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xNBA/src/arch/i386/interface/pcbios/int13.c
Michael Brown 2cf1e33df1 Split bootsector execution code out into bootsector.c. 
Added basic El Torito ISO image boot capability
2007-01-29 04:21:38 +00:00

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/*
* Copyright (C) 2006 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <stdint.h>
#include <limits.h>
#include <byteswap.h>
#include <errno.h>
#include <assert.h>
#include <gpxe/list.h>
#include <gpxe/blockdev.h>
#include <realmode.h>
#include <bios.h>
#include <biosint.h>
#include <bootsector.h>
#include <int13.h>
/** @file
*
* INT 13 emulation
*
* This module provides a mechanism for exporting block devices via
* the BIOS INT 13 disk interrupt interface.
*
*/
/** Vector for chaining to other INT 13 handlers */
static struct segoff __text16 ( int13_vector );
#define int13_vector __use_text16 ( int13_vector )
/** Assembly wrapper */
extern void int13_wrapper ( void );
/** List of registered emulated drives */
static LIST_HEAD ( drives );
/**
* INT 13, 00 - Reset disk system
*
* @v drive Emulated drive
* @ret status Status code
*/
static int int13_reset ( struct int13_drive *drive __unused,
struct i386_all_regs *ix86 __unused ) {
DBG ( "Reset drive\n" );
return 0;
}
/**
* INT 13, 01 - Get status of last operation
*
* @v drive Emulated drive
* @ret status Status code
*/
static int int13_get_last_status ( struct int13_drive *drive,
struct i386_all_regs *ix86 __unused ) {
DBG ( "Get status of last operation\n" );
return drive->last_status;
}
/**
* Read / write sectors
*
* @v drive Emulated drive
* @v al Number of sectors to read or write (must be nonzero)
* @v ch Low bits of cylinder number
* @v cl (bits 7:6) High bits of cylinder number
* @v cl (bits 5:0) Sector number
* @v dh Head number
* @v es:bx Data buffer
* @v io Read / write method
* @ret status Status code
* @ret al Number of sectors read or written
*/
static int int13_rw_sectors ( struct int13_drive *drive,
struct i386_all_regs *ix86,
int ( * io ) ( struct block_device *blockdev,
uint64_t block,
unsigned long count,
userptr_t buffer ) ) {
struct block_device *blockdev = drive->blockdev;
unsigned int cylinder, head, sector;
unsigned long lba;
unsigned int count;
userptr_t buffer;
/* Validate blocksize */
if ( blockdev->blksize != INT13_BLKSIZE ) {
DBG ( "Invalid blocksize (%zd) for non-extended read/write\n",
blockdev->blksize );
return -INT13_STATUS_INVALID;
}
/* Calculate parameters */
cylinder = ( ( ( ix86->regs.cl & 0xc0 ) << 2 ) | ix86->regs.ch );
assert ( cylinder < drive->cylinders );
head = ix86->regs.dh;
assert ( head < drive->heads );
sector = ( ix86->regs.cl & 0x3f );
assert ( ( sector >= 1 ) && ( sector <= drive->sectors_per_track ) );
lba = ( ( ( ( cylinder * drive->heads ) + head )
* drive->sectors_per_track ) + sector - 1 );
count = ix86->regs.al;
buffer = real_to_user ( ix86->segs.es, ix86->regs.bx );
DBG ( "C/H/S %d/%d/%d = LBA %#lx <-> %04x:%04x (count %d)\n", cylinder,
head, sector, lba, ix86->segs.es, ix86->regs.bx, count );
/* Read from / write to block device */
if ( io ( blockdev, lba, count, buffer ) != 0 )
return -INT13_STATUS_READ_ERROR;
return 0;
}
/**
* INT 13, 02 - Read sectors
*
* @v drive Emulated drive
* @v al Number of sectors to read (must be nonzero)
* @v ch Low bits of cylinder number
* @v cl (bits 7:6) High bits of cylinder number
* @v cl (bits 5:0) Sector number
* @v dh Head number
* @v es:bx Data buffer
* @ret status Status code
* @ret al Number of sectors read
*/
static int int13_read_sectors ( struct int13_drive *drive,
struct i386_all_regs *ix86 ) {
DBG ( "Read: " );
return int13_rw_sectors ( drive, ix86, drive->blockdev->read );
}
/**
* INT 13, 03 - Write sectors
*
* @v drive Emulated drive
* @v al Number of sectors to write (must be nonzero)
* @v ch Low bits of cylinder number
* @v cl (bits 7:6) High bits of cylinder number
* @v cl (bits 5:0) Sector number
* @v dh Head number
* @v es:bx Data buffer
* @ret status Status code
* @ret al Number of sectors written
*/
static int int13_write_sectors ( struct int13_drive *drive,
struct i386_all_regs *ix86 ) {
DBG ( "Write: " );
return int13_rw_sectors ( drive, ix86, drive->blockdev->write );
}
/**
* INT 13, 08 - Get drive parameters
*
* @v drive Emulated drive
* @ret status Status code
* @ret ch Low bits of maximum cylinder number
* @ret cl (bits 7:6) High bits of maximum cylinder number
* @ret cl (bits 5:0) Maximum sector number
* @ret dh Maximum head number
* @ret dl Number of drives
*/
static int int13_get_parameters ( struct int13_drive *drive,
struct i386_all_regs *ix86 ) {
unsigned int max_cylinder = drive->cylinders - 1;
unsigned int max_head = drive->heads - 1;
unsigned int max_sector = drive->sectors_per_track; /* sic */
DBG ( "Get drive parameters\n" );
ix86->regs.ch = ( max_cylinder & 0xff );
ix86->regs.cl = ( ( ( max_cylinder >> 8 ) << 6 ) | max_sector );
ix86->regs.dh = max_head;
get_real ( ix86->regs.dl, BDA_SEG, BDA_NUM_DRIVES );
return 0;
}
/**
* INT 13, 15 - Get disk type
*
* @v drive Emulated drive
* @ret ah Type code
* @ret cx:dx Sector count
* @ret status Status code / disk type
*/
static int int13_get_disk_type ( struct int13_drive *drive,
struct i386_all_regs *ix86 ) {
DBG ( "Get disk type\n" );
ix86->regs.cx = ( drive->cylinders >> 16 );
ix86->regs.dx = ( drive->cylinders & 0xffff );
return INT13_DISK_TYPE_HDD;
}
/**
* INT 13, 41 - Extensions installation check
*
* @v drive Emulated drive
* @v bx 0x55aa
* @ret bx 0xaa55
* @ret cx Extensions API support bitmap
* @ret status Status code / API version
*/
static int int13_extension_check ( struct int13_drive *drive __unused,
struct i386_all_regs *ix86 ) {
if ( ix86->regs.bx == 0x55aa ) {
DBG ( "INT 13 extensions installation check\n" );
ix86->regs.bx = 0xaa55;
ix86->regs.cx = INT13_EXTENSION_LINEAR;
return INT13_EXTENSION_VER_1_X;
} else {
return -INT13_STATUS_INVALID;
}
}
/**
* Extended read / write
*
* @v drive Emulated drive
* @v ds:si Disk address packet
* @v io Read / write method
* @ret status Status code
*/
static int int13_extended_rw ( struct int13_drive *drive,
struct i386_all_regs *ix86,
int ( * io ) ( struct block_device *blockdev,
uint64_t block,
unsigned long count,
userptr_t buffer ) ) {
struct block_device *blockdev = drive->blockdev;
struct int13_disk_address addr;
uint64_t lba;
unsigned long count;
userptr_t buffer;
/* Read parameters from disk address structure */
copy_from_real ( &addr, ix86->segs.ds, ix86->regs.si, sizeof ( addr ));
lba = addr.lba;
count = addr.count;
buffer = real_to_user ( addr.buffer.segment, addr.buffer.offset );
DBG ( "LBA %#llx <-> %04x:%04x (count %ld)\n", (unsigned long long)lba,
addr.buffer.segment, addr.buffer.offset, count );
/* Read from / write to block device */
if ( io ( blockdev, lba, count, buffer ) != 0 )
return -INT13_STATUS_READ_ERROR;
return 0;
}
/**
* INT 13, 42 - Extended read
*
* @v drive Emulated drive
* @v ds:si Disk address packet
* @ret status Status code
*/
static int int13_extended_read ( struct int13_drive *drive,
struct i386_all_regs *ix86 ) {
DBG ( "Extended read: " );
return int13_extended_rw ( drive, ix86, drive->blockdev->read );
}
/**
* INT 13, 43 - Extended write
*
* @v drive Emulated drive
* @v ds:si Disk address packet
* @ret status Status code
*/
static int int13_extended_write ( struct int13_drive *drive,
struct i386_all_regs *ix86 ) {
DBG ( "Extended write: " );
return int13_extended_rw ( drive, ix86, drive->blockdev->write );
}
/**
* INT 13, 48 - Get extended parameters
*
* @v drive Emulated drive
* @v ds:si Drive parameter table
* @ret status Status code
*/
static int int13_get_extended_parameters ( struct int13_drive *drive,
struct i386_all_regs *ix86 ) {
struct int13_disk_parameters params = {
.bufsize = sizeof ( params ),
.flags = INT13_FL_DMA_TRANSPARENT,
.cylinders = drive->cylinders,
.heads = drive->heads,
.sectors_per_track = drive->sectors_per_track,
.sectors = drive->blockdev->blocks,
.sector_size = drive->blockdev->blksize,
};
DBG ( "Get extended drive parameters to %04x:%04x\n",
ix86->segs.ds, ix86->regs.si );
copy_to_real ( ix86->segs.ds, ix86->regs.si, &params,
sizeof ( params ) );
return 0;
}
struct int13_cdrom_specification {
/** Size of packet in bytes */
uint8_t size;
/** Boot media type */
uint8_t media_type;
/** Drive number */
uint8_t drive;
};
/**
* INT 13, 4b - Get CD-ROM status / terminate emulation
*
* @v drive Emulated drive
* @v ds:si El Torito specification packet to fill in
* @ret status Status code
*/
static int int13_cdrom_status_terminate ( struct int13_drive *drive,
struct i386_all_regs *ix86 ) {
struct int13_cdrom_specification specification;
DBG ( "Get CD-ROM emulation parameters to %04x:%04x\n",
ix86->segs.ds, ix86->regs.di );
memset ( &specification, 0, sizeof ( specification ) );
specification.size = sizeof ( specification );
specification.drive = drive->drive;
copy_to_real ( ix86->segs.ds, ix86->regs.si, &specification,
sizeof ( specification ) );
return 0;
}
/**
* INT 13 handler
*
*/
static void int13 ( struct i386_all_regs *ix86 ) {
int command = ix86->regs.ah;
struct int13_drive *drive;
int status;
list_for_each_entry ( drive, &drives, list ) {
if ( drive->drive != ix86->regs.dl )
continue;
DBG ( "INT 13,%04x (%02x): ", ix86->regs.ax, drive->drive );
switch ( command ) {
case INT13_RESET:
status = int13_reset ( drive, ix86 );
break;
case INT13_GET_LAST_STATUS:
status = int13_get_last_status ( drive, ix86 );
break;
case INT13_READ_SECTORS:
status = int13_read_sectors ( drive, ix86 );
break;
case INT13_WRITE_SECTORS:
status = int13_write_sectors ( drive, ix86 );
break;
case INT13_GET_PARAMETERS:
status = int13_get_parameters ( drive, ix86 );
break;
case INT13_GET_DISK_TYPE:
status = int13_get_disk_type ( drive, ix86 );
break;
case INT13_EXTENSION_CHECK:
status = int13_extension_check ( drive, ix86 );
break;
case INT13_EXTENDED_READ:
status = int13_extended_read ( drive, ix86 );
break;
case INT13_EXTENDED_WRITE:
status = int13_extended_write ( drive, ix86 );
break;
case INT13_GET_EXTENDED_PARAMETERS:
status = int13_get_extended_parameters ( drive, ix86 );
break;
case INT13_CDROM_STATUS_TERMINATE:
status = int13_cdrom_status_terminate ( drive, ix86 );
break;
default:
DBG ( "*** Unrecognised INT 13 ***\n" );
status = -INT13_STATUS_INVALID;
break;
}
/* Store status for INT 13,01 */
drive->last_status = status;
/* Negative status indicates an error */
if ( status < 0 ) {
ix86->flags |= CF;
status = -status;
DBG ( "INT13 failed with status %x\n", status );
}
ix86->regs.ah = status;
/* Set OF to indicate to wrapper not to chain this call */
ix86->flags |= OF;
break;
}
}
/**
* Hook INT 13 handler
*
*/
static void hook_int13 ( void ) {
/* Assembly wrapper to call int13(). int13() sets OF if we
* should not chain to the previous handler. (The wrapper
* clears CF and OF before calling int13()).
*/
__asm__ __volatile__ (
TEXT16_CODE ( "\nint13_wrapper:\n\t"
"orb $0, %%al\n\t" /* clear CF and OF */
"pushl %0\n\t" /* call int13() */
"pushw %%cs\n\t"
"call prot_call\n\t"
"jo 1f\n\t" /* chain if OF not set */
"pushfw\n\t"
"lcall *%%cs:int13_vector\n\t"
"\n1:\n\t"
"call 2f\n\t" /* return with flags intact */
"lret $2\n\t"
"\n2:\n\t"
"ret $4\n\t" ) : : "i" ( int13 ) );
hook_bios_interrupt ( 0x13, ( unsigned int ) int13_wrapper,
&int13_vector );
}
/**
* Unhook INT 13 handler
*/
static void unhook_int13 ( void ) {
unhook_bios_interrupt ( 0x13, ( unsigned int ) int13_wrapper,
&int13_vector );
}
/**
* Guess INT 13 drive geometry
*
* @v drive Emulated drive
*
* Guesses the drive geometry by inspecting the partition table.
*/
static void guess_int13_geometry ( struct int13_drive *drive ) {
struct master_boot_record mbr;
struct partition_table_entry *partition;
unsigned int guessed_heads = 255;
unsigned int guessed_sectors_per_track = 63;
unsigned long blocks;
unsigned long blocks_per_cyl;
unsigned int i;
/* Don't even try when the blksize is invalid for C/H/S access */
if ( drive->blockdev->blksize != INT13_BLKSIZE )
return;
/* Scan through partition table and modify guesses for heads
* and sectors_per_track if we find any used partitions.
*/
if ( drive->blockdev->read ( drive->blockdev, 0, 1,
virt_to_user ( &mbr ) ) == 0 ) {
for ( i = 0 ; i < 4 ; i++ ) {
partition = &mbr.partitions[i];
if ( ! partition->type )
continue;
guessed_heads =
( PART_HEAD ( partition->chs_end ) + 1 );
guessed_sectors_per_track =
PART_SECTOR ( partition->chs_end );
DBG ( "Guessing C/H/S xx/%d/%d based on partition "
"%d\n", guessed_heads,
guessed_sectors_per_track, ( i + 1 ) );
}
} else {
DBG ( "Could not read partition table to guess geometry\n" );
}
/* Apply guesses if no geometry already specified */
if ( ! drive->heads )
drive->heads = guessed_heads;
if ( ! drive->sectors_per_track )
drive->sectors_per_track = guessed_sectors_per_track;
if ( ! drive->cylinders ) {
/* Avoid attempting a 64-bit divide on a 32-bit system */
blocks = ( ( drive->blockdev->blocks <= ULONG_MAX ) ?
drive->blockdev->blocks : ULONG_MAX );
blocks_per_cyl = ( drive->heads * drive->sectors_per_track );
assert ( blocks_per_cyl != 0 );
drive->cylinders = ( blocks / blocks_per_cyl );
if ( drive->cylinders > 1024 )
drive->cylinders = 1024;
}
}
/**
* Register INT 13 emulated drive
*
* @v drive Emulated drive
*
* Registers the drive with the INT 13 emulation subsystem, and hooks
* the INT 13 interrupt vector (if not already hooked).
*
* The underlying block device must be valid. A drive number and
* geometry will be assigned if left blank.
*/
void register_int13_drive ( struct int13_drive *drive ) {
uint8_t num_drives;
/* Give drive a default geometry if none specified */
guess_int13_geometry ( drive );
/* Assign drive number if none specified, update BIOS drive count */
get_real ( num_drives, BDA_SEG, BDA_NUM_DRIVES );
if ( ! drive->drive )
drive->drive = ( num_drives | 0x80 );
if ( num_drives <= ( drive->drive & 0x7f ) )
num_drives = ( ( drive->drive & 0x7f ) + 1 );
put_real ( num_drives, BDA_SEG, BDA_NUM_DRIVES );
DBG ( "Registered INT13 drive %02x with C/H/S geometry %d/%d/%d\n",
drive->drive, drive->cylinders, drive->heads,
drive->sectors_per_track );
/* Hook INT 13 vector if not already hooked */
if ( list_empty ( &drives ) )
hook_int13();
/* Add to list of emulated drives */
list_add ( &drive->list, &drives );
}
/**
* Unregister INT 13 emulated drive
*
* @v drive Emulated drive
*
* Unregisters the drive from the INT 13 emulation subsystem. If this
* is the last emulated drive, the INT 13 vector is unhooked (if
* possible).
*/
void unregister_int13_drive ( struct int13_drive *drive ) {
/* Remove from list of emulated drives */
list_del ( &drive->list );
DBG ( "Unregistered INT13 drive %02x\n", drive->drive );
/* Unhook INT 13 vector if no more drives */
if ( list_empty ( &drives ) )
unhook_int13();
}
/**
* Attempt to boot from an INT 13 drive
*
* @v drive Drive number
* @ret rc Return status code
*
* This boots from the specified INT 13 drive by loading the Master
* Boot Record to 0000:7c00 and jumping to it. INT 18 is hooked to
* capture an attempt by the MBR to boot the next device. (This is
* the closest thing to a return path from an MBR).
*
* Note that this function can never return success, by definition.
*/
int int13_boot ( unsigned int drive ) {
int status, signature;
int discard_c, discard_d;
int rc;
DBG ( "Booting from INT 13 drive %02x\n", drive );
/* Use INT 13 to read the boot sector */
__asm__ __volatile__ ( REAL_CODE ( "pushw %%es\n\t"
"pushw $0\n\t"
"popw %%es\n\t"
"stc\n\t"
"int $0x13\n\t"
"sti\n\t" /* BIOS bugs */
"jc 1f\n\t"
"xorl %%eax, %%eax\n\t"
"\n1:\n\t"
"movzwl %%es:0x7dfe, %%ebx\n\t"
"popw %%es\n\t" )
: "=a" ( status ), "=b" ( signature ),
"=c" ( discard_c ), "=d" ( discard_d )
: "a" ( 0x0201 ), "b" ( 0x7c00 ),
"c" ( 1 ), "d" ( drive ) );
if ( status )
return -EIO;
/* Check signature is correct */
if ( signature != be16_to_cpu ( 0x55aa ) ) {
DBG ( "Invalid disk signature %#04x (should be 0x55aa)\n",
cpu_to_be16 ( signature ) );
return -ENOEXEC;
}
/* Jump to boot sector */
if ( ( rc = call_bootsector ( 0x0, 0x7c00, drive ) ) != 0 ) {
DBG ( "INT 13 drive %02x boot returned\n", drive );
return rc;
}
return -ECANCELED; /* -EIMPOSSIBLE */
}
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