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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
19char *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 : "0" (src), "1" (dest) : "memory");
28 return dest;
29}
30EXPORT_SYMBOL(strcpy);
31#endif
32
33#ifdef __HAVE_ARCH_STRCAT
34char *strcat(char *dest, const char *src)
35{
36 int d0, d1, d2, d3;
37 asm volatile("repne scasb\n\t"
38 "decl %1\n"
39 "1:\tlodsb\n\t"
40 "stosb\n\t"
41 "testb %%al,%%al\n\t"
42 "jne 1b"
43 : "=&S" (d0), "=&D" (d1), "=&a" (d2), "=&c" (d3)
44 : "0" (src), "1" (dest), "2" (0), "3" (0xffffffffu) : "memory");
45 return dest;
46}
47EXPORT_SYMBOL(strcat);
48#endif
49
50#ifdef __HAVE_ARCH_STRNCAT
51char *strncat(char *dest, const char *src, size_t count)
52{
53 int d0, d1, d2, d3;
54 asm volatile("repne scasb\n\t"
55 "decl %1\n\t"
56 "movl %8,%3\n"
57 "1:\tdecl %3\n\t"
58 "js 2f\n\t"
59 "lodsb\n\t"
60 "stosb\n\t"
61 "testb %%al,%%al\n\t"
62 "jne 1b\n"
63 "2:\txorl %2,%2\n\t"
64 "stosb"
65 : "=&S" (d0), "=&D" (d1), "=&a" (d2), "=&c" (d3)
66 : "0" (src), "1" (dest), "2" (0), "3" (0xffffffffu), "g" (count)
67 : "memory");
68 return dest;
69}
70EXPORT_SYMBOL(strncat);
71#endif
72
73#ifdef __HAVE_ARCH_STRCMP
74int strcmp(const char *cs, const char *ct)
75{
76 int d0, d1;
77 int res;
78 asm volatile("1:\tlodsb\n\t"
79 "scasb\n\t"
80 "jne 2f\n\t"
81 "testb %%al,%%al\n\t"
82 "jne 1b\n\t"
83 "xorl %%eax,%%eax\n\t"
84 "jmp 3f\n"
85 "2:\tsbbl %%eax,%%eax\n\t"
86 "orb $1,%%al\n"
87 "3:"
88 : "=a" (res), "=&S" (d0), "=&D" (d1)
89 : "1" (cs), "2" (ct)
90 : "memory");
91 return res;
92}
93EXPORT_SYMBOL(strcmp);
94#endif
95
96#ifdef __HAVE_ARCH_STRNCMP
97int strncmp(const char *cs, const char *ct, size_t count)
98{
99 int res;
100 int d0, d1, d2;
101 asm volatile("1:\tdecl %3\n\t"
102 "js 2f\n\t"
103 "lodsb\n\t"
104 "scasb\n\t"
105 "jne 3f\n\t"
106 "testb %%al,%%al\n\t"
107 "jne 1b\n"
108 "2:\txorl %%eax,%%eax\n\t"
109 "jmp 4f\n"
110 "3:\tsbbl %%eax,%%eax\n\t"
111 "orb $1,%%al\n"
112 "4:"
113 : "=a" (res), "=&S" (d0), "=&D" (d1), "=&c" (d2)
114 : "1" (cs), "2" (ct), "3" (count)
115 : "memory");
116 return res;
117}
118EXPORT_SYMBOL(strncmp);
119#endif
120
121#ifdef __HAVE_ARCH_STRCHR
122char *strchr(const char *s, int c)
123{
124 int d0;
125 char *res;
126 asm volatile("movb %%al,%%ah\n"
127 "1:\tlodsb\n\t"
128 "cmpb %%ah,%%al\n\t"
129 "je 2f\n\t"
130 "testb %%al,%%al\n\t"
131 "jne 1b\n\t"
132 "movl $1,%1\n"
133 "2:\tmovl %1,%0\n\t"
134 "decl %0"
135 : "=a" (res), "=&S" (d0)
136 : "1" (s), "0" (c)
137 : "memory");
138 return res;
139}
140EXPORT_SYMBOL(strchr);
141#endif
142
143#ifdef __HAVE_ARCH_STRLEN
144size_t strlen(const char *s)
145{
146 int d0;
147 size_t res;
148 asm volatile("repne scasb"
149 : "=c" (res), "=&D" (d0)
150 : "1" (s), "a" (0), "0" (0xffffffffu)
151 : "memory");
152 return ~res - 1;
153}
154EXPORT_SYMBOL(strlen);
155#endif
156
157#ifdef __HAVE_ARCH_MEMCHR
158void *memchr(const void *cs, int c, size_t count)
159{
160 int d0;
161 void *res;
162 if (!count)
163 return NULL;
164 asm volatile("repne scasb\n\t"
165 "je 1f\n\t"
166 "movl $1,%0\n"
167 "1:\tdecl %0"
168 : "=D" (res), "=&c" (d0)
169 : "a" (c), "0" (cs), "1" (count)
170 : "memory");
171 return res;
172}
173EXPORT_SYMBOL(memchr);
174#endif
175
176#ifdef __HAVE_ARCH_MEMSCAN
177void *memscan(void *addr, int c, size_t size)
178{
179 if (!size)
180 return addr;
181 asm volatile("repnz scasb\n\t"
182 "jnz 1f\n\t"
183 "dec %%edi\n"
184 "1:"
185 : "=D" (addr), "=c" (size)
186 : "0" (addr), "1" (size), "a" (c)
187 : "memory");
188 return addr;
189}
190EXPORT_SYMBOL(memscan);
191#endif
192
193#ifdef __HAVE_ARCH_STRNLEN
194size_t strnlen(const char *s, size_t count)
195{
196 int d0;
197 int res;
198 asm volatile("movl %2,%0\n\t"
199 "jmp 2f\n"
200 "1:\tcmpb $0,(%0)\n\t"
201 "je 3f\n\t"
202 "incl %0\n"
203 "2:\tdecl %1\n\t"
204 "cmpl $-1,%1\n\t"
205 "jne 1b\n"
206 "3:\tsubl %2,%0"
207 : "=a" (res), "=&d" (d0)
208 : "c" (s), "1" (count)
209 : "memory");
210 return res;
211}
212EXPORT_SYMBOL(strnlen);
213#endif