Add INT 13 emulation layer (which provides an interface to gPXE block

devices).

1 files changed, 475 insertions, 0 deletions

diff --git a/src/arch/i386/interface/pcbios/int13.c b/src/arch/i386/interface/pcbios/int13.c
new file mode 100644
index 00000000..edf62f4d
--- /dev/null
+++ b/src/arch/i386/interface/pcbios/int13.c
@@ -0,0 +1,475 @@
+/*
+ * 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 <limits.h>
+#include <assert.h>
+#include <gpxe/list.h>
+#include <gpxe/blockdev.h>
+#include <realmode.h>
+#include <bios.h>
+#include <biosint.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 );
+
+/**
+ * Convert CHS address to linear address
+ *
+ * @v drive		Emulated drive
+ * @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
+ * @ret lba		LBA address
+ * 
+ */
+static unsigned long chs_to_lba ( struct int13_drive *drive,
+				  struct i386_all_regs *ix86 ) {
+	unsigned int cylinder;
+	unsigned int head;
+	unsigned int sector;
+	unsigned long lba;
+
+	cylinder = ( ( ( ix86->regs.cl & 0xc0 ) << 8 ) | ix86->regs.ch );
+	head = ix86->regs.dh;
+	sector = ( ix86->regs.cl & 0x3f );
+
+	assert ( cylinder < drive->cylinders );
+	assert ( head < drive->heads );
+	assert ( ( sector >= 1 ) && ( sector <= drive->sectors_per_track ) );
+
+	lba = ( ( ( ( cylinder * drive->heads ) + head )
+		  * drive->sectors_per_track ) + sector - 1 );
+
+	DBG ( "C/H/S address %x/%x/%x -> LBA %x\n",
+	      cylinder, head, sector, lba );
+
+	return lba;
+}
+
+/**
+ * Read from drive to real-mode data buffer
+ *
+ * @v drive		Emulated drive
+ * @v lba		LBA starting sector number
+ * @v data		Data buffer
+ * @v count		Number of sectors to read
+ * @ret status		Status code
+ */
+static int int13_read ( struct int13_drive *drive, uint64_t lba,
+			struct segoff data, unsigned long count ) {
+	struct block_device *blockdev = drive->blockdev;
+	size_t blksize = blockdev->blksize;
+	uint8_t buffer[blksize];
+	int rc;
+
+	DBG ( "Read %lx sectors from %llx to %04x:%04x\n", count,
+	      ( unsigned long long ) lba, data.segment, data.offset );
+	while ( count-- ) {
+		if ( ( rc = blockdev->read ( blockdev, lba, buffer ) ) != 0 )
+			return INT13_STATUS_READ_ERROR;
+		copy_to_real ( data.segment, data.offset, buffer, blksize );
+		data.offset += blksize;
+		lba++;
+	}
+	return 0;
+}
+
+/**
+ * Write from real-mode data buffer to drive
+ *
+ * @v drive		Emulated drive
+ * @v lba		LBA starting sector number
+ * @v data		Data buffer
+ * @v count		Number of sectors to read
+ * @ret status		Status code
+ */
+static int int13_write ( struct int13_drive *drive, uint64_t lba,
+			 struct segoff data, unsigned long count ) {
+	struct block_device *blockdev = drive->blockdev;
+	size_t blksize = blockdev->blksize;
+	uint8_t buffer[blksize];
+	int rc;
+
+	DBG ( "Write %lx sectors from %04x:%04x to %llx\n", count,
+	      data.segment, data.offset, ( unsigned long long ) lba );
+	while ( count-- ) {
+		copy_from_real ( buffer, data.segment, data.offset, blksize );
+		if ( ( rc = blockdev->write ( blockdev, lba, buffer ) ) != 0 )
+			return INT13_STATUS_WRITE_ERROR;
+		data.offset += blksize;
+		lba++;
+	}
+	return 0;
+}
+
+/**
+ * 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;
+}
+
+/**
+ * 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 ) {
+	unsigned long lba = chs_to_lba ( drive, ix86 );
+	unsigned int count = ix86->regs.al;
+	struct segoff data = {
+		.segment = ix86->segs.es,
+		.offset = ix86->regs.bx,
+	};
+
+	if ( drive->blockdev->blksize != INT13_BLKSIZE ) {
+		DBG ( "Invalid blocksize (%d) for non-extended read\n",
+		      drive->blockdev->blksize );
+		return INT13_STATUS_INVALID;
+	}
+
+	return int13_read ( drive, lba, data, count );
+}
+
+/**
+ * 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 ) {
+	unsigned long lba = chs_to_lba ( drive, ix86 );
+	unsigned int count = ix86->regs.al;
+	struct segoff data = {
+		.segment = ix86->segs.es,
+		.offset = ix86->regs.bx,
+	};
+
+	if ( drive->blockdev->blksize != INT13_BLKSIZE ) {
+		DBG ( "Invalid blocksize (%d) for non-extended write\n",
+		      drive->blockdev->blksize );
+		return INT13_STATUS_INVALID;
+	}
+
+	return int13_write ( drive, lba, data, count );
+}
+
+/**
+ * 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, 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 ) {
+	struct int13_disk_address addr;
+
+	copy_from_real ( &addr, ix86->segs.ds, ix86->regs.si,
+			 sizeof ( addr ) );
+	return int13_read ( drive, addr.lba, addr.buffer, addr.count );
+}
+
+/**
+ * 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 ) {
+	struct int13_disk_address addr;
+
+	copy_from_real ( &addr, ix86->segs.ds, ix86->regs.si,
+			 sizeof ( addr ) );
+	return int13_write ( drive, addr.lba, addr.buffer, addr.count );
+}
+
+/**
+ * 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;
+}
+
+/**
+ * INT 13 handler
+ *
+ */
+static void int13 ( struct i386_all_regs *ix86 ) {
+	struct int13_drive *drive;
+	int status;
+
+	list_for_each_entry ( drive, &drives, list ) {
+		if ( drive->drive != ix86->regs.dl )
+			continue;
+		
+		DBG ( "INT 13, %02x on drive %02x\n", ix86->regs.ah,
+		      ix86->regs.dl );
+	
+		switch ( ix86->regs.ah ) {
+		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_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;
+		default:
+			DBG ( "Unrecognised INT 13\n" );
+			status = INT13_STATUS_INVALID;
+			break;
+		}
+
+		/* Store status for INT 13,01 */
+		drive->last_status = status;
+		/* All functions return status via %ah and CF */
+		ix86->regs.ah = status;
+		if ( status ) {
+			ix86->flags |= CF;
+			DBG ( "INT13 failed with status %x\n", status );
+		}
+		/* Set OF to indicate to wrapper not to chain this call */
+		ix86->flags |= OF;
+	}
+}
+
+/**
+ * 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__ ( ".section \".text16\", \"ax\", @progbits\n\t"
+				".code16\n\t"
+				"\nint13_wrapper:\n\t"
+				"orb $0, %%al\n\t" /* clear CF and OF */
+				"pushl %0\n\t" /* call int13() */
+				"data32 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"
+				".previous\n\t"
+				".code32\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 );
+}
+
+/**
+ * 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;
+	unsigned long blocks;
+	unsigned long blocks_per_cyl;
+
+	/* Give drive a default geometry if none specified */
+	if ( ! drive->heads )
+		drive->heads = 255;
+	if ( ! drive->sectors_per_track )
+		drive->sectors_per_track = 63;
+	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 );
+	}
+
+	/* 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();
+}