efi_block.c

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/*
 * 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 <stdio.h>
#include <string.h>
#include <strings.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/acpi.h>
#include <ipxe/efi/efi.h>
#include <ipxe/efi/Protocol/BlockIo.h>
#include <ipxe/efi/Protocol/SimpleFileSystem.h>
#include <ipxe/efi/Protocol/AcpiTable.h>
#include <ipxe/efi/Guid/FileSystemInfo.h>
#include <ipxe/efi/efi_driver.h>
#include <ipxe/efi/efi_strings.h>
#include <ipxe/efi/efi_snp.h>
#include <ipxe/efi/efi_path.h>
#include <ipxe/efi/efi_null.h>
#include <ipxe/efi/efi_wrap.h>
#include <ipxe/efi/efi_block.h>

/** ACPI table protocol protocol */
static EFI_ACPI_TABLE_PROTOCOL *acpi;
EFI_REQUEST_PROTOCOL ( EFI_ACPI_TABLE_PROTOCOL, &acpi );

/** Boot filename */
static wchar_t efi_block_boot_filename[] = EFI_REMOVABLE_MEDIA_FILE_NAME;

/** EFI SAN device private data */
struct efi_block_data {
        /** SAN device */
        struct san_device *sandev;
        /** 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;
};

/**
 * Read from or write to EFI block device
 *
 * @v sandev            SAN device
 * @v lba               Starting LBA
 * @v data              Data buffer
 * @v len               Size of buffer
 * @v sandev_rw         SAN device read/write method
 * @ret rc              Return status code
 */
static int efi_block_rw ( struct san_device *sandev, uint64_t lba,
                          void *data, size_t len,
                          int ( * sandev_rw ) ( struct san_device *sandev,
                                                uint64_t lba,
                                                unsigned int count,
                                                void *buffer ) ) {
        struct efi_block_data *block = sandev->priv;
        unsigned int count;
        int rc;

        /* Sanity check */
        count = ( len / block->media.BlockSize );
        if ( ( count * block->media.BlockSize ) != len ) {
                DBGC ( sandev->drive, "EFIBLK %#02x impossible length %#zx\n",
                       sandev->drive, len );
                return -EINVAL;
        }

        /* Read from / write to block device */
        if ( ( rc = sandev_rw ( sandev, lba, count, data ) ) != 0 ) {
                DBGC ( sandev->drive, "EFIBLK %#02x I/O failed: %s\n",
                       sandev->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_data *block =
                container_of ( block_io, struct efi_block_data, block_io );
        struct san_device *sandev = block->sandev;
        int rc;

        DBGC2 ( sandev->drive, "EFIBLK %#02x reset\n", sandev->drive );
        efi_snp_claim();
        rc = sandev_reset ( sandev );
        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_data *block =
                container_of ( block_io, struct efi_block_data, block_io );
        struct san_device *sandev = block->sandev;
        int rc;

        DBGC2 ( sandev->drive, "EFIBLK %#02x read LBA %#08llx to %p+%#08zx\n",
                sandev->drive, lba, data, ( ( size_t ) len ) );
        efi_snp_claim();
        rc = efi_block_rw ( sandev, lba, data, len, sandev_read );
        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_data *block =
                container_of ( block_io, struct efi_block_data, block_io );
        struct san_device *sandev = block->sandev;
        int rc;

        DBGC2 ( sandev->drive, "EFIBLK %#02x write LBA %#08llx from "
                "%p+%#08zx\n", sandev->drive, lba, data, ( ( size_t ) len ) );
        efi_snp_claim();
        rc = efi_block_rw ( sandev, lba, data, len, sandev_write );
        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_data *block =
                container_of ( block_io, struct efi_block_data, block_io );
        struct san_device *sandev = block->sandev;

        DBGC2 ( sandev->drive, "EFIBLK %#02x flush\n", sandev->drive );

        /* Nothing to do */
        return 0;
}

/**
 * Connect all possible drivers to EFI block device
 *
 * @v drive             Drive number
 * @v handle            Block device handle
 */
static void efi_block_connect ( unsigned int drive, EFI_HANDLE handle ) {
        int rc;

        /* Try to connect all possible drivers to this block device */
        if ( ( rc = efi_connect ( handle, NULL ) ) != 0 ) {
                DBGC ( drive, "EFIBLK %#02x could not connect drivers: %s\n",
                       drive, strerror ( rc ) );
                /* May not be an error; may already be connected */
        }
        DBGC2 ( drive, "EFIBLK %#02x supports protocols:\n", drive );
        DBGC2_EFI_PROTOCOLS ( drive, handle );
}

/**
 * Hook EFI block device
 *
 * @v drive             Drive number
 * @v uris              List of URIs
 * @v count             Number of URIs
 * @v flags             Flags
 * @ret drive           Drive number, or negative error
 */
static int efi_block_hook ( unsigned int drive, struct uri **uris,
                            unsigned int count, unsigned int flags ) {
        EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
        struct san_device *sandev;
        struct efi_block_data *block;
        int leak = 0;
        EFI_STATUS efirc;
        int rc;

        /* Sanity check */
        if ( ! count ) {
                DBGC ( drive, "EFIBLK %#02x has no URIs\n", drive );
                rc = -ENOTTY;
                goto err_no_uris;
        }

        /* Allocate and initialise structure */
        sandev = alloc_sandev ( uris, count, sizeof ( *block ) );
        if ( ! sandev ) {
                rc = -ENOMEM;
                goto err_alloc;
        }
        block = sandev->priv;
        block->sandev = sandev;
        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;

        /* Register SAN device */
        if ( ( rc = register_sandev ( sandev, drive, flags ) ) != 0 ) {
                DBGC ( drive, "EFIBLK %#02x could not register: %s\n",
                       drive, strerror ( rc ) );
                goto err_register;
        }

        /* Update media descriptor */
        block->media.BlockSize =
                ( sandev->capacity.blksize << sandev->blksize_shift );
        block->media.LastBlock =
                ( ( sandev->capacity.blocks >> sandev->blksize_shift ) - 1 );

        /* Construct device path */
        if ( ! sandev->active ) {
                rc = -ENODEV;
                DBGC ( drive, "EFIBLK %#02x not active after registration\n",
                       drive );
                goto err_active;
        }
        block->path = efi_describe ( &sandev->active->block );
        if ( ! block->path ) {
                rc = -ENODEV;
                DBGC ( drive, "EFIBLK %#02x has no device path\n", drive );
                goto err_describe;
        }
        DBGC2 ( drive, "EFIBLK %#02x has device path %s\n",
                drive, efi_devpath_text ( block->path ) );

        /* 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 ( drive, "EFIBLK %#02x could not install protocols: %s\n",
                       drive, strerror ( rc ) );
                goto err_install;
        }
        DBGC ( drive, "EFIBLK %#02x installed as SAN drive %s\n",
               drive, efi_handle_name ( block->handle ) );

        /* Connect all possible protocols */
        efi_block_connect ( drive, block->handle );

        return drive;

        if ( ( efirc = bs->UninstallMultipleProtocolInterfaces (
                        block->handle,
                        &efi_block_io_protocol_guid, &block->block_io,
                        &efi_device_path_protocol_guid, block->path,
                        NULL ) ) != 0 ) {
                DBGC ( drive, "EFIBLK %#02x could not uninstall protocols: "
                       "%s\n", drive, strerror ( -EEFI ( efirc ) ) );
                leak = 1;
        }
        efi_nullify_block ( &block->block_io );
 err_install:
        if ( ! leak )  {
                free ( block->path );
                block->path = NULL;
        }
 err_describe:
 err_active:
        unregister_sandev ( sandev );
 err_register:
        if ( ! leak )
                sandev_put ( sandev );
 err_alloc:
 err_no_uris:
        if ( leak )
                DBGC ( drive, "EFIBLK %#02x nullified and leaked\n", drive );
        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 san_device *sandev;
        struct efi_block_data *block;
        int leak = efi_shutdown_in_progress;
        EFI_STATUS efirc;

        /* Find SAN device */
        sandev = sandev_find ( drive );
        if ( ! sandev ) {
                DBGC ( drive, "EFIBLK %#02x is not a SAN drive\n", drive );
                return;
        }
        block = sandev->priv;

        /* Uninstall protocols */
        if ( ( ! efi_shutdown_in_progress ) &&
             ( ( efirc = bs->UninstallMultipleProtocolInterfaces (
                        block->handle,
                        &efi_block_io_protocol_guid, &block->block_io,
                        &efi_device_path_protocol_guid, block->path,
                        NULL ) ) != 0 ) ) {
                DBGC ( drive, "EFIBLK %#02x could not uninstall protocols: "
                       "%s\n", drive, strerror ( -EEFI ( efirc ) ) );
                leak = 1;
        }
        efi_nullify_block ( &block->block_io );

        /* Free device path */
        if ( ! leak ) {
                free ( block->path );
                block->path = NULL;
        }

        /* Unregister SAN device */
        unregister_sandev ( sandev );

        /* Drop reference to drive */
        if ( ! leak )
                sandev_put ( sandev );

        /* Report leakage, if applicable */
        if ( leak && ( ! efi_shutdown_in_progress ) )
                DBGC ( drive, "EFIBLK %#02x nullified and leaked\n", drive );
}

/** An installed ACPI table */
struct efi_acpi_table {
        /** List of installed tables */
        struct list_head list;
        /** Table key */
        UINTN key;
};

/** List of installed ACPI tables */
static LIST_HEAD ( efi_acpi_tables );

/**
 * Install ACPI table
 *
 * @v hdr               ACPI description header
 * @ret rc              Return status code
 */
static int efi_block_install ( struct acpi_header *hdr ) {
        size_t len = le32_to_cpu ( hdr->length );
        struct efi_acpi_table *installed;
        EFI_STATUS efirc;
        int rc;

        /* Allocate installed table record */
        installed = zalloc ( sizeof ( *installed ) );
        if ( ! installed ) {
                rc = -ENOMEM;
                goto err_alloc;
        }

        /* Fill in common parameters */
        strncpy ( hdr->oem_id, "FENSYS", sizeof ( hdr->oem_id ) );
        strncpy ( hdr->oem_table_id, "iPXE", sizeof ( hdr->oem_table_id ) );

        /* Fix up ACPI checksum */
        acpi_fix_checksum ( hdr );

        /* Install table */
        if ( ( efirc = acpi->InstallAcpiTable ( acpi, hdr, len,
                                                &installed->key ) ) != 0 ){
                rc = -EEFI ( efirc );
                DBGC ( acpi, "EFIBLK could not install %s: %s\n",
                       acpi_name ( hdr->signature ), strerror ( rc ) );
                DBGC2_HDA ( acpi, 0, hdr, len );
                goto err_install;
        }

        /* Add to list of installed tables */
        list_add_tail ( &installed->list, &efi_acpi_tables );

        DBGC ( acpi, "EFIBLK installed %s as ACPI table %#lx\n",
               acpi_name ( hdr->signature ),
               ( ( unsigned long ) installed->key ) );
        DBGC2_HDA ( acpi, 0, hdr, len );
        return 0;

        list_del ( &installed->list );
 err_install:
        free ( installed );
 err_alloc:
        return rc;
}

/**
 * Describe EFI block devices
 *
 * @ret rc              Return status code
 */
static int efi_block_describe ( void ) {
        struct efi_acpi_table *installed;
        struct efi_acpi_table *tmp;
        UINTN key;
        EFI_STATUS efirc;
        int rc;

        /* Sanity check */
        if ( ! acpi ) {
                DBG ( "EFIBLK has no ACPI table protocol\n" );
                return -ENOTSUP;
        }

        /* Uninstall any existing ACPI tables */
        list_for_each_entry_safe ( installed, tmp, &efi_acpi_tables, list ) {
                key = installed->key;
                if ( ( efirc = acpi->UninstallAcpiTable ( acpi, key ) ) != 0 ) {
                        rc = -EEFI ( efirc );
                        DBGC ( acpi, "EFIBLK could not uninstall ACPI table "
                               "%#lx: %s\n", ( ( unsigned long ) key ),
                               strerror ( rc ) );
                        /* Continue anyway */
                }
                list_del ( &installed->list );
                free ( installed );
        }

        /* Install ACPI tables */
        if ( ( rc = acpi_install ( efi_block_install ) ) != 0 )  {
                DBGC ( acpi, "EFIBLK could not install ACPI tables: %s\n",
                       strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Open root directory within a filesystem
 *
 * @v drive             Drive number
 * @v handle            Filesystem handle
 * @v root              Root directory file to fill in
 * @ret rc              Return status code
 */
static int efi_block_root ( unsigned int drive, EFI_HANDLE handle,
                            EFI_FILE_PROTOCOL **root ) {
        EFI_SIMPLE_FILE_SYSTEM_PROTOCOL *fs;
        EFI_STATUS efirc;
        int rc;

        /* Open filesystem protocol */
        if ( ( rc = efi_open ( handle, &efi_simple_file_system_protocol_guid,
                               &fs ) ) != 0 ) {
                DBGC ( drive, "EFIBLK %#02x could not open %s filesystem: %s\n",
                       drive, efi_handle_name ( handle ), strerror ( rc ) );
                return rc;
        }

        /* Open root volume */
        if ( ( efirc = fs->OpenVolume ( fs, root ) ) != 0 ) {
                rc = -EEFI ( efirc );
                DBGC ( drive, "EFIBLK %#02x could not open %s root: %s\n",
                       drive, efi_handle_name ( handle ), strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Check for existence of a file within a filesystem
 *
 * @v drive             Drive number
 * @v handle            Filesystem handle
 * @v root              Root directory
 * @v filename          Filename (or NULL to use default)
 * @ret rc              Return status code
 */
static int efi_block_filename ( unsigned int drive, EFI_HANDLE handle,
                                EFI_FILE_PROTOCOL *root,
                                const char *filename ) {
        CHAR16 tmp[ filename ? ( strlen ( filename ) + 1 /* wNUL */ ) : 0 ];
        CHAR16 *wname;
        EFI_FILE_PROTOCOL *file;
        EFI_STATUS efirc;
        int rc;

        /* Construct filename */
        if ( filename ) {
                efi_snprintf ( tmp, sizeof ( tmp ), "%s", filename );
                wname = tmp;
        } else {
                wname = efi_block_boot_filename;
        }

        /* Try opening file */
        if ( ( efirc = root->Open ( root, &file, wname,
                                    EFI_FILE_MODE_READ, 0 ) ) != 0 ) {
                rc = -EEFI ( efirc );
                DBGC ( drive, "EFIBLK %#02x could not open %s/%ls: %s\n",
                       drive, efi_handle_name ( handle ), wname,
                       strerror ( rc ) );
                goto err_file;
        }

        /* Success */
        rc = 0;

        file->Close ( file );
 err_file:
        return rc;
}

/**
 * Check for EFI block device filesystem label
 *
 * @v drive             Drive number
 * @v root              Root directory
 * @v label             Volume label
 * @ret rc              Return status code
 */
static int efi_block_label ( unsigned int drive, EFI_FILE_PROTOCOL *root,
                             const char *label ) {
        EFI_FILE_SYSTEM_INFO *info;
        UINTN size;
        char *actual;
        EFI_STATUS efirc;
        int rc;

        /* Get length of file system information */
        size = 0;
        root->GetInfo ( root, &efi_file_system_info_id, &size, NULL );

        /* Allocate file system information */
        info = malloc ( size );
        if ( ! info ) {
                rc = -ENOMEM;
                goto err_alloc_info;
        }

        /* Get file system information */
        if ( ( efirc = root->GetInfo ( root, &efi_file_system_info_id, &size,
                                       info ) ) != 0 ) {
                rc = -EEFI ( efirc );
                DBGC ( drive, "EFIBLK %#02x could not get filesystem info: "
                       "%s\n", drive, strerror ( rc ) );
                goto err_get_info;
        }

        /* Construct volume label for comparison */
        if ( asprintf ( &actual, "%ls", info->VolumeLabel ) < 0 ) {
                rc = -ENOMEM;
                goto err_alloc_label;
        }

        /* Compare volume label */
        if ( strcasecmp ( label, actual ) != 0 ) {
                DBGC ( drive, "EFIBLK %#02x has wrong label \"%s\"\n",
                       drive, actual );
                rc = -ENOENT;
                goto err_compare;
        }

        /* Success */
        rc = 0;

 err_compare:
        free ( actual );
 err_alloc_label:
 err_get_info:
        free ( info );
 err_alloc_info:
        return rc;
}

/**
 * Check EFI block device filesystem match
 *
 * @v drive             Drive number
 * @v handle            Filesystem handle
 * @v path              Block device path
 * @v config            Boot configuration parameters
 * @v fspath            Filesystem device path to fill in
 * @ret rc              Return status code
 */
static int efi_block_match ( unsigned int drive, EFI_HANDLE handle,
                             EFI_DEVICE_PATH_PROTOCOL *path,
                             struct san_boot_config *config,
                             EFI_DEVICE_PATH_PROTOCOL **fspath ) {
        EFI_FILE *root;
        union uuid guid;
        int rc;

        /* Identify device path */
        if ( ( rc = efi_open ( handle, &efi_device_path_protocol_guid,
                               fspath ) ) != 0 ) {
                DBGC ( drive, "EFIBLK %#02x could not open %s device path: "
                       "%s\n", drive, efi_handle_name ( handle ),
                       strerror ( rc ) );
                goto err_open;
        }

        /* Check if filesystem is a child of this block device */
        if ( memcmp ( *fspath, path, efi_path_len ( path ) ) != 0 ) {
                /* Not a child device */
                rc = -ENOTTY;
                DBGC2 ( drive, "EFIBLK %#02x is not parent of %s\n",
                        drive, efi_handle_name ( handle ) );
                goto err_not_child;
        }
        DBGC ( drive, "EFIBLK %#02x contains filesystem %s\n",
               drive, efi_devpath_text ( *fspath ) );

        /* Check if filesystem matches GUID, if applicable */
        if ( config->uuid ) {
                if ( ( rc = efi_path_guid ( *fspath, &guid ) ) != 0 ) {
                        DBGC ( drive, "EFIBLK %#02x could not determine GUID: "
                               "%s\n", drive, strerror ( rc ) );
                        goto err_no_guid;
                }
                if ( memcmp ( config->uuid, &guid, sizeof ( guid ) ) != 0 ) {
                        DBGC ( drive, "EFIBLK %#02x has wrong GUID %s\n",
                               drive, uuid_ntoa ( &guid ) );
                        rc = -ENOENT;
                        goto err_wrong_guid;
                }
        }

        /* Open root directory */
        if ( ( rc = efi_block_root ( drive, handle, &root ) ) != 0 )
                goto err_root;

        /* Check if filesystem contains boot filename */
        if ( ( rc = efi_block_filename ( drive, handle, root,
                                         config->filename ) ) != 0 ) {
                goto err_filename;
        }

        /* Check if filesystem contains additional filename, if applicable */
        if ( config->extra &&
             ( ( rc = efi_block_filename ( drive, handle, root,
                                           config->extra ) ) != 0 ) ) {
                goto err_extra;
        }

        /* Check volume label, if applicable */
        if ( config->label &&
             ( ( rc = efi_block_label ( drive, root,
                                        config->label ) ) != 0 ) ) {
                goto err_label;
        }

        /* Success */
        rc = 0;

 err_label:
 err_extra:
 err_filename:
        root->Close ( root );
 err_root:
 err_wrong_guid:
 err_no_guid:
 err_not_child:
 err_open:
        return rc;
}

/**
 * Scan EFI block device for a matching filesystem
 *
 * @v drive             Drive number
 * @v handle            Block device handle
 * @v config            Boot configuration parameters
 * @v fspath            Filesystem device path to fill in
 * @ret rc              Return status code
 */
static int efi_block_scan ( unsigned int drive, EFI_HANDLE handle,
                            struct san_boot_config *config,
                            EFI_DEVICE_PATH_PROTOCOL **fspath ) {
        EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
        EFI_DEVICE_PATH_PROTOCOL *path;
        EFI_HANDLE *handles;
        UINTN count;
        unsigned int i;
        EFI_STATUS efirc;
        int rc;

        /* Connect up possible file system drivers */
        efi_block_connect ( drive, handle );

        /* Identify device path */
        if ( ( rc = efi_open ( handle, &efi_device_path_protocol_guid,
                               &path ) ) != 0 ) {
                DBGC ( drive, "EFIBLK %#02x could not open device path: %s\n",
                       drive, strerror ( rc ) );
                goto err_open;
        }

        /* Locate all Simple File System protocol handles */
        if ( ( efirc = bs->LocateHandleBuffer (
                        ByProtocol, &efi_simple_file_system_protocol_guid,
                        NULL, &count, &handles ) ) != 0 ) {
                rc = -EEFI ( efirc );
                DBGC ( drive, "EFIBLK %#02x cannot locate file systems: %s\n",
                       drive, strerror ( rc ) );
                goto err_locate;
        }

        /* Scan for a matching filesystem */
        rc = -ENOENT;
        for ( i = 0 ; i < count ; i++ ) {

                /* Check for a matching filesystem */
                if ( ( rc = efi_block_match ( drive, handles[i], path,
                                              config, fspath ) ) != 0 )
                        continue;

                break;
        }

        bs->FreePool ( handles );
 err_locate:
 err_open:
        return rc;
}

/**
 * Boot from EFI block device filesystem boot image
 *
 * @v drive             Drive number
 * @v fspath            Filesystem device path
 * @v filename          Filename (or NULL to use default)
 * @ret rc              Return status code
 */
static int efi_block_exec ( unsigned int drive,
                            EFI_DEVICE_PATH_PROTOCOL *fspath,
                            const char *filename ) {
        EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
        EFI_DEVICE_PATH_PROTOCOL *path;
        FILEPATH_DEVICE_PATH *filepath;
        EFI_DEVICE_PATH_PROTOCOL *end;
        EFI_HANDLE image;
        size_t fspath_len;
        size_t filepath_len;
        size_t path_len;
        EFI_STATUS efirc;
        int rc;

        /* Construct device path for boot image */
        end = efi_path_end ( fspath );
        fspath_len = ( ( ( void * ) end ) - ( ( void * ) fspath ) );
        filepath_len = ( SIZE_OF_FILEPATH_DEVICE_PATH +
                         ( filename ?
                           ( ( strlen ( filename ) + 1 /* NUL */ ) *
                             sizeof ( filepath->PathName[0] ) ) :
                           sizeof ( efi_block_boot_filename ) ) );
        path_len = ( fspath_len + filepath_len + sizeof ( *end ) );
        path = zalloc ( path_len );
        if ( ! path ) {
                rc = -ENOMEM;
                goto err_alloc;
        }
        memcpy ( path, fspath, fspath_len );
        filepath = ( ( ( void * ) path ) + fspath_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 );
        if ( filename ) {
                efi_sprintf ( filepath->PathName, "%s", filename );
        } else {
                memcpy ( filepath->PathName, efi_block_boot_filename,
                         sizeof ( efi_block_boot_filename ) );
        }
        end = ( ( ( void * ) filepath ) + filepath_len );
        efi_path_terminate ( end );
        DBGC ( drive, "EFIBLK %#02x trying to load %s\n",
               drive, efi_devpath_text ( path ) );

        /* Load image */
        image = NULL;
        if ( ( efirc = bs->LoadImage ( FALSE, efi_image_handle, path, NULL, 0,
                                       &image ) ) != 0 ) {
                rc = -EEFI ( efirc );
                DBGC ( drive, "EFIBLK %#02x could not load: %s\n",
                       drive, strerror ( rc ) );
                if ( efirc == EFI_SECURITY_VIOLATION ) {
                        goto err_load_security_violation;
                } else {
                        goto err_load;
                }
        }

        /* Wrap calls made by the loaded image (for debugging) */
        efi_wrap_image ( image );

        /* Start image */
        efirc = bs->StartImage ( image, NULL, NULL );
        rc = ( efirc ? -EEFI ( efirc ) : 0 );
        DBGC ( drive, "EFIBLK %#02x boot image returned: %s\n",
               drive, strerror ( rc ) );

        /* Remove wrapper */
        efi_unwrap();

 err_load_security_violation:
        bs->UnloadImage ( image );
 err_load:
        free ( path );
 err_alloc:
        return rc;
}

/**
 * Check that EFI block device is eligible for a local virtual drive number
 *
 * @v handle            Block device handle
 * @ret rc              Return status code
 *
 * We assign virtual drive numbers for local (non-SAN) EFI block
 * devices that represent complete disks, to provide roughly
 * equivalent functionality to BIOS drive numbers.
 */
static int efi_block_local ( EFI_HANDLE handle ) {
        struct san_device *sandev;
        struct efi_block_data *block;
        EFI_BLOCK_IO_PROTOCOL *blockio;
        int rc;

        /* Check if handle belongs to a SAN device */
        for_each_sandev ( sandev ) {
                block = sandev->priv;
                if ( handle == block->handle )
                        return -ENOTTY;
        }

        /* Open block I/O protocol */
        if ( ( rc = efi_open ( handle, &efi_block_io_protocol_guid,
                               &blockio ) ) != 0 ) {
                DBGC ( handle, "EFIBLK %s could not open block I/O: %s\n",
                       efi_handle_name ( handle ), strerror ( rc ) );
                return rc;
        }

        /* Do not assign drive numbers for partitions */
        if ( blockio->Media->LogicalPartition ) {
                DBGC2 ( handle, "EFLBLK %s is a partition\n",
                        efi_handle_name ( handle ) );
                return -ENOTTY;
        }

        return 0;
}

/**
 * Boot from EFI block device
 *
 * @v drive             Drive number
 * @v config            Boot configuration parameters
 * @ret rc              Return status code
 */
static int efi_block_boot ( unsigned int drive,
                            struct san_boot_config *config ) {
        EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
        EFI_DEVICE_PATH_PROTOCOL *fspath = NULL;
        EFI_HANDLE *handles;
        EFI_HANDLE handle;
        UINTN count;
        struct san_device *sandev;
        struct efi_block_data *block;
        unsigned int vdrive;
        unsigned int index;
        EFI_STATUS efirc;
        int rc;

        /* Ensure that any local drives are connected */
        efi_driver_reconnect_all();

        /* Release SNP devices */
        efi_snp_release();

        /* Locate all block I/O protocol handles */
        if ( ( efirc = bs->LocateHandleBuffer ( ByProtocol,
                                                &efi_block_io_protocol_guid,
                                                NULL, &count,
                                                &handles ) ) != 0 ) {
                rc = -EEFI ( efirc );
                DBGC ( drive, "EFIBLK %#02x cannot locate block I/O: %s\n",
                       drive, strerror ( rc ) );
                goto err_locate_block_io;
        }

        /* Try booting from the first matching block device, if any */
        rc = -ENOENT;
        for ( vdrive = 0, index = 0 ; ; vdrive++ ) {

                /* Identify next drive number and block I/O handle */
                if ( ( sandev = sandev_next ( vdrive ) ) &&
                     ( ( sandev->drive == vdrive ) ||
                       ( sandev->drive <= SAN_DEFAULT_DRIVE ) ||
                       ( index >= count ) ) ) {

                        /* There is a SAN drive that either:
                         *
                         * a) has the current virtual drive number, or
                         * b) has a drive number below SAN_DEFAULT_DRIVE, or
                         * c) has a drive number higher than any local drive
                         *
                         * Use this SAN drive, since the explicit SAN
                         * drive numbering takes precedence over the
                         * implicit local drive numbering.
                         */
                        block = sandev->priv;
                        handle = block->handle;

                        /* Use SAN drive's explicit drive number */
                        vdrive = sandev->drive;
                        DBGC ( vdrive, "EFIBLK %#02x is SAN drive %s\n",
                               vdrive, efi_handle_name ( handle ) );

                } else if ( index < count ) {

                        /* There is no SAN drive meeting any of the
                         * above criteria.  Try the next block I/O
                         * handle.
                         */
                        handle = handles[index++];

                        /* Check if this handle is eligible to be
                         * given a local virtual drive number.
                         *
                         * Do not record this as the overall error
                         * status, since it is not an interesting
                         * error.
                         */
                        if ( efi_block_local ( handle ) != 0 ) {
                                /* Do not consume virtual drive number */
                                vdrive--;
                                continue;
                        }

                        /* Use the current virtual drive number, with
                         * a minimum of SAN_DEFAULT_DRIVE to match
                         * typical BIOS drive numbering.
                         */
                        if ( vdrive < SAN_DEFAULT_DRIVE )
                                vdrive = SAN_DEFAULT_DRIVE;
                        DBGC ( vdrive, "EFIBLK %#02x is local drive %s\n",
                               vdrive, efi_handle_name ( handle ) );

                } else {

                        /* No more SAN or local drives */
                        break;
                }

                /* Skip non-matching drives */
                if ( drive && ( drive != vdrive ) )
                        continue;
                DBGC ( vdrive, "EFIBLK %#02x attempting to boot\n", vdrive );

                /* Scan for a matching filesystem within this drive */
                if ( ( rc = efi_block_scan ( vdrive, handle, config,
                                             &fspath ) ) != 0 ) {
                        continue;
                }

                /* Attempt to boot from the matched filesystem */
                rc = efi_block_exec ( vdrive, fspath, config->filename );
                break;
        }

        bs->FreePool ( handles );
 err_locate_block_io:
        efi_snp_claim();
        return rc;
}

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 );