#pypp 0
// Iris: micro-kernel for a capability-based operating system.
// mips/interrupts.ccp: Functions called by mips/entry.S.
// Copyright 2009 Bas Wijnen <wijnen@debian.org>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

#define ARCH
#include "../kernel.hh"

/// A TLB miss has occurred.  This is the slow version.  It is only used
/// when k0 or k1 is not 0, or when an error occurs.
/// Otherwise, the ultra-fast code in entry.S is used.
Thread *tlb_refill ():
	//panic (0x88776655, "TLB refill")
	if !directory:
		panic (0x44449999, "No directory")
	unsigned EntryHi
	cp0_get (CP0_ENTRY_HI, EntryHi)
	unsigned *t = directory[EntryHi >> 21]
	if !t:
		unsigned a
		cp0_get (CP0_EPC, a)
		dbg_send (a)
		cp0_get (CP0_BAD_V_ADDR, a)
		dbg_send (a)
		panic (0x99992222, "No page table")
	// - 2 instead of - 1 means reset bit 0
	unsigned idx = (EntryHi >> 12) & ((1 << 9) - 2)
	cp0_set (CP0_ENTRY_LO0, t[idx])
	cp0_set (CP0_ENTRY_LO1, t[idx + 1])
	__asm__ volatile ("tlbwr")
	return current

/// An interrupt which is not an exception has occurred.
Thread *interrupt ():
	//panic (0x88877722, "Interrupt")
	//dbg_send (INTC_IPR)
	unsigned ipr = INTC_IPR
	for unsigned i = 0; i < 32; ++i:
		if ipr & (1 << i):
			// Handle timer interrupts specially: don't disable them.
			if i == IRQ_OST0:
				continue
			// Disable the interrupt while handling it.
			intc_mask_irq (i)
			intc_ack_irq (i)
			// Send message to interrupt handler.
			if arch_interrupt_receiver[i]:
				Capability::Context c
				for unsigned j = 0; j < 4; ++j:
					c.data[j] = 0
					c.cap[j] = NULL
					c.copy[j] = false
				arch_interrupt_receiver[i]->send_message (i, &c)
	if ipr & (1 << IRQ_OST0):
		ost_clear_uf (0)
		intc_ack_irq (IRQ_OST0)
		timer_interrupt ()
	return current

void flush_tlb (unsigned asid):
	for unsigned tlb = 1; tlb < 32; ++tlb:
		cp0_set (CP0_INDEX, tlb)
		__asm__ volatile ("tlbr")
		unsigned hi
		cp0_get (CP0_ENTRY_HI, hi)
		if (hi & 0x1f) == asid:
			// Set asid to 0, which is only used by the idle task.
			cp0_set (CP0_ENTRY_HI, 0x2000 * tlb)
			__asm__ volatile ("tlbwi")

static void arch_invoke ():
	Capability *target
	bool wait
	Thread *caller = current
	target = caller->address_space->find_capability (caller->arch.v0, &wait)
	if !target:
		// TODO: there must be no action here.  This is just because the rest doesn't work yet.
		dbg_send (3, 2)
		//dbg_send (caller->arch.v0)
		schedule ()
		// Calling an invalid capability always fails.
		caller->arch.v0 = 0
	else:
		if wait:
			caller->wait ()
		Capability::Context c
		c.cap[0] = caller->address_space->find_capability (caller->arch.a0, &c.copy[0])
		c.cap[1] = caller->address_space->find_capability (caller->arch.a1, &c.copy[1])
		c.cap[2] = caller->address_space->find_capability (caller->arch.a2, &c.copy[2])
		c.cap[3] = caller->address_space->find_capability (caller->arch.a3, &c.copy[3])
		c.data[0] = caller->arch.t0
		c.data[1] = caller->arch.t1
		c.data[2] = caller->arch.t2
		c.data[3] = caller->arch.t3
		caller->arch.v0 = target->invoke (&c) ? 1 : 0
	if caller != current && caller != &idle && (caller->flags & (THREAD_FLAG_RUNNING | THREAD_FLAG_WAITING)) == THREAD_FLAG_RUNNING:
		current = caller
	else if !current:
		schedule ()
		if !current:
			current = &idle
	if caller != current:
		if (Memory *)asids[current->address_space->arch.asid] != current->address_space:
			if asids[0]:
				current->address_space->arch.asid = asids[0]
				asids[0] = asids[asids[0]]
			else:
				static unsigned random = 1
				current->address_space->arch.asid = random
				// Overwrite used asid, so flush those values from tlb.
				flush_tlb (random)
				++random
				if random >= 64:
					random = 1
			asids[current->address_space->arch.asid] = (unsigned)current->address_space
		cp0_set (CP0_ENTRY_HI, current->address_space->arch.asid)
		directory = current->address_space->arch.directory
		unsigned status
		cp0_get (CP0_STATUS, status)
		status &= 0x0fffffff
		if current->flags & THREAD_FLAG_PRIV:
			status |= 0x10000000
		cp0_set (CP0_STATUS, status | 0x13)

/// A general exception has occurred.
Thread *exception ():
	unsigned cause
	cp0_get (CP0_CAUSE, cause)
	switch (cause >> 2) & 0x1f:
		case 0:
			// Interrupt.  This shouldn't happen, since CAUSE[IV] == 1.
			panic (0x11223344, "Interrupt on exception vector.")
		case 1:
			// TLB modification.
			panic (0x21223344, "TLB modification.")
		case 2:
			// TLB load or instruction fetch.
			unsigned a
			cp0_get (CP0_EPC, a)
			dbg_send (a)
			panic (0x31223344, "TLB load or instruction fetch.")
		case 3:
			// TLB store.
			panic (0x41223344, "TLB store.")
		case 4:
			// Address error load or instruction fetch.
			panic (0x51223344, "Address error load or instruction fetch.")
		case 5:
			// Address error store.
			unsigned a
			cp0_get (CP0_EPC, a)
			dbg_send (a, 16)
			panic (0x61223344, "Address error store.")
		case 6:
			// Bus error instruction fetch.
			panic (0x71223344, "Bus error instruction fetch.")
		case 7:
			// Bus error load or store.
			panic (0x81223344, "Bus error load or store.")
		case 8:
			// Syscall.
			current->pc += 4
			arch_invoke ()
			break
		case 9:
			// Breakpoint.
			panic (0x91223344, "Breakpoint.")
		case 10:
			// Reserved instruction.
			panic (0xa1223344, "Reserved instruction.")
		case 11:
			// Coprocessor unusable.
			panic (0xb1223344, "Coprocessor unusable.")
		case 12:
			// Arithmetic overflow.
			panic (0xc1223344, "Arithmetic overflow.")
		case 13:
			// Trap.
			panic (0xe1223344, "Trap.")
		case 15:
			// Floating point exception.
			panic (0xf1223344, "Floating point exception.")
		case 23:
			// Reference to WatchHi/WatchLo address.
			panic (0xf2223344, "Reference to WatchHi/WatchLo address.")
		case 24:
			// Machine check.
			panic (0xf3223344, "Machine check.")
		case 30:
			// Cache error (EJTAG only).
			panic (0xf4223344, "Cache error (EJTAG only).")
		case 14:
		case 16:
		case 17:
		case 18:
		case 19:
		case 20:
		case 21:
		case 22:
		case 25:
		case 26:
		case 27:
		case 28:
		case 29:
		case 31:
			// Reserved.
			panic (0xf5223344, "Reserved exception code")
		default:
			panic (0xf6223344, "Impossible exception code")
	return current

/// There's a cache error.  Big trouble.  Probably not worth trying to recover.
Thread *cache_error ():
	panic (0x33333333, "cache error")
	return current