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bce5a1e8 ND |
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) |