diff options
Diffstat (limited to 'arch/x86/include/asm/alternative-asm.h')
| -rw-r--r-- | arch/x86/include/asm/alternative-asm.h | 103 |
1 files changed, 103 insertions, 0 deletions
diff --git a/arch/x86/include/asm/alternative-asm.h b/arch/x86/include/asm/alternative-asm.h new file mode 100644 index 000000000..31b627b43 --- /dev/null +++ b/arch/x86/include/asm/alternative-asm.h @@ -0,0 +1,103 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_X86_ALTERNATIVE_ASM_H +#define _ASM_X86_ALTERNATIVE_ASM_H + +#ifdef __ASSEMBLY__ + +#include <asm/asm.h> + +#ifdef CONFIG_SMP + .macro LOCK_PREFIX +672: lock + .pushsection .smp_locks,"a" + .balign 4 + .long 672b - . + .popsection + .endm +#else + .macro LOCK_PREFIX + .endm +#endif + +/* + * Issue one struct alt_instr descriptor entry (need to put it into + * the section .altinstructions, see below). This entry contains + * enough information for the alternatives patching code to patch an + * instruction. See apply_alternatives(). + */ +.macro altinstruction_entry orig alt feature orig_len alt_len pad_len + .long \orig - . + .long \alt - . + .word \feature + .byte \orig_len + .byte \alt_len + .byte \pad_len +.endm + +/* + * Define an alternative between two instructions. If @feature is + * present, early code in apply_alternatives() replaces @oldinstr with + * @newinstr. ".skip" directive takes care of proper instruction padding + * in case @newinstr is longer than @oldinstr. + */ +.macro ALTERNATIVE oldinstr, newinstr, feature +140: + \oldinstr +141: + .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90 +142: + + .pushsection .altinstructions,"a" + altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f,142b-141b + .popsection + + .pushsection .altinstr_replacement,"ax" +143: + \newinstr +144: + .popsection +.endm + +#define old_len 141b-140b +#define new_len1 144f-143f +#define new_len2 145f-144f + +/* + * gas compatible max based on the idea from: + * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax + * + * The additional "-" is needed because gas uses a "true" value of -1. + */ +#define alt_max_short(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b))))) + + +/* + * Same as ALTERNATIVE macro above but for two alternatives. If CPU + * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has + * @feature2, it replaces @oldinstr with @feature2. + */ +.macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2 +140: + \oldinstr +141: + .skip -((alt_max_short(new_len1, new_len2) - (old_len)) > 0) * \ + (alt_max_short(new_len1, new_len2) - (old_len)),0x90 +142: + + .pushsection .altinstructions,"a" + altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f,142b-141b + altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f,142b-141b + .popsection + + .pushsection .altinstr_replacement,"ax" +143: + \newinstr1 +144: + \newinstr2 +145: + .popsection +.endm + +#endif /* __ASSEMBLY__ */ + +#endif /* _ASM_X86_ALTERNATIVE_ASM_H */ |