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_STRNCPY
34char *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		: "0" (src), "1" (dest), "2" (count) : "memory");
48	return dest;
49}
50EXPORT_SYMBOL(strncpy);
51#endif
52
53#ifdef __HAVE_ARCH_STRCAT
54char *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		: "0" (src), "1" (dest), "2" (0), "3" (0xffffffffu) : "memory");
66	return dest;
67}
68EXPORT_SYMBOL(strcat);
69#endif
70
71#ifdef __HAVE_ARCH_STRNCAT
72char *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		: "0" (src), "1" (dest), "2" (0), "3" (0xffffffffu), "g" (count)
89		: "memory");
90	return dest;
91}
92EXPORT_SYMBOL(strncat);
93#endif
94
95#ifdef __HAVE_ARCH_STRCMP
96int 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}
115EXPORT_SYMBOL(strcmp);
116#endif
117
118#ifdef __HAVE_ARCH_STRNCMP
119int 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}
140EXPORT_SYMBOL(strncmp);
141#endif
142
143#ifdef __HAVE_ARCH_STRCHR
144char *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), "0" (c)
159		: "memory");
160	return res;
161}
162EXPORT_SYMBOL(strchr);
163#endif
164
165#ifdef __HAVE_ARCH_STRLEN
166size_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), "0" (0xffffffffu)
174		: "memory");
175	return ~res - 1;
176}
177EXPORT_SYMBOL(strlen);
178#endif
179
180#ifdef __HAVE_ARCH_MEMCHR
181void *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), "0" (cs), "1" (count)
194		: "memory");
195	return res;
196}
197EXPORT_SYMBOL(memchr);
198#endif
199
200#ifdef __HAVE_ARCH_MEMSCAN
201void *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	    : "0" (addr), "1" (size), "a" (c)
211	    : "memory");
212	return addr;
213}
214EXPORT_SYMBOL(memscan);
215#endif
216
217#ifdef __HAVE_ARCH_STRNLEN
218size_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}
236EXPORT_SYMBOL(strnlen);
237#endif
238