1 /* Memory allocation aligned to system page boundaries.
3 Copyright (C) 2005 Free Software Foundation, Inc.
5 This program is free software; you can redistribute it and/or modify it
6 under the terms of the GNU General Public License as published
7 by the Free Software Foundation; either version 2, or (at your option)
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 General Public License for more details.
15 You should have received a copy of the GNU General Public
16 License along with this program; if not, write to the Free Software
17 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
20 /* Written by Derek R. Price <derek@ximbiot.com>. */
26 #include "pagealign_alloc.h"
38 # include <sys/mman.h>
43 #include "getpagesize.h"
47 #define _(str) gettext (str)
50 /* Define MAP_FILE when it isn't otherwise. */
54 /* Define MAP_FAILED for old systems which neglect to. */
56 # define MAP_FAILED ((void *)-1)
61 #if HAVE_MMAP || ! HAVE_POSIX_MEMALIGN
64 /* For each memory region, we store its size. */
65 typedef size_t info_t;
67 /* For each memory region, we store the original pointer returned by
69 typedef void * info_t;
72 /* A simple linked list of allocated memory regions. It is probably not the
73 most efficient way to store these, but anyway... */
74 typedef struct memnode_s memnode_t;
82 /* The list of currently allocated memory regions. */
83 static memnode_t *memnode_table = NULL;
87 new_memnode (void *aligned_ptr, info_t info)
89 memnode_t *new_node = (memnode_t *) xmalloc (sizeof (memnode_t));
90 new_node->aligned_ptr = aligned_ptr;
91 new_node->info = info;
92 new_node->next = memnode_table;
93 memnode_table = new_node;
97 /* Dispose of the memnode containing a map for the ALIGNED_PTR in question
98 and return the content of the node's INFO field. */
100 get_memnode (void *aligned_ptr)
104 memnode_t **p_next = &memnode_table;
106 for (c = *p_next; c != NULL; p_next = &c->next, c = c->next)
107 if (c->aligned_ptr == aligned_ptr)
111 /* An attempt to free untracked memory. A wrong pointer was passed
112 to pagealign_free(). */
115 /* Remove this entry from the list, save the return value, and free it. */
123 #endif /* HAVE_MMAP || !HAVE_POSIX_MEMALIGN */
127 pagealign_alloc (size_t size)
131 # ifdef HAVE_MAP_ANONYMOUS
133 const int flags = MAP_ANONYMOUS | MAP_PRIVATE;
134 # else /* !HAVE_MAP_ANONYMOUS */
135 static int fd = -1; /* Only open /dev/zero once in order to avoid limiting
136 the amount of memory we may allocate based on the
137 number of open file descriptors. */
138 const int flags = MAP_FILE | MAP_PRIVATE;
141 fd = open ("/dev/zero", O_RDONLY, 0666);
143 error (EXIT_FAILURE, errno, _("Failed to open /dev/zero for read"));
145 # endif /* HAVE_MAP_ANONYMOUS */
146 ret = mmap (NULL, size, PROT_READ | PROT_WRITE, flags, fd, 0);
147 if (ret == MAP_FAILED)
149 new_memnode (ret, size);
150 #elif HAVE_POSIX_MEMALIGN
151 int status = posix_memalign (&ret, getpagesize (), size);
157 #else /* !HAVE_MMAP && !HAVE_POSIX_MEMALIGN */
158 size_t pagesize = getpagesize ();
159 void *unaligned_ptr = malloc (size + pagesize - 1);
160 if (unaligned_ptr == NULL)
162 /* Set errno. We don't know whether malloc already set errno: some
163 implementations of malloc do, some don't. */
167 ret = (char *) unaligned_ptr
168 + ((- (unsigned long) unaligned_ptr) & (pagesize - 1));
169 new_memnode (ret, unaligned_ptr);
170 #endif /* HAVE_MMAP && HAVE_POSIX_MEMALIGN */
176 pagealign_xalloc (size_t size)
180 ret = pagealign_alloc (size);
188 pagealign_free (void *aligned_ptr)
191 if (munmap (aligned_ptr, get_memnode (aligned_ptr)) < 0)
192 error (EXIT_FAILURE, errno, "Failed to unmap memory");
193 #elif HAVE_POSIX_MEMALIGN
196 free (get_memnode (aligned_ptr));