1 #include <string.h>
2 #include <stdint.h>
3
4 #ifdef LOSCFG_KERNEL_LMS
__memset(void * dest,int c,size_t n)5 __attribute__((no_sanitize_address)) void *__memset(void *dest, int c, size_t n)
6 #else
7 void *memset(void *dest, int c, size_t n)
8 #endif
9 {
10 unsigned char *s = dest;
11 size_t k;
12
13 /* Fill head and tail with minimal branching. Each
14 * conditional ensures that all the subsequently used
15 * offsets are well-defined and in the dest region. */
16
17 if (!n) return dest;
18 s[0] = c;
19 s[n-1] = c;
20 if (n <= 2) return dest;
21 s[1] = c;
22 s[2] = c;
23 s[n-2] = c;
24 s[n-3] = c;
25 if (n <= 6) return dest;
26 s[3] = c;
27 s[n-4] = c;
28 if (n <= 8) return dest;
29
30 /* Advance pointer to align it at a 4-byte boundary,
31 * and truncate n to a multiple of 4. The previous code
32 * already took care of any head/tail that get cut off
33 * by the alignment. */
34
35 k = -(uintptr_t)s & 3;
36 s += k;
37 n -= k;
38 n &= -4;
39
40 #ifdef __GNUC__
41 typedef uint32_t __attribute__((__may_alias__)) u32;
42 typedef uint64_t __attribute__((__may_alias__)) u64;
43
44 u32 c32 = ((u32)-1)/255 * (unsigned char)c;
45
46 /* In preparation to copy 32 bytes at a time, aligned on
47 * an 8-byte bounary, fill head/tail up to 28 bytes each.
48 * As in the initial byte-based head/tail fill, each
49 * conditional below ensures that the subsequent offsets
50 * are valid (e.g. !(n<=24) implies n>=28). */
51
52 *(u32 *)(s+0) = c32;
53 *(u32 *)(s+n-4) = c32;
54 if (n <= 8) return dest;
55 *(u32 *)(s+4) = c32;
56 *(u32 *)(s+8) = c32;
57 *(u32 *)(s+n-12) = c32;
58 *(u32 *)(s+n-8) = c32;
59 if (n <= 24) return dest;
60 *(u32 *)(s+12) = c32;
61 *(u32 *)(s+16) = c32;
62 *(u32 *)(s+20) = c32;
63 *(u32 *)(s+24) = c32;
64 *(u32 *)(s+n-28) = c32;
65 *(u32 *)(s+n-24) = c32;
66 *(u32 *)(s+n-20) = c32;
67 *(u32 *)(s+n-16) = c32;
68
69 /* Align to a multiple of 8 so we can fill 64 bits at a time,
70 * and avoid writing the same bytes twice as much as is
71 * practical without introducing additional branching. */
72
73 k = 24 + ((uintptr_t)s & 4);
74 s += k;
75 n -= k;
76
77 /* If this loop is reached, 28 tail bytes have already been
78 * filled, so any remainder when n drops below 32 can be
79 * safely ignored. */
80
81 u64 c64 = c32 | ((u64)c32 << 32);
82 for (; n >= 32; n-=32, s+=32) {
83 *(u64 *)(s+0) = c64;
84 *(u64 *)(s+8) = c64;
85 *(u64 *)(s+16) = c64;
86 *(u64 *)(s+24) = c64;
87 }
88 #else
89 /* Pure C fallback with no aliasing violations. */
90 for (; n; n--, s++) *s = c;
91 #endif
92
93 return dest;
94 }
95