/* ----------------------------------------------------------------------- *
*
* 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/errno_disk.h>
#include <disk/geom.h>
#include <disk/read.h>
#include <disk/util.h>
#include <disk/common.h>
/*
* TODO: implement file descriptors to cache metadata (geometry, ...)
*/
/**
* read_mbr - return a pointer to a malloced buffer containing the mbr
* @drive: Drive number
* @buf: Pre-allocated buffer for output
*
* Return the number of sectors read on success or -1 on failure.
* errno_disk contains the error number.
**/
int read_mbr(int drive, void *buf)
{
struct driveinfo drive_info;
drive_info.disk = drive;
/* MBR: lba = 0, 1 sector */
return read_sectors(&drive_info, buf, 0, 1);
}
/**
* dev_read - read from a drive
* @drive: Drive number
* @buf: Pre-allocated buffer for output
* @lba: Position to start reading from
* @sectors: Number of sectors to read
*
* High-level routine to read from a hard drive.
* Return the number of sectors read on success or -1 on failure.
* errno_disk contains the error number.
**/
int dev_read(int drive, void *buf, unsigned int lba, int sectors)
{
struct driveinfo drive_info;
drive_info.disk = drive;
return read_sectors(&drive_info, buf, lba, sectors);
}
/**
* read_sectors - read several sectors from disk
* @drive_info: driveinfo struct describing the disk
* @data: Pre-allocated buffer for output
* @lba: Position to read
* @sectors: Number of sectors to read
*
* Return the number of sectors read on success or -1 on failure.
* errno_disk contains the error number.
**/
int read_sectors(struct driveinfo *drive_info, void *data,
const unsigned int lba, const int sectors)
{
com32sys_t inreg, outreg;
struct ebios_dapa *dapa = __com32.cs_bounce;
void *buf = (char *)__com32.cs_bounce + sectors * SECTOR;
char *bufp = data;
if (get_drive_parameters(drive_info) == -1)
return -1;
memset(&inreg, 0, sizeof inreg);
if (drive_info->ebios) {
dapa->len = sizeof(*dapa);
dapa->count = sectors;
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.b[1] = 0x42; /* Extended read */
} else {
unsigned int c, h, s;
if (!drive_info->cbios) { // XXX errno
/* We failed to get the geometry */
if (lba)
return -1; /* Can only read 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)
return -1;
inreg.eax.w[0] = 0x0201; /* Read 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 read */
if (int13_retry(&inreg, &outreg)) {
errno_disk = outreg.eax.b[1];
return -1; /* Give up */
}
memcpy(bufp, buf, sectors * SECTOR);
return sectors;
}
