1/*
2 * @TAG(OTHER_MIT)
3 */
4/*
5 * Copyright �� 2005-2014 Rich Felker, et al.
6 *
7 * Permission is hereby granted, free of charge, to any person obtaining
8 * a copy of this software and associated documentation files (the
9 * "Software"), to deal in the Software without restriction, including
10 * without limitation the rights to use, copy, modify, merge, publish,
11 * distribute, sublicense, and/or sell copies of the Software, and to
12 * permit persons to whom the Software is furnished to do so, subject to
13 * the following conditions:
14 *
15 * The above copyright notice and this permission notice shall be
16 * included in all copies or substantial portions of the Software.
17 *
18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
19 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
20 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
21 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
22 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
23 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
24 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
25 */
26
27#include "util.h"
28
29void *__sel4runtime_memset(void *dest, int c, sel4runtime_size_t n)
30{
31    unsigned char *s = dest;
32    sel4runtime_size_t k;
33
34    /* Fill head and tail with minimal branching. Each
35     * conditional ensures that all the subsequently used
36     * offsets are well-defined and in the dest region. */
37
38    if (!n) {
39        return dest;
40    }
41    s[0] = s[n - 1] = c;
42    if (n <= 2) {
43        return dest;
44    }
45    s[1] = s[n - 2] = c;
46    s[2] = s[n - 3] = c;
47    if (n <= 6) {
48        return dest;
49    }
50    s[3] = s[n - 4] = c;
51    if (n <= 8) {
52        return dest;
53    }
54
55    /* Advance pointer to align it at a 4-byte boundary,
56     * and truncate n to a multiple of 4. The previous code
57     * already took care of any head/tail that get cut off
58     * by the alignment. */
59
60    k = -(sel4runtime_uintptr_t)s & 3;
61    s += k;
62    n -= k;
63    n &= -4;
64
65#ifdef __GNUC__
66    typedef sel4runtime_uint32_t __attribute__((__may_alias__)) u32;
67    typedef sel4runtime_uint64_t __attribute__((__may_alias__)) u64;
68
69    u32 c32 = ((u32) - 1) / 255 * (unsigned char)c;
70
71    /* In preparation to copy 32 bytes at a time, aligned on
72     * an 8-byte bounary, fill head/tail up to 28 bytes each.
73     * As in the initial byte-based head/tail fill, each
74     * conditional below ensures that the subsequent offsets
75     * are valid (e.g. !(n<=24) implies n>=28). */
76
77    *(u32 *)(s + 0) = c32;
78    *(u32 *)(s + n - 4) = c32;
79    if (n <= 8) {
80        return dest;
81    }
82    *(u32 *)(s + 4) = c32;
83    *(u32 *)(s + 8) = c32;
84    *(u32 *)(s + n - 12) = c32;
85    *(u32 *)(s + n - 8) = c32;
86    if (n <= 24) {
87        return dest;
88    }
89    *(u32 *)(s + 12) = c32;
90    *(u32 *)(s + 16) = c32;
91    *(u32 *)(s + 20) = c32;
92    *(u32 *)(s + 24) = c32;
93    *(u32 *)(s + n - 28) = c32;
94    *(u32 *)(s + n - 24) = c32;
95    *(u32 *)(s + n - 20) = c32;
96    *(u32 *)(s + n - 16) = c32;
97
98    /* Align to a multiple of 8 so we can fill 64 bits at a time,
99     * and avoid writing the same bytes twice as much as is
100     * practical without introducing additional branching. */
101
102    k = 24 + ((sel4runtime_uintptr_t)s & 4);
103    s += k;
104    n -= k;
105
106    /* If this loop is reached, 28 tail bytes have already been
107     * filled, so any remainder when n drops below 32 can be
108     * safely ignored. */
109
110    u64 c64 = c32 | ((u64)c32 << 32);
111    for (; n >= 32; n -= 32, s += 32) {
112        *(u64 *)(s + 0) = c64;
113        *(u64 *)(s + 8) = c64;
114        *(u64 *)(s + 16) = c64;
115        *(u64 *)(s + 24) = c64;
116    }
117#else
118    /* Pure C fallback with no aliasing violations. */
119    for (; n; n--, s++) {
120        *s = c;
121    }
122#endif
123
124    return dest;
125}
126