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/*

 * main.c -- start the ball rolling

 */

#include "stdarg.h"

#include "start.h"

/**************************************************************/

unsigned char taskCode[] = {

  #include "task.dump"

};

/**************************************************************/

void putchar(char c) {

  unsigned int *base;

  if (c == '\n') {

    putchar('\r');

  }

  base = (unsigned int *) 0xF0300000;

  while ((*(base + 2) & 1) == 0) ;

  *(base + 3) = c;

}

void puts(char *s) {

  char c;

  while ((c = *s++) != '\0') {

    putchar(c);

  }

}

void printn(int n) {

  int a;

  if (n < 0) {

    putchar('-');

    n = -n;

  }

  a = n / 10;

  if (a != 0) {

    printn(a);

  }

  putchar(n % 10 + '0');

}

void printu(unsigned int n, unsigned int b) {

  unsigned int a;

  a = n / b;

  if (a != 0) {

    printu(a, b);

  }

  putchar("0123456789ABCDEF"[n % b]);

}

void printf(char *fmt, ...) {

  va_list ap;

  char c;

  int n;

  unsigned int u;

  char *s;

  va_start(ap, fmt);

  while (1) {

    while ((c = *fmt++) != '%') {

      if (c == '\0') {

        va_end(ap);

        return;

      }

      putchar(c);

    }

    c = *fmt++;

    if (c == 'd') {

      n = va_arg(ap, int);

      printn(n);

    } else

    if (c == 'u' || c == 'o' || c == 'x') {

      u = va_arg(ap, int);

      printu(u, c == 'o' ? 8 : (c == 'x' ? 16 : 10));

    } else

    if (c == 's') {

      s = va_arg(ap, char *);

      puts(s);

    } else {

      putchar(c);

    }

  }

}

/**************************************************************/

static char *exceptionCause[32] = {

  /* 00 */  "terminal 0 transmitter interrupt",

  /* 01 */  "terminal 0 receiver interrupt",

  /* 02 */  "terminal 1 transmitter interrupt",

  /* 03 */  "terminal 1 receiver interrupt",

  /* 04 */  "keyboard interrupt",

  /* 05 */  "unknown interrupt",

  /* 06 */  "unknown interrupt",

  /* 07 */  "unknown interrupt",

  /* 08 */  "disk interrupt",

  /* 09 */  "unknown interrupt",

  /* 10 */  "unknown interrupt",

  /* 11 */  "unknown interrupt",

  /* 12 */  "unknown interrupt",

  /* 13 */  "unknown interrupt",

  /* 14 */  "timer interrupt",

  /* 15 */  "unknown interrupt",

  /* 16 */  "bus timeout exception",

  /* 17 */  "illegal instruction exception",

  /* 18 */  "privileged instruction exception",

  /* 19 */  "divide instruction exception",

  /* 20 */  "trap instruction exception",

  /* 21 */  "TLB miss exception",

  /* 22 */  "TLB write exception",

  /* 23 */  "TLB invalid exception",

  /* 24 */  "illegal address exception",

  /* 25 */  "privileged address exception",

  /* 26 */  "unknown exception",

  /* 27 */  "unknown exception",

  /* 28 */  "unknown exception",

  /* 29 */  "unknown exception",

  /* 30 */  "unknown exception",

  /* 31 */  "unknown exception"

};

void defaultISR(int irq, unsigned int *registers) {

  printf("\n%s\n", exceptionCause[irq]);

}

void initInterrupts(void) {

  int i;

  for (i = 0; i < 32; i++) {

    setISR(i, defaultISR);

  }

}

/**************************************************************/

void loadTask(unsigned char *code,

              int csize, unsigned int physCodeAddr,

              int dsize, unsigned int physDataAddr,

              int bsize) {

  unsigned char *virtLoadAddr;

  int i;

  virtLoadAddr = (unsigned char *) (0xC0000000 | physCodeAddr);

  for (i = 0; i < csize; i++) {

    *virtLoadAddr++ = *code++;

  }

  virtLoadAddr = (unsigned char *) (0xC0000000 | physDataAddr);

  for (i = 0; i < dsize; i++) {

    *virtLoadAddr++ = *code++;

  }

  for (i = 0; i < bsize; i++) {

    *virtLoadAddr++ = '\0';

  }

}

/**************************************************************/

void trapISR(int irq, unsigned int *registers) {

  /* 'putchar' is the only system call yet */

  putchar(registers[4]);

  /* skip the trap instruction */

  registers[30] += 4;

}

/**************************************************************/

void flushTLB(void) {

  unsigned int invalPage;

  int i;

  invalPage = 0xC0000000;

  for (i = 0; i < 32; i++) {

    setTLB(i, invalPage, 0);

    invalPage += (1 << 12);

  }

}

/**************************************************************/

unsigned int getNumber(unsigned char *p) {

  return (unsigned int) *(p + 0) << 24 |

         (unsigned int) *(p + 1) << 16 |

         (unsigned int) *(p + 2) <<  8 |

         (unsigned int) *(p + 3) <<  0;

}

void main(void) {

  unsigned int magic;

  unsigned int csize;

  unsigned int dsize;

  unsigned int bsize;

  printf("\n");

  printf("OS: initializing interrupts\n");

  initInterrupts();

  setISR(20, trapISR);

  /* load code at 256 k, data at (256 + 16) k */

  printf("OS: loading task\n");

  magic = getNumber(taskCode + 0);

  csize = getNumber(taskCode + 4);

  dsize = getNumber(taskCode + 8);

  bsize = getNumber(taskCode + 12);

  if (magic != 0x1AA09232) {

    printf("Error: Load module is not executable!\n");

    while (1) ;

  }

  printf("(csize = 0x%x, dsize = 0x%x, bsize = 0x%x)\n",

         csize, dsize, bsize);

  loadTask(taskCode + 8 * sizeof(unsigned int),

           csize, 64 << 12,

           dsize, 68 << 12,

           bsize);

  printf("OS: presetting TLB\n");

  flushTLB();

  setTLB(5, 0x00000000, 64 << 12 | 0x01);

  setTLB(27, (csize + 0x00000FFF) & 0xFFFFF000, 68 << 12 | 0x03);

  setTLB(22, 0x7FFFF000, 80 << 12 | 0x03);

  printf("OS: starting task\n");

  startTask(80 << 12);  /* stack at (256 + 64) k */

}