shared_alloc_shm.c

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/*
   +----------------------------------------------------------------------+
   | Zend OPcache                                                         |
   +----------------------------------------------------------------------+
   | Copyright (c) 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:           |
   | https://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: Andi Gutmans <andi@php.net>                                 |
   |          Zeev Suraski <zeev@php.net>                                 |
   |          Stanislav Malyshev <stas@zend.com>                          |
   |          Dmitry Stogov <dmitry@php.net>                              |
   +----------------------------------------------------------------------+
*/
 
#include "zend_shared_alloc.h"
 
#ifdef USE_SHM
 
#if defined(__FreeBSD__)
# include <machine/param.h>
#endif
#include <sys/types.h>
#include <sys/shm.h>
#include <sys/ipc.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
 
#include <sys/stat.h>
#include <fcntl.h>
 
#ifndef MIN
# define MIN(x, y) ((x) > (y)? (y) : (x))
#endif
 
#define SEG_ALLOC_SIZE_MAX 32*1024*1024
#define SEG_ALLOC_SIZE_MIN 2*1024*1024
 
typedef struct  {
    zend_shared_segment common;
    int shm_id;
} zend_shared_segment_shm;
 
static int create_segments(size_t requested_size, zend_shared_segment_shm ***shared_segments_p, int *shared_segments_count, const char **error_in)
{
    int i;
    size_t allocate_size = 0, remaining_bytes = requested_size, seg_allocate_size;
    int first_segment_id = -1;
    key_t first_segment_key = -1;
    struct shmid_ds sds;
    int shmget_flags;
    zend_shared_segment_shm *shared_segments;
 
    seg_allocate_size = SEG_ALLOC_SIZE_MAX;
    /* determine segment size we _really_ need:
     * no more than to include requested_size
     */
    while (requested_size * 2 <= seg_allocate_size && seg_allocate_size > SEG_ALLOC_SIZE_MIN) {
        seg_allocate_size >>= 1;
    }
 
    shmget_flags = IPC_CREAT|SHM_R|SHM_W|IPC_EXCL;
 
    /* try allocating this much, if not - try shrinking */
    while (seg_allocate_size >= SEG_ALLOC_SIZE_MIN) {
        allocate_size = MIN(requested_size, seg_allocate_size);
        first_segment_id = shmget(first_segment_key, allocate_size, shmget_flags);
        if (first_segment_id != -1) {
            break;
        }
        seg_allocate_size >>= 1; /* shrink the allocated block */
    }
 
    if (first_segment_id == -1) {
        *error_in = "shmget";
        return ALLOC_FAILURE;
    }
 
    *shared_segments_count = ((requested_size - 1) / seg_allocate_size) + 1;
    *shared_segments_p = (zend_shared_segment_shm **) calloc(1, (*shared_segments_count) * sizeof(zend_shared_segment_shm) + sizeof(void *) * (*shared_segments_count));
    if (!*shared_segments_p) {
        *error_in = "calloc";
        return ALLOC_FAILURE;
    }
    shared_segments = (zend_shared_segment_shm *)((char *)(*shared_segments_p) + sizeof(void *) * (*shared_segments_count));
    for (i = 0; i < *shared_segments_count; i++) {
        (*shared_segments_p)[i] = shared_segments + i;
    }
 
    remaining_bytes = requested_size;
    for (i = 0; i < *shared_segments_count; i++) {
        allocate_size = MIN(remaining_bytes, seg_allocate_size);
        if (i != 0) {
            shared_segments[i].shm_id = shmget(IPC_PRIVATE, allocate_size, shmget_flags);
        } else {
            shared_segments[i].shm_id = first_segment_id;
        }
 
        if (shared_segments[i].shm_id == -1) {
            return ALLOC_FAILURE;
        }
 
        shared_segments[i].common.p = shmat(shared_segments[i].shm_id, NULL, 0);
        if (shared_segments[i].common.p == (void *)-1) {
            *error_in = "shmat";
            shmctl(shared_segments[i].shm_id, IPC_RMID, &sds);
            return ALLOC_FAILURE;
        }
        shmctl(shared_segments[i].shm_id, IPC_RMID, &sds);
 
        shared_segments[i].common.pos = 0;
        shared_segments[i].common.size = allocate_size;
        remaining_bytes -= allocate_size;
    }
    return ALLOC_SUCCESS;
}
 
static int detach_segment(zend_shared_segment_shm *shared_segment)
{
    shmdt(shared_segment->common.p);
    return 0;
}
 
static size_t segment_type_size(void)
{
    return sizeof(zend_shared_segment_shm);
}
 
const zend_shared_memory_handlers zend_alloc_shm_handlers = {
    (create_segments_t)create_segments,
    (detach_segment_t)detach_segment,
    segment_type_size
};
 
#endif /* USE_SHM */