arch/ppc64/boot/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         0xffffffff,             /* real-mode = true */
  27         0x00c00000,             /* real-base, i.e. where we expect OF to be */
  28         0xffffffff,             /* real-size */
  29         0xffffffff,             /* virt-base */
  30         0xffffffff,             /* virt-size */
  31         0x4000,                 /* load-base */
  32 };
  33
  34 unsigned char buf[512];
  35
  36 #define GET_16BE(off)   ((buf[off] << 8) + (buf[(off)+1]))
  37 #define GET_32BE(off)   ((GET_16BE(off) << 16) + GET_16BE((off)+2))
  38
  39 #define PUT_16BE(off, v)        (buf[off] = ((v) >> 8) & 0xff, \
  40                                  buf[(off) + 1] = (v) & 0xff)
  41 #define PUT_32BE(off, v)        (PUT_16BE((off), (v) >> 16), \
  42                                  PUT_16BE((off) + 2, (v)))
  43
  44 /* Structure of an ELF file */
  45 #define E_IDENT         0       /* ELF header */
  46 #define E_PHOFF         28
  47 #define E_PHENTSIZE     42
  48 #define E_PHNUM         44
  49 #define E_HSIZE         52      /* size of ELF header */
  50
  51 #define EI_MAGIC        0       /* offsets in E_IDENT area */
  52 #define EI_CLASS        4
  53 #define EI_DATA         5
  54
  55 #define PH_TYPE         0       /* ELF program header */
  56 #define PH_OFFSET       4
  57 #define PH_FILESZ       16
  58 #define PH_HSIZE        32      /* size of program header */
  59
  60 #define PT_NOTE         4       /* Program header type = note */
  61
  62 #define ELFCLASS32      1
  63 #define ELFDATA2MSB     2
  64
  65 unsigned char elf_magic[4] = { 0x7f, 'E', 'L', 'F' };
  66
  67 int
  68 main(int ac, char **av)
  69 {
  70         int fd, n, i;
  71         int ph, ps, np;
  72         int nnote, ns;
  73
  74         if (ac != 2) {
  75                 fprintf(stderr, "Usage: %s elf-file\n", av[0]);
  76                 exit(1);
  77         }
  78         fd = open(av[1], O_RDWR);
  79         if (fd < 0) {
  80                 perror(av[1]);
  81                 exit(1);
  82         }
  83
  84         nnote = strlen(arch) + 1 + (N_DESCR + 3) * 4;
  85
  86         n = read(fd, buf, sizeof(buf));
  87         if (n < 0) {
  88                 perror("read");
  89                 exit(1);
  90         }
  91
  92         if (n < E_HSIZE || memcmp(&buf[E_IDENT+EI_MAGIC], elf_magic, 4) != 0)
  93                 goto notelf;
  94
  95         if (buf[E_IDENT+EI_CLASS] != ELFCLASS32
  96             || buf[E_IDENT+EI_DATA] != ELFDATA2MSB) {
  97                 fprintf(stderr, "%s is not a big-endian 32-bit ELF image\n",
  98                         av[1]);
  99                 exit(1);
 100         }
 101
 102         ph = GET_32BE(E_PHOFF);
 103         ps = GET_16BE(E_PHENTSIZE);
 104         np = GET_16BE(E_PHNUM);
 105         if (ph < E_HSIZE || ps < PH_HSIZE || np < 1)
 106                 goto notelf;
 107         if (ph + (np + 1) * ps + nnote > n)
 108                 goto nospace;
 109
 110         for (i = 0; i < np; ++i) {
 111                 if (GET_32BE(ph + PH_TYPE) == PT_NOTE) {
 112                         fprintf(stderr, "%s already has a note entry\n",
 113                                 av[1]);
 114                         exit(0);
 115                 }
 116                 ph += ps;
 117         }
 118
 119         /* XXX check that the area we want to use is all zeroes */
 120         for (i = 0; i < ps + nnote; ++i)
 121                 if (buf[ph + i] != 0)
 122                         goto nospace;
 123
 124         /* fill in the program header entry */
 125         ns = ph + ps;
 126         PUT_32BE(ph + PH_TYPE, PT_NOTE);
 127         PUT_32BE(ph + PH_OFFSET, ns);
 128         PUT_32BE(ph + PH_FILESZ, nnote);
 129
 130         /* fill in the note area we point to */
 131         /* XXX we should probably make this a proper section */
 132         PUT_32BE(ns, strlen(arch) + 1);
 133         PUT_32BE(ns + 4, N_DESCR * 4);
 134         PUT_32BE(ns + 8, 0x1275);
 135         strcpy(&buf[ns + 12], arch);
 136         ns += 12 + strlen(arch) + 1;
 137         for (i = 0; i < N_DESCR; ++i)
 138                 PUT_32BE(ns + i * 4, descr[i]);
 139
 140         /* Update the number of program headers */
 141         PUT_16BE(E_PHNUM, np + 1);
 142
 143         /* write back */
 144         lseek(fd, (long) 0, SEEK_SET);
 145         i = write(fd, buf, n);
 146         if (i < 0) {
 147                 perror("write");
 148                 exit(1);
 149         }
 150         if (i < n) {
 151                 fprintf(stderr, "%s: write truncated\n", av[1]);
 152                 exit(1);
 153         }
 154
 155         exit(0);
 156
 157  notelf:
 158         fprintf(stderr, "%s does not appear to be an ELF file\n", av[0]);
 159         exit(1);
 160
 161  nospace:
 162         fprintf(stderr, "sorry, I can't find space in %s to put the note\n",
 163                 av[0]);
 164         exit(1);
 165 }