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 struct alt_instr { 49 s32 instr_offset; /* original instruction */ 50 s32 repl_offset; /* offset to replacement instruction */ 51 u16 cpuid; /* cpuid bit set for replacement */ 52 u8 instrlen; /* length of original instruction */ 53 u8 replacementlen; /* length of new instruction */ 54 u8 padlen; /* length of build-time padding */ 55 } __packed; 56 57 /* 58 * Debug flag that can be tested to see whether alternative 59 * instructions were patched in already: 60 */ 61 extern int alternatives_patched; 62 63 extern void alternative_instructions(void); 64 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end); 65 66 struct module; 67 68 #ifdef CONFIG_SMP 69 extern void alternatives_smp_module_add(struct module *mod, char *name, 70 void *locks, void *locks_end, 71 void *text, void *text_end); 72 extern void alternatives_smp_module_del(struct module *mod); 73 extern void alternatives_enable_smp(void); 74 extern int alternatives_text_reserved(void *start, void *end); 75 extern bool skip_smp_alternatives; 76 #else 77 static inline void alternatives_smp_module_add(struct module *mod, char *name, 78 void *locks, void *locks_end, 79 void *text, void *text_end) {} 80 static inline void alternatives_smp_module_del(struct module *mod) {} 81 static inline void alternatives_enable_smp(void) {} 82 static inline int alternatives_text_reserved(void *start, void *end) 83 { 84 return 0; 85 } 86 #endif /* CONFIG_SMP */ 87 88 #define b_replacement(num) "664"#num 89 #define e_replacement(num) "665"#num 90 91 #define alt_end_marker "663" 92 #define alt_slen "662b-661b" 93 #define alt_pad_len alt_end_marker"b-662b" 94 #define alt_total_slen alt_end_marker"b-661b" 95 #define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f" 96 97 #define __OLDINSTR(oldinstr, num) \ 98 "661:\n\t" oldinstr "\n662:\n" \ 99 ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \ 100 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" 101 102 #define OLDINSTR(oldinstr, num) \ 103 __OLDINSTR(oldinstr, num) \ 104 alt_end_marker ":\n" 105 106 /* 107 * gas compatible max based on the idea from: 108 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax 109 * 110 * The additional "-" is needed because gas uses a "true" value of -1. 111 */ 112 #define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))" 113 114 /* 115 * Pad the second replacement alternative with additional NOPs if it is 116 * additionally longer than the first replacement alternative. 117 */ 118 #define OLDINSTR_2(oldinstr, num1, num2) \ 119 "661:\n\t" oldinstr "\n662:\n" \ 120 ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \ 121 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \ 122 alt_end_marker ":\n" 123 124 #define ALTINSTR_ENTRY(feature, num) \ 125 " .long 661b - .\n" /* label */ \ 126 " .long " b_replacement(num)"f - .\n" /* new instruction */ \ 127 " .word " __stringify(feature) "\n" /* feature bit */ \ 128 " .byte " alt_total_slen "\n" /* source len */ \ 129 " .byte " alt_rlen(num) "\n" /* replacement len */ \ 130 " .byte " alt_pad_len "\n" /* pad len */ 131 132 #define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \ 133 b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n\t" 134 135 /* alternative assembly primitive: */ 136 #define ALTERNATIVE(oldinstr, newinstr, feature) \ 137 OLDINSTR(oldinstr, 1) \ 138 ".pushsection .altinstructions,\"a\"\n" \ 139 ALTINSTR_ENTRY(feature, 1) \ 140 ".popsection\n" \ 141 ".pushsection .altinstr_replacement, \"ax\"\n" \ 142 ALTINSTR_REPLACEMENT(newinstr, feature, 1) \ 143 ".popsection\n" 144 145 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\ 146 OLDINSTR_2(oldinstr, 1, 2) \ 147 ".pushsection .altinstructions,\"a\"\n" \ 148 ALTINSTR_ENTRY(feature1, 1) \ 149 ALTINSTR_ENTRY(feature2, 2) \ 150 ".popsection\n" \ 151 ".pushsection .altinstr_replacement, \"ax\"\n" \ 152 ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \ 153 ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \ 154 ".popsection\n" 155 156 /* 157 * Alternative instructions for different CPU types or capabilities. 158 * 159 * This allows to use optimized instructions even on generic binary 160 * kernels. 161 * 162 * length of oldinstr must be longer or equal the length of newinstr 163 * It can be padded with nops as needed. 164 * 165 * For non barrier like inlines please define new variants 166 * without volatile and memory clobber. 167 */ 168 #define alternative(oldinstr, newinstr, feature) \ 169 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory") 170 171 #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \ 172 asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory") 173 174 /* 175 * Alternative inline assembly with input. 176 * 177 * Pecularities: 178 * No memory clobber here. 179 * Argument numbers start with 1. 180 * Best is to use constraints that are fixed size (like (%1) ... "r") 181 * If you use variable sized constraints like "m" or "g" in the 182 * replacement make sure to pad to the worst case length. 183 * Leaving an unused argument 0 to keep API compatibility. 184 */ 185 #define alternative_input(oldinstr, newinstr, feature, input...) \ 186 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 187 : : "i" (0), ## input) 188 189 /* 190 * This is similar to alternative_input. But it has two features and 191 * respective instructions. 192 * 193 * If CPU has feature2, newinstr2 is used. 194 * Otherwise, if CPU has feature1, newinstr1 is used. 195 * Otherwise, oldinstr is used. 196 */ 197 #define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \ 198 feature2, input...) \ 199 asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \ 200 newinstr2, feature2) \ 201 : : "i" (0), ## input) 202 203 /* Like alternative_input, but with a single output argument */ 204 #define alternative_io(oldinstr, newinstr, feature, output, input...) \ 205 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 206 : output : "i" (0), ## input) 207 208 /* Like alternative_io, but for replacing a direct call with another one. */ 209 #define alternative_call(oldfunc, newfunc, feature, output, input...) \ 210 asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \ 211 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input) 212 213 /* 214 * Like alternative_call, but there are two features and respective functions. 215 * If CPU has feature2, function2 is used. 216 * Otherwise, if CPU has feature1, function1 is used. 217 * Otherwise, old function is used. 218 */ 219 #define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \ 220 output, input...) \ 221 asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\ 222 "call %P[new2]", feature2) \ 223 : output, ASM_CALL_CONSTRAINT \ 224 : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ 225 [new2] "i" (newfunc2), ## input) 226 227 /* 228 * use this macro(s) if you need more than one output parameter 229 * in alternative_io 230 */ 231 #define ASM_OUTPUT2(a...) a 232 233 /* 234 * use this macro if you need clobbers but no inputs in 235 * alternative_{input,io,call}() 236 */ 237 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr 238 239 #endif /* __ASSEMBLY__ */ 240 241 #endif /* _ASM_X86_ALTERNATIVE_H */ 242