/* SPDX-License-Identifier: GPL-2.0 */ #ifndef __ASM_ALTERNATIVE_H #define __ASM_ALTERNATIVE_H #include #include #ifndef __ASSEMBLY__ #include #include #include #include struct alt_instr { s32 orig_offset; /* offset to original instruction */ s32 alt_offset; /* offset to replacement instruction */ u16 cpufeature; /* cpufeature bit set for replacement */ u8 orig_len; /* size of original instruction(s) */ u8 alt_len; /* size of new instruction(s), <= orig_len */ }; void __init apply_alternatives_all(void); void apply_alternatives(void *start, size_t length); #define ALTINSTR_ENTRY(feature) \ " .word 661b - .\n" /* label */ \ " .word 663f - .\n" /* new instruction */ \ " .hword " __stringify(feature) "\n" /* feature bit */ \ " .byte 662b-661b\n" /* source len */ \ " .byte 664f-663f\n" /* replacement len */ /* * alternative assembly primitive: * * If any of these .org directive fail, it means that insn1 and insn2 * don't have the same length. This used to be written as * * .if ((664b-663b) != (662b-661b)) * .error "Alternatives instruction length mismatch" * .endif * * but most assemblers die if insn1 or insn2 have a .inst. This should * be fixed in a binutils release posterior to 2.25.51.0.2 (anything * containing commit 4e4d08cf7399b606 or c1baaddf8861). */ #define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled) \ ".if "__stringify(cfg_enabled)" == 1\n" \ "661:\n\t" \ oldinstr "\n" \ "662:\n" \ ".pushsection .altinstructions,\"a\"\n" \ ALTINSTR_ENTRY(feature) \ ".popsection\n" \ ".pushsection .altinstr_replacement, \"a\"\n" \ "663:\n\t" \ newinstr "\n" \ "664:\n\t" \ ".popsection\n\t" \ ".org . - (664b-663b) + (662b-661b)\n\t" \ ".org . - (662b-661b) + (664b-663b)\n" \ ".endif\n" #define _ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg, ...) \ __ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg)) #else #include .macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len .word \orig_offset - . .word \alt_offset - . .hword \feature .byte \orig_len .byte \alt_len .endm .macro alternative_insn insn1, insn2, cap, enable = 1 .if \enable 661: \insn1 662: .pushsection .altinstructions, "a" altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f .popsection .pushsection .altinstr_replacement, "ax" 663: \insn2 664: .popsection .org . - (664b-663b) + (662b-661b) .org . - (662b-661b) + (664b-663b) .endif .endm /* * 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. * * 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 other half of the alternative code sequence. */ .macro alternative_else 662: .if .Lasm_alt_mode==0 .pushsection .altinstr_replacement, "ax" .else .popsection .endif 663: .endm /* * Complete an alternative code sequence. */ .macro alternative_endif 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) .macro user_alt, label, oldinstr, newinstr, cond 9999: alternative_insn "\oldinstr", "\newinstr", \cond _ASM_EXTABLE 9999b, \label .endm /* * Generate the assembly for UAO alternatives with exception table entries. * This is complicated as there is no post-increment or pair versions of the * unprivileged instructions, and USER() only works for single instructions. */ #ifdef CONFIG_ARM64_UAO .macro uao_ldp l, reg1, reg2, addr, post_inc alternative_if_not ARM64_HAS_UAO 8888: ldp \reg1, \reg2, [\addr], \post_inc; 8889: nop; nop; alternative_else ldtr \reg1, [\addr]; ldtr \reg2, [\addr, #8]; add \addr, \addr, \post_inc; alternative_endif _asm_extable 8888b,\l; _asm_extable 8889b,\l; .endm .macro uao_stp l, reg1, reg2, addr, post_inc alternative_if_not ARM64_HAS_UAO 8888: stp \reg1, \reg2, [\addr], \post_inc; 8889: nop; nop; alternative_else sttr \reg1, [\addr]; sttr \reg2, [\addr, #8]; add \addr, \addr, \post_inc; alternative_endif _asm_extable 8888b,\l; _asm_extable 8889b,\l; .endm .macro uao_user_alternative l, inst, alt_inst, reg, addr, post_inc alternative_if_not ARM64_HAS_UAO 8888: \inst \reg, [\addr], \post_inc; nop; alternative_else \alt_inst \reg, [\addr]; add \addr, \addr, \post_inc; alternative_endif _asm_extable 8888b,\l; .endm #else .macro uao_ldp l, reg1, reg2, addr, post_inc USER(\l, ldp \reg1, \reg2, [\addr], \post_inc) .endm .macro uao_stp l, reg1, reg2, addr, post_inc USER(\l, stp \reg1, \reg2, [\addr], \post_inc) .endm .macro uao_user_alternative l, inst, alt_inst, reg, addr, post_inc USER(\l, \inst \reg, [\addr], \post_inc) .endm #endif #endif /* __ASSEMBLY__ */ /* * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature)); * * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature, CONFIG_FOO)); * N.B. If CONFIG_FOO is specified, but not selected, the whole block * will be omitted, including oldinstr. */ #define ALTERNATIVE(oldinstr, newinstr, ...) \ _ALTERNATIVE_CFG(oldinstr, newinstr, __VA_ARGS__, 1) #endif /* __ASM_ALTERNATIVE_H */