xv6-65oo2/trap.c

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#include "types.h"
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#include "defs.h"
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#include "param.h"
#include "mmu.h"
#include "proc.h"
#include "x86.h"
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#include "traps.h"
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#include "spinlock.h"
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// Interrupt descriptor table (shared by all CPUs).
struct gatedesc idt[256];
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extern uint vectors[]; // in vectors.S: array of 256 entry pointers
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struct spinlock tickslock;
int ticks;
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void
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tvinit(void)
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{
int i;
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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);
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initlock(&tickslock, "time");
}
void
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idtinit(void)
{
lidt(idt, sizeof(idt));
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}
void
trap(struct trapframe *tf)
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{
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if(tf->trapno == T_SYSCALL){
if(cp->killed)
exit();
cp->tf = tf;
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syscall();
if(cp->killed)
exit();
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return;
}
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switch(tf->trapno){
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case IRQ_OFFSET + IRQ_TIMER:
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if(cpu() == 0){
acquire(&tickslock);
ticks++;
wakeup(&ticks);
release(&tickslock);
}
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lapic_eoi();
break;
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case IRQ_OFFSET + IRQ_IDE:
ide_intr();
lapic_eoi();
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break;
case IRQ_OFFSET + IRQ_KBD:
kbd_intr();
lapic_eoi();
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break;
case IRQ_OFFSET + IRQ_SPURIOUS:
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cprintf("cpu%d: spurious interrupt at %x:%x\n",
cpu(), tf->cs, tf->eip);
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lapic_eoi();
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break;
default:
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if(cp == 0 || (tf->cs&3) == 0){
// In kernel, it must be our mistake.
cprintf("unexpected trap %d from cpu %d eip %x\n",
tf->trapno, cpu(), tf->eip);
panic("trap");
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}
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// In user space, assume process misbehaved.
cprintf("pid %d %s: trap %d err %d on cpu %d eip %x -- kill proc\n",
cp->pid, cp->name, tf->trapno, tf->err, cpu(), tf->eip);
cp->killed = 1;
}
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// 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(cp && cp->killed && (tf->cs&3) == DPL_USER)
exit();
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// Force process to give up CPU on clock tick.
// If interrupts were on while locks held, would need to check nlock.
if(cp && cp->state == RUNNING && tf->trapno == IRQ_OFFSET+IRQ_TIMER)
yield();
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}