/*
 * Copyright 1993,1994,1995 Emin Gun Sirer
 * MIPSI - Mips Instruction Set Simulator.
 */

#include "MIPS/syscall-ultrix.h"
#include "config.h"
#include "main.h"
#include "syscalls.h"
#include "mem.h"


/*
 * decides which syscall it should do or simulate
 * returns non-zero to signal exit, zero for continue
 */
int dosyscall(void)
{
    void *buf;

    switch(R[REG_V0]) {
      case SYS_syscall:
	traceout("SYSCALL syscall\n");
	R[REG_V0] = R[REG_A0];
	R[REG_A0] = R[REG_A1];
	R[REG_A1] = R[REG_A2];
	R[REG_A2] = R[REG_A3];
	R[REG_A3] = rnr_mem_word(R[REG_SP]+16);
	dosyscall();
	break;
	
      case SYS_write:
	/* A special case so we can use printf without implementing any I/O in mt-os. */
	traceout("SYSCALL write(%d, 0x%x, %d)\n", R[REG_A0], R[REG_A1], R[REG_A2]);
	buf = galloc(R[REG_A2]);
	copy_to_buffer(buf, R[REG_A1], R[REG_A2]);
	R[REG_RES] = write(R[REG_A0], buf, R[REG_A2]);
	R[REG_ERR] = ((signed)R[REG_RES] < 0) ? -1 : 0;
	free(buf);
	break;

      case SYS_getpagesize:
	traceout("SYSCALL getpagesize() = 4096\n");
	R[REG_RES] = 4096;
	R[REG_ERR] = 0;
	break;
	
      case SYS_sbrk:
	traceout("SYSCALL sbrk(%d) = ", R[REG_A0]);
	expand_data(R[REG_A0]);
	R[REG_RES] = pbreak;
	pbreak += R[REG_A0];
	R[REG_ERR] = 0;
	traceout("0x%x\n", R[REG_RES]);
	break;
	
      case SYS_brk: {
	  unsigned long datatop = 0x10000000 + datasize;
	  traceout("SYSCALL brk(0x%x) = ", R[REG_A0]);
	  /* Round up to PGSZ boundary */
	  if((R[REG_A0] - datatop) > 0)
	      expand_data(ROUND(R[REG_A0], PGSZ) - datatop);
	  /*	
	   * if we get here, expand data must have been successful
	   */
	  R[REG_RES] = pbreak;
	  pbreak = ROUND(R[REG_A0], PGSZ);
	  R[REG_ERR] = 0;
	  traceout("0x%x\n", R[REG_RES]);
	  break;
      }

	
      case SYS_exit: {
	  /* A special case so programs can stop. */
	  traceout("SYSCALL _exit(%d)\n", R[REG_A0]);
	  return (R[REG_A0] & 0xff) + 256;
      }
      
      case SYS_MT_OS:
	R[REG_RES] = mt_syscall(R[REG_A0], R[REG_A1], 
				R[REG_A2], R[REG_A3]);
	break;

      default:
	error(Fatal, "Unimplemented system call: %d\n",R[REG_V0]);
	break;
    }
    
    return 0;
}