1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_X86_ALTERNATIVE_ASM_H
3 #define _ASM_X86_ALTERNATIVE_ASM_H
12 .pushsection .smp_locks,"a"
23 * objtool annotation to ignore the alternatives and only consider the original
26 .macro ANNOTATE_IGNORE_ALTERNATIVE
28 .pushsection .discard.ignore_alts
29 .long .Lannotate_\@ - .
34 * Issue one struct alt_instr descriptor entry (need to put it into
35 * the section .altinstructions, see below). This entry contains
36 * enough information for the alternatives patching code to patch an
37 * instruction. See apply_alternatives().
39 .macro altinstruction_entry orig alt feature orig_len alt_len pad_len
49 * Define an alternative between two instructions. If @feature is
50 * present, early code in apply_alternatives() replaces @oldinstr with
51 * @newinstr. ".skip" directive takes care of proper instruction padding
52 * in case @newinstr is longer than @oldinstr.
54 .macro ALTERNATIVE oldinstr, newinstr, feature
58 .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
61 .pushsection .altinstructions,"a"
62 altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f,142b-141b
65 .pushsection .altinstr_replacement,"ax"
72 #define old_len 141b-140b
73 #define new_len1 144f-143f
74 #define new_len2 145f-144f
77 * gas compatible max based on the idea from:
78 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
80 * The additional "-" is needed because gas uses a "true" value of -1.
82 #define alt_max_short(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
86 * Same as ALTERNATIVE macro above but for two alternatives. If CPU
87 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
88 * @feature2, it replaces @oldinstr with @feature2.
90 .macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
94 .skip -((alt_max_short(new_len1, new_len2) - (old_len)) > 0) * \
95 (alt_max_short(new_len1, new_len2) - (old_len)),0x90
98 .pushsection .altinstructions,"a"
99 altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f,142b-141b
100 altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f,142b-141b
103 .pushsection .altinstr_replacement,"ax"
112 #endif /* __ASSEMBLY__ */
114 #endif /* _ASM_X86_ALTERNATIVE_ASM_H */