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#include <ipc/services.h>

#include <fibril.h>

#include <as.h>

#define min(a, b)   ((a) < (b) ? (a) : (b))

atomic_t plb_futex = FUTEX_INITIALIZER;

link_t plb_head;    /**< PLB entry ring buffer. */

uint8_t *plb = NULL;

/** Perform a path lookup.

 *

 * @param path      Path to be resolved; it needn't be an ASCIIZ string.

 * @param len       Number of path characters pointed by path.

 * @param result    Empty structure where the lookup result will be stored.

 * @param altroot   If non-empty, will be used instead of rootfs as the root

 *          of the whole VFS tree.

 *

 * @return      EOK on success or an error code from errno.h.

 */

int vfs_lookup_internal(char *path, size_t len, vfs_lookup_res_t *result,

    vfs_pair_t *altroot)

{

    vfs_pair_t *root;

    if (!len)

        return EINVAL;

    if (altroot)

        root = altroot;

    else

        root = (vfs_pair_t *) &rootfs;

    if (!root->fs_handle)

        return ENOENT;

    futex_down(&plb_futex);

    plb_entry_t entry;

    link_initialize(&entry.plb_link);

    entry.len = len;

    off_t first;    /* the first free index */

    off_t last; /* the last free index */

    if (list_empty(&plb_head)) {

        first = 0;

        last = PLB_SIZE - 1;

    } else {

        plb_entry_t *oldest = list_get_instance(plb_head.next,

            plb_entry_t, plb_link);

        plb_entry_t *newest = list_get_instance(plb_head.prev,

            plb_entry_t, plb_link);

        first = (newest->index + newest->len) % PLB_SIZE;

        last = (oldest->index - 1) % PLB_SIZE;

    }

    if (first <= last) {

        if ((last - first) + 1 < len) {

            /*

             * The buffer cannot absorb the path.

             */

            futex_up(&plb_futex);

            return ELIMIT;

        }

    } else {

        if (PLB_SIZE - ((first - last) + 1) < len) {

            /*

             * The buffer cannot absorb the path.

             */

            futex_up(&plb_futex);

            return ELIMIT;

        }

    }

    /*

     * We know the first free index in PLB and we also know that there is

     * enough space in the buffer to hold our path.

     */

    entry.index = first;

    entry.len = len;

    /*

     * Claim PLB space by inserting the entry into the PLB entry ring

     * buffer.

     */

    list_append(&entry.plb_link, &plb_head);

    futex_up(&plb_futex);

    /*

     * Copy the path into PLB.

     */

    size_t cnt1 = min(len, (PLB_SIZE - first) + 1);

    size_t cnt2 = len - cnt1;

    memcpy(&plb[first], path, cnt1);

    memcpy(plb, &path[cnt1], cnt2);

    ipc_call_t answer;

    int phone = vfs_grab_phone(root->fs_handle);

    aid_t req = async_send_3(phone, VFS_LOOKUP, (ipcarg_t) first,

        (ipcarg_t) (first + len - 1) % PLB_SIZE,

        (ipcarg_t) root->dev_handle, &answer);

    vfs_release_phone(phone);

    ipcarg_t rc;

    async_wait_for(req, &rc);

    futex_down(&plb_futex);

    list_remove(&entry.plb_link);

    /*

     * Erasing the path from PLB will come handy for debugging purposes.

     */

    memset(&plb[first], 0, cnt1);

    memset(plb, 0, cnt2);

    futex_up(&plb_futex);

    if (rc == EOK) {

        result->triplet.fs_handle = (int) IPC_GET_ARG1(answer);

        result->triplet.dev_handle = (int) IPC_GET_ARG2(answer);

        result->triplet.index = (int) IPC_GET_ARG3(answer);

        result->size = (size_t) IPC_GET_ARG4(answer);

    }

    return rc;

}

    return rc; 

}

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_OPEN)] != VFS_OP_DEFINED) {

        dprintf("Operation VFS_OPEN not defined by the client.\n");

        return false;

    }

    if (info->ops[IPC_METHOD_TO_VFS_OP(VFS_CLOSE)] != VFS_OP_DEFINED) {

        dprintf("Operation VFS_CLOSE 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);

        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;