1 /*
2 * libc/stdlib/malloc/memalign.c -- memalign (`aligned malloc') function
3 *
4 * Copyright (C) 2002 NEC Corporation
5 * Copyright (C) 2002 Miles Bader <miles@gnu.org>
6 *
7 * This file is subject to the terms and conditions of the GNU Lesser
8 * General Public License. See the file COPYING.LIB in the main
9 * directory of this archive for more details.
10 *
11 * Written by Miles Bader <miles@gnu.org>
12 */
13
14 #include <errno.h>
15 #include <stdlib.h>
16 #include <unistd.h>
17 #include <sys/mman.h>
18
19 #include "malloc.h"
20 #include "heap.h"
21
22
23 /*
24 ______________________ TOTAL _________________________
25 / \
26 +---------------+-------------------------+--------------+
27 | | | |
28 +---------------+-------------------------+--------------+
29 \____ INIT ____/ \______ RETURNED _______/ \____ END ___/
30 */
31
32 void *memalign (size_t alignment, size_t size);
33 /* XXX shadow outer malloc.h */
libc_hidden_proto(memalign)34 libc_hidden_proto(memalign)
35 void *
36 memalign (size_t alignment, size_t size)
37 {
38 void *mem, *base;
39 unsigned long tot_addr, tot_end_addr, addr, end_addr;
40 struct heap_free_area **heap = &__malloc_heap;
41
42 if (unlikely(size > PTRDIFF_MAX)) {
43 __set_errno(ENOMEM);
44 return NULL;
45 }
46
47 /* Make SIZE something we like. */
48 size = HEAP_ADJUST_SIZE (size);
49
50 /* Use malloc to do the initial allocation, since it deals with getting
51 system memory. We over-allocate enough to be sure that we'll get
52 enough memory to hold a properly aligned block of size SIZE,
53 _somewhere_ in the result. */
54 mem = malloc (size + 2 * alignment);
55 if (! mem)
56 /* Allocation failed, we can't do anything. */
57 return 0;
58 if (alignment < MALLOC_ALIGNMENT)
59 return mem;
60
61 /* Remember the base-address, of the allocation, although we normally
62 use the user-address for calculations, since that's where the
63 alignment matters. */
64 base = MALLOC_BASE (mem);
65
66 /* The bounds of the initial allocation. */
67 tot_addr = (unsigned long)mem;
68 tot_end_addr = (unsigned long)base + MALLOC_SIZE (mem);
69
70 /* Find a likely place inside MEM with the right alignment. */
71 addr = MALLOC_ROUND_UP (tot_addr, alignment);
72
73 /* Unless TOT_ADDR was already aligned correctly, we need to return the
74 initial part of MEM to the heap. */
75 if (addr != tot_addr)
76 {
77 size_t init_size = addr - tot_addr;
78
79 /* Ensure that memory returned to the heap is large enough. */
80 if (init_size < HEAP_MIN_SIZE)
81 {
82 addr = MALLOC_ROUND_UP (tot_addr + HEAP_MIN_SIZE, alignment);
83 init_size = addr - tot_addr;
84 }
85
86 __heap_lock (&__malloc_heap_lock);
87 __heap_free (heap, base, init_size);
88 __heap_unlock (&__malloc_heap_lock);
89
90 /* Remember that we've freed the initial part of MEM. */
91 base += init_size;
92 }
93
94 /* Return the end part of MEM to the heap, unless it's too small. */
95 end_addr = addr + size;
96 if (end_addr + MALLOC_REALLOC_MIN_FREE_SIZE < tot_end_addr) {
97 __heap_lock (&__malloc_heap_lock);
98 __heap_free (heap, (void *)end_addr, tot_end_addr - end_addr);
99 __heap_unlock (&__malloc_heap_lock);
100 } else
101 /* We didn't free the end, so include it in the size. */
102 end_addr = tot_end_addr;
103
104 return MALLOC_SETUP (base, end_addr - (unsigned long)base);
105 }
106 weak_alias(memalign, aligned_alloc)
107 libc_hidden_def(memalign)
108