diff options
Diffstat (limited to 'arch/arm64/include')
| -rw-r--r-- | arch/arm64/include/asm/alternative.h | 70 |
1 files changed, 53 insertions, 17 deletions
diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h index 8746ff6abd77..55101bd86b98 100644 --- a/arch/arm64/include/asm/alternative.h +++ b/arch/arm64/include/asm/alternative.h @@ -2,6 +2,7 @@ #define __ASM_ALTERNATIVE_H #include <asm/cpufeature.h> +#include <asm/insn.h> #ifndef __ASSEMBLY__ @@ -90,34 +91,55 @@ void apply_alternatives(void *start, size_t length); .endm /* - * Begin an alternative code sequence. + * Alternative sequences + * + * The code for the case where the capability is not present will be + * assembled and linked as normal. There are no restrictions on this + * code. + * + * The code for the case where the capability is present will be + * assembled into a special section to be used for dynamic patching. + * Code for that case must: + * + * 1. Be exactly the same length (in bytes) as the default code + * sequence. * - * The code that follows this macro will be assembled and linked as - * normal. There are no restrictions on this code. + * 2. Not contain a branch target that is used outside of the + * alternative sequence it is defined in (branches into an + * alternative sequence are not fixed up). + */ + +/* + * Begin an alternative code sequence. */ .macro alternative_if_not cap + .set .Lasm_alt_mode, 0 .pushsection .altinstructions, "a" altinstruction_entry 661f, 663f, \cap, 662f-661f, 664f-663f .popsection 661: .endm +.macro alternative_if cap + .set .Lasm_alt_mode, 1 + .pushsection .altinstructions, "a" + altinstruction_entry 663f, 661f, \cap, 664f-663f, 662f-661f + .popsection + .pushsection .altinstr_replacement, "ax" + .align 2 /* So GAS knows label 661 is suitably aligned */ +661: +.endm + /* - * Provide the alternative code sequence. - * - * The code that follows this macro is assembled into a special - * section to be used for dynamic patching. Code that follows this - * macro must: - * - * 1. Be exactly the same length (in bytes) as the default code - * sequence. - * - * 2. Not contain a branch target that is used outside of the - * alternative sequence it is defined in (branches into an - * alternative sequence are not fixed up). + * Provide the other half of the alternative code sequence. */ .macro alternative_else -662: .pushsection .altinstr_replacement, "ax" +662: + .if .Lasm_alt_mode==0 + .pushsection .altinstr_replacement, "ax" + .else + .popsection + .endif 663: .endm @@ -125,11 +147,25 @@ void apply_alternatives(void *start, size_t length); * Complete an alternative code sequence. */ .macro alternative_endif -664: .popsection +664: + .if .Lasm_alt_mode==0 + .popsection + .endif .org . - (664b-663b) + (662b-661b) .org . - (662b-661b) + (664b-663b) .endm +/* + * Provides a trivial alternative or default sequence consisting solely + * of NOPs. The number of NOPs is chosen automatically to match the + * previous case. + */ +.macro alternative_else_nop_endif +alternative_else + nops (662b-661b) / AARCH64_INSN_SIZE +alternative_endif +.endm + #define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...) \ alternative_insn insn1, insn2, cap, IS_ENABLED(cfg) |