/**
* Main and Execute Commands
*/
int main(int argc, char* argv[]) {
char input_buffer[COMMAND_LENGTH];
char *tokens[NUM_TOKENS];
char currentDir[COMMAND_LENGTH];
struct sigaction handler;
handler.sa_handler = handle_SIGINT;
sigaction(SIGINT, &handler, NULL);
while (true) {
getcwd(currentDir, sizeof(currentDir));
// Use write because we need to use read() to work with
// signals, and read() is incompatible with printf().
write(STDOUT_FILENO, currentDir, strlen(currentDir));
write(STDOUT_FILENO, ">", strlen(">"));
_Bool in_background = false;
int token_count = 0;
char *bufCopy = read_command(input_buffer, tokens, &in_background, &token_count);
// Cmd was invalid, or it was part of the Ctr+C signal.
// Nothing was copied, and therefore there is nothing to be run.
if (bufCopy == NULL) {
continue;
}
int handledInline = handle_inline_commands(tokens, bufCopy, input_buffer, &in_background);
// Cmd was handled by the inline command handler.
if (handledInline != 0) {
continue;
}
pid_t pid = fork();
handle_fork(pid, in_background, tokens);
add_to_history(bufCopy);
// Cleanup any previously exited background child processes
// (The zombies)
while (waitpid(-1, NULL, WNOHANG) > 0);
}
return 0;
}
int main(int argc, char *argv[]) {
printf("\nThis is the server with pid %d listening on port %d\n", getpid(), SERVER_PORT);
// setup the server to bind and listen on a port
int s = listen_on(SERVER_PORT);
while(1) { // forever
int msgsock = accept_connection(s); // wait for a client to connect
// handle the request with a new process
handle_fork(msgsock);
}
close(s);
exit (0);
}
void sched_update(struct ls_state *ls)
{
struct sched_state *s = &ls->sched;
int old_tid = s->cur_agent->tid;
int new_tid;
/* wait until the guest is ready */
if (!s->guest_init_done) {
if (kern_sched_init_done(ls->eip)) {
s->guest_init_done = true;
/* Deprecated since kern_get_current_tid went away. */
// assert(old_tid == new_tid && "init tid mismatch");
} else {
return;
}
}
/* The Importance of Being Assertive, A Trivial Style Guideline for
* Serious Programmers, by Ben Blum */
if (s->entering_timer) {
assert(ls->eip == kern_get_timer_wrap_begin() &&
"simics is a clown and tried to delay our interrupt :<");
s->entering_timer = false;
} else {
if (kern_timer_entering(ls->eip)) {
lsprintf(DEV, "A timer tick that wasn't ours (0x%x).\n",
(int)READ_STACK(ls->cpu0, 0));
ls->eip = avoid_timer_interrupt_immediately(ls->cpu0);
}
}
/**********************************************************************
* Update scheduler state.
**********************************************************************/
if (kern_thread_switch(ls->cpu0, ls->eip, &new_tid) && new_tid != old_tid) {
/*
* So, fork needs to be handled twice, both here and below in the
* runnable case. And for kernels that trigger both, both places will
* need to have a check for whether the newly forked thread exists
* already.
*
* Sleep and vanish actually only need to happen here. They should
* check both the rq and the dq, 'cause there's no telling where the
* thread got moved to before. As for the descheduling case, that needs
* to check for a new type of action flag "asleep" or "vanished" (and
* I guess using last_vanished_agent might work), and probably just
* assert that that condition holds if the thread couldn't be found
* for the normal descheduling case.
*/
/* Has to be handled before updating cur_agent, of course. */
handle_sleep(s);
handle_vanish(s);
handle_unsleep(s, new_tid);
/* Careful! On some kernels, the trigger for a new agent forking
* (where it first gets added to the RQ) may happen AFTER its
* tcb is set to be the currently running thread. This would
* cause this case to be reached before agent_fork() is called,
* so agent_by_tid would fail. Instead, we have an option to
* find it later. (see the kern_thread_runnable case below.) */
struct agent *next = agent_by_tid_or_null(&s->rq, new_tid);
if (next == NULL) next = agent_by_tid_or_null(&s->dq, new_tid);
if (next != NULL) {
lsprintf(DEV, "switched threads %d -> %d\n", old_tid,
new_tid);
s->last_agent = s->cur_agent;
s->cur_agent = next;
/* This fork check is for kernels which context switch to a
* newly-forked thread before adding it to the runqueue - and
* possibly won't do so at all (if current_extra_runnable). We
* need to do agent_fork now. (agent_fork *also* needs to be
* handled below, for kernels which don't c-s to the new thread
* immediately.) The */
} else if (handle_fork(s, new_tid, false)) {
next = agent_by_tid_or_null(&s->dq, new_tid);
assert(next != NULL && "Newly forked thread not on DQ");
lsprintf(DEV, "switching threads %d -> %d\n", old_tid,
new_tid);
s->last_agent = s->cur_agent;
s->cur_agent = next;
} else {
lsprintf(ALWAYS, COLOUR_BOLD COLOUR_RED "Couldn't find "
"new thread %d; current %d; did you forget to "
"tell_landslide_forking()?\n" COLOUR_DEFAULT,
new_tid, s->cur_agent->tid);
assert(0);
}
/* Some debug info to help the studence. */
if (s->cur_agent->tid == kern_get_init_tid()) {
lsprintf(DEV, "Now running init.\n");
} else if (s->cur_agent->tid == kern_get_shell_tid()) {
lsprintf(DEV, "Now running shell.\n");
} else if (kern_has_idle() &&
s->cur_agent->tid == kern_get_idle_tid()) {
lsprintf(DEV, "Now idling.\n");
}
}
s->current_extra_runnable = kern_current_extra_runnable(ls->cpu0);
int target_tid;
int mutex_addr;
/* Timer interrupt handling. */
if (kern_timer_entering(ls->eip)) {
// XXX: same as the comment in the below condition.
if (!kern_timer_exiting(READ_STACK(ls->cpu0, 0))) {
assert(!ACTION(s, handling_timer));
} else {
lsprintf(DEV, "WARNING: allowing a nested timer on "
"tid %d's stack\n", s->cur_agent->tid);
}
ACTION(s, handling_timer) = true;
lsprintf(INFO, "%d timer enter from 0x%x\n", s->cur_agent->tid,
(unsigned int)READ_STACK(ls->cpu0, 0));
} else if (kern_timer_exiting(ls->eip)) {
if (ACTION(s, handling_timer)) {
// XXX: This condition is a hack to compensate for when
// simics "sometimes", when keeping a schedule-in-
// flight, takes the caused timer interrupt immediately,
// even before the iret.
if (!kern_timer_exiting(READ_STACK(ls->cpu0, 0))) {
ACTION(s, handling_timer) = false;
s->just_finished_reschedule = true;
}
/* If the schedule target was in a timer interrupt when we
* decided to schedule him, then now is when the operation
* finishes landing. (otherwise, see below)
* FIXME: should this be inside the above if statement? */
if (ACTION(s, schedule_target)) {
ACTION(s, schedule_target) = false;
s->schedule_in_flight = NULL;
}
} else {
lsprintf(INFO, "WARNING: exiting a non-timer interrupt "
"through a path shared with the timer..? (from 0x%x, #%d)\n", (int)READ_STACK(ls->cpu0, 0), (int)READ_STACK(ls->cpu0, -2));
}
/* Context switching. */
} else if (kern_context_switch_entering(ls->eip)) {
/* It -is- possible for a context switch to interrupt a
* context switch if a timer goes off before c-s disables
* interrupts. TODO: if we care, make this an int counter. */
ACTION(s, context_switch) = true;
/* Maybe update the voluntary resched trace. See schedule.h */
if (!ACTION(s, handling_timer)) {
lsprintf(DEV, "Voluntary resched tid ");
print_agent(DEV, s->cur_agent);
printf(DEV, "\n");
s->voluntary_resched_tid = s->cur_agent->tid;
if (s->voluntary_resched_stack != NULL)
MM_FREE(s->voluntary_resched_stack);
s->voluntary_resched_stack =
stack_trace(ls->cpu0, ls->eip, s->cur_agent->tid);
}
} else if (kern_context_switch_exiting(ls->eip)) {
assert(ACTION(s, cs_free_pass) || ACTION(s, context_switch));
ACTION(s, context_switch) = false;
ACTION(s, cs_free_pass) = false;
/* For threads that context switched of their own accord. */
if (!HANDLING_INTERRUPT(s)) {
s->just_finished_reschedule = true;
if (ACTION(s, schedule_target)) {
ACTION(s, schedule_target) = false;
s->schedule_in_flight = NULL;
}
}
/* Lifecycle. */
} else if (kern_forking(ls->eip)) {
assert_no_action(s, "forking");
ACTION(s, forking) = true;
} else if (kern_sleeping(ls->eip)) {
assert_no_action(s, "sleeping");
ACTION(s, sleeping) = true;
} else if (kern_vanishing(ls->eip)) {
assert_no_action(s, "vanishing");
ACTION(s, vanishing) = true;
} else if (kern_readline_enter(ls->eip)) {
assert_no_action(s, "readlining");
ACTION(s, readlining) = true;
} else if (kern_readline_exit(ls->eip)) {
assert(ACTION(s, readlining));
ACTION(s, readlining) = false;
/* Runnable state change (incl. consequences of fork, vanish, sleep). */
} else if (kern_thread_runnable(ls->cpu0, ls->eip, &target_tid)) {
/* A thread is about to become runnable. Was it just spawned? */
if (!handle_fork(s, target_tid, true)) {
agent_wake(s, target_tid);
}
} else if (kern_thread_descheduling(ls->cpu0, ls->eip, &target_tid)) {
/* A thread is about to deschedule. Is it vanishing/sleeping? */
agent_deschedule(s, target_tid);
/* Mutex tracking and noob deadlock detection */
} else if (kern_mutex_locking(ls->cpu0, ls->eip, &mutex_addr)) {
//assert(!ACTION(s, mutex_locking));
assert(!ACTION(s, mutex_unlocking));
ACTION(s, mutex_locking) = true;
s->cur_agent->blocked_on_addr = mutex_addr;
} else if (kern_mutex_blocking(ls->cpu0, ls->eip, &target_tid)) {
/* Possibly not the case - if this thread entered mutex_lock,
* then switched and someone took it, these would be set already
* assert(s->cur_agent->blocked_on == NULL);
* assert(s->cur_agent->blocked_on_tid == -1); */
lsprintf(DEV, "mutex: on 0x%x tid %d blocks, owned by %d\n",
s->cur_agent->blocked_on_addr, s->cur_agent->tid,
target_tid);
s->cur_agent->blocked_on_tid = target_tid;
if (deadlocked(s)) {
lsprintf(BUG, COLOUR_BOLD COLOUR_RED "DEADLOCK! ");
print_deadlock(BUG, s->cur_agent);
printf(BUG, "\n");
found_a_bug(ls);
}
} else if (kern_mutex_locking_done(ls->eip)) {
//assert(ACTION(s, mutex_locking));
assert(!ACTION(s, mutex_unlocking));
ACTION(s, mutex_locking) = false;
s->cur_agent->blocked_on = NULL;
s->cur_agent->blocked_on_tid = -1;
s->cur_agent->blocked_on_addr = -1;
/* no need to check for deadlock; this can't create a cycle. */
mutex_block_others(&s->rq, mutex_addr, s->cur_agent,
s->cur_agent->tid);
} else if (kern_mutex_unlocking(ls->cpu0, ls->eip, &mutex_addr)) {
/* It's allowed to have a mutex_unlock call inside a mutex_lock
* (and it can happen), or mutex_lock inside of mutex_lock, but
* not the other way around. */
assert(!ACTION(s, mutex_unlocking));
ACTION(s, mutex_unlocking) = true;
mutex_block_others(&s->rq, mutex_addr, NULL, -1);
} else if (kern_mutex_unlocking_done(ls->eip)) {
assert(ACTION(s, mutex_unlocking));
ACTION(s, mutex_unlocking) = false;
}
/**********************************************************************
* Exercise our will upon the guest kernel
**********************************************************************/
/* Some checks before invoking the arbiter. First see if an operation of
* ours is already in-flight. */
if (s->schedule_in_flight) {
if (s->schedule_in_flight == s->cur_agent) {
/* the in-flight schedule operation is cleared for
* landing. note that this may cause another one to
* be triggered again as soon as the context switcher
* and/or the timer handler finishes; it is up to the
* arbiter to decide this. */
assert(ACTION(s, schedule_target));
/* this condition should trigger in the middle of the
* switch, rather than after it finishes. (which is also
* why we leave the schedule_target flag turned on).
* the special case is for newly forked agents that are
* schedule targets - they won't exit timer or c-s above
* so here is where we have to clear it for them. */
if (ACTION(s, just_forked)) {
/* Interrupts are "probably" off, but that's why
* just_finished_reschedule is persistent. */
lsprintf(DEV, "Finished flying to %d.\n",
s->cur_agent->tid);
ACTION(s, schedule_target) = false;
ACTION(s, just_forked) = false;
s->schedule_in_flight = NULL;
s->just_finished_reschedule = true;
} else {
assert(ACTION(s, cs_free_pass) ||
ACTION(s, context_switch) ||
HANDLING_INTERRUPT(s));
}
/* The schedule_in_flight flag itself is cleared above,
* along with schedule_target. Sometimes sched_recover
* sets in_flight and needs it not cleared here. */
} else {
/* An undesirable thread has been context-switched away
* from either from an interrupt handler (timer/kbd) or
* of its own accord. We need to wait for it to get back
* to its own execution before triggering an interrupt
* on it; in the former case, this will be just after it
* irets; in the latter, just after the c-s returns. */
if (kern_timer_exiting(ls->eip) ||
(!HANDLING_INTERRUPT(s) &&
kern_context_switch_exiting(ls->eip)) ||
ACTION(s, just_forked)) {
/* an undesirable agent just got switched to;
* keep the pending schedule in the air. */
// XXX: this seems to get taken too soon? change
// it somehow to cause_.._immediately. and then
// see the asserts/comments in the action
// handling_timer sections above.
/* some kernels (pathos) still have interrupts
* off or scheduler locked at this point; so
* properties of !R */
if (interrupts_enabled(ls->cpu0) &&
kern_ready_for_timer_interrupt(ls->cpu0)) {
lsprintf(INFO, "keeping schedule in-"
"flight at 0x%x\n", ls->eip);
cause_timer_interrupt(ls->cpu0);
s->entering_timer = true;
s->delayed_in_flight = false;
} else {
lsprintf(INFO, "Want to keep schedule "
"in-flight at 0x%x; have to "
"delay\n", ls->eip);
s->delayed_in_flight = true;
}
/* If this was the special case where the
* undesirable thread was just forked, keeping
* the schedule in flight will cause it to do a
* normal context switch. So just_forked is no
* longer needed. */
ACTION(s, just_forked) = false;
} else if (s->delayed_in_flight &&
interrupts_enabled(ls->cpu0) &&
kern_ready_for_timer_interrupt(ls->cpu0)) {
lsprintf(INFO, "Delayed in-flight timer tick "
"at 0x%x\n", ls->eip);
cause_timer_interrupt(ls->cpu0);
s->entering_timer = true;
s->delayed_in_flight = false;
} else {
/* they'd better not have "escaped" */
assert(ACTION(s, cs_free_pass) ||
ACTION(s, context_switch) ||
HANDLING_INTERRUPT(s) ||
!interrupts_enabled(ls->cpu0) ||
!kern_ready_for_timer_interrupt(ls->cpu0));
}
}
/* in any case we have no more decisions to make here */
return;
} else if (ACTION(s, just_forked)) {
ACTION(s, just_forked) = false;
s->just_finished_reschedule = true;
}
assert(!s->schedule_in_flight);
/* Can't do anything before the test actually starts. */
if (ls->test.current_test == NULL) {
return;
}
/* XXX TODO: This will "leak" an undesirable thread to execute an
* instruction if the timer/kbd handler is an interrupt gate, so check
* also if we're about to iret and then examine the eflags on the
* stack. Also, "sti" and "popf" are interesting, so check for those.
* Also, do trap gates enable interrupts if they were off? o_O */
if (!interrupts_enabled(ls->cpu0)) {
return;
}
/* If a schedule operation is just finishing, we should allow the thread
* to get back to its own execution before making another choice. Note
* that when we previously decided to interrupt the thread, it will have
* executed the single instruction we made the choice at then taken the
* interrupt, so we return to the next instruction, not the same one. */
if (ACTION(s, schedule_target)) {
return;
}
/* TODO: have an extra mode which will allow us to preempt the timer
* handler. */
if (HANDLING_INTERRUPT(s) || !kern_ready_for_timer_interrupt(ls->cpu0)) {
return;
}
/* As kernel_specifics.h says, no preempting during mutex unblocking. */
if (ACTION(s, mutex_unlocking)) {
return;
}
/* Okay, are we at a choice point? */
bool voluntary;
bool just_finished_reschedule = s->just_finished_reschedule;
s->just_finished_reschedule = false;
/* TODO: arbiter may also want to see the trace_entry_t */
if (arbiter_interested(ls, just_finished_reschedule, &voluntary)) {
struct agent *a;
bool our_choice;
/* TODO: as an optimisation (in serialisation state / etc), the
* arbiter may return NULL if there was only one possible
* choice. */
if (arbiter_choose(ls, &a, &our_choice)) {
/* Effect the choice that was made... */
if (a != s->cur_agent) {
lsprintf(CHOICE, "from agent %d, arbiter chose "
"%d at 0x%x (called at 0x%x)\n",
s->cur_agent->tid, a->tid, ls->eip,
(unsigned int)READ_STACK(ls->cpu0, 0));
set_schedule_target(s, a);
cause_timer_interrupt(ls->cpu0);
s->entering_timer = true;
}
/* Record the choice that was just made. */
if (ls->test.test_ever_caused &&
ls->test.start_population != s->most_agents_ever) {
save_setjmp(&ls->save, ls, a->tid, our_choice,
false, voluntary);
}
} else {
lsprintf(BUG, "no agent was chosen at eip 0x%x\n",
ls->eip);
}
}
/* XXX TODO: it may be that not every timer interrupt triggers a context
* switch, so we should watch out if a handler doesn't enter the c-s. */
}