tools/mbh_patch/mbh_patch.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#include <strings.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/inttypes.h>
#include <sys/elf.h>
#include <sys/elf_notes.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include "sys/multiboot.h"

static char *pname;
static char *fname;
static char *image; /* pointer to the ELF file in memory */

#define ELFSEEK(offset) ((void *)(image + offset))

/*
 * patch the load address / entry address
 * Find the physical load address of the 1st PT_LOAD segment.
 * Find the amount that e_entry exceeds that amount.
 * Now go back and subtract the excess from the p_paddr of the LOAD segment.
 */
static int
patch64(Elf64_Ehdr *eh)
{
    Elf64_Phdr      *phdr;
    caddr_t         phdrs = NULL;
    int         ndx, mem;
    multiboot_header_t  *mbh;

    /*
     * Verify some ELF basics - this must be an executable with program
     * headers.
     */
    if (eh->e_type != ET_EXEC) {
        (void) fprintf(stderr, "%s: %s: not ET_EXEC, e_type = 0x%x\n",
            pname, fname, eh->e_type);
        return (1);
    }
    if ((eh->e_phnum == 0) || (eh->e_phoff == 0)) {
        (void) fprintf(stderr, "%s: %s: no program headers\n", pname,
            fname);
        return (1);
    }

    /*
     * Get the program headers.
     */
    if ((phdrs = ELFSEEK(eh->e_phoff)) == NULL) {
        (void) fprintf(stderr, "%s: %s: failed to get %d program "
            "hdrs\n", pname, fname, eh->e_phnum);
        return (1);
    }

    /*
     * Look for multiboot header.  It must be 32-bit aligned and
     * completely contained in the 1st 8K of the file.
     */
    for (mem = 0; mem < 8192 - sizeof (multiboot_header_t); mem += 4) {
        mbh = ELFSEEK(mem);
        if (mbh->magic == MB_HEADER_MAGIC)
            break;
    }

    if (mem >= 8192 - sizeof (multiboot_header_t)) {
        (void) fprintf(stderr, "%s: %s: Didn't find multiboot header\n",
            pname, fname);
        return (1);
    }

    /*
     * Find the 1:1 mapped PT_LOAD section
     */
    for (ndx = 0; ndx < eh->e_phnum; ndx++) {
        /*LINTED [ELF program header alignment]*/
        phdr = (Elf64_Phdr *)(phdrs + eh->e_phentsize * ndx);

        /*
         * Find the low memory 1:1 PT_LOAD section!
         */
        if (phdr->p_type != PT_LOAD)
            continue;

        if (phdr->p_memsz == 0)
            continue;

        if (phdr->p_paddr != phdr->p_vaddr)
            continue;

        /*
         * Make sure the multiboot header is part of the first PT_LOAD
         * segment, and that the executables entry point starts at the
         * same segment.
         */
        if ((mem < phdr->p_offset) ||
            (mem >= (phdr->p_offset + phdr->p_filesz))) {
            (void) fprintf(stderr, "%s: %s: identity mapped "
                "PT_LOAD wasn't 1st PT_LOAD\n", pname, fname);
            return (1);
        }
        if (eh->e_entry != phdr->p_paddr) {
            (void) fprintf(stderr, "%s: %s: entry != paddr\n",
                pname, fname);
            return (1);
        }

        /*
         * Patch the multiboot header fields to get entire file loaded.
         * Grub uses the MB header for 64 bit loading.
         */
        mbh->load_addr = phdr->p_paddr - phdr->p_offset;
        mbh->entry_addr = phdr->p_paddr;
        mbh->header_addr = mbh->load_addr + mem;
#ifdef VERBOSE
        (void) printf("  %s: ELF64 MB header patched\n", fname);
        (void) printf("\tload_addr now:   0x%x\n", mbh->load_addr);
        (void) printf("\tentry_addr now:  0x%x\n", mbh->entry_addr);
        (void) printf("\theader_addr now: 0x%x\n", mbh->header_addr);
#endif
        return (0);
    }

    (void) fprintf(stderr, "%s: %s: Didn't find 1:1 mapped PT_LOAD "
        "section\n", pname, fname);
    return (1);
}

int
main(int argc, char **argv)
{
    int fd;
    uchar_t *ident;
    void    *hdr = NULL;

    /*
     * we expect one argument -- the elf file
     */
    if (argc != 2) {
        (void) fprintf(stderr, "usage: %s <unix-elf-file>\n", argv[0]);
        return (1);
    }

    pname = strrchr(argv[0], '/');
    if (pname == NULL)
        pname = argv[0];
    else
        ++pname;

    fname = argv[1];
    if ((fd = open(fname, O_RDWR)) < 0) {
        (void) fprintf(stderr, "%s: open(%s, O_RDWR) failed: %s\n",
            pname, fname, strerror(errno));
        return (1);
    }

    /*
     * mmap just the 1st 8K -- since that's where the GRUB
     * multiboot header must be located.
     */
    image = mmap(NULL, 8192, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
    if (image == MAP_FAILED) {
        (void) fprintf(stderr, "%s: mmap() of %s failed: %s\n",
            pname, fname, strerror(errno));
        return (1);
    }

    ident = ELFSEEK(0);
    if (ident[EI_MAG0] != ELFMAG0 || ident[EI_MAG1] != ELFMAG1 ||
        ident[EI_MAG2] != ELFMAG2 || ident[EI_MAG3] != ELFMAG3) {
        (void) fprintf(stderr, "%s: %s: not an ELF file!\n", pname,
            fname);
        return (1);
    }

    if (ident[EI_CLASS] == ELFCLASS64) {
        hdr = ELFSEEK(0);
        return (patch64(hdr));
    }
    if (ident[EI_CLASS] != ELFCLASS32) {
        (void) fprintf(stderr, "%s: Unknown ELF class 0x%x\n", pname,
            ident[EI_CLASS]);
        return (1);
    }
    return (0);
}