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 extern void alternative_instructions(void); 56 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end); 57 58 struct module; 59 60 #ifdef CONFIG_SMP 61 extern void alternatives_smp_module_add(struct module *mod, char *name, 62 void *locks, void *locks_end, 63 void *text, void *text_end); 64 extern void alternatives_smp_module_del(struct module *mod); 65 extern void alternatives_enable_smp(void); 66 extern int alternatives_text_reserved(void *start, void *end); 67 extern bool skip_smp_alternatives; 68 #else 69 static inline void alternatives_smp_module_add(struct module *mod, char *name, 70 void *locks, void *locks_end, 71 void *text, void *text_end) {} 72 static inline void alternatives_smp_module_del(struct module *mod) {} 73 static inline void alternatives_enable_smp(void) {} 74 static inline int alternatives_text_reserved(void *start, void *end) 75 { 76 return 0; 77 } 78 #endif /* CONFIG_SMP */ 79 80 #define b_replacement(num) "664"#num 81 #define e_replacement(num) "665"#num 82 83 #define alt_end_marker "663" 84 #define alt_slen "662b-661b" 85 #define alt_pad_len alt_end_marker"b-662b" 86 #define alt_total_slen alt_end_marker"b-661b" 87 #define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f" 88 89 #define __OLDINSTR(oldinstr, num) \ 90 "661:\n\t" oldinstr "\n662:\n" \ 91 ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \ 92 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" 93 94 #define OLDINSTR(oldinstr, num) \ 95 __OLDINSTR(oldinstr, num) \ 96 alt_end_marker ":\n" 97 98 /* 99 * max without conditionals. Idea adapted from: 100 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax 101 * 102 * The additional "-" is needed because gas works with s32s. 103 */ 104 #define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") - (" b ")))))" 105 106 /* 107 * Pad the second replacement alternative with additional NOPs if it is 108 * additionally longer than the first replacement alternative. 109 */ 110 #define OLDINSTR_2(oldinstr, num1, num2) \ 111 "661:\n\t" oldinstr "\n662:\n" \ 112 ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \ 113 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \ 114 alt_end_marker ":\n" 115 116 #define ALTINSTR_ENTRY(feature, num) \ 117 " .long 661b - .\n" /* label */ \ 118 " .long " b_replacement(num)"f - .\n" /* new instruction */ \ 119 " .word " __stringify(feature) "\n" /* feature bit */ \ 120 " .byte " alt_total_slen "\n" /* source len */ \ 121 " .byte " alt_rlen(num) "\n" /* replacement len */ \ 122 " .byte " alt_pad_len "\n" /* pad len */ 123 124 #define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \ 125 b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n\t" 126 127 /* alternative assembly primitive: */ 128 #define ALTERNATIVE(oldinstr, newinstr, feature) \ 129 OLDINSTR(oldinstr, 1) \ 130 ".pushsection .altinstructions,\"a\"\n" \ 131 ALTINSTR_ENTRY(feature, 1) \ 132 ".popsection\n" \ 133 ".pushsection .altinstr_replacement, \"ax\"\n" \ 134 ALTINSTR_REPLACEMENT(newinstr, feature, 1) \ 135 ".popsection" 136 137 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\ 138 OLDINSTR_2(oldinstr, 1, 2) \ 139 ".pushsection .altinstructions,\"a\"\n" \ 140 ALTINSTR_ENTRY(feature1, 1) \ 141 ALTINSTR_ENTRY(feature2, 2) \ 142 ".popsection\n" \ 143 ".pushsection .altinstr_replacement, \"ax\"\n" \ 144 ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \ 145 ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \ 146 ".popsection" 147 148 /* 149 * This must be included *after* the definition of ALTERNATIVE due to 150 * <asm/arch_hweight.h> 151 */ 152 #include <asm/cpufeature.h> 153 154 /* 155 * Alternative instructions for different CPU types or capabilities. 156 * 157 * This allows to use optimized instructions even on generic binary 158 * kernels. 159 * 160 * length of oldinstr must be longer or equal the length of newinstr 161 * It can be padded with nops as needed. 162 * 163 * For non barrier like inlines please define new variants 164 * without volatile and memory clobber. 165 */ 166 #define alternative(oldinstr, newinstr, feature) \ 167 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory") 168 169 #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \ 170 asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory") 171 172 /* 173 * Alternative inline assembly with input. 174 * 175 * Pecularities: 176 * No memory clobber here. 177 * Argument numbers start with 1. 178 * Best is to use constraints that are fixed size (like (%1) ... "r") 179 * If you use variable sized constraints like "m" or "g" in the 180 * replacement make sure to pad to the worst case length. 181 * Leaving an unused argument 0 to keep API compatibility. 182 */ 183 #define alternative_input(oldinstr, newinstr, feature, input...) \ 184 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 185 : : "i" (0), ## input) 186 187 /* 188 * This is similar to alternative_input. But it has two features and 189 * respective instructions. 190 * 191 * If CPU has feature2, newinstr2 is used. 192 * Otherwise, if CPU has feature1, newinstr1 is used. 193 * Otherwise, oldinstr is used. 194 */ 195 #define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \ 196 feature2, input...) \ 197 asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \ 198 newinstr2, feature2) \ 199 : : "i" (0), ## input) 200 201 /* Like alternative_input, but with a single output argument */ 202 #define alternative_io(oldinstr, newinstr, feature, output, input...) \ 203 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 204 : output : "i" (0), ## input) 205 206 /* Like alternative_io, but for replacing a direct call with another one. */ 207 #define alternative_call(oldfunc, newfunc, feature, output, input...) \ 208 asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \ 209 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input) 210 211 /* 212 * Like alternative_call, but there are two features and respective functions. 213 * If CPU has feature2, function2 is used. 214 * Otherwise, if CPU has feature1, function1 is used. 215 * Otherwise, old function is used. 216 */ 217 #define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \ 218 output, input...) \ 219 asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\ 220 "call %P[new2]", feature2) \ 221 : output : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ 222 [new2] "i" (newfunc2), ## input) 223 224 /* 225 * use this macro(s) if you need more than one output parameter 226 * in alternative_io 227 */ 228 #define ASM_OUTPUT2(a...) a 229 230 /* 231 * use this macro if you need clobbers but no inputs in 232 * alternative_{input,io,call}() 233 */ 234 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr 235 236 struct paravirt_patch_site; 237 #ifdef CONFIG_PARAVIRT 238 void apply_paravirt(struct paravirt_patch_site *start, 239 struct paravirt_patch_site *end); 240 #else 241 static inline void apply_paravirt(struct paravirt_patch_site *start, 242 struct paravirt_patch_site *end) 243 {} 244 #define __parainstructions NULL 245 #define __parainstructions_end NULL 246 #endif 247 248 extern void *text_poke_early(void *addr, const void *opcode, size_t len); 249 250 /* 251 * Clear and restore the kernel write-protection flag on the local CPU. 252 * Allows the kernel to edit read-only pages. 253 * Side-effect: any interrupt handler running between save and restore will have 254 * the ability to write to read-only pages. 255 * 256 * Warning: 257 * Code patching in the UP case is safe if NMIs and MCE handlers are stopped and 258 * no thread can be preempted in the instructions being modified (no iret to an 259 * invalid instruction possible) or if the instructions are changed from a 260 * consistent state to another consistent state atomically. 261 * On the local CPU you need to be protected again NMI or MCE handlers seeing an 262 * inconsistent instruction while you patch. 263 */ 264 extern void *text_poke(void *addr, const void *opcode, size_t len); 265 extern int poke_int3_handler(struct pt_regs *regs); 266 extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler); 267 268 #endif /* _ASM_X86_ALTERNATIVE_H */ 269