build.c

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/*
 *  $Id: build.c,v 1.5 1997/05/19 12:29:58 mj Exp $
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Copyright (C) 1997 Martin Mares
 */

/*
 * This file builds a disk-image from three different files:
 *
 * - bootsect: exactly 512 bytes of 8086 machine code, loads the rest
 * - setup: 8086 machine code, sets up system parm
 * - system: 80386 code for actual system
 *
 * It does some checking that all files are of the correct type, and
 * just writes the result to stdout, removing headers and padding to
 * the right amount. It also writes some system data to stderr.
 */

/*
 * Changes by tytso to allow root device specification
 * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
 * Cross compiling fixes by Gertjan van Wingerde, July 1996
 * Rewritten by Martin Mares, April 1997
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>
#include <unistd.h>
#include <fcntl.h>
#include <asm/boot.h>

typedef unsigned char byte;
typedef unsigned short word;
typedef unsigned long u32;

#define DEFAULT_MAJOR_ROOT 0
#define DEFAULT_MINOR_ROOT 0

/* Minimal number of setup sectors (see also bootsect.S) */
#define SETUP_SECTS 4

byte buf[1024];
int fd;
int is_big_kernel;

void die(const char * str, ...)
{
        va_list args;
        va_start(args, str);
        vfprintf(stderr, str, args);
        fputc('\n', stderr);
        exit(1);
}

void file_open(const char *name)
{
        if ((fd = open(name, O_RDONLY, 0)) < 0)
                die("Unable to open `%s': %m", name);
}

void usage(void)
{
        die("Usage: build [-b] bootsect setup system [rootdev] [> image]");
}

int main(int argc, char ** argv)
{
        unsigned int i, c, sz, setup_sectors;
        u32 sys_size;
        byte major_root, minor_root;
        struct stat sb;

        if (argc > 2 && !strcmp(argv[1], "-b"))
          {
            is_big_kernel = 1;
            argc--, argv++;
          }
        if ((argc < 4) || (argc > 5))
                usage();
        if (argc > 4) {
                if (!strcmp(argv[4], "CURRENT")) {
                        if (stat("/", &sb)) {
                                perror("/");
                                die("Couldn't stat /");
                        }
                        major_root = major(sb.st_dev);
                        minor_root = minor(sb.st_dev);
                } else if (strcmp(argv[4], "FLOPPY")) {
                        if (stat(argv[4], &sb)) {
                                perror(argv[4]);
                                die("Couldn't stat root device.");
                        }
                        major_root = major(sb.st_rdev);
                        minor_root = minor(sb.st_rdev);
                } else {
                        major_root = 0;
                        minor_root = 0;
                }
        } else {
                major_root = DEFAULT_MAJOR_ROOT;
                minor_root = DEFAULT_MINOR_ROOT;
        }
        fprintf(stderr, "Root device is (%d, %d)\n", major_root, minor_root);

        file_open(argv[1]);
        i = read(fd, buf, sizeof(buf));
        fprintf(stderr,"Boot sector %d bytes.\n",i);
        if (i != 512)
                die("Boot block must be exactly 512 bytes");
        if (buf[510] != 0x55 || buf[511] != 0xaa)
                die("Boot block hasn't got boot flag (0xAA55)");
        buf[508] = minor_root;
        buf[509] = major_root;
        if (write(1, buf, 512) != 512)
                die("Write call failed");
        close (fd);

        file_open(argv[2]);                                 /* Copy the setup code */
        for (i=0 ; (c=read(fd, buf, sizeof(buf)))>0 ; i+=c )
                if (write(1, buf, c) != c)
                        die("Write call failed");
        if (c != 0)
                die("read-error on `setup'");
        close (fd);

        setup_sectors = (i + 511) / 512;        /* Pad unused space with zeros */
        /* for compatibility with ancient versions of LILO. */
        if (setup_sectors < SETUP_SECTS)
                setup_sectors = SETUP_SECTS;
        fprintf(stderr, "Setup is %d bytes.\n", i);
        memset(buf, 0, sizeof(buf));
        while (i < setup_sectors * 512) {
                c = setup_sectors * 512 - i;
                if (c > sizeof(buf))
                        c = sizeof(buf);
                if (write(1, buf, c) != c)
                        die("Write call failed");
                i += c;
        }

        file_open(argv[3]);
        if (fstat (fd, &sb))
                die("Unable to stat `%s': %m", argv[3]);
        sz = sb.st_size;
        fprintf (stderr, "System is %d kB\n", sz/1024);
        sys_size = (sz + 15) / 16;
        /* 0x28000*16 = 2.5 MB, conservative estimate for the current maximum */
        if (sys_size > (is_big_kernel ? 0x28000 : DEF_SYSSIZE))
                die("System is too big. Try using %smodules.",
                        is_big_kernel ? "" : "bzImage or ");
        if (sys_size > 0xefff)
                fprintf(stderr,"warning: kernel is too big for standalone boot "
                    "from floppy\n");
        while (sz > 0) {
                int l, n;

                l = (sz > sizeof(buf)) ? sizeof(buf) : sz;
                if ((n=read(fd, buf, l)) != l) {
                        if (n < 0)
                                die("Error reading %s: %m", argv[3]);
                        else
                                die("%s: Unexpected EOF", argv[3]);
                }
                if (write(1, buf, l) != l)
                        die("Write failed");
                sz -= l;
        }
        close(fd);

        if (lseek(1, 497, SEEK_SET) != 497)                 /* Write sizes to the bootsector */
                die("Output: seek failed");
        buf[0] = setup_sectors;
        if (write(1, buf, 1) != 1)
                die("Write of setup sector count failed");
        if (lseek(1, 500, SEEK_SET) != 500)
                die("Output: seek failed");
        buf[0] = (sys_size & 0xff);
        buf[1] = ((sys_size >> 8) & 0xff);
        if (write(1, buf, 2) != 2)
                die("Write of image length failed");

        return 0;                                           /* Everything is OK */
}