1 /* Memory allocation aligned to system page boundaries.
2
3 Copyright (C) 2005 Free Software Foundation, Inc.
4
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)
8 any later version.
9
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.
14
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,
18 USA. */
19
20 /* Written by Derek R. Price <derek@ximbiot.com>. */
21
22 #ifdef HAVE_CONFIG_H
23 # include <config.h>
24 #endif
25
26 #include "pagealign_alloc.h"
27
28 #include <errno.h>
29 #include <stdlib.h>
30
31 #include <fcntl.h>
32
33 #if HAVE_UNISTD_H
34 # include <unistd.h>
35 #endif
36
37 #if HAVE_MMAP
38 # include <sys/mman.h>
39 #endif
40
41 #include "error.h"
42 #include "exit.h"
43 #include "getpagesize.h"
44 #include "xalloc.h"
45 #include "gettext.h"
46
47 #define _(str) gettext (str)
48
49 #if HAVE_MMAP
50 /* Define MAP_FILE when it isn't otherwise. */
51 # ifndef MAP_FILE
52 # define MAP_FILE 0
53 # endif
54 /* Define MAP_FAILED for old systems which neglect to. */
55 # ifndef MAP_FAILED
56 # define MAP_FAILED ((void *)-1)
57 # endif
58 #endif
59
60
61 #if HAVE_MMAP || ! HAVE_POSIX_MEMALIGN
62
63 # if HAVE_MMAP
64 /* For each memory region, we store its size. */
65 typedef size_t info_t;
66 # else
67 /* For each memory region, we store the original pointer returned by
68 malloc(). */
69 typedef void * info_t;
70 # endif
71
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;
75 struct memnode_s
76 {
77 void *aligned_ptr;
78 info_t info;
79 memnode_t *next;
80 };
81
82 /* The list of currently allocated memory regions. */
83 static memnode_t *memnode_table = NULL;
84
85
86 static void
new_memnode(void * aligned_ptr,info_t info)87 new_memnode (void *aligned_ptr, info_t info)
88 {
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;
94 }
95
96
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. */
99 static info_t
get_memnode(void * aligned_ptr)100 get_memnode (void *aligned_ptr)
101 {
102 info_t ret;
103 memnode_t *c;
104 memnode_t **p_next = &memnode_table;
105
106 for (c = *p_next; c != NULL; p_next = &c->next, c = c->next)
107 if (c->aligned_ptr == aligned_ptr)
108 break;
109
110 if (c == NULL)
111 /* An attempt to free untracked memory. A wrong pointer was passed
112 to pagealign_free(). */
113 abort ();
114
115 /* Remove this entry from the list, save the return value, and free it. */
116 *p_next = c->next;
117 ret = c->info;
118 free (c);
119
120 return ret;
121 }
122
123 #endif /* HAVE_MMAP || !HAVE_POSIX_MEMALIGN */
124
125
126 void *
pagealign_alloc(size_t size)127 pagealign_alloc (size_t size)
128 {
129 void *ret;
130 #if HAVE_MMAP
131 # ifdef HAVE_MAP_ANONYMOUS
132 const int fd = -1;
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;
139 if (fd == -1)
140 {
141 fd = open ("/dev/zero", O_RDONLY, 0666);
142 if (fd < 0)
143 error (EXIT_FAILURE, errno, _("Failed to open /dev/zero for read"));
144 }
145 # endif /* HAVE_MAP_ANONYMOUS */
146 ret = mmap (NULL, size, PROT_READ | PROT_WRITE, flags, fd, 0);
147 if (ret == MAP_FAILED)
148 return NULL;
149 new_memnode (ret, size);
150 #elif HAVE_POSIX_MEMALIGN
151 int status = posix_memalign (&ret, getpagesize (), size);
152 if (status)
153 {
154 errno = status;
155 return NULL;
156 }
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)
161 {
162 /* Set errno. We don't know whether malloc already set errno: some
163 implementations of malloc do, some don't. */
164 errno = ENOMEM;
165 return NULL;
166 }
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 */
171 return ret;
172 }
173
174
175 void *
pagealign_xalloc(size_t size)176 pagealign_xalloc (size_t size)
177 {
178 void *ret;
179
180 ret = pagealign_alloc (size);
181 if (ret == NULL)
182 xalloc_die ();
183 return ret;
184 }
185
186
187 void
pagealign_free(void * aligned_ptr)188 pagealign_free (void *aligned_ptr)
189 {
190 #if HAVE_MMAP
191 if (munmap (aligned_ptr, get_memnode (aligned_ptr)) < 0)
192 error (EXIT_FAILURE, errno, "Failed to unmap memory");
193 #elif HAVE_POSIX_MEMALIGN
194 free (aligned_ptr);
195 #else
196 free (get_memnode (aligned_ptr));
197 #endif
198 }
199