crt.S

.global crtStart
.global main
.global irqCallback

crtStart:
  j crtInit
  nop
  nop
  nop
  nop
  nop
  nop
  nop

.global  trap_entry
trap_entry:
  sw x1,  - 1*4(sp)
  sw x5,  - 2*4(sp)
  sw x6,  - 3*4(sp)
  sw x7,  - 4*4(sp)
  sw x10, - 5*4(sp)
  sw x11, - 6*4(sp)
  sw x12, - 7*4(sp)
  sw x13, - 8*4(sp)
  sw x14, - 9*4(sp)
  sw x15, -10*4(sp)
  sw x16, -11*4(sp)
  sw x17, -12*4(sp)
  sw x28, -13*4(sp)
  sw x29, -14*4(sp)
  sw x30, -15*4(sp)
  sw x31, -16*4(sp)
  addi sp,sp,-16*4
  call irqCallback
  lw x1 , 15*4(sp)
  lw x5,  14*4(sp)
  lw x6,  13*4(sp)
  lw x7,  12*4(sp)
  lw x10, 11*4(sp)
  lw x11, 10*4(sp)
  lw x12,  9*4(sp)
  lw x13,  8*4(sp)
  lw x14,  7*4(sp)
  lw x15,  6*4(sp)
  lw x16,  5*4(sp)
  lw x17,  4*4(sp)
  lw x28,  3*4(sp)
  lw x29,  2*4(sp)
  lw x30,  1*4(sp)
  lw x31,  0*4(sp)
  addi sp,sp,16*4
  mret
  .text


crtInit:
  .option push
  .option norelax
  la gp, __global_pointer$
  .option pop
  la sp, _stack_start

bss_init:
  la a0, _bss_start
  la a1, _bss_end
bss_loop:
  beq a0,a1,bss_done
  sw zero,0(a0)
  add a0,a0,4
  j bss_loop
bss_done:

ctors_init:
  la a0, _ctors_start
  addi sp,sp,-4
ctors_loop:
  la a1, _ctors_end
  beq a0,a1,ctors_done
  lw a3,0(a0)
  add a0,a0,4
  sw a0,0(sp)
  jalr  a3
  lw a0,0(sp)
  j ctors_loop
ctors_done:
  addi sp,sp,4


  li a0, 0x880     //880 enable timer + external interrupts
  csrw mie,a0
  li a0, 0x1808     //1808 enable interrupts
  csrw mstatus,a0

  call main
infinitLoop:
  j infinitLoop