/*

     Simple utility to make a single-image install kernel with initial ramdisk
     for Sparc tftpbooting without need to set up nfs.

     Copyright (C) 1996,1997 Jakub Jelinek (jj@sunsite.mff.cuni.cz)

     Pete Zaitcev <zaitcev@yahoo.com> endian fixes for cross-compiles, 2000.

     Copyright (C) 2011 Sam Ravnborg <sam@ravnborg.org>

  
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation; either version 2 of the License, or
     (at your option) any later version.

     This program is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.
  
     You should have received a copy of the GNU General Public License
     along with this program; if not, write to the Free Software
     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */

  
  #include <dirent.h>
  #include <stdlib.h>

  #include <string.h>

  #include <unistd.h>

  #include <ctype.h>
  #include <errno.h>
  #include <fcntl.h>

  #include <stdio.h>

  #include <sys/types.h>
  #include <sys/stat.h>
  
  /*
   * Note: run this on an a.out kernel (use elftoaout for it),
   * as PROM looks for a.out image only.
   */

  #define AOUT_TEXT_OFFSET   32

  static int is64bit = 0;
  
  /* align to power-of-two size */
  static int align(int n)
  {
  	if (is64bit)
  		return (n + 0x1fff) & ~0x1fff;
  	else
  		return (n + 0xfff) & ~0xfff;
  }

  /* read two bytes as big endian */

  static unsigned short ld2(char *p)

  {
  	return (p[0] << 8) | p[1];
  }

  /* save 4 bytes as big endian */

  static void st4(char *p, unsigned int x)

  {
  	p[0] = x >> 24;
  	p[1] = x >> 16;
  	p[2] = x >> 8;
  	p[3] = x;
  }

  static void die(const char *str)
  {
  	perror(str);
  	exit(1);
  }

  static void usage(void)

  {
  	/* fs_img.gz is an image of initial ramdisk. */

  	fprintf(stderr, "Usage: piggyback bits vmlinux.aout System.map fs_img.gz
  ");

  	fprintf(stderr, "\tKernel image will be modified in place.
  ");
  	exit(1);
  }

  static int start_line(const char *line)

  {

  	if (strcmp(line + 8, " T _start
  ") == 0)

  		return 1;

  	else if (strcmp(line + 16, " T _start
  ") == 0)

  		return 1;
  	return 0;
  }
  
  static int end_line(const char *line)
  {
  	if (strcmp(line + 8, " A _end
  ") == 0)
  		return 1;
  	else if (strcmp (line + 16, " A _end
  ") == 0)
  		return 1;
  	return 0;
  }
  
  /*
   * Find address for start and end in System.map.
   * The file looks like this:

   * f0004000 T _start

   * f0379f79 A _end
   * 1234567890123456
   * ^coloumn 1
   * There is support for 64 bit addresses too.
   *
   * Return 0 if either start or end is not found
   */

  static int get_start_end(const char *filename, unsigned int *start,
                                                 unsigned int *end)

  {
  	FILE *map;
  	char buffer[1024];
  
  	*start = 0;
  	*end = 0;
  	map = fopen(filename, "r");
  	if (!map)
  		die(filename);
  	while (fgets(buffer, 1024, map)) {
  		if (start_line(buffer))
  			*start = strtoul(buffer, NULL, 16);
  		else if (end_line(buffer))
  			*end = strtoul(buffer, NULL, 16);
  	}
  	fclose (map);
  
  	if (*start == 0 || *end == 0)
  		return 0;
  
  	return 1;

  }

  #define LOOKBACK (128 * 4)
  #define BUFSIZE 1024
  /*
   * Find the HdrS entry from head_32/head_64.
   * We check if it is at the beginning of the file (sparc64 case)
   * and if not we search for it.
   * When we search do so in steps of 4 as HdrS is on a 4-byte aligned
   * address (it is on same alignment as sparc instructions)
   * Return the offset to the HdrS entry (as off_t)
   */
  static off_t get_hdrs_offset(int kernelfd, const char *filename)
  {
  	char buffer[BUFSIZE];
  	off_t offset;
  	int i;
  
  	if (lseek(kernelfd, 0, SEEK_SET) < 0)
  		die("lseek");
  	if (read(kernelfd, buffer, BUFSIZE) != BUFSIZE)
  		die(filename);
  
  	if (buffer[40] == 'H' && buffer[41] == 'd' &&
  	    buffer[42] == 'r' && buffer[43] == 'S') {
  		return 40;
  	} else {
  		/*  Find the gokernel label */
  		/* Decode offset from branch instruction */
  		offset = ld2(buffer + AOUT_TEXT_OFFSET + 2) << 2;
  		/* Go back 512 bytes so we do not miss HdrS */
  		offset -= LOOKBACK;
  		/* skip a.out header */
  		offset += AOUT_TEXT_OFFSET;
  		if (lseek(kernelfd, offset, SEEK_SET) < 0)
  			die("lseek");
  		if (read(kernelfd, buffer, BUFSIZE) != BUFSIZE)
  			die(filename);
  
  		for (i = 0; i < LOOKBACK; i += 4) {
  			if (buffer[i + 0] == 'H' && buffer[i + 1] == 'd' &&
  			    buffer[i + 2] == 'r' && buffer[i + 3] == 'S') {
  				return offset + i;
  			}
  		}
  	}
  	fprintf (stderr, "Couldn't find headers signature in %s
  ", filename);
  	exit(1);
  }

  int main(int argc,char **argv)
  {
  	static char aout_magic[] = { 0x01, 0x03, 0x01, 0x07 };

  	char buffer[1024];
  	unsigned int i, start, end;
  	off_t offset;

  	struct stat s;
  	int image, tail;

  	if (argc != 5)

  		usage();

  	if (strcmp(argv[1], "64") == 0)
  		is64bit = 1;
  	if (stat (argv[4], &s) < 0)
  		die(argv[4]);

  	if (!get_start_end(argv[3], &start, &end)) {

  		fprintf(stderr, "Could not determine start and end from %s
  ",
  		        argv[3]);

  		exit(1);
  	}

  	if ((image = open(argv[2], O_RDWR)) < 0)
  		die(argv[2]);

  	if (read(image, buffer, 512) != 512)

  		die(argv[2]);

  	if (memcmp(buffer, aout_magic, 4) != 0) {
  		fprintf (stderr, "Not a.out. Don't blame me.
  ");

  		exit(1);
  	}

  	/*

  	 * We need to fill in values for
  	 * sparc_ramdisk_image + sparc_ramdisk_size

  	 * To locate these symbols search for the "HdrS" text which appear
  	 * in the image a little before the gokernel symbol.
  	 * See definition of these in init_32.S
  	 */

  	offset = get_hdrs_offset(image, argv[2]);
  	/* skip HdrS + LINUX_VERSION_CODE + HdrS version */
  	offset += 10;

  	if (lseek(image, offset, 0) < 0)
  		die("lseek");

  	/*
  	 * root_flags = 0
  	 * root_dev = 1 (RAMDISK_MAJOR)
  	 * ram_flags = 0
  	 * sparc_ramdisk_image = "PAGE aligned address after _end")
  	 * sparc_ramdisk_size = size of image
  	 */

  	st4(buffer, 0);
  	st4(buffer + 4, 0x01000000);

  	st4(buffer + 8, align(end + 32));

  	st4(buffer + 12, s.st_size);

  	if (write(image, buffer + 2, 14) != 14)

  		die(argv[2]);

  	/* For sparc64 update a_text and clear a_data + a_bss */
  	if (is64bit)
  	{
  		if (lseek(image, 4, 0) < 0)
  			die("lseek");
  		/* a_text */
  		st4(buffer, align(end + 32 + 8191) - (start & ~0x3fffffUL) +
  		            s.st_size);
  		/* a_data */
  		st4(buffer + 4, 0);
  		/* a_bss */
  		st4(buffer + 8, 0);
  		if (write(image, buffer, 12) != 12)
  			die(argv[2]);
  	}

  	/* seek page aligned boundary in the image file and add boot image */

  	if (lseek(image, AOUT_TEXT_OFFSET - start + align(end + 32), 0) < 0)

  		die("lseek");

  	if ((tail = open(argv[4], O_RDONLY)) < 0)
  		die(argv[4]);

  	while ((i = read(tail, buffer, 1024)) > 0)

  		if (write(image, buffer, i) != i)

  			die(argv[2]);

  	if (close(image) < 0)
  		die("close");
  	if (close(tail) < 0)
  		die("close");
  	return 0;

  }