add an example Multiboot kernel.
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11 changed files with 1053 additions and 12 deletions
274
docs/kernel.c
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274
docs/kernel.c
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/* kernel.c - the C part of the kernel */
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/* Copyright (C) 1999 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
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#include <multiboot.h>
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/* Macros. */
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/* Check if the bit BIT in FLAGS is set. */
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#define CHECK_FLAG(flags,bit) ((flags) & (1 << (bit)))
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/* Some screen stuff. */
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/* The number of columns. */
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#define COLUMNS 80
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/* The number of lines. */
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#define LINES 24
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/* The attribute of an character. */
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#define ATTRIBUTE 7
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/* The video memory address. */
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#define VIDEO 0xB8000
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/* Variables. */
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/* Save the X position. */
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static int xpos;
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/* Save the Y position. */
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static int ypos;
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/* Point to the video memory. */
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static volatile unsigned char *video;
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/* Forward declarations. */
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void cmain (unsigned long magic, unsigned long addr);
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static void cls (void);
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static void itoa (char *buf, int base, int d);
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static void putchar (int c);
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void printf (const char *format, ...);
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/* Check if MAGIC is valid and print the Multiboot information structure
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pointed by ADDR. */
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void
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cmain (unsigned long magic, unsigned long addr)
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{
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multiboot_info_t *mbi;
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/* Clear the screen. */
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cls ();
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/* Am I booted by a Multiboot-compliant boot loader? */
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if (magic != MULTIBOOT_BOOTLOADER_MAGIC)
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{
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printf ("Invalid magic number: 0x%x\n", magic);
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return;
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}
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/* Set MBI to the address of the Multiboot information structure. */
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mbi = (multiboot_info_t *) addr;
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/* Print out the flags. */
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printf ("flags = 0x%x\n", mbi->flags);
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/* Are mem_* valid? */
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if (CHECK_FLAG (mbi->flags, 0))
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printf ("mem_lower = %dKB, mem_upper = %dKB\n",
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mbi->mem_lower, mbi->mem_upper);
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/* Is boot_device valid? */
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if (CHECK_FLAG (mbi->flags, 1))
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printf ("boot_device = 0x%x\n", mbi->boot_device);
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/* Is the command line passed? */
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if (CHECK_FLAG (mbi->flags, 2))
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printf ("cmdline = %s\n", (char *) mbi->cmdline);
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/* Are mods_* valid? */
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if (CHECK_FLAG (mbi->flags, 3))
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{
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module_t *mod;
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int i;
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printf ("mods_count = %d, mods_addr = 0x%x\n",
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mbi->mods_count, mbi->mods_addr);
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for (i = 0, mod = (module_t *) mbi->mods_addr;
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i < mbi->mods_count;
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i++, mod += sizeof (module_t))
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printf (" mod_start = 0x%x, mod_end = 0x%x, string = %s\n",
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mod->mod_start, mod->mod_end, (char *) mod->string);
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}
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/* Bits 4 and 5 are mutually exclusive! */
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if (CHECK_FLAG (mbi->flags, 4) && CHECK_FLAG (mbi->flags, 5))
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{
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printf ("Both bits 4 and 5 are set.\n");
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return;
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}
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/* Is the symbol table of a.out valid? */
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if (CHECK_FLAG (mbi->flags, 4))
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{
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aout_symbol_table_t *aout_sym = &(mbi->u.aout_sym);
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printf ("aout_symbol_table: tabsize = 0x%0x, "
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"strsize = 0x%x, addr = 0x%x\n",
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aout_sym->tabsize, aout_sym->strsize, aout_sym->addr);
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}
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/* Is the section header table of ELF valid? */
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if (CHECK_FLAG (mbi->flags, 5))
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{
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elf_section_header_table_t *elf_sec = &(mbi->u.elf_sec);
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printf ("elf_sec: num = %d, size = 0x%x, addr = 0x%x, shndx = 0x%x\n",
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elf_sec->num, elf_sec->size, elf_sec->addr, elf_sec->shndx);
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}
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/* Are mmap_* valid? */
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if (CHECK_FLAG (mbi->flags, 6))
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{
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memory_map_t *mmap;
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printf ("mmap_addr = 0x%x, mmap_length = 0x%x\n",
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mbi->mmap_addr, mbi->mmap_length);
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for (mmap = (memory_map_t *) mbi->mmap_addr;
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(unsigned long) mmap < mbi->mmap_addr + mbi->mmap_length;
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mmap = (memory_map_t *) ((unsigned long) mmap
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+ mmap->size + sizeof (mmap->size)))
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printf (" size = 0x%x, base_addr = 0x%x%x,"
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" length = 0x%x%x, type = 0x%x\n",
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mmap->size, mmap->base_addr_high, mmap->base_addr_low,
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mmap->length_high, mmap->length_low, mmap->type);
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}
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}
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/* Clear the screen and initialize VIDEO, XPOS and YPOS. */
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static void
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cls (void)
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{
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int i;
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video = (unsigned char *) VIDEO;
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for (i = 0; i < COLUMNS * LINES * 2; i++)
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*(video + i) = 0;
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xpos = 0;
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ypos = 0;
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}
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/* Convert the integer D to a string and save the string in BUF. If
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BASE is equal to 'd', interpret that D is decimal, and if BASE is
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equal to 'x', interpret that D is hexadecimal. */
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static void
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itoa (char *buf, int base, int d)
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{
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char *p = buf;
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char *p1, *p2;
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unsigned long ud = d;
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int divisor = 10;
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/* If %d is specified and D is minus, put `-' in the head. */
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if (base == 'd' && d < 0)
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{
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*p++ = '-';
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buf++;
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ud = -d;
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}
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else if (base == 'x')
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divisor = 16;
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/* Divide UD by DIVISOR until UD == 0. */
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do
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{
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int remainder = ud % divisor;
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*p++ = (remainder < 10) ? remainder + '0' : remainder + 'a' - 10;
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}
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while (ud /= divisor);
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/* Terminate BUF. */
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*p = 0;
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/* Reverse BUF. */
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p1 = buf;
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p2 = p - 1;
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while (p1 < p2)
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{
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char tmp = *p1;
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*p1 = *p2;
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*p2 = tmp;
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p1++;
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p2--;
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}
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}
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/* Put the character C on the screen. */
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static void
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putchar (int c)
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{
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if (c == '\n' || c == '\r')
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{
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newline:
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xpos = 0;
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ypos++;
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if (ypos >= LINES)
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ypos = 0;
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return;
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}
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*(video + (xpos + ypos * COLUMNS) * 2) = c & 0xFF;
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*(video + (xpos + ypos * COLUMNS) * 2 + 1) = ATTRIBUTE;
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xpos++;
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if (xpos >= COLUMNS)
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goto newline;
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}
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/* Format a string and print it on the screen, just like the libc
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function printf. */
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void
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printf (const char *format, ...)
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{
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char **arg = (char **) &format;
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int c;
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char buf[20];
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arg++;
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while ((c = *format++) != 0)
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{
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if (c != '%')
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putchar (c);
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else
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{
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char *p;
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c = *format++;
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switch (c)
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{
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case 'd':
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case 'u':
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case 'x':
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itoa (buf, c, *((int *) arg++));
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p = buf;
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goto string;
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break;
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case 's':
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p = *arg++;
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if (! p)
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p = "(null)";
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string:
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while (*p)
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putchar (*p++);
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break;
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default:
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putchar (*((int *) arg++));
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break;
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}
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}
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}
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}
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