source: bootcd/isolinux/syslinux-6.03/com32/gpllib/disk/write.c

/* ----------------------------------------------------------------------- *
 *
 *   Copyright 2009 Pierre-Alexandre Meyer
 *
 *   Some parts borrowed from chain.c32:
 *
 *   Copyright 2003-2009 H. Peter Anvin - All Rights Reserved
 *   Copyright 2009 Intel Corporation; author: H. Peter Anvin
 *
 *   This file is part of Syslinux, and is made available under
 *   the terms of the GNU General Public License version 2.
 *
 * ----------------------------------------------------------------------- */

#include <com32.h>
#include <stdlib.h>
#include <string.h>

#include <disk/common.h>
#include <disk/errno_disk.h>
#include <disk/read.h>
#include <disk/util.h>
#include <disk/write.h>

/**
 * write_sectors - write several sectors from disk
 * @drive_info:         driveinfo struct describing the disk
 * @lba:                Position to write
 * @data:               Buffer to write
 * @size:               Size of the buffer (number of sectors)
 *
 * Return the number of sectors write on success or -1 on failure.
 * errno_disk contains the error number.
 **/
int write_sectors(const struct driveinfo *drive_info, const unsigned int lba,
                  const void *data, const int size)
{
    com32sys_t inreg, outreg;
    struct ebios_dapa *dapa;
    void *buf;
    int rv = -1;

    buf = lmalloc(size);
    if (!buf)
        return -1;

    dapa = lmalloc(sizeof(*dapa));
    if (!dapa)
        goto out;

    memcpy(buf, data, size);
    memset(&inreg, 0, sizeof inreg);

    if (drive_info->ebios) {
        dapa->len = sizeof(*dapa);
        dapa->count = size;
        dapa->off = OFFS(buf);
        dapa->seg = SEG(buf);
        dapa->lba = lba;

        inreg.esi.w[0] = OFFS(dapa);
        inreg.ds = SEG(dapa);
        inreg.edx.b[0] = drive_info->disk;
        inreg.eax.w[0] = 0x4300;        /* Extended write */
    } else {
        unsigned int c, h, s;

        if (!drive_info->cbios) {       // XXX errno
            /* We failed to get the geometry */
            if (lba)
                goto out;       /* Can only write MBR */

            s = 1;
            h = 0;
            c = 0;
        } else
            lba_to_chs(drive_info, lba, &s, &h, &c);

        // XXX errno
        if (s > 63 || h > 256 || c > 1023)
            goto out;

        inreg.eax.w[0] = 0x0301;        /* Write one sector */
        inreg.ecx.b[1] = c & 0xff;
        inreg.ecx.b[0] = s + (c >> 6);
        inreg.edx.b[1] = h;
        inreg.edx.b[0] = drive_info->disk;
        inreg.ebx.w[0] = OFFS(buf);
        inreg.es = SEG(buf);
    }

    /* Perform the write */
    if (int13_retry(&inreg, &outreg)) {
        errno_disk = outreg.eax.b[1];   /* Give up */
    } else
        rv = size;
out:
    lfree(dapa);
    lfree(buf);
    return rv;
}

/**
 * write_verify_sectors - write several sectors from disk
 * @drive_info:         driveinfo struct describing the disk
 * @lba:                Position to write
 * @data:               Buffer to write
 **/
int write_verify_sector(struct driveinfo *drive_info,
                        const unsigned int lba, const void *data)
{
    return write_verify_sectors(drive_info, lba, data, SECTOR);
}

/**
 * write_verify_sectors - write several sectors from disk
 * @drive_info:         driveinfo struct describing the disk
 * @lba:                Position to write
 * @data:               Buffer to write
 * @size:               Size of the buffer (number of sectors)
 **/
int write_verify_sectors(struct driveinfo *drive_info,
                         const unsigned int lba,
                         const void *data, const int size)
{
    char *rb = malloc(SECTOR * size * sizeof(char));
    int status;

    if (write_sectors(drive_info, lba, data, size) == -1)
        return -1;              /* Write failure */

    if (read_sectors(drive_info, rb, lba, size) == -1)
        return -1;              /* Readback failure */

    status = memcmp(data, rb, SECTOR * size);
    free(rb);
    return status ? -1 : 0;
}