mktree.c

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/*
 * Makes a tree bootable image for IBM Evaluation boards.
 * Basically, just take a zImage, skip the ELF header, and stuff
 * a 32 byte header on the front.
 *
 * We use htonl, which is a network macro, to make sure we're doing
 * The Right Thing on an LE machine.  It's non-obvious, but it should
 * work on anything BSD'ish.
 */

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>
#include <netinet/in.h>
#ifdef __sun__
#include <inttypes.h>
#else
#include <stdint.h>
#endif

/* This gets tacked on the front of the image.  There are also a few
 * bytes allocated after the _start label used by the boot rom (see
 * head.S for details).
 */
typedef struct boot_block {
    uint32_t bb_magic;      /* 0x0052504F */
    uint32_t bb_dest;       /* Target address of the image */
    uint32_t bb_num_512blocks;  /* Size, rounded-up, in 512 byte blks */
    uint32_t bb_debug_flag; /* Run debugger or image after load */
    uint32_t bb_entry_point;    /* The image address to start */
    uint32_t bb_checksum;   /* 32 bit checksum including header */
    uint32_t reserved[2];
} boot_block_t;

#define IMGBLK  512
unsigned int    tmpbuf[IMGBLK / sizeof(unsigned int)];

int main(int argc, char *argv[])
{
    int in_fd, out_fd;
    int nblks, i;
    unsigned int    cksum, *cp;
    struct  stat    st;
    boot_block_t    bt;

    if (argc < 5) {
        fprintf(stderr, "usage: %s <zImage-file> <boot-image> <load address> <entry point>\n",argv[0]);
        exit(1);
    }

    if (stat(argv[1], &st) < 0) {
        perror("stat");
        exit(2);
    }

    nblks = (st.st_size + IMGBLK) / IMGBLK;

    bt.bb_magic = htonl(0x0052504F);

    /* If we have the optional entry point parameter, use it */
    bt.bb_dest = htonl(strtoul(argv[3], NULL, 0));
    bt.bb_entry_point = htonl(strtoul(argv[4], NULL, 0));

    /* We know these from the linker command.
     * ...and then move it up into memory a little more so the
     * relocation can happen.
     */
    bt.bb_num_512blocks = htonl(nblks);
    bt.bb_debug_flag = 0;

    bt.bb_checksum = 0;

    /* To be neat and tidy :-).
    */
    bt.reserved[0] = 0;
    bt.reserved[1] = 0;

    if ((in_fd = open(argv[1], O_RDONLY)) < 0) {
        perror("zImage open");
        exit(3);
    }

    if ((out_fd = open(argv[2], (O_RDWR | O_CREAT | O_TRUNC), 0666)) < 0) {
        perror("bootfile open");
        exit(3);
    }

    cksum = 0;
    cp = (void *)&bt;
    for (i = 0; i < sizeof(bt) / sizeof(unsigned int); i++)
        cksum += *cp++;

    /* Assume zImage is an ELF file, and skip the 64K header.
    */
    if (read(in_fd, tmpbuf, sizeof(tmpbuf)) != sizeof(tmpbuf)) {
        fprintf(stderr, "%s is too small to be an ELF image\n",
                argv[1]);
        exit(4);
    }

    if (tmpbuf[0] != htonl(0x7f454c46)) {
        fprintf(stderr, "%s is not an ELF image\n", argv[1]);
        exit(4);
    }

    if (lseek(in_fd, (64 * 1024), SEEK_SET) < 0) {
        fprintf(stderr, "%s failed to seek in ELF image\n", argv[1]);
        exit(4);
    }

    nblks -= (64 * 1024) / IMGBLK;

    /* And away we go......
    */
    if (write(out_fd, &bt, sizeof(bt)) != sizeof(bt)) {
        perror("boot-image write");
        exit(5);
    }

    while (nblks-- > 0) {
        if (read(in_fd, tmpbuf, sizeof(tmpbuf)) < 0) {
            perror("zImage read");
            exit(5);
        }
        cp = tmpbuf;
        for (i = 0; i < sizeof(tmpbuf) / sizeof(unsigned int); i++)
            cksum += *cp++;
        if (write(out_fd, tmpbuf, sizeof(tmpbuf)) != sizeof(tmpbuf)) {
            perror("boot-image write");
            exit(5);
        }
    }

    /* rewrite the header with the computed checksum.
    */
    bt.bb_checksum = htonl(cksum);
    if (lseek(out_fd, 0, SEEK_SET) < 0) {
        perror("rewrite seek");
        exit(1);
    }
    if (write(out_fd, &bt, sizeof(bt)) != sizeof(bt)) {
        perror("boot-image rewrite");
        exit(1);
    }

    exit(0);
}