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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 operations.

 *

 * Udebug operations on tasks and threads are implemented here. The

 * functions defined here are called from the udebug_ipc module

 * when servicing udebug IPC messages.

 */

#include <debug.h>

#include <proc/task.h>

#include <proc/thread.h>

#include <arch.h>

#include <errno.h>

#include <syscall/copy.h>

#include <ipc/ipc.h>

#include <udebug/udebug.h>

#include <udebug/udebug_ops.h>

/**

 * Prepare a thread for a debugging operation.

 *

 * Simply put, return thread t with t->udebug.lock held,

 * but only if it verifies all conditions.

 *

 * Specifically, verifies that thread t exists, is a userspace thread,

 * and belongs to the current task (TASK). Verifies, that the thread

 * is (or is not) go according to being_go (typically false).

 * It also locks t->udebug.lock, making sure that t->udebug.active

 * is true - that the thread is in a valid debugging session.

 *

 * With this verified and the t->udebug.lock mutex held, it is ensured

 * that the thread cannot leave the debugging session, let alone cease

 * to exist.

 *

 * In this function, holding the TASK->udebug.lock mutex prevents the

 * thread from leaving the debugging session, while relaxing from

 * the t->lock spinlock to the t->udebug.lock mutex.

 *

 * @param t     Pointer, need not at all be valid.

 * @param being_go  Required thread state.

 *

 * Returns EOK if all went well, or an error code otherwise.

 */

static int _thread_op_begin(thread_t *t, bool being_go)

{

    task_id_t taskid;

    ipl_t ipl;

    taskid = TASK->taskid;

    mutex_lock(&TASK->udebug.lock);

    /* thread_exists() must be called with threads_lock held */

    ipl = interrupts_disable();

    spinlock_lock(&threads_lock);

    if (!thread_exists(t)) {

        spinlock_unlock(&threads_lock);

        interrupts_restore(ipl);

        mutex_unlock(&TASK->udebug.lock);

        return ENOENT;

    }

    /* t->lock is enough to ensure the thread's existence */

    spinlock_lock(&t->lock);

    spinlock_unlock(&threads_lock);

    /* Verify that 't' is a userspace thread. */

    if ((t->flags & THREAD_FLAG_USPACE) == 0) {

        /* It's not, deny its existence */

        spinlock_unlock(&t->lock);

        interrupts_restore(ipl);

        mutex_unlock(&TASK->udebug.lock);

        return ENOENT;

    }

    /* Verify debugging state. */

    if (t->udebug.active != true) {

        /* Not in debugging session or undesired GO state */

        spinlock_unlock(&t->lock);

        interrupts_restore(ipl);

        mutex_unlock(&TASK->udebug.lock);

        return ENOENT;

    }

    /*

     * Since the thread has active == true, TASK->udebug.lock

     * is enough to ensure its existence and that active remains

     * true.

     */

    spinlock_unlock(&t->lock);

    interrupts_restore(ipl);

    /* Only mutex TASK->udebug.lock left. */

    /* Now verify that the thread belongs to the current task. */

    if (t->task != TASK) {

        /* No such thread belonging this task*/

        mutex_unlock(&TASK->udebug.lock);

        return ENOENT;

    }

    /*

     * Now we need to grab the thread's debug lock for synchronization

     * of the threads stoppability/stop state.

     */

    mutex_lock(&t->udebug.lock);

    /* The big task mutex is no longer needed. */

    mutex_unlock(&TASK->udebug.lock);

    if (t->udebug.go != being_go) {

        /* Not in debugging session or undesired GO state. */

        mutex_unlock(&t->udebug.lock);

        return EINVAL;

    }

    /* Only t->udebug.lock left. */

    return EOK; /* All went well. */

}

/** End debugging operation on a thread. */

static void _thread_op_end(thread_t *t)

{

    mutex_unlock(&t->udebug.lock);

}

/** Begin debugging the current task.

 *

 * Initiates a debugging session for the current task (and its threads).

 * When the debugging session has started a reply will be sent to the

 * UDEBUG_BEGIN call. This may happen immediately in this function if

 * all the threads in this task are stoppable at the moment and in this

 * case the function returns 1.

 *

 * Otherwise the function returns 0 and the reply will be sent as soon as

 * all the threads become stoppable (i.e. they can be considered stopped).

 *

 * @param call  The BEGIN call we are servicing.

 * @return  0 (OK, but not done yet), 1 (done) or negative error code.

 */

int udebug_begin(call_t *call)

{

    int reply;

    thread_t *t;

    link_t *cur;

    LOG("udebug_begin()\n");

    mutex_lock(&TASK->udebug.lock);

    LOG("debugging task %llu\n", TASK->taskid);

    if (TASK->udebug.dt_state != UDEBUG_TS_INACTIVE) {

        mutex_unlock(&TASK->udebug.lock);

        LOG("udebug_begin(): busy error\n");

        return EBUSY;

    }

    TASK->udebug.dt_state = UDEBUG_TS_BEGINNING;

    TASK->udebug.begin_call = call;

    TASK->udebug.debugger = call->sender;

    if (TASK->udebug.not_stoppable_count == 0) {

        TASK->udebug.dt_state = UDEBUG_TS_ACTIVE;

        TASK->udebug.begin_call = NULL;

        reply = 1; /* immediate reply */

    } else {

        reply = 0; /* no reply */

    }

    /* Set udebug.active on all of the task's userspace threads. */

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

        t = list_get_instance(cur, thread_t, th_link);

        mutex_lock(&t->udebug.lock);

        if ((t->flags & THREAD_FLAG_USPACE) != 0)

            t->udebug.active = true;

        mutex_unlock(&t->udebug.lock);

    }

    mutex_unlock(&TASK->udebug.lock);

    LOG("udebug_begin() done (%s)\n",

        reply ? "reply" : "stoppability wait");

    return reply;

}

/** Finish debugging the current task.

 *

 * Closes the debugging session for the current task.

 * @return Zero on success or negative error code.

 */

int udebug_end(void)

{

    int rc;

    LOG("udebug_end()\n");

    mutex_lock(&TASK->udebug.lock);

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

    rc = udebug_task_cleanup(TASK);

    mutex_unlock(&TASK->udebug.lock);

    return rc;

}

/** Set the event mask.

 *

 * Sets the event mask that determines which events are enabled.

 *

 * @param mask  Or combination of events that should be enabled.

 * @return  Zero on success or negative error code.

 */

int udebug_set_evmask(udebug_evmask_t mask)

{

    LOG("udebug_set_mask()\n");

    mutex_lock(&TASK->udebug.lock);

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

        mutex_unlock(&TASK->udebug.lock);

        LOG("udebug_set_mask(): not active debuging session\n");

        return EINVAL;

    }

    TASK->udebug.evmask = mask;

    mutex_unlock(&TASK->udebug.lock);

    return 0;

}

/** Give thread GO.

 *

 * Upon recieving a go message, the thread is given GO. Being GO

 * means the thread is allowed to execute userspace code (until

 * a debugging event or STOP occurs, at which point the thread loses GO.

 *

 * @param t The thread to operate on (unlocked and need not be valid).

 * @param call  The GO call that we are servicing.

 */

int udebug_go(thread_t *t, call_t *call)

{

    int rc;

    /* On success, this will lock t->udebug.lock. */

    rc = _thread_op_begin(t, false);

    if (rc != EOK) {

        return rc;

    }

    t->udebug.go_call = call;

    t->udebug.go = true;

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

    /*

     * Neither t's lock nor threads_lock may be held during wakeup.

     */

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

    _thread_op_end(t);

    return 0;

}

/** Stop a thread (i.e. take its GO away)

 *

 * Generates a STOP event as soon as the thread becomes stoppable (i.e.

 * can be considered stopped).

 *

 * @param t The thread to operate on (unlocked and need not be valid).

 * @param call  The GO call that we are servicing.

 */

int udebug_stop(thread_t *t, call_t *call)

{

    int rc;

    LOG("udebug_stop()\n");

    /*

     * On success, this will lock t->udebug.lock. Note that this makes sure

     * the thread is not stopped.

     */

    rc = _thread_op_begin(t, true);

    if (rc != EOK) {

        return rc;

    }

    /* Take GO away from the thread. */

    t->udebug.go = false;

    if (t->udebug.stoppable != true) {

        /* Answer will be sent when the thread becomes stoppable. */

        _thread_op_end(t);

        return 0;

    }

    /*

     * Answer GO call.

     */

    LOG("udebug_stop - answering go call\n");

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

    call = t->udebug.go_call;

    t->udebug.go_call = NULL;

    IPC_SET_RETVAL(call->data, 0);

    IPC_SET_ARG1(call->data, UDEBUG_EVENT_STOP);

    LOG("udebug_stop/ipc_answer\n");

    THREAD->udebug.cur_event = UDEBUG_EVENT_STOP;

    _thread_op_end(t);

    mutex_lock(&TASK->udebug.lock);

    ipc_answer(&TASK->answerbox, call);

    mutex_unlock(&TASK->udebug.lock);

    LOG("udebog_stop/done\n");

    return 0;

}

/** Read the list of userspace threads in the current task.

 *

 * The list takes the form of a sequence of thread hashes (i.e. the pointers

 * to thread structures). A buffer of size @a buf_size is allocated and

 * a pointer to it written to @a buffer. The sequence of hashes is written

 * into this buffer.

 *

 * If the sequence is longer than @a buf_size bytes, only as much hashes

 * as can fit are copied. The number of thread hashes copied is stored

 * in @a n.

 *

 * The rationale for having @a buf_size is that this function is only

 * used for servicing the THREAD_READ message, which always specifies

 * a maximum size for the userspace buffer.

 *

 * @param buffer    The buffer for storing thread hashes.

 * @param buf_size  Buffer size in bytes.

 * @param n     The actual number of hashes copied will be stored here.

 */

int udebug_thread_read(void **buffer, size_t buf_size, size_t *n)

{

    thread_t *t;

    link_t *cur;

    unative_t tid;

    unsigned copied_ids;

    ipl_t ipl;

    unative_t *id_buffer;

    int flags;

    size_t max_ids;

    LOG("udebug_thread_read()\n");

    /* Allocate a buffer to hold thread IDs */

    id_buffer = malloc(buf_size, 0);

    mutex_lock(&TASK->udebug.lock);

    /* Verify task state */

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

        mutex_unlock(&TASK->udebug.lock);

        return EINVAL;

    }

    ipl = interrupts_disable();

    spinlock_lock(&TASK->lock);

    /* Copy down the thread IDs */

    max_ids = buf_size / sizeof(unative_t);

    copied_ids = 0;

    /* FIXME: make sure the thread isn't past debug shutdown... */

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

        /* Do not write past end of buffer */

        if (copied_ids >= max_ids) break;

        t = list_get_instance(cur, thread_t, th_link);

        spinlock_lock(&t->lock);

        flags = t->flags;

        spinlock_unlock(&t->lock);

        /* Not interested in kernel threads. */

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

            /* Using thread struct pointer as identification hash */

            tid = (unative_t) t;

            id_buffer[copied_ids++] = tid;

        }

    }

    spinlock_unlock(&TASK->lock);

    interrupts_restore(ipl);

    mutex_unlock(&TASK->udebug.lock);

    *buffer = id_buffer;

    *n = copied_ids * sizeof(unative_t);

    return 0;

}

/** Read the arguments of a system call.

 *

 * The arguments of the system call being being executed are copied

 * to an allocated buffer and a pointer to it is written to @a buffer.

 * The size of the buffer is exactly such that it can hold the maximum number

 * of system-call arguments.

 *

 * Unless the thread is currently blocked in a SYSCALL_B or SYSCALL_E event,

 * this function will fail with an EINVAL error code.

 *

 * @param buffer    The buffer for storing thread hashes.

 */

int udebug_args_read(thread_t *t, void **buffer)

{

    int rc;

    unative_t *arg_buffer;

    /* Prepare a buffer to hold the arguments. */

    arg_buffer = malloc(6 * sizeof(unative_t), 0);

    /* On success, this will lock t->udebug.lock. */

    rc = _thread_op_begin(t, false);

    if (rc != EOK) {

        return rc;

    }

    /* Additionally we need to verify that we are inside a syscall. */

    if (t->udebug.cur_event != UDEBUG_EVENT_SYSCALL_B &&

        t->udebug.cur_event != UDEBUG_EVENT_SYSCALL_E) {

        _thread_op_end(t);

        return EINVAL;

    }

    /* Copy to a local buffer before releasing the lock. */

    memcpy(arg_buffer, t->udebug.syscall_args, 6 * sizeof(unative_t));

    _thread_op_end(t);

    *buffer = arg_buffer;

    return 0;

}

/** Read the memory of the debugged task.

 *

 * Reads @a n bytes from the address space of the debugged task, starting

 * from @a uspace_addr. The bytes are copied into an allocated buffer

 * and a pointer to it is written into @a buffer.

 *

 * @param uspace_addr   Address from where to start reading.

 * @param n     Number of bytes to read.

 * @param buffer    For storing a pointer to the allocated buffer.

 */

int udebug_mem_read(unative_t uspace_addr, size_t n, void **buffer)

{

    void *data_buffer;

    int rc;

    /* Verify task state */

    mutex_lock(&TASK->udebug.lock);

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

        mutex_unlock(&TASK->udebug.lock);

        return EBUSY;

    }

    data_buffer = malloc(n, 0);

    /* NOTE: this is not strictly from a syscall... but that shouldn't

     * be a problem */

    rc = copy_from_uspace(data_buffer, (void *)uspace_addr, n);

    mutex_unlock(&TASK->udebug.lock);

    if (rc != 0) return rc;

    *buffer = data_buffer;

    return 0;

}

/** @}

 */