1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _ASM_X86_ALTERNATIVE_H 3 #define _ASM_X86_ALTERNATIVE_H 4 5 #ifndef __ASSEMBLY__ 6 7 #include <linux/types.h> 8 #include <linux/stddef.h> 9 #include <linux/stringify.h> 10 #include <asm/asm.h> 11 12 /* 13 * Alternative inline assembly for SMP. 14 * 15 * The LOCK_PREFIX macro defined here replaces the LOCK and 16 * LOCK_PREFIX macros used everywhere in the source tree. 17 * 18 * SMP alternatives use the same data structures as the other 19 * alternatives and the X86_FEATURE_UP flag to indicate the case of a 20 * UP system running a SMP kernel. The existing apply_alternatives() 21 * works fine for patching a SMP kernel for UP. 22 * 23 * The SMP alternative tables can be kept after boot and contain both 24 * UP and SMP versions of the instructions to allow switching back to 25 * SMP at runtime, when hotplugging in a new CPU, which is especially 26 * useful in virtualized environments. 27 * 28 * The very common lock prefix is handled as special case in a 29 * separate table which is a pure address list without replacement ptr 30 * and size information. That keeps the table sizes small. 31 */ 32 33 #ifdef CONFIG_SMP 34 #define LOCK_PREFIX_HERE \ 35 ".pushsection .smp_locks,\"a\"\n" \ 36 ".balign 4\n" \ 37 ".long 671f - .\n" /* offset */ \ 38 ".popsection\n" \ 39 "671:" 40 41 #define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; " 42 43 #else /* ! CONFIG_SMP */ 44 #define LOCK_PREFIX_HERE "" 45 #define LOCK_PREFIX "" 46 #endif 47 48 /* 49 * objtool annotation to ignore the alternatives and only consider the original 50 * instruction(s). 51 */ 52 #define ANNOTATE_IGNORE_ALTERNATIVE \ 53 "999:\n\t" \ 54 ".pushsection .discard.ignore_alts\n\t" \ 55 ".long 999b - .\n\t" \ 56 ".popsection\n\t" 57 58 struct alt_instr { 59 s32 instr_offset; /* original instruction */ 60 s32 repl_offset; /* offset to replacement instruction */ 61 u16 cpuid; /* cpuid bit set for replacement */ 62 u8 instrlen; /* length of original instruction */ 63 u8 replacementlen; /* length of new instruction */ 64 u8 padlen; /* length of build-time padding */ 65 } __packed; 66 67 /* 68 * Debug flag that can be tested to see whether alternative 69 * instructions were patched in already: 70 */ 71 extern int alternatives_patched; 72 73 extern void alternative_instructions(void); 74 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end); 75 76 struct module; 77 78 #ifdef CONFIG_SMP 79 extern void alternatives_smp_module_add(struct module *mod, char *name, 80 void *locks, void *locks_end, 81 void *text, void *text_end); 82 extern void alternatives_smp_module_del(struct module *mod); 83 extern void alternatives_enable_smp(void); 84 extern int alternatives_text_reserved(void *start, void *end); 85 extern bool skip_smp_alternatives; 86 #else 87 static inline void alternatives_smp_module_add(struct module *mod, char *name, 88 void *locks, void *locks_end, 89 void *text, void *text_end) {} 90 static inline void alternatives_smp_module_del(struct module *mod) {} 91 static inline void alternatives_enable_smp(void) {} 92 static inline int alternatives_text_reserved(void *start, void *end) 93 { 94 return 0; 95 } 96 #endif /* CONFIG_SMP */ 97 98 #define b_replacement(num) "664"#num 99 #define e_replacement(num) "665"#num 100 101 #define alt_end_marker "663" 102 #define alt_slen "662b-661b" 103 #define alt_pad_len alt_end_marker"b-662b" 104 #define alt_total_slen alt_end_marker"b-661b" 105 #define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f" 106 107 #define OLDINSTR(oldinstr, num) \ 108 "# ALT: oldnstr\n" \ 109 "661:\n\t" oldinstr "\n662:\n" \ 110 "# ALT: padding\n" \ 111 ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \ 112 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" \ 113 alt_end_marker ":\n" 114 115 /* 116 * gas compatible max based on the idea from: 117 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax 118 * 119 * The additional "-" is needed because gas uses a "true" value of -1. 120 */ 121 #define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))" 122 123 /* 124 * Pad the second replacement alternative with additional NOPs if it is 125 * additionally longer than the first replacement alternative. 126 */ 127 #define OLDINSTR_2(oldinstr, num1, num2) \ 128 "# ALT: oldinstr2\n" \ 129 "661:\n\t" oldinstr "\n662:\n" \ 130 "# ALT: padding2\n" \ 131 ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \ 132 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \ 133 alt_end_marker ":\n" 134 135 #define OLDINSTR_3(oldinsn, n1, n2, n3) \ 136 "# ALT: oldinstr3\n" \ 137 "661:\n\t" oldinsn "\n662:\n" \ 138 "# ALT: padding3\n" \ 139 ".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \ 140 " - (" alt_slen ")) > 0) * " \ 141 "(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \ 142 " - (" alt_slen ")), 0x90\n" \ 143 alt_end_marker ":\n" 144 145 #define ALTINSTR_ENTRY(feature, num) \ 146 " .long 661b - .\n" /* label */ \ 147 " .long " b_replacement(num)"f - .\n" /* new instruction */ \ 148 " .word " __stringify(feature) "\n" /* feature bit */ \ 149 " .byte " alt_total_slen "\n" /* source len */ \ 150 " .byte " alt_rlen(num) "\n" /* replacement len */ \ 151 " .byte " alt_pad_len "\n" /* pad len */ 152 153 #define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \ 154 "# ALT: replacement " #num "\n" \ 155 b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n" 156 157 /* alternative assembly primitive: */ 158 #define ALTERNATIVE(oldinstr, newinstr, feature) \ 159 OLDINSTR(oldinstr, 1) \ 160 ".pushsection .altinstructions,\"a\"\n" \ 161 ALTINSTR_ENTRY(feature, 1) \ 162 ".popsection\n" \ 163 ".pushsection .altinstr_replacement, \"ax\"\n" \ 164 ALTINSTR_REPLACEMENT(newinstr, feature, 1) \ 165 ".popsection\n" 166 167 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\ 168 OLDINSTR_2(oldinstr, 1, 2) \ 169 ".pushsection .altinstructions,\"a\"\n" \ 170 ALTINSTR_ENTRY(feature1, 1) \ 171 ALTINSTR_ENTRY(feature2, 2) \ 172 ".popsection\n" \ 173 ".pushsection .altinstr_replacement, \"ax\"\n" \ 174 ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \ 175 ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \ 176 ".popsection\n" 177 178 #define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \ 179 OLDINSTR_3(oldinsn, 1, 2, 3) \ 180 ".pushsection .altinstructions,\"a\"\n" \ 181 ALTINSTR_ENTRY(feat1, 1) \ 182 ALTINSTR_ENTRY(feat2, 2) \ 183 ALTINSTR_ENTRY(feat3, 3) \ 184 ".popsection\n" \ 185 ".pushsection .altinstr_replacement, \"ax\"\n" \ 186 ALTINSTR_REPLACEMENT(newinsn1, feat1, 1) \ 187 ALTINSTR_REPLACEMENT(newinsn2, feat2, 2) \ 188 ALTINSTR_REPLACEMENT(newinsn3, feat3, 3) \ 189 ".popsection\n" 190 191 /* 192 * Alternative instructions for different CPU types or capabilities. 193 * 194 * This allows to use optimized instructions even on generic binary 195 * kernels. 196 * 197 * length of oldinstr must be longer or equal the length of newinstr 198 * It can be padded with nops as needed. 199 * 200 * For non barrier like inlines please define new variants 201 * without volatile and memory clobber. 202 */ 203 #define alternative(oldinstr, newinstr, feature) \ 204 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory") 205 206 #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \ 207 asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory") 208 209 /* 210 * Alternative inline assembly with input. 211 * 212 * Peculiarities: 213 * No memory clobber here. 214 * Argument numbers start with 1. 215 * Best is to use constraints that are fixed size (like (%1) ... "r") 216 * If you use variable sized constraints like "m" or "g" in the 217 * replacement make sure to pad to the worst case length. 218 * Leaving an unused argument 0 to keep API compatibility. 219 */ 220 #define alternative_input(oldinstr, newinstr, feature, input...) \ 221 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 222 : : "i" (0), ## input) 223 224 /* 225 * This is similar to alternative_input. But it has two features and 226 * respective instructions. 227 * 228 * If CPU has feature2, newinstr2 is used. 229 * Otherwise, if CPU has feature1, newinstr1 is used. 230 * Otherwise, oldinstr is used. 231 */ 232 #define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \ 233 feature2, input...) \ 234 asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \ 235 newinstr2, feature2) \ 236 : : "i" (0), ## input) 237 238 /* Like alternative_input, but with a single output argument */ 239 #define alternative_io(oldinstr, newinstr, feature, output, input...) \ 240 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 241 : output : "i" (0), ## input) 242 243 /* Like alternative_io, but for replacing a direct call with another one. */ 244 #define alternative_call(oldfunc, newfunc, feature, output, input...) \ 245 asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \ 246 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input) 247 248 /* 249 * Like alternative_call, but there are two features and respective functions. 250 * If CPU has feature2, function2 is used. 251 * Otherwise, if CPU has feature1, function1 is used. 252 * Otherwise, old function is used. 253 */ 254 #define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \ 255 output, input...) \ 256 asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\ 257 "call %P[new2]", feature2) \ 258 : output, ASM_CALL_CONSTRAINT \ 259 : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ 260 [new2] "i" (newfunc2), ## input) 261 262 /* 263 * use this macro(s) if you need more than one output parameter 264 * in alternative_io 265 */ 266 #define ASM_OUTPUT2(a...) a 267 268 /* 269 * use this macro if you need clobbers but no inputs in 270 * alternative_{input,io,call}() 271 */ 272 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr 273 274 #endif /* __ASSEMBLY__ */ 275 276 #endif /* _ASM_X86_ALTERNATIVE_H */ 277