build.c

Go to the documentation of this file.

/*
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Copyright (C) 1997 Martin Mares
 *  Copyright (C) 2007 H. Peter Anvin
 */

/*
 * This file builds a disk-image from two different files:
 *
 * - 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
 * Substantially overhauled by H. Peter Anvin, April 2007
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <tools/le_byteshift.h>

typedef unsigned char  u8;
typedef unsigned short u16;
typedef unsigned int   u32;

#define DEFAULT_MAJOR_ROOT 0
#define DEFAULT_MINOR_ROOT 0
#define DEFAULT_ROOT_DEV (DEFAULT_MAJOR_ROOT << 8 | DEFAULT_MINOR_ROOT)

/* Minimal number of setup sectors */
#define SETUP_SECT_MIN 5
#define SETUP_SECT_MAX 64

/* This must be large enough to hold the entire setup */
u8 buf[SETUP_SECT_MAX*512];
int is_big_kernel;

#define PECOFF_RELOC_RESERVE 0x20

/*----------------------------------------------------------------------*/

static const u32 crctab32[] = {
    0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
    0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
    0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
    0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
    0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
    0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
    0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
    0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
    0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
    0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
    0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
    0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
    0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
    0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
    0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
    0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
    0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
    0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
    0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
    0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
    0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
    0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
    0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
    0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
    0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
    0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
    0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
    0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
    0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
    0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
    0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
    0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
    0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
    0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
    0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
    0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
    0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
    0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
    0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
    0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
    0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
    0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
    0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
    0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
    0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
    0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
    0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
    0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
    0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
    0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
    0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
    0x2d02ef8d
};

static u32 partial_crc32_one(u8 c, u32 crc)
{
    return crctab32[(crc ^ c) & 0xff] ^ (crc >> 8);
}

static u32 partial_crc32(const u8 *s, int len, u32 crc)
{
    while (len--)
        crc = partial_crc32_one(*s++, crc);
    return crc;
}

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

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

#ifdef CONFIG_EFI_STUB

static void update_pecoff_section_header(char *section_name, u32 offset, u32 size)
{
    unsigned int pe_header;
    unsigned short num_sections;
    u8 *section;

    pe_header = get_unaligned_le32(&buf[0x3c]);
    num_sections = get_unaligned_le16(&buf[pe_header + 6]);

#ifdef CONFIG_X86_32
    section = &buf[pe_header + 0xa8];
#else
    section = &buf[pe_header + 0xb8];
#endif

    while (num_sections > 0) {
        if (strncmp((char*)section, section_name, 8) == 0) {
            /* section header size field */
            put_unaligned_le32(size, section + 0x8);

            /* section header vma field */
            put_unaligned_le32(offset, section + 0xc);

            /* section header 'size of initialised data' field */
            put_unaligned_le32(size, section + 0x10);

            /* section header 'file offset' field */
            put_unaligned_le32(offset, section + 0x14);

            break;
        }
        section += 0x28;
        num_sections--;
    }
}

static void update_pecoff_setup_and_reloc(unsigned int size)
{
    u32 setup_offset = 0x200;
    u32 reloc_offset = size - PECOFF_RELOC_RESERVE;
    u32 setup_size = reloc_offset - setup_offset;

    update_pecoff_section_header(".setup", setup_offset, setup_size);
    update_pecoff_section_header(".reloc", reloc_offset, PECOFF_RELOC_RESERVE);

    /*
     * Modify .reloc section contents with a single entry. The
     * relocation is applied to offset 10 of the relocation section.
     */
    put_unaligned_le32(reloc_offset + 10, &buf[reloc_offset]);
    put_unaligned_le32(10, &buf[reloc_offset + 4]);
}

static void update_pecoff_text(unsigned int text_start, unsigned int file_sz)
{
    unsigned int pe_header;
    unsigned int text_sz = file_sz - text_start;

    pe_header = get_unaligned_le32(&buf[0x3c]);

    /* Size of image */
    put_unaligned_le32(file_sz, &buf[pe_header + 0x50]);

    /*
     * Size of code: Subtract the size of the first sector (512 bytes)
     * which includes the header.
     */
    put_unaligned_le32(file_sz - 512, &buf[pe_header + 0x1c]);

#ifdef CONFIG_X86_32
    /*
     * Address of entry point.
     *
     * The EFI stub entry point is +16 bytes from the start of
     * the .text section.
     */
    put_unaligned_le32(text_start + 16, &buf[pe_header + 0x28]);
#else
    /*
     * Address of entry point. startup_32 is at the beginning and
     * the 64-bit entry point (startup_64) is always 512 bytes
     * after. The EFI stub entry point is 16 bytes after that, as
     * the first instruction allows legacy loaders to jump over
     * the EFI stub initialisation
     */
    put_unaligned_le32(text_start + 528, &buf[pe_header + 0x28]);
#endif /* CONFIG_X86_32 */

    update_pecoff_section_header(".text", text_start, text_sz);
}

#endif /* CONFIG_EFI_STUB */

int main(int argc, char ** argv)
{
    unsigned int i, sz, setup_sectors;
    int c;
    u32 sys_size;
    struct stat sb;
    FILE *file;
    int fd;
    void *kernel;
    u32 crc = 0xffffffffUL;

    if (argc != 3)
        usage();

    /* Copy the setup code */
    file = fopen(argv[1], "r");
    if (!file)
        die("Unable to open `%s': %m", argv[1]);
    c = fread(buf, 1, sizeof(buf), file);
    if (ferror(file))
        die("read-error on `setup'");
    if (c < 1024)
        die("The setup must be at least 1024 bytes");
    if (get_unaligned_le16(&buf[510]) != 0xAA55)
        die("Boot block hasn't got boot flag (0xAA55)");
    fclose(file);

#ifdef CONFIG_EFI_STUB
    /* Reserve 0x20 bytes for .reloc section */
    memset(buf+c, 0, PECOFF_RELOC_RESERVE);
    c += PECOFF_RELOC_RESERVE;
#endif

    /* Pad unused space with zeros */
    setup_sectors = (c + 511) / 512;
    if (setup_sectors < SETUP_SECT_MIN)
        setup_sectors = SETUP_SECT_MIN;
    i = setup_sectors*512;
    memset(buf+c, 0, i-c);

#ifdef CONFIG_EFI_STUB
    update_pecoff_setup_and_reloc(i);
#endif

    /* Set the default root device */
    put_unaligned_le16(DEFAULT_ROOT_DEV, &buf[508]);

    fprintf(stderr, "Setup is %d bytes (padded to %d bytes).\n", c, i);

    /* Open and stat the kernel file */
    fd = open(argv[2], O_RDONLY);
    if (fd < 0)
        die("Unable to open `%s': %m", argv[2]);
    if (fstat(fd, &sb))
        die("Unable to stat `%s': %m", argv[2]);
    sz = sb.st_size;
    fprintf (stderr, "System is %d kB\n", (sz+1023)/1024);
    kernel = mmap(NULL, sz, PROT_READ, MAP_SHARED, fd, 0);
    if (kernel == MAP_FAILED)
        die("Unable to mmap '%s': %m", argv[2]);
    /* Number of 16-byte paragraphs, including space for a 4-byte CRC */
    sys_size = (sz + 15 + 4) / 16;

    /* Patch the setup code with the appropriate size parameters */
    buf[0x1f1] = setup_sectors-1;
    put_unaligned_le32(sys_size, &buf[0x1f4]);

#ifdef CONFIG_EFI_STUB
    update_pecoff_text(setup_sectors * 512, sz + i + ((sys_size * 16) - sz));
#endif

    crc = partial_crc32(buf, i, crc);
    if (fwrite(buf, 1, i, stdout) != i)
        die("Writing setup failed");

    /* Copy the kernel code */
    crc = partial_crc32(kernel, sz, crc);
    if (fwrite(kernel, 1, sz, stdout) != sz)
        die("Writing kernel failed");

    /* Add padding leaving 4 bytes for the checksum */
    while (sz++ < (sys_size*16) - 4) {
        crc = partial_crc32_one('\0', crc);
        if (fwrite("\0", 1, 1, stdout) != 1)
            die("Writing padding failed");
    }

    /* Write the CRC */
    fprintf(stderr, "CRC %x\n", crc);
    put_unaligned_le32(crc, buf);
    if (fwrite(buf, 1, 4, stdout) != 4)
        die("Writing CRC failed");

    close(fd);

    /* Everything is OK */
    return 0;
}