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Turn the syscall interrupt into a trap (by switching the gate type.)

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This leaves interrupts enabled while we're in the kernel, which is
precisely what we want.

This uncovered a horrendous problem with kernel tasks silently
overflowing their stacks. For now I've simply increased the stack size
but I need a more MMU-y solution for this eventually.
This commit is contained in:
Andreas Kling 2018-10-19 11:28:43 +02:00
parent 2d1d01661b
commit 46ff281695
6 changed files with 116 additions and 25 deletions
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16
Kernel/Task.cpp
View file

@ -162,13 +162,14 @@ Task::Task(void (*e)(), const char* n, IPC::Handle h, RingLevel ring)
kprintf("basically ready\n");
// NOTE: Each task gets 4KB of stack.
static const DWORD defaultStackSize = 4096;
// NOTE: Each task gets 16KB of stack.
static const DWORD defaultStackSize = 16384;
if (isRing0()) {
// FIXME: This memory is leaked.
// But uh, there's also no kernel task termination, so I guess it's not technically leaked...
m_stackTop = ((DWORD)kmalloc(defaultStackSize) + defaultStackSize) & 0xffffff8;
dword stackBottom = (dword)kmalloc(defaultStackSize);
m_stackTop = (stackBottom + defaultStackSize) & 0xffffff8;
m_tss.esp = m_stackTop;
} else {
auto* region = allocateRegion(defaultStackSize, "stack");
@ -235,8 +236,8 @@ void Task::dumpRegions()
void Task::taskDidCrash(Task* crashedTask)
{
// NOTE: This is called from an excepton handler, so interrupts are disabled.
crashedTask->setState(Crashing);
crashedTask->dumpRegions();
s_tasks->remove(crashedTask);
@ -260,8 +261,11 @@ void yield()
//kprintf("%s<%u> yield()\n", current->name().characters(), current->pid());
if (!scheduleNewTask())
cli();
if (!scheduleNewTask()) {
sti();
return;
}
//kprintf("yield() jumping to new task: %x (%s)\n", current->farPtr().selector, current->name().characters());
switchNow();
@ -272,7 +276,7 @@ void switchNow()
Descriptor& descriptor = getGDTEntry(current->selector());
descriptor.type = 9;
flushGDT();
asm(
asm("sti\n"
"ljmp *(%%eax)\n"
::"a"(&current->farPtr())
);