source: mainline/kernel/generic/src/ipc/sysipc.c@ 057d21a

/*
 * 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 genericipc
 * @{
 */
/** @file
 */

#include <arch.h>
#include <proc/task.h>
#include <proc/thread.h>
#include <errno.h>
#include <memstr.h>
#include <debug.h>
#include <ipc/ipc.h>
#include <ipc/sysipc.h>
#include <ipc/irq.h>
#include <ipc/ipcrsc.h>
#include <ipc/kbox.h>
#include <synch/waitq.h>
#include <udebug/udebug_ipc.h>
#include <arch/interrupt.h>
#include <syscall/copy.h>
#include <security/cap.h>
#include <mm/as.h>
#include <print.h>

/**
 * Maximum buffer size allowed for IPC_M_DATA_WRITE and IPC_M_DATA_READ
 * requests.
 */
#define DATA_XFER_LIMIT         (64 * 1024)

#define GET_CHECK_PHONE(phone, phoneid, err) \
{ \
        if (phoneid > IPC_MAX_PHONES) { \
                err; \
        } \
        phone = &TASK->phones[phoneid]; \
}

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

/** Decide if the method is a system method.
 *
 * @param method        Method to be decided.
 *
 * @return              Return 1 if the method is a system method.
 *                      Otherwise return 0.
 */
static inline int method_is_system(unative_t method)
{
        if (method <= IPC_M_LAST_SYSTEM)
                return 1;
        return 0;
}

/** Decide if the message with this method is forwardable.
 *
 * - some system messages may be forwarded, for some of them
 *   it is useless
 *
 * @param method        Method to be decided.
 *
 * @return              Return 1 if the method is forwardable.
 *                      Otherwise return 0.
 */
static inline int method_is_forwardable(unative_t method)
{
        switch (method) {
        case IPC_M_CONNECTION_CLONE:
        case IPC_M_CONNECT_ME:
        case IPC_M_PHONE_HUNGUP:
                /* This message is meant only for the original recipient. */
                return 0;
        default:
                return 1;
        }
}

/** Decide if the message with this method is immutable on forward.
 *
 * - some system messages may be forwarded but their content cannot be altered
 *
 * @param method        Method to be decided.
 *
 * @return              Return 1 if the method is immutable on forward.
 *                      Otherwise return 0.
 */
static inline int method_is_immutable(unative_t method)
{
        switch (method) {
        case IPC_M_SHARE_OUT:
        case IPC_M_SHARE_IN:
        case IPC_M_DATA_WRITE:
        case IPC_M_DATA_READ:
                return 1;
                break;
        default:
                return 0;
        }
}


/***********************************************************************
 * 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              Return 1 if the old call contents should be saved.
 *                      Return 0 otherwise.
 */
static inline int answer_need_old(call_t *call)
{
        switch (IPC_GET_METHOD(call->data)) {
        case IPC_M_CONNECTION_CLONE:
        case IPC_M_CONNECT_ME:
        case IPC_M_CONNECT_TO_ME:
        case IPC_M_CONNECT_ME_TO:
        case IPC_M_SHARE_OUT:
        case IPC_M_SHARE_IN:
        case IPC_M_DATA_WRITE:
        case IPC_M_DATA_READ:
                return 1;
        default:
                return 0;
        }
}

/** 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 0 on success or an error code. 
 */
static inline int answer_preprocess(call_t *answer, ipc_data_t *olddata)
{
        int phoneid;

        if ((native_t) IPC_GET_RETVAL(answer->data) == EHANGUP) {
                /* In case of forward, hangup the forwared phone,
                 * not the originator
                 */
                mutex_lock(&answer->data.phone->lock);
                spinlock_lock(&TASK->answerbox.lock);
                if (answer->data.phone->state == IPC_PHONE_CONNECTED) {
                        list_remove(&answer->data.phone->link);
                        answer->data.phone->state = IPC_PHONE_SLAMMED;
                }
                spinlock_unlock(&TASK->answerbox.lock);
                mutex_unlock(&answer->data.phone->lock);
        }

        if (!olddata)
                return 0;

        if (IPC_GET_METHOD(*olddata) == IPC_M_CONNECTION_CLONE) {
                phoneid = IPC_GET_ARG1(*olddata);
                phone_t *phone = &TASK->phones[phoneid]; 
                if (IPC_GET_RETVAL(answer->data) != EOK) {
                        /*
                         * The recipient of the cloned phone rejected the offer.
                         * In this case, the connection was established at the
                         * request time and therefore we need to slam the phone.
                         * We don't merely hangup as that would result in
                         * sending IPC_M_HUNGUP to the third party on the
                         * other side of the cloned phone.
                         */
                        mutex_lock(&phone->lock);
                        if (phone->state == IPC_PHONE_CONNECTED) {
                                spinlock_lock(&phone->callee->lock);
                                list_remove(&phone->link);
                                phone->state = IPC_PHONE_SLAMMED;
                                spinlock_unlock(&phone->callee->lock);
                        }
                        mutex_unlock(&phone->lock);
                }
        } else if (IPC_GET_METHOD(*olddata) == IPC_M_CONNECT_ME) {
                phone_t *phone = (phone_t *)IPC_GET_ARG5(*olddata);
                if (IPC_GET_RETVAL(answer->data) != EOK) {
                        /*
                         * The other party on the cloned phoned rejected our
                         * request for connection on the protocol level.
                         * We need to break the connection without sending
                         * IPC_M_HUNGUP back.
                         */
                        mutex_lock(&phone->lock);
                        if (phone->state == IPC_PHONE_CONNECTED) {
                                spinlock_lock(&phone->callee->lock);
                                list_remove(&phone->link);
                                phone->state = IPC_PHONE_SLAMMED;
                                spinlock_unlock(&phone->callee->lock);
                        }
                        mutex_unlock(&phone->lock);
                }
        } else if (IPC_GET_METHOD(*olddata) == IPC_M_CONNECT_TO_ME) {
                phoneid = IPC_GET_ARG5(*olddata);
                if (IPC_GET_RETVAL(answer->data) != EOK) {
                        /* The connection was not accepted */
                        phone_dealloc(phoneid);
                } else {
                        /* The connection was accepted */
                        phone_connect(phoneid, &answer->sender->answerbox);
                        /* Set 'phone hash' as arg5 of response */
                        IPC_SET_ARG5(answer->data,
                            (unative_t) &TASK->phones[phoneid]);
                }
        } else if (IPC_GET_METHOD(*olddata) == IPC_M_CONNECT_ME_TO) {
                /* If the users accepted call, connect */
                if (IPC_GET_RETVAL(answer->data) == EOK) {
                        ipc_phone_connect((phone_t *) IPC_GET_ARG5(*olddata),
                            &TASK->answerbox);
                }
        } else if (IPC_GET_METHOD(*olddata) == IPC_M_SHARE_OUT) {
                if (!IPC_GET_RETVAL(answer->data)) {
                        /* Accepted, handle as_area receipt */
                        ipl_t ipl;
                        int rc;
                        as_t *as;
                        
                        ipl = interrupts_disable();
                        spinlock_lock(&answer->sender->lock);
                        as = answer->sender->as;
                        spinlock_unlock(&answer->sender->lock);
                        interrupts_restore(ipl);
                        
                        rc = as_area_share(as, IPC_GET_ARG1(*olddata),
                            IPC_GET_ARG2(*olddata), AS,
                            IPC_GET_ARG1(answer->data), IPC_GET_ARG3(*olddata));
                        IPC_SET_RETVAL(answer->data, rc);
                        return rc;
                }
        } else if (IPC_GET_METHOD(*olddata) == IPC_M_SHARE_IN) {
                if (!IPC_GET_RETVAL(answer->data)) { 
                        ipl_t ipl;
                        as_t *as;
                        int rc;
                        
                        ipl = interrupts_disable();
                        spinlock_lock(&answer->sender->lock);
                        as = answer->sender->as;
                        spinlock_unlock(&answer->sender->lock);
                        interrupts_restore(ipl);
                        
                        rc = as_area_share(AS, IPC_GET_ARG1(answer->data),
                            IPC_GET_ARG2(*olddata), as, IPC_GET_ARG1(*olddata),
                            IPC_GET_ARG2(answer->data));
                        IPC_SET_RETVAL(answer->data, rc);
                }
        } else if (IPC_GET_METHOD(*olddata) == IPC_M_DATA_READ) {
                ASSERT(!answer->buffer);
                if (!IPC_GET_RETVAL(answer->data)) {
                        /* The recipient agreed to send data. */
                        uintptr_t src = IPC_GET_ARG1(answer->data);
                        uintptr_t dst = IPC_GET_ARG1(*olddata);
                        size_t max_size = IPC_GET_ARG2(*olddata);
                        size_t size = IPC_GET_ARG2(answer->data);
                        if (size && size <= max_size) {
                                /*
                                 * Copy the destination VA so that this piece of
                                 * information is not lost.
                                 */
                                IPC_SET_ARG1(answer->data, dst);

                                answer->buffer = malloc(size, 0);
                                int rc = copy_from_uspace(answer->buffer,
                                    (void *) src, size);
                                if (rc) {
                                        IPC_SET_RETVAL(answer->data, rc);
                                        free(answer->buffer);
                                        answer->buffer = NULL;
                                }
                        } else if (!size) {
                                IPC_SET_RETVAL(answer->data, EOK);
                        } else {
                                IPC_SET_RETVAL(answer->data, ELIMIT);
                        }
                }
        } else if (IPC_GET_METHOD(*olddata) == IPC_M_DATA_WRITE) {
                ASSERT(answer->buffer);
                if (!IPC_GET_RETVAL(answer->data)) {
                        /* The recipient agreed to receive data. */
                        int rc;
                        uintptr_t dst;
                        size_t size;
                        size_t max_size;

                        dst = (uintptr_t)IPC_GET_ARG1(answer->data);
                        size = (size_t)IPC_GET_ARG2(answer->data);
                        max_size = (size_t)IPC_GET_ARG2(*olddata);

                        if (size <= max_size) {
                                rc = copy_to_uspace((void *) dst,
                                    answer->buffer, size);
                                if (rc)
                                        IPC_SET_RETVAL(answer->data, rc);
                        } else {
                                IPC_SET_RETVAL(answer->data, ELIMIT);
                        }
                }
                free(answer->buffer);
                answer->buffer = NULL;
        }
        return 0;
}

static void phones_lock(phone_t *p1, phone_t *p2)
{
        if (p1 < p2) {
                mutex_lock(&p1->lock);
                mutex_lock(&p2->lock);
        } else if (p1 > p2) {
                mutex_lock(&p2->lock);
                mutex_lock(&p1->lock);
        } else {
                mutex_lock(&p1->lock);
        }
}

static void phones_unlock(phone_t *p1, phone_t *p2)
{
        mutex_unlock(&p1->lock);
        if (p1 != p2)
                mutex_unlock(&p2->lock);
}

/** 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 int request_preprocess(call_t *call, phone_t *phone)
{
        int newphid;
        size_t size;
        uintptr_t src;
        int rc;

        switch (IPC_GET_METHOD(call->data)) {
        case IPC_M_CONNECTION_CLONE: {
                phone_t *cloned_phone;
                GET_CHECK_PHONE(cloned_phone, IPC_GET_ARG1(call->data),
                    return ENOENT);
                phones_lock(cloned_phone, phone);
                if ((cloned_phone->state != IPC_PHONE_CONNECTED) ||
                    phone->state != IPC_PHONE_CONNECTED) {
                        phones_unlock(cloned_phone, phone);
                        return EINVAL;
                }
                /*
                 * We can be pretty sure now that both tasks exist and we are
                 * connected to them. As we continue to hold the phone locks,
                 * we are effectively preventing them from finishing their
                 * potential cleanup.
                 */
                newphid = phone_alloc(phone->callee->task);
                if (newphid < 0) {
                        phones_unlock(cloned_phone, phone);
                        return ELIMIT;
                }
                ipc_phone_connect(&phone->callee->task->phones[newphid],
                    cloned_phone->callee);
                phones_unlock(cloned_phone, phone);
                /* Set the new phone for the callee. */
                IPC_SET_ARG1(call->data, newphid);
                break;
        }
        case IPC_M_CONNECT_ME:
                IPC_SET_ARG5(call->data, (unative_t) phone);
                break;
        case IPC_M_CONNECT_ME_TO:
                newphid = phone_alloc(TASK);
                if (newphid < 0)
                        return ELIMIT;
                /* Set arg5 for server */
                IPC_SET_ARG5(call->data, (unative_t) &TASK->phones[newphid]);
                call->flags |= IPC_CALL_CONN_ME_TO;
                call->priv = newphid;
                break;
        case IPC_M_SHARE_OUT:
                size = as_area_get_size(IPC_GET_ARG1(call->data));
                if (!size)
                        return EPERM;
                IPC_SET_ARG2(call->data, size);
                break;
        case IPC_M_DATA_READ:
                size = IPC_GET_ARG2(call->data);
                if ((size <= 0 || (size > DATA_XFER_LIMIT)))
                        return ELIMIT;
                break;
        case IPC_M_DATA_WRITE:
                src = IPC_GET_ARG1(call->data);
                size = IPC_GET_ARG2(call->data);
                
                if (size > DATA_XFER_LIMIT)
                        return ELIMIT;
                
                call->buffer = (uint8_t *) malloc(size, 0);
                rc = copy_from_uspace(call->buffer, (void *) src, size);
                if (rc != 0) {
                        free(call->buffer);
                        return rc;
                }
                break;
#ifdef CONFIG_UDEBUG
        case IPC_M_DEBUG_ALL:
                return udebug_request_preprocess(call, phone);
#endif
        default:
                break;
        }
        return 0;
}

/*******************************************************************************
 * 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 (((native_t) IPC_GET_RETVAL(call->data) == EHANGUP) &&
            (call->flags & IPC_CALL_FORWARDED))
                IPC_SET_RETVAL(call->data, EFORWARD);

        if (call->flags & IPC_CALL_CONN_ME_TO) {
                if (IPC_GET_RETVAL(call->data))
                        phone_dealloc(call->priv);
                else
                        IPC_SET_ARG5(call->data, call->priv);
        }

        if (call->buffer) {
                /* This must be an affirmative answer to IPC_M_DATA_READ. */
                /* or IPC_M_DEBUG_ALL/UDEBUG_M_MEM_READ... */
                uintptr_t dst = IPC_GET_ARG1(call->data);
                size_t size = IPC_GET_ARG2(call->data);
                int rc = copy_to_uspace((void *) dst, call->buffer, size);
                if (rc)
                        IPC_SET_RETVAL(call->data, rc);
                free(call->buffer);
                call->buffer = NULL;
        }
}

/** Do basic kernel processing of received call request.
 *
 * @param box           Destination answerbox structure.
 * @param call          Call structure with the request.
 *
 * @return              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)
{
        int phoneid;

        if (IPC_GET_METHOD(call->data) == IPC_M_CONNECT_TO_ME) {
                phoneid = phone_alloc(TASK);
                if (phoneid < 0) { /* Failed to allocate phone */
                        IPC_SET_RETVAL(call->data, ELIMIT);
                        ipc_answer(box, call);
                        return -1;
                }
                IPC_SET_ARG5(call->data, phoneid);
        }
        switch (IPC_GET_METHOD(call->data)) {
        case IPC_M_DEBUG_ALL:
                return -1;
        default:
                break;
        }
        return 0;
}

/** Make a fast call over IPC, wait for reply and return to user.
 *
 * This function can handle only three arguments of payload, but is faster than
 * the generic function (i.e. sys_ipc_call_sync_slow()).
 *
 * @param phoneid       Phone handle for the call.
 * @param method        Method of the call.
 * @param arg1          Service-defined payload argument.
 * @param arg2          Service-defined payload argument.
 * @param arg3          Service-defined payload argument.
 * @param data          Address of userspace structure where the reply call will
 *                      be stored.
 *
 * @return              Returns 0 on success.
 *                      Return ENOENT if there is no such phone handle.
 */
unative_t sys_ipc_call_sync_fast(unative_t phoneid, unative_t method,
    unative_t arg1, unative_t arg2, unative_t arg3, ipc_data_t *data)
{
        call_t call;
        phone_t *phone;
        int res;
        int rc;
        
        GET_CHECK_PHONE(phone, phoneid, return ENOENT);

        ipc_call_static_init(&call);
        IPC_SET_METHOD(call.data, method);
        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_ARG4(call.data, 0);
        IPC_SET_ARG5(call.data, 0);

        if (!(res = request_preprocess(&call, phone))) {
#ifdef CONFIG_UDEBUG
                udebug_stoppable_begin();
#endif
                rc = ipc_call_sync(phone, &call);
#ifdef CONFIG_UDEBUG
                udebug_stoppable_end();
#endif
                if (rc != EOK)
                        return rc;
                process_answer(&call);

        } else {
                IPC_SET_RETVAL(call.data, res);
        }
        rc = STRUCT_TO_USPACE(&data->args, &call.data.args);
        if (rc != 0)
                return rc;

        return 0;
}

/** Make a synchronous IPC call allowing to transmit the entire payload.
 *
 * @param phoneid       Phone handle for the call.
 * @param question      Userspace address of call data with the request.
 * @param reply         Userspace address of call data where to store the
 *                      answer.
 *
 * @return              Zero on success or an error code.
 */
unative_t sys_ipc_call_sync_slow(unative_t phoneid, ipc_data_t *question,
    ipc_data_t *reply)
{
        call_t call;
        phone_t *phone;
        int res;
        int rc;

        ipc_call_static_init(&call);
        rc = copy_from_uspace(&call.data.args, &question->args,
            sizeof(call.data.args));
        if (rc != 0)
                return (unative_t) rc;

        GET_CHECK_PHONE(phone, phoneid, return ENOENT);

        if (!(res = request_preprocess(&call, phone))) {
#ifdef CONFIG_UDEBUG
                udebug_stoppable_begin();
#endif
                rc = ipc_call_sync(phone, &call);
#ifdef CONFIG_UDEBUG
                udebug_stoppable_end();
#endif
                if (rc != EOK)
                        return rc;
                process_answer(&call);
        } else 
                IPC_SET_RETVAL(call.data, res);

        rc = STRUCT_TO_USPACE(&reply->args, &call.data.args);
        if (rc != 0)
                return rc;

        return 0;
}

/** Check that the task did not exceed the allowed limit of asynchronous calls.
 *
 * @return              Return 0 if limit not reached or -1 if limit exceeded.
 */
static int check_call_limit(void)
{
        if (atomic_preinc(&TASK->active_calls) > IPC_MAX_ASYNC_CALLS) {
                atomic_dec(&TASK->active_calls);
                return -1;
        }
        return 0;
}

/** Make a fast asynchronous call over IPC.
 *
 * This function can only handle four arguments of payload, but is faster than
 * the generic function sys_ipc_call_async_slow().
 *
 * @param phoneid       Phone handle for the call.
 * @param method        Method of the call.
 * @param arg1          Service-defined payload argument.
 * @param arg2          Service-defined payload argument.
 * @param arg3          Service-defined payload argument.
 * @param arg4          Service-defined payload argument.
 *
 * @return              Return call hash on success.
 *                      Return IPC_CALLRET_FATAL in case of a fatal error and 
 *                      IPC_CALLRET_TEMPORARY if there are too many pending
 *                      asynchronous requests; answers should be handled first.
 */
unative_t sys_ipc_call_async_fast(unative_t phoneid, unative_t method,
    unative_t arg1, unative_t arg2, unative_t arg3, unative_t arg4)
{
        call_t *call;
        phone_t *phone;
        int res;

        if (check_call_limit())
                return IPC_CALLRET_TEMPORARY;

        GET_CHECK_PHONE(phone, phoneid, return IPC_CALLRET_FATAL);

        call = ipc_call_alloc(0);
        IPC_SET_METHOD(call->data, method);
        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);

        if (!(res = request_preprocess(call, phone)))
                ipc_call(phone, call);
        else
                ipc_backsend_err(phone, call, res);

        return (unative_t) call;
}

/** Make an asynchronous IPC call allowing to transmit the entire payload.
 *
 * @param phoneid       Phone handle for the call.
 * @param data          Userspace address of call data with the request.
 *
 * @return              See sys_ipc_call_async_fast(). 
 */
unative_t sys_ipc_call_async_slow(unative_t phoneid, ipc_data_t *data)
{
        call_t *call;
        phone_t *phone;
        int res;
        int rc;

        if (check_call_limit())
                return IPC_CALLRET_TEMPORARY;

        GET_CHECK_PHONE(phone, phoneid, return IPC_CALLRET_FATAL);

        call = ipc_call_alloc(0);
        rc = copy_from_uspace(&call->data.args, &data->args,
            sizeof(call->data.args));
        if (rc != 0) {
                ipc_call_free(call);
                return (unative_t) rc;
        }
        if (!(res = request_preprocess(call, phone)))
                ipc_call(phone, call);
        else
                ipc_backsend_err(phone, call, res);

        return (unative_t) call;
}

/** Forward a received call to another destination - common code for both the
 * fast and the slow version.
 *
 * @param callid        Hash of the call to forward.
 * @param phoneid       Phone handle to use for forwarding.
 * @param method        New 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              Return 0 on succes, otherwise return an error code.
 *
 * Warning:     Make sure that ARG5 is not rewritten for certain system IPC
 */
static unative_t sys_ipc_forward_common(unative_t callid, unative_t phoneid,
    unative_t method, unative_t arg1, unative_t arg2, unative_t arg3,
    unative_t arg4, unative_t arg5, int mode, bool slow)
{
        call_t *call;
        phone_t *phone;

        call = get_call(callid);
        if (!call)
                return ENOENT;
        
        call->flags |= IPC_CALL_FORWARDED;

        GET_CHECK_PHONE(phone, phoneid, { 
                IPC_SET_RETVAL(call->data, EFORWARD);
                ipc_answer(&TASK->answerbox, call);
                return ENOENT;
        });

        if (!method_is_forwardable(IPC_GET_METHOD(call->data))) {
                IPC_SET_RETVAL(call->data, EFORWARD);
                ipc_answer(&TASK->answerbox, call);
                return EPERM;
        }

        /*
         * Userspace is not allowed to change method of system methods on
         * forward, allow changing ARG1, ARG2, ARG3 and ARG4 by means of method,
         * arg1, arg2 and arg3.
         * If the method is immutable, don't change anything.
         */
        if (!method_is_immutable(IPC_GET_METHOD(call->data))) {
                if (method_is_system(IPC_GET_METHOD(call->data))) {
                        if (IPC_GET_METHOD(call->data) == IPC_M_CONNECT_TO_ME)
                                phone_dealloc(IPC_GET_ARG5(call->data));

                        IPC_SET_ARG1(call->data, method);
                        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_METHOD(call->data, method);
                        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);
                        }
                }
        }

        return ipc_forward(call, phone, &TASK->answerbox, mode);
}

/** Forward a received call to another destination - fast version.
 *
 * @param callid        Hash of the call to forward.
 * @param phoneid       Phone handle to use for forwarding.
 * @param method        New 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              Return 0 on succes, otherwise return an error code.
 *
 * In case the original 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 METHOD, ARG1 and ARG2 are
 * rewritten with the new 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.
 */
unative_t sys_ipc_forward_fast(unative_t callid, unative_t phoneid,
    unative_t method, unative_t arg1, unative_t arg2, int mode)
{
        return sys_ipc_forward_common(callid, phoneid, method, arg1, arg2, 0, 0,
            0, mode, false); 
}

/** Forward a received call to another destination - slow version.
 *
 * @param callid        Hash of the call to forward.
 * @param phoneid       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              Return 0 on succes, otherwise return an error code.
 *
 * This function is the slow verision of the sys_ipc_forward_fast interface.
 * It can copy all five new arguments and the new 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.
 */
unative_t sys_ipc_forward_slow(unative_t callid, unative_t phoneid,
    ipc_data_t *data, int mode)
{
        ipc_data_t newdata;
        int rc;

        rc = copy_from_uspace(&newdata.args, &data->args,
            sizeof(newdata.args));
        if (rc != 0) 
                return (unative_t) rc;

        return sys_ipc_forward_common(callid, phoneid,
            IPC_GET_METHOD(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 callid        Hash of the call 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              Return 0 on success, otherwise return an error code.    
 */
unative_t sys_ipc_answer_fast(unative_t callid, unative_t retval,
    unative_t arg1, unative_t arg2, unative_t arg3, unative_t arg4)
{
        call_t *call;
        ipc_data_t saved_data;
        int saveddata = 0;
        int rc;

        /* Do not answer notification callids */
        if (callid & IPC_CALLID_NOTIFICATION)
                return 0;

        call = get_call(callid);
        if (!call)
                return ENOENT;

        if (answer_need_old(call)) {
                memcpy(&saved_data, &call->data, sizeof(call->data));
                saveddata = 1;
        }

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

        ipc_answer(&TASK->answerbox, call);
        return rc;
}

/** Answer an IPC call.
 *
 * @param callid        Hash of the call to be answered.
 * @param data          Userspace address of call data with the answer.
 *
 * @return              Return 0 on success, otherwise return an error code.
 */
unative_t sys_ipc_answer_slow(unative_t callid, ipc_data_t *data)
{
        call_t *call;
        ipc_data_t saved_data;
        int saveddata = 0;
        int rc;

        /* Do not answer notification callids */
        if (callid & IPC_CALLID_NOTIFICATION)
                return 0;

        call = get_call(callid);
        if (!call)
                return ENOENT;

        if (answer_need_old(call)) {
                memcpy(&saved_data, &call->data, sizeof(call->data));
                saveddata = 1;
        }
        rc = copy_from_uspace(&call->data.args, &data->args, 
            sizeof(call->data.args));
        if (rc != 0)
                return rc;

        rc = answer_preprocess(call, saveddata ? &saved_data : NULL);
        
        ipc_answer(&TASK->answerbox, call);

        return rc;
}

/** Hang up a phone.
 *
 * @param               Phone handle of the phone to be hung up.
 *
 * @return              Return 0 on success or an error code.
 */
unative_t sys_ipc_hangup(int phoneid)
{
        phone_t *phone;

        GET_CHECK_PHONE(phone, phoneid, return ENOENT);

        if (ipc_phone_hangup(phone))
                return -1;

        return 0;
}

/** 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              Hash of the call.
 *                      If IPC_CALLID_NOTIFICATION bit is set in the hash, the
 *                      call is a notification. IPC_CALLID_ANSWERED denotes an
 *                      answer.
 */
unative_t sys_ipc_wait_for_call(ipc_data_t *calldata, uint32_t usec, int flags)
{
        call_t *call;

restart:

#ifdef CONFIG_UDEBUG
        udebug_stoppable_begin();
#endif  
        call = ipc_wait_for_call(&TASK->answerbox, usec,
            flags | SYNCH_FLAGS_INTERRUPTIBLE);

#ifdef CONFIG_UDEBUG
        udebug_stoppable_end();
#endif
        if (!call)
                return 0;

        if (call->flags & IPC_CALL_NOTIF) {
                ASSERT(! (call->flags & IPC_CALL_STATIC_ALLOC));

                /* Set in_phone_hash to the interrupt counter */
                call->data.phone = (void *) call->priv;
                
                STRUCT_TO_USPACE(calldata, &call->data);

                ipc_call_free(call);
                
                return ((unative_t) call) | IPC_CALLID_NOTIFICATION;
        }

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

                ASSERT(! (call->flags & IPC_CALL_STATIC_ALLOC));

                if (call->flags & IPC_CALL_DISCARD_ANSWER) {
                        ipc_call_free(call);
                        goto restart;
                } else {
                        /*
                         * Decrement the counter of active calls only if the
                         * call is not an answer to IPC_M_PHONE_HUNGUP,
                         * which doesn't contribute to the counter.
                         */
                        atomic_dec(&TASK->active_calls);
                }

                STRUCT_TO_USPACE(&calldata->args, &call->data.args);
                ipc_call_free(call);

                return ((unative_t) call) | IPC_CALLID_ANSWERED;
        }

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

        /* Include phone address('id') of the caller in the request,
         * copy whole call->data, not only call->data.args */
        if (STRUCT_TO_USPACE(calldata, &call->data)) {
                /*
                 * The callee will not receive this call and no one else has
                 * a chance to answer it. Reply with the EPARTY error code.
                 */
                ipc_data_t saved_data;
                int saveddata = 0;

                if (answer_need_old(call)) {
                        memcpy(&saved_data, &call->data, sizeof(call->data));
                        saveddata = 1;
                }
                
                IPC_SET_RETVAL(call->data, EPARTY);
                (void) answer_preprocess(call, saveddata ? &saved_data : NULL);
                ipc_answer(&TASK->answerbox, call);
                return 0;
        }
        return (unative_t)call;
}

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

/** Connect an IRQ handler to a task.
 *
 * @param inr           IRQ number.
 * @param devno         Device number.
 * @param method        Method to be associated with the notification.
 * @param ucode         Uspace pointer to the top-half pseudocode.
 *
 * @return              EPERM or a return code returned by ipc_irq_register().
 */
unative_t sys_ipc_register_irq(inr_t inr, devno_t devno, unative_t method,
    irq_code_t *ucode)
{
        if (!(cap_get(TASK) & CAP_IRQ_REG))
                return EPERM;

        return ipc_irq_register(&TASK->answerbox, inr, devno, method, ucode);
}

/** Disconnect an IRQ handler from a task.
 *
 * @param inr           IRQ number.
 * @param devno         Device number.
 *
 * @return              Zero on success or EPERM on error..
 */
unative_t sys_ipc_unregister_irq(inr_t inr, devno_t devno)
{
        if (!(cap_get(TASK) & CAP_IRQ_REG))
                return EPERM;

        ipc_irq_unregister(&TASK->answerbox, inr, devno);

        return 0;
}

#include <console/console.h>

/**
 * Syscall connect to a task by id.
 *
 * @return              Phone id on success, or negative error code.
 */
unative_t sys_ipc_connect_kbox(sysarg64_t *uspace_taskid_arg)
{
#ifdef CONFIG_UDEBUG
        sysarg64_t taskid_arg;
        int rc;
        
        rc = copy_from_uspace(&taskid_arg, uspace_taskid_arg, sizeof(sysarg64_t));
        if (rc != 0)
                return (unative_t) rc;

        LOG("sys_ipc_connect_kbox(%" PRIu64 ")\n", taskid_arg.value);

        return ipc_connect_kbox(taskid_arg.value);
#else
        return (unative_t) ENOTSUP;
#endif
}

/** @}
 */