WebSVN – HelenOS – Diff – /branches/dynload/kernel/generic/src/udebug/udebug_ops.c


/*
 * 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.debug_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.debug_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 debug_active == true, TASK->udebug.lock
     * is enough to ensure its existence and that debug_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.debug_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.debug_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;
}
 
/** @}
 */
 
Subversion Repositories HelenOS

(root)/branches/dynload/kernel/generic/src/udebug/udebug_ops.c – Rev 3474 → 3674
