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 ALTINSTR_FLAG_INV (1 << 15)
10 #define ALT_NOT(feat) ((feat) | ALTINSTR_FLAG_INV)
11
12 #ifndef __ASSEMBLY__
13
14 #include <linux/stddef.h>
15
16 /*
17 * Alternative inline assembly for SMP.
18 *
19 * The LOCK_PREFIX macro defined here replaces the LOCK and
20 * LOCK_PREFIX macros used everywhere in the source tree.
21 *
22 * SMP alternatives use the same data structures as the other
23 * alternatives and the X86_FEATURE_UP flag to indicate the case of a
24 * UP system running a SMP kernel. The existing apply_alternatives()
25 * works fine for patching a SMP kernel for UP.
26 *
27 * The SMP alternative tables can be kept after boot and contain both
28 * UP and SMP versions of the instructions to allow switching back to
29 * SMP at runtime, when hotplugging in a new CPU, which is especially
30 * useful in virtualized environments.
31 *
32 * The very common lock prefix is handled as special case in a
33 * separate table which is a pure address list without replacement ptr
34 * and size information. That keeps the table sizes small.
35 */
36
37 #ifdef CONFIG_SMP
38 #define LOCK_PREFIX_HERE \
39 ".pushsection .smp_locks,\"a\"\n" \
40 ".balign 4\n" \
41 ".long 671f - .\n" /* offset */ \
42 ".popsection\n" \
43 "671:"
44
45 #define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; "
46
47 #else /* ! CONFIG_SMP */
48 #define LOCK_PREFIX_HERE ""
49 #define LOCK_PREFIX ""
50 #endif
51
52 /*
53 * objtool annotation to ignore the alternatives and only consider the original
54 * instruction(s).
55 */
56 #define ANNOTATE_IGNORE_ALTERNATIVE \
57 "999:\n\t" \
58 ".pushsection .discard.ignore_alts\n\t" \
59 ".long 999b - .\n\t" \
60 ".popsection\n\t"
61
62 struct alt_instr {
63 s32 instr_offset; /* original instruction */
64 s32 repl_offset; /* offset to replacement instruction */
65 u16 cpuid; /* cpuid bit set for replacement */
66 u8 instrlen; /* length of original instruction */
67 u8 replacementlen; /* length of new instruction */
68 } __packed;
69
70 /*
71 * Debug flag that can be tested to see whether alternative
72 * instructions were patched in already:
73 */
74 extern int alternatives_patched;
75
76 extern void alternative_instructions(void);
77 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
78 extern void apply_retpolines(s32 *start, s32 *end);
79
80 struct module;
81
82 #ifdef CONFIG_SMP
83 extern void alternatives_smp_module_add(struct module *mod, char *name,
84 void *locks, void *locks_end,
85 void *text, void *text_end);
86 extern void alternatives_smp_module_del(struct module *mod);
87 extern void alternatives_enable_smp(void);
88 extern int alternatives_text_reserved(void *start, void *end);
89 extern bool skip_smp_alternatives;
90 #else
alternatives_smp_module_add(struct module * mod,char * name,void * locks,void * locks_end,void * text,void * text_end)91 static inline void alternatives_smp_module_add(struct module *mod, char *name,
92 void *locks, void *locks_end,
93 void *text, void *text_end) {}
alternatives_smp_module_del(struct module * mod)94 static inline void alternatives_smp_module_del(struct module *mod) {}
alternatives_enable_smp(void)95 static inline void alternatives_enable_smp(void) {}
alternatives_text_reserved(void * start,void * end)96 static inline int alternatives_text_reserved(void *start, void *end)
97 {
98 return 0;
99 }
100 #endif /* CONFIG_SMP */
101
102 #define b_replacement(num) "664"#num
103 #define e_replacement(num) "665"#num
104
105 #define alt_end_marker "663"
106 #define alt_slen "662b-661b"
107 #define alt_total_slen alt_end_marker"b-661b"
108 #define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f"
109
110 #define OLDINSTR(oldinstr, num) \
111 "# ALT: oldnstr\n" \
112 "661:\n\t" oldinstr "\n662:\n" \
113 "# ALT: padding\n" \
114 ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \
115 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" \
116 alt_end_marker ":\n"
117
118 /*
119 * gas compatible max based on the idea from:
120 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
121 *
122 * The additional "-" is needed because gas uses a "true" value of -1.
123 */
124 #define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))"
125
126 /*
127 * Pad the second replacement alternative with additional NOPs if it is
128 * additionally longer than the first replacement alternative.
129 */
130 #define OLDINSTR_2(oldinstr, num1, num2) \
131 "# ALT: oldinstr2\n" \
132 "661:\n\t" oldinstr "\n662:\n" \
133 "# ALT: padding2\n" \
134 ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \
135 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \
136 alt_end_marker ":\n"
137
138 #define OLDINSTR_3(oldinsn, n1, n2, n3) \
139 "# ALT: oldinstr3\n" \
140 "661:\n\t" oldinsn "\n662:\n" \
141 "# ALT: padding3\n" \
142 ".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \
143 " - (" alt_slen ")) > 0) * " \
144 "(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \
145 " - (" alt_slen ")), 0x90\n" \
146 alt_end_marker ":\n"
147
148 #define ALTINSTR_ENTRY(feature, num) \
149 " .long 661b - .\n" /* label */ \
150 " .long " b_replacement(num)"f - .\n" /* new instruction */ \
151 " .word " __stringify(feature) "\n" /* feature bit */ \
152 " .byte " alt_total_slen "\n" /* source len */ \
153 " .byte " alt_rlen(num) "\n" /* replacement len */
154
155 #define ALTINSTR_REPLACEMENT(newinstr, num) /* replacement */ \
156 "# ALT: replacement " #num "\n" \
157 b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n"
158
159 /* alternative assembly primitive: */
160 #define ALTERNATIVE(oldinstr, newinstr, feature) \
161 OLDINSTR(oldinstr, 1) \
162 ".pushsection .altinstructions,\"a\"\n" \
163 ALTINSTR_ENTRY(feature, 1) \
164 ".popsection\n" \
165 ".pushsection .altinstr_replacement, \"ax\"\n" \
166 ALTINSTR_REPLACEMENT(newinstr, 1) \
167 ".popsection\n"
168
169 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
170 OLDINSTR_2(oldinstr, 1, 2) \
171 ".pushsection .altinstructions,\"a\"\n" \
172 ALTINSTR_ENTRY(feature1, 1) \
173 ALTINSTR_ENTRY(feature2, 2) \
174 ".popsection\n" \
175 ".pushsection .altinstr_replacement, \"ax\"\n" \
176 ALTINSTR_REPLACEMENT(newinstr1, 1) \
177 ALTINSTR_REPLACEMENT(newinstr2, 2) \
178 ".popsection\n"
179
180 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
181 #define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \
182 ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \
183 newinstr_yes, feature)
184
185 #define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \
186 OLDINSTR_3(oldinsn, 1, 2, 3) \
187 ".pushsection .altinstructions,\"a\"\n" \
188 ALTINSTR_ENTRY(feat1, 1) \
189 ALTINSTR_ENTRY(feat2, 2) \
190 ALTINSTR_ENTRY(feat3, 3) \
191 ".popsection\n" \
192 ".pushsection .altinstr_replacement, \"ax\"\n" \
193 ALTINSTR_REPLACEMENT(newinsn1, 1) \
194 ALTINSTR_REPLACEMENT(newinsn2, 2) \
195 ALTINSTR_REPLACEMENT(newinsn3, 3) \
196 ".popsection\n"
197
198 /*
199 * Alternative instructions for different CPU types or capabilities.
200 *
201 * This allows to use optimized instructions even on generic binary
202 * kernels.
203 *
204 * length of oldinstr must be longer or equal the length of newinstr
205 * It can be padded with nops as needed.
206 *
207 * For non barrier like inlines please define new variants
208 * without volatile and memory clobber.
209 */
210 #define alternative(oldinstr, newinstr, feature) \
211 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
212
213 #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
214 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")
215
216 #define alternative_ternary(oldinstr, feature, newinstr_yes, newinstr_no) \
217 asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) ::: "memory")
218
219 /*
220 * Alternative inline assembly with input.
221 *
222 * Peculiarities:
223 * No memory clobber here.
224 * Argument numbers start with 1.
225 * Leaving an unused argument 0 to keep API compatibility.
226 */
227 #define alternative_input(oldinstr, newinstr, feature, input...) \
228 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
229 : : "i" (0), ## input)
230
231 /*
232 * This is similar to alternative_input. But it has two features and
233 * respective instructions.
234 *
235 * If CPU has feature2, newinstr2 is used.
236 * Otherwise, if CPU has feature1, newinstr1 is used.
237 * Otherwise, oldinstr is used.
238 */
239 #define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \
240 feature2, input...) \
241 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \
242 newinstr2, feature2) \
243 : : "i" (0), ## input)
244
245 /* Like alternative_input, but with a single output argument */
246 #define alternative_io(oldinstr, newinstr, feature, output, input...) \
247 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
248 : output : "i" (0), ## input)
249
250 /* Like alternative_io, but for replacing a direct call with another one. */
251 #define alternative_call(oldfunc, newfunc, feature, output, input...) \
252 asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
253 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
254
255 /*
256 * Like alternative_call, but there are two features and respective functions.
257 * If CPU has feature2, function2 is used.
258 * Otherwise, if CPU has feature1, function1 is used.
259 * Otherwise, old function is used.
260 */
261 #define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \
262 output, input...) \
263 asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\
264 "call %P[new2]", feature2) \
265 : output, ASM_CALL_CONSTRAINT \
266 : [old] "i" (oldfunc), [new1] "i" (newfunc1), \
267 [new2] "i" (newfunc2), ## input)
268
269 /*
270 * use this macro(s) if you need more than one output parameter
271 * in alternative_io
272 */
273 #define ASM_OUTPUT2(a...) a
274
275 /*
276 * use this macro if you need clobbers but no inputs in
277 * alternative_{input,io,call}()
278 */
279 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr
280
281 #else /* __ASSEMBLY__ */
282
283 #ifdef CONFIG_SMP
284 .macro LOCK_PREFIX
285 672: lock
286 .pushsection .smp_locks,"a"
287 .balign 4
288 .long 672b - .
289 .popsection
290 .endm
291 #else
292 .macro LOCK_PREFIX
293 .endm
294 #endif
295
296 /*
297 * objtool annotation to ignore the alternatives and only consider the original
298 * instruction(s).
299 */
300 .macro ANNOTATE_IGNORE_ALTERNATIVE
301 .Lannotate_\@:
302 .pushsection .discard.ignore_alts
303 .long .Lannotate_\@ - .
304 .popsection
305 .endm
306
307 /*
308 * Issue one struct alt_instr descriptor entry (need to put it into
309 * the section .altinstructions, see below). This entry contains
310 * enough information for the alternatives patching code to patch an
311 * instruction. See apply_alternatives().
312 */
313 .macro altinstruction_entry orig alt feature orig_len alt_len
314 .long \orig - .
315 .long \alt - .
316 .word \feature
317 .byte \orig_len
318 .byte \alt_len
319 .endm
320
321 /*
322 * Define an alternative between two instructions. If @feature is
323 * present, early code in apply_alternatives() replaces @oldinstr with
324 * @newinstr. ".skip" directive takes care of proper instruction padding
325 * in case @newinstr is longer than @oldinstr.
326 */
327 .macro ALTERNATIVE oldinstr, newinstr, feature
328 140:
329 \oldinstr
330 141:
331 .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
332 142:
333
334 .pushsection .altinstructions,"a"
335 altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f
336 .popsection
337
338 .pushsection .altinstr_replacement,"ax"
339 143:
340 \newinstr
341 144:
342 .popsection
343 .endm
344
345 #define old_len 141b-140b
346 #define new_len1 144f-143f
347 #define new_len2 145f-144f
348
349 /*
350 * gas compatible max based on the idea from:
351 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
352 *
353 * The additional "-" is needed because gas uses a "true" value of -1.
354 */
355 #define alt_max_short(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
356
357
358 /*
359 * Same as ALTERNATIVE macro above but for two alternatives. If CPU
360 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
361 * @feature2, it replaces @oldinstr with @feature2.
362 */
363 .macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
364 140:
365 \oldinstr
366 141:
367 .skip -((alt_max_short(new_len1, new_len2) - (old_len)) > 0) * \
368 (alt_max_short(new_len1, new_len2) - (old_len)),0x90
369 142:
370
371 .pushsection .altinstructions,"a"
372 altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f
373 altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f
374 .popsection
375
376 .pushsection .altinstr_replacement,"ax"
377 143:
378 \newinstr1
379 144:
380 \newinstr2
381 145:
382 .popsection
383 .endm
384
385 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
386 #define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \
387 ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \
388 newinstr_yes, feature
389
390 #endif /* __ASSEMBLY__ */
391
392 #endif /* _ASM_X86_ALTERNATIVE_H */
393