shm.c

Apache 2.0.63 is the current stable version of the 2.0 series, and is recommended over any previous

/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "apr_arch_shm.h"

#include "apr_general.h"
#include "apr_errno.h"
#include "apr_user.h"
#include "apr_strings.h"

static apr_status_t shm_cleanup_owner(void *m_)
{
    apr_shm_t *m = (apr_shm_t *)m_;

    /* anonymous shared memory */
    if (m->filename == NULL) {
#if APR_USE_SHMEM_MMAP_ZERO || APR_USE_SHMEM_MMAP_ANON
        if (munmap(m->base, m->realsize) == -1) {
            return errno;
        }
        return APR_SUCCESS;
#endif
#if APR_USE_SHMEM_SHMGET_ANON
        if (shmdt(m->base) == -1) {
            return errno;
        }
        /* This segment will automatically remove itself after all
         * references have detached. */
        return APR_SUCCESS;
#endif
    }

    /* name-based shared memory */
    else {
#if APR_USE_SHMEM_MMAP_TMP
        apr_status_t rv;

        if (munmap(m->base, m->realsize) == -1) {
            return errno;
        }
        rv = apr_file_remove(m->filename, m->pool);
        if (rv != APR_SUCCESS) {
            return rv;
        }
        return APR_SUCCESS;
#endif
#if APR_USE_SHMEM_MMAP_SHM
        if (munmap(m->base, m->realsize) == -1) {
            return errno;
        }
        if (shm_unlink(m->filename) == -1) {
            return errno;
        }
        return APR_SUCCESS;
#endif
#if APR_USE_SHMEM_SHMGET
        apr_status_t rv;

        /* Indicate that the segment is to be destroyed as soon
         * as all processes have detached. This also disallows any
         * new attachments to the segment. */
        if (shmctl(m->shmid, IPC_RMID, NULL) == -1) {
            return errno;
        }
        if (shmdt(m->base) == -1) {
            return errno;
        }
        rv = apr_file_remove(m->filename, m->pool);
        if (rv != APR_SUCCESS) {
            return rv;
        }
        return APR_SUCCESS;
#endif
    }

    return APR_ENOTIMPL;
}

APR_DECLARE(apr_status_t) apr_shm_create(apr_shm_t **m,
                                         apr_size_t reqsize, 
                                         const char *filename,
                                         apr_pool_t *pool)
{
    apr_shm_t *new_m;
    apr_status_t status;
#if APR_USE_SHMEM_SHMGET || APR_USE_SHMEM_SHMGET_ANON
    struct shmid_ds shmbuf;
    apr_uid_t uid;
    apr_gid_t gid;
#endif
#if APR_USE_SHMEM_MMAP_TMP || APR_USE_SHMEM_MMAP_SHM || \
    APR_USE_SHMEM_MMAP_ZERO
    int tmpfd;
#endif
#if APR_USE_SHMEM_SHMGET
    apr_size_t nbytes;
    key_t shmkey;
#endif
#if APR_USE_SHMEM_MMAP_ZERO || APR_USE_SHMEM_SHMGET || \
    APR_USE_SHMEM_MMAP_TMP || APR_USE_SHMEM_MMAP_SHM
    apr_file_t *file;   /* file where metadata is stored */
#endif

    /* Check if they want anonymous or name-based shared memory */
    if (filename == NULL) {
#if APR_USE_SHMEM_MMAP_ZERO || APR_USE_SHMEM_MMAP_ANON
        new_m = apr_palloc(pool, sizeof(apr_shm_t));
        if (!new_m) {
            return APR_ENOMEM;
        }
        new_m->pool = pool;
        new_m->reqsize = reqsize;
        new_m->realsize = reqsize + 
            APR_ALIGN_DEFAULT(sizeof(apr_size_t)); /* room for metadata */
        new_m->filename = NULL;
    
#if APR_USE_SHMEM_MMAP_ZERO
        status = apr_file_open(&file, "/dev/zero", APR_READ | APR_WRITE, 
                               APR_OS_DEFAULT, pool);
        if (status != APR_SUCCESS) {
            return status;
        }
        status = apr_os_file_get(&tmpfd, file);
        if (status != APR_SUCCESS) {
            return status;
        }

        new_m->base = mmap(NULL, new_m->realsize, PROT_READ|PROT_WRITE,
                           MAP_SHARED, tmpfd, 0);
        if (new_m->base == (void *)MAP_FAILED) {
            return errno;
        }

        status = apr_file_close(file);
        if (status != APR_SUCCESS) {
            return status;
        }

        /* store the real size in the metadata */
        *(apr_size_t*)(new_m->base) = new_m->realsize;
        /* metadata isn't usable */
        new_m->usable = (char *)new_m->base + APR_ALIGN_DEFAULT(sizeof(apr_size_t));

        apr_pool_cleanup_register(new_m->pool, new_m, shm_cleanup_owner,
                                  apr_pool_cleanup_null);
        *m = new_m;
        return APR_SUCCESS;

#elif APR_USE_SHMEM_MMAP_ANON
        new_m->base = mmap(NULL, new_m->realsize, PROT_READ|PROT_WRITE,
                           MAP_ANON|MAP_SHARED, -1, 0);
        if (new_m->base == (void *)MAP_FAILED) {
            return errno;
        }

        /* store the real size in the metadata */
        *(apr_size_t*)(new_m->base) = new_m->realsize;
        /* metadata isn't usable */
        new_m->usable = (char *)new_m->base + APR_ALIGN_DEFAULT(sizeof(apr_size_t));

        apr_pool_cleanup_register(new_m->pool, new_m, shm_cleanup_owner,
                                  apr_pool_cleanup_null);
        *m = new_m;
        return APR_SUCCESS;

#endif /* APR_USE_SHMEM_MMAP_ZERO */
#endif /* APR_USE_SHMEM_MMAP_ZERO || APR_USE_SHMEM_MMAP_ANON */
#if APR_USE_SHMEM_SHMGET_ANON

        new_m = apr_palloc(pool, sizeof(apr_shm_t));
        if (!new_m) {
            return APR_ENOMEM;
        }
        new_m->pool = pool;
        new_m->reqsize = reqsize;
        new_m->realsize = reqsize;
        new_m->filename = NULL;

        if ((new_m->shmid = shmget(IPC_PRIVATE, new_m->realsize,
                                   SHM_R | SHM_W | IPC_CREAT)) < 0) {
            return errno;
        }

        if ((new_m->base = shmat(new_m->shmid, NULL, 0)) == (void *)-1) {
            return errno;
        }
        new_m->usable = new_m->base;

        if (shmctl(new_m->shmid, IPC_STAT, &shmbuf) == -1) {
            return errno;
        }
        apr_uid_current(&uid, &gid, pool);
        shmbuf.shm_perm.uid = uid;
        shmbuf.shm_perm.gid = gid;
        if (shmctl(new_m->shmid, IPC_SET, &shmbuf) == -1) {
            return errno;
        }

        /* Remove the segment once use count hits zero.
         * We will not attach to this segment again, since it is
         * anonymous memory, so it is ok to mark it for deletion.
         */
        if (shmctl(new_m->shmid, IPC_RMID, NULL) == -1) {
            return errno;
        }

        apr_pool_cleanup_register(new_m->pool, new_m, shm_cleanup_owner,
                                  apr_pool_cleanup_null);
        *m = new_m;
        return APR_SUCCESS;
#endif /* APR_USE_SHMEM_SHMGET_ANON */
        /* It is an error if they want anonymous memory but we don't have it. */
        return APR_ENOTIMPL; /* requested anonymous but we don't have it */
    }

    /* Name-based shared memory */
    else {
        new_m = apr_palloc(pool, sizeof(apr_shm_t));
        if (!new_m) {
            return APR_ENOMEM;
        }
        new_m->pool = pool;
        new_m->reqsize = reqsize;
        new_m->filename = apr_pstrdup(pool, filename);

#if APR_USE_SHMEM_MMAP_TMP || APR_USE_SHMEM_MMAP_SHM
        new_m->realsize = reqsize + 
            APR_ALIGN_DEFAULT(sizeof(apr_size_t)); /* room for metadata */
        /* FIXME: Ignore error for now. *
         * status = apr_file_remove(file, pool);*/
        status = APR_SUCCESS;
    
#if APR_USE_SHMEM_MMAP_TMP
        /* FIXME: Is APR_OS_DEFAULT sufficient? */
        status = apr_file_open(&file, filename, 
                               APR_READ | APR_WRITE | APR_CREATE | APR_EXCL,
                               APR_OS_DEFAULT, pool);
        if (status != APR_SUCCESS) {
            return status;
        }

        status = apr_os_file_get(&tmpfd, file);
        if (status != APR_SUCCESS) {
            apr_file_close(file); /* ignore errors, we're failing */
            apr_file_remove(new_m->filename, new_m->pool);
            return status;
        }

        status = apr_file_trunc(file, new_m->realsize);
        if (status != APR_SUCCESS) {
            apr_file_close(file); /* ignore errors, we're failing */
            apr_file_remove(new_m->filename, new_m->pool);
            return status;
        }

        new_m->base = mmap(NULL, new_m->realsize, PROT_READ | PROT_WRITE,
                           MAP_SHARED, tmpfd, 0);
        /* FIXME: check for errors */

        status = apr_file_close(file);
        if (status != APR_SUCCESS) {
            return status;
        }
#endif /* APR_USE_SHMEM_MMAP_TMP */
#if APR_USE_SHMEM_MMAP_SHM
        /* FIXME: Is APR_OS_DEFAULT sufficient? */
        tmpfd = shm_open(filename, O_RDWR | O_CREAT | O_EXCL, APR_OS_DEFAULT);
        if (tmpfd == -1) {
            return errno;
        }

        status = apr_os_file_put(&file, &tmpfd,