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ladybird/Kernel/Thread.cpp
Hediadyoin1 d12e14fa95 Userland: Respect red-zone for signal handlers 
We were building with red-zone before, but were not accounting for it on
signal handler entries. This should fix that.

Also shorten the stack alignment calculations for this.
2021-07-03 13:20:04 +02:00

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/*
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Demangle.h>
#include <AK/ScopeGuard.h>
#include <AK/StringBuilder.h>
#include <AK/Time.h>
#include <Kernel/Arch/x86/SmapDisabler.h>
#include <Kernel/Arch/x86/TrapFrame.h>
#include <Kernel/Debug.h>
#include <Kernel/FileSystem/FileDescription.h>
#include <Kernel/KSyms.h>
#include <Kernel/Panic.h>
#include <Kernel/PerformanceEventBuffer.h>
#include <Kernel/Process.h>
#include <Kernel/ProcessExposed.h>
#include <Kernel/Scheduler.h>
#include <Kernel/Sections.h>
#include <Kernel/Thread.h>
#include <Kernel/ThreadTracer.h>
#include <Kernel/TimerQueue.h>
#include <Kernel/VM/MemoryManager.h>
#include <Kernel/VM/PageDirectory.h>
#include <Kernel/VM/ProcessPagingScope.h>
#include <LibC/signal_numbers.h>
namespace Kernel {
SpinLock<u8> Thread::g_tid_map_lock;
READONLY_AFTER_INIT HashMap<ThreadID, Thread*>* Thread::g_tid_map;
UNMAP_AFTER_INIT void Thread::initialize()
{
g_tid_map = new HashMap<ThreadID, Thread*>();
}
KResultOr<NonnullRefPtr<Thread>> Thread::try_create(NonnullRefPtr<Process> process)
{
// FIXME: Once we have aligned + nothrow operator new, we can avoid the manual kfree.
FPUState* fpu_state = (FPUState*)kmalloc_aligned<16>(sizeof(FPUState));
if (!fpu_state)
return ENOMEM;
ArmedScopeGuard fpu_guard([fpu_state]() { kfree_aligned(fpu_state); });
auto kernel_stack_region = MM.allocate_kernel_region(default_kernel_stack_size, {}, Region::Access::Read | Region::Access::Write, AllocationStrategy::AllocateNow);
if (!kernel_stack_region)
return ENOMEM;
kernel_stack_region->set_stack(true);
auto block_timer = AK::try_create<Timer>();
if (!block_timer)
return ENOMEM;
auto thread = adopt_ref_if_nonnull(new (nothrow) Thread(move(process), kernel_stack_region.release_nonnull(), block_timer.release_nonnull(), fpu_state));
if (!thread)
return ENOMEM;
fpu_guard.disarm();
return thread.release_nonnull();
}
Thread::Thread(NonnullRefPtr<Process> process, NonnullOwnPtr<Region> kernel_stack_region, NonnullRefPtr<Timer> block_timer, FPUState* fpu_state)
: m_process(move(process))
, m_kernel_stack_region(move(kernel_stack_region))
, m_fpu_state(fpu_state)
, m_name(m_process->name())
, m_block_timer(block_timer)
, m_global_procfs_inode_index(ProcFSComponentsRegistrar::the().allocate_inode_index())
{
bool is_first_thread = m_process->add_thread(*this);
if (is_first_thread) {
// First thread gets TID == PID
m_tid = m_process->pid().value();
} else {
m_tid = Process::allocate_pid().value();
}
{
// FIXME: Go directly to KString
auto string = String::formatted("Kernel stack (thread {})", m_tid.value());
m_kernel_stack_region->set_name(KString::try_create(string));
}
{
ScopedSpinLock lock(g_tid_map_lock);
auto result = g_tid_map->set(m_tid, this);
VERIFY(result == AK::HashSetResult::InsertedNewEntry);
}
if constexpr (THREAD_DEBUG)
dbgln("Created new thread {}({}:{})", m_process->name(), m_process->pid().value(), m_tid.value());
reset_fpu_state();
#if ARCH(I386)
// Only IF is set when a process boots.
m_regs.eflags = 0x0202;
if (m_process->is_kernel_process()) {
m_regs.cs = GDT_SELECTOR_CODE0;
m_regs.ds = GDT_SELECTOR_DATA0;
m_regs.es = GDT_SELECTOR_DATA0;
m_regs.fs = 0;
m_regs.ss = GDT_SELECTOR_DATA0;
m_regs.gs = GDT_SELECTOR_PROC;
} else {
m_regs.cs = GDT_SELECTOR_CODE3 | 3;
m_regs.ds = GDT_SELECTOR_DATA3 | 3;
m_regs.es = GDT_SELECTOR_DATA3 | 3;
m_regs.fs = GDT_SELECTOR_DATA3 | 3;
m_regs.ss = GDT_SELECTOR_DATA3 | 3;
m_regs.gs = GDT_SELECTOR_TLS | 3;
}
#else
// Only IF is set when a process boots.
m_regs.rflags = 0x0202;
if (m_process->is_kernel_process())
m_regs.cs = GDT_SELECTOR_CODE0;
else
m_regs.cs = GDT_SELECTOR_CODE3 | 3;
#endif
m_regs.cr3 = m_process->space().page_directory().cr3();
m_kernel_stack_base = m_kernel_stack_region->vaddr().get();
m_kernel_stack_top = m_kernel_stack_region->vaddr().offset(default_kernel_stack_size).get() & 0xfffffff8u;
if (m_process->is_kernel_process()) {
#if ARCH(I386)
m_regs.esp = m_regs.esp0 = m_kernel_stack_top;
#else
m_regs.rsp = m_regs.rsp0 = m_kernel_stack_top;
#endif
} else {
// Ring 3 processes get a separate stack for ring 0.
// The ring 3 stack will be assigned by exec().
#if ARCH(I386)
m_regs.ss0 = GDT_SELECTOR_DATA0;
m_regs.esp0 = m_kernel_stack_top;
#else
m_regs.rsp0 = m_kernel_stack_top;
#endif
}
// We need to add another reference if we could successfully create
// all the resources needed for this thread. The reason for this is that
// we don't want to delete this thread after dropping the reference,
// it may still be running or scheduled to be run.
// The finalizer is responsible for dropping this reference once this
// thread is ready to be cleaned up.
ref();
}
Thread::~Thread()
{
{
// We need to explicitly remove ourselves from the thread list
// here. We may get pre-empted in the middle of destructing this
// thread, which causes problems if the thread list is iterated.
// Specifically, if this is the last thread of a process, checking
// block conditions would access m_process, which would be in
// the middle of being destroyed.
ScopedSpinLock lock(g_scheduler_lock);
VERIFY(!m_process_thread_list_node.is_in_list());
// We shouldn't be queued
VERIFY(m_runnable_priority < 0);
}
{
ScopedSpinLock lock(g_tid_map_lock);
auto result = g_tid_map->remove(m_tid);
VERIFY(result);
}
}
void Thread::unblock_from_blocker(Blocker& blocker)
{
auto do_unblock = [&]() {
ScopedSpinLock scheduler_lock(g_scheduler_lock);
ScopedSpinLock block_lock(m_block_lock);
if (m_blocker != &blocker)
return;
if (!should_be_stopped() && !is_stopped())
unblock();
};
if (Processor::current().in_irq()) {
Processor::current().deferred_call_queue([do_unblock = move(do_unblock), self = make_weak_ptr()]() {
if (auto this_thread = self.strong_ref())
do_unblock();
});
} else {
do_unblock();
}
}
void Thread::unblock(u8 signal)
{
VERIFY(!Processor::current().in_irq());
VERIFY(g_scheduler_lock.own_lock());
VERIFY(m_block_lock.own_lock());
if (m_state != Thread::Blocked)
return;
VERIFY(m_blocker);
if (signal != 0) {
if (is_handling_page_fault()) {
// Don't let signals unblock threads that are blocked inside a page fault handler.
// This prevents threads from EINTR'ing the inode read in an inode page fault.
// FIXME: There's probably a better way to solve this.
return;
}
if (!m_blocker->can_be_interrupted() && !m_should_die)
return;
m_blocker->set_interrupted_by_signal(signal);
}
m_blocker = nullptr;
if (Thread::current() == this) {
set_state(Thread::Running);
return;
}
VERIFY(m_state != Thread::Runnable && m_state != Thread::Running);
set_state(Thread::Runnable);
}
void Thread::set_should_die()
{
if (m_should_die) {
dbgln("{} Should already die", *this);
return;
}
ScopedCritical critical;
// Remember that we should die instead of returning to
// the userspace.
ScopedSpinLock lock(g_scheduler_lock);
m_should_die = true;
// NOTE: Even the current thread can technically be in "Stopped"
// state! This is the case when another thread sent a SIGSTOP to
// it while it was running and it calls e.g. exit() before
// the scheduler gets involved again.
if (is_stopped()) {
// If we were stopped, we need to briefly resume so that
// the kernel stacks can clean up. We won't ever return back
// to user mode, though
VERIFY(!process().is_stopped());
resume_from_stopped();
}
if (is_blocked()) {
ScopedSpinLock block_lock(m_block_lock);
if (m_blocker) {
// We're blocked in the kernel.
m_blocker->set_interrupted_by_death();
unblock();
}
}
}
void Thread::die_if_needed()
{
VERIFY(Thread::current() == this);
if (!m_should_die)
return;
u32 unlock_count;
[[maybe_unused]] auto rc = unlock_process_if_locked(unlock_count);
dbgln_if(THREAD_DEBUG, "Thread {} is dying", *this);
{
ScopedSpinLock lock(g_scheduler_lock);
// It's possible that we don't reach the code after this block if the
// scheduler is invoked and FinalizerTask cleans up this thread, however
// that doesn't matter because we're trying to invoke the scheduler anyway
set_state(Thread::Dying);
}
ScopedCritical critical;
// Flag a context switch. Because we're in a critical section,
// Scheduler::yield will actually only mark a pending context switch
// Simply leaving the critical section would not necessarily trigger
// a switch.
Scheduler::yield();
// Now leave the critical section so that we can also trigger the
// actual context switch
u32 prev_flags;
Processor::current().clear_critical(prev_flags, false);
dbgln("die_if_needed returned from clear_critical!!! in irq: {}", Processor::current().in_irq());
// We should never get here, but the scoped scheduler lock
// will be released by Scheduler::context_switch again
VERIFY_NOT_REACHED();
}
void Thread::exit(void* exit_value)
{
VERIFY(Thread::current() == this);
m_join_condition.thread_did_exit(exit_value);
set_should_die();
u32 unlock_count;
[[maybe_unused]] auto rc = unlock_process_if_locked(unlock_count);
if (m_thread_specific_range.has_value()) {
auto* region = process().space().find_region_from_range(m_thread_specific_range.value());
VERIFY(region);
if (!process().space().deallocate_region(*region))
dbgln("Failed to unmap TLS range, exiting thread anyway.");
}
die_if_needed();
}
void Thread::yield_while_not_holding_big_lock()
{
VERIFY(!g_scheduler_lock.own_lock());
u32 prev_flags;
u32 prev_crit = Processor::current().clear_critical(prev_flags, true);
Scheduler::yield();
// NOTE: We may be on a different CPU now!
Processor::current().restore_critical(prev_crit, prev_flags);
}
void Thread::yield_without_holding_big_lock()
{
VERIFY(!g_scheduler_lock.own_lock());
u32 lock_count_to_restore = 0;
auto previous_locked = unlock_process_if_locked(lock_count_to_restore);
// NOTE: Even though we call Scheduler::yield here, unless we happen
// to be outside of a critical section, the yield will be postponed
// until leaving it in relock_process.
Scheduler::yield();
relock_process(previous_locked, lock_count_to_restore);
}
void Thread::donate_without_holding_big_lock(RefPtr<Thread>& thread, const char* reason)
{
VERIFY(!g_scheduler_lock.own_lock());
u32 lock_count_to_restore = 0;
auto previous_locked = unlock_process_if_locked(lock_count_to_restore);
// NOTE: Even though we call Scheduler::yield here, unless we happen
// to be outside of a critical section, the yield will be postponed
// until leaving it in relock_process.
Scheduler::donate_to(thread, reason);
relock_process(previous_locked, lock_count_to_restore);
}
LockMode Thread::unlock_process_if_locked(u32& lock_count_to_restore)
{
return process().big_lock().force_unlock_if_locked(lock_count_to_restore);
}
void Thread::relock_process(LockMode previous_locked, u32 lock_count_to_restore)
{
// Clearing the critical section may trigger the context switch
// flagged by calling Scheduler::donate_to or Scheduler::yield
// above. We have to do it this way because we intentionally
// leave the critical section here to be able to switch contexts.
u32 prev_flags;
u32 prev_crit = Processor::current().clear_critical(prev_flags, true);
// CONTEXT SWITCH HAPPENS HERE!
// NOTE: We may be on a different CPU now!
Processor::current().restore_critical(prev_crit, prev_flags);
if (previous_locked != LockMode::Unlocked) {
// We've unblocked, relock the process if needed and carry on.
process().big_lock().restore_lock(previous_locked, lock_count_to_restore);
}
}
auto Thread::sleep(clockid_t clock_id, const Time& duration, Time* remaining_time) -> BlockResult
{
VERIFY(state() == Thread::Running);
return Thread::current()->block<Thread::SleepBlocker>({}, Thread::BlockTimeout(false, &duration, nullptr, clock_id), remaining_time);
}
auto Thread::sleep_until(clockid_t clock_id, const Time& deadline) -> BlockResult
{
VERIFY(state() == Thread::Running);
return Thread::current()->block<Thread::SleepBlocker>({}, Thread::BlockTimeout(true, &deadline, nullptr, clock_id));
}
const char* Thread::state_string() const
{
switch (state()) {
case Thread::Invalid:
return "Invalid";
case Thread::Runnable:
return "Runnable";
case Thread::Running:
return "Running";
case Thread::Dying:
return "Dying";
case Thread::Dead:
return "Dead";
case Thread::Stopped:
return "Stopped";
case Thread::Blocked: {
ScopedSpinLock block_lock(m_block_lock);
VERIFY(m_blocker != nullptr);
return m_blocker->state_string();
}
}
PANIC("Thread::state_string(): Invalid state: {}", (int)state());
}
void Thread::finalize()
{
VERIFY(Thread::current() == g_finalizer);
VERIFY(Thread::current() != this);
#if LOCK_DEBUG
VERIFY(!m_lock.own_lock());
if (lock_count() > 0) {
dbgln("Thread {} leaking {} Locks!", *this, lock_count());
ScopedSpinLock list_lock(m_holding_locks_lock);
for (auto& info : m_holding_locks_list) {
const auto& location = info.source_location;
dbgln(" - Lock: \"{}\" @ {} locked in function \"{}\" at \"{}:{}\" with a count of: {}", info.lock->name(), info.lock, location.function_name(), location.filename(), location.line_number(), info.count);
}
VERIFY_NOT_REACHED();
}
#endif
{
ScopedSpinLock lock(g_scheduler_lock);
dbgln_if(THREAD_DEBUG, "Finalizing thread {}", *this);
set_state(Thread::State::Dead);
m_join_condition.thread_finalizing();
}
if (m_dump_backtrace_on_finalization)
dbgln("{}", backtrace());
kfree_aligned(m_fpu_state);
drop_thread_count(false);
}
void Thread::drop_thread_count(bool initializing_first_thread)
{
bool is_last = process().remove_thread(*this);
if (!initializing_first_thread && is_last)
process().finalize();
}
void Thread::finalize_dying_threads()
{
VERIFY(Thread::current() == g_finalizer);
Vector<Thread*, 32> dying_threads;
{
ScopedSpinLock lock(g_scheduler_lock);
for_each_in_state(Thread::State::Dying, [&](Thread& thread) {
if (thread.is_finalizable())
dying_threads.append(&thread);
});
}
for (auto* thread : dying_threads) {
RefPtr<Process> process = thread->process();
dbgln_if(PROCESS_DEBUG, "Before finalization, {} has {} refs and its process has {}",
*thread, thread->ref_count(), thread->process().ref_count());
thread->finalize();
dbgln_if(PROCESS_DEBUG, "After finalization, {} has {} refs and its process has {}",
*thread, thread->ref_count(), thread->process().ref_count());
// This thread will never execute again, drop the running reference
// NOTE: This may not necessarily drop the last reference if anything
// else is still holding onto this thread!
thread->unref();
}
}
bool Thread::tick()
{
if (previous_mode() == PreviousMode::KernelMode) {
++m_process->m_ticks_in_kernel;
++m_ticks_in_kernel;
} else {
++m_process->m_ticks_in_user;
++m_ticks_in_user;
}
return --m_ticks_left;
}
void Thread::check_dispatch_pending_signal()
{
auto result = DispatchSignalResult::Continue;
{
ScopedSpinLock scheduler_lock(g_scheduler_lock);
if (pending_signals_for_state()) {
ScopedSpinLock lock(m_lock);
result = dispatch_one_pending_signal();
}
}
switch (result) {
case DispatchSignalResult::Yield:
yield_while_not_holding_big_lock();
break;
default:
break;
}
}
u32 Thread::pending_signals() const
{
ScopedSpinLock lock(g_scheduler_lock);
return pending_signals_for_state();
}
u32 Thread::pending_signals_for_state() const
{
VERIFY(g_scheduler_lock.own_lock());
constexpr u32 stopped_signal_mask = (1 << (SIGCONT - 1)) | (1 << (SIGKILL - 1)) | (1 << (SIGTRAP - 1));
if (is_handling_page_fault())
return 0;
return m_state != Stopped ? m_pending_signals : m_pending_signals & stopped_signal_mask;
}
void Thread::send_signal(u8 signal, [[maybe_unused]] Process* sender)
{
VERIFY(signal < 32);
ScopedSpinLock scheduler_lock(g_scheduler_lock);
// FIXME: Figure out what to do for masked signals. Should we also ignore them here?
if (should_ignore_signal(signal)) {
dbgln_if(SIGNAL_DEBUG, "Signal {} was ignored by {}", signal, process());
return;
}
if constexpr (SIGNAL_DEBUG) {
if (sender)
dbgln("Signal: {} sent {} to {}", *sender, signal, process());
else
dbgln("Signal: Kernel send {} to {}", signal, process());
}
m_pending_signals |= 1 << (signal - 1);
m_have_any_unmasked_pending_signals.store(pending_signals_for_state() & ~m_signal_mask, AK::memory_order_release);
if (m_state == Stopped) {
ScopedSpinLock lock(m_lock);
if (pending_signals_for_state()) {
dbgln_if(SIGNAL_DEBUG, "Signal: Resuming stopped {} to deliver signal {}", *this, signal);
resume_from_stopped();
}
} else {
ScopedSpinLock block_lock(m_block_lock);
dbgln_if(SIGNAL_DEBUG, "Signal: Unblocking {} to deliver signal {}", *this, signal);
unblock(signal);
}
}
u32 Thread::update_signal_mask(u32 signal_mask)
{
ScopedSpinLock lock(g_scheduler_lock);
auto previous_signal_mask = m_signal_mask;
m_signal_mask = signal_mask;
m_have_any_unmasked_pending_signals.store(pending_signals_for_state() & ~m_signal_mask, AK::memory_order_release);
return previous_signal_mask;
}
u32 Thread::signal_mask() const
{
ScopedSpinLock lock(g_scheduler_lock);
return m_signal_mask;
}
u32 Thread::signal_mask_block(sigset_t signal_set, bool block)
{
ScopedSpinLock lock(g_scheduler_lock);
auto previous_signal_mask = m_signal_mask;
if (block)
m_signal_mask &= ~signal_set;
else
m_signal_mask |= signal_set;
m_have_any_unmasked_pending_signals.store(pending_signals_for_state() & ~m_signal_mask, AK::memory_order_release);
return previous_signal_mask;
}
void Thread::clear_signals()
{
ScopedSpinLock lock(g_scheduler_lock);
m_signal_mask = 0;
m_pending_signals = 0;
m_have_any_unmasked_pending_signals.store(false, AK::memory_order_release);
m_signal_action_data.fill({});
}
// Certain exceptions, such as SIGSEGV and SIGILL, put a
// thread into a state where the signal handler must be
// invoked immediately, otherwise it will continue to fault.
// This function should be used in an exception handler to
// ensure that when the thread resumes, it's executing in
// the appropriate signal handler.
void Thread::send_urgent_signal_to_self(u8 signal)
{
VERIFY(Thread::current() == this);
DispatchSignalResult result;
{
ScopedSpinLock lock(g_scheduler_lock);
result = dispatch_signal(signal);
}
if (result == DispatchSignalResult::Yield)
yield_without_holding_big_lock();
}
DispatchSignalResult Thread::dispatch_one_pending_signal()
{
VERIFY(m_lock.own_lock());
u32 signal_candidates = pending_signals_for_state() & ~m_signal_mask;
if (signal_candidates == 0)
return DispatchSignalResult::Continue;
u8 signal = 1;
for (; signal < 32; ++signal) {
if (signal_candidates & (1 << (signal - 1))) {
break;
}
}
return dispatch_signal(signal);
}
DispatchSignalResult Thread::try_dispatch_one_pending_signal(u8 signal)
{
VERIFY(signal != 0);
ScopedSpinLock scheduler_lock(g_scheduler_lock);
ScopedSpinLock lock(m_lock);
u32 signal_candidates = pending_signals_for_state() & ~m_signal_mask;
if (!(signal_candidates & (1 << (signal - 1))))
return DispatchSignalResult::Continue;
return dispatch_signal(signal);
}
enum class DefaultSignalAction {
Terminate,
Ignore,
DumpCore,
Stop,
Continue,
};
static DefaultSignalAction default_signal_action(u8 signal)
{
VERIFY(signal && signal < NSIG);
switch (signal) {
case SIGHUP:
case SIGINT:
case SIGKILL:
case SIGPIPE:
case SIGALRM:
case SIGUSR1:
case SIGUSR2:
case SIGVTALRM:
case SIGSTKFLT:
case SIGIO:
case SIGPROF:
case SIGTERM:
return DefaultSignalAction::Terminate;
case SIGCHLD:
case SIGURG:
case SIGWINCH:
case SIGINFO:
return DefaultSignalAction::Ignore;
case SIGQUIT:
case SIGILL:
case SIGTRAP:
case SIGABRT:
case SIGBUS:
case SIGFPE:
case SIGSEGV:
case SIGXCPU:
case SIGXFSZ:
case SIGSYS:
return DefaultSignalAction::DumpCore;
case SIGCONT:
return DefaultSignalAction::Continue;
case SIGSTOP:
case SIGTSTP:
case SIGTTIN:
case SIGTTOU:
return DefaultSignalAction::Stop;
}
VERIFY_NOT_REACHED();
}
bool Thread::should_ignore_signal(u8 signal) const
{
VERIFY(signal < 32);
auto& action = m_signal_action_data[signal];
if (action.handler_or_sigaction.is_null())
return default_signal_action(signal) == DefaultSignalAction::Ignore;
if (action.handler_or_sigaction.as_ptr() == SIG_IGN)
return true;
return false;
}
bool Thread::has_signal_handler(u8 signal) const
{
VERIFY(signal < 32);
auto& action = m_signal_action_data[signal];
return !action.handler_or_sigaction.is_null();
}
static bool push_value_on_user_stack(FlatPtr* stack, FlatPtr data)
{
*stack -= sizeof(FlatPtr);
return copy_to_user((FlatPtr*)*stack, &data);
}
void Thread::resume_from_stopped()
{
VERIFY(is_stopped());
VERIFY(m_stop_state != State::Invalid);
VERIFY(g_scheduler_lock.own_lock());
if (m_stop_state == Blocked) {
ScopedSpinLock block_lock(m_block_lock);
if (m_blocker) {
// Hasn't been unblocked yet
set_state(Blocked, 0);
} else {
// Was unblocked while stopped
set_state(Runnable);
}
} else {
set_state(m_stop_state, 0);
}
}
DispatchSignalResult Thread::dispatch_signal(u8 signal)
{
VERIFY_INTERRUPTS_DISABLED();
VERIFY(g_scheduler_lock.own_lock());
VERIFY(signal > 0 && signal <= 32);
VERIFY(process().is_user_process());
VERIFY(this == Thread::current());
dbgln_if(SIGNAL_DEBUG, "Dispatch signal {} to {}, state: {}", signal, *this, state_string());
if (m_state == Invalid || !is_initialized()) {
// Thread has barely been created, we need to wait until it is
// at least in Runnable state and is_initialized() returns true,
// which indicates that it is fully set up an we actually have
// a register state on the stack that we can modify
return DispatchSignalResult::Deferred;
}
VERIFY(previous_mode() == PreviousMode::UserMode);
auto& action = m_signal_action_data[signal];
// FIXME: Implement SA_SIGINFO signal handlers.
VERIFY(!(action.flags & SA_SIGINFO));
// Mark this signal as handled.
m_pending_signals &= ~(1 << (signal - 1));
m_have_any_unmasked_pending_signals.store(m_pending_signals & ~m_signal_mask, AK::memory_order_release);
auto& process = this->process();
auto tracer = process.tracer();
if (signal == SIGSTOP || (tracer && default_signal_action(signal) == DefaultSignalAction::DumpCore)) {
dbgln_if(SIGNAL_DEBUG, "Signal {} stopping this thread", signal);
set_state(State::Stopped, signal);
return DispatchSignalResult::Yield;
}
if (signal == SIGCONT) {
dbgln("signal: SIGCONT resuming {}", *this);
} else {
if (tracer) {
// when a thread is traced, it should be stopped whenever it receives a signal
// the tracer is notified of this by using waitpid()
// only "pending signals" from the tracer are sent to the tracee
if (!tracer->has_pending_signal(signal)) {
dbgln("signal: {} stopping {} for tracer", signal, *this);
set_state(Stopped, signal);
return DispatchSignalResult::Yield;
}
tracer->unset_signal(signal);
}
}
auto handler_vaddr = action.handler_or_sigaction;
if (handler_vaddr.is_null()) {
switch (default_signal_action(signal)) {
case DefaultSignalAction::Stop:
set_state(Stopped, signal);
return DispatchSignalResult::Yield;
case DefaultSignalAction::DumpCore:
process.set_dump_core(true);
process.for_each_thread([](auto& thread) {
thread.set_dump_backtrace_on_finalization();
});
[[fallthrough]];
case DefaultSignalAction::Terminate:
m_process->terminate_due_to_signal(signal);
return DispatchSignalResult::Terminate;
case DefaultSignalAction::Ignore:
VERIFY_NOT_REACHED();
case DefaultSignalAction::Continue:
return DispatchSignalResult::Continue;
}
VERIFY_NOT_REACHED();
}
if (handler_vaddr.as_ptr() == SIG_IGN) {
dbgln_if(SIGNAL_DEBUG, "Ignored signal {}", signal);
return DispatchSignalResult::Continue;
}
VERIFY(previous_mode() == PreviousMode::UserMode);
VERIFY(current_trap());
ProcessPagingScope paging_scope(m_process);
u32 old_signal_mask = m_signal_mask;
u32 new_signal_mask = action.mask;
if (action.flags & SA_NODEFER)
new_signal_mask &= ~(1 << (signal - 1));
else
new_signal_mask |= 1 << (signal - 1);
m_signal_mask |= new_signal_mask;
m_have_any_unmasked_pending_signals.store(m_pending_signals & ~m_signal_mask, AK::memory_order_release);
auto setup_stack = [&](RegisterState& state) {
#if ARCH(I386)
FlatPtr* stack = &state.userspace_esp;
FlatPtr old_esp = *stack;
FlatPtr ret_eip = state.eip;
FlatPtr ret_eflags = state.eflags;
dbgln_if(SIGNAL_DEBUG, "Setting up user stack to return to EIP {:p}, ESP {:p}", ret_eip, old_esp);
#elif ARCH(X86_64)
FlatPtr* stack = &state.userspace_rsp;
FlatPtr old_rsp = *stack;
FlatPtr ret_rip = state.rip;
FlatPtr ret_rflags = state.rflags;
dbgln_if(SIGNAL_DEBUG, "Setting up user stack to return to RIP {:p}, RSP {:p}", ret_rip, old_rsp);
#endif
#if ARCH(I386)
// Align the stack to 16 bytes.
// Note that we push 56 bytes (4 * 14) on to the stack,
// so we need to account for this here.
// 56 % 16 = 8, so we only need to take 8 bytes into consideration for
// the stack alignment.
FlatPtr stack_alignment = (*stack - 8) % 16;
*stack -= stack_alignment;
push_value_on_user_stack(stack, ret_eflags);
push_value_on_user_stack(stack, ret_eip);
push_value_on_user_stack(stack, state.eax);
push_value_on_user_stack(stack, state.ecx);
push_value_on_user_stack(stack, state.edx);
push_value_on_user_stack(stack, state.ebx);
push_value_on_user_stack(stack, old_esp);
push_value_on_user_stack(stack, state.ebp);
push_value_on_user_stack(stack, state.esi);
push_value_on_user_stack(stack, state.edi);
#else
// Align the stack to 16 bytes.
// Note that we push 176 bytes (8 * 22) on to the stack,
// so we need to account for this here.
// 22 % 2 = 0, so we dont need to take anything into consideration
// for the alignment.
// We also are not allowed to touch the thread's red-zone of 128 bytes
FlatPtr stack_alignment = *stack % 16;
*stack -= 128 + stack_alignment;
push_value_on_user_stack(stack, ret_rflags);
push_value_on_user_stack(stack, ret_rip);
push_value_on_user_stack(stack, state.r15);
push_value_on_user_stack(stack, state.r14);
push_value_on_user_stack(stack, state.r13);
push_value_on_user_stack(stack, state.r12);
push_value_on_user_stack(stack, state.r11);
push_value_on_user_stack(stack, state.r10);
push_value_on_user_stack(stack, state.r9);
push_value_on_user_stack(stack, state.r8);
push_value_on_user_stack(stack, state.rax);
push_value_on_user_stack(stack, state.rcx);
push_value_on_user_stack(stack, state.rdx);
push_value_on_user_stack(stack, state.rbx);
push_value_on_user_stack(stack, old_rsp);
push_value_on_user_stack(stack, state.rbp);
push_value_on_user_stack(stack, state.rsi);
push_value_on_user_stack(stack, state.rdi);
#endif
// PUSH old_signal_mask
push_value_on_user_stack(stack, old_signal_mask);
push_value_on_user_stack(stack, signal);
push_value_on_user_stack(stack, handler_vaddr.get());
push_value_on_user_stack(stack, 0); //push fake return address
VERIFY((*stack % 16) == 0);
};
// We now place the thread state on the userspace stack.
// Note that we use a RegisterState.
// Conversely, when the thread isn't blocking the RegisterState may not be
// valid (fork, exec etc) but the tss will, so we use that instead.
auto& regs = get_register_dump_from_stack();
setup_stack(regs);
auto signal_trampoline_addr = process.signal_trampoline().get();
#if ARCH(I386)
regs.eip = signal_trampoline_addr;
#else
regs.rip = signal_trampoline_addr;
#endif
#if ARCH(I386)
dbgln_if(SIGNAL_DEBUG, "Thread in state '{}' has been primed with signal handler {:04x}:{:08x} to deliver {}", state_string(), m_regs.cs, m_regs.eip, signal);
#else
dbgln_if(SIGNAL_DEBUG, "Thread in state '{}' has been primed with signal handler {:04x}:{:16x} to deliver {}", state_string(), m_regs.cs, m_regs.rip, signal);
#endif
return DispatchSignalResult::Continue;
}
RegisterState& Thread::get_register_dump_from_stack()
{
auto* trap = current_trap();
// We should *always* have a trap. If we don't we're probably a kernel
// thread that hasn't been pre-empted. If we want to support this, we
// need to capture the registers probably into m_regs and return it
VERIFY(trap);
while (trap) {
if (!trap->next_trap)
break;
trap = trap->next_trap;
}
return *trap->regs;
}
RefPtr<Thread> Thread::clone(Process& process)
{
auto thread_or_error = Thread::try_create(process);
if (thread_or_error.is_error())
return {};
auto& clone = thread_or_error.value();
auto signal_action_data_span = m_signal_action_data.span();
signal_action_data_span.copy_to(clone->m_signal_action_data.span());
clone->m_signal_mask = m_signal_mask;
memcpy(clone->m_fpu_state, m_fpu_state, sizeof(FPUState));
clone->m_thread_specific_data = m_thread_specific_data;
return clone;
}
void Thread::set_state(State new_state, u8 stop_signal)
{
State previous_state;
VERIFY(g_scheduler_lock.own_lock());
if (new_state == m_state)
return;
{
ScopedSpinLock thread_lock(m_lock);
previous_state = m_state;
if (previous_state == Invalid) {
// If we were *just* created, we may have already pending signals
if (has_unmasked_pending_signals()) {
dbgln_if(THREAD_DEBUG, "Dispatch pending signals to new thread {}", *this);
dispatch_one_pending_signal();
}
}
m_state = new_state;
dbgln_if(THREAD_DEBUG, "Set thread {} state to {}", *this, state_string());
}
if (previous_state == Runnable) {
Scheduler::dequeue_runnable_thread(*this);
} else if (previous_state == Stopped) {
m_stop_state = State::Invalid;
auto& process = this->process();
if (process.set_stopped(false) == true) {
process.for_each_thread([&](auto& thread) {
if (&thread == this)
return;
if (!thread.is_stopped())
return;
dbgln_if(THREAD_DEBUG, "Resuming peer thread {}", thread);
thread.resume_from_stopped();
});
process.unblock_waiters(Thread::WaitBlocker::UnblockFlags::Continued);
// Tell the parent process (if any) about this change.
if (auto parent = Process::from_pid(process.ppid())) {
[[maybe_unused]] auto result = parent->send_signal(SIGCHLD, &process);
}
}
}
if (m_state == Runnable) {
Scheduler::queue_runnable_thread(*this);
Processor::smp_wake_n_idle_processors(1);
} else if (m_state == Stopped) {
// We don't want to restore to Running state, only Runnable!
m_stop_state = previous_state != Running ? previous_state : Runnable;
auto& process = this->process();
if (process.set_stopped(true) == false) {
process.for_each_thread([&](auto& thread) {
if (&thread == this)
return;
if (thread.is_stopped())
return;
dbgln_if(THREAD_DEBUG, "Stopping peer thread {}", thread);
thread.set_state(Stopped, stop_signal);
});
process.unblock_waiters(Thread::WaitBlocker::UnblockFlags::Stopped, stop_signal);
// Tell the parent process (if any) about this change.
if (auto parent = Process::from_pid(process.ppid())) {
[[maybe_unused]] auto result = parent->send_signal(SIGCHLD, &process);
}
}
} else if (m_state == Dying) {
VERIFY(previous_state != Blocked);
if (this != Thread::current() && is_finalizable()) {
// Some other thread set this thread to Dying, notify the
// finalizer right away as it can be cleaned up now
Scheduler::notify_finalizer();
}
}
}
struct RecognizedSymbol {
FlatPtr address;
const KernelSymbol* symbol { nullptr };
};
static bool symbolicate(const RecognizedSymbol& symbol, const Process& process, StringBuilder& builder)
{
if (!symbol.address)
return false;
bool mask_kernel_addresses = !process.is_superuser();
if (!symbol.symbol) {
if (!is_user_address(VirtualAddress(symbol.address))) {
builder.append("0xdeadc0de\n");
} else {
builder.appendff("{:p}\n", symbol.address);
}
return true;
}
unsigned offset = symbol.address - symbol.symbol->address;
if (symbol.symbol->address == g_highest_kernel_symbol_address && offset > 4096) {
builder.appendff("{:p}\n", (void*)(mask_kernel_addresses ? 0xdeadc0de : symbol.address));
} else {
builder.appendff("{:p} {} +{}\n", (void*)(mask_kernel_addresses ? 0xdeadc0de : symbol.address), demangle(symbol.symbol->name), offset);
}
return true;
}
String Thread::backtrace()
{
Vector<RecognizedSymbol, 128> recognized_symbols;
auto& process = const_cast<Process&>(this->process());
auto stack_trace = Processor::capture_stack_trace(*this);
VERIFY(!g_scheduler_lock.own_lock());
ProcessPagingScope paging_scope(process);
for (auto& frame : stack_trace) {
if (is_user_range(VirtualAddress(frame), sizeof(FlatPtr) * 2)) {
recognized_symbols.append({ frame });
} else {
recognized_symbols.append({ frame, symbolicate_kernel_address(frame) });
}
}
StringBuilder builder;
for (auto& symbol : recognized_symbols) {
if (!symbolicate(symbol, process, builder))
break;
}
return builder.to_string();
}
size_t Thread::thread_specific_region_alignment() const
{
return max(process().m_master_tls_alignment, alignof(ThreadSpecificData));
}
size_t Thread::thread_specific_region_size() const
{
return align_up_to(process().m_master_tls_size, thread_specific_region_alignment()) + sizeof(ThreadSpecificData);
}
KResult Thread::make_thread_specific_region(Badge<Process>)
{
// The process may not require a TLS region, or allocate TLS later with sys$allocate_tls (which is what dynamically loaded programs do)
if (!process().m_master_tls_region)
return KSuccess;
auto range = process().space().allocate_range({}, thread_specific_region_size());
if (!range.has_value())
return ENOMEM;
auto region_or_error = process().space().allocate_region(range.value(), "Thread-specific", PROT_READ | PROT_WRITE);
if (region_or_error.is_error())
return region_or_error.error();
m_thread_specific_range = range.value();
SmapDisabler disabler;
auto* thread_specific_data = (ThreadSpecificData*)region_or_error.value()->vaddr().offset(align_up_to(process().m_master_tls_size, thread_specific_region_alignment())).as_ptr();
auto* thread_local_storage = (u8*)((u8*)thread_specific_data) - align_up_to(process().m_master_tls_size, process().m_master_tls_alignment);
m_thread_specific_data = VirtualAddress(thread_specific_data);
thread_specific_data->self = thread_specific_data;
if (process().m_master_tls_size)
memcpy(thread_local_storage, process().m_master_tls_region.unsafe_ptr()->vaddr().as_ptr(), process().m_master_tls_size);
return KSuccess;
}
RefPtr<Thread> Thread::from_tid(ThreadID tid)
{
RefPtr<Thread> found_thread;
{
ScopedSpinLock lock(g_tid_map_lock);
if (auto it = g_tid_map->find(tid); it != g_tid_map->end()) {
// We need to call try_ref() here as there is a window between
// dropping the last reference and calling the Thread's destructor!
// We shouldn't remove the threads from that list until it is truly
// destructed as it may stick around past finalization in order to
// be able to wait() on it!
if (it->value->try_ref()) {
found_thread = adopt_ref(*it->value);
}
}
}
return found_thread;
}
void Thread::reset_fpu_state()
{
memcpy(m_fpu_state, &Processor::current().clean_fpu_state(), sizeof(FPUState));
}
bool Thread::should_be_stopped() const
{
return process().is_stopped();
}
}
void AK::Formatter<Kernel::Thread>::format(FormatBuilder& builder, const Kernel::Thread& value)
{
return AK::Formatter<FormatString>::format(
builder,
"{}({}:{})", value.process().name(), value.pid().value(), value.tid().value());
}
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