1// SPDX-License-Identifier: GPL-2.0-only
2/* -*- linux-c -*- ------------------------------------------------------- *
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 * Copyright 2007 rPath, Inc. - All Rights Reserved
6 *
7 * ----------------------------------------------------------------------- */
8
9/*
10 * Very basic string functions
11 */
12
13#include <linux/types.h>
14#include <linux/compiler.h>
15#include <linux/errno.h>
16#include <linux/limits.h>
17#include <asm/asm.h>
18#include "ctype.h"
19#include "string.h"
20
21#define KSTRTOX_OVERFLOW (1U << 31)
22
23/*
24 * Undef these macros so that the functions that we provide
25 * here will have the correct names regardless of how string.h
26 * may have chosen to #define them.
27 */
28#undef memcpy
29#undef memset
30#undef memcmp
31
32int memcmp(const void *s1, const void *s2, size_t len)
33{
34 bool diff;
35 asm("repe; cmpsb" CC_SET(nz)
36 : CC_OUT(nz) (diff), "+D" (s1), "+S" (s2), "+c" (len));
37 return diff;
38}
39
40/*
41 * Clang may lower `memcmp == 0` to `bcmp == 0`.
42 */
43int bcmp(const void *s1, const void *s2, size_t len)
44{
45 return memcmp(s1, s2, len);
46}
47
48int strcmp(const char *str1, const char *str2)
49{
50 const unsigned char *s1 = (const unsigned char *)str1;
51 const unsigned char *s2 = (const unsigned char *)str2;
52 int delta = 0;
53
54 while (*s1 || *s2) {
55 delta = *s1 - *s2;
56 if (delta)
57 return delta;
58 s1++;
59 s2++;
60 }
61 return 0;
62}
63
64int strncmp(const char *cs, const char *ct, size_t count)
65{
66 unsigned char c1, c2;
67
68 while (count) {
69 c1 = *cs++;
70 c2 = *ct++;
71 if (c1 != c2)
72 return c1 < c2 ? -1 : 1;
73 if (!c1)
74 break;
75 count--;
76 }
77 return 0;
78}
79
80size_t strnlen(const char *s, size_t maxlen)
81{
82 const char *es = s;
83 while (*es && maxlen) {
84 es++;
85 maxlen--;
86 }
87
88 return (es - s);
89}
90
91unsigned int atou(const char *s)
92{
93 unsigned int i = 0;
94 while (isdigit(ch: *s))
95 i = i * 10 + (*s++ - '0');
96 return i;
97}
98
99/* Works only for digits and letters, but small and fast */
100#define TOLOWER(x) ((x) | 0x20)
101
102static unsigned int simple_guess_base(const char *cp)
103{
104 if (cp[0] == '0') {
105 if (TOLOWER(cp[1]) == 'x' && isxdigit(ch: cp[2]))
106 return 16;
107 else
108 return 8;
109 } else {
110 return 10;
111 }
112}
113
114/**
115 * simple_strtoull - convert a string to an unsigned long long
116 * @cp: The start of the string
117 * @endp: A pointer to the end of the parsed string will be placed here
118 * @base: The number base to use
119 */
120unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base)
121{
122 unsigned long long result = 0;
123
124 if (!base)
125 base = simple_guess_base(cp);
126
127 if (base == 16 && cp[0] == '0' && TOLOWER(cp[1]) == 'x')
128 cp += 2;
129
130 while (isxdigit(ch: *cp)) {
131 unsigned int value;
132
133 value = isdigit(ch: *cp) ? *cp - '0' : TOLOWER(*cp) - 'a' + 10;
134 if (value >= base)
135 break;
136 result = result * base + value;
137 cp++;
138 }
139 if (endp)
140 *endp = (char *)cp;
141
142 return result;
143}
144
145long simple_strtol(const char *cp, char **endp, unsigned int base)
146{
147 if (*cp == '-')
148 return -simple_strtoull(cp: cp + 1, endp, base);
149
150 return simple_strtoull(cp, endp, base);
151}
152
153/**
154 * strlen - Find the length of a string
155 * @s: The string to be sized
156 */
157size_t strlen(const char *s)
158{
159 const char *sc;
160
161 for (sc = s; *sc != '\0'; ++sc)
162 /* nothing */;
163 return sc - s;
164}
165
166/**
167 * strstr - Find the first substring in a %NUL terminated string
168 * @s1: The string to be searched
169 * @s2: The string to search for
170 */
171char *strstr(const char *s1, const char *s2)
172{
173 size_t l1, l2;
174
175 l2 = strlen(s: s2);
176 if (!l2)
177 return (char *)s1;
178 l1 = strlen(s: s1);
179 while (l1 >= l2) {
180 l1--;
181 if (!memcmp(s1, s2, len: l2))
182 return (char *)s1;
183 s1++;
184 }
185 return NULL;
186}
187
188/**
189 * strchr - Find the first occurrence of the character c in the string s.
190 * @s: the string to be searched
191 * @c: the character to search for
192 */
193char *strchr(const char *s, int c)
194{
195 while (*s != (char)c)
196 if (*s++ == '\0')
197 return NULL;
198 return (char *)s;
199}
200
201static inline u64 __div_u64_rem(u64 dividend, u32 divisor, u32 *remainder)
202{
203 union {
204 u64 v64;
205 u32 v32[2];
206 } d = { dividend };
207 u32 upper;
208
209 upper = d.v32[1];
210 d.v32[1] = 0;
211 if (upper >= divisor) {
212 d.v32[1] = upper / divisor;
213 upper %= divisor;
214 }
215 asm ("divl %2" : "=a" (d.v32[0]), "=d" (*remainder) :
216 "rm" (divisor), "0" (d.v32[0]), "1" (upper));
217 return d.v64;
218}
219
220static inline u64 __div_u64(u64 dividend, u32 divisor)
221{
222 u32 remainder;
223
224 return __div_u64_rem(dividend, divisor, remainder: &remainder);
225}
226
227static inline char _tolower(const char c)
228{
229 return c | 0x20;
230}
231
232static const char *_parse_integer_fixup_radix(const char *s, unsigned int *base)
233{
234 if (*base == 0) {
235 if (s[0] == '0') {
236 if (_tolower(c: s[1]) == 'x' && isxdigit(ch: s[2]))
237 *base = 16;
238 else
239 *base = 8;
240 } else
241 *base = 10;
242 }
243 if (*base == 16 && s[0] == '0' && _tolower(c: s[1]) == 'x')
244 s += 2;
245 return s;
246}
247
248/*
249 * Convert non-negative integer string representation in explicitly given radix
250 * to an integer.
251 * Return number of characters consumed maybe or-ed with overflow bit.
252 * If overflow occurs, result integer (incorrect) is still returned.
253 *
254 * Don't you dare use this function.
255 */
256static unsigned int _parse_integer(const char *s,
257 unsigned int base,
258 unsigned long long *p)
259{
260 unsigned long long res;
261 unsigned int rv;
262
263 res = 0;
264 rv = 0;
265 while (1) {
266 unsigned int c = *s;
267 unsigned int lc = c | 0x20; /* don't tolower() this line */
268 unsigned int val;
269
270 if ('0' <= c && c <= '9')
271 val = c - '0';
272 else if ('a' <= lc && lc <= 'f')
273 val = lc - 'a' + 10;
274 else
275 break;
276
277 if (val >= base)
278 break;
279 /*
280 * Check for overflow only if we are within range of
281 * it in the max base we support (16)
282 */
283 if (unlikely(res & (~0ull << 60))) {
284 if (res > __div_u64(ULLONG_MAX - val, divisor: base))
285 rv |= KSTRTOX_OVERFLOW;
286 }
287 res = res * base + val;
288 rv++;
289 s++;
290 }
291 *p = res;
292 return rv;
293}
294
295static int _kstrtoull(const char *s, unsigned int base, unsigned long long *res)
296{
297 unsigned long long _res;
298 unsigned int rv;
299
300 s = _parse_integer_fixup_radix(s, base: &base);
301 rv = _parse_integer(s, base, p: &_res);
302 if (rv & KSTRTOX_OVERFLOW)
303 return -ERANGE;
304 if (rv == 0)
305 return -EINVAL;
306 s += rv;
307 if (*s == '\n')
308 s++;
309 if (*s)
310 return -EINVAL;
311 *res = _res;
312 return 0;
313}
314
315/**
316 * kstrtoull - convert a string to an unsigned long long
317 * @s: The start of the string. The string must be null-terminated, and may also
318 * include a single newline before its terminating null. The first character
319 * may also be a plus sign, but not a minus sign.
320 * @base: The number base to use. The maximum supported base is 16. If base is
321 * given as 0, then the base of the string is automatically detected with the
322 * conventional semantics - If it begins with 0x the number will be parsed as a
323 * hexadecimal (case insensitive), if it otherwise begins with 0, it will be
324 * parsed as an octal number. Otherwise it will be parsed as a decimal.
325 * @res: Where to write the result of the conversion on success.
326 *
327 * Returns 0 on success, -ERANGE on overflow and -EINVAL on parsing error.
328 * Used as a replacement for the obsolete simple_strtoull. Return code must
329 * be checked.
330 */
331int kstrtoull(const char *s, unsigned int base, unsigned long long *res)
332{
333 if (s[0] == '+')
334 s++;
335 return _kstrtoull(s, base, res);
336}
337
338static int _kstrtoul(const char *s, unsigned int base, unsigned long *res)
339{
340 unsigned long long tmp;
341 int rv;
342
343 rv = kstrtoull(s, base, res: &tmp);
344 if (rv < 0)
345 return rv;
346 if (tmp != (unsigned long)tmp)
347 return -ERANGE;
348 *res = tmp;
349 return 0;
350}
351
352/**
353 * boot_kstrtoul - convert a string to an unsigned long
354 * @s: The start of the string. The string must be null-terminated, and may also
355 * include a single newline before its terminating null. The first character
356 * may also be a plus sign, but not a minus sign.
357 * @base: The number base to use. The maximum supported base is 16. If base is
358 * given as 0, then the base of the string is automatically detected with the
359 * conventional semantics - If it begins with 0x the number will be parsed as a
360 * hexadecimal (case insensitive), if it otherwise begins with 0, it will be
361 * parsed as an octal number. Otherwise it will be parsed as a decimal.
362 * @res: Where to write the result of the conversion on success.
363 *
364 * Returns 0 on success, -ERANGE on overflow and -EINVAL on parsing error.
365 * Used as a replacement for the simple_strtoull.
366 */
367int boot_kstrtoul(const char *s, unsigned int base, unsigned long *res)
368{
369 /*
370 * We want to shortcut function call, but
371 * __builtin_types_compatible_p(unsigned long, unsigned long long) = 0.
372 */
373 if (sizeof(unsigned long) == sizeof(unsigned long long) &&
374 __alignof__(unsigned long) == __alignof__(unsigned long long))
375 return kstrtoull(s, base, res: (unsigned long long *)res);
376 else
377 return _kstrtoul(s, base, res);
378}
379

source code of linux/arch/x86/boot/string.c