trapasm.S

.text
.globl trap
.globl trapret1

.globl alltraps
alltraps:
  /* vectors.S sends all traps here */
  pushl   %ds      # build
  pushl   %es      #  trap
  pushal           #  frame
  movl $16,%eax    # SEG_KDATA << 3
  movw %ax,%ds     #  kernel
  movw %ax,%es     #  segments
  pushl %esp       # pass pointer to this trapframe
  call    trap     #  and call trap()
  addl $4, %esp
  # return falls through to trapret...

  /*
   * a forked process RETs here
   * expects ESP to point to a Trapframe
   */
.globl trapret
trapret:
  popal
  popl %es
  popl %ds
  addl $0x8, %esp /* trapno and errcode */
  iret

.globl forkret1
forkret1:
  movl 4(%esp), %esp
  jmp trapret