1// SPDX-License-Identifier: GPL-2.0
2/*
3 *    Optimized string functions
4 *
5 *  S390 version
6 *    Copyright IBM Corp. 2004
7 *    Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
8 */
9
10#define IN_ARCH_STRING_C 1
11#ifndef __NO_FORTIFY
12# define __NO_FORTIFY
13#endif
14
15#include <linux/types.h>
16#include <linux/string.h>
17#include <linux/export.h>
18
19/*
20 * Helper functions to find the end of a string
21 */
22static inline char *__strend(const char *s)
23{
24	unsigned long e = 0;
25
26	asm volatile(
27		"	lghi	0,0\n"
28		"0:	srst	%[e],%[s]\n"
29		"	jo	0b\n"
30		: [e] "+&a" (e), [s] "+&a" (s)
31		:
32		: "cc", "memory", "0");
33	return (char *)e;
34}
35
36static inline char *__strnend(const char *s, size_t n)
37{
38	const char *p = s + n;
39
40	asm volatile(
41		"	lghi	0,0\n"
42		"0:	srst	%[p],%[s]\n"
43		"	jo	0b\n"
44		: [p] "+&d" (p), [s] "+&a" (s)
45		:
46		: "cc", "memory", "0");
47	return (char *)p;
48}
49
50/**
51 * strlen - Find the length of a string
52 * @s: The string to be sized
53 *
54 * returns the length of @s
55 */
56#ifdef __HAVE_ARCH_STRLEN
57size_t strlen(const char *s)
58{
59	return __strend(s) - s;
60}
61EXPORT_SYMBOL(strlen);
62#endif
63
64/**
65 * strnlen - Find the length of a length-limited string
66 * @s: The string to be sized
67 * @n: The maximum number of bytes to search
68 *
69 * returns the minimum of the length of @s and @n
70 */
71#ifdef __HAVE_ARCH_STRNLEN
72size_t strnlen(const char *s, size_t n)
73{
74	return __strnend(s, n) - s;
75}
76EXPORT_SYMBOL(strnlen);
77#endif
78
79/**
80 * strcpy - Copy a %NUL terminated string
81 * @dest: Where to copy the string to
82 * @src: Where to copy the string from
83 *
84 * returns a pointer to @dest
85 */
86#ifdef __HAVE_ARCH_STRCPY
87char *strcpy(char *dest, const char *src)
88{
89	char *ret = dest;
90
91	asm volatile(
92		"	lghi	0,0\n"
93		"0:	mvst	%[dest],%[src]\n"
94		"	jo	0b\n"
95		: [dest] "+&a" (dest), [src] "+&a" (src)
96		:
97		: "cc", "memory", "0");
98	return ret;
99}
100EXPORT_SYMBOL(strcpy);
101#endif
102
103/**
104 * strncpy - Copy a length-limited, %NUL-terminated string
105 * @dest: Where to copy the string to
106 * @src: Where to copy the string from
107 * @n: The maximum number of bytes to copy
108 *
109 * The result is not %NUL-terminated if the source exceeds
110 * @n bytes.
111 */
112#ifdef __HAVE_ARCH_STRNCPY
113char *strncpy(char *dest, const char *src, size_t n)
114{
115	size_t len = __strnend(src, n) - src;
116	memset(dest + len, 0, n - len);
117	memcpy(dest, src, len);
118	return dest;
119}
120EXPORT_SYMBOL(strncpy);
121#endif
122
123/**
124 * strcat - Append one %NUL-terminated string to another
125 * @dest: The string to be appended to
126 * @src: The string to append to it
127 *
128 * returns a pointer to @dest
129 */
130#ifdef __HAVE_ARCH_STRCAT
131char *strcat(char *dest, const char *src)
132{
133	unsigned long dummy = 0;
134	char *ret = dest;
135
136	asm volatile(
137		"	lghi	0,0\n"
138		"0:	srst	%[dummy],%[dest]\n"
139		"	jo	0b\n"
140		"1:	mvst	%[dummy],%[src]\n"
141		"	jo	1b\n"
142		: [dummy] "+&a" (dummy), [dest] "+&a" (dest), [src] "+&a" (src)
143		:
144		: "cc", "memory", "0");
145	return ret;
146}
147EXPORT_SYMBOL(strcat);
148#endif
149
150/**
151 * strlcat - Append a length-limited, %NUL-terminated string to another
152 * @dest: The string to be appended to
153 * @src: The string to append to it
154 * @n: The size of the destination buffer.
155 */
156#ifdef __HAVE_ARCH_STRLCAT
157size_t strlcat(char *dest, const char *src, size_t n)
158{
159	size_t dsize = __strend(dest) - dest;
160	size_t len = __strend(src) - src;
161	size_t res = dsize + len;
162
163	if (dsize < n) {
164		dest += dsize;
165		n -= dsize;
166		if (len >= n)
167			len = n - 1;
168		dest[len] = '\0';
169		memcpy(dest, src, len);
170	}
171	return res;
172}
173EXPORT_SYMBOL(strlcat);
174#endif
175
176/**
177 * strncat - Append a length-limited, %NUL-terminated string to another
178 * @dest: The string to be appended to
179 * @src: The string to append to it
180 * @n: The maximum numbers of bytes to copy
181 *
182 * returns a pointer to @dest
183 *
184 * Note that in contrast to strncpy, strncat ensures the result is
185 * terminated.
186 */
187#ifdef __HAVE_ARCH_STRNCAT
188char *strncat(char *dest, const char *src, size_t n)
189{
190	size_t len = __strnend(src, n) - src;
191	char *p = __strend(dest);
192
193	p[len] = '\0';
194	memcpy(p, src, len);
195	return dest;
196}
197EXPORT_SYMBOL(strncat);
198#endif
199
200/**
201 * strcmp - Compare two strings
202 * @s1: One string
203 * @s2: Another string
204 *
205 * returns   0 if @s1 and @s2 are equal,
206 *	   < 0 if @s1 is less than @s2
207 *	   > 0 if @s1 is greater than @s2
208 */
209#ifdef __HAVE_ARCH_STRCMP
210int strcmp(const char *s1, const char *s2)
211{
212	int ret = 0;
213
214	asm volatile(
215		"	lghi	0,0\n"
216		"0:	clst	%[s1],%[s2]\n"
217		"	jo	0b\n"
218		"	je	1f\n"
219		"	ic	%[ret],0(%[s1])\n"
220		"	ic	0,0(%[s2])\n"
221		"	sr	%[ret],0\n"
222		"1:"
223		: [ret] "+&d" (ret), [s1] "+&a" (s1), [s2] "+&a" (s2)
224		:
225		: "cc", "memory", "0");
226	return ret;
227}
228EXPORT_SYMBOL(strcmp);
229#endif
230
231static inline int clcle(const char *s1, unsigned long l1,
232			const char *s2, unsigned long l2)
233{
234	union register_pair r1 = { .even = (unsigned long)s1, .odd = l1, };
235	union register_pair r3 = { .even = (unsigned long)s2, .odd = l2, };
236	int cc;
237
238	asm volatile(
239		"0:	clcle	%[r1],%[r3],0\n"
240		"	jo	0b\n"
241		"	ipm	%[cc]\n"
242		"	srl	%[cc],28\n"
243		: [cc] "=&d" (cc), [r1] "+&d" (r1.pair), [r3] "+&d" (r3.pair)
244		:
245		: "cc", "memory");
246	return cc;
247}
248
249/**
250 * strstr - Find the first substring in a %NUL terminated string
251 * @s1: The string to be searched
252 * @s2: The string to search for
253 */
254#ifdef __HAVE_ARCH_STRSTR
255char *strstr(const char *s1, const char *s2)
256{
257	int l1, l2;
258
259	l2 = __strend(s2) - s2;
260	if (!l2)
261		return (char *) s1;
262	l1 = __strend(s1) - s1;
263	while (l1-- >= l2) {
264		int cc;
265
266		cc = clcle(s1, l2, s2, l2);
267		if (!cc)
268			return (char *) s1;
269		s1++;
270	}
271	return NULL;
272}
273EXPORT_SYMBOL(strstr);
274#endif
275
276/**
277 * memchr - Find a character in an area of memory.
278 * @s: The memory area
279 * @c: The byte to search for
280 * @n: The size of the area.
281 *
282 * returns the address of the first occurrence of @c, or %NULL
283 * if @c is not found
284 */
285#ifdef __HAVE_ARCH_MEMCHR
286void *memchr(const void *s, int c, size_t n)
287{
288	const void *ret = s + n;
289
290	asm volatile(
291		"	lgr	0,%[c]\n"
292		"0:	srst	%[ret],%[s]\n"
293		"	jo	0b\n"
294		"	jl	1f\n"
295		"	la	%[ret],0\n"
296		"1:"
297		: [ret] "+&a" (ret), [s] "+&a" (s)
298		: [c] "d" (c)
299		: "cc", "memory", "0");
300	return (void *) ret;
301}
302EXPORT_SYMBOL(memchr);
303#endif
304
305/**
306 * memcmp - Compare two areas of memory
307 * @s1: One area of memory
308 * @s2: Another area of memory
309 * @n: The size of the area.
310 */
311#ifdef __HAVE_ARCH_MEMCMP
312int memcmp(const void *s1, const void *s2, size_t n)
313{
314	int ret;
315
316	ret = clcle(s1, n, s2, n);
317	if (ret)
318		ret = ret == 1 ? -1 : 1;
319	return ret;
320}
321EXPORT_SYMBOL(memcmp);
322#endif
323
324/**
325 * memscan - Find a character in an area of memory.
326 * @s: The memory area
327 * @c: The byte to search for
328 * @n: The size of the area.
329 *
330 * returns the address of the first occurrence of @c, or 1 byte past
331 * the area if @c is not found
332 */
333#ifdef __HAVE_ARCH_MEMSCAN
334void *memscan(void *s, int c, size_t n)
335{
336	const void *ret = s + n;
337
338	asm volatile(
339		"	lgr	0,%[c]\n"
340		"0:	srst	%[ret],%[s]\n"
341		"	jo	0b\n"
342		: [ret] "+&a" (ret), [s] "+&a" (s)
343		: [c] "d" (c)
344		: "cc", "memory", "0");
345	return (void *)ret;
346}
347EXPORT_SYMBOL(memscan);
348#endif
349