elfboot.c

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/*
 * Copyright (C) 2008 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * 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 any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <string.h>
#include <errno.h>
#include <elf.h>
#include <librm.h>
#include <ipxe/image.h>
#include <ipxe/elf.h>
#include <ipxe/features.h>
#include <ipxe/init.h>

/**
 * @file
 *
 * ELF bootable image
 *
 */

FEATURE ( FEATURE_IMAGE, "ELF", DHCP_EB_FEATURE_ELF, 1 );

/**
 * Execute ELF image
 *
 * @v image             ELF image
 * @ret rc              Return status code
 */
static int elfboot_exec ( struct image *image ) {
        physaddr_t entry;
        physaddr_t max;
        int rc;

        /* Load the image using core ELF support */
        if ( ( rc = elf_load ( image, &entry, &max ) ) != 0 ) {
                DBGC ( image, "ELF %s could not load: %s\n",
                       image->name, strerror ( rc ) );
                return rc;
        }

        /* An ELF image has no callback interface, so we need to shut
         * down before invoking it.
         */
        shutdown_boot();

        /* Jump to OS with flat physical addressing */
        DBGC ( image, "ELF %s starting execution at %lx\n",
               image->name, entry );
        __asm__ __volatile__ ( PHYS_CODE ( "pushl %%ebp\n\t" /* gcc bug */
                                           "call *%%edi\n\t"
                                           "popl %%ebp\n\t" /* gcc bug */ )
                               : : "D" ( entry )
                               : "eax", "ebx", "ecx", "edx", "esi", "memory" );

        DBGC ( image, "ELF %s returned\n", image->name );

        /* It isn't safe to continue after calling shutdown() */
        while ( 1 ) {}

        return -ECANCELED;  /* -EIMPOSSIBLE, anyone? */
}

/**
 * Check that ELF segment uses flat physical addressing
 *
 * @v image             ELF file
 * @v phdr              ELF program header
 * @v dest              Destination address
 * @ret rc              Return status code
 */
static int elfboot_check_segment ( struct image *image, const Elf_Phdr *phdr,
                                   physaddr_t dest ) {

        /* Check that ELF segment uses flat physical addressing */
        if ( phdr->p_vaddr != dest ) {
                DBGC ( image, "ELF %s uses virtual addressing (phys %x, virt "
                       "%x)\n", image->name, phdr->p_paddr, phdr->p_vaddr );
                return -ENOEXEC;
        }

        return 0;
}

/**
 * Probe ELF image
 *
 * @v image             ELF file
 * @ret rc              Return status code
 */
static int elfboot_probe ( struct image *image ) {
        const Elf32_Ehdr *ehdr;
        static const uint8_t e_ident[] = {
                [EI_MAG0]       = ELFMAG0,
                [EI_MAG1]       = ELFMAG1,
                [EI_MAG2]       = ELFMAG2,
                [EI_MAG3]       = ELFMAG3,
                [EI_CLASS]      = ELFCLASS32,
                [EI_DATA]       = ELFDATA2LSB,
                [EI_VERSION]    = EV_CURRENT,
        };
        physaddr_t entry;
        physaddr_t max;
        int rc;

        /* Read ELF header */
        if ( image->len < sizeof ( *ehdr ) ) {
                DBGC ( image, "ELF %s too short for ELF header\n",
                       image->name );
                return -ENOEXEC;
        }
        ehdr = image->data;
        if ( memcmp ( ehdr->e_ident, e_ident, sizeof ( e_ident ) ) != 0 ) {
                DBGC ( image, "ELF %s invalid identifier\n", image->name );
                return -ENOEXEC;
        }

        /* Check that this image uses flat physical addressing */
        if ( ( rc = elf_segments ( image, ehdr, elfboot_check_segment,
                                   &entry, &max ) ) != 0 ) {
                DBGC ( image, "ELF %s is not loadable: %s\n",
                       image->name, strerror ( rc ) );
                return rc;
        }

        return 0;
}

/** ELF image type */
struct image_type elfboot_image_type __image_type ( PROBE_NORMAL ) = {
        .name = "ELF",
        .probe = elfboot_probe,
        .exec = elfboot_exec,
};