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/* Memory allocation aligned to system page boundaries.
Copyright (C) 2005-2007, 2009-2021 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Derek R. Price <derek@ximbiot.com>. */
#include <config.h>
#include "pagealign_alloc.h"
#include <errno.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#if HAVE_MMAP
# include <sys/mman.h>
#endif
#include "error.h"
#include "xalloc.h"
#include "gettext.h"
#define _(str) gettext (str)
#if HAVE_MMAP
/* Define MAP_FILE when it isn't otherwise. */
# ifndef MAP_FILE
# define MAP_FILE 0
# endif
/* Define MAP_FAILED for old systems which neglect to. */
# ifndef MAP_FAILED
# define MAP_FAILED ((void *)-1)
# endif
#endif
#if HAVE_MMAP || ! HAVE_POSIX_MEMALIGN
# if HAVE_MMAP
/* For each memory region, we store its size. */
typedef size_t info_t;
# else
/* For each memory region, we store the original pointer returned by
malloc(). */
typedef void * info_t;
# endif
/* A simple linked list of allocated memory regions. It is probably not the
most efficient way to store these, but anyway... */
typedef struct memnode_s memnode_t;
struct memnode_s
{
void *aligned_ptr;
info_t info;
memnode_t *next;
};
/* The list of currently allocated memory regions. */
static memnode_t *memnode_table = NULL;
static void
new_memnode (void *aligned_ptr, info_t info)
{
memnode_t *new_node = XMALLOC (memnode_t);
new_node->aligned_ptr = aligned_ptr;
new_node->info = info;
new_node->next = memnode_table;
memnode_table = new_node;
}
/* Dispose of the memnode containing a map for the ALIGNED_PTR in question
and return the content of the node's INFO field. */
static info_t
get_memnode (void *aligned_ptr)
{
info_t ret;
memnode_t *c;
memnode_t **p_next = &memnode_table;
for (c = *p_next; c != NULL; p_next = &c->next, c = c->next)
if (c->aligned_ptr == aligned_ptr)
break;
if (c == NULL)
/* An attempt to free untracked memory. A wrong pointer was passed
to pagealign_free(). */
abort ();
/* Remove this entry from the list, save the return value, and free it. */
*p_next = c->next;
ret = c->info;
free (c);
return ret;
}
#endif /* HAVE_MMAP || !HAVE_POSIX_MEMALIGN */
void *
pagealign_alloc (size_t size)
{
void *ret;
/* We prefer the mmap() approach over the posix_memalign() or malloc()
based approaches, since the latter often waste an entire memory page
per call. */
#if HAVE_MMAP
# ifdef HAVE_MAP_ANONYMOUS
const int fd = -1;
const int flags = MAP_ANONYMOUS | MAP_PRIVATE;
# else /* !HAVE_MAP_ANONYMOUS */
static int fd = -1; /* Only open /dev/zero once in order to avoid limiting
the amount of memory we may allocate based on the
number of open file descriptors. */
const int flags = MAP_FILE | MAP_PRIVATE;
if (fd == -1)
{
fd = open ("/dev/zero", O_RDONLY | O_CLOEXEC, 0666);
if (fd < 0)
error (EXIT_FAILURE, errno, _("Failed to open /dev/zero for read"));
}
# endif /* HAVE_MAP_ANONYMOUS */
ret = mmap (NULL, size, PROT_READ | PROT_WRITE, flags, fd, 0);
if (ret == MAP_FAILED)
return NULL;
new_memnode (ret, size);
#elif HAVE_POSIX_MEMALIGN
int status = posix_memalign (&ret, getpagesize (), size);
if (status)
{
errno = status;
return NULL;
}
#else /* !HAVE_MMAP && !HAVE_POSIX_MEMALIGN */
size_t pagesize = getpagesize ();
void *unaligned_ptr = malloc (size + pagesize - 1);
if (unaligned_ptr == NULL)
{
/* Set errno. We don't know whether malloc already set errno: some
implementations of malloc do, some don't. */
errno = ENOMEM;
return NULL;
}
ret = (char *) unaligned_ptr
+ ((- (unsigned long) unaligned_ptr) & (pagesize - 1));
new_memnode (ret, unaligned_ptr);
#endif /* HAVE_MMAP && HAVE_POSIX_MEMALIGN */
return ret;
}
void *
pagealign_xalloc (size_t size)
{
void *ret;
ret = pagealign_alloc (size);
if (ret == NULL)
xalloc_die ();
return ret;
}
void
pagealign_free (void *aligned_ptr)
{
#if HAVE_MMAP
if (munmap (aligned_ptr, get_memnode (aligned_ptr)) < 0)
error (EXIT_FAILURE, errno, "Failed to unmap memory");
#elif HAVE_POSIX_MEMALIGN
free (aligned_ptr);
#else
free (get_memnode (aligned_ptr));
#endif
}
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