1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_X86_ALTERNATIVE_H
3 #define _ASM_X86_ALTERNATIVE_H
4
5 #include <linux/types.h>
6 #include <linux/stringify.h>
7 #include <asm/asm.h>
8
9 #define ALT_FLAGS_SHIFT 16
10
11 #define ALT_FLAG_NOT BIT(0)
12 #define ALT_NOT(feature) ((ALT_FLAG_NOT << ALT_FLAGS_SHIFT) | (feature))
13
14 #ifndef __ASSEMBLY__
15
16 #include <linux/stddef.h>
17
18 /*
19 * Alternative inline assembly for SMP.
20 *
21 * The LOCK_PREFIX macro defined here replaces the LOCK and
22 * LOCK_PREFIX macros used everywhere in the source tree.
23 *
24 * SMP alternatives use the same data structures as the other
25 * alternatives and the X86_FEATURE_UP flag to indicate the case of a
26 * UP system running a SMP kernel. The existing apply_alternatives()
27 * works fine for patching a SMP kernel for UP.
28 *
29 * The SMP alternative tables can be kept after boot and contain both
30 * UP and SMP versions of the instructions to allow switching back to
31 * SMP at runtime, when hotplugging in a new CPU, which is especially
32 * useful in virtualized environments.
33 *
34 * The very common lock prefix is handled as special case in a
35 * separate table which is a pure address list without replacement ptr
36 * and size information. That keeps the table sizes small.
37 */
38
39 #ifdef CONFIG_SMP
40 #define LOCK_PREFIX_HERE \
41 ".pushsection .smp_locks,\"a\"\n" \
42 ".balign 4\n" \
43 ".long 671f - .\n" /* offset */ \
44 ".popsection\n" \
45 "671:"
46
47 #define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; "
48
49 #else /* ! CONFIG_SMP */
50 #define LOCK_PREFIX_HERE ""
51 #define LOCK_PREFIX ""
52 #endif
53
54 /*
55 * objtool annotation to ignore the alternatives and only consider the original
56 * instruction(s).
57 */
58 #define ANNOTATE_IGNORE_ALTERNATIVE \
59 "999:\n\t" \
60 ".pushsection .discard.ignore_alts\n\t" \
61 ".long 999b - .\n\t" \
62 ".popsection\n\t"
63
64 /*
65 * The patching flags are part of the upper bits of the @ft_flags parameter when
66 * specifying them. The split is currently like this:
67 *
68 * [31... flags ...16][15... CPUID feature bit ...0]
69 *
70 * but since this is all hidden in the macros argument being split, those fields can be
71 * extended in the future to fit in a u64 or however the need arises.
72 */
73 struct alt_instr {
74 s32 instr_offset; /* original instruction */
75 s32 repl_offset; /* offset to replacement instruction */
76
77 union {
78 struct {
79 u32 cpuid: 16; /* CPUID bit set for replacement */
80 u32 flags: 16; /* patching control flags */
81 };
82 u32 ft_flags;
83 };
84
85 u8 instrlen; /* length of original instruction */
86 u8 replacementlen; /* length of new instruction */
87 } __packed;
88
89 /*
90 * Debug flag that can be tested to see whether alternative
91 * instructions were patched in already:
92 */
93 extern int alternatives_patched;
94
95 extern void alternative_instructions(void);
96 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
97 extern void apply_retpolines(s32 *start, s32 *end);
98 extern void apply_returns(s32 *start, s32 *end);
99 extern void apply_ibt_endbr(s32 *start, s32 *end);
100 extern void apply_fineibt(s32 *start_retpoline, s32 *end_retpoine,
101 s32 *start_cfi, s32 *end_cfi);
102
103 struct module;
104 struct paravirt_patch_site;
105
106 struct callthunk_sites {
107 s32 *call_start, *call_end;
108 struct paravirt_patch_site *pv_start, *pv_end;
109 };
110
111 #ifdef CONFIG_CALL_THUNKS
112 extern void callthunks_patch_builtin_calls(void);
113 extern void callthunks_patch_module_calls(struct callthunk_sites *sites,
114 struct module *mod);
115 extern void *callthunks_translate_call_dest(void *dest);
116 extern bool is_callthunk(void *addr);
117 extern int x86_call_depth_emit_accounting(u8 **pprog, void *func);
118 #else
callthunks_patch_builtin_calls(void)119 static __always_inline void callthunks_patch_builtin_calls(void) {}
120 static __always_inline void
callthunks_patch_module_calls(struct callthunk_sites * sites,struct module * mod)121 callthunks_patch_module_calls(struct callthunk_sites *sites,
122 struct module *mod) {}
callthunks_translate_call_dest(void * dest)123 static __always_inline void *callthunks_translate_call_dest(void *dest)
124 {
125 return dest;
126 }
is_callthunk(void * addr)127 static __always_inline bool is_callthunk(void *addr)
128 {
129 return false;
130 }
x86_call_depth_emit_accounting(u8 ** pprog,void * func)131 static __always_inline int x86_call_depth_emit_accounting(u8 **pprog,
132 void *func)
133 {
134 return 0;
135 }
136 #endif
137
138 #ifdef CONFIG_SMP
139 extern void alternatives_smp_module_add(struct module *mod, char *name,
140 void *locks, void *locks_end,
141 void *text, void *text_end);
142 extern void alternatives_smp_module_del(struct module *mod);
143 extern void alternatives_enable_smp(void);
144 extern int alternatives_text_reserved(void *start, void *end);
145 extern bool skip_smp_alternatives;
146 #else
alternatives_smp_module_add(struct module * mod,char * name,void * locks,void * locks_end,void * text,void * text_end)147 static inline void alternatives_smp_module_add(struct module *mod, char *name,
148 void *locks, void *locks_end,
149 void *text, void *text_end) {}
alternatives_smp_module_del(struct module * mod)150 static inline void alternatives_smp_module_del(struct module *mod) {}
alternatives_enable_smp(void)151 static inline void alternatives_enable_smp(void) {}
alternatives_text_reserved(void * start,void * end)152 static inline int alternatives_text_reserved(void *start, void *end)
153 {
154 return 0;
155 }
156 #endif /* CONFIG_SMP */
157
158 #define b_replacement(num) "664"#num
159 #define e_replacement(num) "665"#num
160
161 #define alt_end_marker "663"
162 #define alt_slen "662b-661b"
163 #define alt_total_slen alt_end_marker"b-661b"
164 #define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f"
165
166 #define OLDINSTR(oldinstr, num) \
167 "# ALT: oldnstr\n" \
168 "661:\n\t" oldinstr "\n662:\n" \
169 "# ALT: padding\n" \
170 ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \
171 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" \
172 alt_end_marker ":\n"
173
174 /*
175 * gas compatible max based on the idea from:
176 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
177 *
178 * The additional "-" is needed because gas uses a "true" value of -1.
179 */
180 #define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))"
181
182 /*
183 * Pad the second replacement alternative with additional NOPs if it is
184 * additionally longer than the first replacement alternative.
185 */
186 #define OLDINSTR_2(oldinstr, num1, num2) \
187 "# ALT: oldinstr2\n" \
188 "661:\n\t" oldinstr "\n662:\n" \
189 "# ALT: padding2\n" \
190 ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \
191 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \
192 alt_end_marker ":\n"
193
194 #define OLDINSTR_3(oldinsn, n1, n2, n3) \
195 "# ALT: oldinstr3\n" \
196 "661:\n\t" oldinsn "\n662:\n" \
197 "# ALT: padding3\n" \
198 ".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \
199 " - (" alt_slen ")) > 0) * " \
200 "(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \
201 " - (" alt_slen ")), 0x90\n" \
202 alt_end_marker ":\n"
203
204 #define ALTINSTR_ENTRY(ft_flags, num) \
205 " .long 661b - .\n" /* label */ \
206 " .long " b_replacement(num)"f - .\n" /* new instruction */ \
207 " .4byte " __stringify(ft_flags) "\n" /* feature + flags */ \
208 " .byte " alt_total_slen "\n" /* source len */ \
209 " .byte " alt_rlen(num) "\n" /* replacement len */
210
211 #define ALTINSTR_REPLACEMENT(newinstr, num) /* replacement */ \
212 "# ALT: replacement " #num "\n" \
213 b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n"
214
215 /* alternative assembly primitive: */
216 #define ALTERNATIVE(oldinstr, newinstr, ft_flags) \
217 OLDINSTR(oldinstr, 1) \
218 ".pushsection .altinstructions,\"a\"\n" \
219 ALTINSTR_ENTRY(ft_flags, 1) \
220 ".popsection\n" \
221 ".pushsection .altinstr_replacement, \"ax\"\n" \
222 ALTINSTR_REPLACEMENT(newinstr, 1) \
223 ".popsection\n"
224
225 #define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
226 OLDINSTR_2(oldinstr, 1, 2) \
227 ".pushsection .altinstructions,\"a\"\n" \
228 ALTINSTR_ENTRY(ft_flags1, 1) \
229 ALTINSTR_ENTRY(ft_flags2, 2) \
230 ".popsection\n" \
231 ".pushsection .altinstr_replacement, \"ax\"\n" \
232 ALTINSTR_REPLACEMENT(newinstr1, 1) \
233 ALTINSTR_REPLACEMENT(newinstr2, 2) \
234 ".popsection\n"
235
236 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
237 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
238 ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \
239 newinstr_yes, ft_flags)
240
241 #define ALTERNATIVE_3(oldinsn, newinsn1, ft_flags1, newinsn2, ft_flags2, \
242 newinsn3, ft_flags3) \
243 OLDINSTR_3(oldinsn, 1, 2, 3) \
244 ".pushsection .altinstructions,\"a\"\n" \
245 ALTINSTR_ENTRY(ft_flags1, 1) \
246 ALTINSTR_ENTRY(ft_flags2, 2) \
247 ALTINSTR_ENTRY(ft_flags3, 3) \
248 ".popsection\n" \
249 ".pushsection .altinstr_replacement, \"ax\"\n" \
250 ALTINSTR_REPLACEMENT(newinsn1, 1) \
251 ALTINSTR_REPLACEMENT(newinsn2, 2) \
252 ALTINSTR_REPLACEMENT(newinsn3, 3) \
253 ".popsection\n"
254
255 /*
256 * Alternative instructions for different CPU types or capabilities.
257 *
258 * This allows to use optimized instructions even on generic binary
259 * kernels.
260 *
261 * length of oldinstr must be longer or equal the length of newinstr
262 * It can be padded with nops as needed.
263 *
264 * For non barrier like inlines please define new variants
265 * without volatile and memory clobber.
266 */
267 #define alternative(oldinstr, newinstr, ft_flags) \
268 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")
269
270 #define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
271 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")
272
273 #define alternative_ternary(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
274 asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) ::: "memory")
275
276 /*
277 * Alternative inline assembly with input.
278 *
279 * Peculiarities:
280 * No memory clobber here.
281 * Argument numbers start with 1.
282 * Leaving an unused argument 0 to keep API compatibility.
283 */
284 #define alternative_input(oldinstr, newinstr, ft_flags, input...) \
285 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags) \
286 : : "i" (0), ## input)
287
288 /*
289 * This is similar to alternative_input. But it has two features and
290 * respective instructions.
291 *
292 * If CPU has feature2, newinstr2 is used.
293 * Otherwise, if CPU has feature1, newinstr1 is used.
294 * Otherwise, oldinstr is used.
295 */
296 #define alternative_input_2(oldinstr, newinstr1, ft_flags1, newinstr2, \
297 ft_flags2, input...) \
298 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, \
299 newinstr2, ft_flags2) \
300 : : "i" (0), ## input)
301
302 /* Like alternative_input, but with a single output argument */
303 #define alternative_io(oldinstr, newinstr, ft_flags, output, input...) \
304 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags) \
305 : output : "i" (0), ## input)
306
307 /* Like alternative_io, but for replacing a direct call with another one. */
308 #define alternative_call(oldfunc, newfunc, ft_flags, output, input...) \
309 asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", ft_flags) \
310 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
311
312 /*
313 * Like alternative_call, but there are two features and respective functions.
314 * If CPU has feature2, function2 is used.
315 * Otherwise, if CPU has feature1, function1 is used.
316 * Otherwise, old function is used.
317 */
318 #define alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2, \
319 output, input...) \
320 asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", ft_flags1,\
321 "call %P[new2]", ft_flags2) \
322 : output, ASM_CALL_CONSTRAINT \
323 : [old] "i" (oldfunc), [new1] "i" (newfunc1), \
324 [new2] "i" (newfunc2), ## input)
325
326 /*
327 * use this macro(s) if you need more than one output parameter
328 * in alternative_io
329 */
330 #define ASM_OUTPUT2(a...) a
331
332 /*
333 * use this macro if you need clobbers but no inputs in
334 * alternative_{input,io,call}()
335 */
336 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr
337
338 #else /* __ASSEMBLY__ */
339
340 #ifdef CONFIG_SMP
341 .macro LOCK_PREFIX
342 672: lock
343 .pushsection .smp_locks,"a"
344 .balign 4
345 .long 672b - .
346 .popsection
347 .endm
348 #else
349 .macro LOCK_PREFIX
350 .endm
351 #endif
352
353 /*
354 * objtool annotation to ignore the alternatives and only consider the original
355 * instruction(s).
356 */
357 .macro ANNOTATE_IGNORE_ALTERNATIVE
358 .Lannotate_\@:
359 .pushsection .discard.ignore_alts
360 .long .Lannotate_\@ - .
361 .popsection
362 .endm
363
364 /*
365 * Issue one struct alt_instr descriptor entry (need to put it into
366 * the section .altinstructions, see below). This entry contains
367 * enough information for the alternatives patching code to patch an
368 * instruction. See apply_alternatives().
369 */
370 .macro altinstr_entry orig alt ft_flags orig_len alt_len
371 .long \orig - .
372 .long \alt - .
373 .4byte \ft_flags
374 .byte \orig_len
375 .byte \alt_len
376 .endm
377
378 /*
379 * Define an alternative between two instructions. If @feature is
380 * present, early code in apply_alternatives() replaces @oldinstr with
381 * @newinstr. ".skip" directive takes care of proper instruction padding
382 * in case @newinstr is longer than @oldinstr.
383 */
384 .macro ALTERNATIVE oldinstr, newinstr, ft_flags
385 140:
386 \oldinstr
387 141:
388 .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
389 142:
390
391 .pushsection .altinstructions,"a"
392 altinstr_entry 140b,143f,\ft_flags,142b-140b,144f-143f
393 .popsection
394
395 .pushsection .altinstr_replacement,"ax"
396 143:
397 \newinstr
398 144:
399 .popsection
400 .endm
401
402 #define old_len 141b-140b
403 #define new_len1 144f-143f
404 #define new_len2 145f-144f
405 #define new_len3 146f-145f
406
407 /*
408 * gas compatible max based on the idea from:
409 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
410 *
411 * The additional "-" is needed because gas uses a "true" value of -1.
412 */
413 #define alt_max_2(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
414 #define alt_max_3(a, b, c) (alt_max_2(alt_max_2(a, b), c))
415
416
417 /*
418 * Same as ALTERNATIVE macro above but for two alternatives. If CPU
419 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
420 * @feature2, it replaces @oldinstr with @feature2.
421 */
422 .macro ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2
423 140:
424 \oldinstr
425 141:
426 .skip -((alt_max_2(new_len1, new_len2) - (old_len)) > 0) * \
427 (alt_max_2(new_len1, new_len2) - (old_len)),0x90
428 142:
429
430 .pushsection .altinstructions,"a"
431 altinstr_entry 140b,143f,\ft_flags1,142b-140b,144f-143f
432 altinstr_entry 140b,144f,\ft_flags2,142b-140b,145f-144f
433 .popsection
434
435 .pushsection .altinstr_replacement,"ax"
436 143:
437 \newinstr1
438 144:
439 \newinstr2
440 145:
441 .popsection
442 .endm
443
444 .macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
445 140:
446 \oldinstr
447 141:
448 .skip -((alt_max_3(new_len1, new_len2, new_len3) - (old_len)) > 0) * \
449 (alt_max_3(new_len1, new_len2, new_len3) - (old_len)),0x90
450 142:
451
452 .pushsection .altinstructions,"a"
453 altinstr_entry 140b,143f,\ft_flags1,142b-140b,144f-143f
454 altinstr_entry 140b,144f,\ft_flags2,142b-140b,145f-144f
455 altinstr_entry 140b,145f,\ft_flags3,142b-140b,146f-145f
456 .popsection
457
458 .pushsection .altinstr_replacement,"ax"
459 143:
460 \newinstr1
461 144:
462 \newinstr2
463 145:
464 \newinstr3
465 146:
466 .popsection
467 .endm
468
469 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
470 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
471 ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \
472 newinstr_yes, ft_flags
473
474 #endif /* __ASSEMBLY__ */
475
476 #endif /* _ASM_X86_ALTERNATIVE_H */
477