LXR linux/arch/x86/boot/compressed/string.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * This provides an optimized implementation of memcpy, and a simplified
   4 * implementation of memset and memmove. These are used here because the
   5 * standard kernel runtime versions are not yet available and we don't
   6 * trust the gcc built-in implementations as they may do unexpected things
   7 * (e.g. FPU ops) in the minimal decompression stub execution environment.
   8 */
   9#include "error.h"
  10
  11#include "../string.c"
  12
  13#ifdef CONFIG_X86_32
  14static void *____memcpy(void *dest, const void *src, size_t n)
  15{
  16        int d0, d1, d2;
  17        asm volatile(
  18                "rep ; movsl\n\t"
  19                "movl %4,%%ecx\n\t"
  20                "rep ; movsb\n\t"
  21                : "=&c" (d0), "=&D" (d1), "=&S" (d2)
  22                : "0" (n >> 2), "g" (n & 3), "1" (dest), "2" (src)
  23                : "memory");
  24
  25        return dest;
  26}
  27#else
  28static void *____memcpy(void *dest, const void *src, size_t n)
  29{
  30        long d0, d1, d2;
  31        asm volatile(
  32                "rep ; movsq\n\t"
  33                "movq %4,%%rcx\n\t"
  34                "rep ; movsb\n\t"
  35                : "=&c" (d0), "=&D" (d1), "=&S" (d2)
  36                : "0" (n >> 3), "g" (n & 7), "1" (dest), "2" (src)
  37                : "memory");
  38
  39        return dest;
  40}
  41#endif
  42
  43void *memset(void *s, int c, size_t n)
  44{
  45        int i;
  46        char *ss = s;
  47
  48        for (i = 0; i < n; i++)
  49                ss[i] = c;
  50        return s;
  51}
  52
  53void *memmove(void *dest, const void *src, size_t n)
  54{
  55        unsigned char *d = dest;
  56        const unsigned char *s = src;
  57
  58        if (d <= s || d - s >= n)
  59                return ____memcpy(dest, src, n);
  60
  61        while (n-- > 0)
  62                d[n] = s[n];
  63
  64        return dest;
  65}
  66
  67/* Detect and warn about potential overlaps, but handle them with memmove. */
  68void *memcpy(void *dest, const void *src, size_t n)
  69{
  70        if (dest > src && dest - src < n) {
  71                warn("Avoiding potentially unsafe overlapping memcpy()!");
  72                return memmove(dest, src, n);
  73        }
  74        return ____memcpy(dest, src, n);
  75}
  76
  77#ifdef CONFIG_KASAN
  78extern void *__memset(void *s, int c, size_t n) __alias(memset);
  79extern void *__memmove(void *dest, const void *src, size_t n) __alias(memmove);
  80extern void *__memcpy(void *dest, const void *src, size_t n) __alias(memcpy);
  81#endif
  82