1 #ifndef __ASM_ALTERNATIVE_H 2 #define __ASM_ALTERNATIVE_H 3 4 #include <asm/cpufeature.h> 5 6 #ifdef CONFIG_HAS_ALTERNATIVE 7 8 #ifndef __ASSEMBLY__ 9 10 #include <xen/init.h> 11 #include <xen/types.h> 12 #include <xen/stringify.h> 13 14 struct alt_instr { 15 s32 orig_offset; /* offset to original instruction */ 16 s32 alt_offset; /* offset to replacement instruction */ 17 u16 cpufeature; /* cpufeature bit set for replacement */ 18 u8 orig_len; /* size of original instruction(s) */ 19 u8 alt_len; /* size of new instruction(s), <= orig_len */ 20 }; 21 22 /* Xen: helpers used by common code. */ 23 #define __ALT_PTR(a,f) ((u32 *)((void *)&(a)->f + (a)->f)) 24 #define ALT_ORIG_PTR(a) __ALT_PTR(a, orig_offset) 25 #define ALT_REPL_PTR(a) __ALT_PTR(a, alt_offset) 26 27 void __init apply_alternatives_all(void); 28 int apply_alternatives(const struct alt_instr *start, const struct alt_instr *end); 29 30 #define ALTINSTR_ENTRY(feature) \ 31 " .word 661b - .\n" /* label */ \ 32 " .word 663f - .\n" /* new instruction */ \ 33 " .hword " __stringify(feature) "\n" /* feature bit */ \ 34 " .byte 662b-661b\n" /* source len */ \ 35 " .byte 664f-663f\n" /* replacement len */ 36 37 /* 38 * alternative assembly primitive: 39 * 40 * If any of these .org directive fail, it means that insn1 and insn2 41 * don't have the same length. This used to be written as 42 * 43 * .if ((664b-663b) != (662b-661b)) 44 * .error "Alternatives instruction length mismatch" 45 * .endif 46 * 47 * but most assemblers die if insn1 or insn2 have a .inst. This should 48 * be fixed in a binutils release posterior to 2.25.51.0.2 (anything 49 * containing commit 4e4d08cf7399b606 or c1baaddf8861). 50 */ 51 #define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled) \ 52 ".if "__stringify(cfg_enabled)" == 1\n" \ 53 "661:\n\t" \ 54 oldinstr "\n" \ 55 "662:\n" \ 56 ".pushsection .altinstructions,\"a\"\n" \ 57 ALTINSTR_ENTRY(feature) \ 58 ".popsection\n" \ 59 ".pushsection .altinstr_replacement, \"a\"\n" \ 60 "663:\n\t" \ 61 newinstr "\n" \ 62 "664:\n\t" \ 63 ".popsection\n\t" \ 64 ".org . - (664b-663b) + (662b-661b)\n\t" \ 65 ".org . - (662b-661b) + (664b-663b)\n" \ 66 ".endif\n" 67 68 #define _ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg, ...) \ 69 __ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg)) 70 71 #else 72 73 #include <asm/asm_defns.h> 74 75 .macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len 76 .word \orig_offset - . 77 .word \alt_offset - . 78 .hword \feature 79 .byte \orig_len 80 .byte \alt_len 81 .endm 82 83 .macro alternative_insn insn1, insn2, cap, enable = 1 84 .if \enable 85 661: \insn1 86 662: .pushsection .altinstructions, "a" 87 altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f 88 .popsection 89 .pushsection .altinstr_replacement, "ax" 90 663: \insn2 91 664: .popsection 92 .org . - (664b-663b) + (662b-661b) 93 .org . - (662b-661b) + (664b-663b) 94 .endif 95 .endm 96 97 /* 98 * Begin an alternative code sequence. 99 * 100 * The code that follows this macro will be assembled and linked as 101 * normal. There are no restrictions on this code. 102 */ 103 .macro alternative_if_not cap, enable = 1 104 .if \enable 105 .pushsection .altinstructions, "a" 106 altinstruction_entry 661f, 663f, \cap, 662f-661f, 664f-663f 107 .popsection 108 661: 109 .endif 110 .endm 111 112 /* 113 * Provide the alternative code sequence. 114 * 115 * The code that follows this macro is assembled into a special 116 * section to be used for dynamic patching. Code that follows this 117 * macro must: 118 * 119 * 1. Be exactly the same length (in bytes) as the default code 120 * sequence. 121 * 122 * 2. Not contain a branch target that is used outside of the 123 * alternative sequence it is defined in (branches into an 124 * alternative sequence are not fixed up). 125 */ 126 .macro alternative_else 127 662: .pushsection .altinstr_replacement, "ax" 128 663: 129 .endm 130 131 /* 132 * Complete an alternative code sequence. 133 */ 134 .macro alternative_endif 135 664: .popsection 136 .org . - (664b-663b) + (662b-661b) 137 .org . - (662b-661b) + (664b-663b) 138 .endm 139 140 #define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...) \ 141 alternative_insn insn1, insn2, cap, IS_ENABLED(cfg) 142 143 #endif /* __ASSEMBLY__ */ 144 145 /* 146 * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature)); 147 * 148 * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature, CONFIG_FOO)); 149 * N.B. If CONFIG_FOO is specified, but not selected, the whole block 150 * will be omitted, including oldinstr. 151 */ 152 #define ALTERNATIVE(oldinstr, newinstr, ...) \ 153 _ALTERNATIVE_CFG(oldinstr, newinstr, __VA_ARGS__, 1) 154 155 #else /* !CONFIG_HAS_ALTERNATIVE */ 156 157 static inline void apply_alternatives_all(void) 158 { 159 } 160 161 static inline int apply_alternatives(void *start, size_t length) 162 { 163 return 0; 164 } 165 166 #endif 167 168 #endif /* __ASM_ALTERNATIVE_H */ 169