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Kernel: Move signal handlers from being thread state to process state

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POSIX requires that sigaction() and friends set a _process-wide_ signal
handler, so move signal handlers and flags inside Process.
This also fixes a "pid/tid confusion" FIXME, as we can now send the
signal to the process and let that decide which thread should get the
signal (which is the thread with tid==pid, but that's now the Process's
problem).
Note that each thread still retains its signal mask, as that is local to
each thread.
This commit is contained in:
Ali Mohammad Pur 2022-02-24 22:25:49 +03:30 • committed by Andreas Kling
parent 18b9d02edd
commit cf63447044
5 changed files with 19 additions and 19 deletions
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7
Kernel/Process.cpp
View file

@ -612,10 +612,9 @@ void Process::finalize()
m_state.store(State::Dead, AK::MemoryOrder::memory_order_release);
{
// FIXME: PID/TID BUG
if (auto parent_thread = Thread::from_tid(ppid().value())) {
if (parent_thread->process().is_user_process() && (parent_thread->m_signal_action_data[SIGCHLD].flags & SA_NOCLDWAIT) != SA_NOCLDWAIT)
parent_thread->send_signal(SIGCHLD, this);
if (auto parent_process = Process::from_pid(ppid())) {
if (parent_process->is_user_process() && (parent_process->m_signal_action_data[SIGCHLD].flags & SA_NOCLDWAIT) != SA_NOCLDWAIT)
(void)parent_process->send_signal(SIGCHLD, this);
}
}

6
Kernel/Process.h
View file

@ -827,6 +827,12 @@ private:
NonnullRefPtrVector<Thread> m_threads_for_coredump;
mutable RefPtr<ProcessProcFSTraits> m_procfs_traits;
struct SignalActionData {
VirtualAddress handler_or_sigaction;
int flags { 0 };
u32 mask { 0 };
};
Array<SignalActionData, NSIG> m_signal_action_data;
static_assert(sizeof(ProtectedValues) < (PAGE_SIZE));
alignas(4096) ProtectedValues m_protected_values;

4
Kernel/Syscalls/sigaction.cpp
View file

@ -58,15 +58,17 @@ ErrorOr<FlatPtr> Process::sys$sigaction(int signum, Userspace<const sigaction*>
return EINVAL;
InterruptDisabler disabler; // FIXME: This should use a narrower lock. Maybe a way to ignore signals temporarily?
auto& action = Thread::current()->m_signal_action_data[signum];
auto& action = m_signal_action_data[signum];
if (user_old_act) {
sigaction old_act {};
old_act.sa_flags = action.flags;
old_act.sa_sigaction = reinterpret_cast<decltype(old_act.sa_sigaction)>(action.handler_or_sigaction.as_ptr());
old_act.sa_mask = action.mask;
TRY(copy_to_user(user_old_act, &old_act));
}
if (user_act) {
auto act = TRY(copy_typed_from_user(user_act));
action.mask = act.sa_mask;
action.flags = act.sa_flags;
action.handler_or_sigaction = VirtualAddress { reinterpret_cast<void*>(act.sa_sigaction) };
}

13
Kernel/Thread.cpp
View file

@ -790,7 +790,7 @@ void Thread::reset_signals_for_exec()
// The signal mask is preserved across execve(2).
// The pending signal set is preserved across an execve(2).
m_have_any_unmasked_pending_signals.store(false, AK::memory_order_release);
m_signal_action_data.fill({});
m_signal_action_masks.fill({});
// A successful call to execve(2) removes any existing alternate signal stack
m_alternative_signal_stack = 0;
m_alternative_signal_stack_size = 0;
@ -902,7 +902,7 @@ static DefaultSignalAction default_signal_action(u8 signal)
bool Thread::should_ignore_signal(u8 signal) const
{
VERIFY(signal < 32);
auto const& action = m_signal_action_data[signal];
auto const& action = m_process->m_signal_action_data[signal];
if (action.handler_or_sigaction.is_null())
return default_signal_action(signal) == DefaultSignalAction::Ignore;
return ((sighandler_t)action.handler_or_sigaction.get() == SIG_IGN);
@ -911,7 +911,7 @@ bool Thread::should_ignore_signal(u8 signal) const
bool Thread::has_signal_handler(u8 signal) const
{
VERIFY(signal < 32);
auto const& action = m_signal_action_data[signal];
auto const& action = m_process->m_signal_action_data[signal];
return !action.handler_or_sigaction.is_null();
}
@ -975,7 +975,7 @@ DispatchSignalResult Thread::dispatch_signal(u8 signal)
return DispatchSignalResult::Deferred;
}
auto& action = m_signal_action_data[signal];
auto& action = m_process->m_signal_action_data[signal];
// FIXME: Implement SA_SIGINFO signal handlers.
VERIFY(!(action.flags & SA_SIGINFO));
@ -1045,7 +1045,7 @@ DispatchSignalResult Thread::dispatch_signal(u8 signal)
ScopedAddressSpaceSwitcher switcher(m_process);
u32 old_signal_mask = m_signal_mask;
u32 new_signal_mask = action.mask;
u32 new_signal_mask = m_signal_action_masks[signal].value_or(action.mask);
if ((action.flags & SA_NODEFER) == SA_NODEFER)
new_signal_mask &= ~(1 << (signal - 1));
else
@ -1182,8 +1182,7 @@ RegisterState& Thread::get_register_dump_from_stack()
ErrorOr<NonnullRefPtr<Thread>> Thread::try_clone(Process& process)
{
auto clone = TRY(Thread::try_create(process));
auto signal_action_data_span = m_signal_action_data.span();
signal_action_data_span.copy_to(clone->m_signal_action_data.span());
m_signal_action_masks.span().copy_to(clone->m_signal_action_masks);
clone->m_signal_mask = m_signal_mask;
clone->m_fpu_state = m_fpu_state;
clone->m_thread_specific_data = m_thread_specific_data;

8
Kernel/Thread.h
View file

@ -46,12 +46,6 @@ enum class DispatchSignalResult {
Continue
};
struct SignalActionData {
VirtualAddress handler_or_sigaction;
u32 mask { 0 };
int flags { 0 };
};
struct ThreadSpecificData {
ThreadSpecificData* self;
};
@ -1225,7 +1219,7 @@ private:
NonnullOwnPtr<Memory::Region> m_kernel_stack_region;
VirtualAddress m_thread_specific_data;
Optional<Memory::VirtualRange> m_thread_specific_range;
Array<SignalActionData, NSIG> m_signal_action_data;
Array<Optional<u32>, NSIG> m_signal_action_masks;
Blocker* m_blocker { nullptr };
Kernel::Mutex* m_blocking_mutex { nullptr };
u32 m_lock_requested_count { 0 };