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
____memcpy(void * dest,const void * src,size_t n)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
____memcpy(void * dest,const void * src,size_t n)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 
memset(void * s,int c,size_t n)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 
memmove(void * dest,const void * src,size_t n)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. */
memcpy(void * dest,const void * src,size_t n)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