addnote.c

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/*
 * 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\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);
}