/*
* 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->go = false;
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 == true &&
THREAD->udebug.go == false) {
/*
* 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.go == false) {
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 is go. */
if (THREAD->udebug.debug_active != true ||
THREAD->udebug.go == false ||
(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.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);
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.go: %s\n",
THREAD->udebug.debug_active ? "yes(+)" : "no(-)",
THREAD->udebug.go ? "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.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("- 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.go: %s\n",
THREAD->udebug.debug_active ? "yes(+)" : "no(-)",
THREAD->udebug.go ? "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.go = false; /* 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 */
/* Is the thread still go? */
if (t->udebug.go == true) {
/*
* Yes, so clear go. As debug_active == false,
* this doesn't affect anything.
*/
t->udebug.go = false;
/* 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;
}
/** @}
*/