boot/common/mboot_extra.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 (c) 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright 2012 Nexenta Systems, Inc. All rights reserved.
 */

#include <stdio.h>
#include <errno.h>
#include <assert.h>
#include <unistd.h>
#include <libintl.h>
#include <sys/multiboot.h>
#include <sys/sysmacros.h>

#include "bblk_einfo.h"
#include "boot_utils.h"
#include "mboot_extra.h"

/*
 * Common functions to deal with the fake-multiboot encapsulation of the
 * bootblock and the location of the extra information area.
 */

/* mboot checksum routine. */
uint32_t
compute_checksum(char *data, uint32_t size)
{
    uint32_t    *ck_ptr;
    uint32_t    cksum = 0;
    int     i;

    ck_ptr = (uint32_t *)data;
    for (i = 0; i < size; i += sizeof (uint32_t))
        cksum += *ck_ptr++;

    return (-cksum);
}

/* Given a buffer, look for a multiboot header within it. */
int
find_multiboot(char *buffer, uint32_t buf_size, uint32_t *mboot_off)
{
    multiboot_header_t  *mboot;
    uint32_t        *iter;
    uint32_t        cksum;
    uint32_t        boundary;
    int         i = 0;

    iter = (uint32_t *)buffer;
    *mboot_off = 0;
    /* multiboot header has to be within the first 32K. */
    boundary = MBOOT_SCAN_SIZE;
    if (boundary > buf_size)
        boundary = buf_size;

    boundary = boundary - sizeof (multiboot_header_t);

    for (i = 0; i < boundary; i += 4, iter++) {

        mboot = (multiboot_header_t *)iter;
        if (mboot->magic != MB_HEADER_MAGIC)
            continue;

        /* Found magic signature -- check checksum. */
        cksum = -(mboot->flags + mboot->magic);
        if (mboot->checksum != cksum) {
            BOOT_DEBUG("multiboot magic found at %p, but checksum "
                "mismatches (is %x, should be %x)\n", mboot,
                mboot->checksum, cksum);
            continue;
        } else {
            if (!(mboot->flags & BB_MBOOT_AOUT_FLAG)) {
                BOOT_DEBUG("multiboot structure found, but no "
                    "AOUT kludge specified, skipping.\n");
                continue;
            } else {
                /* proper multiboot structure found. */
                *mboot_off = i;
                return (BC_SUCCESS);
            }
        }
    }

    return (BC_ERROR);
}

/*
 * Given a pointer to the extra information area (a sequence of bb_header_ext_t
 * + payload chunks), find the extended information structure.
 */
bblk_einfo_t *
find_einfo(char *extra, uint32_t size)
{
    bb_header_ext_t     *ext_header;
    bblk_einfo_t        *einfo;
    uint32_t        cksum;

    assert(extra != NULL);

    ext_header = (bb_header_ext_t *)extra;
    if (ext_header->size > size) {
        BOOT_DEBUG("Unable to find extended versioning information, "
            "data size too big\n");
        return (NULL);
    }

    cksum = compute_checksum(extra + sizeof (bb_header_ext_t),
        ext_header->size);
    BOOT_DEBUG("Extended information header checksum is %x\n", cksum);

    if (cksum != ext_header->checksum) {
        BOOT_DEBUG("Unable to find extended versioning information, "
            "data looks corrupted\n");
        return (NULL);
    }

    /*
     * Currently we only have one extra header so it must be encapsulating
     * the extended information structure.
     */
    einfo = (bblk_einfo_t *)(extra + sizeof (bb_header_ext_t));
    if (memcmp(einfo->magic, EINFO_MAGIC, EINFO_MAGIC_SIZE) != 0) {
        BOOT_DEBUG("Unable to read stage2 extended versioning "
            "information, wrong magic identifier\n");
        BOOT_DEBUG("Found %s, expected %s\n", einfo->magic,
            EINFO_MAGIC);
        return (NULL);
    }

    return (einfo);
}

/*
 * Given a pointer to the extra area, add the extended information structure
 * encapsulated by a bb_header_ext_t structure.
 */
void
add_einfo(char *extra, char *updt_str, bblk_hs_t *hs, uint32_t avail_space)
{
    bb_header_ext_t *ext_hdr;
    uint32_t    used_space;
    unsigned char   *dest;
    int     ret;

    assert(extra != NULL);

    if (updt_str == NULL) {
        BOOT_DEBUG("WARNING: no update string passed to "
            "add_stage2_einfo()\n");
        return;
    }

    /* Reserve space for the extra header. */
    ext_hdr = (bb_header_ext_t *)extra;
    dest = (unsigned char *)extra + sizeof (*ext_hdr);
    /* Place the extended information structure. */
    ret = prepare_and_write_einfo(dest, updt_str, hs, avail_space,
        &used_space);
    if (ret != 0) {
        (void) fprintf(stderr, gettext("Unable to write the extended "
            "versioning information\n"));
        return;
    }

    /* Fill the extended information associated header. */
    ext_hdr->size = P2ROUNDUP(used_space, 8);
    ext_hdr->checksum = compute_checksum((char *)dest, ext_hdr->size);
}