[efi] Add basic EFI SAN booting capability

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 1062 insertions, 0 deletions

diff --git a/src/interface/efi/efi_block.c b/src/interface/efi/efi_block.c
new file mode 100644
index 00000000..ab230943
--- /dev/null
+++ b/src/interface/efi/efi_block.c
@@ -0,0 +1,1062 @@
+/*
+ * Copyright (C) 2016 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., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+/**
+ * @file
+ *
+ * EFI block device protocols
+ *
+ */
+
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <ipxe/refcnt.h>
+#include <ipxe/list.h>
+#include <ipxe/uri.h>
+#include <ipxe/interface.h>
+#include <ipxe/blockdev.h>
+#include <ipxe/xfer.h>
+#include <ipxe/open.h>
+#include <ipxe/retry.h>
+#include <ipxe/timer.h>
+#include <ipxe/process.h>
+#include <ipxe/sanboot.h>
+#include <ipxe/iso9660.h>
+#include <ipxe/efi/efi.h>
+#include <ipxe/efi/Protocol/BlockIo.h>
+#include <ipxe/efi/Protocol/SimpleFileSystem.h>
+#include <ipxe/efi/efi_driver.h>
+#include <ipxe/efi/efi_strings.h>
+#include <ipxe/efi/efi_snp.h>
+#include <ipxe/efi/efi_utils.h>
+#include <ipxe/efi/efi_block.h>
+
+/** Timeout for EFI block device commands (in ticks) */
+#define EFI_BLOCK_TIMEOUT ( 15 * TICKS_PER_SEC )
+
+/** Boot filename */
+static wchar_t efi_block_boot_filename[] = EFI_REMOVABLE_MEDIA_FILE_NAME;
+
+/** iPXE EFI block device vendor device path GUID */
+#define IPXE_BLOCK_DEVICE_PATH_GUID					\
+	{ 0x8998b594, 0xf531, 0x4e87,					\
+	  { 0x8b, 0xdf, 0x8f, 0x88, 0x54, 0x3e, 0x99, 0xd4 } }
+
+/** iPXE EFI block device vendor device path GUID */
+static EFI_GUID ipxe_block_device_path_guid
+	= IPXE_BLOCK_DEVICE_PATH_GUID;
+
+/** An iPXE EFI block device vendor device path */
+struct efi_block_vendor_path {
+	/** Generic vendor device path */
+	VENDOR_DEVICE_PATH vendor;
+	/** Block device URI */
+	CHAR16 uri[0];
+} __attribute__ (( packed ));
+
+/** An EFI block device */
+struct efi_block {
+	/** Reference count */
+	struct refcnt refcnt;
+	/** List of all registered block devices */
+	struct list_head list;
+
+	/** Block device URI */
+	struct uri *uri;
+	/** Drive number */
+	unsigned int drive;
+	/** Underlying block device interface */
+	struct interface intf;
+
+	/** Current device status */
+	int block_rc;
+	/** Raw block device capacity */
+	struct block_device_capacity capacity;
+	/** Block size shift
+	 *
+	 * To allow for emulation of CD-ROM access, this represents
+	 * the left-shift required to translate from EFI I/O blocks to
+	 * underlying blocks.
+	 *
+	 * Note that the LogicalBlocksPerPhysicalBlock field in
+	 * EFI_BLOCK_IO_MEDIA is unable to encapsulate this
+	 * information, since it does not allow us to describe a
+	 * situation in which there are multiple "physical"
+	 * (i.e. underlying) blocks per logical (i.e. exposed) block.
+	 */
+	unsigned int blksize_shift;
+
+	/** EFI handle */
+	EFI_HANDLE handle;
+	/** Media descriptor */
+	EFI_BLOCK_IO_MEDIA media;
+	/** Block I/O protocol */
+	EFI_BLOCK_IO_PROTOCOL block_io;
+	/** Device path protocol */
+	EFI_DEVICE_PATH_PROTOCOL *path;
+
+	/** Command interface */
+	struct interface command;
+	/** Command timeout timer */
+	struct retry_timer timer;
+	/** Command status */
+	int command_rc;
+};
+
+/**
+ * Free EFI block device
+ *
+ * @v refcnt		Reference count
+ */
+static void efi_block_free ( struct refcnt *refcnt ) {
+	struct efi_block *block =
+		container_of ( refcnt, struct efi_block, refcnt );
+
+	assert ( ! timer_running ( &block->timer ) );
+	uri_put ( block->uri );
+	free ( block->path );
+	free ( block );
+}
+
+/** List of EFI block devices */
+static LIST_HEAD ( efi_block_devices );
+
+/**
+ * Find EFI block device
+ *
+ * @v drive		Drive number
+ * @ret block		Block device, or NULL if not found
+ */
+static struct efi_block * efi_block_find ( unsigned int drive ) {
+	struct efi_block *block;
+
+	list_for_each_entry ( block, &efi_block_devices, list ) {
+		if ( block->drive == drive )
+			return block;
+	}
+
+	return NULL;
+}
+
+/**
+ * Close EFI block device command
+ *
+ * @v block		Block device
+ * @v rc		Reason for close
+ */
+static void efi_block_cmd_close ( struct efi_block *block, int rc ) {
+
+	/* Stop timer */
+	stop_timer ( &block->timer );
+
+	/* Restart interface */
+	intf_restart ( &block->command, rc );
+
+	/* Record command status */
+	block->command_rc = rc;
+}
+
+/**
+ * Record EFI block device capacity
+ *
+ * @v block		Block device
+ * @v capacity		Block device capacity
+ */
+static void efi_block_cmd_capacity ( struct efi_block *block,
+				     struct block_device_capacity *capacity ) {
+
+	/* Record raw capacity information */
+	memcpy ( &block->capacity, capacity, sizeof ( block->capacity ) );
+}
+
+/** EFI block device command interface operations */
+static struct interface_operation efi_block_cmd_op[] = {
+	INTF_OP ( intf_close, struct efi_block *, efi_block_cmd_close ),
+	INTF_OP ( block_capacity, struct efi_block *, efi_block_cmd_capacity ),
+};
+
+/** EFI block device command interface descriptor */
+static struct interface_descriptor efi_block_cmd_desc =
+	INTF_DESC ( struct efi_block, command, efi_block_cmd_op );
+
+/**
+ * Handle EFI block device command timeout
+ *
+ * @v retry		Retry timer
+ */
+static void efi_block_cmd_expired ( struct retry_timer *timer,
+				    int over __unused ) {
+	struct efi_block *block =
+		container_of ( timer, struct efi_block, timer );
+
+	efi_block_cmd_close ( block, -ETIMEDOUT );
+}
+
+/**
+ * Restart EFI block device interface
+ *
+ * @v block		Block device
+ * @v rc		Reason for restart
+ */
+static void efi_block_restart ( struct efi_block *block, int rc ) {
+
+	/* Restart block device interface */
+	intf_nullify ( &block->command ); /* avoid potential loops */
+	intf_restart ( &block->intf, rc );
+
+	/* Close any outstanding command */
+	efi_block_cmd_close ( block, rc );
+
+	/* Record device error */
+	block->block_rc = rc;
+}
+
+/**
+ * (Re)open EFI block device
+ *
+ * @v block		Block device
+ * @ret rc		Return status code
+ *
+ * This function will block until the device is available.
+ */
+static int efi_block_reopen ( struct efi_block *block ) {
+	int rc;
+
+	/* Close any outstanding command and restart interface */
+	efi_block_restart ( block, -ECONNRESET );
+
+	/* Mark device as being not yet open */
+	block->block_rc = -EINPROGRESS;
+
+	/* Open block device interface */
+	if ( ( rc = xfer_open_uri ( &block->intf, block->uri ) ) != 0 ) {
+		DBGC ( block, "EFIBLK %#02x could not (re)open URI: %s\n",
+		       block->drive, strerror ( rc ) );
+		return rc;
+	}
+
+	/* Wait for device to become available */
+	while ( block->block_rc == -EINPROGRESS ) {
+		step();
+		if ( xfer_window ( &block->intf ) != 0 ) {
+			block->block_rc = 0;
+			return 0;
+		}
+	}
+
+	DBGC ( block, "EFIBLK %#02x never became available: %s\n",
+	       block->drive, strerror ( block->block_rc ) );
+	return block->block_rc;
+}
+
+/**
+ * Handle closure of underlying block device interface
+ *
+ * @v block		Block device
+ * @ret rc		Reason for close
+ */
+static void efi_block_close ( struct efi_block *block, int rc ) {
+
+	/* Any closure is an error from our point of view */
+	if ( rc == 0 )
+		rc = -ENOTCONN;
+	DBGC ( block, "EFIBLK %#02x went away: %s\n",
+	       block->drive, strerror ( rc ) );
+
+	/* Close any outstanding command and restart interface */
+	efi_block_restart ( block, rc );
+}
+
+/**
+ * Check EFI block device flow control window
+ *
+ * @v block		Block device
+ */
+static size_t efi_block_window ( struct efi_block *block __unused ) {
+
+	/* We are never ready to receive data via this interface.
+	 * This prevents objects that support both block and stream
+	 * interfaces from attempting to send us stream data.
+	 */
+	return 0;
+}
+
+/** EFI block device interface operations */
+static struct interface_operation efi_block_op[] = {
+	INTF_OP ( intf_close, struct efi_block *, efi_block_close ),
+	INTF_OP ( xfer_window, struct efi_block *, efi_block_window ),
+};
+
+/** EFI block device interface descriptor */
+static struct interface_descriptor efi_block_desc =
+	INTF_DESC ( struct efi_block, intf, efi_block_op );
+
+/** EFI block device command context */
+struct efi_block_command_context {
+	/** Starting LBA (using EFI block numbering) */
+	uint64_t lba;
+	/** Data buffer */
+	void *data;
+	/** Length of data buffer */
+	size_t len;
+	/** Block device read/write operation (if any) */
+	int ( * block_rw ) ( struct interface *control, struct interface *data,
+			     uint64_t lba, unsigned int count,
+			     userptr_t buffer, size_t len );
+};
+
+/**
+ * Initiate EFI block device command
+ *
+ * @v block		Block device
+ * @v op		Command operation
+ * @v context		Command context, or NULL if not required
+ * @ret rc		Return status code
+ */
+static int efi_block_command ( struct efi_block *block,
+			       int ( * op ) ( struct efi_block *block,
+					      struct efi_block_command_context
+						      *context ),
+			       struct efi_block_command_context *context ) {
+	int rc;
+
+	/* Sanity check */
+	assert ( ! timer_running ( &block->timer ) );
+
+	/* Reopen block device if applicable */
+	if ( ( block->block_rc != 0 ) &&
+	     ( ( rc = efi_block_reopen ( block ) ) != 0 ) ) {
+	     goto err_reopen;
+	}
+
+	/* Start expiry timer */
+	start_timer_fixed ( &block->timer, EFI_BLOCK_TIMEOUT );
+
+	/* Initiate block device operation */
+	if ( ( rc = op ( block, context ) ) != 0 )
+		goto err_op;
+
+	/* Wait for command to complete */
+	while ( timer_running ( &block->timer ) )
+		step();
+
+	/* Collect return status */
+	rc = block->command_rc;
+
+	return rc;
+
+ err_op:
+	stop_timer ( &block->timer );
+ err_reopen:
+	return rc;
+}
+
+/**
+ * Initiate EFI block device read/write command
+ *
+ * @v block		Block device
+ * @v context		Command context
+ * @ret rc		Return status code
+ */
+static int efi_block_cmd_rw ( struct efi_block *block,
+			      struct efi_block_command_context *context ) {
+	uint64_t lba;
+	unsigned int count;
+	int rc;
+
+	/* Calculate underlying starting LBA and block count */
+	if ( block->capacity.blksize == 0 ) {
+		DBGC ( block, "EFIBLK %#02x has zero block size\n",
+		       block->drive );
+		return -EINVAL;
+	}
+	lba = ( context->lba << block->blksize_shift );
+	count = ( context->len / block->capacity.blksize );
+	if ( ( count * block->capacity.blksize ) != context->len ) {
+		DBGC ( block, "EFIBLK %#02x invalid read/write length %#zx\n",
+		       block->drive, context->len );
+		return -EINVAL;
+	}
+
+	/* Initiate read/write command */
+	if ( ( rc = context->block_rw ( &block->intf, &block->command, lba,
+					count, virt_to_user ( context->data ),
+					context->len ) ) != 0 ) {
+		DBGC ( block, "EFIBLK %#02x could not initiate read/write: "
+		       "%s\n", block->drive, strerror ( rc ) );
+		return rc;
+	}
+
+	return 0;
+}
+
+/**
+ * Initiate EFI block device read capacity command
+ *
+ * @v block		Block device
+ * @v context		Command context
+ * @ret rc		Return status code
+ */
+static int efi_block_cmd_read_capacity ( struct efi_block *block,
+					 struct efi_block_command_context
+						 *context __unused ) {
+	int rc;
+
+	/* Initiate read capacity command */
+	if ( ( rc = block_read_capacity ( &block->intf,
+					  &block->command ) ) != 0 ) {
+		DBGC ( block, "EFIBLK %#02x could not read capacity: %s\n",
+		       block->drive, strerror ( rc ) );
+		return rc;
+	}
+
+	return 0;
+}
+
+/**
+ * Reset EFI block device
+ *
+ * @v block_io		Block I/O protocol
+ * @v verify		Perform extended verification
+ * @ret efirc		EFI status code
+ */
+static EFI_STATUS EFIAPI efi_block_io_reset ( EFI_BLOCK_IO_PROTOCOL *block_io,
+					      BOOLEAN verify __unused ) {
+	struct efi_block *block =
+		container_of ( block_io, struct efi_block, block_io );
+	int rc;
+
+	DBGC2 ( block, "EFIBLK %#02x reset\n", block->drive );
+
+	/* Claim network devices for use by iPXE */
+	efi_snp_claim();
+
+	/* Reopen block device */
+	if ( ( rc = efi_block_reopen ( block ) ) != 0 )
+		goto err_reopen;
+
+ err_reopen:
+	efi_snp_release();
+	return EFIRC ( rc );
+}
+
+/**
+ * Read from EFI block device
+ *
+ * @v block_io		Block I/O protocol
+ * @v media		Media identifier
+ * @v lba		Starting LBA
+ * @v len		Size of buffer
+ * @v data		Data buffer
+ * @ret efirc		EFI status code
+ */
+static EFI_STATUS EFIAPI
+efi_block_io_read ( EFI_BLOCK_IO_PROTOCOL *block_io, UINT32 media __unused,
+		    EFI_LBA lba, UINTN len, VOID *data ) {
+	struct efi_block *block =
+		container_of ( block_io, struct efi_block, block_io );
+	struct efi_block_command_context context = {
+		.lba = lba,
+		.data = data,
+		.len = len,
+		.block_rw = block_read,
+	};
+	int rc;
+
+	DBGC2 ( block, "EFIBLK %#02x read LBA %#08llx to %p+%#08zx\n",
+		block->drive, context.lba, context.data, context.len );
+
+	/* Claim network devices for use by iPXE */
+	efi_snp_claim();
+
+	/* Issue read command */
+	if ( ( rc = efi_block_command ( block, efi_block_cmd_rw,
+					&context ) ) != 0 )
+		goto err_command;
+
+ err_command:
+	efi_snp_release();
+	return EFIRC ( rc );
+}
+
+/**
+ * Write to EFI block device
+ *
+ * @v block_io		Block I/O protocol
+ * @v media		Media identifier
+ * @v lba		Starting LBA
+ * @v len		Size of buffer
+ * @v data		Data buffer
+ * @ret efirc		EFI status code
+ */
+static EFI_STATUS EFIAPI
+efi_block_io_write ( EFI_BLOCK_IO_PROTOCOL *block_io, UINT32 media __unused,
+		     EFI_LBA lba, UINTN len, VOID *data ) {
+	struct efi_block *block =
+		container_of ( block_io, struct efi_block, block_io );
+	struct efi_block_command_context context = {
+		.lba = lba,
+		.data = data,
+		.len = len,
+		.block_rw = block_write,
+	};
+	int rc;
+
+	DBGC2 ( block, "EFIBLK %#02x write LBA %#08llx from %p+%#08zx\n",
+		block->drive, context.lba, context.data, context.len );
+
+	/* Claim network devices for use by iPXE */
+	efi_snp_claim();
+
+	/* Issue write command */
+	if ( ( rc = efi_block_command ( block, efi_block_cmd_rw,
+					&context ) ) != 0 )
+		goto err_command;
+
+ err_command:
+	efi_snp_release();
+	return EFIRC ( rc );
+}
+
+/**
+ * Flush data to EFI block device
+ *
+ * @v block_io		Block I/O protocol
+ * @ret efirc		EFI status code
+ */
+static EFI_STATUS EFIAPI
+efi_block_io_flush ( EFI_BLOCK_IO_PROTOCOL *block_io ) {
+	struct efi_block *block =
+		container_of ( block_io, struct efi_block, block_io );
+
+	DBGC2 ( block, "EFIBLK %#02x flush\n", block->drive );
+
+	/* Nothing to do */
+	return 0;
+}
+
+/**
+ * Create device path for EFI block device
+ *
+ * @v uri		Block device URI
+ * @v parent		Parent device path
+ * @ret path		Device path, or NULL on failure
+ *
+ * The caller must eventually free() the device path.
+ */
+static EFI_DEVICE_PATH_PROTOCOL *
+efi_block_path ( struct uri *uri, EFI_DEVICE_PATH_PROTOCOL *parent ) {
+	EFI_DEVICE_PATH_PROTOCOL *path;
+	struct efi_block_vendor_path *vendor;
+	EFI_DEVICE_PATH_PROTOCOL *end;
+	size_t prefix_len;
+	size_t uri_len;
+	size_t vendor_len;
+	size_t len;
+	char *uri_buf;
+
+	/* Calculate device path lengths */
+	end = efi_devpath_end ( parent );
+	prefix_len = ( ( void * ) end - ( void * ) parent );
+	uri_len = format_uri ( uri, NULL, 0 );
+	vendor_len = ( sizeof ( *vendor ) +
+		       ( ( uri_len + 1 /* NUL */ ) * sizeof ( wchar_t ) ) );
+	len = ( prefix_len + vendor_len + sizeof ( *end ) );
+
+	/* Allocate device path and space for URI buffer */
+	path = zalloc ( len + uri_len + 1 /* NUL */ );
+	if ( ! path )
+		return NULL;
+	uri_buf = ( ( ( void * ) path ) + len );
+
+	/* Construct device path */
+	memcpy ( path, parent, prefix_len );
+	vendor = ( ( ( void * ) path ) + prefix_len );
+	vendor->vendor.Header.Type = HARDWARE_DEVICE_PATH;
+	vendor->vendor.Header.SubType = HW_VENDOR_DP;
+	vendor->vendor.Header.Length[0] = ( vendor_len & 0xff );
+	vendor->vendor.Header.Length[1] = ( vendor_len >> 8 );
+	memcpy ( &vendor->vendor.Guid, &ipxe_block_device_path_guid,
+		 sizeof ( vendor->vendor.Guid ) );
+	format_uri ( uri, uri_buf, ( uri_len + 1 /* NUL */ ) );
+	efi_snprintf ( vendor->uri, ( uri_len + 1 /* NUL */ ), "%s", uri_buf );
+	end = ( ( ( void * ) vendor ) + vendor_len );
+	end->Type = END_DEVICE_PATH_TYPE;
+	end->SubType = END_ENTIRE_DEVICE_PATH_SUBTYPE;
+	end->Length[0] = sizeof ( *end );
+
+	return path;
+}
+
+/**
+ * Configure EFI block device as a CD-ROM, if applicable
+ *
+ * @v block		Block device
+ * @v scratch		Scratch data area
+ * @ret rc		Return status code
+ *
+ * The EDK2 code will ignore CD-ROM devices with a block size other
+ * than 2048.  While we could require the user to configure the block
+ * size appropriately, this is non-trivial and would impose a
+ * substantial learning effort on the user.  Instead, we perform
+ * essentially the same auto-detection as under a BIOS SAN boot; if
+ * the ISO9660 primary volume descriptor is present then we force a
+ * block size of 2048 and map read/write requests appropriately.
+ */
+static int efi_block_parse_iso9660 ( struct efi_block *block, void *scratch ) {
+	static const struct iso9660_primary_descriptor_fixed primary_check = {
+		.type = ISO9660_TYPE_PRIMARY,
+		.id = ISO9660_ID,
+	};
+	struct iso9660_primary_descriptor *primary = scratch;
+	struct efi_block_command_context context;
+	unsigned int blksize;
+	unsigned int blksize_shift;
+	int rc;
+
+	/* Calculate required blocksize shift for potential CD-ROM access */
+	blksize = block->capacity.blksize;
+	blksize_shift = 0;
+	while ( blksize < ISO9660_BLKSIZE ) {
+		blksize <<= 1;
+		blksize_shift++;
+	}
+	if ( blksize > ISO9660_BLKSIZE ) {
+		/* Cannot be a CD-ROM */
+		return 0;
+	}
+
+	/* Read primary volume descriptor */
+	memset ( &context, 0, sizeof ( context ) );
+	context.lba = ( ISO9660_PRIMARY_LBA << blksize_shift );
+	context.data = primary;
+	context.len = ISO9660_BLKSIZE;
+	context.block_rw = block_read;
+	if ( ( rc = efi_block_command ( block, efi_block_cmd_rw,
+					&context ) ) != 0 ) {
+		DBGC ( block, "EFIBLK %#02x could not read ISO9660 primary "
+		       "volume descriptor: %s\n",
+		       block->drive, strerror ( rc ) );
+		return rc;
+	}
+
+	/* Do nothing unless this is an ISO image */
+	if ( memcmp ( primary, &primary_check, sizeof ( primary_check ) ) != 0 )
+		return 0;
+	DBGC ( block, "EFIBLK %#02x contains an ISO9660 filesystem; treating "
+	       "as CD-ROM\n", block->drive );
+	block->blksize_shift = blksize_shift;
+
+	return 0;
+}
+
+/**
+ * Determing EFI block device capacity and block size
+ *
+ * @v block		Block device
+ * @ret rc		Return status code
+ */
+static int efi_block_capacity ( struct efi_block *block ) {
+	size_t scratch_len;
+	void *scratch;
+	int rc;
+
+	/* Read read block capacity */
+	if ( ( rc = efi_block_command ( block, efi_block_cmd_read_capacity,
+					NULL ) ) != 0 )
+		goto err_read_capacity;
+	block->blksize_shift = 0;
+
+	/* Allocate scratch area */
+	scratch_len = ( block->capacity.blksize );
+	if ( scratch_len < ISO9660_BLKSIZE )
+		scratch_len = ISO9660_BLKSIZE;
+	scratch = malloc ( scratch_len );
+	if ( ! scratch ) {
+		rc = -ENOMEM;
+		goto err_alloc;
+	}
+
+	/* Configure as a CD-ROM, if applicable */
+	if ( ( rc = efi_block_parse_iso9660 ( block, scratch ) ) != 0 )
+		goto err_parse_iso9660;
+
+	/* Update media descriptor */
+	block->media.BlockSize =
+		( block->capacity.blksize << block->blksize_shift );
+	block->media.LastBlock =
+		( ( block->capacity.blocks >> block->blksize_shift ) - 1 );
+
+	/* Success */
+	rc = 0;
+
+ err_parse_iso9660:
+	free ( scratch );
+ err_alloc:
+ err_read_capacity:
+	return rc;
+}
+
+/**
+ * Connect all possible drivers to EFI block device
+ *
+ * @v block		Block device
+ */
+static void efi_block_connect ( struct efi_block *block ) {
+	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
+	EFI_STATUS efirc;
+	int rc;
+
+	/* Try to connect all possible drivers to this block device */
+	if ( ( efirc = bs->ConnectController ( block->handle, NULL,
+					       NULL, 1 ) ) != 0 ) {
+		rc = -EEFI ( efirc );
+		DBGC ( block, "EFIBLK %#02x could not connect drivers: %s\n",
+		       block->drive, strerror ( rc ) );
+		/* May not be an error; may already be connected */
+	}
+	DBGC2 ( block, "EFIBLK %#02x supports protocols:\n", block->drive );
+	DBGC2_EFI_PROTOCOLS ( block, block->handle );
+}
+
+/**
+ * Hook EFI block device
+ *
+ * @v uri		URI
+ * @v drive		Drive number
+ * @ret drive		Drive number, or negative error
+ */
+static int efi_block_hook ( struct uri *uri, unsigned int drive ) {
+	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
+	struct efi_snp_device *snpdev;
+	struct efi_block *block;
+	EFI_STATUS efirc;
+	int rc;
+
+	/* Check that drive number is not already in use */
+	if ( efi_block_find ( drive ) ) {
+		rc = -EADDRINUSE;
+		goto err_in_use;
+	}
+
+	/* Allocate and initialise structure */
+	block = zalloc ( sizeof ( *block ) );
+	if ( ! block ) {
+		rc = -ENOMEM;
+		goto err_zalloc;
+	}
+	ref_init ( &block->refcnt, efi_block_free );
+	intf_init ( &block->intf, &efi_block_desc, &block->refcnt );
+	block->uri = uri_get ( uri );
+	block->drive = drive;
+	block->block_rc = -EINPROGRESS;
+	block->media.MediaPresent = 1;
+	block->media.LogicalBlocksPerPhysicalBlock = 1;
+	block->block_io.Revision = EFI_BLOCK_IO_PROTOCOL_REVISION3;
+	block->block_io.Media = &block->media;
+	block->block_io.Reset = efi_block_io_reset;
+	block->block_io.ReadBlocks = efi_block_io_read;
+	block->block_io.WriteBlocks = efi_block_io_write;
+	block->block_io.FlushBlocks = efi_block_io_flush;
+	intf_init ( &block->command, &efi_block_cmd_desc, &block->refcnt );
+	timer_init ( &block->timer, efi_block_cmd_expired, &block->refcnt );
+
+	/* Find an appropriate parent device handle */
+	snpdev = last_opened_snpdev();
+	if ( ! snpdev ) {
+		DBGC ( block, "EFIBLK %#02x could not identify SNP device\n",
+		       block->drive );
+		rc = -ENODEV;
+		goto err_no_snpdev;
+	}
+
+	/* Construct device path */
+	block->path = efi_block_path ( block->uri, snpdev->path );
+	if ( ! block->path ) {
+		rc = -ENOMEM;
+		goto err_path;
+	}
+	DBGC ( block, "EFIBLK %#02x has device path %s\n",
+	       block->drive, efi_devpath_text ( block->path ) );
+
+	/* Add to list of block devices */
+	list_add ( &block->list, &efi_block_devices );
+
+	/* Open block device interface */
+	if ( ( rc = efi_block_reopen ( block ) ) != 0 )
+		goto err_reopen;
+
+	/* Determine capacity and block size */
+	if ( ( rc = efi_block_capacity ( block ) ) != 0 )
+		goto err_capacity;
+
+	/* Install protocols */
+	if ( ( efirc = bs->InstallMultipleProtocolInterfaces (
+			&block->handle,
+			&efi_block_io_protocol_guid, &block->block_io,
+			&efi_device_path_protocol_guid, block->path,
+			NULL ) ) != 0 ) {
+		rc = -EEFI ( efirc );
+		DBGC ( block, "EFIBLK %#02x could not install protocols: %s\n",
+		       block->drive, strerror ( rc ) );
+		goto err_install;
+	}
+
+	/* Connect all possible protocols */
+	efi_block_connect ( block );
+
+	return drive;
+
+	bs->UninstallMultipleProtocolInterfaces (
+			block->handle,
+			&efi_block_io_protocol_guid, &block->block_io,
+			&efi_device_path_protocol_guid, block->path, NULL );
+ err_install:
+ err_capacity:
+	efi_block_restart ( block, rc );
+	intf_shutdown ( &block->intf, rc );
+ err_reopen:
+	list_del ( &block->list );
+ err_no_snpdev:
+ err_path:
+	ref_put ( &block->refcnt );
+ err_zalloc:
+ err_in_use:
+	return rc;
+}
+
+/**
+ * Unhook EFI block device
+ *
+ * @v drive		Drive number
+ */
+static void efi_block_unhook ( unsigned int drive ) {
+	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
+	struct efi_block *block;
+
+	/* Find block device */
+	block = efi_block_find ( drive );
+	if ( ! block ) {
+		DBG ( "EFIBLK cannot find drive %#02x\n", drive );
+		return;
+	}
+
+	/* Uninstall protocols */
+	bs->UninstallMultipleProtocolInterfaces (
+			block->handle,
+			&efi_block_io_protocol_guid, &block->block_io,
+			&efi_device_path_protocol_guid, block->path, NULL );
+
+	/* Close any outstanding commands and shut down interface */
+	efi_block_restart ( block, 0 );
+	intf_shutdown ( &block->intf, 0 );
+
+	/* Remove from list of block devices */
+	list_del ( &block->list );
+
+	/* Drop list's reference to drive */
+	ref_put ( &block->refcnt );
+}
+
+/**
+ * Describe EFI block device
+ *
+ * @v drive		Drive number
+ * @ret rc		Return status code
+ */
+static int efi_block_describe ( unsigned int drive ) {
+	struct efi_block *block;
+
+	/* Find block device */
+	block = efi_block_find ( drive );
+	if ( ! block ) {
+		DBG ( "EFIBLK cannot find drive %#02x\n", drive );
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+/**
+ * Try booting from child device of EFI block device
+ *
+ * @v block		Block device
+ * @v handle		EFI handle
+ * @ret rc		Return status code
+ */
+static int efi_block_boot_image ( struct efi_block *block,
+				  EFI_HANDLE handle, EFI_HANDLE *image ) {
+	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
+	union {
+		EFI_DEVICE_PATH_PROTOCOL *path;
+		void *interface;
+	} path;
+	EFI_DEVICE_PATH_PROTOCOL *boot_path;
+	FILEPATH_DEVICE_PATH *filepath;
+	EFI_DEVICE_PATH_PROTOCOL *end;
+	size_t prefix_len;
+	size_t filepath_len;
+	size_t boot_path_len;
+	EFI_STATUS efirc;
+	int rc;
+
+	/* Identify device path */
+	if ( ( efirc = bs->OpenProtocol ( handle,
+					  &efi_device_path_protocol_guid,
+					  &path.interface, efi_image_handle,
+					  handle,
+					  EFI_OPEN_PROTOCOL_GET_PROTOCOL ))!=0){
+		DBGC ( block, "EFIBLK %#02x found filesystem with no device "
+		       "path??", block->drive );
+		rc = -EEFI ( efirc );
+		goto err_open_device_path;
+	}
+
+	/* Check if this device is a child of our block device */
+	end = efi_devpath_end ( block->path );
+	prefix_len = ( ( ( void * ) end ) - ( ( void * ) block->path ) );
+	if ( memcmp ( path.path, block->path, prefix_len ) != 0 ) {
+		/* Not a child device */
+		rc = -ENOTTY;
+		goto err_not_child;
+	}
+	DBGC ( block, "EFIBLK %#02x found child device %s\n",
+	       block->drive, efi_devpath_text ( path.path ) );
+
+	/* Construct device path for boot image */
+	end = efi_devpath_end ( path.path );
+	prefix_len = ( ( ( void * ) end ) - ( ( void * ) path.path ) );
+	filepath_len = ( SIZE_OF_FILEPATH_DEVICE_PATH +
+			 sizeof ( efi_block_boot_filename ) );
+	boot_path_len = ( prefix_len + filepath_len + sizeof ( *end ) );
+	boot_path = zalloc ( boot_path_len );
+	if ( ! boot_path ) {
+		rc = -ENOMEM;
+		goto err_alloc_path;
+	}
+	memcpy ( boot_path, path.path, prefix_len );
+	filepath = ( ( ( void * ) boot_path ) + prefix_len );
+	filepath->Header.Type = MEDIA_DEVICE_PATH;
+	filepath->Header.SubType = MEDIA_FILEPATH_DP;
+	filepath->Header.Length[0] = ( filepath_len & 0xff );
+	filepath->Header.Length[1] = ( filepath_len >> 8 );
+	memcpy ( filepath->PathName, efi_block_boot_filename,
+		 sizeof ( efi_block_boot_filename ) );
+	end = ( ( ( void * ) filepath ) + filepath_len );
+	end->Type = END_DEVICE_PATH_TYPE;
+	end->SubType = END_ENTIRE_DEVICE_PATH_SUBTYPE;
+	end->Length[0] = sizeof ( *end );
+	DBGC ( block, "EFIBLK %#02x trying to load %s\n",
+	       block->drive, efi_devpath_text ( boot_path ) );
+
+	/* Try loading boot image from this device */
+	if ( ( efirc = bs->LoadImage ( FALSE, efi_image_handle, boot_path,
+				       NULL, 0, image ) ) != 0 ) {
+		rc = -EEFI ( efirc );
+		DBGC ( block, "EFIBLK %#02x could not load image: %s\n",
+		       block->drive, strerror ( rc ) );
+		goto err_load_image;
+	}
+
+	/* Success */
+	rc = 0;
+
+ err_load_image:
+	free ( boot_path );
+ err_alloc_path:
+ err_not_child:
+ err_open_device_path:
+	return rc;
+}
+
+/**
+ * Boot from EFI block device
+ *
+ * @v drive		Drive number
+ * @ret rc		Return status code
+ */
+static int efi_block_boot ( unsigned int drive ) {
+	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
+	struct efi_block *block;
+	EFI_HANDLE *handles;
+	EFI_HANDLE image = NULL;
+	UINTN count;
+	unsigned int i;
+	EFI_STATUS efirc;
+	int rc;
+
+	/* Find block device */
+	block = efi_block_find ( drive );
+	if ( ! block ) {
+		DBG ( "EFIBLK cannot find drive %#02x\n", drive );
+		rc = -ENODEV;
+		goto err_block_find;
+	}
+
+	/* Connect all possible protocols */
+	efi_block_connect ( block );
+
+	/* Locate all handles supporting the Simple File System protocol */
+	if ( ( efirc = bs->LocateHandleBuffer (
+			ByProtocol, &efi_simple_file_system_protocol_guid,
+			NULL, &count, &handles ) ) != 0 ) {
+		rc = -EEFI ( efirc );
+		DBGC ( block, "EFIBLK %#02x cannot locate file systems: %s\n",
+		       block->drive, strerror ( rc ) );
+		goto err_locate_file_systems;
+	}
+
+	/* Try booting from any available child device containing a
+	 * suitable boot image.  This is something of a wild stab in
+	 * the dark, but should end up conforming to user expectations
+	 * most of the time.
+	 */
+	rc = -ENOENT;
+	for ( i = 0 ; i < count ; i++ ) {
+		if ( ( rc = efi_block_boot_image ( block, handles[i],
+						   &image ) ) != 0 )
+			continue;
+		DBGC ( block, "EFIBLK %#02x found boot image\n", block->drive );
+		efirc = bs->StartImage ( image, NULL, NULL );
+		rc = ( efirc ? -EEFI ( efirc ) : 0 );
+		bs->UnloadImage ( image );
+		DBGC ( block, "EFIBLK %#02x boot image returned: %s\n",
+		       block->drive, strerror ( rc ) );
+		break;
+	}
+
+	bs->FreePool ( handles );
+ err_locate_file_systems:
+ err_block_find:
+	return rc;
+}
+
+PROVIDE_SANBOOT_INLINE ( efi, san_default_drive );
+PROVIDE_SANBOOT ( efi, san_hook, efi_block_hook );
+PROVIDE_SANBOOT ( efi, san_unhook, efi_block_unhook );
+PROVIDE_SANBOOT ( efi, san_describe, efi_block_describe );
+PROVIDE_SANBOOT ( efi, san_boot, efi_block_boot );