tools/testing/selftests/kvm/lib/string_override.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 #include <stddef.h>
   3
   4 /*
   5  * Override the "basic" built-in string helpers so that they can be used in
   6  * guest code.  KVM selftests don't support dynamic loading in guest code and
   7  * will jump into the weeds if the compiler decides to insert an out-of-line
   8  * call via the PLT.
   9  */
  10 int memcmp(const void *cs, const void *ct, size_t count)
  11 {
  12         const unsigned char *su1, *su2;
  13         int res = 0;
  14
  15         for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--) {
  16                 if ((res = *su1 - *su2) != 0)
  17                         break;
  18         }
  19         return res;
  20 }
  21
  22 void *memcpy(void *dest, const void *src, size_t count)
  23 {
  24         char *tmp = dest;
  25         const char *s = src;
  26
  27         while (count--)
  28                 *tmp++ = *s++;
  29         return dest;
  30 }
  31
  32 void *memset(void *s, int c, size_t count)
  33 {
  34         char *xs = s;
  35
  36         while (count--)
  37                 *xs++ = c;
  38         return s;
  39 }
  40
  41 size_t strnlen(const char *s, size_t count)
  42 {
  43         const char *sc;
  44
  45         for (sc = s; count-- && *sc != '\0'; ++sc)
  46                 /* nothing */;
  47         return sc - s;
  48 }