arch/all-pc/boot/grub/docs/kernel.c

   1 /* kernel.c - the C part of the kernel */
   2 /* Copyright (C) 1999  Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software
  16    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
  17
  18 #include <multiboot.h>
  19
  20 /* Macros.  */
  21
  22 /* Check if the bit BIT in FLAGS is set.  */
  23 #define CHECK_FLAG(flags,bit)   ((flags) & (1 << (bit)))
  24
  25 /* Some screen stuff.  */
  26 /* The number of columns.  */
  27 #define COLUMNS                 80
  28 /* The number of lines.  */
  29 #define LINES                   24
  30 /* The attribute of an character.  */
  31 #define ATTRIBUTE               7
  32 /* The video memory address.  */
  33 #define VIDEO                   0xB8000
  34
  35 /* Variables.  */
  36 /* Save the X position.  */
  37 static int xpos;
  38 /* Save the Y position.  */
  39 static int ypos;
  40 /* Point to the video memory.  */
  41 static volatile unsigned char *video;
  42
  43 /* Forward declarations.  */
  44 void cmain (unsigned long magic, unsigned long addr);
  45 static void cls (void);
  46 static void itoa (char *buf, int base, int d);
  47 static void putchar (int c);
  48 void printf (const char *format, ...);
  49
  50 /* Check if MAGIC is valid and print the Multiboot information structure
  51    pointed by ADDR.  */
  52 void
  53 cmain (unsigned long magic, unsigned long addr)
  54 {
  55   multiboot_info_t *mbi;
  56
  57   /* Clear the screen.  */
  58   cls ();
  59
  60   /* Am I booted by a Multiboot-compliant boot loader?  */
  61   if (magic != MULTIBOOT_BOOTLOADER_MAGIC)
  62     {
  63       printf ("Invalid magic number: 0x%x\n", (unsigned) magic);
  64       return;
  65     }
  66
  67   /* Set MBI to the address of the Multiboot information structure.  */
  68   mbi = (multiboot_info_t *) addr;
  69
  70   /* Print out the flags.  */
  71   printf ("flags = 0x%x\n", (unsigned) mbi->flags);
  72
  73   /* Are mem_* valid?  */
  74   if (CHECK_FLAG (mbi->flags, 0))
  75     printf ("mem_lower = %uKB, mem_upper = %uKB\n",
  76             (unsigned) mbi->mem_lower, (unsigned) mbi->mem_upper);
  77
  78   /* Is boot_device valid?  */
  79   if (CHECK_FLAG (mbi->flags, 1))
  80     printf ("boot_device = 0x%x\n", (unsigned) mbi->boot_device);
  81
  82   /* Is the command line passed?  */
  83   if (CHECK_FLAG (mbi->flags, 2))
  84     printf ("cmdline = %s\n", (char *) mbi->cmdline);
  85
  86   /* Are mods_* valid?  */
  87   if (CHECK_FLAG (mbi->flags, 3))
  88     {
  89       module_t *mod;
  90       int i;
  91
  92       printf ("mods_count = %d, mods_addr = 0x%x\n",
  93               (int) mbi->mods_count, (int) mbi->mods_addr);
  94       for (i = 0, mod = (module_t *) mbi->mods_addr;
  95            i < mbi->mods_count;
  96            i++, mod++)
  97         printf (" mod_start = 0x%x, mod_end = 0x%x, string = %s\n",
  98                 (unsigned) mod->mod_start,
  99                 (unsigned) mod->mod_end,
 100                 (char *) mod->string);
 101     }
 102
 103   /* Bits 4 and 5 are mutually exclusive!  */
 104   if (CHECK_FLAG (mbi->flags, 4) && CHECK_FLAG (mbi->flags, 5))
 105     {
 106       printf ("Both bits 4 and 5 are set.\n");
 107       return;
 108     }
 109
 110   /* Is the symbol table of a.out valid?  */
 111   if (CHECK_FLAG (mbi->flags, 4))
 112     {
 113       aout_symbol_table_t *aout_sym = &(mbi->u.aout_sym);
 114
 115       printf ("aout_symbol_table: tabsize = 0x%0x, "
 116               "strsize = 0x%x, addr = 0x%x\n",
 117               (unsigned) aout_sym->tabsize,
 118               (unsigned) aout_sym->strsize,
 119               (unsigned) aout_sym->addr);
 120     }
 121
 122   /* Is the section header table of ELF valid?  */
 123   if (CHECK_FLAG (mbi->flags, 5))
 124     {
 125       elf_section_header_table_t *elf_sec = &(mbi->u.elf_sec);
 126
 127       printf ("elf_sec: num = %u, size = 0x%x,"
 128               " addr = 0x%x, shndx = 0x%x\n",
 129               (unsigned) elf_sec->num, (unsigned) elf_sec->size,
 130               (unsigned) elf_sec->addr, (unsigned) elf_sec->shndx);
 131     }
 132
 133   /* Are mmap_* valid?  */
 134   if (CHECK_FLAG (mbi->flags, 6))
 135     {
 136       memory_map_t *mmap;
 137
 138       printf ("mmap_addr = 0x%x, mmap_length = 0x%x\n",
 139               (unsigned) mbi->mmap_addr, (unsigned) mbi->mmap_length);
 140       for (mmap = (memory_map_t *) mbi->mmap_addr;
 141            (unsigned long) mmap < mbi->mmap_addr + mbi->mmap_length;
 142            mmap = (memory_map_t *) ((unsigned long) mmap
 143                                     + mmap->size + sizeof (mmap->size)))
 144         printf (" size = 0x%x, base_addr = 0x%x%x,"
 145                 " length = 0x%x%x, type = 0x%x\n",
 146                 (unsigned) mmap->size,
 147                 (unsigned) mmap->base_addr_high,
 148                 (unsigned) mmap->base_addr_low,
 149                 (unsigned) mmap->length_high,
 150                 (unsigned) mmap->length_low,
 151                 (unsigned) mmap->type);
 152     }
 153 }
 154
 155 /* Clear the screen and initialize VIDEO, XPOS and YPOS.  */
 156 static void
 157 cls (void)
 158 {
 159   int i;
 160
 161   video = (unsigned char *) VIDEO;
 162
 163   for (i = 0; i < COLUMNS * LINES * 2; i++)
 164     *(video + i) = 0;
 165
 166   xpos = 0;
 167   ypos = 0;
 168 }
 169
 170 /* Convert the integer D to a string and save the string in BUF. If
 171    BASE is equal to 'd', interpret that D is decimal, and if BASE is
 172    equal to 'x', interpret that D is hexadecimal.  */
 173 static void
 174 itoa (char *buf, int base, int d)
 175 {
 176   char *p = buf;
 177   char *p1, *p2;
 178   unsigned long ud = d;
 179   int divisor = 10;
 180
 181   /* If %d is specified and D is minus, put `-' in the head.  */
 182   if (base == 'd' && d < 0)
 183     {
 184       *p++ = '-';
 185       buf++;
 186       ud = -d;
 187     }
 188   else if (base == 'x')
 189     divisor = 16;
 190
 191   /* Divide UD by DIVISOR until UD == 0.  */
 192   do
 193     {
 194       int remainder = ud % divisor;
 195
 196       *p++ = (remainder < 10) ? remainder + '0' : remainder + 'a' - 10;
 197     }
 198   while (ud /= divisor);
 199
 200   /* Terminate BUF.  */
 201   *p = 0;
 202
 203   /* Reverse BUF.  */
 204   p1 = buf;
 205   p2 = p - 1;
 206   while (p1 < p2)
 207     {
 208       char tmp = *p1;
 209       *p1 = *p2;
 210       *p2 = tmp;
 211       p1++;
 212       p2--;
 213     }
 214 }
 215
 216 /* Put the character C on the screen.  */
 217 static void
 218 putchar (int c)
 219 {
 220   if (c == '\n' || c == '\r')
 221     {
 222     newline:
 223       xpos = 0;
 224       ypos++;
 225       if (ypos >= LINES)
 226         ypos = 0;
 227       return;
 228     }
 229
 230   *(video + (xpos + ypos * COLUMNS) * 2) = c & 0xFF;
 231   *(video + (xpos + ypos * COLUMNS) * 2 + 1) = ATTRIBUTE;
 232
 233   xpos++;
 234   if (xpos >= COLUMNS)
 235     goto newline;
 236 }
 237
 238 /* Format a string and print it on the screen, just like the libc
 239    function printf.  */
 240 void
 241 printf (const char *format, ...)
 242 {
 243   char **arg = (char **) &format;
 244   int c;
 245   char buf[20];
 246
 247   arg++;
 248
 249   while ((c = *format++) != 0)
 250     {
 251       if (c != '%')
 252         putchar (c);
 253       else
 254         {
 255           char *p;
 256
 257           c = *format++;
 258           switch (c)
 259             {
 260             case 'd':
 261             case 'u':
 262             case 'x':
 263               itoa (buf, c, *((int *) arg++));
 264               p = buf;
 265               goto string;
 266               break;
 267
 268             case 's':
 269               p = *arg++;
 270               if (! p)
 271                 p = "(null)";
 272
 273             string:
 274               while (*p)
 275                 putchar (*p++);
 276               break;
 277
 278             default:
 279               putchar (*((int *) arg++));
 280               break;
 281             }
 282         }
 283     }
 284 }