1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef __ASM_ALTERNATIVE_MACROS_H 3 #define __ASM_ALTERNATIVE_MACROS_H 4 5 #include <linux/const.h> 6 #include <vdso/bits.h> 7 8 #include <asm/cpucaps.h> 9 #include <asm/insn-def.h> 10 11 /* 12 * Binutils 2.27.0 can't handle a 'UL' suffix on constants, so for the assembly 13 * macros below we must use we must use `(1 << ARM64_CB_SHIFT)`. 14 */ 15 #define ARM64_CB_SHIFT 15 16 #define ARM64_CB_BIT BIT(ARM64_CB_SHIFT) 17 18 #if ARM64_NCAPS >= ARM64_CB_BIT 19 #error "cpucaps have overflown ARM64_CB_BIT" 20 #endif 21 22 #ifndef __ASSEMBLY__ 23 24 #include <linux/stringify.h> 25 26 #define ALTINSTR_ENTRY(feature) \ 27 " .word 661b - .\n" /* label */ \ 28 " .word 663f - .\n" /* new instruction */ \ 29 " .hword " __stringify(feature) "\n" /* feature bit */ \ 30 " .byte 662b-661b\n" /* source len */ \ 31 " .byte 664f-663f\n" /* replacement len */ 32 33 #define ALTINSTR_ENTRY_CB(feature, cb) \ 34 " .word 661b - .\n" /* label */ \ 35 " .word " __stringify(cb) "- .\n" /* callback */ \ 36 " .hword " __stringify(feature) "\n" /* feature bit */ \ 37 " .byte 662b-661b\n" /* source len */ \ 38 " .byte 664f-663f\n" /* replacement len */ 39 40 /* 41 * alternative assembly primitive: 42 * 43 * If any of these .org directive fail, it means that insn1 and insn2 44 * don't have the same length. This used to be written as 45 * 46 * .if ((664b-663b) != (662b-661b)) 47 * .error "Alternatives instruction length mismatch" 48 * .endif 49 * 50 * but most assemblers die if insn1 or insn2 have a .inst. This should 51 * be fixed in a binutils release posterior to 2.25.51.0.2 (anything 52 * containing commit 4e4d08cf7399b606 or c1baaddf8861). 53 * 54 * Alternatives with callbacks do not generate replacement instructions. 55 */ 56 #define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled) \ 57 ".if "__stringify(cfg_enabled)" == 1\n" \ 58 "661:\n\t" \ 59 oldinstr "\n" \ 60 "662:\n" \ 61 ".pushsection .altinstructions,\"a\"\n" \ 62 ALTINSTR_ENTRY(feature) \ 63 ".popsection\n" \ 64 ".subsection 1\n" \ 65 "663:\n\t" \ 66 newinstr "\n" \ 67 "664:\n\t" \ 68 ".org . - (664b-663b) + (662b-661b)\n\t" \ 69 ".org . - (662b-661b) + (664b-663b)\n\t" \ 70 ".previous\n" \ 71 ".endif\n" 72 73 #define __ALTERNATIVE_CFG_CB(oldinstr, feature, cfg_enabled, cb) \ 74 ".if "__stringify(cfg_enabled)" == 1\n" \ 75 "661:\n\t" \ 76 oldinstr "\n" \ 77 "662:\n" \ 78 ".pushsection .altinstructions,\"a\"\n" \ 79 ALTINSTR_ENTRY_CB(feature, cb) \ 80 ".popsection\n" \ 81 "663:\n\t" \ 82 "664:\n\t" \ 83 ".endif\n" 84 85 #define _ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg, ...) \ 86 __ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg)) 87 88 #define ALTERNATIVE_CB(oldinstr, feature, cb) \ 89 __ALTERNATIVE_CFG_CB(oldinstr, (1 << ARM64_CB_SHIFT) | (feature), 1, cb) 90 #else 91 92 #include <asm/assembler.h> 93 94 .macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len 95 .word \orig_offset - . 96 .word \alt_offset - . 97 .hword (\feature) 98 .byte \orig_len 99 .byte \alt_len 100 .endm 101 102 .macro alternative_insn insn1, insn2, cap, enable = 1 103 .if \enable 104 661: \insn1 105 662: .pushsection .altinstructions, "a" 106 altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f 107 .popsection 108 .subsection 1 109 663: \insn2 110 664: .org . - (664b-663b) + (662b-661b) 111 .org . - (662b-661b) + (664b-663b) 112 .previous 113 .endif 114 .endm 115 116 /* 117 * Alternative sequences 118 * 119 * The code for the case where the capability is not present will be 120 * assembled and linked as normal. There are no restrictions on this 121 * code. 122 * 123 * The code for the case where the capability is present will be 124 * assembled into a special section to be used for dynamic patching. 125 * Code for that case must: 126 * 127 * 1. Be exactly the same length (in bytes) as the default code 128 * sequence. 129 * 130 * 2. Not contain a branch target that is used outside of the 131 * alternative sequence it is defined in (branches into an 132 * alternative sequence are not fixed up). 133 */ 134 135 /* 136 * Begin an alternative code sequence. 137 */ 138 .macro alternative_if_not cap 139 .set .Lasm_alt_mode, 0 140 .pushsection .altinstructions, "a" 141 altinstruction_entry 661f, 663f, \cap, 662f-661f, 664f-663f 142 .popsection 143 661: 144 .endm 145 146 .macro alternative_if cap 147 .set .Lasm_alt_mode, 1 148 .pushsection .altinstructions, "a" 149 altinstruction_entry 663f, 661f, \cap, 664f-663f, 662f-661f 150 .popsection 151 .subsection 1 152 .align 2 /* So GAS knows label 661 is suitably aligned */ 153 661: 154 .endm 155 156 .macro alternative_cb cap, cb 157 .set .Lasm_alt_mode, 0 158 .pushsection .altinstructions, "a" 159 altinstruction_entry 661f, \cb, (1 << ARM64_CB_SHIFT) | \cap, 662f-661f, 0 160 .popsection 161 661: 162 .endm 163 164 /* 165 * Provide the other half of the alternative code sequence. 166 */ 167 .macro alternative_else 168 662: 169 .if .Lasm_alt_mode==0 170 .subsection 1 171 .else 172 .previous 173 .endif 174 663: 175 .endm 176 177 /* 178 * Complete an alternative code sequence. 179 */ 180 .macro alternative_endif 181 664: 182 .org . - (664b-663b) + (662b-661b) 183 .org . - (662b-661b) + (664b-663b) 184 .if .Lasm_alt_mode==0 185 .previous 186 .endif 187 .endm 188 189 /* 190 * Callback-based alternative epilogue 191 */ 192 .macro alternative_cb_end 193 662: 194 .endm 195 196 /* 197 * Provides a trivial alternative or default sequence consisting solely 198 * of NOPs. The number of NOPs is chosen automatically to match the 199 * previous case. 200 */ 201 .macro alternative_else_nop_endif 202 alternative_else 203 nops (662b-661b) / AARCH64_INSN_SIZE 204 alternative_endif 205 .endm 206 207 #define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...) \ 208 alternative_insn insn1, insn2, cap, IS_ENABLED(cfg) 209 210 #endif /* __ASSEMBLY__ */ 211 212 /* 213 * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature)); 214 * 215 * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature, CONFIG_FOO)); 216 * N.B. If CONFIG_FOO is specified, but not selected, the whole block 217 * will be omitted, including oldinstr. 218 */ 219 #define ALTERNATIVE(oldinstr, newinstr, ...) \ 220 _ALTERNATIVE_CFG(oldinstr, newinstr, __VA_ARGS__, 1) 221 222 #ifndef __ASSEMBLY__ 223 224 #include <linux/types.h> 225 226 static __always_inline bool 227 alternative_has_feature_likely(const unsigned long feature) 228 { 229 compiletime_assert(feature < ARM64_NCAPS, 230 "feature must be < ARM64_NCAPS"); 231 232 asm_volatile_goto( 233 ALTERNATIVE_CB("b %l[l_no]", %[feature], alt_cb_patch_nops) 234 : 235 : [feature] "i" (feature) 236 : 237 : l_no); 238 239 return true; 240 l_no: 241 return false; 242 } 243 244 static __always_inline bool 245 alternative_has_feature_unlikely(const unsigned long feature) 246 { 247 compiletime_assert(feature < ARM64_NCAPS, 248 "feature must be < ARM64_NCAPS"); 249 250 asm_volatile_goto( 251 ALTERNATIVE("nop", "b %l[l_yes]", %[feature]) 252 : 253 : [feature] "i" (feature) 254 : 255 : l_yes); 256 257 return false; 258 l_yes: 259 return true; 260 } 261 262 #endif /* __ASSEMBLY__ */ 263 264 #endif /* __ASM_ALTERNATIVE_MACROS_H */ 265