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Merge branch 'ptrace' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc into ptrace

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This commit is contained in:
Oleg Nesterov 2011-04-07 20:44:11 +02:00
commit e46bc9b6fd
6 changed files with 445 additions and 183 deletions
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379
kernel/signal.c
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@ -124,7 +124,7 @@ static inline int has_pending_signals(sigset_t *signal, sigset_t *blocked)
static int recalc_sigpending_tsk(struct task_struct *t)
{
if (t->signal->group_stop_count > 0 ||
if ((t->group_stop & GROUP_STOP_PENDING) ||
PENDING(&t->pending, &t->blocked) ||
PENDING(&t->signal->shared_pending, &t->blocked)) {
set_tsk_thread_flag(t, TIF_SIGPENDING);
@ -223,6 +223,83 @@ static inline void print_dropped_signal(int sig)
current->comm, current->pid, sig);
}
/**
* task_clear_group_stop_trapping - clear group stop trapping bit
* @task: target task
*
* If GROUP_STOP_TRAPPING is set, a ptracer is waiting for us. Clear it
* and wake up the ptracer. Note that we don't need any further locking.
* @task->siglock guarantees that @task->parent points to the ptracer.
*
* CONTEXT:
* Must be called with @task->sighand->siglock held.
*/
static void task_clear_group_stop_trapping(struct task_struct *task)
{
if (unlikely(task->group_stop & GROUP_STOP_TRAPPING)) {
task->group_stop &= ~GROUP_STOP_TRAPPING;
__wake_up_sync(&task->parent->signal->wait_chldexit,
TASK_UNINTERRUPTIBLE, 1);
}
}
/**
* task_clear_group_stop_pending - clear pending group stop
* @task: target task
*
* Clear group stop states for @task.
*
* CONTEXT:
* Must be called with @task->sighand->siglock held.
*/
void task_clear_group_stop_pending(struct task_struct *task)
{
task->group_stop &= ~(GROUP_STOP_PENDING | GROUP_STOP_CONSUME |
GROUP_STOP_DEQUEUED);
}
/**
* task_participate_group_stop - participate in a group stop
* @task: task participating in a group stop
*
* @task has GROUP_STOP_PENDING set and is participating in a group stop.
* Group stop states are cleared and the group stop count is consumed if
* %GROUP_STOP_CONSUME was set. If the consumption completes the group
* stop, the appropriate %SIGNAL_* flags are set.
*
* CONTEXT:
* Must be called with @task->sighand->siglock held.
*
* RETURNS:
* %true if group stop completion should be notified to the parent, %false
* otherwise.
*/
static bool task_participate_group_stop(struct task_struct *task)
{
struct signal_struct *sig = task->signal;
bool consume = task->group_stop & GROUP_STOP_CONSUME;
WARN_ON_ONCE(!(task->group_stop & GROUP_STOP_PENDING));
task_clear_group_stop_pending(task);
if (!consume)
return false;
if (!WARN_ON_ONCE(sig->group_stop_count == 0))
sig->group_stop_count--;
/*
* Tell the caller to notify completion iff we are entering into a
* fresh group stop. Read comment in do_signal_stop() for details.
*/
if (!sig->group_stop_count && !(sig->flags & SIGNAL_STOP_STOPPED)) {
sig->flags = SIGNAL_STOP_STOPPED;
return true;
}
return false;
}
/*
* allocate a new signal queue record
* - this may be called without locks if and only if t == current, otherwise an
@ -527,7 +604,7 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
* is to alert stop-signal processing code when another
* processor has come along and cleared the flag.
*/
tsk->signal->flags |= SIGNAL_STOP_DEQUEUED;
current->group_stop |= GROUP_STOP_DEQUEUED;
}
if ((info->si_code & __SI_MASK) == __SI_TIMER && info->si_sys_private) {
/*
@ -727,34 +804,14 @@ static int prepare_signal(int sig, struct task_struct *p, int from_ancestor_ns)
} else if (sig == SIGCONT) {
unsigned int why;
/*
* Remove all stop signals from all queues,
* and wake all threads.
* Remove all stop signals from all queues, wake all threads.
*/
rm_from_queue(SIG_KERNEL_STOP_MASK, &signal->shared_pending);
t = p;
do {
unsigned int state;
task_clear_group_stop_pending(t);
rm_from_queue(SIG_KERNEL_STOP_MASK, &t->pending);
/*
* If there is a handler for SIGCONT, we must make
* sure that no thread returns to user mode before
* we post the signal, in case it was the only
* thread eligible to run the signal handler--then
* it must not do anything between resuming and
* running the handler. With the TIF_SIGPENDING
* flag set, the thread will pause and acquire the
* siglock that we hold now and until we've queued
* the pending signal.
*
* Wake up the stopped thread _after_ setting
* TIF_SIGPENDING
*/
state = __TASK_STOPPED;
if (sig_user_defined(t, SIGCONT) && !sigismember(&t->blocked, SIGCONT)) {
set_tsk_thread_flag(t, TIF_SIGPENDING);
state |= TASK_INTERRUPTIBLE;
}
wake_up_state(t, state);
wake_up_state(t, __TASK_STOPPED);
} while_each_thread(p, t);
/*
@ -780,13 +837,6 @@ static int prepare_signal(int sig, struct task_struct *p, int from_ancestor_ns)
signal->flags = why | SIGNAL_STOP_CONTINUED;
signal->group_stop_count = 0;
signal->group_exit_code = 0;
} else {
/*
* We are not stopped, but there could be a stop
* signal in the middle of being processed after
* being removed from the queue. Clear that too.
*/
signal->flags &= ~SIGNAL_STOP_DEQUEUED;
}
}
@ -875,6 +925,7 @@ static void complete_signal(int sig, struct task_struct *p, int group)
signal->group_stop_count = 0;
t = p;
do {
task_clear_group_stop_pending(t);
sigaddset(&t->pending.signal, SIGKILL);
signal_wake_up(t, 1);
} while_each_thread(p, t);
@ -1109,6 +1160,7 @@ int zap_other_threads(struct task_struct *p)
p->signal->group_stop_count = 0;
while_each_thread(p, t) {
task_clear_group_stop_pending(t);
count++;
/* Don't bother with already dead threads */
@ -1536,16 +1588,30 @@ int do_notify_parent(struct task_struct *tsk, int sig)
return ret;
}
static void do_notify_parent_cldstop(struct task_struct *tsk, int why)
/**
* do_notify_parent_cldstop - notify parent of stopped/continued state change
* @tsk: task reporting the state change
* @for_ptracer: the notification is for ptracer
* @why: CLD_{CONTINUED|STOPPED|TRAPPED} to report
*
* Notify @tsk's parent that the stopped/continued state has changed. If
* @for_ptracer is %false, @tsk's group leader notifies to its real parent.
* If %true, @tsk reports to @tsk->parent which should be the ptracer.
*
* CONTEXT:
* Must be called with tasklist_lock at least read locked.
*/
static void do_notify_parent_cldstop(struct task_struct *tsk,
bool for_ptracer, int why)
{
struct siginfo info;
unsigned long flags;
struct task_struct *parent;
struct sighand_struct *sighand;
if (task_ptrace(tsk))
if (for_ptracer) {
parent = tsk->parent;
else {
} else {
tsk = tsk->group_leader;
parent = tsk->real_parent;
}
@ -1620,6 +1686,15 @@ static int sigkill_pending(struct task_struct *tsk)
sigismember(&tsk->signal->shared_pending.signal, SIGKILL);
}
/*
* Test whether the target task of the usual cldstop notification - the
* real_parent of @child - is in the same group as the ptracer.
*/
static bool real_parent_is_ptracer(struct task_struct *child)
{
return same_thread_group(child->parent, child->real_parent);
}
/*
* This must be called with current->sighand->siglock held.
*
@ -1631,10 +1706,12 @@ static int sigkill_pending(struct task_struct *tsk)
* If we actually decide not to stop at all because the tracer
* is gone, we keep current->exit_code unless clear_code.
*/
static void ptrace_stop(int exit_code, int clear_code, siginfo_t *info)
static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info)
__releases(&current->sighand->siglock)
__acquires(&current->sighand->siglock)
{
bool gstop_done = false;
if (arch_ptrace_stop_needed(exit_code, info)) {
/*
* The arch code has something special to do before a
@ -1655,21 +1732,49 @@ static void ptrace_stop(int exit_code, int clear_code, siginfo_t *info)
}
/*
* If there is a group stop in progress,
* we must participate in the bookkeeping.
* If @why is CLD_STOPPED, we're trapping to participate in a group
* stop. Do the bookkeeping. Note that if SIGCONT was delievered
* while siglock was released for the arch hook, PENDING could be
* clear now. We act as if SIGCONT is received after TASK_TRACED
* is entered - ignore it.
*/
if (current->signal->group_stop_count > 0)
--current->signal->group_stop_count;
if (why == CLD_STOPPED && (current->group_stop & GROUP_STOP_PENDING))
gstop_done = task_participate_group_stop(current);
current->last_siginfo = info;
current->exit_code = exit_code;
/* Let the debugger run. */
__set_current_state(TASK_TRACED);
/*
* TRACED should be visible before TRAPPING is cleared; otherwise,
* the tracer might fail do_wait().
*/
set_current_state(TASK_TRACED);
/*
* We're committing to trapping. Clearing GROUP_STOP_TRAPPING and
* transition to TASK_TRACED should be atomic with respect to
* siglock. This hsould be done after the arch hook as siglock is
* released and regrabbed across it.
*/
task_clear_group_stop_trapping(current);
spin_unlock_irq(&current->sighand->siglock);
read_lock(&tasklist_lock);
if (may_ptrace_stop()) {
do_notify_parent_cldstop(current, CLD_TRAPPED);
/*
* Notify parents of the stop.
*
* While ptraced, there are two parents - the ptracer and
* the real_parent of the group_leader. The ptracer should
* know about every stop while the real parent is only
* interested in the completion of group stop. The states
* for the two don't interact with each other. Notify
* separately unless they're gonna be duplicates.
*/
do_notify_parent_cldstop(current, true, why);
if (gstop_done && !real_parent_is_ptracer(current))
do_notify_parent_cldstop(current, false, why);
/*
* Don't want to allow preemption here, because
* sys_ptrace() needs this task to be inactive.
@ -1684,7 +1789,16 @@ static void ptrace_stop(int exit_code, int clear_code, siginfo_t *info)
/*
* By the time we got the lock, our tracer went away.
* Don't drop the lock yet, another tracer may come.
*
* If @gstop_done, the ptracer went away between group stop
* completion and here. During detach, it would have set
* GROUP_STOP_PENDING on us and we'll re-enter TASK_STOPPED
* in do_signal_stop() on return, so notifying the real
* parent of the group stop completion is enough.
*/
if (gstop_done)
do_notify_parent_cldstop(current, false, why);
__set_current_state(TASK_RUNNING);
if (clear_code)
current->exit_code = 0;
@ -1728,7 +1842,7 @@ void ptrace_notify(int exit_code)
/* Let the debugger run. */
spin_lock_irq(&current->sighand->siglock);
ptrace_stop(exit_code, 1, &info);
ptrace_stop(exit_code, CLD_TRAPPED, 1, &info);
spin_unlock_irq(&current->sighand->siglock);
}
@ -1741,66 +1855,115 @@ void ptrace_notify(int exit_code)
static int do_signal_stop(int signr)
{
struct signal_struct *sig = current->signal;
int notify;
if (!sig->group_stop_count) {
if (!(current->group_stop & GROUP_STOP_PENDING)) {
unsigned int gstop = GROUP_STOP_PENDING | GROUP_STOP_CONSUME;
struct task_struct *t;
if (!likely(sig->flags & SIGNAL_STOP_DEQUEUED) ||
/* signr will be recorded in task->group_stop for retries */
WARN_ON_ONCE(signr & ~GROUP_STOP_SIGMASK);
if (!likely(current->group_stop & GROUP_STOP_DEQUEUED) ||
unlikely(signal_group_exit(sig)))
return 0;
/*
* There is no group stop already in progress.
* We must initiate one now.
* There is no group stop already in progress. We must
* initiate one now.
*
* While ptraced, a task may be resumed while group stop is
* still in effect and then receive a stop signal and
* initiate another group stop. This deviates from the
* usual behavior as two consecutive stop signals can't
* cause two group stops when !ptraced. That is why we
* also check !task_is_stopped(t) below.
*
* The condition can be distinguished by testing whether
* SIGNAL_STOP_STOPPED is already set. Don't generate
* group_exit_code in such case.
*
* This is not necessary for SIGNAL_STOP_CONTINUED because
* an intervening stop signal is required to cause two
* continued events regardless of ptrace.
*/
sig->group_exit_code = signr;
if (!(sig->flags & SIGNAL_STOP_STOPPED))
sig->group_exit_code = signr;
else
WARN_ON_ONCE(!task_ptrace(current));
current->group_stop &= ~GROUP_STOP_SIGMASK;
current->group_stop |= signr | gstop;
sig->group_stop_count = 1;
for (t = next_thread(current); t != current; t = next_thread(t))
for (t = next_thread(current); t != current;
t = next_thread(t)) {
t->group_stop &= ~GROUP_STOP_SIGMASK;
/*
* Setting state to TASK_STOPPED for a group
* stop is always done with the siglock held,
* so this check has no races.
*/
if (!(t->flags & PF_EXITING) &&
!task_is_stopped_or_traced(t)) {
if (!(t->flags & PF_EXITING) && !task_is_stopped(t)) {
t->group_stop |= signr | gstop;
sig->group_stop_count++;
signal_wake_up(t, 0);
}
}
}
/*
* If there are no other threads in the group, or if there is
* a group stop in progress and we are the last to stop, report
* to the parent. When ptraced, every thread reports itself.
*/
notify = sig->group_stop_count == 1 ? CLD_STOPPED : 0;
notify = tracehook_notify_jctl(notify, CLD_STOPPED);
/*
* tracehook_notify_jctl() can drop and reacquire siglock, so
* we keep ->group_stop_count != 0 before the call. If SIGCONT
* or SIGKILL comes in between ->group_stop_count == 0.
*/
if (sig->group_stop_count) {
if (!--sig->group_stop_count)
sig->flags = SIGNAL_STOP_STOPPED;
current->exit_code = sig->group_exit_code;
retry:
if (likely(!task_ptrace(current))) {
int notify = 0;
/*
* If there are no other threads in the group, or if there
* is a group stop in progress and we are the last to stop,
* report to the parent.
*/
if (task_participate_group_stop(current))
notify = CLD_STOPPED;
__set_current_state(TASK_STOPPED);
spin_unlock_irq(&current->sighand->siglock);
/*
* Notify the parent of the group stop completion. Because
* we're not holding either the siglock or tasklist_lock
* here, ptracer may attach inbetween; however, this is for
* group stop and should always be delivered to the real
* parent of the group leader. The new ptracer will get
* its notification when this task transitions into
* TASK_TRACED.
*/
if (notify) {
read_lock(&tasklist_lock);
do_notify_parent_cldstop(current, false, notify);
read_unlock(&tasklist_lock);
}
/* Now we don't run again until woken by SIGCONT or SIGKILL */
schedule();
spin_lock_irq(&current->sighand->siglock);
} else {
ptrace_stop(current->group_stop & GROUP_STOP_SIGMASK,
CLD_STOPPED, 0, NULL);
current->exit_code = 0;
}
/*
* GROUP_STOP_PENDING could be set if another group stop has
* started since being woken up or ptrace wants us to transit
* between TASK_STOPPED and TRACED. Retry group stop.
*/
if (current->group_stop & GROUP_STOP_PENDING) {
WARN_ON_ONCE(!(current->group_stop & GROUP_STOP_SIGMASK));
goto retry;
}
/* PTRACE_ATTACH might have raced with task killing, clear trapping */
task_clear_group_stop_trapping(current);
spin_unlock_irq(&current->sighand->siglock);
if (notify) {
read_lock(&tasklist_lock);
do_notify_parent_cldstop(current, notify);
read_unlock(&tasklist_lock);
}
/* Now we don't run again until woken by SIGCONT or SIGKILL */
do {
schedule();
} while (try_to_freeze());
tracehook_finish_jctl();
current->exit_code = 0;
return 1;
}
@ -1814,7 +1977,7 @@ static int ptrace_signal(int signr, siginfo_t *info,
ptrace_signal_deliver(regs, cookie);
/* Let the debugger run. */
ptrace_stop(signr, 0, info);
ptrace_stop(signr, CLD_TRAPPED, 0, info);
/* We're back. Did the debugger cancel the sig? */
signr = current->exit_code;
@ -1869,18 +2032,36 @@ relock:
* the CLD_ si_code into SIGNAL_CLD_MASK bits.
*/
if (unlikely(signal->flags & SIGNAL_CLD_MASK)) {
int why = (signal->flags & SIGNAL_STOP_CONTINUED)
? CLD_CONTINUED : CLD_STOPPED;
struct task_struct *leader;
int why;
if (signal->flags & SIGNAL_CLD_CONTINUED)
why = CLD_CONTINUED;
else
why = CLD_STOPPED;
signal->flags &= ~SIGNAL_CLD_MASK;
why = tracehook_notify_jctl(why, CLD_CONTINUED);
spin_unlock_irq(&sighand->siglock);
if (why) {
read_lock(&tasklist_lock);
do_notify_parent_cldstop(current->group_leader, why);
read_unlock(&tasklist_lock);
}
/*
* Notify the parent that we're continuing. This event is
* always per-process and doesn't make whole lot of sense
* for ptracers, who shouldn't consume the state via
* wait(2) either, but, for backward compatibility, notify
* the ptracer of the group leader too unless it's gonna be
* a duplicate.
*/
read_lock(&tasklist_lock);
do_notify_parent_cldstop(current, false, why);
leader = current->group_leader;
if (task_ptrace(leader) && !real_parent_is_ptracer(leader))
do_notify_parent_cldstop(leader, true, why);
read_unlock(&tasklist_lock);
goto relock;
}
@ -1897,8 +2078,8 @@ relock:
if (unlikely(signr != 0))
ka = return_ka;
else {
if (unlikely(signal->group_stop_count > 0) &&
do_signal_stop(0))
if (unlikely(current->group_stop &
GROUP_STOP_PENDING) && do_signal_stop(0))
goto relock;
signr = dequeue_signal(current, &current->blocked,
@ -2045,17 +2226,19 @@ void exit_signals(struct task_struct *tsk)
if (!signal_pending(t) && !(t->flags & PF_EXITING))
recalc_sigpending_and_wake(t);
if (unlikely(tsk->signal->group_stop_count) &&
!--tsk->signal->group_stop_count) {
tsk->signal->flags = SIGNAL_STOP_STOPPED;
group_stop = tracehook_notify_jctl(CLD_STOPPED, CLD_STOPPED);
}
if (unlikely(tsk->group_stop & GROUP_STOP_PENDING) &&
task_participate_group_stop(tsk))
group_stop = CLD_STOPPED;
out:
spin_unlock_irq(&tsk->sighand->siglock);
/*
* If group stop has completed, deliver the notification. This
* should always go to the real parent of the group leader.
*/
if (unlikely(group_stop)) {
read_lock(&tasklist_lock);
do_notify_parent_cldstop(tsk, group_stop);
do_notify_parent_cldstop(tsk, false, group_stop);
read_unlock(&tasklist_lock);
}
}