1 #ifndef _ASM_X86_ALTERNATIVE_H 2 #define _ASM_X86_ALTERNATIVE_H 3 4 #include <linux/types.h> 5 #include <linux/stddef.h> 6 #include <linux/stringify.h> 7 #include <asm/asm.h> 8 #include <asm/ptrace.h> 9 10 /* 11 * Alternative inline assembly for SMP. 12 * 13 * The LOCK_PREFIX macro defined here replaces the LOCK and 14 * LOCK_PREFIX macros used everywhere in the source tree. 15 * 16 * SMP alternatives use the same data structures as the other 17 * alternatives and the X86_FEATURE_UP flag to indicate the case of a 18 * UP system running a SMP kernel. The existing apply_alternatives() 19 * works fine for patching a SMP kernel for UP. 20 * 21 * The SMP alternative tables can be kept after boot and contain both 22 * UP and SMP versions of the instructions to allow switching back to 23 * SMP at runtime, when hotplugging in a new CPU, which is especially 24 * useful in virtualized environments. 25 * 26 * The very common lock prefix is handled as special case in a 27 * separate table which is a pure address list without replacement ptr 28 * and size information. That keeps the table sizes small. 29 */ 30 31 #ifdef CONFIG_SMP 32 #define LOCK_PREFIX_HERE \ 33 ".pushsection .smp_locks,\"a\"\n" \ 34 ".balign 4\n" \ 35 ".long 671f - .\n" /* offset */ \ 36 ".popsection\n" \ 37 "671:" 38 39 #define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; " 40 41 #else /* ! CONFIG_SMP */ 42 #define LOCK_PREFIX_HERE "" 43 #define LOCK_PREFIX "" 44 #endif 45 46 struct alt_instr { 47 s32 instr_offset; /* original instruction */ 48 s32 repl_offset; /* offset to replacement instruction */ 49 u16 cpuid; /* cpuid bit set for replacement */ 50 u8 instrlen; /* length of original instruction */ 51 u8 replacementlen; /* length of new instruction */ 52 u8 padlen; /* length of build-time padding */ 53 } __packed; 54 55 /* 56 * Debug flag that can be tested to see whether alternative 57 * instructions were patched in already: 58 */ 59 extern int alternatives_patched; 60 61 extern void alternative_instructions(void); 62 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end); 63 64 struct module; 65 66 #ifdef CONFIG_SMP 67 extern void alternatives_smp_module_add(struct module *mod, char *name, 68 void *locks, void *locks_end, 69 void *text, void *text_end); 70 extern void alternatives_smp_module_del(struct module *mod); 71 extern void alternatives_enable_smp(void); 72 extern int alternatives_text_reserved(void *start, void *end); 73 extern bool skip_smp_alternatives; 74 #else 75 static inline void alternatives_smp_module_add(struct module *mod, char *name, 76 void *locks, void *locks_end, 77 void *text, void *text_end) {} 78 static inline void alternatives_smp_module_del(struct module *mod) {} 79 static inline void alternatives_enable_smp(void) {} 80 static inline int alternatives_text_reserved(void *start, void *end) 81 { 82 return 0; 83 } 84 #endif /* CONFIG_SMP */ 85 86 #define b_replacement(num) "664"#num 87 #define e_replacement(num) "665"#num 88 89 #define alt_end_marker "663" 90 #define alt_slen "662b-661b" 91 #define alt_pad_len alt_end_marker"b-662b" 92 #define alt_total_slen alt_end_marker"b-661b" 93 #define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f" 94 95 #define __OLDINSTR(oldinstr, num) \ 96 "661:\n\t" oldinstr "\n662:\n" \ 97 ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \ 98 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" 99 100 #define OLDINSTR(oldinstr, num) \ 101 __OLDINSTR(oldinstr, num) \ 102 alt_end_marker ":\n" 103 104 /* 105 * max without conditionals. Idea adapted from: 106 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax 107 * 108 * The additional "-" is needed because gas works with s32s. 109 */ 110 #define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") - (" b ")))))" 111 112 /* 113 * Pad the second replacement alternative with additional NOPs if it is 114 * additionally longer than the first replacement alternative. 115 */ 116 #define OLDINSTR_2(oldinstr, num1, num2) \ 117 "661:\n\t" oldinstr "\n662:\n" \ 118 ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \ 119 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \ 120 alt_end_marker ":\n" 121 122 #define ALTINSTR_ENTRY(feature, num) \ 123 " .long 661b - .\n" /* label */ \ 124 " .long " b_replacement(num)"f - .\n" /* new instruction */ \ 125 " .word " __stringify(feature) "\n" /* feature bit */ \ 126 " .byte " alt_total_slen "\n" /* source len */ \ 127 " .byte " alt_rlen(num) "\n" /* replacement len */ \ 128 " .byte " alt_pad_len "\n" /* pad len */ 129 130 #define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \ 131 b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n\t" 132 133 /* alternative assembly primitive: */ 134 #define ALTERNATIVE(oldinstr, newinstr, feature) \ 135 OLDINSTR(oldinstr, 1) \ 136 ".pushsection .altinstructions,\"a\"\n" \ 137 ALTINSTR_ENTRY(feature, 1) \ 138 ".popsection\n" \ 139 ".pushsection .altinstr_replacement, \"ax\"\n" \ 140 ALTINSTR_REPLACEMENT(newinstr, feature, 1) \ 141 ".popsection" 142 143 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\ 144 OLDINSTR_2(oldinstr, 1, 2) \ 145 ".pushsection .altinstructions,\"a\"\n" \ 146 ALTINSTR_ENTRY(feature1, 1) \ 147 ALTINSTR_ENTRY(feature2, 2) \ 148 ".popsection\n" \ 149 ".pushsection .altinstr_replacement, \"ax\"\n" \ 150 ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \ 151 ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \ 152 ".popsection" 153 154 /* 155 * This must be included *after* the definition of ALTERNATIVE due to 156 * <asm/arch_hweight.h> 157 */ 158 #include <asm/cpufeature.h> 159 160 /* 161 * Alternative instructions for different CPU types or capabilities. 162 * 163 * This allows to use optimized instructions even on generic binary 164 * kernels. 165 * 166 * length of oldinstr must be longer or equal the length of newinstr 167 * It can be padded with nops as needed. 168 * 169 * For non barrier like inlines please define new variants 170 * without volatile and memory clobber. 171 */ 172 #define alternative(oldinstr, newinstr, feature) \ 173 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory") 174 175 #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \ 176 asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory") 177 178 /* 179 * Alternative inline assembly with input. 180 * 181 * Pecularities: 182 * No memory clobber here. 183 * Argument numbers start with 1. 184 * Best is to use constraints that are fixed size (like (%1) ... "r") 185 * If you use variable sized constraints like "m" or "g" in the 186 * replacement make sure to pad to the worst case length. 187 * Leaving an unused argument 0 to keep API compatibility. 188 */ 189 #define alternative_input(oldinstr, newinstr, feature, input...) \ 190 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 191 : : "i" (0), ## input) 192 193 /* 194 * This is similar to alternative_input. But it has two features and 195 * respective instructions. 196 * 197 * If CPU has feature2, newinstr2 is used. 198 * Otherwise, if CPU has feature1, newinstr1 is used. 199 * Otherwise, oldinstr is used. 200 */ 201 #define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \ 202 feature2, input...) \ 203 asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \ 204 newinstr2, feature2) \ 205 : : "i" (0), ## input) 206 207 /* Like alternative_input, but with a single output argument */ 208 #define alternative_io(oldinstr, newinstr, feature, output, input...) \ 209 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 210 : output : "i" (0), ## input) 211 212 /* Like alternative_io, but for replacing a direct call with another one. */ 213 #define alternative_call(oldfunc, newfunc, feature, output, input...) \ 214 asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \ 215 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input) 216 217 /* 218 * Like alternative_call, but there are two features and respective functions. 219 * If CPU has feature2, function2 is used. 220 * Otherwise, if CPU has feature1, function1 is used. 221 * Otherwise, old function is used. 222 */ 223 #define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \ 224 output, input...) \ 225 asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\ 226 "call %P[new2]", feature2) \ 227 : output : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ 228 [new2] "i" (newfunc2), ## input) 229 230 /* 231 * use this macro(s) if you need more than one output parameter 232 * in alternative_io 233 */ 234 #define ASM_OUTPUT2(a...) a 235 236 /* 237 * use this macro if you need clobbers but no inputs in 238 * alternative_{input,io,call}() 239 */ 240 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr 241 242 struct paravirt_patch_site; 243 #ifdef CONFIG_PARAVIRT 244 void apply_paravirt(struct paravirt_patch_site *start, 245 struct paravirt_patch_site *end); 246 #else 247 static inline void apply_paravirt(struct paravirt_patch_site *start, 248 struct paravirt_patch_site *end) 249 {} 250 #define __parainstructions NULL 251 #define __parainstructions_end NULL 252 #endif 253 254 extern void *text_poke_early(void *addr, const void *opcode, size_t len); 255 256 /* 257 * Clear and restore the kernel write-protection flag on the local CPU. 258 * Allows the kernel to edit read-only pages. 259 * Side-effect: any interrupt handler running between save and restore will have 260 * the ability to write to read-only pages. 261 * 262 * Warning: 263 * Code patching in the UP case is safe if NMIs and MCE handlers are stopped and 264 * no thread can be preempted in the instructions being modified (no iret to an 265 * invalid instruction possible) or if the instructions are changed from a 266 * consistent state to another consistent state atomically. 267 * On the local CPU you need to be protected again NMI or MCE handlers seeing an 268 * inconsistent instruction while you patch. 269 */ 270 extern void *text_poke(void *addr, const void *opcode, size_t len); 271 extern int poke_int3_handler(struct pt_regs *regs); 272 extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler); 273 274 #endif /* _ASM_X86_ALTERNATIVE_H */ 275