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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 | /* Copyright 2002 Andi Kleen */ #include <linux/linkage.h> #include <asm/cpufeature.h> #include <asm/dwarf2.h> #include <asm/alternative-asm.h> /* * memcpy - Copy a memory block. * * Input: * rdi destination * rsi source * rdx count * * Output: * rax original destination */ /* * memcpy_c() - fast string ops (REP MOVSQ) based variant. * * This gets patched over the unrolled variant (below) via the * alternative instructions framework: */ .section .altinstr_replacement, "ax", @progbits .Lmemcpy_c: movq %rdi, %rax movq %rdx, %rcx shrq $3, %rcx andl $7, %edx rep movsq movl %edx, %ecx rep movsb ret .Lmemcpy_e: .previous /* * memcpy_c_e() - enhanced fast string memcpy. This is faster and simpler than * memcpy_c. Use memcpy_c_e when possible. * * This gets patched over the unrolled variant (below) via the * alternative instructions framework: */ .section .altinstr_replacement, "ax", @progbits .Lmemcpy_c_e: movq %rdi, %rax movq %rdx, %rcx rep movsb ret .Lmemcpy_e_e: .previous .weak memcpy ENTRY(__memcpy) ENTRY(memcpy) CFI_STARTPROC movq %rdi, %rax cmpq $0x20, %rdx jb .Lhandle_tail /* * We check whether memory false dependence could occur, * then jump to corresponding copy mode. */ cmp %dil, %sil jl .Lcopy_backward subq $0x20, %rdx .Lcopy_forward_loop: subq $0x20, %rdx /* * Move in blocks of 4x8 bytes: */ movq 0*8(%rsi), %r8 movq 1*8(%rsi), %r9 movq 2*8(%rsi), %r10 movq 3*8(%rsi), %r11 leaq 4*8(%rsi), %rsi movq %r8, 0*8(%rdi) movq %r9, 1*8(%rdi) movq %r10, 2*8(%rdi) movq %r11, 3*8(%rdi) leaq 4*8(%rdi), %rdi jae .Lcopy_forward_loop addl $0x20, %edx jmp .Lhandle_tail .Lcopy_backward: /* * Calculate copy position to tail. */ addq %rdx, %rsi addq %rdx, %rdi subq $0x20, %rdx /* * At most 3 ALU operations in one cycle, * so append NOPS in the same 16 bytes trunk. */ .p2align 4 .Lcopy_backward_loop: subq $0x20, %rdx movq -1*8(%rsi), %r8 movq -2*8(%rsi), %r9 movq -3*8(%rsi), %r10 movq -4*8(%rsi), %r11 leaq -4*8(%rsi), %rsi movq %r8, -1*8(%rdi) movq %r9, -2*8(%rdi) movq %r10, -3*8(%rdi) movq %r11, -4*8(%rdi) leaq -4*8(%rdi), %rdi jae .Lcopy_backward_loop /* * Calculate copy position to head. */ addl $0x20, %edx subq %rdx, %rsi subq %rdx, %rdi .Lhandle_tail: cmpl $16, %edx jb .Lless_16bytes /* * Move data from 16 bytes to 31 bytes. */ movq 0*8(%rsi), %r8 movq 1*8(%rsi), %r9 movq -2*8(%rsi, %rdx), %r10 movq -1*8(%rsi, %rdx), %r11 movq %r8, 0*8(%rdi) movq %r9, 1*8(%rdi) movq %r10, -2*8(%rdi, %rdx) movq %r11, -1*8(%rdi, %rdx) retq .p2align 4 .Lless_16bytes: cmpl $8, %edx jb .Lless_8bytes /* * Move data from 8 bytes to 15 bytes. */ movq 0*8(%rsi), %r8 movq -1*8(%rsi, %rdx), %r9 movq %r8, 0*8(%rdi) movq %r9, -1*8(%rdi, %rdx) retq .p2align 4 .Lless_8bytes: cmpl $4, %edx jb .Lless_3bytes /* * Move data from 4 bytes to 7 bytes. */ movl (%rsi), %ecx movl -4(%rsi, %rdx), %r8d movl %ecx, (%rdi) movl %r8d, -4(%rdi, %rdx) retq .p2align 4 .Lless_3bytes: subl $1, %edx jb .Lend /* * Move data from 1 bytes to 3 bytes. */ movzbl (%rsi), %ecx jz .Lstore_1byte movzbq 1(%rsi), %r8 movzbq (%rsi, %rdx), %r9 movb %r8b, 1(%rdi) movb %r9b, (%rdi, %rdx) .Lstore_1byte: movb %cl, (%rdi) .Lend: retq CFI_ENDPROC ENDPROC(memcpy) ENDPROC(__memcpy) /* * Some CPUs are adding enhanced REP MOVSB/STOSB feature * If the feature is supported, memcpy_c_e() is the first choice. * If enhanced rep movsb copy is not available, use fast string copy * memcpy_c() when possible. This is faster and code is simpler than * original memcpy(). * Otherwise, original memcpy() is used. * In .altinstructions section, ERMS feature is placed after REG_GOOD * feature to implement the right patch order. * * Replace only beginning, memcpy is used to apply alternatives, * so it is silly to overwrite itself with nops - reboot is the * only outcome... */ .section .altinstructions, "a" altinstruction_entry __memcpy,.Lmemcpy_c,X86_FEATURE_REP_GOOD,\ .Lmemcpy_e-.Lmemcpy_c,.Lmemcpy_e-.Lmemcpy_c altinstruction_entry __memcpy,.Lmemcpy_c_e,X86_FEATURE_ERMS, \ .Lmemcpy_e_e-.Lmemcpy_c_e,.Lmemcpy_e_e-.Lmemcpy_c_e .previous |