external/gpl2/xcvs/dist/lib/pagealign_alloc.c

   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
  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
 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 *
 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 *
 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
 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 }