1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 /* Copyright 2002 Andi Kleen */ 3 4 #include <linux/linkage.h> 5 #include <asm/errno.h> 6 #include <asm/cpufeatures.h> 7 #include <asm/alternative.h> 8 #include <asm/export.h> 9 10 .pushsection .noinstr.text, "ax" 11 12 /* 13 * We build a jump to memcpy_orig by default which gets NOPped out on 14 * the majority of x86 CPUs which set REP_GOOD. In addition, CPUs which 15 * have the enhanced REP MOVSB/STOSB feature (ERMS), change those NOPs 16 * to a jmp to memcpy_erms which does the REP; MOVSB mem copy. 17 */ 18 19 /* 20 * memcpy - Copy a memory block. 21 * 22 * Input: 23 * rdi destination 24 * rsi source 25 * rdx count 26 * 27 * Output: 28 * rax original destination 29 */ 30 SYM_FUNC_START_ALIAS(__memcpy) 31 SYM_FUNC_START_WEAK(memcpy) 32 ALTERNATIVE_2 "jmp memcpy_orig", "", X86_FEATURE_REP_GOOD, \ 33 "jmp memcpy_erms", X86_FEATURE_ERMS 34 35 movq %rdi, %rax 36 movq %rdx, %rcx 37 shrq $3, %rcx 38 andl $7, %edx 39 rep movsq 40 movl %edx, %ecx 41 rep movsb 42 RET 43 SYM_FUNC_END(memcpy) 44 SYM_FUNC_END_ALIAS(__memcpy) 45 EXPORT_SYMBOL(memcpy) 46 EXPORT_SYMBOL(__memcpy) 47 48 /* 49 * memcpy_erms() - enhanced fast string memcpy. This is faster and 50 * simpler than memcpy. Use memcpy_erms when possible. 51 */ 52 SYM_FUNC_START_LOCAL(memcpy_erms) 53 movq %rdi, %rax 54 movq %rdx, %rcx 55 rep movsb 56 RET 57 SYM_FUNC_END(memcpy_erms) 58 59 SYM_FUNC_START_LOCAL(memcpy_orig) 60 movq %rdi, %rax 61 62 cmpq $0x20, %rdx 63 jb .Lhandle_tail 64 65 /* 66 * We check whether memory false dependence could occur, 67 * then jump to corresponding copy mode. 68 */ 69 cmp %dil, %sil 70 jl .Lcopy_backward 71 subq $0x20, %rdx 72 .Lcopy_forward_loop: 73 subq $0x20, %rdx 74 75 /* 76 * Move in blocks of 4x8 bytes: 77 */ 78 movq 0*8(%rsi), %r8 79 movq 1*8(%rsi), %r9 80 movq 2*8(%rsi), %r10 81 movq 3*8(%rsi), %r11 82 leaq 4*8(%rsi), %rsi 83 84 movq %r8, 0*8(%rdi) 85 movq %r9, 1*8(%rdi) 86 movq %r10, 2*8(%rdi) 87 movq %r11, 3*8(%rdi) 88 leaq 4*8(%rdi), %rdi 89 jae .Lcopy_forward_loop 90 addl $0x20, %edx 91 jmp .Lhandle_tail 92 93 .Lcopy_backward: 94 /* 95 * Calculate copy position to tail. 96 */ 97 addq %rdx, %rsi 98 addq %rdx, %rdi 99 subq $0x20, %rdx 100 /* 101 * At most 3 ALU operations in one cycle, 102 * so append NOPS in the same 16 bytes trunk. 103 */ 104 .p2align 4 105 .Lcopy_backward_loop: 106 subq $0x20, %rdx 107 movq -1*8(%rsi), %r8 108 movq -2*8(%rsi), %r9 109 movq -3*8(%rsi), %r10 110 movq -4*8(%rsi), %r11 111 leaq -4*8(%rsi), %rsi 112 movq %r8, -1*8(%rdi) 113 movq %r9, -2*8(%rdi) 114 movq %r10, -3*8(%rdi) 115 movq %r11, -4*8(%rdi) 116 leaq -4*8(%rdi), %rdi 117 jae .Lcopy_backward_loop 118 119 /* 120 * Calculate copy position to head. 121 */ 122 addl $0x20, %edx 123 subq %rdx, %rsi 124 subq %rdx, %rdi 125 .Lhandle_tail: 126 cmpl $16, %edx 127 jb .Lless_16bytes 128 129 /* 130 * Move data from 16 bytes to 31 bytes. 131 */ 132 movq 0*8(%rsi), %r8 133 movq 1*8(%rsi), %r9 134 movq -2*8(%rsi, %rdx), %r10 135 movq -1*8(%rsi, %rdx), %r11 136 movq %r8, 0*8(%rdi) 137 movq %r9, 1*8(%rdi) 138 movq %r10, -2*8(%rdi, %rdx) 139 movq %r11, -1*8(%rdi, %rdx) 140 RET 141 .p2align 4 142 .Lless_16bytes: 143 cmpl $8, %edx 144 jb .Lless_8bytes 145 /* 146 * Move data from 8 bytes to 15 bytes. 147 */ 148 movq 0*8(%rsi), %r8 149 movq -1*8(%rsi, %rdx), %r9 150 movq %r8, 0*8(%rdi) 151 movq %r9, -1*8(%rdi, %rdx) 152 RET 153 .p2align 4 154 .Lless_8bytes: 155 cmpl $4, %edx 156 jb .Lless_3bytes 157 158 /* 159 * Move data from 4 bytes to 7 bytes. 160 */ 161 movl (%rsi), %ecx 162 movl -4(%rsi, %rdx), %r8d 163 movl %ecx, (%rdi) 164 movl %r8d, -4(%rdi, %rdx) 165 RET 166 .p2align 4 167 .Lless_3bytes: 168 subl $1, %edx 169 jb .Lend 170 /* 171 * Move data from 1 bytes to 3 bytes. 172 */ 173 movzbl (%rsi), %ecx 174 jz .Lstore_1byte 175 movzbq 1(%rsi), %r8 176 movzbq (%rsi, %rdx), %r9 177 movb %r8b, 1(%rdi) 178 movb %r9b, (%rdi, %rdx) 179 .Lstore_1byte: 180 movb %cl, (%rdi) 181 182 .Lend: 183 RET 184 SYM_FUNC_END(memcpy_orig) 185 186 .popsection 187