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/*

 * Copyright (c) 2008 Jiri Svoboda

 * 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 generic

 * @{

 */

/**

 * @file

 * @brief   Udebug hooks and data structure management.

 *

 * Udebug is an interface that makes userspace debuggers possible.

 *

 * Functions in this file are executed directly in each thread, which

 * may or may not be the subject of debugging. The udebug_stoppable_begin/end()

 * functions are also executed in the clock interrupt handler. To avoid

 * deadlock, functions in this file are protected from the interrupt

 * by locking the recursive lock THREAD->udebug.int_lock (just an atomic

 * variable). This prevents udebug_stoppable_begin/end() from being

 * executed in the interrupt handler (they are skipped).

 *

 * Functions in udebug_ops.c and udebug_ipc.c execute in different threads,

 * so they needn't be protected from the (preemptible) interrupt-initiated

 * code.

 */

#include <synch/waitq.h>

#include <debug.h>

#include <udebug/udebug.h>

#include <errno.h>

#include <arch.h>

static inline void udebug_int_lock(void)

{

    atomic_inc(&THREAD->udebug.int_lock);

}

static inline void udebug_int_unlock(void)

{

    atomic_dec(&THREAD->udebug.int_lock);

}

/** Initialize udebug part of task structure.

 *

 * Called as part of task structure initialization.

 * @param ut    Pointer to the structure to initialize.

 */

void udebug_task_init(udebug_task_t *ut)

{

    mutex_initialize(&ut->lock, MUTEX_PASSIVE);

    ut->dt_state = UDEBUG_TS_INACTIVE;

    ut->begin_call = NULL;

    ut->not_stoppable_count = 0;

    ut->evmask = 0;

}

/** Initialize udebug part of thread structure.

 *

 * Called as part of thread structure initialization.

 * @param ut    Pointer to the structure to initialize.

 */

void udebug_thread_initialize(udebug_thread_t *ut)

{

    mutex_initialize(&ut->lock, MUTEX_PASSIVE);

    waitq_initialize(&ut->go_wq);

    /*

     * At the beginning the thread is stoppable, so int_lock be set, too.

     */

    atomic_set(&ut->int_lock, 1);

    ut->go_call = NULL;

    ut->stop = true;

    ut->stoppable = true;

    ut->debug_active = false;

    ut->cur_event = 0; /* none */

}

/** Wait for a GO message.

 *

 * When a debugging event occurs in a thread or the thread is stopped,

 * this function is called to block the thread until a GO message

 * is received.

 *

 * @param wq    The wait queue used by the thread to wait for GO messages.

 */

static void udebug_wait_for_go(waitq_t *wq)

{

    int rc;

    ipl_t ipl;

    ipl = waitq_sleep_prepare(wq);

    wq->missed_wakeups = 0; /* Enforce blocking. */

    rc = waitq_sleep_timeout_unsafe(wq, SYNCH_NO_TIMEOUT, SYNCH_FLAGS_NONE);

    waitq_sleep_finish(wq, rc, ipl);

}

/** Do a preliminary check that a debugging session is in progress.

 *

 * This only requires the THREAD->udebug.lock mutex (and not TASK->udebug.lock

 * mutex). For an undebugged task, this will never block (while there could be

 * collisions by different threads on the TASK mutex), thus improving SMP

 * perormance for undebugged tasks.

 *

 * @return  True if the thread was in a debugging session when the function

 *      checked, false otherwise.

 */

static bool udebug_thread_precheck(void)

{

    bool res;

    mutex_lock(&THREAD->udebug.lock);

    res = THREAD->udebug.debug_active;

    mutex_unlock(&THREAD->udebug.lock);

    return res;

}

/** Start of stoppable section.

 *

 * A stoppable section is a section of code where if the thread can be stoped. In other words,

 * if a STOP operation is issued, the thread is guaranteed not to execute

 * any userspace instructions until the thread is resumed.

 *

 * Having stoppable sections is better than having stopping points, since

 * a thread can be stopped even when it is blocked indefinitely in a system

 * call (whereas it would not reach any stopping point).

 */

void udebug_stoppable_begin(void)

{

    int nsc;

    call_t *db_call, *go_call;

    ASSERT(THREAD);

    ASSERT(TASK);

    udebug_int_lock();

    /* Early check for undebugged tasks */

    if (!udebug_thread_precheck()) {

        udebug_int_unlock();

        return;

    }

    mutex_lock(&TASK->udebug.lock);

    nsc = --TASK->udebug.not_stoppable_count;

    /* Lock order OK, THREAD->udebug.lock is after TASK->udebug.lock */

    mutex_lock(&THREAD->udebug.lock);

    ASSERT(THREAD->udebug.stoppable == false);

    THREAD->udebug.stoppable = true;

    if (TASK->udebug.dt_state == UDEBUG_TS_BEGINNING && nsc == 0) {

        /*

         * This was the last non-stoppable thread. Reply to

         * DEBUG_BEGIN call.

         */

        db_call = TASK->udebug.begin_call;

        ASSERT(db_call);

        TASK->udebug.dt_state = UDEBUG_TS_ACTIVE;

        TASK->udebug.begin_call = NULL;

        IPC_SET_RETVAL(db_call->data, 0);

        ipc_answer(&TASK->answerbox, db_call);     

    } else if (TASK->udebug.dt_state == UDEBUG_TS_ACTIVE) {

        /*

         * Active debugging session

         */

        if (THREAD->udebug.debug_active && THREAD->udebug.stop) {

            /*

             * Thread was requested to stop - answer go call

             */

            /* Make sure nobody takes this call away from us */

            go_call = THREAD->udebug.go_call;

            THREAD->udebug.go_call = NULL;

            ASSERT(go_call);

            IPC_SET_RETVAL(go_call->data, 0);

            IPC_SET_ARG1(go_call->data, UDEBUG_EVENT_STOP);

            THREAD->udebug.cur_event = UDEBUG_EVENT_STOP;

                ipc_answer(&TASK->answerbox, go_call);

        }

    }

    mutex_unlock(&THREAD->udebug.lock);

        mutex_unlock(&TASK->udebug.lock);

}

/** End of a stoppable section.

 *

 * This is the point where the thread will block if it is stopped.

 * (As, by definition, a stopped thread must not leave its stoppable section).

 */

void udebug_stoppable_end(void)

{

    /* Early check for undebugged tasks */

    if (!udebug_thread_precheck()) {

        udebug_int_unlock();

        return;

    }

restart:

    mutex_lock(&TASK->udebug.lock);

    mutex_lock(&THREAD->udebug.lock);

    if (THREAD->udebug.debug_active &&

        THREAD->udebug.stop == true) {

        TASK->udebug.begin_call = NULL;

        mutex_unlock(&THREAD->udebug.lock);

        mutex_unlock(&TASK->udebug.lock);

        udebug_wait_for_go(&THREAD->udebug.go_wq);

        goto restart;

        /* must try again - have to lose stoppability atomically */

    } else {

        ++TASK->udebug.not_stoppable_count;

        ASSERT(THREAD->udebug.stoppable == true);

        THREAD->udebug.stoppable = false;

        mutex_unlock(&THREAD->udebug.lock);

        mutex_unlock(&TASK->udebug.lock);

    }

    udebug_int_unlock();

}

/** Upon being scheduled to run, check if the current thread should stop.

 *

 * This function is called from clock(). Preemption is enabled.

 * interrupts are disabled, but since this is called after

 * being scheduled-in, we can enable them, if we're careful enough

 * not to allow arbitrary recursion or deadlock with the thread context.

 */

void udebug_before_thread_runs(void)

{

    ipl_t ipl;

    return;

    ASSERT(!PREEMPTION_DISABLED);

    /*

     * Prevent agains re-entering, such as when preempted inside this

     * function.

     */

    if (atomic_get(&THREAD->udebug.int_lock) != 0)

        return;

    udebug_int_lock();

    ipl = interrupts_enable();

    /* Now we're free to do whatever we need (lock mutexes, sleep, etc.) */

    /* Check if we're supposed to stop */

    udebug_stoppable_begin();

    udebug_stoppable_end();

    interrupts_restore(ipl);

    udebug_int_unlock();

}

/** Syscall event hook.

 *

 * Must be called before and after servicing a system call. This generates

 * a SYSCALL_B or SYSCALL_E event, depending on the value of @a end_variant.

 */

void udebug_syscall_event(unative_t a1, unative_t a2, unative_t a3,

    unative_t a4, unative_t a5, unative_t a6, unative_t id, unative_t rc,

    bool end_variant)

{

    call_t *call;

    udebug_event_t etype;

    etype = end_variant ? UDEBUG_EVENT_SYSCALL_E : UDEBUG_EVENT_SYSCALL_B;

    udebug_int_lock();

    /* Early check for undebugged tasks */

    if (!udebug_thread_precheck()) {

        udebug_int_unlock();

        return;

    }

    mutex_lock(&TASK->udebug.lock);

    mutex_lock(&THREAD->udebug.lock);

    /* Must only generate events when in debugging session and have go */

    if (THREAD->udebug.debug_active != true ||

        THREAD->udebug.stop == true ||

        (TASK->udebug.evmask & UDEBUG_EVMASK(etype)) == 0) {

        mutex_unlock(&THREAD->udebug.lock);

        mutex_unlock(&TASK->udebug.lock);

        return;

    }

    //printf("udebug_syscall_event\n");

    call = THREAD->udebug.go_call;

    THREAD->udebug.go_call = NULL;

    IPC_SET_RETVAL(call->data, 0);

    IPC_SET_ARG1(call->data, etype);

    IPC_SET_ARG2(call->data, id);

    IPC_SET_ARG3(call->data, rc);

    //printf("udebug_syscall_event/ipc_answer\n");

    THREAD->udebug.syscall_args[0] = a1;

    THREAD->udebug.syscall_args[1] = a2;

    THREAD->udebug.syscall_args[2] = a3;

    THREAD->udebug.syscall_args[3] = a4;

    THREAD->udebug.syscall_args[4] = a5;

    THREAD->udebug.syscall_args[5] = a6;

    /*

     * Make sure udebug.stop is true when going to sleep

     * in case we get woken up by DEBUG_END. (At which

     * point it must be back to the initial true value).

     */

    THREAD->udebug.stop = true;

    THREAD->udebug.cur_event = etype;

    ipc_answer(&TASK->answerbox, call);

    mutex_unlock(&THREAD->udebug.lock);

    mutex_unlock(&TASK->udebug.lock);

    udebug_wait_for_go(&THREAD->udebug.go_wq);

    udebug_int_unlock();

}

/** Thread-creation event hook.

 *

 * Must be called when a new userspace thread is created in the debugged

 * task. Generates a THREAD_B event.

 *

 * @param t Structure of the thread being created. Not locked, as the

 *      thread is not executing yet.

 */

void udebug_thread_b_event(struct thread *t)

{

    call_t *call;

    udebug_int_lock();

    mutex_lock(&TASK->udebug.lock);

    mutex_lock(&THREAD->udebug.lock);

    LOG("udebug_thread_b_event\n");

    LOG("- check state\n");

    /* Must only generate events when in debugging session */

    if (THREAD->udebug.debug_active != true) {

        LOG("- debug_active: %s, udebug.stop: %s\n",

            THREAD->udebug.debug_active ? "yes(+)" : "no(-)",

            THREAD->udebug.stop ? "yes(-)" : "no(+)");

        mutex_unlock(&THREAD->udebug.lock);

        mutex_unlock(&TASK->udebug.lock);

        return;

    }

    LOG("- trigger event\n");

    call = THREAD->udebug.go_call;

    THREAD->udebug.go_call = NULL;

    IPC_SET_RETVAL(call->data, 0);

    IPC_SET_ARG1(call->data, UDEBUG_EVENT_THREAD_B);

    IPC_SET_ARG2(call->data, (unative_t)t);

    /*

     * Make sure udebug.stop is true when going to sleep

     * in case we get woken up by DEBUG_END. (At which

     * point it must be back to the initial true value).

     */

    THREAD->udebug.stop = true;

    THREAD->udebug.cur_event = UDEBUG_EVENT_THREAD_B;

    ipc_answer(&TASK->answerbox, call);

    mutex_unlock(&THREAD->udebug.lock);

    mutex_unlock(&TASK->udebug.lock);

    LOG("- sleep\n");

    udebug_wait_for_go(&THREAD->udebug.go_wq);

    udebug_int_unlock();

}

/** Thread-termination event hook.

 *

 * Must be called when the current thread is terminating.

 * Generates a THREAD_E event.

 */

void udebug_thread_e_event(void)

{

    call_t *call;

    udebug_int_lock();

    mutex_lock(&TASK->udebug.lock);

    mutex_lock(&THREAD->udebug.lock);

    LOG("udebug_thread_e_event\n");

    LOG("- check state\n");

    /* Must only generate events when in debugging session */

    if (THREAD->udebug.debug_active != true) {

/*      printf("- debug_active: %s, udebug.stop: %s\n",

            THREAD->udebug.debug_active ? "yes(+)" : "no(-)",

            THREAD->udebug.stop ? "yes(-)" : "no(+)");*/

        mutex_unlock(&THREAD->udebug.lock);

        mutex_unlock(&TASK->udebug.lock);

        return;

    }

    LOG("- trigger event\n");

    call = THREAD->udebug.go_call;

    THREAD->udebug.go_call = NULL;

    IPC_SET_RETVAL(call->data, 0);

    IPC_SET_ARG1(call->data, UDEBUG_EVENT_THREAD_E);

    /* Prevent any further debug activity in thread */

    THREAD->udebug.debug_active = false;

    THREAD->udebug.cur_event = 0;       /* none */

    THREAD->udebug.stop = true; /* set to initial value */

    ipc_answer(&TASK->answerbox, call);

    mutex_unlock(&THREAD->udebug.lock);

    mutex_unlock(&TASK->udebug.lock);

    /* Leave int_lock enabled */

    /* This event does not sleep - debugging has finished in this thread */

}

/**

 * Terminate task debugging session.

 *

 * Gracefully terminates the debugging session for a task. If the debugger

 * is still waiting for events on some threads, it will receive a

 * FINISHED event for each of them.

 *

 * @param ta    Task structure. ta->udebug.lock must be already locked.

 * @return  Zero on success or negative error code.

 */

int udebug_task_cleanup(struct task *ta)

{

    thread_t *t;

    link_t *cur;

    int flags;

    ipl_t ipl;

    LOG("udebug_task_cleanup()\n");

    LOG("task %" PRIu64 "\n", ta->taskid);

    udebug_int_lock();

    if (ta->udebug.dt_state != UDEBUG_TS_BEGINNING &&

        ta->udebug.dt_state != UDEBUG_TS_ACTIVE) {

        LOG("udebug_task_cleanup(): task not being debugged\n");

        return EINVAL;

    }

    /* Finish debugging of all userspace threads */

    for (cur = ta->th_head.next; cur != &ta->th_head; cur = cur->next) {

        t = list_get_instance(cur, thread_t, th_link);

        mutex_lock(&t->udebug.lock);

        ipl = interrupts_disable();

        spinlock_lock(&t->lock);

        flags = t->flags;

        spinlock_unlock(&t->lock);

        interrupts_restore(ipl);

        /* Only process userspace threads */

        if ((flags & THREAD_FLAG_USPACE) != 0) {

            /* Prevent any further debug activity in thread */

            t->udebug.debug_active = false;

            t->udebug.cur_event = 0;    /* none */

            /* Still has go? */

            if (t->udebug.stop == false) {

                /*

                * Yes, so clear go. As debug_active == false,

                 * this doesn't affect anything.

                 */

                t->udebug.stop = true; 

                /* Answer GO call */

                LOG("answer GO call with EVENT_FINISHED\n");

                IPC_SET_RETVAL(t->udebug.go_call->data, 0);

                IPC_SET_ARG1(t->udebug.go_call->data,

                    UDEBUG_EVENT_FINISHED);

                ipc_answer(&ta->answerbox, t->udebug.go_call);

                t->udebug.go_call = NULL;

            } else {

                /*

                 * Debug_stop is already at initial value.

                 * Yet this means the thread needs waking up.

                 */

                /*

                 * t's lock must not be held when calling

                 * waitq_wakeup.

                 */

                waitq_wakeup(&t->udebug.go_wq, WAKEUP_FIRST);

            }

        }

        mutex_unlock(&t->udebug.lock);

    }

    ta->udebug.dt_state = UDEBUG_TS_INACTIVE;

    ta->udebug.debugger = NULL;

    udebug_int_unlock();

    return 0;

}

/** @}

 */