xv6-cs450/trap.c

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#include "types.h"
#include "param.h"
#include "mmu.h"
#include "proc.h"
#include "defs.h"
#include "x86.h"
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#include "traps.h"
#include "syscall.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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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);
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SETGATE(idt[T_SYSCALL], 0, SEG_KCODE << 3, vectors[T_SYSCALL], DPL_USER);
}
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)
proc_exit();
cp->tf = tf;
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syscall();
if(cp->killed)
proc_exit();
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return;
}
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// PAGEBREAK: 10
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// Increment nlock to make sure interrupts stay off
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// during interrupt handler. Decrement before returning.
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cpus[cpu()].nlock++;
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switch(tf->trapno){
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case IRQ_OFFSET + IRQ_TIMER:
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lapic_timerintr();
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cpus[cpu()].nlock--;
if(cp){
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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.)
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if((tf->cs&3) == DPL_USER && cp->killed)
proc_exit();
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// Force process to give up CPU and let others run.
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// If locks were held with interrupts on, would need to check nlock.
if(cp->state == RUNNING)
yield();
}
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return;
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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("spurious interrupt from cpu %d eip %x\n", cpu(), tf->eip);
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break;
default:
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if(cp) {
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// Assume process divided by zero or dereferenced null, etc.
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cprintf("pid %d %s: unhandled trap %d on cpu %d eip %x -- kill proc\n",
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cp->pid, cp->name, tf->trapno, cpu(), tf->eip);
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proc_exit();
}
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// Otherwise it's our mistake.
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cprintf("unexpected trap %d from cpu %d eip %x\n",
tf->trapno, cpu(), tf->eip);
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panic("trap");
}
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cpus[cpu()].nlock--;
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}