[efi] Install our own disk I/O protocol and claim exclusive use of it

The EFI FAT filesystem driver has a bug: if a block device contains no
FAT filesystem but does have an EFI_SIMPLE_FILE_SYSTEM_PROTOCOL
instance, the FAT driver will assume that it must have previously
installed the EFI_SIMPLE_FILE_SYSTEM_PROTOCOL.  This causes the FAT
driver to claim control of our device, and to refuse to stop driving
it, which prevents us from later uninstalling correctly.

Work around this bug by opening the disk I/O protocol ourselves,
thereby preventing the FAT driver from opening it.

Note that the alternative approach of opening the block I/O protocol
(and thereby in theory preventing DiskIo from attaching to the block
I/O protocol) causes an endless loop of calls to our DRIVER_STOP
method when starting the EFI shell.  I have no idea why this is.

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

src/include/ipxe/efi/Protocol/DiskIo.h

@@ -0,0 +1,119 @@
+/** @file
+  Disk IO protocol as defined in the UEFI 2.0 specification.
+
+  The Disk IO protocol is used to convert block oriented devices into byte
+  oriented devices. The Disk IO protocol is intended to layer on top of the
+  Block IO protocol.
+
+  Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
+  This program and the accompanying materials
+  are licensed and made available under the terms and conditions of the BSD License
+  which accompanies this distribution.  The full text of the license may be found at
+  http://opensource.org/licenses/bsd-license.php
+
+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+
+**/
+
+#ifndef __DISK_IO_H__
+#define __DISK_IO_H__
+
+FILE_LICENCE ( BSD3 );
+
+#define EFI_DISK_IO_PROTOCOL_GUID \
+  { \
+    0xce345171, 0xba0b, 0x11d2, {0x8e, 0x4f, 0x0, 0xa0, 0xc9, 0x69, 0x72, 0x3b } \
+  }
+
+///
+/// Protocol GUID name defined in EFI1.1.
+///
+#define DISK_IO_PROTOCOL  EFI_DISK_IO_PROTOCOL_GUID
+
+typedef struct _EFI_DISK_IO_PROTOCOL EFI_DISK_IO_PROTOCOL;
+
+///
+/// Protocol defined in EFI1.1.
+///
+typedef EFI_DISK_IO_PROTOCOL  EFI_DISK_IO;
+
+/**
+  Read BufferSize bytes from Offset into Buffer.
+
+  @param  This                  Protocol instance pointer.
+  @param  MediaId               Id of the media, changes every time the media is replaced.
+  @param  Offset                The starting byte offset to read from
+  @param  BufferSize            Size of Buffer
+  @param  Buffer                Buffer containing read data
+
+  @retval EFI_SUCCESS           The data was read correctly from the device.
+  @retval EFI_DEVICE_ERROR      The device reported an error while performing the read.
+  @retval EFI_NO_MEDIA          There is no media in the device.
+  @retval EFI_MEDIA_CHNAGED     The MediaId does not matched the current device.
+  @retval EFI_INVALID_PARAMETER The read request contains device addresses that are not
+                                valid for the device.
+
+**/
+typedef
+EFI_STATUS
+(EFIAPI *EFI_DISK_READ)(
+  IN EFI_DISK_IO_PROTOCOL         *This,
+  IN UINT32                       MediaId,
+  IN UINT64                       Offset,
+  IN UINTN                        BufferSize,
+  OUT VOID                        *Buffer
+  );
+
+/**
+  Writes a specified number of bytes to a device.
+
+  @param  This       Indicates a pointer to the calling context.
+  @param  MediaId    ID of the medium to be written.
+  @param  Offset     The starting byte offset on the logical block I/O device to write.
+  @param  BufferSize The size in bytes of Buffer. The number of bytes to write to the device.
+  @param  Buffer     A pointer to the buffer containing the data to be written.
+
+  @retval EFI_SUCCESS           The data was written correctly to the device.
+  @retval EFI_WRITE_PROTECTED   The device can not be written to.
+  @retval EFI_DEVICE_ERROR      The device reported an error while performing the write.
+  @retval EFI_NO_MEDIA          There is no media in the device.
+  @retval EFI_MEDIA_CHNAGED     The MediaId does not matched the current device.
+  @retval EFI_INVALID_PARAMETER The write request contains device addresses that are not
+                                 valid for the device.
+
+**/
+typedef
+EFI_STATUS
+(EFIAPI *EFI_DISK_WRITE)(
+  IN EFI_DISK_IO_PROTOCOL         *This,
+  IN UINT32                       MediaId,
+  IN UINT64                       Offset,
+  IN UINTN                        BufferSize,
+  IN VOID                         *Buffer
+  );
+
+#define EFI_DISK_IO_PROTOCOL_REVISION 0x00010000
+
+///
+/// Revision defined in EFI1.1
+///
+#define EFI_DISK_IO_INTERFACE_REVISION  EFI_DISK_IO_PROTOCOL_REVISION
+
+///
+/// This protocol is used to abstract Block I/O interfaces.
+///
+struct _EFI_DISK_IO_PROTOCOL {
+  ///
+  /// The revision to which the disk I/O interface adheres. All future
+  /// revisions must be backwards compatible. If a future version is not
+  /// backwards compatible, it is not the same GUID.
+  ///
+  UINT64          Revision;
+  EFI_DISK_READ   ReadDisk;
+  EFI_DISK_WRITE  WriteDisk;
+};
+
+extern EFI_GUID gEfiDiskIoProtocolGuid;
+
+#endif

src/interface/efi/efi_file.c

@@ -36,6 +36,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #include <ipxe/efi/efi.h>
 #include <ipxe/efi/Protocol/SimpleFileSystem.h>
 #include <ipxe/efi/Protocol/BlockIo.h>
+#include <ipxe/efi/Protocol/DiskIo.h>
 #include <ipxe/efi/Guid/FileInfo.h>
 #include <ipxe/efi/Guid/FileSystemInfo.h>
 #include <ipxe/efi/efi_strings.h>
@@ -55,6 +56,10 @@ static EFI_GUID efi_file_system_info_id = EFI_FILE_SYSTEM_INFO_ID;
 static EFI_GUID efi_block_io_protocol_guid
 	= EFI_BLOCK_IO_PROTOCOL_GUID;
 
+/** EFI disk I/O protocol GUID */
+static EFI_GUID efi_disk_io_protocol_guid
+	= EFI_DISK_IO_PROTOCOL_GUID;
+
 /** EFI media ID */
 #define EFI_MEDIA_ID_MAGIC 0x69505845
 
@@ -506,7 +511,7 @@ static EFI_STATUS EFIAPI
 efi_block_io_read_blocks ( EFI_BLOCK_IO_PROTOCOL *this __unused,
 			   UINT32 MediaId __unused, EFI_LBA lba __unused,
 			   UINTN len __unused, VOID *data __unused ) {
-	return EFI_DEVICE_ERROR;
+	return EFI_NO_MEDIA;
 }
 
 /** Dummy block I/O write */
@@ -514,7 +519,7 @@ static EFI_STATUS EFIAPI
 efi_block_io_write_blocks ( EFI_BLOCK_IO_PROTOCOL *this __unused,
 			    UINT32 MediaId __unused, EFI_LBA lba __unused,
 			    UINTN len __unused, VOID *data __unused ) {
-	return EFI_DEVICE_ERROR;
+	return EFI_NO_MEDIA;
 }
 
 /** Dummy block I/O flush */
@@ -541,6 +546,29 @@ static EFI_BLOCK_IO_PROTOCOL efi_block_io_protocol = {
 	.FlushBlocks = efi_block_io_flush_blocks,
 };
 
+/** Dummy disk I/O read */
+static EFI_STATUS EFIAPI
+efi_disk_io_read_disk ( EFI_DISK_IO_PROTOCOL *this __unused,
+			UINT32 MediaId __unused, UINT64 offset __unused,
+			UINTN len __unused, VOID *data __unused ) {
+	return EFI_NO_MEDIA;
+}
+
+/** Dummy disk I/O write */
+static EFI_STATUS EFIAPI
+efi_disk_io_write_disk ( EFI_DISK_IO_PROTOCOL *this __unused,
+			 UINT32 MediaId __unused, UINT64 offset __unused,
+			 UINTN len __unused, VOID *data __unused ) {
+	return EFI_NO_MEDIA;
+}
+
+/** Dummy EFI disk I/O protocol */
+static EFI_DISK_IO_PROTOCOL efi_disk_io_protocol = {
+	.Revision = EFI_DISK_IO_PROTOCOL_REVISION,
+	.ReadDisk = efi_disk_io_read_disk,
+	.WriteDisk = efi_disk_io_write_disk,
+};
+
 /**
  * Install EFI simple file system protocol
  *
@@ -549,29 +577,79 @@ static EFI_BLOCK_IO_PROTOCOL efi_block_io_protocol = {
  */
 int efi_file_install ( EFI_HANDLE *handle ) {
 	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
+	union {
+		EFI_DISK_IO_PROTOCOL *diskio;
+		void *interface;
+	} diskio;
 	EFI_STATUS efirc;
 	int rc;
 
-	/* Install the simple file system protocol and the block I/O
-	 * protocol.  We don't have a block device, but large parts of
-	 * the EDK2 codebase make the assumption that file systems are
-	 * normally attached to block devices, and so we create a
-	 * dummy block device on the same handle just to keep things
-	 * looking normal.
+	/* Install the simple file system protocol, block I/O
+	 * protocol, and disk I/O protocol.  We don't have a block
+	 * device, but large parts of the EDK2 codebase make the
+	 * assumption that file systems are normally attached to block
+	 * devices, and so we create a dummy block device on the same
+	 * handle just to keep things looking normal.
 	 */
 	if ( ( efirc = bs->InstallMultipleProtocolInterfaces (
 			handle,
 			&efi_block_io_protocol_guid,
 			&efi_block_io_protocol,
+			&efi_disk_io_protocol_guid,
+			&efi_disk_io_protocol,
 			&efi_simple_file_system_protocol_guid,
 			&efi_simple_file_system_protocol, NULL ) ) != 0 ) {
 		rc = -EEFI ( efirc );
-		DBGC ( handle, "Could not install simple file system protocol: "
-		       "%s\n", strerror ( rc ) );
-		return rc;
+		DBGC ( handle, "Could not install simple file system "
+		       "protocols: %s\n", strerror ( rc ) );
+		goto err_install;
+	}
+
+	/* The FAT filesystem driver has a bug: if a block device
+	 * contains no FAT filesystem but does have an
+	 * EFI_SIMPLE_FILE_SYSTEM_PROTOCOL instance, the FAT driver
+	 * will assume that it must have previously installed the
+	 * EFI_SIMPLE_FILE_SYSTEM_PROTOCOL.  This causes the FAT
+	 * driver to claim control of our device, and to refuse to
+	 * stop driving it, which prevents us from later uninstalling
+	 * correctly.
+	 *
+	 * Work around this bug by opening the disk I/O protocol
+	 * ourselves, thereby preventing the FAT driver from opening
+	 * it.
+	 *
+	 * Note that the alternative approach of opening the block I/O
+	 * protocol (and thereby in theory preventing DiskIo from
+	 * attaching to the block I/O protocol) causes an endless loop
+	 * of calls to our DRIVER_STOP method when starting the EFI
+	 * shell.  I have no idea why this is.
+	 */
+	if ( ( efirc = bs->OpenProtocol ( *handle, &efi_disk_io_protocol_guid,
+					  &diskio.interface, efi_image_handle,
+					  *handle,
+					  EFI_OPEN_PROTOCOL_BY_DRIVER ) ) != 0){
+		rc = -EEFI ( efirc );
+		DBGC ( handle, "Could not open disk I/O protocol: %s\n",
+		       strerror ( rc ) );
+		goto err_open;
 	}
+	assert ( diskio.diskio == &efi_disk_io_protocol );
 
 	return 0;
+
+	bs->CloseProtocol ( *handle, &efi_disk_io_protocol_guid,
+			    efi_image_handle, *handle );
+ err_open:
+	bs->UninstallMultipleProtocolInterfaces (
+			*handle,
+			&efi_simple_file_system_protocol_guid,
+			&efi_simple_file_system_protocol,
+			&efi_disk_io_protocol_guid,
+			&efi_disk_io_protocol,
+			&efi_block_io_protocol_guid,
+			&efi_block_io_protocol, NULL );
+ err_install:
+	return rc;
 }
 
 /**
@@ -581,16 +659,29 @@ int efi_file_install ( EFI_HANDLE *handle ) {
  */
 void efi_file_uninstall ( EFI_HANDLE handle ) {
 	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
+	EFI_STATUS efirc;
+	int rc;
+
+	/* Close our own disk I/O protocol */
+	bs->CloseProtocol ( handle, &efi_disk_io_protocol_guid,
+			    efi_image_handle, handle );
 
 	/* We must install the file system protocol first, since
 	 * otherwise the EDK2 code will attempt to helpfully uninstall
 	 * it when the block I/O protocol is uninstalled, leading to a
 	 * system lock-up.
 	 */
-	bs->UninstallMultipleProtocolInterfaces (
+	if ( ( efirc = bs->UninstallMultipleProtocolInterfaces (
 			handle,
 			&efi_simple_file_system_protocol_guid,
 			&efi_simple_file_system_protocol,
+			&efi_disk_io_protocol_guid,
+			&efi_disk_io_protocol,
 			&efi_block_io_protocol_guid,
-			&efi_block_io_protocol, NULL );
+			&efi_block_io_protocol, NULL ) ) != 0 ) {
+		rc = -EEFI ( efirc );
+		DBGC ( handle, "Could not uninstall simple file system "
+		       "protocols: %s\n", strerror ( rc ) );
+		/* Oh dear */
+	}
 }