kernel.c.texi

i386的bootloader源码grub

/* @r{kernel.c - the C part of the kernel} */
/* @r{Copyright (C) 1999  Free Software Foundation, Inc.
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.} */

#include <multiboot.h>

/* @r{Macros.} */

/* @r{Check if the bit BIT in FLAGS is set.} */
#define CHECK_FLAG(flags,bit)   ((flags) & (1 << (bit)))

/* @r{Some screen stuff.} */
/* @r{The number of columns.} */
#define COLUMNS                 80
/* @r{The number of lines.} */
#define LINES                   24
/* @r{The attribute of an character.} */
#define ATTRIBUTE               7
/* @r{The video memory address.} */
#define VIDEO                   0xB8000

/* @r{Variables.} */
/* @r{Save the X position.} */
static int xpos;
/* @r{Save the Y position.} */
static int ypos;
/* @r{Point to the video memory.} */
static volatile unsigned char *video;

/* @r{Forward declarations.} */
void cmain (unsigned long magic, unsigned long addr);
static void cls (void);
static void itoa (char *buf, int base, int d);
static void putchar (int c);
void printf (const char *format, ...);

/* @r{Check if MAGIC is valid and print the Multiboot information structure
   pointed by ADDR.} */
void
cmain (unsigned long magic, unsigned long addr)
@{
  multiboot_info_t *mbi;
  
  /* @r{Clear the screen.} */
  cls ();

  /* @r{Am I booted by a Multiboot-compliant boot loader?} */
  if (magic != MULTIBOOT_BOOTLOADER_MAGIC)
    @{
      printf ("Invalid magic number: 0x%x\n", (unsigned) magic);
      return;
    @}

  /* @r{Set MBI to the address of the Multiboot information structure.} */
  mbi = (multiboot_info_t *) addr;

  /* @r{Print out the flags.} */
  printf ("flags = 0x%x\n", (unsigned) mbi->flags);

  /* @r{Are mem_* valid?} */
  if (CHECK_FLAG (mbi->flags, 0))
    printf ("mem_lower = %uKB, mem_upper = %uKB\n",
            (unsigned) mbi->mem_lower, (unsigned) mbi->mem_upper);

  /* @r{Is boot_device valid?} */
  if (CHECK_FLAG (mbi->flags, 1))
    printf ("boot_device = 0x%x\n", (unsigned) mbi->boot_device);
  
  /* @r{Is the command line passed?} */
  if (CHECK_FLAG (mbi->flags, 2))
    printf ("cmdline = %s\n", (char *) mbi->cmdline);

  /* @r{Are mods_* valid?} */
  if (CHECK_FLAG (mbi->flags, 3))
    @{
      module_t *mod;
      int i;
      
      printf ("mods_count = %d, mods_addr = 0x%x\n",
              (int) mbi->mods_count, (int) mbi->mods_addr);
      for (i = 0, mod = (module_t *) mbi->mods_addr;
           i < mbi->mods_count;
           i++, mod += sizeof (module_t))
        printf (" mod_start = 0x%x, mod_end = 0x%x, string = %s\n",
                (unsigned) mod->mod_start,
                (unsigned) mod->mod_end,
                (char *) mod->string);
    @}

  /* @r{Bits 4 and 5 are mutually exclusive!} */
  if (CHECK_FLAG (mbi->flags, 4) && CHECK_FLAG (mbi->flags, 5))
    @{
      printf ("Both bits 4 and 5 are set.\n");
      return;
    @}

  /* @r{Is the symbol table of a.out valid?} */
  if (CHECK_FLAG (mbi->flags, 4))
    @{
      aout_symbol_table_t *aout_sym = &(mbi->u.aout_sym);
      
      printf ("aout_symbol_table: tabsize = 0x%0x, "
              "strsize = 0x%x, addr = 0x%x\n",
              (unsigned) aout_sym->tabsize,
              (unsigned) aout_sym->strsize,
              (unsigned) aout_sym->addr);
    @}

  /* @r{Is the section header table of ELF valid?} */
  if (CHECK_FLAG (mbi->flags, 5))
    @{
      elf_section_header_table_t *elf_sec = &(mbi->u.elf_sec);

      printf ("elf_sec: num = %u, size = 0x%x,"
              " addr = 0x%x, shndx = 0x%x\n",
              (unsigned) elf_sec->num, (unsigned) elf_sec->size,
              (unsigned) elf_sec->addr, (unsigned) elf_sec->shndx);
    @}

  /* @r{Are mmap_* valid?} */
  if (CHECK_FLAG (mbi->flags, 6))
    @{
      memory_map_t *mmap;
      
      printf ("mmap_addr = 0x%x, mmap_length = 0x%x\n",
              (unsigned) mbi->mmap_addr, (unsigned) mbi->mmap_length);
      for (mmap = (memory_map_t *) mbi->mmap_addr;
           (unsigned long) mmap < mbi->mmap_addr + mbi->mmap_length;
           mmap = (memory_map_t *) ((unsigned long) mmap
                                    + mmap->size + sizeof (mmap->size)))
        printf (" size = 0x%x, base_addr = 0x%x%x,"
                " length = 0x%x%x, type = 0x%x\n",
                (unsigned) mmap->size,
                (unsigned) mmap->base_addr_high,
                (unsigned) mmap->base_addr_low,
                (unsigned) mmap->length_high,
                (unsigned) mmap->length_low,
                (unsigned) mmap->type);
    @}
@}    

/* @r{Clear the screen and initialize VIDEO, XPOS and YPOS.} */
static void
cls (void)
@{
  int i;

  video = (unsigned char *) VIDEO;
  
  for (i = 0; i < COLUMNS * LINES * 2; i++)
    *(video + i) = 0;

  xpos = 0;
  ypos = 0;
@}

/* @r{Convert the integer D to a string and save the string in BUF. If
   BASE is equal to 'd', interpret that D is decimal, and if BASE is
   equal to 'x', interpret that D is hexadecimal.} */
static void
itoa (char *buf, int base, int d)
@{
  char *p = buf;
  char *p1, *p2;
  unsigned long ud = d;
  int divisor = 10;
  
  /* @r{If %d is specified and D is minus, put `-' in the head.} */
  if (base == 'd' && d < 0)
    @{
      *p++ = '-';
      buf++;
      ud = -d;
    @}
  else if (base == 'x')
    divisor = 16;

  /* @r{Divide UD by DIVISOR until UD == 0.} */
  do
    @{
      int remainder = ud % divisor;
      
      *p++ = (remainder < 10) ? remainder + '0' : remainder + 'a' - 10;
    @}
  while (ud /= divisor);

  /* @r{Terminate BUF.} */
  *p = 0;
  
  /* @r{Reverse BUF.} */
  p1 = buf;
  p2 = p - 1;
  while (p1 < p2)
    @{
      char tmp = *p1;
      *p1 = *p2;
      *p2 = tmp;
      p1++;
      p2--;
    @}
@}

/* @r{Put the character C on the screen.} */
static void
putchar (int c)
@{
  if (c == '\n' || c == '\r')
    @{
    newline:
      xpos = 0;
      ypos++;
      if (ypos >= LINES)
        ypos = 0;
      return;
    @}

  *(video + (xpos + ypos * COLUMNS) * 2) = c & 0xFF;
  *(video + (xpos + ypos * COLUMNS) * 2 + 1) = ATTRIBUTE;

  xpos++;
  if (xpos >= COLUMNS)
    goto newline;
@}

/* @r{Format a string and print it on the screen, just like the libc
   function printf.} */
void
printf (const char *format, ...)
@{
  char **arg = (char **) &format;
  int c;
  char buf[20];

  arg++;
  
  while ((c = *format++) != 0)
    @{
      if (c != '%')
        putchar (c);
      else
        @{
          char *p;
          
          c = *format++;
          switch (c)
            @{
            case 'd':
            case 'u':
            case 'x':
              itoa (buf, c, *((int *) arg++));
              p = buf;
              goto string;
              break;

            case 's':
              p = *arg++;
              if (! p)
                p = "(null)";

            string:
              while (*p)
                putchar (*p++);
              break;

            default:
              putchar (*((int *) arg++));
              break;
            @}
        @}
    @}
@}