source: mainline/uspace/srv/vfs/vfs_register.c@ f17667a

/*
 * 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.
 */

/** @addtogroup fs
 * @{
 */ 

/**
 * @file        vfs_register.c
 * @brief
 */

#include <ipc/ipc.h>
#include <ipc/services.h>
#include <async.h>
#include <fibril.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <bool.h>
#include <futex.h>
#include <libadt/list.h>
#include <as.h>
#include <assert.h>
#include <atomic.h>
#include "vfs.h"

atomic_t fs_head_futex = FUTEX_INITIALIZER;
link_t fs_head;

atomic_t fs_handle_next = {
        .count = 1
};

/** Verify the VFS info structure.
 *
 * @param info          Info structure to be verified.
 *
 * @return              Non-zero if the info structure is sane, zero otherwise.
 */
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;
        }
        

        /*
         * Check if the FS implements mandatory VFS operations.
         */
        if (info->ops[IPC_METHOD_TO_VFS_OP(VFS_LOOKUP)] != VFS_OP_DEFINED) {
                dprintf("Operation VFS_LOOKUP not defined by the client.\n");
                return false;
        }
        if (info->ops[IPC_METHOD_TO_VFS_OP(VFS_READ)] != VFS_OP_DEFINED) {
                dprintf("Operation VFS_READ not defined by the client.\n");
                return false;
        }
        
        /*
         * Check if each operation is either not defined, defined or default.
         */
        for (i = VFS_FIRST; i < VFS_LAST_CLNT; i++) {
                if ((info->ops[IPC_METHOD_TO_VFS_OP(i)] != VFS_OP_NULL) && 
                    (info->ops[IPC_METHOD_TO_VFS_OP(i)] != VFS_OP_DEFAULT) && 
                    (info->ops[IPC_METHOD_TO_VFS_OP(i)] != VFS_OP_DEFINED)) {
                        dprintf("Operation info not understood.\n");
                        return false;
                }
        }
        return true;
}

/** VFS_REGISTER protocol function.
 *
 * @param rid           Hash of the call with the request.
 * @param request       Call structure with the request.
 */
void vfs_register(ipc_callid_t rid, ipc_call_t *request)
{
        ipc_callid_t callid;
        ipc_call_t call;
        int rc;
        size_t size;

        dprintf("Processing VFS_REGISTER request received from %p.\n",
            request->in_phone_hash);

        /*
         * The first call has to be IPC_M_DATA_SEND in which we receive the
         * VFS info structure from the client FS.
         */
        if (!ipc_data_write_receive(&callid, &size)) {
                /*
                 * The client doesn't obey the same protocol as we do.
                 */
                dprintf("Receiving of VFS info failed.\n");
                ipc_answer_0(callid, EINVAL);
                ipc_answer_0(rid, EINVAL);
                return;
        }
        
        dprintf("VFS info received, size = %d\n", size);
        
        /*
         * We know the size of the VFS info structure. See if the client
         * understands this easy concept too.
         */
        if (size != sizeof(vfs_info_t)) {
                /*
                 * The client is sending us something, which cannot be
                 * the info structure.
                 */
                dprintf("Received VFS info has bad size.\n");
                ipc_answer_0(callid, EINVAL);
                ipc_answer_0(rid, EINVAL);
                return;
        }

        /*
         * Allocate and initialize a buffer for the fs_info structure.
         */
        fs_info_t *fs_info;
        fs_info = (fs_info_t *) malloc(sizeof(fs_info_t));
        if (!fs_info) {
                dprintf("Could not allocate memory for FS info.\n");
                ipc_answer_0(callid, ENOMEM);
                ipc_answer_0(rid, ENOMEM);
                return;
        }
        link_initialize(&fs_info->fs_link);
        futex_initialize(&fs_info->phone_futex, 1);
                
        rc = ipc_data_write_finalize(callid, &fs_info->vfs_info, size);
        if (rc != EOK) {
                dprintf("Failed to deliver the VFS info into our AS, rc=%d.\n",
                    rc);
                free(fs_info);
                ipc_answer_0(callid, rc);
                ipc_answer_0(rid, rc);
                return;
        }

        dprintf("VFS info delivered.\n");
                
        if (!vfs_info_sane(&fs_info->vfs_info)) {
                free(fs_info);
                ipc_answer_0(callid, EINVAL);
                ipc_answer_0(rid, EINVAL);
                return;
        }
                
        futex_down(&fs_head_futex);

        /*
         * 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");
                futex_up(&fs_head_futex);
                free(fs_info);
                ipc_answer_0(callid, EEXISTS);
                ipc_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.
         */
        callid = async_get_call(&call);
        if (IPC_GET_METHOD(call) != IPC_M_CONNECT_TO_ME) {
                dprintf("Unexpected call, method = %d\n", IPC_GET_METHOD(call));
                list_remove(&fs_info->fs_link);
                futex_up(&fs_head_futex);
                free(fs_info);
                ipc_answer_0(callid, EINVAL);
                ipc_answer_0(rid, EINVAL);
                return;
        }
        fs_info->phone = IPC_GET_ARG5(call);
        ipc_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.
         */

        if (!ipc_share_in_receive(&callid, &size)) {
                dprintf("Unexpected call, method = %d\n", IPC_GET_METHOD(call));
                list_remove(&fs_info->fs_link);
                futex_up(&fs_head_futex);
                ipc_hangup(fs_info->phone);
                free(fs_info);
                ipc_answer_0(callid, EINVAL);
                ipc_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);
                futex_up(&fs_head_futex);
                ipc_hangup(fs_info->phone);
                free(fs_info);
                ipc_answer_0(callid, EINVAL);
                ipc_answer_0(rid, EINVAL);
                return;
        }

        /*
         * Commit to read-only sharing the PLB with the client.
         */
        (void) ipc_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 = (int) atomic_postinc(&fs_handle_next);
        ipc_answer_1(rid, EOK, (ipcarg_t) fs_info->fs_handle);
        
        futex_up(&fs_head_futex);
        
        dprintf("\"%.*s\" filesystem successfully registered, handle=%d.\n",
            FS_NAME_MAXLEN, fs_info->vfs_info.name, fs_info->fs_handle);
}

/** For a given file system handle, implement policy for allocating a phone.
 *
 * @param handle        File system handle.
 *
 * @return              Phone over which a multi-call request can be safely
 *                      sent. Return 0 if no phone was found.
 */
int vfs_grab_phone(int handle)
{
        /*
         * For now, we don't try to be very clever and very fast.
         * We simply lookup the phone in the fs_head list. We currently don't
         * open any additional phones (even though that itself would be pretty
         * straightforward; housekeeping multiple open phones to a FS task would
         * be more demanding). Instead, we simply take the respective
         * phone_futex and keep it until vfs_release_phone().
         */
        futex_down(&fs_head_futex);
        link_t *cur;
        fs_info_t *fs;
        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) {
                        futex_up(&fs_head_futex);
                        /*
                         * For now, take the futex unconditionally.
                         * Oh yeah, serialization rocks.
                         * It will be up'ed in vfs_release_phone().
                         */
                        futex_down(&fs->phone_futex);
                        /*
                         * Avoid deadlock with other fibrils in the same thread
                         * by disabling fibril preemption.
                         */
                        fibril_inc_sercount();
                        return fs->phone; 
                }
        }
        futex_up(&fs_head_futex);
        return 0;
}

/** Tell VFS that the phone is in use for any request.
 *
 * @param phone         Phone to FS task.
 */
void vfs_release_phone(int phone)
{
        bool found = false;

        /*
         * Undo the fibril_inc_sercount() done in vfs_grab_phone().
         */
        fibril_dec_sercount();
        
        futex_down(&fs_head_futex);
        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 (fs->phone == phone) {
                        found = true;
                        futex_up(&fs_head_futex);
                        futex_up(&fs->phone_futex);
                        return;
                }
        }
        futex_up(&fs_head_futex);

        /*
         * Not good to get here.
         */
        assert(found == true);
}

/** Convert file system name to its handle.
 *
 * @param name          File system name.
 * @param lock          If true, the function will down and up the
 *                      fs_head_futex.
 *
 * @return              File system handle or zero if file system not found.
 */
int fs_name_to_handle(char *name, bool lock)
{
        int handle = 0;
        
        if (lock)
                futex_down(&fs_head_futex);
        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 (strncmp(fs->vfs_info.name, name,
                    sizeof(fs->vfs_info.name)) == 0) { 
                        handle = fs->fs_handle;
                        break;
                }
        }
        if (lock)
                futex_up(&fs_head_futex);
        return handle;
}

/**
 * @}
 */