/*
 * 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);
}