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1#ifndef _ASM_X86_ALTERNATIVE_H
2#define _ASM_X86_ALTERNATIVE_H
3
4#ifndef __ASSEMBLY__
5
6#include <linux/types.h>
7#include <linux/stddef.h>
8#include <linux/stringify.h>
9#include <asm/asm.h>
10
11/*
12 * Alternative inline assembly for SMP.
13 *
14 * The LOCK_PREFIX macro defined here replaces the LOCK and
15 * LOCK_PREFIX macros used everywhere in the source tree.
16 *
17 * SMP alternatives use the same data structures as the other
18 * alternatives and the X86_FEATURE_UP flag to indicate the case of a
19 * UP system running a SMP kernel. The existing apply_alternatives()
20 * works fine for patching a SMP kernel for UP.
21 *
22 * The SMP alternative tables can be kept after boot and contain both
23 * UP and SMP versions of the instructions to allow switching back to
24 * SMP at runtime, when hotplugging in a new CPU, which is especially
25 * useful in virtualized environments.
26 *
27 * The very common lock prefix is handled as special case in a
28 * separate table which is a pure address list without replacement ptr
29 * and size information. That keeps the table sizes small.
30 */
31
32#ifdef CONFIG_SMP
33#define LOCK_PREFIX_HERE \
34 ".pushsection .smp_locks,\"a\"\n" \
35 ".balign 4\n" \
36 ".long 671f - .\n" /* offset */ \
37 ".popsection\n" \
38 "671:"
39
40#define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; "
41
42#else /* ! CONFIG_SMP */
43#define LOCK_PREFIX_HERE ""
44#define LOCK_PREFIX ""
45#endif
46
47struct alt_instr {
48 s32 instr_offset; /* original instruction */
49 s32 repl_offset; /* offset to replacement instruction */
50 u16 cpuid; /* cpuid bit set for replacement */
51 u8 instrlen; /* length of original instruction */
52 u8 replacementlen; /* length of new instruction */
53 u8 padlen; /* length of build-time padding */
54} __packed;
55
56/*
57 * Debug flag that can be tested to see whether alternative
58 * instructions were patched in already:
59 */
60extern int alternatives_patched;
61
62extern void alternative_instructions(void);
63extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
64
65struct module;
66
67#ifdef CONFIG_SMP
68extern void alternatives_smp_module_add(struct module *mod, char *name,
69 void *locks, void *locks_end,
70 void *text, void *text_end);
71extern void alternatives_smp_module_del(struct module *mod);
72extern void alternatives_enable_smp(void);
73extern int alternatives_text_reserved(void *start, void *end);
74extern bool skip_smp_alternatives;
75#else
76static inline void alternatives_smp_module_add(struct module *mod, char *name,
77 void *locks, void *locks_end,
78 void *text, void *text_end) {}
79static inline void alternatives_smp_module_del(struct module *mod) {}
80static inline void alternatives_enable_smp(void) {}
81static inline int alternatives_text_reserved(void *start, void *end)
82{
83 return 0;
84}
85#endif /* CONFIG_SMP */
86
87#define b_replacement(num) "664"#num
88#define e_replacement(num) "665"#num
89
90#define alt_end_marker "663"
91#define alt_slen "662b-661b"
92#define alt_pad_len alt_end_marker"b-662b"
93#define alt_total_slen alt_end_marker"b-661b"
94#define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f"
95
96#define __OLDINSTR(oldinstr, num) \
97 "661:\n\t" oldinstr "\n662:\n" \
98 ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \
99 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n"
100
101#define OLDINSTR(oldinstr, num) \
102 __OLDINSTR(oldinstr, num) \
103 alt_end_marker ":\n"
104
105/*
106 * max without conditionals. Idea adapted from:
107 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
108 *
109 * The additional "-" is needed because gas works with s32s.
110 */
111#define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") - (" b ")))))"
112
113/*
114 * Pad the second replacement alternative with additional NOPs if it is
115 * additionally longer than the first replacement alternative.
116 */
117#define OLDINSTR_2(oldinstr, num1, num2) \
118 "661:\n\t" oldinstr "\n662:\n" \
119 ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \
120 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \
121 alt_end_marker ":\n"
122
123#define ALTINSTR_ENTRY(feature, num) \
124 " .long 661b - .\n" /* label */ \
125 " .long " b_replacement(num)"f - .\n" /* new instruction */ \
126 " .word " __stringify(feature) "\n" /* feature bit */ \
127 " .byte " alt_total_slen "\n" /* source len */ \
128 " .byte " alt_rlen(num) "\n" /* replacement len */ \
129 " .byte " alt_pad_len "\n" /* pad len */
130
131#define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \
132 b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n\t"
133
134/* alternative assembly primitive: */
135#define ALTERNATIVE(oldinstr, newinstr, feature) \
136 OLDINSTR(oldinstr, 1) \
137 ".pushsection .altinstructions,\"a\"\n" \
138 ALTINSTR_ENTRY(feature, 1) \
139 ".popsection\n" \
140 ".pushsection .altinstr_replacement, \"ax\"\n" \
141 ALTINSTR_REPLACEMENT(newinstr, feature, 1) \
142 ".popsection"
143
144#define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
145 OLDINSTR_2(oldinstr, 1, 2) \
146 ".pushsection .altinstructions,\"a\"\n" \
147 ALTINSTR_ENTRY(feature1, 1) \
148 ALTINSTR_ENTRY(feature2, 2) \
149 ".popsection\n" \
150 ".pushsection .altinstr_replacement, \"ax\"\n" \
151 ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \
152 ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \
153 ".popsection"
154
155/*
156 * Alternative instructions for different CPU types or capabilities.
157 *
158 * This allows to use optimized instructions even on generic binary
159 * kernels.
160 *
161 * length of oldinstr must be longer or equal the length of newinstr
162 * It can be padded with nops as needed.
163 *
164 * For non barrier like inlines please define new variants
165 * without volatile and memory clobber.
166 */
167#define alternative(oldinstr, newinstr, feature) \
168 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
169
170#define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
171 asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")
172
173/*
174 * Alternative inline assembly with input.
175 *
176 * Pecularities:
177 * No memory clobber here.
178 * Argument numbers start with 1.
179 * Best is to use constraints that are fixed size (like (%1) ... "r")
180 * If you use variable sized constraints like "m" or "g" in the
181 * replacement make sure to pad to the worst case length.
182 * Leaving an unused argument 0 to keep API compatibility.
183 */
184#define alternative_input(oldinstr, newinstr, feature, input...) \
185 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
186 : : "i" (0), ## input)
187
188/*
189 * This is similar to alternative_input. But it has two features and
190 * respective instructions.
191 *
192 * If CPU has feature2, newinstr2 is used.
193 * Otherwise, if CPU has feature1, newinstr1 is used.
194 * Otherwise, oldinstr is used.
195 */
196#define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \
197 feature2, input...) \
198 asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \
199 newinstr2, feature2) \
200 : : "i" (0), ## input)
201
202/* Like alternative_input, but with a single output argument */
203#define alternative_io(oldinstr, newinstr, feature, output, input...) \
204 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
205 : output : "i" (0), ## input)
206
207/* Like alternative_io, but for replacing a direct call with another one. */
208#define alternative_call(oldfunc, newfunc, feature, output, input...) \
209 asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
210 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
211
212/*
213 * Like alternative_call, but there are two features and respective functions.
214 * If CPU has feature2, function2 is used.
215 * Otherwise, if CPU has feature1, function1 is used.
216 * Otherwise, old function is used.
217 */
218#define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \
219 output, input...) \
220{ \
221 register void *__sp asm(_ASM_SP); \
222 asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\
223 "call %P[new2]", feature2) \
224 : output, "+r" (__sp) \
225 : [old] "i" (oldfunc), [new1] "i" (newfunc1), \
226 [new2] "i" (newfunc2), ## input); \
227}
228
229/*
230 * use this macro(s) if you need more than one output parameter
231 * in alternative_io
232 */
233#define ASM_OUTPUT2(a...) a
234
235/*
236 * use this macro if you need clobbers but no inputs in
237 * alternative_{input,io,call}()
238 */
239#define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr
240
241#endif /* __ASSEMBLY__ */
242
243#endif /* _ASM_X86_ALTERNATIVE_H */
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
62struct 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 */
74extern int alternatives_patched;
75
76extern void alternative_instructions(void);
77extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
78extern void apply_retpolines(s32 *start, s32 *end);
79extern void apply_returns(s32 *start, s32 *end);
80extern void apply_ibt_endbr(s32 *start, s32 *end);
81extern void apply_fineibt(s32 *start_retpoline, s32 *end_retpoine,
82 s32 *start_cfi, s32 *end_cfi);
83
84struct module;
85struct paravirt_patch_site;
86
87struct callthunk_sites {
88 s32 *call_start, *call_end;
89 struct paravirt_patch_site *pv_start, *pv_end;
90};
91
92#ifdef CONFIG_CALL_THUNKS
93extern void callthunks_patch_builtin_calls(void);
94extern void callthunks_patch_module_calls(struct callthunk_sites *sites,
95 struct module *mod);
96extern void *callthunks_translate_call_dest(void *dest);
97extern bool is_callthunk(void *addr);
98extern int x86_call_depth_emit_accounting(u8 **pprog, void *func);
99#else
100static __always_inline void callthunks_patch_builtin_calls(void) {}
101static __always_inline void
102callthunks_patch_module_calls(struct callthunk_sites *sites,
103 struct module *mod) {}
104static __always_inline void *callthunks_translate_call_dest(void *dest)
105{
106 return dest;
107}
108static __always_inline bool is_callthunk(void *addr)
109{
110 return false;
111}
112static __always_inline int x86_call_depth_emit_accounting(u8 **pprog,
113 void *func)
114{
115 return 0;
116}
117#endif
118
119#ifdef CONFIG_SMP
120extern void alternatives_smp_module_add(struct module *mod, char *name,
121 void *locks, void *locks_end,
122 void *text, void *text_end);
123extern void alternatives_smp_module_del(struct module *mod);
124extern void alternatives_enable_smp(void);
125extern int alternatives_text_reserved(void *start, void *end);
126extern bool skip_smp_alternatives;
127#else
128static inline void alternatives_smp_module_add(struct module *mod, char *name,
129 void *locks, void *locks_end,
130 void *text, void *text_end) {}
131static inline void alternatives_smp_module_del(struct module *mod) {}
132static inline void alternatives_enable_smp(void) {}
133static inline int alternatives_text_reserved(void *start, void *end)
134{
135 return 0;
136}
137#endif /* CONFIG_SMP */
138
139#define b_replacement(num) "664"#num
140#define e_replacement(num) "665"#num
141
142#define alt_end_marker "663"
143#define alt_slen "662b-661b"
144#define alt_total_slen alt_end_marker"b-661b"
145#define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f"
146
147#define OLDINSTR(oldinstr, num) \
148 "# ALT: oldnstr\n" \
149 "661:\n\t" oldinstr "\n662:\n" \
150 "# ALT: padding\n" \
151 ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \
152 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" \
153 alt_end_marker ":\n"
154
155/*
156 * gas compatible max based on the idea from:
157 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
158 *
159 * The additional "-" is needed because gas uses a "true" value of -1.
160 */
161#define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))"
162
163/*
164 * Pad the second replacement alternative with additional NOPs if it is
165 * additionally longer than the first replacement alternative.
166 */
167#define OLDINSTR_2(oldinstr, num1, num2) \
168 "# ALT: oldinstr2\n" \
169 "661:\n\t" oldinstr "\n662:\n" \
170 "# ALT: padding2\n" \
171 ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \
172 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \
173 alt_end_marker ":\n"
174
175#define OLDINSTR_3(oldinsn, n1, n2, n3) \
176 "# ALT: oldinstr3\n" \
177 "661:\n\t" oldinsn "\n662:\n" \
178 "# ALT: padding3\n" \
179 ".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \
180 " - (" alt_slen ")) > 0) * " \
181 "(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \
182 " - (" alt_slen ")), 0x90\n" \
183 alt_end_marker ":\n"
184
185#define ALTINSTR_ENTRY(feature, num) \
186 " .long 661b - .\n" /* label */ \
187 " .long " b_replacement(num)"f - .\n" /* new instruction */ \
188 " .word " __stringify(feature) "\n" /* feature bit */ \
189 " .byte " alt_total_slen "\n" /* source len */ \
190 " .byte " alt_rlen(num) "\n" /* replacement len */
191
192#define ALTINSTR_REPLACEMENT(newinstr, num) /* replacement */ \
193 "# ALT: replacement " #num "\n" \
194 b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n"
195
196/* alternative assembly primitive: */
197#define ALTERNATIVE(oldinstr, newinstr, feature) \
198 OLDINSTR(oldinstr, 1) \
199 ".pushsection .altinstructions,\"a\"\n" \
200 ALTINSTR_ENTRY(feature, 1) \
201 ".popsection\n" \
202 ".pushsection .altinstr_replacement, \"ax\"\n" \
203 ALTINSTR_REPLACEMENT(newinstr, 1) \
204 ".popsection\n"
205
206#define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
207 OLDINSTR_2(oldinstr, 1, 2) \
208 ".pushsection .altinstructions,\"a\"\n" \
209 ALTINSTR_ENTRY(feature1, 1) \
210 ALTINSTR_ENTRY(feature2, 2) \
211 ".popsection\n" \
212 ".pushsection .altinstr_replacement, \"ax\"\n" \
213 ALTINSTR_REPLACEMENT(newinstr1, 1) \
214 ALTINSTR_REPLACEMENT(newinstr2, 2) \
215 ".popsection\n"
216
217/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
218#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \
219 ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \
220 newinstr_yes, feature)
221
222#define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \
223 OLDINSTR_3(oldinsn, 1, 2, 3) \
224 ".pushsection .altinstructions,\"a\"\n" \
225 ALTINSTR_ENTRY(feat1, 1) \
226 ALTINSTR_ENTRY(feat2, 2) \
227 ALTINSTR_ENTRY(feat3, 3) \
228 ".popsection\n" \
229 ".pushsection .altinstr_replacement, \"ax\"\n" \
230 ALTINSTR_REPLACEMENT(newinsn1, 1) \
231 ALTINSTR_REPLACEMENT(newinsn2, 2) \
232 ALTINSTR_REPLACEMENT(newinsn3, 3) \
233 ".popsection\n"
234
235/*
236 * Alternative instructions for different CPU types or capabilities.
237 *
238 * This allows to use optimized instructions even on generic binary
239 * kernels.
240 *
241 * length of oldinstr must be longer or equal the length of newinstr
242 * It can be padded with nops as needed.
243 *
244 * For non barrier like inlines please define new variants
245 * without volatile and memory clobber.
246 */
247#define alternative(oldinstr, newinstr, feature) \
248 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
249
250#define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
251 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")
252
253#define alternative_ternary(oldinstr, feature, newinstr_yes, newinstr_no) \
254 asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) ::: "memory")
255
256/*
257 * Alternative inline assembly with input.
258 *
259 * Peculiarities:
260 * No memory clobber here.
261 * Argument numbers start with 1.
262 * Leaving an unused argument 0 to keep API compatibility.
263 */
264#define alternative_input(oldinstr, newinstr, feature, input...) \
265 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
266 : : "i" (0), ## input)
267
268/*
269 * This is similar to alternative_input. But it has two features and
270 * respective instructions.
271 *
272 * If CPU has feature2, newinstr2 is used.
273 * Otherwise, if CPU has feature1, newinstr1 is used.
274 * Otherwise, oldinstr is used.
275 */
276#define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \
277 feature2, input...) \
278 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \
279 newinstr2, feature2) \
280 : : "i" (0), ## input)
281
282/* Like alternative_input, but with a single output argument */
283#define alternative_io(oldinstr, newinstr, feature, output, input...) \
284 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
285 : output : "i" (0), ## input)
286
287/* Like alternative_io, but for replacing a direct call with another one. */
288#define alternative_call(oldfunc, newfunc, feature, output, input...) \
289 asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
290 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
291
292/*
293 * Like alternative_call, but there are two features and respective functions.
294 * If CPU has feature2, function2 is used.
295 * Otherwise, if CPU has feature1, function1 is used.
296 * Otherwise, old function is used.
297 */
298#define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \
299 output, input...) \
300 asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\
301 "call %P[new2]", feature2) \
302 : output, ASM_CALL_CONSTRAINT \
303 : [old] "i" (oldfunc), [new1] "i" (newfunc1), \
304 [new2] "i" (newfunc2), ## input)
305
306/*
307 * use this macro(s) if you need more than one output parameter
308 * in alternative_io
309 */
310#define ASM_OUTPUT2(a...) a
311
312/*
313 * use this macro if you need clobbers but no inputs in
314 * alternative_{input,io,call}()
315 */
316#define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr
317
318#else /* __ASSEMBLY__ */
319
320#ifdef CONFIG_SMP
321 .macro LOCK_PREFIX
322672: lock
323 .pushsection .smp_locks,"a"
324 .balign 4
325 .long 672b - .
326 .popsection
327 .endm
328#else
329 .macro LOCK_PREFIX
330 .endm
331#endif
332
333/*
334 * objtool annotation to ignore the alternatives and only consider the original
335 * instruction(s).
336 */
337.macro ANNOTATE_IGNORE_ALTERNATIVE
338 .Lannotate_\@:
339 .pushsection .discard.ignore_alts
340 .long .Lannotate_\@ - .
341 .popsection
342.endm
343
344/*
345 * Issue one struct alt_instr descriptor entry (need to put it into
346 * the section .altinstructions, see below). This entry contains
347 * enough information for the alternatives patching code to patch an
348 * instruction. See apply_alternatives().
349 */
350.macro altinstruction_entry orig alt feature orig_len alt_len
351 .long \orig - .
352 .long \alt - .
353 .word \feature
354 .byte \orig_len
355 .byte \alt_len
356.endm
357
358/*
359 * Define an alternative between two instructions. If @feature is
360 * present, early code in apply_alternatives() replaces @oldinstr with
361 * @newinstr. ".skip" directive takes care of proper instruction padding
362 * in case @newinstr is longer than @oldinstr.
363 */
364.macro ALTERNATIVE oldinstr, newinstr, feature
365140:
366 \oldinstr
367141:
368 .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
369142:
370
371 .pushsection .altinstructions,"a"
372 altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f
373 .popsection
374
375 .pushsection .altinstr_replacement,"ax"
376143:
377 \newinstr
378144:
379 .popsection
380.endm
381
382#define old_len 141b-140b
383#define new_len1 144f-143f
384#define new_len2 145f-144f
385#define new_len3 146f-145f
386
387/*
388 * gas compatible max based on the idea from:
389 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
390 *
391 * The additional "-" is needed because gas uses a "true" value of -1.
392 */
393#define alt_max_2(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
394#define alt_max_3(a, b, c) (alt_max_2(alt_max_2(a, b), c))
395
396
397/*
398 * Same as ALTERNATIVE macro above but for two alternatives. If CPU
399 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
400 * @feature2, it replaces @oldinstr with @feature2.
401 */
402.macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
403140:
404 \oldinstr
405141:
406 .skip -((alt_max_2(new_len1, new_len2) - (old_len)) > 0) * \
407 (alt_max_2(new_len1, new_len2) - (old_len)),0x90
408142:
409
410 .pushsection .altinstructions,"a"
411 altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f
412 altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f
413 .popsection
414
415 .pushsection .altinstr_replacement,"ax"
416143:
417 \newinstr1
418144:
419 \newinstr2
420145:
421 .popsection
422.endm
423
424.macro ALTERNATIVE_3 oldinstr, newinstr1, feature1, newinstr2, feature2, newinstr3, feature3
425140:
426 \oldinstr
427141:
428 .skip -((alt_max_3(new_len1, new_len2, new_len3) - (old_len)) > 0) * \
429 (alt_max_3(new_len1, new_len2, new_len3) - (old_len)),0x90
430142:
431
432 .pushsection .altinstructions,"a"
433 altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f
434 altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f
435 altinstruction_entry 140b,145f,\feature3,142b-140b,146f-145f
436 .popsection
437
438 .pushsection .altinstr_replacement,"ax"
439143:
440 \newinstr1
441144:
442 \newinstr2
443145:
444 \newinstr3
445146:
446 .popsection
447.endm
448
449/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
450#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \
451 ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \
452 newinstr_yes, feature
453
454#endif /* __ASSEMBLY__ */
455
456#endif /* _ASM_X86_ALTERNATIVE_H */