simple_os/b_by_bootloader.c at master · descent/simple_os · GitHub

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/*
 * let bootloader load to memory
 */
asm(".code16gcc\n");

typedef unsigned char u8;
typedef unsigned int u32;

int i;
char* itoa(int n, char* str);

void print(const char   *s)
{
  while(*s)
  {
    __asm__ __volatile__ ("int  $0x10" : : "a"(0x0E00 | *s), "b"(7));
    s++;
  }
}

#define DATA

const int A = 10;
#ifdef DATA
char data_str[]="data_string";
#endif

void write_mem8(u32 addr, u8 data); // assembly function.

int p()
{
  write_mem8(0x4, 'Z'); // assembly function.
#if 0
  int c=i+1;
  char arr[10]="a";
  char *s = arr;
#endif
#if 0
  char stack_str[]="stack_string"; // need %ds = %ss
  print("\r\n");
  print(stack_str);
#endif
#if 0
  const char *ro_str="ro_string"; // movl $0x000002f0, %ss:-4(%ebp)
  print("\r\n");
  print(ro_str);
#endif

#ifdef DATA
  print("\r\n");
  print(data_str);
#endif

#if 0
  static char *s_str="static_point";
  static char s_str_a[]="static_array";
  print("\r\n");
  print(s_str);
  print("\r\n");
  print(s_str_a);
#endif

  //const char *str="test";
  //volatile u8 *video_addr = (u8*)0xB8000;
  //asm("movw $0xb000 %gs");
  //*video_addr = 'a';
#if 0
  s = itoa(c, s); // need %ds to 0
  print("\r\n");
  print(s);
  return c;
#else
  return 1;
#endif
}

#if 1
char* itoa(int n, char* str)
{
  char digit[]="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  char* p=str;
  char* head=str;
  int radix = 10;

//  if(!p || radix < 2 || radix > 36)
//    return p;
  if (n==0)
  {
    *p++='0';
    *p=0;
    return str;
  }
#if 0
  if (radix == 10 && n < 0)
  {
    *p++='-';
    n= -n;
  }
#endif
  while(n)
  {
    *p++=digit[n%radix];
    n/=radix;
  }
  *p=0;
#if 1
  for (--p; head < p ; ++head, --p)
  {
    char temp=*head;
    *head=*p;
    *p=temp;
  }
#endif
  return str;
}
#endif

#if 0
extern u32 __bss_start__;
extern u32 __bss_end__;
void init_bss()
{
  u8 *bss=(u8*)__bss_start__;
  *bss = 0x1;
  *(bss+1) = 0x1;
  *(bss+2) = 0x1;
  *(bss+3) = 0x1;
#if 0
  while (i!=(u8*)__bss_end__)
  {
    *i = 0x1;
    ++i;
  }
#endif
}
#endif