1 #ifndef _ASM_X86_ALTERNATIVE_H 2 #define _ASM_X86_ALTERNATIVE_H 3 4 #ifndef __ASSEMBLY__ 5 6 #include <linux/types.h> 7 #include <linux/stddef.h> 8 #include <linux/stringify.h> 9 #include <asm/asm.h> 10 11 /* 12 * Alternative inline assembly for SMP. 13 * 14 * The LOCK_PREFIX macro defined here replaces the LOCK and 15 * LOCK_PREFIX macros used everywhere in the source tree. 16 * 17 * SMP alternatives use the same data structures as the other 18 * alternatives and the X86_FEATURE_UP flag to indicate the case of a 19 * UP system running a SMP kernel. The existing apply_alternatives() 20 * works fine for patching a SMP kernel for UP. 21 * 22 * The SMP alternative tables can be kept after boot and contain both 23 * UP and SMP versions of the instructions to allow switching back to 24 * SMP at runtime, when hotplugging in a new CPU, which is especially 25 * useful in virtualized environments. 26 * 27 * The very common lock prefix is handled as special case in a 28 * separate table which is a pure address list without replacement ptr 29 * and size information. That keeps the table sizes small. 30 */ 31 32 #ifdef CONFIG_SMP 33 #define LOCK_PREFIX_HERE \ 34 ".pushsection .smp_locks,\"a\"\n" \ 35 ".balign 4\n" \ 36 ".long 671f - .\n" /* offset */ \ 37 ".popsection\n" \ 38 "671:" 39 40 #define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; " 41 42 #else /* ! CONFIG_SMP */ 43 #define LOCK_PREFIX_HERE "" 44 #define LOCK_PREFIX "" 45 #endif 46 47 struct alt_instr { 48 s32 instr_offset; /* original instruction */ 49 s32 repl_offset; /* offset to replacement instruction */ 50 u16 cpuid; /* cpuid bit set for replacement */ 51 u8 instrlen; /* length of original instruction */ 52 u8 replacementlen; /* length of new instruction */ 53 u8 padlen; /* length of build-time padding */ 54 } __packed; 55 56 /* 57 * Debug flag that can be tested to see whether alternative 58 * instructions were patched in already: 59 */ 60 extern int alternatives_patched; 61 62 extern void alternative_instructions(void); 63 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end); 64 65 struct module; 66 67 #ifdef CONFIG_SMP 68 extern void alternatives_smp_module_add(struct module *mod, char *name, 69 void *locks, void *locks_end, 70 void *text, void *text_end); 71 extern void alternatives_smp_module_del(struct module *mod); 72 extern void alternatives_enable_smp(void); 73 extern int alternatives_text_reserved(void *start, void *end); 74 extern bool skip_smp_alternatives; 75 #else 76 static inline void alternatives_smp_module_add(struct module *mod, char *name, 77 void *locks, void *locks_end, 78 void *text, void *text_end) {} 79 static inline void alternatives_smp_module_del(struct module *mod) {} 80 static inline void alternatives_enable_smp(void) {} 81 static inline int alternatives_text_reserved(void *start, void *end) 82 { 83 return 0; 84 } 85 #endif /* CONFIG_SMP */ 86 87 #define b_replacement(num) "664"#num 88 #define e_replacement(num) "665"#num 89 90 #define alt_end_marker "663" 91 #define alt_slen "662b-661b" 92 #define alt_pad_len alt_end_marker"b-662b" 93 #define alt_total_slen alt_end_marker"b-661b" 94 #define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f" 95 96 #define __OLDINSTR(oldinstr, num) \ 97 "661:\n\t" oldinstr "\n662:\n" \ 98 ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \ 99 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" 100 101 #define OLDINSTR(oldinstr, num) \ 102 __OLDINSTR(oldinstr, num) \ 103 alt_end_marker ":\n" 104 105 /* 106 * max without conditionals. Idea adapted from: 107 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax 108 * 109 * The additional "-" is needed because gas works with s32s. 110 */ 111 #define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") - (" b ")))))" 112 113 /* 114 * Pad the second replacement alternative with additional NOPs if it is 115 * additionally longer than the first replacement alternative. 116 */ 117 #define OLDINSTR_2(oldinstr, num1, num2) \ 118 "661:\n\t" oldinstr "\n662:\n" \ 119 ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \ 120 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \ 121 alt_end_marker ":\n" 122 123 #define ALTINSTR_ENTRY(feature, num) \ 124 " .long 661b - .\n" /* label */ \ 125 " .long " b_replacement(num)"f - .\n" /* new instruction */ \ 126 " .word " __stringify(feature) "\n" /* feature bit */ \ 127 " .byte " alt_total_slen "\n" /* source len */ \ 128 " .byte " alt_rlen(num) "\n" /* replacement len */ \ 129 " .byte " alt_pad_len "\n" /* pad len */ 130 131 #define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \ 132 b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n\t" 133 134 /* alternative assembly primitive: */ 135 #define ALTERNATIVE(oldinstr, newinstr, feature) \ 136 OLDINSTR(oldinstr, 1) \ 137 ".pushsection .altinstructions,\"a\"\n" \ 138 ALTINSTR_ENTRY(feature, 1) \ 139 ".popsection\n" \ 140 ".pushsection .altinstr_replacement, \"ax\"\n" \ 141 ALTINSTR_REPLACEMENT(newinstr, feature, 1) \ 142 ".popsection" 143 144 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\ 145 OLDINSTR_2(oldinstr, 1, 2) \ 146 ".pushsection .altinstructions,\"a\"\n" \ 147 ALTINSTR_ENTRY(feature1, 1) \ 148 ALTINSTR_ENTRY(feature2, 2) \ 149 ".popsection\n" \ 150 ".pushsection .altinstr_replacement, \"ax\"\n" \ 151 ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \ 152 ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \ 153 ".popsection" 154 155 /* 156 * Alternative instructions for different CPU types or capabilities. 157 * 158 * This allows to use optimized instructions even on generic binary 159 * kernels. 160 * 161 * length of oldinstr must be longer or equal the length of newinstr 162 * It can be padded with nops as needed. 163 * 164 * For non barrier like inlines please define new variants 165 * without volatile and memory clobber. 166 */ 167 #define alternative(oldinstr, newinstr, feature) \ 168 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory") 169 170 #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \ 171 asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory") 172 173 /* 174 * Alternative inline assembly with input. 175 * 176 * Pecularities: 177 * No memory clobber here. 178 * Argument numbers start with 1. 179 * Best is to use constraints that are fixed size (like (%1) ... "r") 180 * If you use variable sized constraints like "m" or "g" in the 181 * replacement make sure to pad to the worst case length. 182 * Leaving an unused argument 0 to keep API compatibility. 183 */ 184 #define alternative_input(oldinstr, newinstr, feature, input...) \ 185 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 186 : : "i" (0), ## input) 187 188 /* 189 * This is similar to alternative_input. But it has two features and 190 * respective instructions. 191 * 192 * If CPU has feature2, newinstr2 is used. 193 * Otherwise, if CPU has feature1, newinstr1 is used. 194 * Otherwise, oldinstr is used. 195 */ 196 #define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \ 197 feature2, input...) \ 198 asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \ 199 newinstr2, feature2) \ 200 : : "i" (0), ## input) 201 202 /* Like alternative_input, but with a single output argument */ 203 #define alternative_io(oldinstr, newinstr, feature, output, input...) \ 204 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 205 : output : "i" (0), ## input) 206 207 /* Like alternative_io, but for replacing a direct call with another one. */ 208 #define alternative_call(oldfunc, newfunc, feature, output, input...) \ 209 asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \ 210 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input) 211 212 /* 213 * Like alternative_call, but there are two features and respective functions. 214 * If CPU has feature2, function2 is used. 215 * Otherwise, if CPU has feature1, function1 is used. 216 * Otherwise, old function is used. 217 */ 218 #define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \ 219 output, input...) \ 220 { \ 221 register void *__sp asm(_ASM_SP); \ 222 asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\ 223 "call %P[new2]", feature2) \ 224 : output, "+r" (__sp) \ 225 : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ 226 [new2] "i" (newfunc2), ## input); \ 227 } 228 229 /* 230 * use this macro(s) if you need more than one output parameter 231 * in alternative_io 232 */ 233 #define ASM_OUTPUT2(a...) a 234 235 /* 236 * use this macro if you need clobbers but no inputs in 237 * alternative_{input,io,call}() 238 */ 239 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr 240 241 #endif /* __ASSEMBLY__ */ 242 243 #endif /* _ASM_X86_ALTERNATIVE_H */ 244