/*
 *  addnote.c - Program to hack in a PT_NOTE program header entry in an ELF file.
 *             This is needed for OF on RS/6000s to load an image correctly.
 *             Note that OF needs a program header entry for the note, not an
 *             ELF section.
 *
 *  Copyright 2000 Paul Mackerras.
 *
 *  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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

/* Usage: addnote zImage */

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

char arch[] = "PowerPC";

#define N_DESCR	6
unsigned int descr[N_DESCR] = {
     0xffffffff,		/* real-mode = true */
     0x00c00000,		/* real-base, i.e. where we expect OF to be */
     0xffffffff,		/* real-size */
     0xffffffff,		/* virt-base */
     0xffffffff,		/* virt-size */
     0x4000,			/* load-base */
};

unsigned char buf[512];

#define GET_16BE(off)	((buf[off] << 8) + (buf[(off)+1]))
#define GET_32BE(off)	((GET_16BE(off) << 16) + GET_16BE((off)+2))
#define PUT_16BE(off, v)	(buf[off] = ((v) >> 8) & 0xff, \
			 buf[(off) + 1] = (v) & 0xff)
#define PUT_32BE(off, v)	(PUT_16BE((off), (v) >> 16), \
				 PUT_16BE((off) + 2, (v)))

/* Structure of an ELF file */
#define E_IDENT		0	/* ELF header */
#define	E_PHOFF		28
#define E_PHENTSIZE	42
#define E_PHNUM		44
#define E_HSIZE		52	/* size of ELF header */

#define EI_MAGIC	0	/* offsets in E_IDENT area */
#define EI_CLASS	4
#define EI_DATA		5

#define PH_TYPE		0	/* ELF program header */
#define PH_OFFSET	4
#define PH_FILESZ	16
#define PH_HSIZE	32	/* size of program header */

#define PT_NOTE		4	/* Program header type = note */

#define ELFCLASS32	1
#define ELFDATA2MSB	2

unsigned char elf_magic[4] = { 0x7f, 'E', 'L', 'F' };

int
main(int ac, char **av)
{
     int fd, n, i;
     int ph, ps, np;
     int nnote, ns;

     if (ac != 2) {
	  fprintf(stderr, "Usage: %s elf-file\n", av[0]);
	  exit(1);
     }
     fd = open(av[1], O_RDWR);
     if (fd < 0) {
	  perror(av[1]);
	  exit(1);
     }

     nnote = strlen(arch) + 1 + (N_DESCR + 3) * 4;

     n = read(fd, buf, sizeof(buf));
     if (n < 0) {
	  perror("read");
	  exit(1);
     }

     if (n < E_HSIZE || memcmp(&buf[E_IDENT+EI_MAGIC], elf_magic, 4) != 0)
	  goto notelf;

     if (buf[E_IDENT+EI_CLASS] != ELFCLASS32
	 || buf[E_IDENT+EI_DATA] != ELFDATA2MSB) {
	  fprintf(stderr, "%s is not a big-endian 32-bit ELF image\n",
		  av[1]);
	  exit(1);
     }

     ph = GET_32BE(E_PHOFF);
     ps = GET_16BE(E_PHENTSIZE);
     np = GET_16BE(E_PHNUM);
     if (ph < E_HSIZE || ps < PH_HSIZE || np < 1)
	  goto notelf;
     if (ph + (np + 1) * ps + nnote > n)
	  goto nospace;

     for (i = 0; i < np; ++i) {
	  if (GET_32BE(ph + PH_TYPE) == PT_NOTE) {
	       fprintf(stderr, "%s already has a note entry\n",
		       av[1]);
	       exit(0);
	  }
	  ph += ps;
     }

     /* XXX check that the area we want to use is all zeroes */
     for (i = 0; i < ps + nnote; ++i)
	  if (buf[ph + i] != 0)
	       goto nospace;

     /* fill in the program header entry */
     ns = ph + ps;
     PUT_32BE(ph + PH_TYPE, PT_NOTE);
     PUT_32BE(ph + PH_OFFSET, ns);
     PUT_32BE(ph + PH_FILESZ, nnote);

     /* fill in the note area we point to */
     /* XXX we should probably make this a proper section */
     PUT_32BE(ns, strlen(arch) + 1);
     PUT_32BE(ns + 4, N_DESCR * 4);
     PUT_32BE(ns + 8, 0x1275);
     strcpy(&buf[ns + 12], arch);
     ns += 12 + strlen(arch) + 1;
     for (i = 0; i < N_DESCR; ++i)
	  PUT_32BE(ns + i * 4, descr[i]);

     /* Update the number of program headers */
     PUT_16BE(E_PHNUM, np + 1);

     /* write back */
     lseek(fd, (long) 0, SEEK_SET);
     i = write(fd, buf, n);
     if (i < 0) {
	  perror("write");
	  exit(1);
     }
     if (i < n) {
	  fprintf(stderr, "%s: write truncated\n", av[1]);
	  exit(1);
     }

     exit(0);

notelf:
     fprintf(stderr, "%s does not appear to be an ELF file\n", av[1]);
     exit(1);

nospace:
     fprintf(stderr, "sorry, I can't find space in %s to put the note\n",
	     av[1]);
     exit(1);
}

/* 
 * Local variables:
 * c-file-style: "k&r"
 * c-basic-offset: 5
 * End:
 */
