trap.c

#include "types.h"
#include "defs.h"
#include "param.h"
#include "memlayout.h"
#include "mmu.h"
#include "proc.h"
#include "x86.h"
#include "traps.h"
#include "spinlock.h"

// Interrupt descriptor table (shared by all CPUs).
struct gatedesc idt[256];
extern uint vectors[];	// in vectors.S: array of 256 entry pointers
struct spinlock tickslock;
uint ticks;

void
tvinit(void)
{
	int i;

	for(i = 0; i < 256; i++)
		SETGATE(idt[i], 0, SEG_KCODE<<3, vectors[i], 0);
	SETGATE(idt[T_SYSCALL], 1, SEG_KCODE<<3, vectors[T_SYSCALL], DPL_USER);

	initlock(&tickslock, "time");
}

void
idtinit(void)
{
	lidt(idt, sizeof(idt));
}

//PAGEBREAK: 41
void
trap(struct trapframe *tf)
{
	if(tf->trapno == T_SYSCALL){
		if(myproc()->killed)
			exit();
		myproc()->tf = tf;
		syscall();
		if(myproc()->killed)
			exit();
		return;
	}

	switch(tf->trapno){
	case T_IRQ0 + IRQ_TIMER:
		if(cpuid() == 0){
			acquire(&tickslock);
			ticks++;
			wakeup(&ticks);
			release(&tickslock);
		}
		lapiceoi();
		break;
	case T_IRQ0 + IRQ_IDE:
		ideintr();
		lapiceoi();
		break;
	case T_IRQ0 + IRQ_IDE+1:
		// Bochs generates spurious IDE1 interrupts.
		break;
	case T_IRQ0 + IRQ_KBD:
		kbdintr();
		lapiceoi();
		break;
	case T_IRQ0 + IRQ_COM1:
		uartintr();
		lapiceoi();
		break;
	case T_IRQ0 + 7:
	case T_IRQ0 + IRQ_SPURIOUS:
		cprintf("cpu%d: spurious interrupt at %x:%x\n",
						cpuid(), tf->cs, tf->eip);
		lapiceoi();
		break;

	//PAGEBREAK: 13
	default:
		if(myproc() == 0 || (tf->cs&3) == 0){
			// In kernel, it must be our mistake.
			cprintf("unexpected trap %d from cpu %d eip %x (cr2=0x%x)\n",
							tf->trapno, cpuid(), tf->eip, rcr2());
			panic("trap");
		}
		// In user space, assume process misbehaved.
		cprintf("pid %d %s: trap %d err %d on cpu %d "
						"eip 0x%x addr 0x%x--kill proc\n",
						myproc()->pid, myproc()->name, tf->trapno,
						tf->err, cpuid(), tf->eip, rcr2());
		myproc()->killed = 1;
	}

	// Force process exit if it has been killed and is in user space.
	// (If it is still executing in the kernel, let it keep running
	// until it gets to the regular system call return.)
	if(myproc() && myproc()->killed && (tf->cs&3) == DPL_USER)
		exit();

	// Force process to give up CPU on clock tick.
	// If interrupts were on while locks held, would need to check nlock.
	if(myproc() && myproc()->state == RUNNING &&
		 tf->trapno == T_IRQ0+IRQ_TIMER)
		yield();

	// Check if the process has been killed since we yielded
	if(myproc() && myproc()->killed && (tf->cs&3) == DPL_USER)
		exit();
}