build.c

Go to the documentation of this file.

/*
 *  linux/tools/build.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

/*
 * 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
 */

#include <stdio.h>  /* fprintf */
#include <string.h>
#include <stdlib.h> /* contains exit */
#include <sys/types.h>  /* unistd.h needs this */
#include <sys/stat.h>
#include <sys/sysmacros.h>
#include <unistd.h> /* contains read/write */
#include <fcntl.h>
#include <errno.h>

#define MINIX_HEADER 32

#define N_MAGIC_OFFSET 1024
#ifndef __BFD__
static int GCC_HEADER = sizeof(struct exec);
#endif

#ifdef __BIG_KERNEL__
#define SYS_SIZE 0xffff
#else
#define SYS_SIZE DEF_SYSSIZE
#endif

#define DEFAULT_MAJOR_ROOT 0
#define DEFAULT_MINOR_ROOT 0

/* max nr of sectors of setup: don't change unless you also change
 * bootsect etc */
#define SETUP_SECTS 4

#define STRINGIFY(x) #x

typedef union {
    int i;
    long l;
    short s[2];
    char b[4];
} conv;

long intel_long(long l)
{
    conv t;

    t.b[0] = l & 0xff; l >>= 8;
    t.b[1] = l & 0xff; l >>= 8;
    t.b[2] = l & 0xff; l >>= 8;
    t.b[3] = l & 0xff; l >>= 8;
    return t.l;
}

int intel_int(int i)
{
    conv t;

    t.b[0] = i & 0xff; i >>= 8;
        t.b[1] = i & 0xff; i >>= 8;
        t.b[2] = i & 0xff; i >>= 8;
        t.b[3] = i & 0xff; i >>= 8;
        return t.i;
}

short intel_short(short l)
{
    conv t;

    t.b[0] = l & 0xff; l >>= 8;
    t.b[1] = l & 0xff; l >>= 8;
    return t.s[0];
}

void die(const char * str)
{
    fprintf(stderr,"%s\n",str);
    exit(1);
}

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

int main(int argc, char ** argv)
{
    int i,c,id,sz,tmp_int;
    unsigned long sys_size, tmp_long;
    char buf[1024];
#ifndef __BFD__
    struct exec *ex = (struct exec *)buf;
#endif
    char major_root, minor_root;
    struct stat sb;
    unsigned char setup_sectors;

    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);
    for (i=0;i<sizeof buf; i++) buf[i]=0;
    if ((id=open(argv[1],O_RDONLY,0))<0)
        die("Unable to open 'boot'");
    if (read(id,buf,MINIX_HEADER) != MINIX_HEADER)
        die("Unable to read header of 'boot'");
    if (((long *) buf)[0]!=intel_long(0x04100301))
        die("Non-Minix header of 'boot'");
    if (((long *) buf)[1]!=intel_long(MINIX_HEADER))
        die("Non-Minix header of 'boot'");
    if (((long *) buf)[3] != 0)
        die("Illegal data segment in 'boot'");
    if (((long *) buf)[4] != 0)
        die("Illegal bss in 'boot'");
    if (((long *) buf)[5] != 0)
        die("Non-Minix header of 'boot'");
    if (((long *) buf)[7] != 0)
        die("Illegal symbol table in 'boot'");
    i=read(id,buf,sizeof buf);
    fprintf(stderr,"Boot sector %d bytes.\n",i);
    if (i != 512)
        die("Boot block must be exactly 512 bytes");
    if ((*(unsigned short *)(buf+510)) != (unsigned short)intel_short(0xAA55))
        die("Boot block hasn't got boot flag (0xAA55)");
    buf[508] = (char) minor_root;
    buf[509] = (char) major_root;   
    i=write(1,buf,512);
    if (i!=512)
        die("Write call failed");
    close (id);
    
    if ((id=open(argv[2],O_RDONLY,0))<0)
        die("Unable to open 'setup'");
    if (read(id,buf,MINIX_HEADER) != MINIX_HEADER)
        die("Unable to read header of 'setup'");
    if (((long *) buf)[0]!=intel_long(0x04100301))
        die("Non-Minix header of 'setup'");
    if (((long *) buf)[1]!=intel_long(MINIX_HEADER))
        die("Non-Minix header of 'setup'");
    if (((long *) buf)[3] != 0)
        die("Illegal data segment in 'setup'");
    if (((long *) buf)[4] != 0)
        die("Illegal bss in 'setup'");
    if (((long *) buf)[5] != 0)
        die("Non-Minix header of 'setup'");
    if (((long *) buf)[7] != 0)
        die("Illegal symbol table in 'setup'");
    for (i=0 ; (c=read(id,buf,sizeof buf))>0 ; i+=c )
#ifdef __BIG_KERNEL__
    {
        if (!i) {
            /* Working with memcpy because of alignment constraints
               on Sparc - Gertjan */
            memcpy(&tmp_long, &buf[2], sizeof(long));
            if (tmp_long != intel_long(0x53726448) )
                die("Wrong magic in loader header of 'setup'");
            memcpy(&tmp_int, &buf[6], sizeof(int));
            if (tmp_int < intel_int(0x200))
                die("Wrong version of loader header of 'setup'");
            buf[0x11] = 1; /* LOADED_HIGH */
            tmp_long = intel_long(0x100000);
            memcpy(&buf[0x14], &tmp_long, sizeof(long));  /* code32_start */
        }
#endif
        if (write(1,buf,c)!=c)
            die("Write call failed");
#ifdef __BIG_KERNEL__
    }
#endif
    if (c != 0)
        die("read-error on 'setup'");
    close (id);
    setup_sectors = (unsigned char)((i + 511) / 512);
    /* for compatibility with LILO */
    if (setup_sectors < SETUP_SECTS)
        setup_sectors = SETUP_SECTS;
    fprintf(stderr,"Setup is %d bytes.\n",i);
    for (c=0 ; c<sizeof(buf) ; c++)
        buf[c] = '\0';
    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;
    }
    
    if ((id=open(argv[3],O_RDONLY,0))<0)
        die("Unable to open 'system'");
#ifndef __BFD__
    if (read(id,buf,GCC_HEADER) != GCC_HEADER)
        die("Unable to read header of 'system'");
    if (N_MAGIC(*ex) == ZMAGIC) {
        GCC_HEADER = N_MAGIC_OFFSET;
        lseek(id, GCC_HEADER, SEEK_SET);
    } else if (N_MAGIC(*ex) != QMAGIC)
        die("Non-GCC header of 'system'");
    fprintf(stderr,"System is %d kB (%d kB code, %d kB data and %d kB bss)\n",
        (ex->a_text+ex->a_data+ex->a_bss)/1024,
        ex->a_text /1024,
        ex->a_data /1024,
        ex->a_bss  /1024);
    sz = N_SYMOFF(*ex) - GCC_HEADER + 4;
#else
    if (fstat (id, &sb)) {
      perror ("fstat");
      die ("Unable to stat 'system'");
    }
    sz = sb.st_size;
    fprintf (stderr, "System is %d kB\n", sz/1024);
#endif
    sys_size = (sz + 15) / 16;
    if (sys_size > SYS_SIZE)
        die("System is too big");
    while (sz > 0) {
        int l, n;

        l = sz;
        if (l > sizeof(buf))
            l = sizeof(buf);
        if ((n=read(id, buf, l)) != l) {
            if (n == -1) 
                perror(argv[1]);
            else
                fprintf(stderr, "Unexpected EOF\n");
            die("Can't read 'system'");
        }
        if (write(1, buf, l) != l)
            die("Write failed");
        sz -= l;
    }
    close(id);
    if (lseek(1, 497, 0) == 497) {
        if (write(1, &setup_sectors, 1) != 1)
            die("Write of setup sectors failed");
    }
    if (lseek(1,500,0) == 500) {
        buf[0] = (sys_size & 0xff);
        buf[1] = ((sys_size >> 8) & 0xff);
        if (write(1, buf, 2) != 2)
            die("Write failed");
    }
    return(0);
}