1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Most of the string-functions are rather heavily hand-optimized,
4 * see especially strsep,strstr,str[c]spn. They should work, but are not
5 * very easy to understand. Everything is done entirely within the register
6 * set, making the functions fast and clean. String instructions have been
7 * used through-out, making for "slightly" unclear code :-)
8 *
9 * AK: On P4 and K7 using non string instruction implementations might be faster
10 * for large memory blocks. But most of them are unlikely to be used on large
11 * strings.
12 */
13
14 #define __NO_FORTIFY
15 #include <linux/string.h>
16 #include <linux/export.h>
17
18 #ifdef __HAVE_ARCH_STRCPY
19 char *strcpy(char *dest, const char *src)
20 {
21 int d0, d1, d2;
22 asm volatile("1:\tlodsb\n\t"
23 "stosb\n\t"
24 "testb %%al,%%al\n\t"
25 "jne 1b"
26 : "=&S" (d0), "=&D" (d1), "=&a" (d2)
27 : "" (src), "1" (dest) : "memory");
28 return dest;
29 }
30 EXPORT_SYMBOL(strcpy);
31 #endif
32
33 #ifdef __HAVE_ARCH_STRNCPY
34 char *strncpy(char *dest, const char *src, size_t count)
35 {
36 int d0, d1, d2, d3;
37 asm volatile("1:\tdecl %2\n\t"
38 "js 2f\n\t"
39 "lodsb\n\t"
40 "stosb\n\t"
41 "testb %%al,%%al\n\t"
42 "jne 1b\n\t"
43 "rep\n\t"
44 "stosb\n"
45 "2:"
46 : "=&S" (d0), "=&D" (d1), "=&c" (d2), "=&a" (d3)
47 : "" (src), "1" (dest), "2" (count) : "memory");
48 return dest;
49 }
50 EXPORT_SYMBOL(strncpy);
51 #endif
52
53 #ifdef __HAVE_ARCH_STRCAT
54 char *strcat(char *dest, const char *src)
55 {
56 int d0, d1, d2, d3;
57 asm volatile("repne\n\t"
58 "scasb\n\t"
59 "decl %1\n"
60 "1:\tlodsb\n\t"
61 "stosb\n\t"
62 "testb %%al,%%al\n\t"
63 "jne 1b"
64 : "=&S" (d0), "=&D" (d1), "=&a" (d2), "=&c" (d3)
65 : "" (src), "1" (dest), "2" (0), "3" (0xffffffffu) : "memory");
66 return dest;
67 }
68 EXPORT_SYMBOL(strcat);
69 #endif
70
71 #ifdef __HAVE_ARCH_STRNCAT
72 char *strncat(char *dest, const char *src, size_t count)
73 {
74 int d0, d1, d2, d3;
75 asm volatile("repne\n\t"
76 "scasb\n\t"
77 "decl %1\n\t"
78 "movl %8,%3\n"
79 "1:\tdecl %3\n\t"
80 "js 2f\n\t"
81 "lodsb\n\t"
82 "stosb\n\t"
83 "testb %%al,%%al\n\t"
84 "jne 1b\n"
85 "2:\txorl %2,%2\n\t"
86 "stosb"
87 : "=&S" (d0), "=&D" (d1), "=&a" (d2), "=&c" (d3)
88 : "" (src), "1" (dest), "2" (0), "3" (0xffffffffu), "g" (count)
89 : "memory");
90 return dest;
91 }
92 EXPORT_SYMBOL(strncat);
93 #endif
94
95 #ifdef __HAVE_ARCH_STRCMP
96 int strcmp(const char *cs, const char *ct)
97 {
98 int d0, d1;
99 int res;
100 asm volatile("1:\tlodsb\n\t"
101 "scasb\n\t"
102 "jne 2f\n\t"
103 "testb %%al,%%al\n\t"
104 "jne 1b\n\t"
105 "xorl %%eax,%%eax\n\t"
106 "jmp 3f\n"
107 "2:\tsbbl %%eax,%%eax\n\t"
108 "orb $1,%%al\n"
109 "3:"
110 : "=a" (res), "=&S" (d0), "=&D" (d1)
111 : "1" (cs), "2" (ct)
112 : "memory");
113 return res;
114 }
115 EXPORT_SYMBOL(strcmp);
116 #endif
117
118 #ifdef __HAVE_ARCH_STRNCMP
119 int strncmp(const char *cs, const char *ct, size_t count)
120 {
121 int res;
122 int d0, d1, d2;
123 asm volatile("1:\tdecl %3\n\t"
124 "js 2f\n\t"
125 "lodsb\n\t"
126 "scasb\n\t"
127 "jne 3f\n\t"
128 "testb %%al,%%al\n\t"
129 "jne 1b\n"
130 "2:\txorl %%eax,%%eax\n\t"
131 "jmp 4f\n"
132 "3:\tsbbl %%eax,%%eax\n\t"
133 "orb $1,%%al\n"
134 "4:"
135 : "=a" (res), "=&S" (d0), "=&D" (d1), "=&c" (d2)
136 : "1" (cs), "2" (ct), "3" (count)
137 : "memory");
138 return res;
139 }
140 EXPORT_SYMBOL(strncmp);
141 #endif
142
143 #ifdef __HAVE_ARCH_STRCHR
144 char *strchr(const char *s, int c)
145 {
146 int d0;
147 char *res;
148 asm volatile("movb %%al,%%ah\n"
149 "1:\tlodsb\n\t"
150 "cmpb %%ah,%%al\n\t"
151 "je 2f\n\t"
152 "testb %%al,%%al\n\t"
153 "jne 1b\n\t"
154 "movl $1,%1\n"
155 "2:\tmovl %1,%0\n\t"
156 "decl %0"
157 : "=a" (res), "=&S" (d0)
158 : "1" (s), "" (c)
159 : "memory");
160 return res;
161 }
162 EXPORT_SYMBOL(strchr);
163 #endif
164
165 #ifdef __HAVE_ARCH_STRLEN
166 size_t strlen(const char *s)
167 {
168 int d0;
169 size_t res;
170 asm volatile("repne\n\t"
171 "scasb"
172 : "=c" (res), "=&D" (d0)
173 : "1" (s), "a" (0), "" (0xffffffffu)
174 : "memory");
175 return ~res - 1;
176 }
177 EXPORT_SYMBOL(strlen);
178 #endif
179
180 #ifdef __HAVE_ARCH_MEMCHR
181 void *memchr(const void *cs, int c, size_t count)
182 {
183 int d0;
184 void *res;
185 if (!count)
186 return NULL;
187 asm volatile("repne\n\t"
188 "scasb\n\t"
189 "je 1f\n\t"
190 "movl $1,%0\n"
191 "1:\tdecl %0"
192 : "=D" (res), "=&c" (d0)
193 : "a" (c), "" (cs), "1" (count)
194 : "memory");
195 return res;
196 }
197 EXPORT_SYMBOL(memchr);
198 #endif
199
200 #ifdef __HAVE_ARCH_MEMSCAN
201 void *memscan(void *addr, int c, size_t size)
202 {
203 if (!size)
204 return addr;
205 asm volatile("repnz; scasb\n\t"
206 "jnz 1f\n\t"
207 "dec %%edi\n"
208 "1:"
209 : "=D" (addr), "=c" (size)
210 : "" (addr), "1" (size), "a" (c)
211 : "memory");
212 return addr;
213 }
214 EXPORT_SYMBOL(memscan);
215 #endif
216
217 #ifdef __HAVE_ARCH_STRNLEN
218 size_t strnlen(const char *s, size_t count)
219 {
220 int d0;
221 int res;
222 asm volatile("movl %2,%0\n\t"
223 "jmp 2f\n"
224 "1:\tcmpb $0,(%0)\n\t"
225 "je 3f\n\t"
226 "incl %0\n"
227 "2:\tdecl %1\n\t"
228 "cmpl $-1,%1\n\t"
229 "jne 1b\n"
230 "3:\tsubl %2,%0"
231 : "=a" (res), "=&d" (d0)
232 : "c" (s), "1" (count)
233 : "memory");
234 return res;
235 }
236 EXPORT_SYMBOL(strnlen);
237 #endif
238
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