apc_mmap.c

/*
  +----------------------------------------------------------------------+
  | APC                                                                  |
  +----------------------------------------------------------------------+
  | Copyright (c) 2006-2011 The PHP Group                                |
  +----------------------------------------------------------------------+
  | This source file is subject to version 3.01 of the PHP license,      |
  | that is bundled with this package in the file LICENSE, and is        |
  | available through the world-wide-web at the following url:           |
  | http://www.php.net/license/3_01.txt                                  |
  | If you did not receive a copy of the PHP license and are unable to   |
  | obtain it through the world-wide-web, please send a note to          |
  | license@php.net so we can mail you a copy immediately.               |
  +----------------------------------------------------------------------+
  | Authors: Rasmus Lerdorf <rasmus@php.net>                             |
  +----------------------------------------------------------------------+

   This software was contributed to PHP by Community Connect Inc. in 2002
   and revised in 2005 by Yahoo! Inc. to add support for PHP 5.1.
   Future revisions and derivatives of this source code must acknowledge
   Community Connect Inc. as the original contributor of this module by
   leaving this note intact in the source code.

   All other licensing and usage conditions are those of the PHP Group.

 */

/* $Id: apc_mmap.c 328964 2013-01-03 12:38:55Z remi $ */

#include "apc.h"
#include "apc_mmap.h"
#include "apc_lock.h"

#if APC_MMAP

#include <fcntl.h>
#include <sys/types.h>
#include <sys/mman.h>

/*
 * Some operating systems (like FreeBSD) have a MAP_NOSYNC flag that
 * tells whatever update daemons might be running to not flush dirty
 * vm pages to disk unless absolutely necessary.  My guess is that
 * most systems that don't have this probably default to only synching
 * to disk when absolutely necessary.
 */
#ifndef MAP_NOSYNC
#define MAP_NOSYNC 0
#endif

/* support for systems where MAP_ANONYMOUS is defined but not MAP_ANON, ie: HP-UX bug #14615 */
#if !defined(MAP_ANON) && defined(MAP_ANONYMOUS)
# define MAP_ANON MAP_ANONYMOUS
#endif

apc_segment_t apc_mmap(char *file_mask, size_t size)
{
    apc_segment_t segment; 

    int fd = -1;
    int flags = MAP_SHARED | MAP_NOSYNC;
#ifdef APC_MEMPROTECT
    int remap = 1;
#endif

    /* If no filename was provided, do an anonymous mmap */
    if(!file_mask || (file_mask && !strlen(file_mask))) {
#if !defined(MAP_ANON)
        apc_error("Anonymous mmap does not apear to be available on this system (MAP_ANON/MAP_ANONYMOUS).  Please see the apc.mmap_file_mask INI option.");
#else
        fd = -1;
        flags = MAP_SHARED | MAP_ANON;
#ifdef APC_MEMPROTECT
        remap = 0;
#endif
#endif
    } else if(!strcmp(file_mask,"/dev/zero")) { 
        fd = open("/dev/zero", O_RDWR, S_IRUSR | S_IWUSR);
        if(fd == -1) {
            apc_error("apc_mmap: open on /dev/zero failed:");
            goto error;
        }
#ifdef APC_MEMPROTECT
        remap = 0; /* cannot remap */
#endif
    } else if(strstr(file_mask,".shm")) {
        /*
         * If the filemask contains .shm we try to do a POSIX-compliant shared memory
         * backed mmap which should avoid synchs on some platforms.  At least on
         * FreeBSD this implies MAP_NOSYNC and on Linux it is equivalent of mmap'ing
         * a file in a mounted shmfs.  For this to work on Linux you need to make sure
         * you actually have shmfs mounted.  Also on Linux, make sure the file_mask you
         * pass in has a leading / and no other /'s.  eg.  /apc.shm.XXXXXX
         * On FreeBSD these are mapped onto the regular filesystem so you can put whatever
         * path you want here.
         */
        if(!mktemp(file_mask)) {
            apc_error("apc_mmap: mktemp on %s failed:", file_mask);
            goto error;
        }
        fd = shm_open(file_mask, O_CREAT|O_RDWR, S_IRUSR|S_IWUSR);
        if(fd == -1) {
            apc_error("apc_mmap: shm_open on %s failed:", file_mask);
            goto error;
        }
        if (ftruncate(fd, size) < 0) {
            close(fd);
            shm_unlink(file_mask);
            apc_error("apc_mmap: ftruncate failed:");
            goto error;
        }
        shm_unlink(file_mask);
    } else {
        /*
         * Otherwise we do a normal filesystem mmap
         */
        fd = mkstemp(file_mask);
        if(fd == -1) {
            apc_error("apc_mmap: mkstemp on %s failed:", file_mask);
            goto error;
        }
        if (ftruncate(fd, size) < 0) {
            close(fd);
            unlink(file_mask);
            apc_error("apc_mmap: ftruncate failed:");
            goto error;
        }
        unlink(file_mask);
    }

    segment.shmaddr = (void *)mmap(NULL, size, PROT_READ | PROT_WRITE, flags, fd, 0);
    segment.size = size;

#ifdef APC_MEMPROTECT
    if(remap) {
        segment.roaddr = (void *)mmap(NULL, size, PROT_READ, flags, fd, 0);
    } else {
        segment.roaddr = NULL;
    }
#endif

    if((long)segment.shmaddr == -1) {
        apc_error("apc_mmap: mmap failed:");
    }

    if(fd != -1) close(fd);
    
    return segment;

error:

    segment.shmaddr = (void*)-1;
    segment.size = 0;
#ifdef APC_MEMPROTECT
    segment.roaddr = NULL;
#endif
    return segment;
}

void apc_unmap(apc_segment_t *segment)
{
    if (munmap(segment->shmaddr, segment->size) < 0) {
        apc_warning("apc_unmap: munmap failed:");
    }

#ifdef APC_MEMPROTECT
    if (segment->roaddr && munmap(segment->roaddr, segment->size) < 0) {
        apc_warning("apc_unmap: munmap failed:");
    }
#endif

}

#endif

/*
 * Local variables:
 * tab-width: 4
 * c-basic-offset: 4
 * End:
 * vim>600: expandtab sw=4 ts=4 sts=4 fdm=marker
 * vim<600: expandtab sw=4 ts=4 sts=4
 */