ossc/software/sys_controller/crt0.boot.S

// Copyright 2017 ETH Zurich and University of Bologna.
// Copyright and related rights are licensed under the Solderpad Hardware
// License, Version 0.51 (the “License”); you may not use this file except in
// compliance with the License.  You may obtain a copy of the License at
// http://solderpad.org/licenses/SHL-0.51. Unless required by applicable law
// or agreed to in writing, software, hardware and materials distributed under
// this License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR
// CONDITIONS OF ANY KIND, either express or implied. See the License for the
// specific language governing permissions and limitations under the License.

#include "pulpino.h"

#define EXCEPTION_STACK_SIZE 72


/* ========================================================= [ entry ] === */
  .section .text

default_exc_handler:
  jal x0, default_exc_handler

reset_handler:
  /* set all registers to zero */
  mv  x1, x0
  mv  x2, x1
  mv  x3, x1
  mv  x4, x1
  mv  x5, x1
  mv  x6, x1
  mv  x7, x1
  mv  x8, x1
  mv  x9, x1
  mv x10, x1
  mv x11, x1
  mv x12, x1
  mv x13, x1
  mv x14, x1
  mv x15, x1
  mv x16, x1
  mv x17, x1
  mv x18, x1
  mv x19, x1
  mv x20, x1
  mv x21, x1
  mv x22, x1
  mv x23, x1
  mv x24, x1
  mv x25, x1
  mv x26, x1
  mv x27, x1
  mv x28, x1
  mv x29, x1
  mv x30, x1
  mv x31, x1

  /* stack initilization */
  la   x2, _stack_start

_start:
  .global _start

  /* clear BSS */
  la x26, _bss_start
  la x27, _bss_end

  bge x26, x27, zero_loop_end

zero_loop:
  sw x0, 0(x26)
  addi x26, x26, 4
  ble x26, x27, zero_loop
zero_loop_end:


main_entry:
  /* jump to alt_main program entry point */
  jal alt_main

/* =================================================== [ exceptions ] === */
/* This section has to be down here, since we have to disable rvc for it  */

  .section .vectors, "ax"
  .option norvc;

  // external interrupts are handled by the same callback
  // until compiler supports IRQ routines
  .org 0x00
  .rept 31
  nop
  .endr
  jal x0, default_exc_handler

  // reset vector
  .org 0x80
  jal x0, reset_handler

  // illegal instruction exception
  .org 0x84
  jal x0, default_exc_handler

  // ecall handler
  .org 0x88
  jal x0, default_exc_handler