a->replacementlen);
 313		insn_buff_sz = a->replacementlen;
 314
 315		/*
 316		 * 0xe8 is a relative jump; fix the offset.
 317		 *
 318		 * Instruction length is checked before the opcode to avoid
 319		 * accessing uninitialized bytes for zero-length replacements.
 320		 */
 321		if (a->replacementlen == 5 && *insn_buff == 0xe8) {
 322			*(s32 *)(insn_buff + 1) += replacement - instr;
 323			DPRINTK("Fix CALL offset: 0x%x, CALL 0x%lx",
 324				*(s32 *)(insn_buff + 1),
 325				(unsigned long)instr + *(s32 *)(insn_buff + 1) + 5);
 326		}
 327
 328		if (a->replacementlen && is_jmp(replacement[0]))
 329			recompute_jump(a, instr, replacement, insn_buff);
 330
 331		for (; insn_buff_sz < a->instrlen; insn_buff_sz++)
 332			insn_buff[insn_buff_sz] = 0x90;
 333
 334		DUMP_BYTES(insn_buff, insn_buff_sz, "%px: final_insn: ", instr);
 335
 336		text_poke_early(instr, insn_buff, insn_buff_sz);
 
 
 337
 338next:
 339		optimize_nops(instr, a->instrlen);
 340	}
 
 
 
 
 
 
 
 
 341}
 342
 343#if defined(CONFIG_RETPOLINE) && defined(CONFIG_OBJTOOL)
 344
 345/*
 346 * CALL/JMP *%\reg
 347 */
 348static int emit_indirect(int op, int reg, u8 *bytes)
 349{
 350	int i = 0;
 351	u8 modrm;
 352
 353	switch (op) {
 354	case CALL_INSN_OPCODE:
 355		modrm = 0x10; /* Reg = 2; CALL r/m */
 356		break;
 357
 358	case JMP32_INSN_OPCODE:
 359		modrm = 0x20; /* Reg = 4; JMP r/m */
 360		break;
 361
 362	default:
 363		WARN_ON_ONCE(1);
 364		return -1;
 365	}
 366
 367	if (reg >= 8) {
 368		bytes[i++] = 0x41; /* REX.B prefix */
 369		reg -= 8;
 370	}
 371
 372	modrm |= 0xc0; /* Mod = 3 */
 373	modrm += reg;
 374
 375	bytes[i++] = 0xff; /* opcode */
 376	bytes[i++] = modrm;
 377
 378	return i;
 379}
 380
 381static inline bool is_jcc32(struct insn *insn)
 382{
 383	/* Jcc.d32 second opcode byte is in the range: 0x80-0x8f */
 384	return insn->opcode.bytes[0] == 0x0f && (insn->opcode.bytes[1] & 0xf0) == 0x80;
 385}
 386
 387static int emit_call_track_retpoline(void *addr, struct insn *insn, int reg, u8 *bytes)
 388{
 389	u8 op = insn->opcode.bytes[0];
 390	int i = 0;
 391
 392	/*
 393	 * Clang does 'weird' Jcc __x86_indirect_thunk_r11 conditional
 394	 * tail-calls. Deal with them.
 395	 */
 396	if (is_jcc32(insn)) {
 397		bytes[i++] = op;
 398		op = insn->opcode.bytes[1];
 399		goto clang_jcc;
 400	}
 401
 402	if (insn->length == 6)
 403		bytes[i++] = 0x2e; /* CS-prefix */
 404
 405	switch (op) {
 406	case CALL_INSN_OPCODE:
 407		__text_gen_insn(bytes+i, op, addr+i,
 408				__x86_indirect_call_thunk_array[reg],
 409				CALL_INSN_SIZE);
 410		i += CALL_INSN_SIZE;
 411		break;
 412
 413	case JMP32_INSN_OPCODE:
 414clang_jcc:
 415		__text_gen_insn(bytes+i, op, addr+i,
 416				__x86_indirect_jump_thunk_array[reg],
 417				JMP32_INSN_SIZE);
 418		i += JMP32_INSN_SIZE;
 419		break;
 420
 421	default:
 422		WARN(1, "%pS %px %*ph\n", addr, addr, 6, addr);
 423		return -1;
 424	}
 425
 426	WARN_ON_ONCE(i != insn->length);
 427
 428	return i;
 429}
 430
 431/*
 432 * Rewrite the compiler generated retpoline thunk calls.
 433 *
 434 * For spectre_v2=off (!X86_FEATURE_RETPOLINE), rewrite them into immediate
 435 * indirect instructions, avoiding the extra indirection.
 436 *
 437 * For example, convert:
 438 *
 439 *   CALL __x86_indirect_thunk_\reg
 440 *
 441 * into:
 442 *
 443 *   CALL *%\reg
 444 *
 445 * It also tries to inline spectre_v2=retpoline,lfence when size permits.
 446 */
 447static int patch_retpoline(void *addr, struct insn *insn, u8 *bytes)
 448{
 449	retpoline_thunk_t *target;
 450	int reg, ret, i = 0;
 451	u8 op, cc;
 452
 453	target = addr + insn->length + insn->immediate.value;
 454	reg = target - __x86_indirect_thunk_array;
 455
 456	if (WARN_ON_ONCE(reg & ~0xf))
 457		return -1;
 458
 459	/* If anyone ever does: CALL/JMP *%rsp, we're in deep trouble. */
 460	BUG_ON(reg == 4);
 461
 462	if (cpu_feature_enabled(X86_FEATURE_RETPOLINE) &&
 463	    !cpu_feature_enabled(X86_FEATURE_RETPOLINE_LFENCE)) {
 464		if (cpu_feature_enabled(X86_FEATURE_CALL_DEPTH))
 465			return emit_call_track_retpoline(addr, insn, reg, bytes);
 466
 467		return -1;
 468	}
 469
 470	op = insn->opcode.bytes[0];
 471
 472	/*
 473	 * Convert:
 474	 *
 475	 *   Jcc.d32 __x86_indirect_thunk_\reg
 476	 *
 477	 * into:
 478	 *
 479	 *   Jncc.d8 1f
 480	 *   [ LFENCE ]
 481	 *   JMP *%\reg
 482	 *   [ NOP ]
 483	 * 1:
 484	 */
 485	if (is_jcc32(insn)) {
 486		cc = insn->opcode.bytes[1] & 0xf;
 487		cc ^= 1; /* invert condition */
 488
 489		bytes[i++] = 0x70 + cc;        /* Jcc.d8 */
 490		bytes[i++] = insn->length - 2; /* sizeof(Jcc.d8) == 2 */
 491
 492		/* Continue as if: JMP.d32 __x86_indirect_thunk_\reg */
 493		op = JMP32_INSN_OPCODE;
 494	}
 495
 496	/*
 497	 * For RETPOLINE_LFENCE: prepend the indirect CALL/JMP with an LFENCE.
 498	 */
 499	if (cpu_feature_enabled(X86_FEATURE_RETPOLINE_LFENCE)) {
 500		bytes[i++] = 0x0f;
 501		bytes[i++] = 0xae;
 502		bytes[i++] = 0xe8; /* LFENCE */
 503	}
 504
 505	ret = emit_indirect(op, reg, bytes + i);
 506	if (ret < 0)
 507		return ret;
 508	i += ret;
 509
 510	/*
 511	 * The compiler is supposed to EMIT an INT3 after every unconditional
 512	 * JMP instruction due to AMD BTC. However, if the compiler is too old
 513	 * or SLS isn't enabled, we still need an INT3 after indirect JMPs
 514	 * even on Intel.
 515	 */
 516	if (op == JMP32_INSN_OPCODE && i < insn->length)
 517		bytes[i++] = INT3_INSN_OPCODE;
 518
 519	for (; i < insn->length;)
 520		bytes[i++] = BYTES_NOP1;
 521
 522	return i;
 523}
 524
 525/*
 526 * Generated by 'objtool --retpoline'.
 527 */
 528void __init_or_module noinline apply_retpolines(s32 *start, s32 *end)
 529{
 530	s32 *s;
 531
 532	for (s = start; s < end; s++) {
 533		void *addr = (void *)s + *s;
 534		struct insn insn;
 535		int len, ret;
 536		u8 bytes[16];
 537		u8 op1, op2;
 538
 539		ret = insn_decode_kernel(&insn, addr);
 540		if (WARN_ON_ONCE(ret < 0))
 541			continue;
 542
 543		op1 = insn.opcode.bytes[0];
 544		op2 = insn.opcode.bytes[1];
 545
 546		switch (op1) {
 547		case CALL_INSN_OPCODE:
 548		case JMP32_INSN_OPCODE:
 549			break;
 550
 551		case 0x0f: /* escape */
 552			if (op2 >= 0x80 && op2 <= 0x8f)
 553				break;
 554			fallthrough;
 555		default:
 556			WARN_ON_ONCE(1);
 557			continue;
 558		}
 559
 560		DPRINTK("retpoline at: %pS (%px) len: %d to: %pS",
 561			addr, addr, insn.length,
 562			addr + insn.length + insn.immediate.value);
 563
 564		len = patch_retpoline(addr, &insn, bytes);
 565		if (len == insn.length) {
 566			optimize_nops(bytes, len);
 567			DUMP_BYTES(((u8*)addr),  len, "%px: orig: ", addr);
 568			DUMP_BYTES(((u8*)bytes), len, "%px: repl: ", addr);
 569			text_poke_early(addr, bytes, len);
 570		}
 571	}
 572}
 573
 574#ifdef CONFIG_RETHUNK
 575
 576#ifdef CONFIG_CALL_THUNKS
 577void (*x86_return_thunk)(void) __ro_after_init = &__x86_return_thunk;
 578#endif
 579
 580/*
 581 * Rewrite the compiler generated return thunk tail-calls.
 582 *
 583 * For example, convert:
 584 *
 585 *   JMP __x86_return_thunk
 586 *
 587 * into:
 588 *
 589 *   RET
 590 */
 591static int patch_return(void *addr, struct insn *insn, u8 *bytes)
 592{
 593	int i = 0;
 594
 
 595	if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) {
 596		if (x86_return_thunk == __x86_return_thunk)
 597			return -1;
 598
 599		i = JMP32_INSN_SIZE;
 600		__text_gen_insn(bytes, JMP32_INSN_OPCODE, addr, x86_return_thunk, i);
 601	} else {
 
 602		bytes[i++] = RET_INSN_OPCODE;
 603	}
 604
 605	for (; i < insn->length;)
 606		bytes[i++] = INT3_INSN_OPCODE;
 607	return i;
 608}
 609
 610void __init_or_module noinline apply_returns(s32 *start, s32 *end)
 611{
 612	s32 *s;
 613
 
 
 
 614	for (s = start; s < end; s++) {
 615		void *dest = NULL, *addr = (void *)s + *s;
 616		struct insn insn;
 617		int len, ret;
 618		u8 bytes[16];
 619		u8 op;
 620
 621		ret = insn_decode_kernel(&insn, addr);
 622		if (WARN_ON_ONCE(ret < 0))
 623			continue;
 624
 625		op = insn.opcode.bytes[0];
 626		if (op == JMP32_INSN_OPCODE)
 627			dest = addr + insn.length + insn.immediate.value;
 628
 629		if (__static_call_fixup(addr, op, dest) ||
 630		    WARN_ONCE(dest != &__x86_return_thunk,
 631			      "missing return thunk: %pS-%pS: %*ph",
 632			      addr, dest, 5, addr))
 633			continue;
 634
 635		DPRINTK("return thunk at: %pS (%px) len: %d to: %pS",
 636			addr, addr, insn.length,
 637			addr + insn.length + insn.immediate.value);
 638
 639		len = patch_return(addr, &insn, bytes);
 640		if (len == insn.length) {
 641			DUMP_BYTES(((u8*)addr),  len, "%px: orig: ", addr);
 642			DUMP_BYTES(((u8*)bytes), len, "%px: repl: ", addr);
 643			text_poke_early(addr, bytes, len);
 644		}
 645	}
 646}
 647#else
 648void __init_or_module noinline apply_returns(s32 *start, s32 *end) { }
 649#endif /* CONFIG_RETHUNK */
 650
 651#else /* !CONFIG_RETPOLINE || !CONFIG_OBJTOOL */
 652
 653void __init_or_module noinline apply_retpolines(s32 *start, s32 *end) { }
 654void __init_or_module noinline apply_returns(s32 *start, s32 *end) { }
 655
 656#endif /* CONFIG_RETPOLINE && CONFIG_OBJTOOL */
 657
 658#ifdef CONFIG_X86_KERNEL_IBT
 659
 660static void poison_endbr(void *addr, bool warn)
 
 
 661{
 662	u32 endbr, poison = gen_endbr_poison();
 663
 664	if (WARN_ON_ONCE(get_kernel_nofault(endbr, addr)))
 665		return;
 666
 667	if (!is_endbr(endbr)) {
 668		WARN_ON_ONCE(warn);
 669		return;
 670	}
 671
 672	DPRINTK("ENDBR at: %pS (%px)", addr, addr);
 673
 674	/*
 675	 * When we have IBT, the lack of ENDBR will trigger #CP
 676	 */
 677	DUMP_BYTES(((u8*)addr), 4, "%px: orig: ", addr);
 678	DUMP_BYTES(((u8*)&poison), 4, "%px: repl: ", addr);
 679	text_poke_early(addr, &poison, 4);
 680}
 681
 682/*
 683 * Generated by: objtool --ibt
 
 
 
 684 */
 685void __init_or_module noinline apply_ibt_endbr(s32 *start, s32 *end)
 686{
 687	s32 *s;
 688
 689	for (s = start; s < end; s++) {
 690		void *addr = (void *)s + *s;
 691
 692		poison_endbr(addr, true);
 693		if (IS_ENABLED(CONFIG_FINEIBT))
 694			poison_endbr(addr - 16, false);
 695	}
 696}
 697
 698#else
 699
 700void __init_or_module apply_ibt_endbr(s32 *start, s32 *end) { }
 701
 702#endif /* CONFIG_X86_KERNEL_IBT */
 703
 704#ifdef CONFIG_FINEIBT
 
 
 
 
 
 
 705
 706enum cfi_mode {
 707	CFI_DEFAULT,
 708	CFI_OFF,
 709	CFI_KCFI,
 710	CFI_FINEIBT,
 711};
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 712
 713static enum cfi_mode cfi_mode __ro_after_init = CFI_DEFAULT;
 714static bool cfi_rand __ro_after_init = true;
 715static u32  cfi_seed __ro_after_init;
 716
 717/*
 718 * Re-hash the CFI hash with a boot-time seed while making sure the result is
 719 * not a valid ENDBR instruction.
 720 */
 721static u32 cfi_rehash(u32 hash)
 722{
 723	hash ^= cfi_seed;
 724	while (unlikely(is_endbr(hash) || is_endbr(-hash))) {
 725		bool lsb = hash & 1;
 726		hash >>= 1;
 727		if (lsb)
 728			hash ^= 0x80200003;
 729	}
 730	return hash;
 731}
 732
 733static __init int cfi_parse_cmdline(char *str)
 734{
 735	if (!str)
 736		return -EINVAL;
 737
 738	while (str) {
 739		char *next = strchr(str, ',');
 740		if (next) {
 741			*next = 0;
 742			next++;
 743		}
 744
 745		if (!strcmp(str, "auto")) {
 746			cfi_mode = CFI_DEFAULT;
 747		} else if (!strcmp(str, "off")) {
 748			cfi_mode = CFI_OFF;
 749			cfi_rand = false;
 750		} else if (!strcmp(str, "kcfi")) {
 751			cfi_mode = CFI_KCFI;
 752		} else if (!strcmp(str, "fineibt")) {
 753			cfi_mode = CFI_FINEIBT;
 754		} else if (!strcmp(str, "norand")) {
 755			cfi_rand = false;
 756		} else {
 757			pr_err("Ignoring unknown cfi option (%s).", str);
 758		}
 759
 760		str = next;
 761	}
 762
 763	return 0;
 764}
 765early_param("cfi", cfi_parse_cmdline);
 766
 767/*
 768 * kCFI						FineIBT
 769 *
 770 * __cfi_\func:					__cfi_\func:
 771 *	movl   $0x12345678,%eax		// 5	     endbr64			// 4
 772 *	nop					     subl   $0x12345678,%r10d   // 7
 773 *	nop					     jz     1f			// 2
 774 *	nop					     ud2			// 2
 775 *	nop					1:   nop			// 1
 776 *	nop
 777 *	nop
 778 *	nop
 779 *	nop
 780 *	nop
 781 *	nop
 782 *	nop
 783 *
 784 *
 785 * caller:					caller:
 786 *	movl	$(-0x12345678),%r10d	 // 6	     movl   $0x12345678,%r10d	// 6
 787 *	addl	$-15(%r11),%r10d	 // 4	     sub    $16,%r11		// 4
 788 *	je	1f			 // 2	     nop4			// 4
 789 *	ud2				 // 2
 790 * 1:	call	__x86_indirect_thunk_r11 // 5	     call   *%r11; nop2;	// 5
 791 *
 792 */
 793
 794asm(	".pushsection .rodata			\n"
 795	"fineibt_preamble_start:		\n"
 796	"	endbr64				\n"
 797	"	subl	$0x12345678, %r10d	\n"
 798	"	je	fineibt_preamble_end	\n"
 799	"	ud2				\n"
 800	"	nop				\n"
 801	"fineibt_preamble_end:			\n"
 802	".popsection\n"
 803);
 804
 805extern u8 fineibt_preamble_start[];
 806extern u8 fineibt_preamble_end[];
 807
 808#define fineibt_preamble_size (fineibt_preamble_end - fineibt_preamble_start)
 809#define fineibt_preamble_hash 7
 810
 811asm(	".pushsection .rodata			\n"
 812	"fineibt_caller_start:			\n"
 813	"	movl	$0x12345678, %r10d	\n"
 814	"	sub	$16, %r11		\n"
 815	ASM_NOP4
 816	"fineibt_caller_end:			\n"
 817	".popsection				\n"
 818);
 819
 820extern u8 fineibt_caller_start[];
 821extern u8 fineibt_caller_end[];
 822
 823#define fineibt_caller_size (fineibt_caller_end - fineibt_caller_start)
 824#define fineibt_caller_hash 2
 825
 826#define fineibt_caller_jmp (fineibt_caller_size - 2)
 827
 828static u32 decode_preamble_hash(void *addr)
 829{
 830	u8 *p = addr;
 831
 832	/* b8 78 56 34 12          mov    $0x12345678,%eax */
 833	if (p[0] == 0xb8)
 834		return *(u32 *)(addr + 1);
 835
 836	return 0; /* invalid hash value */
 837}
 838
 839static u32 decode_caller_hash(void *addr)
 840{
 841	u8 *p = addr;
 842
 843	/* 41 ba 78 56 34 12       mov    $0x12345678,%r10d */
 844	if (p[0] == 0x41 && p[1] == 0xba)
 845		return -*(u32 *)(addr + 2);
 846
 847	/* e8 0c 78 56 34 12	   jmp.d8  +12 */
 848	if (p[0] == JMP8_INSN_OPCODE && p[1] == fineibt_caller_jmp)
 849		return -*(u32 *)(addr + 2);
 850
 851	return 0; /* invalid hash value */
 852}
 853
 854/* .retpoline_sites */
 855static int cfi_disable_callers(s32 *start, s32 *end)
 856{
 857	/*
 858	 * Disable kCFI by patching in a JMP.d8, this leaves the hash immediate
 859	 * in tact for later usage. Also see decode_caller_hash() and
 860	 * cfi_rewrite_callers().
 861	 */
 862	const u8 jmp[] = { JMP8_INSN_OPCODE, fineibt_caller_jmp };
 863	s32 *s;
 864
 865	for (s = start; s < end; s++) {
 866		void *addr = (void *)s + *s;
 867		u32 hash;
 868
 869		addr -= fineibt_caller_size;
 870		hash = decode_caller_hash(addr);
 871		if (!hash) /* nocfi callers */
 872			continue;
 873
 874		text_poke_early(addr, jmp, 2);
 875	}
 876
 877	return 0;
 878}
 879
 880static int cfi_enable_callers(s32 *start, s32 *end)
 881{
 882	/*
 883	 * Re-enable kCFI, undo what cfi_disable_callers() did.
 884	 */
 885	const u8 mov[] = { 0x41, 0xba };
 886	s32 *s;
 887
 888	for (s = start; s < end; s++) {
 889		void *addr = (void *)s + *s;
 890		u32 hash;
 891
 892		addr -= fineibt_caller_size;
 893		hash = decode_caller_hash(addr);
 894		if (!hash) /* nocfi callers */
 895			continue;
 896
 897		text_poke_early(addr, mov, 2);
 898	}
 899
 900	return 0;
 901}
 902
 903/* .cfi_sites */
 904static int cfi_rand_preamble(s32 *start, s32 *end)
 905{
 906	s32 *s;
 907
 908	for (s = start; s < end; s++) {
 909		void *addr = (void *)s + *s;
 910		u32 hash;
 911
 912		hash = decode_preamble_hash(addr);
 913		if (WARN(!hash, "no CFI hash found at: %pS %px %*ph\n",
 914			 addr, addr, 5, addr))
 915			return -EINVAL;
 916
 917		hash = cfi_rehash(hash);
 918		text_poke_early(addr + 1, &hash, 4);
 919	}
 920
 921	return 0;
 922}
 923
 924static int cfi_rewrite_preamble(s32 *start, s32 *end)
 925{
 926	s32 *s;
 927
 928	for (s = start; s < end; s++) {
 929		void *addr = (void *)s + *s;
 930		u32 hash;
 931
 932		hash = decode_preamble_hash(addr);
 933		if (WARN(!hash, "no CFI hash found at: %pS %px %*ph\n",
 934			 addr, addr, 5, addr))
 935			return -EINVAL;
 936
 937		text_poke_early(addr, fineibt_preamble_start, fineibt_preamble_size);
 938		WARN_ON(*(u32 *)(addr + fineibt_preamble_hash) != 0x12345678);
 939		text_poke_early(addr + fineibt_preamble_hash, &hash, 4);
 940	}
 941
 942	return 0;
 943}
 944
 
 
 
 
 
 
 
 
 
 
 
 945/* .retpoline_sites */
 946static int cfi_rand_callers(s32 *start, s32 *end)
 947{
 948	s32 *s;
 949
 950	for (s = start; s < end; s++) {
 951		void *addr = (void *)s + *s;
 952		u32 hash;
 953
 954		addr -= fineibt_caller_size;
 955		hash = decode_caller_hash(addr);
 956		if (hash) {
 957			hash = -cfi_rehash(hash);
 958			text_poke_early(addr + 2, &hash, 4);
 959		}
 960	}
 961
 962	return 0;
 963}
 964
 965static int cfi_rewrite_callers(s32 *start, s32 *end)
 966{
 967	s32 *s;
 968
 969	for (s = start; s < end; s++) {
 970		void *addr = (void *)s + *s;
 971		u32 hash;
 972
 973		addr -= fineibt_caller_size;
 974		hash = decode_caller_hash(addr);
 975		if (hash) {
 976			text_poke_early(addr, fineibt_caller_start, fineibt_caller_size);
 977			WARN_ON(*(u32 *)(addr + fineibt_caller_hash) != 0x12345678);
 978			text_poke_early(addr + fineibt_caller_hash, &hash, 4);
 979		}
 980		/* rely on apply_retpolines() */
 981	}
 982
 983	return 0;
 984}
 985
 986static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
 987			    s32 *start_cfi, s32 *end_cfi, bool builtin)
 988{
 989	int ret;
 990
 991	if (WARN_ONCE(fineibt_preamble_size != 16,
 992		      "FineIBT preamble wrong size: %ld", fineibt_preamble_size))
 993		return;
 994
 995	if (cfi_mode == CFI_DEFAULT) {
 996		cfi_mode = CFI_KCFI;
 997		if (HAS_KERNEL_IBT && cpu_feature_enabled(X86_FEATURE_IBT))
 998			cfi_mode = CFI_FINEIBT;
 999	}
1000
1001	/*
1002	 * Rewrite the callers to not use the __cfi_ stubs, such that we might
1003	 * rewrite them. This disables all CFI. If this succeeds but any of the
1004	 * later stages fails, we're without CFI.
1005	 */
1006	ret = cfi_disable_callers(start_retpoline, end_retpoline);
1007	if (ret)
1008		goto err;
1009
1010	if (cfi_rand) {
1011		if (builtin)
1012			cfi_seed = get_random_u32();
 
 
 
1013
1014		ret = cfi_rand_preamble(start_cfi, end_cfi);
1015		if (ret)
1016			goto err;
1017
1018		ret = cfi_rand_callers(start_retpoline, end_retpoline);
1019		if (ret)
1020			goto err;
1021	}
1022
1023	switch (cfi_mode) {
1024	case CFI_OFF:
1025		if (builtin)
1026			pr_info("Disabling CFI\n");
1027		return;
1028
1029	case CFI_KCFI:
1030		ret = cfi_enable_callers(start_retpoline, end_retpoline);
1031		if (ret)
1032			goto err;
1033
1034		if (builtin)
1035			pr_info("Using kCFI\n");
1036		return;
1037
1038	case CFI_FINEIBT:
 
1039		ret = cfi_rewrite_preamble(start_cfi, end_cfi);
1040		if (ret)
1041			goto err;
1042
 
1043		ret = cfi_rewrite_callers(start_retpoline, end_retpoline);
1044		if (ret)
1045			goto err;
1046
 
 
 
1047		if (builtin)
1048			pr_info("Using FineIBT CFI\n");
1049		return;
1050
1051	default:
1052		break;
1053	}
1054
1055err:
1056	pr_err("Something went horribly wrong trying to rewrite the CFI implementation.\n");
1057}
1058
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1059#else
1060
1061static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
1062			    s32 *start_cfi, s32 *end_cfi, bool builtin)
1063{
1064}
1065
 
 
 
 
1066#endif
1067
1068void apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
1069		   s32 *start_cfi, s32 *end_cfi)
1070{
1071	return __apply_fineibt(start_retpoline, end_retpoline,
1072			       start_cfi, end_cfi,
1073			       /* .builtin = */ false);
1074}
1075
1076#ifdef CONFIG_SMP
1077static void alternatives_smp_lock(const s32 *start, const s32 *end,
1078				  u8 *text, u8 *text_end)
1079{
1080	const s32 *poff;
1081
1082	for (poff = start; poff < end; poff++) {
1083		u8 *ptr = (u8 *)poff + *poff;
1084
1085		if (!*poff || ptr < text || ptr >= text_end)
1086			continue;
1087		/* turn DS segment override prefix into lock prefix */
1088		if (*ptr == 0x3e)
1089			text_poke(ptr, ((unsigned char []){0xf0}), 1);
1090	}
1091}
1092
1093static void alternatives_smp_unlock(const s32 *start, const s32 *end,
1094				    u8 *text, u8 *text_end)
1095{
1096	const s32 *poff;
1097
1098	for (poff = start; poff < end; poff++) {
1099		u8 *ptr = (u8 *)poff + *poff;
1100
1101		if (!*poff || ptr < text || ptr >= text_end)
1102			continue;
1103		/* turn lock prefix into DS segment override prefix */
1104		if (*ptr == 0xf0)
1105			text_poke(ptr, ((unsigned char []){0x3E}), 1);
1106	}
1107}
1108
1109struct smp_alt_module {
1110	/* what is this ??? */
1111	struct module	*mod;
1112	char		*name;
1113
1114	/* ptrs to lock prefixes */
1115	const s32	*locks;
1116	const s32	*locks_end;
1117
1118	/* .text segment, needed to avoid patching init code ;) */
1119	u8		*text;
1120	u8		*text_end;
1121
1122	struct list_head next;
1123};
1124static LIST_HEAD(smp_alt_modules);
1125static bool uniproc_patched = false;	/* protected by text_mutex */
1126
1127void __init_or_module alternatives_smp_module_add(struct module *mod,
1128						  char *name,
1129						  void *locks, void *locks_end,
1130						  void *text,  void *text_end)
1131{
1132	struct smp_alt_module *smp;
1133
1134	mutex_lock(&text_mutex);
1135	if (!uniproc_patched)
1136		goto unlock;
1137
1138	if (num_possible_cpus() == 1)
1139		/* Don't bother remembering, we'll never have to undo it. */
1140		goto smp_unlock;
1141
1142	smp = kzalloc(sizeof(*smp), GFP_KERNEL);
1143	if (NULL == smp)
1144		/* we'll run the (safe but slow) SMP code then ... */
1145		goto unlock;
1146
1147	smp->mod	= mod;
1148	smp->name	= name;
1149	smp->locks	= locks;
1150	smp->locks_end	= locks_end;
1151	smp->text	= text;
1152	smp->text_end	= text_end;
1153	DPRINTK("locks %p -> %p, text %p -> %p, name %s\n",
1154		smp->locks, smp->locks_end,
1155		smp->text, smp->text_end, smp->name);
1156
1157	list_add_tail(&smp->next, &smp_alt_modules);
1158smp_unlock:
1159	alternatives_smp_unlock(locks, locks_end, text, text_end);
1160unlock:
1161	mutex_unlock(&text_mutex);
1162}
1163
1164void __init_or_module alternatives_smp_module_del(struct module *mod)
1165{
1166	struct smp_alt_module *item;
1167
1168	mutex_lock(&text_mutex);
1169	list_for_each_entry(item, &smp_alt_modules, next) {
1170		if (mod != item->mod)
1171			continue;
1172		list_del(&item->next);
1173		kfree(item);
1174		break;
1175	}
1176	mutex_unlock(&text_mutex);
1177}
1178
1179void alternatives_enable_smp(void)
1180{
1181	struct smp_alt_module *mod;
1182
1183	/* Why bother if there are no other CPUs? */
1184	BUG_ON(num_possible_cpus() == 1);
1185
1186	mutex_lock(&text_mutex);
1187
1188	if (uniproc_patched) {
1189		pr_info("switching to SMP code\n");
1190		BUG_ON(num_online_cpus() != 1);
1191		clear_cpu_cap(&boot_cpu_data, X86_FEATURE_UP);
1192		clear_cpu_cap(&cpu_data(0), X86_FEATURE_UP);
1193		list_for_each_entry(mod, &smp_alt_modules, next)
1194			alternatives_smp_lock(mod->locks, mod->locks_end,
1195					      mod->text, mod->text_end);
1196		uniproc_patched = false;
1197	}
1198	mutex_unlock(&text_mutex);
1199}
1200
1201/*
1202 * Return 1 if the address range is reserved for SMP-alternatives.
1203 * Must hold text_mutex.
1204 */
1205int alternatives_text_reserved(void *start, void *end)
1206{
1207	struct smp_alt_module *mod;
1208	const s32 *poff;
1209	u8 *text_start = start;
1210	u8 *text_end = end;
1211
1212	lockdep_assert_held(&text_mutex);
1213
1214	list_for_each_entry(mod, &smp_alt_modules, next) {
1215		if (mod->text > text_end || mod->text_end < text_start)
1216			continue;
1217		for (poff = mod->locks; poff < mod->locks_end; poff++) {
1218			const u8 *ptr = (const u8 *)poff + *poff;
1219
1220			if (text_start <= ptr && text_end > ptr)
1221				return 1;
1222		}
1223	}
1224
1225	return 0;
1226}
1227#endif /* CONFIG_SMP */
1228
1229#ifdef CONFIG_PARAVIRT
1230void __init_or_module apply_paravirt(struct paravirt_patch_site *start,
1231				     struct paravirt_patch_site *end)
1232{
1233	struct paravirt_patch_site *p;
1234	char insn_buff[MAX_PATCH_LEN];
1235
1236	for (p = start; p < end; p++) {
1237		unsigned int used;
1238
1239		BUG_ON(p->len > MAX_PATCH_LEN);
1240		/* prep the buffer with the original instructions */
1241		memcpy(insn_buff, p->instr, p->len);
1242		used = paravirt_patch(p->type, insn_buff, (unsigned long)p->instr, p->len);
1243
1244		BUG_ON(used > p->len);
1245
1246		/* Pad the rest with nops */
1247		add_nops(insn_buff + used, p->len - used);
1248		text_poke_early(p->instr, insn_buff, p->len);
1249	}
1250}
1251extern struct paravirt_patch_site __start_parainstructions[],
1252	__stop_parainstructions[];
1253#endif	/* CONFIG_PARAVIRT */
1254
1255/*
1256 * Self-test for the INT3 based CALL emulation code.
1257 *
1258 * This exercises int3_emulate_call() to make sure INT3 pt_regs are set up
1259 * properly and that there is a stack gap between the INT3 frame and the
1260 * previous context. Without this gap doing a virtual PUSH on the interrupted
1261 * stack would corrupt the INT3 IRET frame.
1262 *
1263 * See entry_{32,64}.S for more details.
1264 */
1265
1266/*
1267 * We define the int3_magic() function in assembly to control the calling
1268 * convention such that we can 'call' it from assembly.
1269 */
1270
1271extern void int3_magic(unsigned int *ptr); /* defined in asm */
1272
1273asm (
1274"	.pushsection	.init.text, \"ax\", @progbits\n"
1275"	.type		int3_magic, @function\n"
1276"int3_magic:\n"
1277	ANNOTATE_NOENDBR
1278"	movl	$1, (%" _ASM_ARG1 ")\n"
1279	ASM_RET
1280"	.size		int3_magic, .-int3_magic\n"
1281"	.popsection\n"
1282);
1283
1284extern void int3_selftest_ip(void); /* defined in asm below */
1285
1286static int __init
1287int3_exception_notify(struct notifier_block *self, unsigned long val, void *data)
1288{
1289	unsigned long selftest = (unsigned long)&int3_selftest_ip;
1290	struct die_args *args = data;
1291	struct pt_regs *regs = args->regs;
1292
1293	OPTIMIZER_HIDE_VAR(selftest);
1294
1295	if (!regs || user_mode(regs))
1296		return NOTIFY_DONE;
1297
1298	if (val != DIE_INT3)
1299		return NOTIFY_DONE;
1300
1301	if (regs->ip - INT3_INSN_SIZE != selftest)
1302		return NOTIFY_DONE;
1303
1304	int3_emulate_call(regs, (unsigned long)&int3_magic);
1305	return NOTIFY_STOP;
1306}
1307
1308/* Must be noinline to ensure uniqueness of int3_selftest_ip. */
1309static noinline void __init int3_selftest(void)
1310{
1311	static __initdata struct notifier_block int3_exception_nb = {
1312		.notifier_call	= int3_exception_notify,
1313		.priority	= INT_MAX-1, /* last */
1314	};
1315	unsigned int val = 0;
1316
1317	BUG_ON(register_die_notifier(&int3_exception_nb));
1318
1319	/*
1320	 * Basically: int3_magic(&val); but really complicated :-)
1321	 *
1322	 * INT3 padded with NOP to CALL_INSN_SIZE. The int3_exception_nb
1323	 * notifier above will emulate CALL for us.
1324	 */
1325	asm volatile ("int3_selftest_ip:\n\t"
1326		      ANNOTATE_NOENDBR
1327		      "    int3; nop; nop; nop; nop\n\t"
1328		      : ASM_CALL_CONSTRAINT
1329		      : __ASM_SEL_RAW(a, D) (&val)
1330		      : "memory");
1331
1332	BUG_ON(val != 1);
1333
1334	unregister_die_notifier(&int3_exception_nb);
1335}
1336
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1337void __init alternative_instructions(void)
1338{
1339	int3_selftest();
1340
1341	/*
1342	 * The patching is not fully atomic, so try to avoid local
1343	 * interruptions that might execute the to be patched code.
1344	 * Other CPUs are not running.
1345	 */
1346	stop_nmi();
1347
1348	/*
1349	 * Don't stop machine check exceptions while patching.
1350	 * MCEs only happen when something got corrupted and in this
1351	 * case we must do something about the corruption.
1352	 * Ignoring it is worse than an unlikely patching race.
1353	 * Also machine checks tend to be broadcast and if one CPU
1354	 * goes into machine check the others follow quickly, so we don't
1355	 * expect a machine check to cause undue problems during to code
1356	 * patching.
1357	 */
1358
1359	/*
1360	 * Paravirt patching and alternative patching can be combined to
1361	 * replace a function call with a short direct code sequence (e.g.
1362	 * by setting a constant return value instead of doing that in an
1363	 * external function).
1364	 * In order to make this work the following sequence is required:
1365	 * 1. set (artificial) features depending on used paravirt
1366	 *    functions which can later influence alternative patching
1367	 * 2. apply paravirt patching (generally replacing an indirect
1368	 *    function call with a direct one)
1369	 * 3. apply alternative patching (e.g. replacing a direct function
1370	 *    call with a custom code sequence)
1371	 * Doing paravirt patching after alternative patching would clobber
1372	 * the optimization of the custom code with a function call again.
1373	 */
1374	paravirt_set_cap();
1375
1376	/*
1377	 * First patch paravirt functions, such that we overwrite the indirect
1378	 * call with the direct call.
1379	 */
1380	apply_paravirt(__parainstructions, __parainstructions_end);
1381
1382	__apply_fineibt(__retpoline_sites, __retpoline_sites_end,
1383			__cfi_sites, __cfi_sites_end, true);
1384
1385	/*
1386	 * Rewrite the retpolines, must be done before alternatives since
1387	 * those can rewrite the retpoline thunks.
1388	 */
1389	apply_retpolines(__retpoline_sites, __retpoline_sites_end);
1390	apply_returns(__return_sites, __return_sites_end);
1391
1392	/*
1393	 * Then patch alternatives, such that those paravirt calls that are in
1394	 * alternatives can be overwritten by their immediate fragments.
1395	 */
1396	apply_alternatives(__alt_instructions, __alt_instructions_end);
1397
1398	/*
1399	 * Now all calls are established. Apply the call thunks if
1400	 * required.
1401	 */
1402	callthunks_patch_builtin_calls();
1403
1404	apply_ibt_endbr(__ibt_endbr_seal, __ibt_endbr_seal_end);
 
 
 
1405
1406#ifdef CONFIG_SMP
1407	/* Patch to UP if other cpus not imminent. */
1408	if (!noreplace_smp && (num_present_cpus() == 1 || setup_max_cpus <= 1)) {
1409		uniproc_patched = true;
1410		alternatives_smp_module_add(NULL, "core kernel",
1411					    __smp_locks, __smp_locks_end,
1412					    _text, _etext);
1413	}
1414
1415	if (!uniproc_patched || num_possible_cpus() == 1) {
1416		free_init_pages("SMP alternatives",
1417				(unsigned long)__smp_locks,
1418				(unsigned long)__smp_locks_end);
1419	}
1420#endif
1421
1422	restart_nmi();
1423	alternatives_patched = 1;
 
 
1424}
1425
1426/**
1427 * text_poke_early - Update instructions on a live kernel at boot time
1428 * @addr: address to modify
1429 * @opcode: source of the copy
1430 * @len: length to copy
1431 *
1432 * When you use this code to patch more than one byte of an instruction
1433 * you need to make sure that other CPUs cannot execute this code in parallel.
1434 * Also no thread must be currently preempted in the middle of these
1435 * instructions. And on the local CPU you need to be protected against NMI or
1436 * MCE handlers seeing an inconsistent instruction while you patch.
1437 */
1438void __init_or_module text_poke_early(void *addr, const void *opcode,
1439				      size_t len)
1440{
1441	unsigned long flags;
1442
1443	if (boot_cpu_has(X86_FEATURE_NX) &&
1444	    is_module_text_address((unsigned long)addr)) {
1445		/*
1446		 * Modules text is marked initially as non-executable, so the
1447		 * code cannot be running and speculative code-fetches are
1448		 * prevented. Just change the code.
1449		 */
1450		memcpy(addr, opcode, len);
1451	} else {
1452		local_irq_save(flags);
1453		memcpy(addr, opcode, len);
1454		local_irq_restore(flags);
1455		sync_core();
 
1456
1457		/*
1458		 * Could also do a CLFLUSH here to speed up CPU recovery; but
1459		 * that causes hangs on some VIA CPUs.
1460		 */
1461	}
1462}
1463
1464typedef struct {
1465	struct mm_struct *mm;
1466} temp_mm_state_t;
1467
1468/*
1469 * Using a temporary mm allows to set temporary mappings that are not accessible
1470 * by other CPUs. Such mappings are needed to perform sensitive memory writes
1471 * that override the kernel memory protections (e.g., W^X), without exposing the
1472 * temporary page-table mappings that are required for these write operations to
1473 * other CPUs. Using a temporary mm also allows to avoid TLB shootdowns when the
1474 * mapping is torn down.
1475 *
1476 * Context: The temporary mm needs to be used exclusively by a single core. To
1477 *          harden security IRQs must be disabled while the temporary mm is
1478 *          loaded, thereby preventing interrupt handler bugs from overriding
1479 *          the kernel memory protection.
1480 */
1481static inline temp_mm_state_t use_temporary_mm(struct mm_struct *mm)
1482{
1483	temp_mm_state_t temp_state;
1484
1485	lockdep_assert_irqs_disabled();
1486
1487	/*
1488	 * Make sure not to be in TLB lazy mode, as otherwise we'll end up
1489	 * with a stale address space WITHOUT being in lazy mode after
1490	 * restoring the previous mm.
1491	 */
1492	if (this_cpu_read(cpu_tlbstate_shared.is_lazy))
1493		leave_mm(smp_processor_id());
1494
1495	temp_state.mm = this_cpu_read(cpu_tlbstate.loaded_mm);
1496	switch_mm_irqs_off(NULL, mm, current);
1497
1498	/*
1499	 * If breakpoints are enabled, disable them while the temporary mm is
1500	 * used. Userspace might set up watchpoints on addresses that are used
1501	 * in the temporary mm, which would lead to wrong signals being sent or
1502	 * crashes.
1503	 *
1504	 * Note that breakpoints are not disabled selectively, which also causes
1505	 * kernel breakpoints (e.g., perf's) to be disabled. This might be
1506	 * undesirable, but still seems reasonable as the code that runs in the
1507	 * temporary mm should be short.
1508	 */
1509	if (hw_breakpoint_active())
1510		hw_breakpoint_disable();
1511
1512	return temp_state;
1513}
1514
1515static inline void unuse_temporary_mm(temp_mm_state_t prev_state)
1516{
1517	lockdep_assert_irqs_disabled();
1518	switch_mm_irqs_off(NULL, prev_state.mm, current);
1519
1520	/*
1521	 * Restore the breakpoints if they were disabled before the temporary mm
1522	 * was loaded.
1523	 */
1524	if (hw_breakpoint_active())
1525		hw_breakpoint_restore();
1526}
1527
1528__ro_after_init struct mm_struct *poking_mm;
1529__ro_after_init unsigned long poking_addr;
1530
1531static void text_poke_memcpy(void *dst, const void *src, size_t len)
1532{
1533	memcpy(dst, src, len);
1534}
1535
1536static void text_poke_memset(void *dst, const void *src, size_t len)
1537{
1538	int c = *(const int *)src;
1539
1540	memset(dst, c, len);
1541}
1542
1543typedef void text_poke_f(void *dst, const void *src, size_t len);
1544
1545static void *__text_poke(text_poke_f func, void *addr, const void *src, size_t len)
1546{
1547	bool cross_page_boundary = offset_in_page(addr) + len > PAGE_SIZE;
1548	struct page *pages[2] = {NULL};
1549	temp_mm_state_t prev;
1550	unsigned long flags;
1551	pte_t pte, *ptep;
1552	spinlock_t *ptl;
1553	pgprot_t pgprot;
1554
1555	/*
1556	 * While boot memory allocator is running we cannot use struct pages as
1557	 * they are not yet initialized. There is no way to recover.
1558	 */
1559	BUG_ON(!after_bootmem);
1560
1561	if (!core_kernel_text((unsigned long)addr)) {
1562		pages[0] = vmalloc_to_page(addr);
1563		if (cross_page_boundary)
1564			pages[1] = vmalloc_to_page(addr + PAGE_SIZE);
1565	} else {
1566		pages[0] = virt_to_page(addr);
1567		WARN_ON(!PageReserved(pages[0]));
1568		if (cross_page_boundary)
1569			pages[1] = virt_to_page(addr + PAGE_SIZE);
1570	}
1571	/*
1572	 * If something went wrong, crash and burn since recovery paths are not
1573	 * implemented.
1574	 */
1575	BUG_ON(!pages[0] || (cross_page_boundary && !pages[1]));
1576
1577	/*
1578	 * Map the page without the global bit, as TLB flushing is done with
1579	 * flush_tlb_mm_range(), which is intended for non-global PTEs.
1580	 */
1581	pgprot = __pgprot(pgprot_val(PAGE_KERNEL) & ~_PAGE_GLOBAL);
1582
1583	/*
1584	 * The lock is not really needed, but this allows to avoid open-coding.
1585	 */
1586	ptep = get_locked_pte(poking_mm, poking_addr, &ptl);
1587
1588	/*
1589	 * This must not fail; preallocated in poking_init().
1590	 */
1591	VM_BUG_ON(!ptep);
1592
1593	local_irq_save(flags);
1594
1595	pte = mk_pte(pages[0], pgprot);
1596	set_pte_at(poking_mm, poking_addr, ptep, pte);
1597
1598	if (cross_page_boundary) {
1599		pte = mk_pte(pages[1], pgprot);
1600		set_pte_at(poking_mm, poking_addr + PAGE_SIZE, ptep + 1, pte);
1601	}
1602
1603	/*
1604	 * Loading the temporary mm behaves as a compiler barrier, which
1605	 * guarantees that the PTE will be set at the time memcpy() is done.
1606	 */
1607	prev = use_temporary_mm(poking_mm);
1608
1609	kasan_disable_current();
1610	func((u8 *)poking_addr + offset_in_page(addr), src, len);
1611	kasan_enable_current();
1612
1613	/*
1614	 * Ensure that the PTE is only cleared after the instructions of memcpy
1615	 * were issued by using a compiler barrier.
1616	 */
1617	barrier();
1618
1619	pte_clear(poking_mm, poking_addr, ptep);
1620	if (cross_page_boundary)
1621		pte_clear(poking_mm, poking_addr + PAGE_SIZE, ptep + 1);
1622
1623	/*
1624	 * Loading the previous page-table hierarchy requires a serializing
1625	 * instruction that already allows the core to see the updated version.
1626	 * Xen-PV is assumed to serialize execution in a similar manner.
1627	 */
1628	unuse_temporary_mm(prev);
1629
1630	/*
1631	 * Flushing the TLB might involve IPIs, which would require enabled
1632	 * IRQs, but not if the mm is not used, as it is in this point.
1633	 */
1634	flush_tlb_mm_range(poking_mm, poking_addr, poking_addr +
1635			   (cross_page_boundary ? 2 : 1) * PAGE_SIZE,
1636			   PAGE_SHIFT, false);
1637
1638	if (func == text_poke_memcpy) {
1639		/*
1640		 * If the text does not match what we just wrote then something is
1641		 * fundamentally screwy; there's nothing we can really do about that.
1642		 */
1643		BUG_ON(memcmp(addr, src, len));
1644	}
1645
1646	local_irq_restore(flags);
1647	pte_unmap_unlock(ptep, ptl);
1648	return addr;
1649}
1650
1651/**
1652 * text_poke - Update instructions on a live kernel
1653 * @addr: address to modify
1654 * @opcode: source of the copy
1655 * @len: length to copy
1656 *
1657 * Only atomic text poke/set should be allowed when not doing early patching.
1658 * It means the size must be writable atomically and the address must be aligned
1659 * in a way that permits an atomic write. It also makes sure we fit on a single
1660 * page.
1661 *
1662 * Note that the caller must ensure that if the modified code is part of a
1663 * module, the module would not be removed during poking. This can be achieved
1664 * by registering a module notifier, and ordering module removal and patching
1665 * trough a mutex.
1666 */
1667void *text_poke(void *addr, const void *opcode, size_t len)
1668{
1669	lockdep_assert_held(&text_mutex);
1670
1671	return __text_poke(text_poke_memcpy, addr, opcode, len);
1672}
1673
1674/**
1675 * text_poke_kgdb - Update instructions on a live kernel by kgdb
1676 * @addr: address to modify
1677 * @opcode: source of the copy
1678 * @len: length to copy
1679 *
1680 * Only atomic text poke/set should be allowed when not doing early patching.
1681 * It means the size must be writable atomically and the address must be aligned
1682 * in a way that permits an atomic write. It also makes sure we fit on a single
1683 * page.
1684 *
1685 * Context: should only be used by kgdb, which ensures no other core is running,
1686 *	    despite the fact it does not hold the text_mutex.
1687 */
1688void *text_poke_kgdb(void *addr, const void *opcode, size_t len)
1689{
1690	return __text_poke(text_poke_memcpy, addr, opcode, len);
1691}
1692
1693void *text_poke_copy_locked(void *addr, const void *opcode, size_t len,
1694			    bool core_ok)
1695{
1696	unsigned long start = (unsigned long)addr;
1697	size_t patched = 0;
1698
1699	if (WARN_ON_ONCE(!core_ok && core_kernel_text(start)))
1700		return NULL;
1701
1702	while (patched < len) {
1703		unsigned long ptr = start + patched;
1704		size_t s;
1705
1706		s = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(ptr), len - patched);
1707
1708		__text_poke(text_poke_memcpy, (void *)ptr, opcode + patched, s);
1709		patched += s;
1710	}
1711	return addr;
1712}
1713
1714/**
1715 * text_poke_copy - Copy instructions into (an unused part of) RX memory
1716 * @addr: address to modify
1717 * @opcode: source of the copy
1718 * @len: length to copy, could be more than 2x PAGE_SIZE
1719 *
1720 * Not safe against concurrent execution; useful for JITs to dump
1721 * new code blocks into unused regions of RX memory. Can be used in
1722 * conjunction with synchronize_rcu_tasks() to wait for existing
1723 * execution to quiesce after having made sure no existing functions
1724 * pointers are live.
1725 */
1726void *text_poke_copy(void *addr, const void *opcode, size_t len)
1727{
1728	mutex_lock(&text_mutex);
1729	addr = text_poke_copy_locked(addr, opcode, len, false);
1730	mutex_unlock(&text_mutex);
1731	return addr;
1732}
1733
1734/**
1735 * text_poke_set - memset into (an unused part of) RX memory
1736 * @addr: address to modify
1737 * @c: the byte to fill the area with
1738 * @len: length to copy, could be more than 2x PAGE_SIZE
1739 *
1740 * This is useful to overwrite unused regions of RX memory with illegal
1741 * instructions.
1742 */
1743void *text_poke_set(void *addr, int c, size_t len)
1744{
1745	unsigned long start = (unsigned long)addr;
1746	size_t patched = 0;
1747
1748	if (WARN_ON_ONCE(core_kernel_text(start)))
1749		return NULL;
1750
1751	mutex_lock(&text_mutex);
1752	while (patched < len) {
1753		unsigned long ptr = start + patched;
1754		size_t s;
1755
1756		s = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(ptr), len - patched);
1757
1758		__text_poke(text_poke_memset, (void *)ptr, (void *)&c, s);
1759		patched += s;
1760	}
1761	mutex_unlock(&text_mutex);
1762	return addr;
1763}
1764
1765static void do_sync_core(void *info)
1766{
1767	sync_core();
1768}
1769
1770void text_poke_sync(void)
1771{
1772	on_each_cpu(do_sync_core, NULL, 1);
1773}
1774
 
 
 
 
 
1775struct text_poke_loc {
1776	/* addr := _stext + rel_addr */
1777	s32 rel_addr;
1778	s32 disp;
1779	u8 len;
1780	u8 opcode;
1781	const u8 text[POKE_MAX_OPCODE_SIZE];
1782	/* see text_poke_bp_batch() */
1783	u8 old;
1784};
1785
1786struct bp_patching_desc {
1787	struct text_poke_loc *vec;
1788	int nr_entries;
1789	atomic_t refs;
1790};
1791
1792static struct bp_patching_desc bp_desc;
1793
1794static __always_inline
1795struct bp_patching_desc *try_get_desc(void)
1796{
1797	struct bp_patching_desc *desc = &bp_desc;
1798
1799	if (!arch_atomic_inc_not_zero(&desc->refs))
1800		return NULL;
1801
1802	return desc;
1803}
1804
1805static __always_inline void put_desc(void)
1806{
1807	struct bp_patching_desc *desc = &bp_desc;
1808
1809	smp_mb__before_atomic();
1810	arch_atomic_dec(&desc->refs);
1811}
1812
1813static __always_inline void *text_poke_addr(struct text_poke_loc *tp)
1814{
1815	return _stext + tp->rel_addr;
1816}
1817
1818static __always_inline int patch_cmp(const void *key, const void *elt)
1819{
1820	struct text_poke_loc *tp = (struct text_poke_loc *) elt;
1821
1822	if (key < text_poke_addr(tp))
1823		return -1;
1824	if (key > text_poke_addr(tp))
1825		return 1;
1826	return 0;
1827}
1828
1829noinstr int poke_int3_handler(struct pt_regs *regs)
1830{
1831	struct bp_patching_desc *desc;
1832	struct text_poke_loc *tp;
1833	int ret = 0;
1834	void *ip;
1835
1836	if (user_mode(regs))
1837		return 0;
1838
1839	/*
1840	 * Having observed our INT3 instruction, we now must observe
1841	 * bp_desc with non-zero refcount:
1842	 *
1843	 *	bp_desc.refs = 1		INT3
1844	 *	WMB				RMB
1845	 *	write INT3			if (bp_desc.refs != 0)
1846	 */
1847	smp_rmb();
1848
1849	desc = try_get_desc();
1850	if (!desc)
1851		return 0;
1852
1853	/*
1854	 * Discount the INT3. See text_poke_bp_batch().
1855	 */
1856	ip = (void *) regs->ip - INT3_INSN_SIZE;
1857
1858	/*
1859	 * Skip the binary search if there is a single member in the vector.
1860	 */
1861	if (unlikely(desc->nr_entries > 1)) {
1862		tp = __inline_bsearch(ip, desc->vec, desc->nr_entries,
1863				      sizeof(struct text_poke_loc),
1864				      patch_cmp);
1865		if (!tp)
1866			goto out_put;
1867	} else {
1868		tp = desc->vec;
1869		if (text_poke_addr(tp) != ip)
1870			goto out_put;
1871	}
1872
1873	ip += tp->len;
1874
1875	switch (tp->opcode) {
1876	case INT3_INSN_OPCODE:
1877		/*
1878		 * Someone poked an explicit INT3, they'll want to handle it,
1879		 * do not consume.
1880		 */
1881		goto out_put;
1882
1883	case RET_INSN_OPCODE:
1884		int3_emulate_ret(regs);
1885		break;
1886
1887	case CALL_INSN_OPCODE:
1888		int3_emulate_call(regs, (long)ip + tp->disp);
1889		break;
1890
1891	case JMP32_INSN_OPCODE:
1892	case JMP8_INSN_OPCODE:
1893		int3_emulate_jmp(regs, (long)ip + tp->disp);
1894		break;
1895
 
 
 
 
1896	default:
1897		BUG();
1898	}
1899
1900	ret = 1;
1901
1902out_put:
1903	put_desc();
1904	return ret;
1905}
1906
1907#define TP_VEC_MAX (PAGE_SIZE / sizeof(struct text_poke_loc))
1908static struct text_poke_loc tp_vec[TP_VEC_MAX];
1909static int tp_vec_nr;
1910
1911/**
1912 * text_poke_bp_batch() -- update instructions on live kernel on SMP
1913 * @tp:			vector of instructions to patch
1914 * @nr_entries:		number of entries in the vector
1915 *
1916 * Modify multi-byte instruction by using int3 breakpoint on SMP.
1917 * We completely avoid stop_machine() here, and achieve the
1918 * synchronization using int3 breakpoint.
1919 *
1920 * The way it is done:
1921 *	- For each entry in the vector:
1922 *		- add a int3 trap to the address that will be patched
1923 *	- sync cores
1924 *	- For each entry in the vector:
1925 *		- update all but the first byte of the patched range
1926 *	- sync cores
1927 *	- For each entry in the vector:
1928 *		- replace the first byte (int3) by the first byte of
1929 *		  replacing opcode
1930 *	- sync cores
1931 */
1932static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries)
1933{
1934	unsigned char int3 = INT3_INSN_OPCODE;
1935	unsigned int i;
1936	int do_sync;
1937
1938	lockdep_assert_held(&text_mutex);
1939
1940	bp_desc.vec = tp;
1941	bp_desc.nr_entries = nr_entries;
1942
1943	/*
1944	 * Corresponds to the implicit memory barrier in try_get_desc() to
1945	 * ensure reading a non-zero refcount provides up to date bp_desc data.
1946	 */
1947	atomic_set_release(&bp_desc.refs, 1);
1948
1949	/*
 
 
 
 
 
 
 
 
 
 
1950	 * Corresponding read barrier in int3 notifier for making sure the
1951	 * nr_entries and handler are correctly ordered wrt. patching.
1952	 */
1953	smp_wmb();
1954
1955	/*
1956	 * First step: add a int3 trap to the address that will be patched.
1957	 */
1958	for (i = 0; i < nr_entries; i++) {
1959		tp[i].old = *(u8 *)text_poke_addr(&tp[i]);
1960		text_poke(text_poke_addr(&tp[i]), &int3, INT3_INSN_SIZE);
1961	}
1962
1963	text_poke_sync();
1964
1965	/*
1966	 * Second step: update all but the first byte of the patched range.
1967	 */
1968	for (do_sync = 0, i = 0; i < nr_entries; i++) {
1969		u8 old[POKE_MAX_OPCODE_SIZE] = { tp[i].old, };
 
 
1970		int len = tp[i].len;
1971
1972		if (len - INT3_INSN_SIZE > 0) {
1973			memcpy(old + INT3_INSN_SIZE,
1974			       text_poke_addr(&tp[i]) + INT3_INSN_SIZE,
1975			       len - INT3_INSN_SIZE);
 
 
 
 
 
 
 
1976			text_poke(text_poke_addr(&tp[i]) + INT3_INSN_SIZE,
1977				  (const char *)tp[i].text + INT3_INSN_SIZE,
1978				  len - INT3_INSN_SIZE);
 
1979			do_sync++;
1980		}
1981
1982		/*
1983		 * Emit a perf event to record the text poke, primarily to
1984		 * support Intel PT decoding which must walk the executable code
1985		 * to reconstruct the trace. The flow up to here is:
1986		 *   - write INT3 byte
1987		 *   - IPI-SYNC
1988		 *   - write instruction tail
1989		 * At this point the actual control flow will be through the
1990		 * INT3 and handler and not hit the old or new instruction.
1991		 * Intel PT outputs FUP/TIP packets for the INT3, so the flow
1992		 * can still be decoded. Subsequently:
1993		 *   - emit RECORD_TEXT_POKE with the new instruction
1994		 *   - IPI-SYNC
1995		 *   - write first byte
1996		 *   - IPI-SYNC
1997		 * So before the text poke event timestamp, the decoder will see
1998		 * either the old instruction flow or FUP/TIP of INT3. After the
1999		 * text poke event timestamp, the decoder will see either the
2000		 * new instruction flow or FUP/TIP of INT3. Thus decoders can
2001		 * use the timestamp as the point at which to modify the
2002		 * executable code.
2003		 * The old instruction is recorded so that the event can be
2004		 * processed forwards or backwards.
2005		 */
2006		perf_event_text_poke(text_poke_addr(&tp[i]), old, len,
2007				     tp[i].text, len);
2008	}
2009
2010	if (do_sync) {
2011		/*
2012		 * According to Intel, this core syncing is very likely
2013		 * not necessary and we'd be safe even without it. But
2014		 * better safe than sorry (plus there's not only Intel).
2015		 */
2016		text_poke_sync();
2017	}
2018
2019	/*
2020	 * Third step: replace the first byte (int3) by the first byte of
2021	 * replacing opcode.
2022	 */
2023	for (do_sync = 0, i = 0; i < nr_entries; i++) {
2024		if (tp[i].text[0] == INT3_INSN_OPCODE)
 
 
 
 
 
2025			continue;
2026
2027		text_poke(text_poke_addr(&tp[i]), tp[i].text, INT3_INSN_SIZE);
2028		do_sync++;
2029	}
2030
2031	if (do_sync)
2032		text_poke_sync();
2033
2034	/*
2035	 * Remove and wait for refs to be zero.
2036	 */
2037	if (!atomic_dec_and_test(&bp_desc.refs))
2038		atomic_cond_read_acquire(&bp_desc.refs, !VAL);
2039}
2040
2041static void text_poke_loc_init(struct text_poke_loc *tp, void *addr,
2042			       const void *opcode, size_t len, const void *emulate)
2043{
2044	struct insn insn;
2045	int ret, i;
2046
2047	memcpy((void *)tp->text, opcode, len);
 
 
2048	if (!emulate)
2049		emulate = opcode;
2050
2051	ret = insn_decode_kernel(&insn, emulate);
2052	BUG_ON(ret < 0);
2053
2054	tp->rel_addr = addr - (void *)_stext;
2055	tp->len = len;
2056	tp->opcode = insn.opcode.bytes[0];
2057
 
 
 
 
 
 
 
2058	switch (tp->opcode) {
2059	case RET_INSN_OPCODE:
2060	case JMP32_INSN_OPCODE:
2061	case JMP8_INSN_OPCODE:
2062		/*
2063		 * Control flow instructions without implied execution of the
2064		 * next instruction can be padded with INT3.
2065		 */
2066		for (i = insn.length; i < len; i++)
2067			BUG_ON(tp->text[i] != INT3_INSN_OPCODE);
2068		break;
2069
2070	default:
2071		BUG_ON(len != insn.length);
2072	}
2073
2074
2075	switch (tp->opcode) {
2076	case INT3_INSN_OPCODE:
2077	case RET_INSN_OPCODE:
2078		break;
2079
2080	case CALL_INSN_OPCODE:
2081	case JMP32_INSN_OPCODE:
2082	case JMP8_INSN_OPCODE:
 
2083		tp->disp = insn.immediate.value;
2084		break;
2085
2086	default: /* assume NOP */
2087		switch (len) {
2088		case 2: /* NOP2 -- emulate as JMP8+0 */
2089			BUG_ON(memcmp(emulate, x86_nops[len], len));
2090			tp->opcode = JMP8_INSN_OPCODE;
2091			tp->disp = 0;
2092			break;
2093
2094		case 5: /* NOP5 -- emulate as JMP32+0 */
2095			BUG_ON(memcmp(emulate, x86_nops[len], len));
2096			tp->opcode = JMP32_INSN_OPCODE;
2097			tp->disp = 0;
2098			break;
2099
2100		default: /* unknown instruction */
2101			BUG();
2102		}
2103		break;
2104	}
2105}
2106
2107/*
2108 * We hard rely on the tp_vec being ordered; ensure this is so by flushing
2109 * early if needed.
2110 */
2111static bool tp_order_fail(void *addr)
2112{
2113	struct text_poke_loc *tp;
2114
2115	if (!tp_vec_nr)
2116		return false;
2117
2118	if (!addr) /* force */
2119		return true;
2120
2121	tp = &tp_vec[tp_vec_nr - 1];
2122	if ((unsigned long)text_poke_addr(tp) > (unsigned long)addr)
2123		return true;
2124
2125	return false;
2126}
2127
2128static void text_poke_flush(void *addr)
2129{
2130	if (tp_vec_nr == TP_VEC_MAX || tp_order_fail(addr)) {
2131		text_poke_bp_batch(tp_vec, tp_vec_nr);
2132		tp_vec_nr = 0;
2133	}
2134}
2135
2136void text_poke_finish(void)
2137{
2138	text_poke_flush(NULL);
2139}
2140
2141void __ref text_poke_queue(void *addr, const void *opcode, size_t len, const void *emulate)
2142{
2143	struct text_poke_loc *tp;
2144
2145	text_poke_flush(addr);
2146
2147	tp = &tp_vec[tp_vec_nr++];
2148	text_poke_loc_init(tp, addr, opcode, len, emulate);
2149}
2150
2151/**
2152 * text_poke_bp() -- update instructions on live kernel on SMP
2153 * @addr:	address to patch
2154 * @opcode:	opcode of new instruction
2155 * @len:	length to copy
2156 * @emulate:	instruction to be emulated
2157 *
2158 * Update a single instruction with the vector in the stack, avoiding
2159 * dynamically allocated memory. This function should be used when it is
2160 * not possible to allocate memory.
2161 */
2162void __ref text_poke_bp(void *addr, const void *opcode, size_t len, const void *emulate)
2163{
2164	struct text_poke_loc tp;
2165
2166	text_poke_loc_init(&tp, addr, opcode, len, emulate);
2167	text_poke_bp_batch(&tp, 1);
2168}