i386/loader/chain.c

	chain.c revision 199767f8919635c4928607450d9e0abb932109ce
/*
 * This file and its contents are supplied under the terms of the
 * Common Development and Distribution License ("CDDL"), version 1.0.
 * You may only use this file in accordance with the terms of version
 * 1.0 of the CDDL.
 *
 * A full copy of the text of the CDDL should have accompanied this
 * source.  A copy of the CDDL is also available via the Internet at
 * http://www.illumos.org/license/CDDL.
 */

/*
 * Copyright 2015 Toomas Soome <tsoome@me.com>
 */

/*
 * Chain loader to load BIOS boot block either from MBR or PBR.
 *
 * Note the boot block location 0000:7c000 conflicts with loader, so we need to
 * read in to temporary space and relocate on exec, when btx is stopped.
 */

#include <sys/cdefs.h>
#include <stand.h>
#include <sys/param.h>
#include <sys/linker.h>
#include <sys/diskmbr.h>

#include "bootstrap.h"
#include "libi386/libi386.h"
#include "btxv86.h"

/*
 * The MBR/VBR is located in first sector of disk/partition.
 * Read 512B to temporary location and set up relocation. Then
 * exec relocator.
 */
#define SECTOR_SIZE (512)

COMMAND_SET(chain, "chain", "chain load boot block from device", command_chain);

static int
command_chain(int argc, char *argv[])
{
    int fd, len, size = SECTOR_SIZE;
    struct stat st;
    vm_offset_t mem = 0x100000;
    uint32_t *uintptr = &relocater_data;
    struct i386_devdesc *rootdev;

    if (argc == 1) {
        command_errmsg = "no device or file name specified";
        return (CMD_ERROR);
    }
    if (argc != 2) {
        command_errmsg = "invalid trailing arguments";
        return (CMD_ERROR);
    }

    fd = open(argv[1], O_RDONLY);
    if (fd == -1) {
        command_errmsg = "open failed";
        return (CMD_ERROR);
    }

    len = strlen(argv[1]);
    if (argv[1][len-1] != ':') {
        if (fstat(fd, &st) == -1) {
            command_errmsg = "stat failed";
            close(fd);
            return (CMD_ERROR);
        }
        size = st.st_size;
    } else if (strncmp(argv[1], "disk", 4) != 0) {
        command_errmsg = "can only use disk device";
        close(fd);
        return (CMD_ERROR);
    }

    i386_getdev((void **)(&rootdev), argv[1], NULL);
    if (rootdev == NULL) {
        command_errmsg = "can't determine root device";
        close(fd);
        return (CMD_ERROR);
    }

    if (archsw.arch_readin(fd, mem, size) != size) {
        command_errmsg = "failed to read disk";
        close(fd);
        return (CMD_ERROR);
    }
    close(fd);

    if (argv[1][len-1] == ':' &&
        *((uint16_t *)PTOV(mem + DOSMAGICOFFSET)) != DOSMAGIC) {
        command_errmsg = "wrong magic";
        return (CMD_ERROR);
    }

    uintptr[0] = mem;
    uintptr[1] = 0x7C00;
    uintptr[2] = size;

    relocator_edx = bd_unit2bios(rootdev->d_unit);
    relocator_esi = relocater_size;
    relocator_ds = 0;
    relocator_es = 0;
    relocator_fs = 0;
    relocator_gs = 0;
    relocator_ss = 0;
    relocator_cs = 0;
    relocator_sp = 0x7C00;
    relocator_ip = 0x7C00;
    relocator_a20_enabled = 0;

    i386_copyin(relocater, 0x600, relocater_size);

    dev_cleanup();

    __exec((void *)0x600);

    panic("exec returned");
    return (CMD_ERROR);     /* not reached */
}