summaryrefslogtreecommitdiff
path: root/arch/x86/include/asm/alternative.h
blob: ba99ef75f56cbe3ef97c8f7f9fc616884f3802af (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_ALTERNATIVE_H
#define _ASM_X86_ALTERNATIVE_H

#include <linux/types.h>
#include <linux/stringify.h>
#include <asm/asm.h>

#define ALT_FLAGS_SHIFT		16

#define ALT_FLAG_NOT		(1 << 0)
#define ALT_NOT(feature)	((ALT_FLAG_NOT << ALT_FLAGS_SHIFT) | (feature))
#define ALT_FLAG_DIRECT_CALL	(1 << 1)
#define ALT_DIRECT_CALL(feature) ((ALT_FLAG_DIRECT_CALL << ALT_FLAGS_SHIFT) | (feature))
#define ALT_CALL_ALWAYS		ALT_DIRECT_CALL(X86_FEATURE_ALWAYS)

#ifndef __ASSEMBLY__

#include <linux/stddef.h>

/*
 * Alternative inline assembly for SMP.
 *
 * The LOCK_PREFIX macro defined here replaces the LOCK and
 * LOCK_PREFIX macros used everywhere in the source tree.
 *
 * SMP alternatives use the same data structures as the other
 * alternatives and the X86_FEATURE_UP flag to indicate the case of a
 * UP system running a SMP kernel.  The existing apply_alternatives()
 * works fine for patching a SMP kernel for UP.
 *
 * The SMP alternative tables can be kept after boot and contain both
 * UP and SMP versions of the instructions to allow switching back to
 * SMP at runtime, when hotplugging in a new CPU, which is especially
 * useful in virtualized environments.
 *
 * The very common lock prefix is handled as special case in a
 * separate table which is a pure address list without replacement ptr
 * and size information.  That keeps the table sizes small.
 */

#ifdef CONFIG_SMP
#define LOCK_PREFIX_HERE \
		".pushsection .smp_locks,\"a\"\n"	\
		".balign 4\n"				\
		".long 671f - .\n" /* offset */		\
		".popsection\n"				\
		"671:"

#define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; "

#else /* ! CONFIG_SMP */
#define LOCK_PREFIX_HERE ""
#define LOCK_PREFIX ""
#endif

/*
 * objtool annotation to ignore the alternatives and only consider the original
 * instruction(s).
 */
#define ANNOTATE_IGNORE_ALTERNATIVE				\
	"999:\n\t"						\
	".pushsection .discard.ignore_alts\n\t"			\
	".long 999b\n\t"					\
	".popsection\n\t"

/*
 * The patching flags are part of the upper bits of the @ft_flags parameter when
 * specifying them. The split is currently like this:
 *
 * [31... flags ...16][15... CPUID feature bit ...0]
 *
 * but since this is all hidden in the macros argument being split, those fields can be
 * extended in the future to fit in a u64 or however the need arises.
 */
struct alt_instr {
	s32 instr_offset;	/* original instruction */
	s32 repl_offset;	/* offset to replacement instruction */

	union {
		struct {
			u32 cpuid: 16;	/* CPUID bit set for replacement */
			u32 flags: 16;	/* patching control flags */
		};
		u32 ft_flags;
	};

	u8  instrlen;		/* length of original instruction */
	u8  replacementlen;	/* length of new instruction */
} __packed;

extern struct alt_instr __alt_instructions[], __alt_instructions_end[];

/*
 * Debug flag that can be tested to see whether alternative
 * instructions were patched in already:
 */
extern int alternatives_patched;

extern void alternative_instructions(void);
extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
extern void apply_retpolines(s32 *start, s32 *end);
extern void apply_returns(s32 *start, s32 *end);
extern void apply_seal_endbr(s32 *start, s32 *end);
extern void apply_fineibt(s32 *start_retpoline, s32 *end_retpoine,
			  s32 *start_cfi, s32 *end_cfi);

struct module;

struct callthunk_sites {
	s32				*call_start, *call_end;
	struct alt_instr		*alt_start, *alt_end;
};

#ifdef CONFIG_CALL_THUNKS
extern void callthunks_patch_builtin_calls(void);
extern void callthunks_patch_module_calls(struct callthunk_sites *sites,
					  struct module *mod);
extern void *callthunks_translate_call_dest(void *dest);
extern int x86_call_depth_emit_accounting(u8 **pprog, void *func, void *ip);
#else
static __always_inline void callthunks_patch_builtin_calls(void) {}
static __always_inline void
callthunks_patch_module_calls(struct callthunk_sites *sites,
			      struct module *mod) {}
static __always_inline void *callthunks_translate_call_dest(void *dest)
{
	return dest;
}
static __always_inline int x86_call_depth_emit_accounting(u8 **pprog,
							  void *func, void *ip)
{
	return 0;
}
#endif

#ifdef CONFIG_SMP
extern void alternatives_smp_module_add(struct module *mod, char *name,
					void *locks, void *locks_end,
					void *text, void *text_end);
extern void alternatives_smp_module_del(struct module *mod);
extern void alternatives_enable_smp(void);
extern int alternatives_text_reserved(void *start, void *end);
extern bool skip_smp_alternatives;
#else
static inline void alternatives_smp_module_add(struct module *mod, char *name,
					       void *locks, void *locks_end,
					       void *text, void *text_end) {}
static inline void alternatives_smp_module_del(struct module *mod) {}
static inline void alternatives_enable_smp(void) {}
static inline int alternatives_text_reserved(void *start, void *end)
{
	return 0;
}
#endif	/* CONFIG_SMP */

#define ALT_CALL_INSTR		"call BUG_func"

#define b_replacement(num)	"664"#num
#define e_replacement(num)	"665"#num

#define alt_end_marker		"663"
#define alt_slen		"662b-661b"
#define alt_total_slen		alt_end_marker"b-661b"
#define alt_rlen(num)		e_replacement(num)"f-"b_replacement(num)"f"

#define OLDINSTR(oldinstr, num)						\
	"# ALT: oldnstr\n"						\
	"661:\n\t" oldinstr "\n662:\n"					\
	"# ALT: padding\n"						\
	".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * "		\
		"((" alt_rlen(num) ")-(" alt_slen ")),0x90\n"		\
	alt_end_marker ":\n"

/*
 * gas compatible max based on the idea from:
 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
 *
 * The additional "-" is needed because gas uses a "true" value of -1.
 */
#define alt_max_short(a, b)	"((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))"

/*
 * Pad the second replacement alternative with additional NOPs if it is
 * additionally longer than the first replacement alternative.
 */
#define OLDINSTR_2(oldinstr, num1, num2) \
	"# ALT: oldinstr2\n"									\
	"661:\n\t" oldinstr "\n662:\n"								\
	"# ALT: padding2\n"									\
	".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * "	\
		"(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n"	\
	alt_end_marker ":\n"

#define OLDINSTR_3(oldinsn, n1, n2, n3)								\
	"# ALT: oldinstr3\n"									\
	"661:\n\t" oldinsn "\n662:\n"								\
	"# ALT: padding3\n"									\
	".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3))	\
		" - (" alt_slen ")) > 0) * "							\
		"(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3))	\
		" - (" alt_slen ")), 0x90\n"							\
	alt_end_marker ":\n"

#define ALTINSTR_ENTRY(ft_flags, num)					      \
	" .long 661b - .\n"				/* label           */ \
	" .long " b_replacement(num)"f - .\n"		/* new instruction */ \
	" .4byte " __stringify(ft_flags) "\n"		/* feature + flags */ \
	" .byte " alt_total_slen "\n"			/* source len      */ \
	" .byte " alt_rlen(num) "\n"			/* replacement len */

#define ALTINSTR_REPLACEMENT(newinstr, num)		/* replacement */	\
	"# ALT: replacement " #num "\n"						\
	b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n"

/* alternative assembly primitive: */
#define ALTERNATIVE(oldinstr, newinstr, ft_flags)			\
	OLDINSTR(oldinstr, 1)						\
	".pushsection .altinstructions,\"a\"\n"				\
	ALTINSTR_ENTRY(ft_flags, 1)					\
	".popsection\n"							\
	".pushsection .altinstr_replacement, \"ax\"\n"			\
	ALTINSTR_REPLACEMENT(newinstr, 1)				\
	".popsection\n"

#define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
	OLDINSTR_2(oldinstr, 1, 2)					\
	".pushsection .altinstructions,\"a\"\n"				\
	ALTINSTR_ENTRY(ft_flags1, 1)					\
	ALTINSTR_ENTRY(ft_flags2, 2)					\
	".popsection\n"							\
	".pushsection .altinstr_replacement, \"ax\"\n"			\
	ALTINSTR_REPLACEMENT(newinstr1, 1)				\
	ALTINSTR_REPLACEMENT(newinstr2, 2)				\
	".popsection\n"

/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
#define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
	ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS,	\
		      newinstr_yes, ft_flags)

#define ALTERNATIVE_3(oldinsn, newinsn1, ft_flags1, newinsn2, ft_flags2, \
			newinsn3, ft_flags3)				\
	OLDINSTR_3(oldinsn, 1, 2, 3)					\
	".pushsection .altinstructions,\"a\"\n"				\
	ALTINSTR_ENTRY(ft_flags1, 1)					\
	ALTINSTR_ENTRY(ft_flags2, 2)					\
	ALTINSTR_ENTRY(ft_flags3, 3)					\
	".popsection\n"							\
	".pushsection .altinstr_replacement, \"ax\"\n"			\
	ALTINSTR_REPLACEMENT(newinsn1, 1)				\
	ALTINSTR_REPLACEMENT(newinsn2, 2)				\
	ALTINSTR_REPLACEMENT(newinsn3, 3)				\
	".popsection\n"

/*
 * Alternative instructions for different CPU types or capabilities.
 *
 * This allows to use optimized instructions even on generic binary
 * kernels.
 *
 * length of oldinstr must be longer or equal the length of newinstr
 * It can be padded with nops as needed.
 *
 * For non barrier like inlines please define new variants
 * without volatile and memory clobber.
 */
#define alternative(oldinstr, newinstr, ft_flags)			\
	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")

#define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
	asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")

#define alternative_ternary(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
	asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) ::: "memory")

/*
 * Alternative inline assembly with input.
 *
 * Peculiarities:
 * No memory clobber here.
 * Argument numbers start with 1.
 * Leaving an unused argument 0 to keep API compatibility.
 */
#define alternative_input(oldinstr, newinstr, ft_flags, input...)	\
	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags)	\
		: : "i" (0), ## input)

/* Like alternative_input, but with a single output argument */
#define alternative_io(oldinstr, newinstr, ft_flags, output, input...)	\
	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags)	\
		: output : "i" (0), ## input)

/* Like alternative_io, but for replacing a direct call with another one. */
#define alternative_call(oldfunc, newfunc, ft_flags, output, input...)	\
	asm_inline volatile (ALTERNATIVE("call %c[old]", "call %c[new]", ft_flags) \
		: output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)

/*
 * Like alternative_call, but there are two features and respective functions.
 * If CPU has feature2, function2 is used.
 * Otherwise, if CPU has feature1, function1 is used.
 * Otherwise, old function is used.
 */
#define alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2, \
			   output, input...)				\
	asm_inline volatile (ALTERNATIVE_2("call %c[old]", "call %c[new1]", ft_flags1, \
		"call %c[new2]", ft_flags2)				\
		: output, ASM_CALL_CONSTRAINT				\
		: [old] "i" (oldfunc), [new1] "i" (newfunc1),		\
		  [new2] "i" (newfunc2), ## input)

/*
 * use this macro(s) if you need more than one output parameter
 * in alternative_io
 */
#define ASM_OUTPUT2(a...) a

/*
 * use this macro if you need clobbers but no inputs in
 * alternative_{input,io,call}()
 */
#define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr

/* Macro for creating assembler functions avoiding any C magic. */
#define DEFINE_ASM_FUNC(func, instr, sec)		\
	asm (".pushsection " #sec ", \"ax\"\n"		\
	     ".global " #func "\n\t"			\
	     ".type " #func ", @function\n\t"		\
	     ASM_FUNC_ALIGN "\n"			\
	     #func ":\n\t"				\
	     ASM_ENDBR					\
	     instr "\n\t"				\
	     ASM_RET					\
	     ".size " #func ", . - " #func "\n\t"	\
	     ".popsection")

void BUG_func(void);
void nop_func(void);

#else /* __ASSEMBLY__ */

#ifdef CONFIG_SMP
	.macro LOCK_PREFIX
672:	lock
	.pushsection .smp_locks,"a"
	.balign 4
	.long 672b - .
	.popsection
	.endm
#else
	.macro LOCK_PREFIX
	.endm
#endif

/*
 * objtool annotation to ignore the alternatives and only consider the original
 * instruction(s).
 */
.macro ANNOTATE_IGNORE_ALTERNATIVE
	.Lannotate_\@:
	.pushsection .discard.ignore_alts
	.long .Lannotate_\@
	.popsection
.endm

/*
 * Issue one struct alt_instr descriptor entry (need to put it into
 * the section .altinstructions, see below). This entry contains
 * enough information for the alternatives patching code to patch an
 * instruction. See apply_alternatives().
 */
.macro altinstr_entry orig alt ft_flags orig_len alt_len
	.long \orig - .
	.long \alt - .
	.4byte \ft_flags
	.byte \orig_len
	.byte \alt_len
.endm

.macro ALT_CALL_INSTR
	call BUG_func
.endm

/*
 * Define an alternative between two instructions. If @feature is
 * present, early code in apply_alternatives() replaces @oldinstr with
 * @newinstr. ".skip" directive takes care of proper instruction padding
 * in case @newinstr is longer than @oldinstr.
 */
.macro ALTERNATIVE oldinstr, newinstr, ft_flags
140:
	\oldinstr
141:
	.skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
142:

	.pushsection .altinstructions,"a"
	altinstr_entry 140b,143f,\ft_flags,142b-140b,144f-143f
	.popsection

	.pushsection .altinstr_replacement,"ax"
143:
	\newinstr
144:
	.popsection
.endm

#define old_len			141b-140b
#define new_len1		144f-143f
#define new_len2		145f-144f
#define new_len3		146f-145f

/*
 * gas compatible max based on the idea from:
 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
 *
 * The additional "-" is needed because gas uses a "true" value of -1.
 */
#define alt_max_2(a, b)		((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
#define alt_max_3(a, b, c)	(alt_max_2(alt_max_2(a, b), c))


/*
 * Same as ALTERNATIVE macro above but for two alternatives. If CPU
 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
 * @feature2, it replaces @oldinstr with @feature2.
 */
.macro ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2
140:
	\oldinstr
141:
	.skip -((alt_max_2(new_len1, new_len2) - (old_len)) > 0) * \
		(alt_max_2(new_len1, new_len2) - (old_len)),0x90
142:

	.pushsection .altinstructions,"a"
	altinstr_entry 140b,143f,\ft_flags1,142b-140b,144f-143f
	altinstr_entry 140b,144f,\ft_flags2,142b-140b,145f-144f
	.popsection

	.pushsection .altinstr_replacement,"ax"
143:
	\newinstr1
144:
	\newinstr2
145:
	.popsection
.endm

.macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
140:
	\oldinstr
141:
	.skip -((alt_max_3(new_len1, new_len2, new_len3) - (old_len)) > 0) * \
		(alt_max_3(new_len1, new_len2, new_len3) - (old_len)),0x90
142:

	.pushsection .altinstructions,"a"
	altinstr_entry 140b,143f,\ft_flags1,142b-140b,144f-143f
	altinstr_entry 140b,144f,\ft_flags2,142b-140b,145f-144f
	altinstr_entry 140b,145f,\ft_flags3,142b-140b,146f-145f
	.popsection

	.pushsection .altinstr_replacement,"ax"
143:
	\newinstr1
144:
	\newinstr2
145:
	\newinstr3
146:
	.popsection
.endm

/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
#define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
	ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS,	\
	newinstr_yes, ft_flags

#endif /* __ASSEMBLY__ */

#endif /* _ASM_X86_ALTERNATIVE_H */