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Linux/arch/x86/lib/string_32.c

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

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