lindows/lcrash/irq.c

#include <lcrash/irq.h>

#include <lcrash/util.h>
#include <lcrash/debug/debug.h>

#define PICMCMD 0x0020
#define PICMDAT 0x0021
#define PICSCMD 0x00A0
#define PICSDAT 0x00A1

struct IrqHandlerGate {
	/// Gate number
	u8 GateNumber;

	/// Hooks
	struct IrqHandlerHook* Hooks;
};

struct [[gnu::packed]] IrqHandlerDescriptor {
	u16 Offset0;
	u16 Segment;
	u16 Flags;
	u16 Offset1;
	u32 Offset2;
	u32 Reserved;
};

struct [[gnu::packed]] IrqHandlerIDTR {
	u16 Length;
	struct IrqHandlerDescriptor* Offset;
};

struct IrqHandlerInterruptFrame {
	u64 PrevInstructionAddress;
	u64 PrevInstructionSegment;
	u64 PrevFlags;
	u64 PrevStackAddress;
	u64 PrevStackSegment;
};

struct IrqHandlerGate IrqHandlerGates[256] = {};

[[gnu::aligned(16)]]
struct IrqHandlerDescriptor IrqHandlerDescriptors[256] = {};

/// Check for spurious IRQs
bool IrqHandlerCheckRealIRQ(u64 Interrupt) {
	if (Interrupt == 0x27) {
		PortWrite8(PICMCMD, 0x0B); // RDISR
		if (PortRead8(PICMDAT) & 0x80) return false;
	}

	if (Interrupt >= 0x28 && Interrupt <= 0x2f) {
		PortWrite8(PICSCMD, 0x0B); // RDISR
		if (PortRead8(PICSDAT) & 0x80) {
			PortWrite8(PICMCMD, 0x20);
			return false;
		}
	}

	return true;
}

/// Send an EOI to the PIC
void IrqHandlerSendEOI(u64 Interrupt) {
	if (Interrupt >= 0x20 && Interrupt < 0x30) {
		if (Interrupt >= 0x28) PortWrite8(PICSCMD, 0x20); // EOI
		PortWrite8(PICMCMD, 0x20); // EOI
	}
}

/// Handle an interrupt
[[gnu::target("general-regs-only")]]
void IrqHandlerHandleInterrupt(struct IrqHandlerInterruptFrame* Frame, u64 Interrupt) {
	// Panic("Got interrupt");
	
	IrqHandlerSendEOI(Interrupt);

	return;
}

/// Handle an exception
[[gnu::target("general-regs-only")]]
void IrqHandlerHandleException(struct IrqHandlerInterruptFrame* Frame, u64 ErrorCode, u64 Interrupt) {
	//Panic("Got exception");

	IrqHandlerSendEOI(Interrupt);

	return;
}

s32 IrqHandlerInitialize() {
	extern int   IrqHandlerISRTable;
	void*        ISRTable = &IrqHandlerISRTable;
	
	// Table stating if an interrupt is an error or not
	bool Error[256] = {
		0, 0, 0, 0, 0, 0, 0, 0,
		1, 0, 1, 1, 1, 1, 1, 0,
		0, 1, 0, 0, 0, 1, 0, 0,
		0, 0, 0, 0, 0, 1, 1, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0,
	};

	// Fill IDT
	for (int i = 0; i < 256; i++) {
		u64 Offset = (u64)ISRTable;
		
		IrqHandlerDescriptors[i].Segment = 0x10; // TODO: This shouldnt be hardcoded
		IrqHandlerDescriptors[i].Flags   = Error[i] ? 0x8F00 : 0x8E00;
		IrqHandlerDescriptors[i].Offset0 =  Offset        & 0xffff;
		IrqHandlerDescriptors[i].Offset1 = (Offset >> 16) & 0xffff;
		IrqHandlerDescriptors[i].Offset2 =  Offset >> 32  & 0xffffffff;

		ISRTable += 0x20;
	}

	// Load the IDT
	struct IrqHandlerIDTR IDTR;
	IDTR.Offset = IrqHandlerDescriptors;
	IDTR.Length = 256 * 16 - 1;
	asm ("lidt %0" :: "m" (IDTR));

	// Drop to assembly and do a long jump to get our IRQ's working  
	asm ("call IrqHandlerApplyStateChange");
	
	// TODO: Disable APIC until APIC support is added

	// Reconfigure legacy PIC (TODO: Switch to APIC)
	PortWrite8(PICMCMD, 0x11); // Initialize / cascade
	PortWrite8(PICSCMD, 0x11); 
	PortWrite8(PICMDAT, 0x20); // Map master PIC IRQs to 0x20-0x27
	PortWrite8(PICSDAT, 0x28); // Map slave  PIC IRQS to 0x28-0x2f
	PortWrite8(PICMDAT, 0x04); // Slave at IRQ2
	PortWrite8(PICSDAT, 0x02); // Slave ID 2
	PortWrite8(PICMDAT, 0x01); // Switch to 8086 mode
	PortWrite8(PICSDAT, 0x01);
	PortWrite8(PICMDAT, 0x01); // Respect all external interrupts except the PIC timer because its fucking stupid
	PortWrite8(PICSDAT, 0x00);

	return 0;
}

void IrqHandlerEnableInterrupts() { asm ("sti"); }
void IrqHandlerDisableInterrupts() { asm ("cli"); }

s32 IrqHandlerAttach(u8 Gate, struct IrqHandlerHook* Hook) {
	return -1;
}

s32 IrqHandlerDetach(struct IrqHandlerHook* Hook) {
	return -1;
}