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 extern void apply_returns(s32 *start, s32 *end);
80
81 struct module;
82
83 #ifdef CONFIG_SMP
84 extern void alternatives_smp_module_add(struct module *mod, char *name,
85 void *locks, void *locks_end,
86 void *text, void *text_end);
87 extern void alternatives_smp_module_del(struct module *mod);
88 extern void alternatives_enable_smp(void);
89 extern int alternatives_text_reserved(void *start, void *end);
90 extern bool skip_smp_alternatives;
91 #else
alternatives_smp_module_add(struct module * mod,char * name,void * locks,void * locks_end,void * text,void * text_end)92 static inline void alternatives_smp_module_add(struct module *mod, char *name,
93 void *locks, void *locks_end,
94 void *text, void *text_end) {}
alternatives_smp_module_del(struct module * mod)95 static inline void alternatives_smp_module_del(struct module *mod) {}
alternatives_enable_smp(void)96 static inline void alternatives_enable_smp(void) {}
alternatives_text_reserved(void * start,void * end)97 static inline int alternatives_text_reserved(void *start, void *end)
98 {
99 return 0;
100 }
101 #endif /* CONFIG_SMP */
102
103 #define b_replacement(num) "664"#num
104 #define e_replacement(num) "665"#num
105
106 #define alt_end_marker "663"
107 #define alt_slen "662b-661b"
108 #define alt_total_slen alt_end_marker"b-661b"
109 #define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f"
110
111 #define OLDINSTR(oldinstr, num) \
112 "# ALT: oldnstr\n" \
113 "661:\n\t" oldinstr "\n662:\n" \
114 "# ALT: padding\n" \
115 ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \
116 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" \
117 alt_end_marker ":\n"
118
119 /*
120 * gas compatible max based on the idea from:
121 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
122 *
123 * The additional "-" is needed because gas uses a "true" value of -1.
124 */
125 #define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))"
126
127 /*
128 * Pad the second replacement alternative with additional NOPs if it is
129 * additionally longer than the first replacement alternative.
130 */
131 #define OLDINSTR_2(oldinstr, num1, num2) \
132 "# ALT: oldinstr2\n" \
133 "661:\n\t" oldinstr "\n662:\n" \
134 "# ALT: padding2\n" \
135 ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \
136 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \
137 alt_end_marker ":\n"
138
139 #define OLDINSTR_3(oldinsn, n1, n2, n3) \
140 "# ALT: oldinstr3\n" \
141 "661:\n\t" oldinsn "\n662:\n" \
142 "# ALT: padding3\n" \
143 ".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \
144 " - (" alt_slen ")) > 0) * " \
145 "(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \
146 " - (" alt_slen ")), 0x90\n" \
147 alt_end_marker ":\n"
148
149 #define ALTINSTR_ENTRY(feature, num) \
150 " .long 661b - .\n" /* label */ \
151 " .long " b_replacement(num)"f - .\n" /* new instruction */ \
152 " .word " __stringify(feature) "\n" /* feature bit */ \
153 " .byte " alt_total_slen "\n" /* source len */ \
154 " .byte " alt_rlen(num) "\n" /* replacement len */
155
156 #define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \
157 "# ALT: replacement " #num "\n" \
158 b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n"
159
160 /* alternative assembly primitive: */
161 #define ALTERNATIVE(oldinstr, newinstr, feature) \
162 OLDINSTR(oldinstr, 1) \
163 ".pushsection .altinstructions,\"a\"\n" \
164 ALTINSTR_ENTRY(feature, 1) \
165 ".popsection\n" \
166 ".pushsection .altinstr_replacement, \"ax\"\n" \
167 ALTINSTR_REPLACEMENT(newinstr, feature, 1) \
168 ".popsection\n"
169
170 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
171 OLDINSTR_2(oldinstr, 1, 2) \
172 ".pushsection .altinstructions,\"a\"\n" \
173 ALTINSTR_ENTRY(feature1, 1) \
174 ALTINSTR_ENTRY(feature2, 2) \
175 ".popsection\n" \
176 ".pushsection .altinstr_replacement, \"ax\"\n" \
177 ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \
178 ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \
179 ".popsection\n"
180
181 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
182 #define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \
183 ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \
184 newinstr_yes, feature)
185
186 #define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \
187 OLDINSTR_3(oldinsn, 1, 2, 3) \
188 ".pushsection .altinstructions,\"a\"\n" \
189 ALTINSTR_ENTRY(feat1, 1) \
190 ALTINSTR_ENTRY(feat2, 2) \
191 ALTINSTR_ENTRY(feat3, 3) \
192 ".popsection\n" \
193 ".pushsection .altinstr_replacement, \"ax\"\n" \
194 ALTINSTR_REPLACEMENT(newinsn1, feat1, 1) \
195 ALTINSTR_REPLACEMENT(newinsn2, feat2, 2) \
196 ALTINSTR_REPLACEMENT(newinsn3, feat3, 3) \
197 ".popsection\n"
198
199 /*
200 * Alternative instructions for different CPU types or capabilities.
201 *
202 * This allows to use optimized instructions even on generic binary
203 * kernels.
204 *
205 * length of oldinstr must be longer or equal the length of newinstr
206 * It can be padded with nops as needed.
207 *
208 * For non barrier like inlines please define new variants
209 * without volatile and memory clobber.
210 */
211 #define alternative(oldinstr, newinstr, feature) \
212 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
213
214 #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
215 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")
216
217 #define alternative_ternary(oldinstr, feature, newinstr_yes, newinstr_no) \
218 asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) ::: "memory")
219
220 /*
221 * Alternative inline assembly with input.
222 *
223 * Peculiarities:
224 * No memory clobber here.
225 * Argument numbers start with 1.
226 * Leaving an unused argument 0 to keep API compatibility.
227 */
228 #define alternative_input(oldinstr, newinstr, feature, input...) \
229 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
230 : : "i" (0), ## input)
231
232 /*
233 * This is similar to alternative_input. But it has two features and
234 * respective instructions.
235 *
236 * If CPU has feature2, newinstr2 is used.
237 * Otherwise, if CPU has feature1, newinstr1 is used.
238 * Otherwise, oldinstr is used.
239 */
240 #define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \
241 feature2, input...) \
242 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \
243 newinstr2, feature2) \
244 : : "i" (0), ## input)
245
246 /* Like alternative_input, but with a single output argument */
247 #define alternative_io(oldinstr, newinstr, feature, output, input...) \
248 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
249 : output : "i" (0), ## input)
250
251 /* Like alternative_io, but for replacing a direct call with another one. */
252 #define alternative_call(oldfunc, newfunc, feature, output, input...) \
253 asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
254 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
255
256 /*
257 * Like alternative_call, but there are two features and respective functions.
258 * If CPU has feature2, function2 is used.
259 * Otherwise, if CPU has feature1, function1 is used.
260 * Otherwise, old function is used.
261 */
262 #define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \
263 output, input...) \
264 asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\
265 "call %P[new2]", feature2) \
266 : output, ASM_CALL_CONSTRAINT \
267 : [old] "i" (oldfunc), [new1] "i" (newfunc1), \
268 [new2] "i" (newfunc2), ## input)
269
270 /*
271 * use this macro(s) if you need more than one output parameter
272 * in alternative_io
273 */
274 #define ASM_OUTPUT2(a...) a
275
276 /*
277 * use this macro if you need clobbers but no inputs in
278 * alternative_{input,io,call}()
279 */
280 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr
281
282 #else /* __ASSEMBLY__ */
283
284 #ifdef CONFIG_SMP
285 .macro LOCK_PREFIX
286 672: lock
287 .pushsection .smp_locks,"a"
288 .balign 4
289 .long 672b - .
290 .popsection
291 .endm
292 #else
293 .macro LOCK_PREFIX
294 .endm
295 #endif
296
297 /*
298 * objtool annotation to ignore the alternatives and only consider the original
299 * instruction(s).
300 */
301 .macro ANNOTATE_IGNORE_ALTERNATIVE
302 .Lannotate_\@:
303 .pushsection .discard.ignore_alts
304 .long .Lannotate_\@ - .
305 .popsection
306 .endm
307
308 /*
309 * Issue one struct alt_instr descriptor entry (need to put it into
310 * the section .altinstructions, see below). This entry contains
311 * enough information for the alternatives patching code to patch an
312 * instruction. See apply_alternatives().
313 */
314 .macro altinstruction_entry orig alt feature orig_len alt_len
315 .long \orig - .
316 .long \alt - .
317 .word \feature
318 .byte \orig_len
319 .byte \alt_len
320 .endm
321
322 /*
323 * Define an alternative between two instructions. If @feature is
324 * present, early code in apply_alternatives() replaces @oldinstr with
325 * @newinstr. ".skip" directive takes care of proper instruction padding
326 * in case @newinstr is longer than @oldinstr.
327 */
328 .macro ALTERNATIVE oldinstr, newinstr, feature
329 140:
330 \oldinstr
331 141:
332 .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
333 142:
334
335 .pushsection .altinstructions,"a"
336 altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f
337 .popsection
338
339 .pushsection .altinstr_replacement,"ax"
340 143:
341 \newinstr
342 144:
343 .popsection
344 .endm
345
346 #define old_len 141b-140b
347 #define new_len1 144f-143f
348 #define new_len2 145f-144f
349
350 /*
351 * gas compatible max based on the idea from:
352 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
353 *
354 * The additional "-" is needed because gas uses a "true" value of -1.
355 */
356 #define alt_max_short(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
357
358
359 /*
360 * Same as ALTERNATIVE macro above but for two alternatives. If CPU
361 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
362 * @feature2, it replaces @oldinstr with @feature2.
363 */
364 .macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
365 140:
366 \oldinstr
367 141:
368 .skip -((alt_max_short(new_len1, new_len2) - (old_len)) > 0) * \
369 (alt_max_short(new_len1, new_len2) - (old_len)),0x90
370 142:
371
372 .pushsection .altinstructions,"a"
373 altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f
374 altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f
375 .popsection
376
377 .pushsection .altinstr_replacement,"ax"
378 143:
379 \newinstr1
380 144:
381 \newinstr2
382 145:
383 .popsection
384 .endm
385
386 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
387 #define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \
388 ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \
389 newinstr_yes, feature
390
391 #endif /* __ASSEMBLY__ */
392
393 #endif /* _ASM_X86_ALTERNATIVE_H */
394