/*
* 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 kernel_generic
* @{
*/
/**
* @file
* @brief Udebug hooks and data structure management.
*
* Udebug is an interface that makes userspace debuggers possible.
*/
#include <assert.h>
#include <debug.h>
#include <synch/waitq.h>
#include <udebug/udebug.h>
#include <errno.h>
#include <arch.h>
#include <proc/task.h>
#include <proc/thread.h>
/** 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);
condvar_initialize(&ut->active_cv);
ut->go_call = NULL;
ut->uspace_state = NULL;
ut->go = false;
ut->stoppable = true;
ut->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)
{
waitq_sleep(wq);
}
/** 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)
{
assert(THREAD);
assert(TASK);
mutex_lock(&TASK->udebug.lock);
int 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.
*
*/
call_t *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.active == true &&
THREAD->udebug.go == false) {
/*
* Thread was requested to stop - answer go call
*
*/
/* Make sure nobody takes this call away from us */
call_t *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)
{
restart:
mutex_lock(&TASK->udebug.lock);
mutex_lock(&THREAD->udebug.lock);
if ((THREAD->udebug.active) && (THREAD->udebug.go == false)) {
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);
}
}
/** Upon being scheduled to run, check if the current thread should stop.
*
* This function is called from clock().
*
*/
void udebug_before_thread_runs(void)
{
/* Check if we're supposed to stop */
udebug_stoppable_begin();
udebug_stoppable_end();
}
/** 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(sysarg_t a1, sysarg_t a2, sysarg_t a3,
sysarg_t a4, sysarg_t a5, sysarg_t a6, sysarg_t id, sysarg_t rc,
bool end_variant)
{
udebug_event_t etype =
end_variant ? UDEBUG_EVENT_SYSCALL_E : UDEBUG_EVENT_SYSCALL_B;
mutex_lock(&TASK->udebug.lock);
mutex_lock(&THREAD->udebug.lock);
/* Must only generate events when in debugging session and is go. */
if (THREAD->udebug.active != true || THREAD->udebug.go == false ||
(TASK->udebug.evmask & UDEBUG_EVMASK(etype)) == 0) {
mutex_unlock(&THREAD->udebug.lock);
mutex_unlock(&TASK->udebug.lock);
return;
}
/* Fill in the GO response. */
call_t *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);
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.go is false 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.go = false;
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);
}
/** Thread-creation event hook combined with attaching the thread.
*
* Must be called when a new userspace thread is created in the debugged
* task. Generates a THREAD_B event. Also attaches the thread @a t
* to the task @a ta.
*
* This is necessary to avoid a race condition where the BEGIN and THREAD_READ
* requests would be handled inbetween attaching the thread and checking it
* for being in a debugging session to send the THREAD_B event. We could then
* either miss threads or get some threads both in the thread list
* and get a THREAD_B event for them.
*
* @param thread Structure of the thread being created. Not locked, as the
* thread is not executing yet.
* @param task Task to which the thread should be attached.
*
*/
void udebug_thread_b_event_attach(struct thread *thread, struct task *task)
{
mutex_lock(&TASK->udebug.lock);
mutex_lock(&THREAD->udebug.lock);
thread_attach(thread, task);
LOG("Check state");
/* Must only generate events when in debugging session */
if (THREAD->udebug.active != true) {
LOG("udebug.active: %s, udebug.go: %s",
THREAD->udebug.active ? "Yes(+)" : "No",
THREAD->udebug.go ? "Yes(-)" : "No");
mutex_unlock(&THREAD->udebug.lock);
mutex_unlock(&TASK->udebug.lock);
return;
}
LOG("Trigger event");
call_t *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, (sysarg_t) thread);
/*
* Make sure udebug.go is false 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.go = false;
THREAD->udebug.cur_event = UDEBUG_EVENT_THREAD_B;
ipc_answer(&TASK->answerbox, call);
mutex_unlock(&THREAD->udebug.lock);
mutex_unlock(&TASK->udebug.lock);
LOG("Wait for Go");
udebug_wait_for_go(&THREAD->udebug.go_wq);
}
/** Thread-termination event hook.
*
* Must be called when the current thread is terminating.
* Generates a THREAD_E event.
*
*/
void udebug_thread_e_event(void)
{
mutex_lock(&TASK->udebug.lock);
mutex_lock(&THREAD->udebug.lock);
LOG("Check state");
/* Must only generate events when in debugging session. */
if (THREAD->udebug.active != true) {
LOG("udebug.active: %s, udebug.go: %s",
THREAD->udebug.active ? "Yes" : "No",
THREAD->udebug.go ? "Yes" : "No");
mutex_unlock(&THREAD->udebug.lock);
mutex_unlock(&TASK->udebug.lock);
return;
}
LOG("Trigger event");
call_t *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.active = false;
THREAD->udebug.cur_event = 0; /* None */
THREAD->udebug.go = false; /* Set to initial value */
ipc_answer(&TASK->answerbox, call);
mutex_unlock(&THREAD->udebug.lock);
mutex_unlock(&TASK->udebug.lock);
/*
* This event does not sleep - debugging has finished
* in this thread.
*
*/
}
/** Terminate task debugging session.
*
* Gracefully terminate 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 task Task structure. task->udebug.lock must be already locked.
*
* @return Zero on success or an error code.
*
*/
errno_t udebug_task_cleanup(struct task *task)
{
assert(mutex_locked(&task->udebug.lock));
if ((task->udebug.dt_state != UDEBUG_TS_BEGINNING) &&
(task->udebug.dt_state != UDEBUG_TS_ACTIVE)) {
return EINVAL;
}
LOG("Task %" PRIu64, task->taskid);
/* Finish debugging of all userspace threads */
list_foreach(task->threads, th_link, thread_t, thread) {
mutex_lock(&thread->udebug.lock);
/* Only process userspace threads. */
if (thread->uspace) {
/* Prevent any further debug activity in thread. */
thread->udebug.active = false;
thread->udebug.cur_event = 0; /* None */
/* Is the thread still go? */
if (thread->udebug.go == true) {
/*
* Yes, so clear go. As active == false,
* this doesn't affect anything.
*/
thread->udebug.go = false;
/* Answer GO call */
LOG("Answer GO call with EVENT_FINISHED.");
ipc_set_retval(&thread->udebug.go_call->data, 0);
ipc_set_arg1(&thread->udebug.go_call->data,
UDEBUG_EVENT_FINISHED);
ipc_answer(&task->answerbox, thread->udebug.go_call);
thread->udebug.go_call = NULL;
} else {
/*
* Debug_stop is already at initial value.
* Yet this means the thread needs waking up.
*
*/
/*
* thread's lock must not be held when calling
* waitq_close.
*
*/
waitq_close(&thread->udebug.go_wq);
}
mutex_unlock(&thread->udebug.lock);
condvar_broadcast(&thread->udebug.active_cv);
} else
mutex_unlock(&thread->udebug.lock);
}
task->udebug.dt_state = UDEBUG_TS_INACTIVE;
task->udebug.debugger = NULL;
return 0;
}
/** Wait for debugger to handle a fault in this thread.
*
* When a thread faults and someone is subscribed to the FAULT kernel event,
* this function is called to wait for a debugging session to give userspace
* a chance to examine the faulting thead/task. When the debugging session
* is over, this function returns (so that thread/task cleanup can continue).
*
*/
void udebug_thread_fault(void)
{
udebug_stoppable_begin();
/* Wait until a debugger attends to us. */
mutex_lock(&THREAD->udebug.lock);
while (!THREAD->udebug.active)
condvar_wait(&THREAD->udebug.active_cv, &THREAD->udebug.lock);
mutex_unlock(&THREAD->udebug.lock);
/*
* This is where we will typically block until a post-mortem debugger
* terminates the debugging session.
*/
udebug_stoppable_end();
}
/** @}
*/