vfs_register.c

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/*
 * Copyright (c) 2008 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <ipc/services.h>
#include <async.h>
#include <fibril.h>
#include <fibril_synch.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <str.h>
#include <ctype.h>
#include <bool.h>
#include <adt/list.h>
#include <as.h>
#include <assert.h>
#include <atomic.h>
#include "vfs.h"

FIBRIL_CONDVAR_INITIALIZE(fs_head_cv);
FIBRIL_MUTEX_INITIALIZE(fs_head_lock);
LIST_INITIALIZE(fs_head);

atomic_t fs_handle_next = {
        .count = 1
};

static bool vfs_info_sane(vfs_info_t *info)
{
        int i;

        /*
         * Check if the name is non-empty and is composed solely of ASCII
         * characters [a-z]+[a-z0-9_-]*.
         */
        if (!islower(info->name[0])) {
                dprintf("The name doesn't start with a lowercase character.\n");
                return false;
        }
        for (i = 1; i < FS_NAME_MAXLEN; i++) {
                if (!(islower(info->name[i]) || isdigit(info->name[i])) &&
                    (info->name[i] != '-') && (info->name[i] != '_')) {
                        if (info->name[i] == '\0') {
                                break;
                        } else {
                                dprintf("The name contains illegal "
                                    "characters.\n");
                                return false;
                        }
                }
        }
        /*
         * This check is not redundant. It ensures that the name is
         * NULL-terminated, even if FS_NAME_MAXLEN characters are used.
         */
        if (info->name[i] != '\0') {
                dprintf("The name is not properly NULL-terminated.\n"); 
                return false;
        }
        
        return true;
}

void vfs_register(ipc_callid_t rid, ipc_call_t *request)
{
        int phone;
        
        dprintf("Processing VFS_REGISTER request received from %p.\n",
            request->in_phone_hash);
        
        vfs_info_t *vfs_info;
        int rc = async_data_write_accept((void **) &vfs_info, false,
            sizeof(vfs_info_t), sizeof(vfs_info_t), 0, NULL);
        
        if (rc != EOK) {
                dprintf("Failed to deliver the VFS info into our AS, rc=%d.\n",
                    rc);
                async_answer_0(rid, rc);
                return;
        }
        
        /*
         * Allocate and initialize a buffer for the fs_info structure.
         */
        fs_info_t *fs_info = (fs_info_t *) malloc(sizeof(fs_info_t));
        if (!fs_info) {
                dprintf("Could not allocate memory for FS info.\n");
                async_answer_0(rid, ENOMEM);
                return;
        }
        
        link_initialize(&fs_info->fs_link);
        fs_info->vfs_info = *vfs_info;
        free(vfs_info);
        
        dprintf("VFS info delivered.\n");
        
        if (!vfs_info_sane(&fs_info->vfs_info)) {
                free(fs_info);
                async_answer_0(rid, EINVAL);
                return;
        }
        
        fibril_mutex_lock(&fs_head_lock);
        
        /*
         * Check for duplicit registrations.
         */
        if (fs_name_to_handle(fs_info->vfs_info.name, false)) {
                /*
                 * We already register a fs like this.
                 */
                dprintf("FS is already registered.\n");
                fibril_mutex_unlock(&fs_head_lock);
                free(fs_info);
                async_answer_0(rid, EEXISTS);
                return;
        }
        
        /*
         * Add fs_info to the list of registered FS's.
         */
        dprintf("Inserting FS into the list of registered file systems.\n");
        list_append(&fs_info->fs_link, &fs_head);
        
        /*
         * Now we want the client to send us the IPC_M_CONNECT_TO_ME call so
         * that a callback connection is created and we have a phone through
         * which to forward VFS requests to it.
         */
        ipc_call_t call;
        ipc_callid_t callid = async_get_call(&call);
        if (IPC_GET_IMETHOD(call) != IPC_M_CONNECT_TO_ME) {
                dprintf("Unexpected call, method = %d\n", IPC_GET_IMETHOD(call));
                list_remove(&fs_info->fs_link);
                fibril_mutex_unlock(&fs_head_lock);
                free(fs_info);
                async_answer_0(callid, EINVAL);
                async_answer_0(rid, EINVAL);
                return;
        }
        
        phone = IPC_GET_ARG5(call);
        async_session_create(&fs_info->session, phone, 0);
        async_answer_0(callid, EOK);
        
        dprintf("Callback connection to FS created.\n");
        
        /*
         * The client will want us to send him the address space area with PLB.
         */
        
        size_t size;
        if (!async_share_in_receive(&callid, &size)) {
                dprintf("Unexpected call, method = %d\n", IPC_GET_IMETHOD(call));
                list_remove(&fs_info->fs_link);
                fibril_mutex_unlock(&fs_head_lock);
                async_session_destroy(&fs_info->session);
                async_hangup(phone);
                free(fs_info);
                async_answer_0(callid, EINVAL);
                async_answer_0(rid, EINVAL);
                return;
        }
        
        /*
         * We can only send the client address space area PLB_SIZE bytes long.
         */
        if (size != PLB_SIZE) {
                dprintf("Client suggests wrong size of PFB, size = %d\n", size);
                list_remove(&fs_info->fs_link);
                fibril_mutex_unlock(&fs_head_lock);
                async_session_destroy(&fs_info->session);
                async_hangup(phone);
                free(fs_info);
                async_answer_0(callid, EINVAL);
                async_answer_0(rid, EINVAL);
                return;
        }
        
        /*
         * Commit to read-only sharing the PLB with the client.
         */
        (void) async_share_in_finalize(callid, plb,
            AS_AREA_READ | AS_AREA_CACHEABLE);
        
        dprintf("Sharing PLB.\n");
        
        /*
         * That was it. The FS has been registered.
         * In reply to the VFS_REGISTER request, we assign the client file
         * system a global file system handle.
         */
        fs_info->fs_handle = (fs_handle_t) atomic_postinc(&fs_handle_next);
        async_answer_1(rid, EOK, (sysarg_t) fs_info->fs_handle);
        
        fibril_condvar_broadcast(&fs_head_cv);
        fibril_mutex_unlock(&fs_head_lock);
        
        dprintf("\"%.*s\" filesystem successfully registered, handle=%d.\n",
            FS_NAME_MAXLEN, fs_info->vfs_info.name, fs_info->fs_handle);
}

int vfs_grab_phone(fs_handle_t handle)
{
        link_t *cur;
        fs_info_t *fs;
        int phone;

        /*
         * For now, we don't try to be very clever and very fast.  We simply
         * lookup the phone in the fs_head list and duplicate it.  The duplicate
         * phone will be returned to the client and the client will use it for
         * communication.  In the future, we should cache the connections so
         * that they do not have to be reestablished over and over again.
         */
        fibril_mutex_lock(&fs_head_lock);
        for (cur = fs_head.next; cur != &fs_head; cur = cur->next) {
                fs = list_get_instance(cur, fs_info_t, fs_link);
                if (fs->fs_handle == handle) {
                        fibril_mutex_unlock(&fs_head_lock);
                        phone = async_exchange_begin(&fs->session);

                        assert(phone > 0);
                        return phone;
                }
        }
        fibril_mutex_unlock(&fs_head_lock);
        return 0;
}

void vfs_release_phone(fs_handle_t handle, int phone)
{
        link_t *cur;
        fs_info_t *fs;

        fibril_mutex_lock(&fs_head_lock);
        for (cur = fs_head.next; cur != &fs_head; cur = cur->next) {
                fs = list_get_instance(cur, fs_info_t, fs_link);
                if (fs->fs_handle == handle) {
                        fibril_mutex_unlock(&fs_head_lock);
                        async_exchange_end(&fs->session, phone);
                        return;
                }
        }
        /* should not really get here */
        abort();
        fibril_mutex_unlock(&fs_head_lock);
}

fs_handle_t fs_name_to_handle(char *name, bool lock)
{
        int handle = 0;
        
        if (lock)
                fibril_mutex_lock(&fs_head_lock);
        link_t *cur;
        for (cur = fs_head.next; cur != &fs_head; cur = cur->next) {
                fs_info_t *fs = list_get_instance(cur, fs_info_t, fs_link);
                if (str_cmp(fs->vfs_info.name, name) == 0) { 
                        handle = fs->fs_handle;
                        break;
                }
        }
        if (lock)
                fibril_mutex_unlock(&fs_head_lock);
        return handle;
}

vfs_info_t *fs_handle_to_info(fs_handle_t handle)
{
        vfs_info_t *info = NULL;
        link_t *cur;

        fibril_mutex_lock(&fs_head_lock);
        for (cur = fs_head.next; cur != &fs_head; cur = cur->next) {
                fs_info_t *fs = list_get_instance(cur, fs_info_t, fs_link);
                if (fs->fs_handle == handle) { 
                        info = &fs->vfs_info;
                        break;
                }
        }
        fibril_mutex_unlock(&fs_head_lock);

        return info;
}

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