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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.
 *
 * Usage: addnote zImage
 */
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

/* CHRP note section */
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 */
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\n", 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\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 + 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\n",
                        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\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);
}

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