/*
   * 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.
   *
   * Usage: addnote zImage
   */
  #include <stdio.h>
  #include <stdlib.h>
  #include <fcntl.h>
  #include <unistd.h>
  #include <string.h>
  
  /* CHRP note section */
  static const char arch[] = "PowerPC";
  
  #define N_DESCR	6
  unsigned int descr[N_DESCR] = {
  	0xffffffff,		/* real-mode = true */
  	0x02000000,		/* real-base, i.e. where we expect OF to be */
  	0xffffffff,		/* real-size */
  	0xffffffff,		/* virt-base */
  	0xffffffff,		/* virt-size */
  	0x4000,			/* load-base */
  };
  
  /* RPA note section */
  static const char rpaname[] = "IBM,RPA-Client-Config";
  
  /*
   * Note: setting ignore_my_client_config *should* mean that OF ignores
   * all the other fields, but there is a firmware bug which means that
   * it looks at the splpar field at least.  So these values need to be
   * reasonable.
   */
  #define N_RPA_DESCR	8
  unsigned int rpanote[N_RPA_DESCR] = {
  	0,			/* lparaffinity */
  	64,			/* min_rmo_size */
  	0,			/* min_rmo_percent */
  	40,			/* max_pft_size */
  	1,			/* splpar */
  	-1,			/* min_load */
  	0,			/* new_mem_def */
  	1,			/* ignore_my_client_config */
  };
  
  #define ROUNDUP(len)	(((len) + 3) & ~3)
  
  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, nnote2, ns;
  
  	if (ac != 2) {
  		fprintf(stderr, "Usage: %s elf-file
  ", av[0]);
  		exit(1);
  	}
  	fd = open(av[1], O_RDWR);
  	if (fd < 0) {
  		perror(av[1]);
  		exit(1);
  	}
  
  	nnote = 12 + ROUNDUP(strlen(arch) + 1) + sizeof(descr);
  	nnote2 = 12 + ROUNDUP(strlen(rpaname) + 1) + sizeof(rpanote);
  
  	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
  ",
  			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 + 2) * ps + nnote + nnote2 > 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
  ",
  				av[1]);
  			exit(0);
  		}
  		ph += ps;
  	}
  
  	/* XXX check that the area we want to use is all zeroes */
  	for (i = 0; i < 2 * ps + nnote + nnote2; ++i)
  		if (buf[ph + i] != 0)
  			goto nospace;
  
  	/* fill in the program header entry */
  	ns = ph + 2 * 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((char *) &buf[ns + 12], arch);
  	ns += 12 + strlen(arch) + 1;
  	for (i = 0; i < N_DESCR; ++i, ns += 4)
  		PUT_32BE(ns, descr[i]);
  
  	/* fill in the second program header entry and the RPA note area */
  	ph += ps;
  	PUT_32BE(ph + PH_TYPE, PT_NOTE);
  	PUT_32BE(ph + PH_OFFSET, ns);
  	PUT_32BE(ph + PH_FILESZ, nnote2);
  
  	/* fill in the note area we point to */
  	PUT_32BE(ns, strlen(rpaname) + 1);
  	PUT_32BE(ns + 4, sizeof(rpanote));
  	PUT_32BE(ns + 8, 0x12759999);
  	strcpy((char *) &buf[ns + 12], rpaname);
  	ns += 12 + ROUNDUP(strlen(rpaname) + 1);
  	for (i = 0; i < N_RPA_DESCR; ++i, ns += 4)
  		PUT_32BE(ns, rpanote[i]);
  
  	/* Update the number of program headers */
  	PUT_16BE(E_PHNUM, np + 2);
  
  	/* 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
  ", av[1]);
  		exit(1);
  	}
  
  	exit(0);
  
   notelf:
  	fprintf(stderr, "%s does not appear to be an ELF file
  ", av[1]);
  	exit(1);
  
   nospace:
  	fprintf(stderr, "sorry, I can't find space in %s to put the note
  ",
  		av[1]);
  	exit(1);
  }