source: mainline/kernel/generic/src/ipc/sysipc.c

/*
 * Copyright (c) 2006 Ondrej Palkovsky
 * 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 kernel_generic_ipc
 * @{
 */
/** @file
 */

#include <arch.h>
#include <assert.h>
#include <errno.h>
#include <memw.h>
#include <ipc/ipc.h>
#include <abi/ipc/methods.h>
#include <ipc/sysipc.h>
#include <ipc/sysipc_ops.h>
#include <ipc/sysipc_priv.h>
#include <ipc/irq.h>
#include <ipc/ipcrsc.h>
#include <ipc/event.h>
#include <ipc/kbox.h>
#include <synch/waitq.h>
#include <arch/interrupt.h>
#include <syscall/copy.h>
#include <security/perm.h>
#include <console/console.h>
#include <macros.h>
#include <cap/cap.h>

#define STRUCT_TO_USPACE(dst, src)  copy_to_uspace((dst), (src), sizeof(*(src)))

/** Decide if the interface and method is a system method.
 *
 * @param imethod Interface and method to be decided.
 *
 * @return True if the interface and method is a system
 *         interface and method.
 *
 */
static inline bool method_is_system(sysarg_t imethod)
{
        if (imethod <= IPC_M_LAST_SYSTEM)
                return true;

        return false;
}

/** Decide if the message with this interface and method is forwardable.
 *
 * Some system messages may be forwarded, for some of them
 * it is useless.
 *
 * @param imethod Interface and method to be decided.
 *
 * @return True if the interface and method is forwardable.
 *
 */
static inline bool method_is_forwardable(sysarg_t imethod)
{
        switch (imethod) {
        case IPC_M_PHONE_HUNGUP:
                /* This message is meant only for the original recipient. */
                return false;
        default:
                return true;
        }
}

/** Decide if the message with this interface and method is immutable on forward.
 *
 * Some system messages may be forwarded but their content cannot be altered.
 *
 * @param imethod Interface and method to be decided.
 *
 * @return True if the interface and method is immutable on forward.
 *
 */
static inline bool method_is_immutable(sysarg_t imethod)
{
        switch (imethod) {
        case IPC_M_PAGE_IN:
        case IPC_M_SHARE_OUT:
        case IPC_M_SHARE_IN:
        case IPC_M_DATA_WRITE:
        case IPC_M_DATA_READ:
        case IPC_M_STATE_CHANGE_AUTHORIZE:
                return true;
        default:
                return false;
        }
}

/*
 * Functions that preprocess answer before sending it to the recepient.
 */

/** Decide if the caller (e.g. ipc_answer()) should save the old call contents
 * for answer_preprocess().
 *
 * @param call Call structure to be decided.
 *
 * @return true if the old call contents should be saved.
 *
 */
static inline bool answer_need_old(call_t *call)
{
        switch (ipc_get_imethod(&call->data)) {
        case IPC_M_CONNECT_TO_ME:
        case IPC_M_CONNECT_ME_TO:
        case IPC_M_PAGE_IN:
        case IPC_M_SHARE_OUT:
        case IPC_M_SHARE_IN:
        case IPC_M_DATA_WRITE:
        case IPC_M_DATA_READ:
        case IPC_M_STATE_CHANGE_AUTHORIZE:
                return true;
        default:
                return false;
        }
}

/** Interpret process answer as control information.
 *
 * This function is called directly after sys_ipc_answer().
 *
 * @param answer  Call structure with the answer.
 * @param olddata Saved data of the request.
 *
 * @return Return EOK on success or an error code.
 *
 */
errno_t answer_preprocess(call_t *answer, ipc_data_t *olddata)
{
        errno_t rc = EOK;

        spinlock_lock(&answer->forget_lock);
        if (answer->forget) {
                /*
                 * This is a forgotten call and answer->sender is not valid.
                 */
                spinlock_unlock(&answer->forget_lock);

                SYSIPC_OP(answer_cleanup, answer, olddata);
                return rc;
        } else {
                assert(answer->active);

                /*
                 * Mark the call as inactive to prevent _ipc_answer_free_call()
                 * from attempting to remove the call from the active list
                 * itself.
                 */
                answer->active = false;

                /*
                 * Remove the call from the sender's active call list.
                 * We enforce this locking order so that any potential
                 * concurrently executing forget operation is forced to
                 * release its active_calls_lock and lose the race to
                 * forget this soon to be answered call.
                 */
                spinlock_lock(&answer->sender->active_calls_lock);
                list_remove(&answer->ta_link);
                spinlock_unlock(&answer->sender->active_calls_lock);
        }
        spinlock_unlock(&answer->forget_lock);

        if ((errno_t) ipc_get_retval(&answer->data) == EHANGUP) {
                phone_t *phone = answer->caller_phone;
                mutex_lock(&phone->lock);
                if (phone->state == IPC_PHONE_CONNECTED) {
                        irq_spinlock_lock(&phone->callee->lock, true);
                        list_remove(&phone->link);
                        /* Drop callee->connected_phones reference */
                        kobject_put(phone->kobject);
                        phone->state = IPC_PHONE_SLAMMED;
                        phone->label = 0;
                        irq_spinlock_unlock(&phone->callee->lock, true);
                }
                mutex_unlock(&phone->lock);
        }

        if (!olddata)
                return rc;

        return SYSIPC_OP(answer_preprocess, answer, olddata);
}

/** Called before the request is sent.
 *
 * @param call  Call structure with the request.
 * @param phone Phone that the call will be sent through.
 *
 * @return Return 0 on success, ELIMIT or EPERM on error.
 *
 */
static errno_t request_preprocess(call_t *call, phone_t *phone)
{
        call->request_method = ipc_get_imethod(&call->data);
        return SYSIPC_OP(request_preprocess, call, phone);
}

/*
 * Functions called to process received call/answer before passing it to uspace.
 */

/** Do basic kernel processing of received call answer.
 *
 * @param call Call structure with the answer.
 *
 */
static void process_answer(call_t *call)
{
        if (((errno_t) ipc_get_retval(&call->data) == EHANGUP) &&
            (call->flags & IPC_CALL_FORWARDED))
                ipc_set_retval(&call->data, EFORWARD);

        SYSIPC_OP(answer_process, call);
}

/** Do basic kernel processing of received call request.
 *
 * @param box  Destination answerbox structure.
 * @param call Call structure with the request.
 *
 * @return 0 if the call should be passed to userspace.
 * @return -1 if the call should be ignored.
 *
 */
static int process_request(answerbox_t *box, call_t *call)
{
        return SYSIPC_OP(request_process, call, box);
}

/** Make a call over IPC and wait for reply.
 *
 * @param handle       Phone capability handle for the call.
 * @param data[inout]  Structure with request/reply data.
 * @param priv         Value to be stored in call->priv.
 *
 * @return EOK on success.
 * @return ENOENT if there is no such phone handle.
 * @return ENOMEM if not enough memory to make the call
 *
 */
errno_t
ipc_req_internal(cap_phone_handle_t handle, ipc_data_t *data, sysarg_t priv)
{
        kobject_t *kobj = kobject_get(TASK, handle, KOBJECT_TYPE_PHONE);
        if (!kobj->phone)
                return ENOENT;

        call_t *call = ipc_call_alloc();
        if (!call) {
                kobject_put(kobj);
                return ENOMEM;
        }

        call->priv = priv;
        memcpy(call->data.args, data->args, sizeof(data->args));

        errno_t rc = request_preprocess(call, kobj->phone);
        if (!rc) {
#ifdef CONFIG_UDEBUG
                udebug_stoppable_begin();
#endif

                kobject_add_ref(call->kobject);
                rc = ipc_call_sync(kobj->phone, call);
                spinlock_lock(&call->forget_lock);
                bool forgotten = call->forget;
                spinlock_unlock(&call->forget_lock);
                kobject_put(call->kobject);

#ifdef CONFIG_UDEBUG
                udebug_stoppable_end();
#endif

                if (rc != EOK) {
                        if (!forgotten) {
                                /*
                                 * There was an error, but it did not result
                                 * in the call being forgotten. In fact, the
                                 * call was not even sent. We are still
                                 * its owners and are responsible for its
                                 * deallocation.
                                 */
                                kobject_put(call->kobject);
                        } else {
                                /*
                                 * The call was forgotten and it changed hands.
                                 * We are no longer expected to free it.
                                 */
                                assert(rc == EINTR);
                        }
                        kobject_put(kobj);
                        return rc;
                }

                process_answer(call);
        } else
                ipc_set_retval(&call->data, rc);

        memcpy(data->args, call->data.args, sizeof(data->args));
        kobject_put(call->kobject);
        kobject_put(kobj);

        return EOK;
}

/** Check that the task did not exceed the allowed limit of asynchronous calls
 * made over a phone.
 *
 * @param phone Phone to check the limit against.
 *
 * @return 0 if limit not reached or -1 if limit exceeded.
 *
 */
static int check_call_limit(phone_t *phone)
{
        if (atomic_load(&phone->active_calls) >= IPC_MAX_ASYNC_CALLS)
                return -1;

        return 0;
}

/** Make a fast asynchronous call over IPC.
 *
 * This function can only handle three arguments of payload, but is faster than
 * the generic function sys_ipc_call_async_slow().
 *
 * @param handle   Phone capability handle for the call.
 * @param imethod  Interface and method of the call.
 * @param arg1     Service-defined payload argument.
 * @param arg2     Service-defined payload argument.
 * @param arg3     Service-defined payload argument.
 * @param label    User-defined label.
 *
 * @return EOK on success.
 * @return An error code on error.
 *
 */
sys_errno_t sys_ipc_call_async_fast(cap_phone_handle_t handle, sysarg_t imethod,
    sysarg_t arg1, sysarg_t arg2, sysarg_t arg3, sysarg_t label)
{
        kobject_t *kobj = kobject_get(TASK, handle, KOBJECT_TYPE_PHONE);
        if (!kobj)
                return ENOENT;

        if (check_call_limit(kobj->phone)) {
                kobject_put(kobj);
                return ELIMIT;
        }

        call_t *call = ipc_call_alloc();
        if (!call) {
                kobject_put(kobj);
                return ENOMEM;
        }

        ipc_set_imethod(&call->data, imethod);
        ipc_set_arg1(&call->data, arg1);
        ipc_set_arg2(&call->data, arg2);
        ipc_set_arg3(&call->data, arg3);

        /*
         * To achieve deterministic behavior, zero out arguments that are beyond
         * the limits of the fast version.
         */
        ipc_set_arg5(&call->data, 0);

        /* Set the user-defined label */
        call->data.answer_label = label;

        errno_t res = request_preprocess(call, kobj->phone);

        if (!res)
                ipc_call(kobj->phone, call);
        else
                ipc_backsend_err(kobj->phone, call, res);

        kobject_put(kobj);
        return EOK;
}

/** Make an asynchronous IPC call allowing to transmit the entire payload.
 *
 * @param handle  Phone capability for the call.
 * @param data    Userspace address of call data with the request.
 * @param label   User-defined label.
 *
 * @return See sys_ipc_call_async_fast().
 *
 */
sys_errno_t sys_ipc_call_async_slow(cap_phone_handle_t handle, uspace_ptr_ipc_data_t data,
    sysarg_t label)
{
        kobject_t *kobj = kobject_get(TASK, handle, KOBJECT_TYPE_PHONE);
        if (!kobj)
                return ENOENT;

        if (check_call_limit(kobj->phone)) {
                kobject_put(kobj);
                return ELIMIT;
        }

        call_t *call = ipc_call_alloc();
        if (!call) {
                kobject_put(kobj);
                return ENOMEM;
        }

        errno_t rc = copy_from_uspace(&call->data.args, data + offsetof(ipc_data_t, args),
            sizeof(call->data.args));
        if (rc != EOK) {
                kobject_put(call->kobject);
                kobject_put(kobj);
                return (sys_errno_t) rc;
        }

        /* Set the user-defined label */
        call->data.answer_label = label;

        errno_t res = request_preprocess(call, kobj->phone);

        if (!res)
                ipc_call(kobj->phone, call);
        else
                ipc_backsend_err(kobj->phone, call, res);

        kobject_put(kobj);
        return EOK;
}

/** Forward a received call to another destination
 *
 * Common code for both the fast and the slow version.
 *
 * @param chandle  Call handle of the forwarded call.
 * @param phandle  Phone handle to use for forwarding.
 * @param imethod  New interface and method to use for the forwarded call.
 * @param arg1     New value of the first argument for the forwarded call.
 * @param arg2     New value of the second argument for the forwarded call.
 * @param arg3     New value of the third argument for the forwarded call.
 * @param arg4     New value of the fourth argument for the forwarded call.
 * @param arg5     New value of the fifth argument for the forwarded call.
 * @param mode     Flags that specify mode of the forward operation.
 * @param slow     If true, arg3, arg4 and arg5 are considered. Otherwise
 *                 the function considers only the fast version arguments:
 *                 i.e. arg1 and arg2.
 *
 * @return 0 on succes, otherwise an error code.
 *
 * Warning: Make sure that ARG5 is not rewritten for certain system IPC
 *
 */
static sys_errno_t sys_ipc_forward_common(cap_call_handle_t chandle,
    cap_phone_handle_t phandle, sysarg_t imethod, sysarg_t arg1, sysarg_t arg2,
    sysarg_t arg3, sysarg_t arg4, sysarg_t arg5, unsigned int mode, bool slow)
{
        kobject_t *ckobj = cap_unpublish(TASK, chandle, KOBJECT_TYPE_CALL);
        if (!ckobj)
                return ENOENT;

        call_t *call = ckobj->call;

        ipc_data_t old;
        bool need_old = answer_need_old(call);
        if (need_old)
                old = call->data;

        bool after_forward = false;
        errno_t rc;

        kobject_t *pkobj = kobject_get(TASK, phandle, KOBJECT_TYPE_PHONE);
        if (!pkobj) {
                rc = ENOENT;
                goto error;
        }

        if (!method_is_forwardable(ipc_get_imethod(&call->data))) {
                rc = EPERM;
                goto error;
        }

        call->flags |= IPC_CALL_FORWARDED;

        /*
         * User space is not allowed to change interface and method of system
         * methods on forward, allow changing ARG1, ARG2, ARG3 and ARG4 by
         * means of imethod, arg1, arg2 and arg3.
         * If the interface and method is immutable, don't change anything.
         */
        if (!method_is_immutable(ipc_get_imethod(&call->data))) {
                if (method_is_system(ipc_get_imethod(&call->data))) {
                        if (ipc_get_imethod(&call->data) ==
                            IPC_M_CONNECT_TO_ME) {
                                kobject_put((kobject_t *) call->priv);
                                call->priv = 0;
                                cap_free(TASK,
                                    (cap_handle_t) ipc_get_arg5(&call->data));
                        }

                        ipc_set_arg1(&call->data, imethod);
                        ipc_set_arg2(&call->data, arg1);
                        ipc_set_arg3(&call->data, arg2);

                        if (slow)
                                ipc_set_arg4(&call->data, arg3);

                        /*
                         * For system methods we deliberately don't
                         * overwrite ARG5.
                         */
                } else {
                        ipc_set_imethod(&call->data, imethod);
                        ipc_set_arg1(&call->data, arg1);
                        ipc_set_arg2(&call->data, arg2);
                        if (slow) {
                                ipc_set_arg3(&call->data, arg3);
                                ipc_set_arg4(&call->data, arg4);
                                ipc_set_arg5(&call->data, arg5);
                        }
                }
        }

        rc = ipc_forward(call, pkobj->phone, &TASK->answerbox, mode);
        if (rc != EOK) {
                after_forward = true;
                goto error;
        }

        cap_free(TASK, chandle);
        kobject_put(ckobj);
        kobject_put(pkobj);
        return EOK;

error:
        ipc_set_retval(&call->data, EFORWARD);
        (void) answer_preprocess(call, need_old ? &old : NULL);
        if (after_forward)
                _ipc_answer_free_call(call, false);
        else
                ipc_answer(&TASK->answerbox, call);

        cap_free(TASK, chandle);
        kobject_put(ckobj);

        if (pkobj)
                kobject_put(pkobj);
        return rc;
}

/** Forward a received call to another destination - fast version.
 *
 * In case the original interface and method is a system method, ARG1, ARG2
 * and ARG3 are overwritten in the forwarded message with the new method and
 * the new arg1 and arg2, respectively. Otherwise the IMETHOD, ARG1 and ARG2
 * are rewritten with the new interface and method, arg1 and arg2, respectively.
 * Also note there is a set of immutable methods, for which the new method and
 * arguments are not set and these values are ignored.
 *
 * @param chandle  Call handle of the call to forward.
 * @param phandle  Phone handle to use for forwarding.
 * @param imethod  New interface and method to use for the forwarded call.
 * @param arg1     New value of the first argument for the forwarded call.
 * @param arg2     New value of the second argument for the forwarded call.
 * @param mode     Flags that specify mode of the forward operation.
 *
 * @return 0 on succes, otherwise an error code.
 *
 */
sys_errno_t sys_ipc_forward_fast(cap_call_handle_t chandle,
    cap_phone_handle_t phandle, sysarg_t imethod, sysarg_t arg1, sysarg_t arg2,
    unsigned int mode)
{
        return sys_ipc_forward_common(chandle, phandle, imethod, arg1, arg2, 0,
            0, 0, mode, false);
}

/** Forward a received call to another destination - slow version.
 *
 * This function is the slow verision of the sys_ipc_forward_fast interface.
 * It can copy all five new arguments and the new interface and method from
 * the userspace. It naturally extends the functionality of the fast version.
 * For system methods, it additionally stores the new value of arg3 to ARG4.
 * For non-system methods, it additionally stores the new value of arg3, arg4
 * and arg5, respectively, to ARG3, ARG4 and ARG5, respectively.
 *
 * @param chandle  Call handle of the call to forward.
 * @param phandle  Phone handle to use for forwarding.
 * @param data     Userspace address of the new IPC data.
 * @param mode     Flags that specify mode of the forward operation.
 *
 * @return 0 on succes, otherwise an error code.
 *
 */
sys_errno_t sys_ipc_forward_slow(cap_call_handle_t chandle,
    cap_phone_handle_t phandle, uspace_ptr_ipc_data_t data, unsigned int mode)
{
        ipc_data_t newdata;
        errno_t rc = copy_from_uspace(&newdata.args, data + offsetof(ipc_data_t, args),
            sizeof(newdata.args));
        if (rc != EOK)
                return (sys_errno_t) rc;

        return sys_ipc_forward_common(chandle, phandle,
            ipc_get_imethod(&newdata), ipc_get_arg1(&newdata),
            ipc_get_arg2(&newdata), ipc_get_arg3(&newdata),
            ipc_get_arg4(&newdata), ipc_get_arg5(&newdata), mode, true);
}

/** Answer an IPC call - fast version.
 *
 * This function can handle only two return arguments of payload, but is faster
 * than the generic sys_ipc_answer().
 *
 * @param chandle  Call handle to be answered.
 * @param retval   Return value of the answer.
 * @param arg1     Service-defined return value.
 * @param arg2     Service-defined return value.
 * @param arg3     Service-defined return value.
 * @param arg4     Service-defined return value.
 *
 * @return 0 on success, otherwise an error code.
 *
 */
sys_errno_t sys_ipc_answer_fast(cap_call_handle_t chandle, sysarg_t retval,
    sysarg_t arg1, sysarg_t arg2, sysarg_t arg3, sysarg_t arg4)
{
        kobject_t *kobj = cap_unpublish(TASK, chandle, KOBJECT_TYPE_CALL);
        if (!kobj)
                return ENOENT;

        call_t *call = kobj->call;
        assert(!(call->flags & IPC_CALL_ANSWERED));

        ipc_data_t saved_data;
        bool saved;

        if (answer_need_old(call)) {
                memcpy(&saved_data, &call->data, sizeof(call->data));
                saved = true;
        } else
                saved = false;

        ipc_set_retval(&call->data, retval);
        ipc_set_arg1(&call->data, arg1);
        ipc_set_arg2(&call->data, arg2);
        ipc_set_arg3(&call->data, arg3);
        ipc_set_arg4(&call->data, arg4);

        /*
         * To achieve deterministic behavior, zero out arguments that are beyond
         * the limits of the fast version.
         */
        ipc_set_arg5(&call->data, 0);
        errno_t rc = answer_preprocess(call, saved ? &saved_data : NULL);

        ipc_answer(&TASK->answerbox, call);

        kobject_put(kobj);
        cap_free(TASK, chandle);

        return rc;
}

/** Answer an IPC call.
 *
 * @param chandle Call handle to be answered.
 * @param data    Userspace address of call data with the answer.
 *
 * @return 0 on success, otherwise an error code.
 *
 */
sys_errno_t sys_ipc_answer_slow(cap_call_handle_t chandle, uspace_ptr_ipc_data_t data)
{
        kobject_t *kobj = cap_unpublish(TASK, chandle, KOBJECT_TYPE_CALL);
        if (!kobj)
                return ENOENT;

        call_t *call = kobj->call;
        assert(!(call->flags & IPC_CALL_ANSWERED));

        ipc_data_t saved_data;
        bool saved;

        if (answer_need_old(call)) {
                memcpy(&saved_data, &call->data, sizeof(call->data));
                saved = true;
        } else
                saved = false;

        errno_t rc = copy_from_uspace(&call->data.args, data + offsetof(ipc_data_t, args),
            sizeof(call->data.args));
        if (rc != EOK) {
                /*
                 * Republish the capability so that the call does not get lost.
                 */
                cap_publish(TASK, chandle, kobj);
                return rc;
        }

        rc = answer_preprocess(call, saved ? &saved_data : NULL);

        ipc_answer(&TASK->answerbox, call);

        kobject_put(kobj);
        cap_free(TASK, chandle);

        return rc;
}

/** Hang up a phone.
 *
 * @param handle  Phone capability handle of the phone to be hung up.
 *
 * @return 0 on success or an error code.
 *
 */
sys_errno_t sys_ipc_hangup(cap_phone_handle_t handle)
{
        kobject_t *kobj = cap_unpublish(TASK, handle, KOBJECT_TYPE_PHONE);
        if (!kobj)
                return ENOENT;

        errno_t rc = ipc_phone_hangup(kobj->phone);
        kobject_put(kobj);
        cap_free(TASK, handle);
        return rc;
}

/** Wait for an incoming IPC call or an answer.
 *
 * @param calldata Pointer to buffer where the call/answer data is stored.
 * @param usec     Timeout. See waitq_sleep_timeout() for explanation.
 * @param flags    Select mode of sleep operation. See waitq_sleep_timeout()
 *                 for explanation.
 *
 * @return An error code on error.
 */
sys_errno_t sys_ipc_wait_for_call(uspace_ptr_ipc_data_t calldata, uint32_t usec,
    unsigned int flags)
{
        call_t *call = NULL;
        errno_t rc;
restart:

#ifdef CONFIG_UDEBUG
        udebug_stoppable_begin();
#endif

        rc = ipc_wait_for_call(&TASK->answerbox, usec,
            flags | SYNCH_FLAGS_INTERRUPTIBLE, &call);

#ifdef CONFIG_UDEBUG
        udebug_stoppable_end();
#endif

        if (rc != EOK)
                return rc;

        assert(call);

        call->data.flags = call->flags;
        if (call->flags & IPC_CALL_NOTIF) {
                /* Set the request_label to the interrupt counter */
                call->data.request_label = (sysarg_t) call->priv;

                call->data.cap_handle = CAP_NIL;

                STRUCT_TO_USPACE(calldata, &call->data);
                kobject_put(call->kobject);

                return EOK;
        }

        if (call->flags & IPC_CALL_ANSWERED) {
                process_answer(call);

                if (call->flags & IPC_CALL_DISCARD_ANSWER) {
                        kobject_put(call->kobject);
                        goto restart;
                }

                call->data.cap_handle = CAP_NIL;

                STRUCT_TO_USPACE(calldata, &call->data);
                kobject_put(call->kobject);

                return EOK;
        }

        if (process_request(&TASK->answerbox, call))
                goto restart;

        cap_handle_t handle = CAP_NIL;
        rc = cap_alloc(TASK, &handle);
        if (rc != EOK) {
                goto error;
        }

        call->data.cap_handle = handle;

        /*
         * Copy the whole call->data to include the request label.
         */
        rc = STRUCT_TO_USPACE(calldata, &call->data);
        if (rc != EOK)
                goto error;

        kobject_add_ref(call->kobject);
        cap_publish(TASK, handle, call->kobject);
        return EOK;

error:
        if (cap_handle_valid(handle))
                cap_free(TASK, handle);

        /*
         * The callee will not receive this call and no one else has a chance to
         * answer it. Set the IPC_CALL_AUTO_REPLY flag and return the EPARTY
         * error code.
         */
        ipc_data_t saved_data;
        bool saved;

        if (answer_need_old(call)) {
                memcpy(&saved_data, &call->data, sizeof(call->data));
                saved = true;
        } else
                saved = false;

        ipc_set_retval(&call->data, EPARTY);
        (void) answer_preprocess(call, saved ? &saved_data : NULL);
        call->flags |= IPC_CALL_AUTO_REPLY;
        ipc_answer(&TASK->answerbox, call);

        return rc;
}

/** Interrupt one thread from sys_ipc_wait_for_call().
 *
 */
sys_errno_t sys_ipc_poke(void)
{
        waitq_wake_one(&TASK->answerbox.wq);
        return EOK;
}

/** Connect an IRQ handler to a task.
 *
 * @param inr     IRQ number.
 * @param imethod Interface and method to be associated with the notification.
 * @param ucode   Uspace pointer to the top-half pseudocode.
 *
 * @param[out] uspace_handle  Uspace pointer to IRQ capability handle
 *
 * @return EPERM
 * @return Error code returned by ipc_irq_subscribe().
 *
 */
sys_errno_t sys_ipc_irq_subscribe(inr_t inr, sysarg_t imethod,
    uspace_ptr_irq_code_t ucode, uspace_ptr_cap_irq_handle_t uspace_handle)
{
        if (!(perm_get(TASK) & PERM_IRQ_REG))
                return EPERM;

        return ipc_irq_subscribe(&TASK->answerbox, inr, imethod, ucode, uspace_handle);
}

/** Disconnect an IRQ handler from a task.
 *
 * @param handle  IRQ capability handle.
 *
 * @return Zero on success or EPERM on error.
 *
 */
sys_errno_t sys_ipc_irq_unsubscribe(cap_irq_handle_t handle)
{
        if (!(perm_get(TASK) & PERM_IRQ_REG))
                return EPERM;

        ipc_irq_unsubscribe(&TASK->answerbox, handle);

        return 0;
}

/** Syscall connect to a task by ID
 *
 * @return Error code.
 *
 */
sys_errno_t sys_ipc_connect_kbox(uspace_ptr_task_id_t uspace_taskid,
    uspace_ptr_cap_phone_handle_t uspace_phone)
{
#ifdef CONFIG_UDEBUG
        task_id_t taskid;
        cap_phone_handle_t phone;

        errno_t rc = copy_from_uspace(&taskid, uspace_taskid, sizeof(task_id_t));
        if (rc == EOK) {
                rc = ipc_connect_kbox((task_id_t) taskid, &phone);
        }

        if (rc == EOK) {
                rc = copy_to_uspace(uspace_phone, &phone, sizeof(cap_handle_t));
                if (rc != EOK) {
                        // Clean up the phone on failure.
                        sys_ipc_hangup(phone);
                }
        }

        return (sys_errno_t) rc;
#else
        return (sys_errno_t) ENOTSUP;
#endif
}

/** @}
 */