alternative-macros.h (5537B)
1/* SPDX-License-Identifier: GPL-2.0 */ 2#ifndef __ASM_ALTERNATIVE_MACROS_H 3#define __ASM_ALTERNATIVE_MACROS_H 4 5#include <asm/cpucaps.h> 6#include <asm/insn-def.h> 7 8#define ARM64_CB_PATCH ARM64_NCAPS 9 10#ifndef __ASSEMBLY__ 11 12#include <linux/stringify.h> 13 14#define ALTINSTR_ENTRY(feature) \ 15 " .word 661b - .\n" /* label */ \ 16 " .word 663f - .\n" /* new instruction */ \ 17 " .hword " __stringify(feature) "\n" /* feature bit */ \ 18 " .byte 662b-661b\n" /* source len */ \ 19 " .byte 664f-663f\n" /* replacement len */ 20 21#define ALTINSTR_ENTRY_CB(feature, cb) \ 22 " .word 661b - .\n" /* label */ \ 23 " .word " __stringify(cb) "- .\n" /* callback */ \ 24 " .hword " __stringify(feature) "\n" /* feature bit */ \ 25 " .byte 662b-661b\n" /* source len */ \ 26 " .byte 664f-663f\n" /* replacement len */ 27 28/* 29 * alternative assembly primitive: 30 * 31 * If any of these .org directive fail, it means that insn1 and insn2 32 * don't have the same length. This used to be written as 33 * 34 * .if ((664b-663b) != (662b-661b)) 35 * .error "Alternatives instruction length mismatch" 36 * .endif 37 * 38 * but most assemblers die if insn1 or insn2 have a .inst. This should 39 * be fixed in a binutils release posterior to 2.25.51.0.2 (anything 40 * containing commit 4e4d08cf7399b606 or c1baaddf8861). 41 * 42 * Alternatives with callbacks do not generate replacement instructions. 43 */ 44#define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled) \ 45 ".if "__stringify(cfg_enabled)" == 1\n" \ 46 "661:\n\t" \ 47 oldinstr "\n" \ 48 "662:\n" \ 49 ".pushsection .altinstructions,\"a\"\n" \ 50 ALTINSTR_ENTRY(feature) \ 51 ".popsection\n" \ 52 ".subsection 1\n" \ 53 "663:\n\t" \ 54 newinstr "\n" \ 55 "664:\n\t" \ 56 ".org . - (664b-663b) + (662b-661b)\n\t" \ 57 ".org . - (662b-661b) + (664b-663b)\n\t" \ 58 ".previous\n" \ 59 ".endif\n" 60 61#define __ALTERNATIVE_CFG_CB(oldinstr, feature, cfg_enabled, cb) \ 62 ".if "__stringify(cfg_enabled)" == 1\n" \ 63 "661:\n\t" \ 64 oldinstr "\n" \ 65 "662:\n" \ 66 ".pushsection .altinstructions,\"a\"\n" \ 67 ALTINSTR_ENTRY_CB(feature, cb) \ 68 ".popsection\n" \ 69 "663:\n\t" \ 70 "664:\n\t" \ 71 ".endif\n" 72 73#define _ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg, ...) \ 74 __ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg)) 75 76#define ALTERNATIVE_CB(oldinstr, cb) \ 77 __ALTERNATIVE_CFG_CB(oldinstr, ARM64_CB_PATCH, 1, cb) 78#else 79 80#include <asm/assembler.h> 81 82.macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len 83 .word \orig_offset - . 84 .word \alt_offset - . 85 .hword \feature 86 .byte \orig_len 87 .byte \alt_len 88.endm 89 90.macro alternative_insn insn1, insn2, cap, enable = 1 91 .if \enable 92661: \insn1 93662: .pushsection .altinstructions, "a" 94 altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f 95 .popsection 96 .subsection 1 97663: \insn2 98664: .org . - (664b-663b) + (662b-661b) 99 .org . - (662b-661b) + (664b-663b) 100 .previous 101 .endif 102.endm 103 104/* 105 * Alternative sequences 106 * 107 * The code for the case where the capability is not present will be 108 * assembled and linked as normal. There are no restrictions on this 109 * code. 110 * 111 * The code for the case where the capability is present will be 112 * assembled into a special section to be used for dynamic patching. 113 * Code for that case must: 114 * 115 * 1. Be exactly the same length (in bytes) as the default code 116 * sequence. 117 * 118 * 2. Not contain a branch target that is used outside of the 119 * alternative sequence it is defined in (branches into an 120 * alternative sequence are not fixed up). 121 */ 122 123/* 124 * Begin an alternative code sequence. 125 */ 126.macro alternative_if_not cap 127 .set .Lasm_alt_mode, 0 128 .pushsection .altinstructions, "a" 129 altinstruction_entry 661f, 663f, \cap, 662f-661f, 664f-663f 130 .popsection 131661: 132.endm 133 134.macro alternative_if cap 135 .set .Lasm_alt_mode, 1 136 .pushsection .altinstructions, "a" 137 altinstruction_entry 663f, 661f, \cap, 664f-663f, 662f-661f 138 .popsection 139 .subsection 1 140 .align 2 /* So GAS knows label 661 is suitably aligned */ 141661: 142.endm 143 144.macro alternative_cb cb 145 .set .Lasm_alt_mode, 0 146 .pushsection .altinstructions, "a" 147 altinstruction_entry 661f, \cb, ARM64_CB_PATCH, 662f-661f, 0 148 .popsection 149661: 150.endm 151 152/* 153 * Provide the other half of the alternative code sequence. 154 */ 155.macro alternative_else 156662: 157 .if .Lasm_alt_mode==0 158 .subsection 1 159 .else 160 .previous 161 .endif 162663: 163.endm 164 165/* 166 * Complete an alternative code sequence. 167 */ 168.macro alternative_endif 169664: 170 .org . - (664b-663b) + (662b-661b) 171 .org . - (662b-661b) + (664b-663b) 172 .if .Lasm_alt_mode==0 173 .previous 174 .endif 175.endm 176 177/* 178 * Callback-based alternative epilogue 179 */ 180.macro alternative_cb_end 181662: 182.endm 183 184/* 185 * Provides a trivial alternative or default sequence consisting solely 186 * of NOPs. The number of NOPs is chosen automatically to match the 187 * previous case. 188 */ 189.macro alternative_else_nop_endif 190alternative_else 191 nops (662b-661b) / AARCH64_INSN_SIZE 192alternative_endif 193.endm 194 195#define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...) \ 196 alternative_insn insn1, insn2, cap, IS_ENABLED(cfg) 197 198#endif /* __ASSEMBLY__ */ 199 200/* 201 * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature)); 202 * 203 * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature, CONFIG_FOO)); 204 * N.B. If CONFIG_FOO is specified, but not selected, the whole block 205 * will be omitted, including oldinstr. 206 */ 207#define ALTERNATIVE(oldinstr, newinstr, ...) \ 208 _ALTERNATIVE_CFG(oldinstr, newinstr, __VA_ARGS__, 1) 209 210#endif /* __ASM_ALTERNATIVE_MACROS_H */