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).
uint *idt;
extern addr_t vectors[];  // in vectors.S: array of 256 entry pointers
struct spinlock tickslock;
uint ticks;

static void
mkgate(uint *idt, uint n, addr_t kva, uint pl)
{
  uint64 addr = (uint64) kva;

  n *= 4;
  idt[n+0] = (addr & 0xFFFF) | (KERNEL_CS << 16);
  idt[n+1] = (addr & 0xFFFF0000) | 0x8E00 | ((pl & 3) << 13);
  idt[n+2] = addr >> 32;
  idt[n+3] = 0;
}

void idtinit(void)
{
  lidt((void*) idt, PGSIZE);
}

void tvinit(void)
{
  int n;
  idt = (uint*) kalloc();
  memset(idt, 0, PGSIZE);

  for (n = 0; n < 256; n++)
    mkgate(idt, n, vectors[n], 0);
}

//PAGEBREAK: 41
void
trap(struct trapframe *tf)
{
  switch(tf->trapno){
  case T_IRQ0 + IRQ_TIMER:
    if(cpunum() == 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 %p:%p\n",
            cpunum(), tf->cs, tf->rip);
    lapiceoi();
    break;

  //PAGEBREAK: 13
  default:
    if(proc == 0 || (tf->cs&3) == 0){
      // In kernel, it must be our mistake.
      cprintf("unexpected trap %d from cpu %d rip %p (cr2=0x%p)\n",
              tf->trapno, cpunum(), tf->rip, rcr2());
      if (proc)
        cprintf("proc id: %d\n", proc->pid);
      panic("trap");
    }
    // In user space, assume process misbehaved.
    cprintf("pid %d %s: trap %d err %d on cpu %d "
            "rip 0x%p addr 0x%p--kill proc\n",
            proc->pid, proc->name, tf->trapno, tf->err, cpunum(), tf->rip,
            rcr2());
    proc->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(proc && proc->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(proc && proc->state == RUNNING && tf->trapno == T_IRQ0+IRQ_TIMER)
    yield();

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