arch/ppc/boot/utils/addnote.c

   1 /*
   2  * Program to hack in a PT_NOTE program header entry in an ELF file.
   3  * This is needed for OF on RS/6000s to load an image correctly.
   4  * Note that OF needs a program header entry for the note, not an
   5  * ELF section.
   6  *
   7  * Copyright 2000 Paul Mackerras.
   8  *
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU General Public License
  11  * as published by the Free Software Foundation; either version
  12  * 2 of the License, or (at your option) any later version.
  13  *
  14  * Usage: addnote zImage
  15  */
  16 #include <stdio.h>
  17 #include <stdlib.h>
  18 #include <fcntl.h>
  19 #include <unistd.h>
  20 #include <string.h>
  21
  22 char arch[] = "PowerPC";
  23
  24 #define N_DESCR 6
  25 unsigned int descr[N_DESCR] = {
  26 #if 1
  27         /* values for IBM RS/6000 machines */
  28         0xffffffff,             /* real-mode = true */
  29         0x00c00000,             /* real-base, i.e. where we expect OF to be */
  30         0xffffffff,             /* real-size */
  31         0xffffffff,             /* virt-base */
  32         0xffffffff,             /* virt-size */
  33         0x4000,                 /* load-base */
  34 #else
  35         /* values for longtrail CHRP */
  36         0,                      /* real-mode = false */
  37         0xffffffff,             /* real-base */
  38         0xffffffff,             /* real-size */
  39         0xffffffff,             /* virt-base */
  40         0xffffffff,             /* virt-size */
  41         0x00600000,             /* load-base */
  42 #endif
  43 };
  44
  45 unsigned char buf[512];
  46
  47 #define GET_16BE(off)   ((buf[off] << 8) + (buf[(off)+1]))
  48 #define GET_32BE(off)   ((GET_16BE(off) << 16) + GET_16BE((off)+2))
  49
  50 #define PUT_16BE(off, v)        (buf[off] = ((v) >> 8) & 0xff, \
  51                                  buf[(off) + 1] = (v) & 0xff)
  52 #define PUT_32BE(off, v)        (PUT_16BE((off), (v) >> 16), \
  53                                  PUT_16BE((off) + 2, (v)))
  54
  55 /* Structure of an ELF file */
  56 #define E_IDENT         0       /* ELF header */
  57 #define E_PHOFF         28
  58 #define E_PHENTSIZE     42
  59 #define E_PHNUM         44
  60 #define E_HSIZE         52      /* size of ELF header */
  61
  62 #define EI_MAGIC        0       /* offsets in E_IDENT area */
  63 #define EI_CLASS        4
  64 #define EI_DATA         5
  65
  66 #define PH_TYPE         0       /* ELF program header */
  67 #define PH_OFFSET       4
  68 #define PH_FILESZ       16
  69 #define PH_HSIZE        32      /* size of program header */
  70
  71 #define PT_NOTE         4       /* Program header type = note */
  72
  73 #define ELFCLASS32      1
  74 #define ELFDATA2MSB     2
  75
  76 unsigned char elf_magic[4] = { 0x7f, 'E', 'L', 'F' };
  77
  78 int main(int ac, char **av)
  79 {
  80         int fd, n, i;
  81         int ph, ps, np;
  82         int nnote, ns;
  83
  84         if (ac != 2) {
  85                 fprintf(stderr, "Usage: %s elf-file\n", av[0]);
  86                 exit(1);
  87         }
  88         fd = open(av[1], O_RDWR);
  89         if (fd < 0) {
  90                 perror(av[1]);
  91                 exit(1);
  92         }
  93
  94         nnote = strlen(arch) + 1 + (N_DESCR + 3) * 4;
  95
  96         n = read(fd, buf, sizeof(buf));
  97         if (n < 0) {
  98                 perror("read");
  99                 exit(1);
 100         }
 101
 102         if (n < E_HSIZE || memcmp(&buf[E_IDENT+EI_MAGIC], elf_magic, 4) != 0)
 103                 goto notelf;
 104
 105         if (buf[E_IDENT+EI_CLASS] != ELFCLASS32
 106             || buf[E_IDENT+EI_DATA] != ELFDATA2MSB) {
 107                 fprintf(stderr, "%s is not a big-endian 32-bit ELF image\n",
 108                         av[1]);
 109                 exit(1);
 110         }
 111
 112         ph = GET_32BE(E_PHOFF);
 113         ps = GET_16BE(E_PHENTSIZE);
 114         np = GET_16BE(E_PHNUM);
 115         if (ph < E_HSIZE || ps < PH_HSIZE || np < 1)
 116                 goto notelf;
 117         if (ph + (np + 1) * ps + nnote > n)
 118                 goto nospace;
 119
 120         for (i = 0; i < np; ++i) {
 121                 if (GET_32BE(ph + PH_TYPE) == PT_NOTE) {
 122                         fprintf(stderr, "%s already has a note entry\n",
 123                                 av[1]);
 124                         exit(0);
 125                 }
 126                 ph += ps;
 127         }
 128
 129         /* XXX check that the area we want to use is all zeroes */
 130         for (i = 0; i < ps + nnote; ++i)
 131                 if (buf[ph + i] != 0)
 132                         goto nospace;
 133
 134         /* fill in the program header entry */
 135         ns = ph + ps;
 136         PUT_32BE(ph + PH_TYPE, PT_NOTE);
 137         PUT_32BE(ph + PH_OFFSET, ns);
 138         PUT_32BE(ph + PH_FILESZ, nnote);
 139
 140         /* fill in the note area we point to */
 141         /* XXX we should probably make this a proper section */
 142         PUT_32BE(ns, strlen(arch) + 1);
 143         PUT_32BE(ns + 4, N_DESCR * 4);
 144         PUT_32BE(ns + 8, 0x1275);
 145         strcpy(&buf[ns + 12], arch);
 146         ns += 12 + strlen(arch) + 1;
 147         for (i = 0; i < N_DESCR; ++i)
 148                 PUT_32BE(ns + i * 4, descr[i]);
 149
 150         /* Update the number of program headers */
 151         PUT_16BE(E_PHNUM, np + 1);
 152
 153         /* write back */
 154         lseek(fd, (long) 0, SEEK_SET);
 155         i = write(fd, buf, n);
 156         if (i < 0) {
 157                 perror("write");
 158                 exit(1);
 159         }
 160         if (i < n) {
 161                 fprintf(stderr, "%s: write truncated\n", av[1]);
 162                 exit(1);
 163         }
 164
 165         exit(0);
 166
 167  notelf:
 168         fprintf(stderr, "%s does not appear to be an ELF file\n", av[0]);
 169         exit(1);
 170
 171  nospace:
 172         fprintf(stderr, "sorry, I can't find space in %s to put the note\n",
 173                 av[0]);
 174         exit(1);
 175 }