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 14 static 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 28 static 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 43 void *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 53 void *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. */ 68 void *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 78 extern void *__memset(void *s, int c, size_t n) __alias(memset); 79 extern void *__memmove(void *dest, const void *src, size_t n) __alias(memmove); 80 extern void *__memcpy(void *dest, const void *src, size_t n) __alias(memcpy); 81 #endif 82