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mktree.c

/*
 * 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
char  tmpbuf[IMGBLK];

int main(int argc, char *argv[])
{
      int   in_fd, out_fd;
      int   nblks, i;
      uint  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(uint); i++)
            cksum += *cp++;

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

      if ((*(uint *)tmpbuf) != 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, IMGBLK) < 0) {
                  perror("zImage read");
                  exit(5);
            }
            cp = (uint *)tmpbuf;
            for (i=0; i<sizeof(tmpbuf)/sizeof(uint); 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);
}

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