arch/s390/lib/string.c

   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
  12 #include <linux/types.h>
  13 #include <linux/string.h>
  14 #include <linux/export.h>
  15
  16 /*
  17  * Helper functions to find the end of a string
  18  */
  19 static inline char *__strend(const char *s)
  20 {
  21         register unsigned long r0 asm("0") = 0;
  22
  23         asm volatile ("0: srst  %0,%1\n"
  24                       "   jo    0b"
  25                       : "+d" (r0), "+a" (s) :  : "cc", "memory");
  26         return (char *) r0;
  27 }
  28
  29 static inline char *__strnend(const char *s, size_t n)
  30 {
  31         register unsigned long r0 asm("0") = 0;
  32         const char *p = s + n;
  33
  34         asm volatile ("0: srst  %0,%1\n"
  35                       "   jo    0b"
  36                       : "+d" (p), "+a" (s) : "d" (r0) : "cc", "memory");
  37         return (char *) p;
  38 }
  39
  40 /**
  41  * strlen - Find the length of a string
  42  * @s: The string to be sized
  43  *
  44  * returns the length of @s
  45  */
  46 size_t strlen(const char *s)
  47 {
  48         return __strend(s) - s;
  49 }
  50 EXPORT_SYMBOL(strlen);
  51
  52 /**
  53  * strnlen - Find the length of a length-limited string
  54  * @s: The string to be sized
  55  * @n: The maximum number of bytes to search
  56  *
  57  * returns the minimum of the length of @s and @n
  58  */
  59 size_t strnlen(const char *s, size_t n)
  60 {
  61         return __strnend(s, n) - s;
  62 }
  63 EXPORT_SYMBOL(strnlen);
  64
  65 /**
  66  * strcpy - Copy a %NUL terminated string
  67  * @dest: Where to copy the string to
  68  * @src: Where to copy the string from
  69  *
  70  * returns a pointer to @dest
  71  */
  72 char *strcpy(char *dest, const char *src)
  73 {
  74         register int r0 asm("0") = 0;
  75         char *ret = dest;
  76
  77         asm volatile ("0: mvst  %0,%1\n"
  78                       "   jo    0b"
  79                       : "+&a" (dest), "+&a" (src) : "d" (r0)
  80                       : "cc", "memory" );
  81         return ret;
  82 }
  83 EXPORT_SYMBOL(strcpy);
  84
  85 /**
  86  * strlcpy - Copy a %NUL terminated string into a sized buffer
  87  * @dest: Where to copy the string to
  88  * @src: Where to copy the string from
  89  * @size: size of destination buffer
  90  *
  91  * Compatible with *BSD: the result is always a valid
  92  * NUL-terminated string that fits in the buffer (unless,
  93  * of course, the buffer size is zero). It does not pad
  94  * out the result like strncpy() does.
  95  */
  96 size_t strlcpy(char *dest, const char *src, size_t size)
  97 {
  98         size_t ret = __strend(src) - src;
  99
 100         if (size) {
 101                 size_t len = (ret >= size) ? size-1 : ret;
 102                 dest[len] = '\0';
 103                 memcpy(dest, src, len);
 104         }
 105         return ret;
 106 }
 107 EXPORT_SYMBOL(strlcpy);
 108
 109 /**
 110  * strncpy - Copy a length-limited, %NUL-terminated string
 111  * @dest: Where to copy the string to
 112  * @src: Where to copy the string from
 113  * @n: The maximum number of bytes to copy
 114  *
 115  * The result is not %NUL-terminated if the source exceeds
 116  * @n bytes.
 117  */
 118 char *strncpy(char *dest, const char *src, size_t n)
 119 {
 120         size_t len = __strnend(src, n) - src;
 121         memset(dest + len, 0, n - len);
 122         memcpy(dest, src, len);
 123         return dest;
 124 }
 125 EXPORT_SYMBOL(strncpy);
 126
 127 /**
 128  * strcat - Append one %NUL-terminated string to another
 129  * @dest: The string to be appended to
 130  * @src: The string to append to it
 131  *
 132  * returns a pointer to @dest
 133  */
 134 char *strcat(char *dest, const char *src)
 135 {
 136         register int r0 asm("0") = 0;
 137         unsigned long dummy;
 138         char *ret = dest;
 139
 140         asm volatile ("0: srst  %0,%1\n"
 141                       "   jo    0b\n"
 142                       "1: mvst  %0,%2\n"
 143                       "   jo    1b"
 144                       : "=&a" (dummy), "+a" (dest), "+a" (src)
 145                       : "d" (r0), "0" (0UL) : "cc", "memory" );
 146         return ret;
 147 }
 148 EXPORT_SYMBOL(strcat);
 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 size_t strlcat(char *dest, const char *src, size_t n)
 157 {
 158         size_t dsize = __strend(dest) - dest;
 159         size_t len = __strend(src) - src;
 160         size_t res = dsize + len;
 161
 162         if (dsize < n) {
 163                 dest += dsize;
 164                 n -= dsize;
 165                 if (len >= n)
 166                         len = n - 1;
 167                 dest[len] = '\0';
 168                 memcpy(dest, src, len);
 169         }
 170         return res;
 171 }
 172 EXPORT_SYMBOL(strlcat);
 173
 174 /**
 175  * strncat - Append a length-limited, %NUL-terminated string to another
 176  * @dest: The string to be appended to
 177  * @src: The string to append to it
 178  * @n: The maximum numbers of bytes to copy
 179  *
 180  * returns a pointer to @dest
 181  *
 182  * Note that in contrast to strncpy, strncat ensures the result is
 183  * terminated.
 184  */
 185 char *strncat(char *dest, const char *src, size_t n)
 186 {
 187         size_t len = __strnend(src, n) - src;
 188         char *p = __strend(dest);
 189
 190         p[len] = '\0';
 191         memcpy(p, src, len);
 192         return dest;
 193 }
 194 EXPORT_SYMBOL(strncat);
 195
 196 /**
 197  * strcmp - Compare two strings
 198  * @s1: One string
 199  * @s2: Another string
 200  *
 201  * returns   0 if @s1 and @s2 are equal,
 202  *         < 0 if @s1 is less than @s2
 203  *         > 0 if @s1 is greater than @s2
 204  */
 205 int strcmp(const char *s1, const char *s2)
 206 {
 207         register int r0 asm("0") = 0;
 208         int ret = 0;
 209
 210         asm volatile ("0: clst %2,%3\n"
 211                       "   jo   0b\n"
 212                       "   je   1f\n"
 213                       "   ic   %0,0(%2)\n"
 214                       "   ic   %1,0(%3)\n"
 215                       "   sr   %0,%1\n"
 216                       "1:"
 217                       : "+d" (ret), "+d" (r0), "+a" (s1), "+a" (s2)
 218                       : : "cc", "memory");
 219         return ret;
 220 }
 221 EXPORT_SYMBOL(strcmp);
 222
 223 /**
 224  * strrchr - Find the last occurrence of a character in a string
 225  * @s: The string to be searched
 226  * @c: The character to search for
 227  */
 228 char *strrchr(const char *s, int c)
 229 {
 230        size_t len = __strend(s) - s;
 231
 232        if (len)
 233                do {
 234                        if (s[len] == (char) c)
 235                                return (char *) s + len;
 236                } while (--len > 0);
 237        return NULL;
 238 }
 239 EXPORT_SYMBOL(strrchr);
 240
 241 static inline int clcle(const char *s1, unsigned long l1,
 242                         const char *s2, unsigned long l2)
 243 {
 244         register unsigned long r2 asm("2") = (unsigned long) s1;
 245         register unsigned long r3 asm("3") = (unsigned long) l1;
 246         register unsigned long r4 asm("4") = (unsigned long) s2;
 247         register unsigned long r5 asm("5") = (unsigned long) l2;
 248         int cc;
 249
 250         asm volatile ("0: clcle %1,%3,0\n"
 251                       "   jo    0b\n"
 252                       "   ipm   %0\n"
 253                       "   srl   %0,28"
 254                       : "=&d" (cc), "+a" (r2), "+a" (r3),
 255                         "+a" (r4), "+a" (r5) : : "cc", "memory");
 256         return cc;
 257 }
 258
 259 /**
 260  * strstr - Find the first substring in a %NUL terminated string
 261  * @s1: The string to be searched
 262  * @s2: The string to search for
 263  */
 264 char *strstr(const char *s1, const char *s2)
 265 {
 266         int l1, l2;
 267
 268         l2 = __strend(s2) - s2;
 269         if (!l2)
 270                 return (char *) s1;
 271         l1 = __strend(s1) - s1;
 272         while (l1-- >= l2) {
 273                 int cc;
 274
 275                 cc = clcle(s1, l2, s2, l2);
 276                 if (!cc)
 277                         return (char *) s1;
 278                 s1++;
 279         }
 280         return NULL;
 281 }
 282 EXPORT_SYMBOL(strstr);
 283
 284 /**
 285  * memchr - Find a character in an area of memory.
 286  * @s: The memory area
 287  * @c: The byte to search for
 288  * @n: The size of the area.
 289  *
 290  * returns the address of the first occurrence of @c, or %NULL
 291  * if @c is not found
 292  */
 293 void *memchr(const void *s, int c, size_t n)
 294 {
 295         register int r0 asm("0") = (char) c;
 296         const void *ret = s + n;
 297
 298         asm volatile ("0: srst  %0,%1\n"
 299                       "   jo    0b\n"
 300                       "   jl    1f\n"
 301                       "   la    %0,0\n"
 302                       "1:"
 303                       : "+a" (ret), "+&a" (s) : "d" (r0) : "cc", "memory");
 304         return (void *) ret;
 305 }
 306 EXPORT_SYMBOL(memchr);
 307
 308 /**
 309  * memcmp - Compare two areas of memory
 310  * @s1: One area of memory
 311  * @s2: Another area of memory
 312  * @count: The size of the area.
 313  */
 314 int memcmp(const void *s1, const void *s2, size_t n)
 315 {
 316         int ret;
 317
 318         ret = clcle(s1, n, s2, n);
 319         if (ret)
 320                 ret = ret == 1 ? -1 : 1;
 321         return ret;
 322 }
 323 EXPORT_SYMBOL(memcmp);
 324
 325 /**
 326  * memscan - Find a character in an area of memory.
 327  * @s: The memory area
 328  * @c: The byte to search for
 329  * @n: The size of the area.
 330  *
 331  * returns the address of the first occurrence of @c, or 1 byte past
 332  * the area if @c is not found
 333  */
 334 void *memscan(void *s, int c, size_t n)
 335 {
 336         register int r0 asm("0") = (char) c;
 337         const void *ret = s + n;
 338
 339         asm volatile ("0: srst  %0,%1\n"
 340                       "   jo    0b\n"
 341                       : "+a" (ret), "+&a" (s) : "d" (r0) : "cc", "memory");
 342         return (void *) ret;
 343 }
 344 EXPORT_SYMBOL(memscan);