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Kernel: Track previous mode when entering/exiting traps

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This allows us to determine what the previous mode (user or kernel)
was, e.g. in the timer interrupt. This is used e.g. to determine
whether a signal handler should be set up.

Fixes #5096
This commit is contained in:
Tom 2021-01-25 13:19:34 -07:00 • committed by Andreas Kling
parent fa18010477
commit 0bd558081e
6 changed files with 70 additions and 7 deletions
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16
Kernel/Scheduler.cpp
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@ -369,10 +369,12 @@ bool Scheduler::context_switch(Thread* thread)
ASSERT(thread == Thread::current());
#if ARCH(I386)
auto iopl = get_iopl_from_eflags(Thread::current()->get_register_dump_from_stack().eflags);
if (thread->process().is_user_process() && iopl != 0) {
dbgln("PANIC: Switched to thread {} with non-zero IOPL={}", Thread::current()->tid().value(), iopl);
Processor::halt();
if (thread->process().is_user_process()) {
auto iopl = get_iopl_from_eflags(Thread::current()->get_register_dump_from_stack().eflags);
if (iopl != 0) {
dbgln("PANIC: Switched to thread {} with non-zero IOPL={}", Thread::current()->tid().value(), iopl);
Processor::halt();
}
}
#endif
@ -392,7 +394,7 @@ void Scheduler::enter_current(Thread& prev_thread, bool is_first)
// Check if we have any signals we should deliver (even if we don't
// end up switching to another thread).
auto current_thread = Thread::current();
if (!current_thread->is_in_block()) {
if (!current_thread->is_in_block() && current_thread->previous_mode() != Thread::PreviousMode::KernelMode) {
ScopedSpinLock lock(current_thread->get_lock());
if (current_thread->state() == Thread::Running && current_thread->pending_signals_for_state()) {
current_thread->dispatch_one_pending_signal();
@ -485,6 +487,10 @@ void Scheduler::timer_tick(const RegisterState& regs)
if (!current_thread)
return;
// Sanity checks
ASSERT(current_thread->current_trap());
ASSERT(current_thread->current_trap()->regs == &regs);
bool is_bsp = Processor::current().id() == 0;
if (!is_bsp)
return; // TODO: This prevents scheduling on other CPUs!