1 /* SPDX-License-Identifier: GPL-2.0 */ 2 3 #include <linux/linkage.h> 4 #include <asm/export.h> 5 6 SYM_FUNC_START(memmove) 7 /* 8 * void *memmove(void *dest_in, const void *src_in, size_t n) 9 * -mregparm=3 passes these in registers: 10 * dest_in: %eax 11 * src_in: %edx 12 * n: %ecx 13 * See also: arch/x86/entry/calling.h for description of the calling convention. 14 * 15 * n can remain in %ecx, but for `rep movsl`, we'll need dest in %edi and src 16 * in %esi. 17 */ 18 .set dest_in, %eax 19 .set dest, %edi 20 .set src_in, %edx 21 .set src, %esi 22 .set n, %ecx 23 .set tmp0, %edx 24 .set tmp0w, %dx 25 .set tmp1, %ebx 26 .set tmp1w, %bx 27 .set tmp2, %eax 28 .set tmp3b, %cl 29 30 /* 31 * Save all callee-saved registers, because this function is going to clobber 32 * all of them: 33 */ 34 pushl %ebp 35 movl %esp, %ebp // set standard frame pointer 36 37 pushl %ebx 38 pushl %edi 39 pushl %esi 40 pushl %eax // save 'dest_in' parameter [eax] as the return value 41 42 movl src_in, src 43 movl dest_in, dest 44 45 /* Handle more 16 bytes in loop */ 46 cmpl $0x10, n 47 jb .Lmove_16B 48 49 /* Decide forward/backward copy mode */ 50 cmpl dest, src 51 jb .Lbackwards_header 52 53 /* 54 * movs instruction have many startup latency 55 * so we handle small size by general register. 56 */ 57 cmpl $680, n 58 jb .Ltoo_small_forwards 59 /* movs instruction is only good for aligned case. */ 60 movl src, tmp0 61 xorl dest, tmp0 62 andl $0xff, tmp0 63 jz .Lforward_movs 64 .Ltoo_small_forwards: 65 subl $0x10, n 66 67 /* We gobble 16 bytes forward in each loop. */ 68 .Lmove_16B_forwards_loop: 69 subl $0x10, n 70 movl 0*4(src), tmp0 71 movl 1*4(src), tmp1 72 movl tmp0, 0*4(dest) 73 movl tmp1, 1*4(dest) 74 movl 2*4(src), tmp0 75 movl 3*4(src), tmp1 76 movl tmp0, 2*4(dest) 77 movl tmp1, 3*4(dest) 78 leal 0x10(src), src 79 leal 0x10(dest), dest 80 jae .Lmove_16B_forwards_loop 81 addl $0x10, n 82 jmp .Lmove_16B 83 84 /* Handle data forward by movs. */ 85 .p2align 4 86 .Lforward_movs: 87 movl -4(src, n), tmp0 88 leal -4(dest, n), tmp1 89 shrl $2, n 90 rep movsl 91 movl tmp0, (tmp1) 92 jmp .Ldone 93 94 /* Handle data backward by movs. */ 95 .p2align 4 96 .Lbackwards_movs: 97 movl (src), tmp0 98 movl dest, tmp1 99 leal -4(src, n), src 100 leal -4(dest, n), dest 101 shrl $2, n 102 std 103 rep movsl 104 movl tmp0,(tmp1) 105 cld 106 jmp .Ldone 107 108 /* Start to prepare for backward copy. */ 109 .p2align 4 110 .Lbackwards_header: 111 cmpl $680, n 112 jb .Ltoo_small_backwards 113 movl src, tmp0 114 xorl dest, tmp0 115 andl $0xff, tmp0 116 jz .Lbackwards_movs 117 118 /* Calculate copy position to tail. */ 119 .Ltoo_small_backwards: 120 addl n, src 121 addl n, dest 122 subl $0x10, n 123 124 /* We gobble 16 bytes backward in each loop. */ 125 .Lmove_16B_backwards_loop: 126 subl $0x10, n 127 128 movl -1*4(src), tmp0 129 movl -2*4(src), tmp1 130 movl tmp0, -1*4(dest) 131 movl tmp1, -2*4(dest) 132 movl -3*4(src), tmp0 133 movl -4*4(src), tmp1 134 movl tmp0, -3*4(dest) 135 movl tmp1, -4*4(dest) 136 leal -0x10(src), src 137 leal -0x10(dest), dest 138 jae .Lmove_16B_backwards_loop 139 /* Calculate copy position to head. */ 140 addl $0x10, n 141 subl n, src 142 subl n, dest 143 144 /* Move data from 8 bytes to 15 bytes. */ 145 .p2align 4 146 .Lmove_16B: 147 cmpl $8, n 148 jb .Lmove_8B 149 movl 0*4(src), tmp0 150 movl 1*4(src), tmp1 151 movl -2*4(src, n), tmp2 152 movl -1*4(src, n), src 153 154 movl tmp0, 0*4(dest) 155 movl tmp1, 1*4(dest) 156 movl tmp2, -2*4(dest, n) 157 movl src, -1*4(dest, n) 158 jmp .Ldone 159 160 /* Move data from 4 bytes to 7 bytes. */ 161 .p2align 4 162 .Lmove_8B: 163 cmpl $4, n 164 jb .Lmove_4B 165 movl 0*4(src), tmp0 166 movl -1*4(src, n), tmp1 167 movl tmp0, 0*4(dest) 168 movl tmp1, -1*4(dest, n) 169 jmp .Ldone 170 171 /* Move data from 2 bytes to 3 bytes. */ 172 .p2align 4 173 .Lmove_4B: 174 cmpl $2, n 175 jb .Lmove_1B 176 movw 0*2(src), tmp0w 177 movw -1*2(src, n), tmp1w 178 movw tmp0w, 0*2(dest) 179 movw tmp1w, -1*2(dest, n) 180 jmp .Ldone 181 182 /* Move data for 1 byte. */ 183 .p2align 4 184 .Lmove_1B: 185 cmpl $1, n 186 jb .Ldone 187 movb (src), tmp3b 188 movb tmp3b, (dest) 189 .p2align 4 190 .Ldone: 191 popl dest_in // restore 'dest_in' [eax] as the return value 192 /* Restore all callee-saved registers: */ 193 popl %esi 194 popl %edi 195 popl %ebx 196 popl %ebp 197 198 RET 199 SYM_FUNC_END(memmove) 200 EXPORT_SYMBOL(memmove) 201