149 lines
3.5 KiB
C
149 lines
3.5 KiB
C
/* ----------------------------------------------------------------------- *
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*
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* Copyright 2009 Pierre-Alexandre Meyer
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*
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* Some parts borrowed from chain.c32:
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*
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* Copyright 2003-2009 H. Peter Anvin - All Rights Reserved
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* Copyright 2009 Intel Corporation; author: H. Peter Anvin
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*
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* This file is part of Syslinux, and is made available under
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* the terms of the GNU General Public License version 2.
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*
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* ----------------------------------------------------------------------- */
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#include <com32.h>
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#include <stdlib.h>
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#include <string.h>
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#include <disk/errno_disk.h>
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#include <disk/geom.h>
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#include <disk/read.h>
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#include <disk/util.h>
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#include <disk/common.h>
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/*
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* TODO: implement file descriptors to cache metadata (geometry, ...)
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*/
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/**
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* read_mbr - return a pointer to a malloced buffer containing the mbr
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* @drive: Drive number
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* @buf: Pre-allocated buffer for output
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*
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* Return the number of sectors read on success or -1 on failure.
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* errno_disk contains the error number.
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**/
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int read_mbr(int drive, void *buf)
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{
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struct driveinfo drive_info;
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drive_info.disk = drive;
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/* MBR: lba = 0, 1 sector */
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return read_sectors(&drive_info, buf, 0, 1);
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}
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/**
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* dev_read - read from a drive
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* @drive: Drive number
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* @buf: Pre-allocated buffer for output
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* @lba: Position to start reading from
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* @sectors: Number of sectors to read
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*
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* High-level routine to read from a hard drive.
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* Return the number of sectors read on success or -1 on failure.
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* errno_disk contains the error number.
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**/
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int dev_read(int drive, void *buf, unsigned int lba, int sectors)
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{
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struct driveinfo drive_info;
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drive_info.disk = drive;
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return read_sectors(&drive_info, buf, lba, sectors);
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}
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/**
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* read_sectors - read several sectors from disk
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* @drive_info: driveinfo struct describing the disk
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* @data: Pre-allocated buffer for output
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* @lba: Position to read
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* @sectors: Number of sectors to read
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*
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* Return the number of sectors read on success or -1 on failure.
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* errno_disk contains the error number.
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**/
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int read_sectors(struct driveinfo *drive_info, void *data,
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const unsigned int lba, const int sectors)
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{
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com32sys_t inreg, outreg;
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struct ebios_dapa *dapa;
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void *buf;
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char *bufp = data;
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int rv = -1;
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if (get_drive_parameters(drive_info) == -1)
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return -1;
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buf = lmalloc(sectors * SECTOR);
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if (!buf)
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return -1;
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dapa = lmalloc(sizeof(*dapa));
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if (!dapa)
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goto fail;
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memset(&inreg, 0, sizeof inreg);
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if (drive_info->ebios) {
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dapa->len = sizeof(*dapa);
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dapa->count = sectors;
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dapa->off = OFFS(buf);
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dapa->seg = SEG(buf);
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dapa->lba = lba;
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inreg.esi.w[0] = OFFS(dapa);
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inreg.ds = SEG(dapa);
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inreg.edx.b[0] = drive_info->disk;
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inreg.eax.b[1] = 0x42; /* Extended read */
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} else {
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unsigned int c, h, s;
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if (!drive_info->cbios) { // XXX errno
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/* We failed to get the geometry */
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if (lba)
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goto fail; /* Can only read MBR */
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s = 1;
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h = 0;
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c = 0;
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} else
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lba_to_chs(drive_info, lba, &s, &h, &c);
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// XXX errno
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if (s > 63 || h > 256 || c > 1023)
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goto fail;
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inreg.eax.w[0] = 0x0201; /* Read one sector */
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inreg.ecx.b[1] = c & 0xff;
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inreg.ecx.b[0] = s + (c >> 6);
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inreg.edx.b[1] = h;
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inreg.edx.b[0] = drive_info->disk;
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inreg.ebx.w[0] = OFFS(buf);
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inreg.es = SEG(buf);
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}
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/* Perform the read */
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if (int13_retry(&inreg, &outreg)) {
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errno_disk = outreg.eax.b[1];
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goto fail; /* Give up */
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}
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memcpy(bufp, buf, sectors * SECTOR);
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rv = sectors;
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fail:
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lfree(dapa);
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lfree(buf);
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return rv;
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}
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