efi_file.c

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/*
 * Copyright (C) 2013 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 file protocols
 *
 */

#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <strings.h>
#include <errno.h>
#include <wchar.h>
#include <ipxe/image.h>
#include <ipxe/cpio.h>
#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>
#include <ipxe/efi/efi_file.h>

/** EFI media ID */
#define EFI_MEDIA_ID_MAGIC 0x69505845

/** An EFI virtual file reader */
struct efi_file_reader {
        /** EFI file */
        struct efi_file *file;
        /** Position within virtual file */
        size_t pos;
        /** Output data buffer */
        void *data;
        /** Length of output data buffer */
        size_t len;
};

/** An EFI file */
struct efi_file {
        /** Reference count */
        struct refcnt refcnt;
        /** EFI file protocol */
        EFI_FILE_PROTOCOL file;
        /** Image (if any) */
        struct image *image;
        /** Filename */
        const char *name;
        /** Current file position */
        size_t pos;
        /**
         * Read from file
         *
         * @v reader            File reader
         * @ret len             Length read
         */
        size_t ( * read ) ( struct efi_file_reader *reader );
};

static struct efi_file efi_file_root;
static struct efi_file efi_file_initrd;

/**
 * Free EFI file
 *
 * @v refcnt            Reference count
 */
static void efi_file_free ( struct refcnt *refcnt ) {
        struct efi_file *file =
                container_of ( refcnt, struct efi_file, refcnt );

        image_put ( file->image );
        free ( file );
}

/**
 * Get EFI file name (for debugging)
 *
 * @v file              EFI file
 * @ret name            Name
 */
static const char * efi_file_name ( struct efi_file *file ) {

        return ( file == &efi_file_root ? "<root>" : file->name );
}

/**
 * Find EFI file image
 *
 * @v name              Filename
 * @ret image           Image, or NULL
 */
static struct image * efi_file_find ( const char *name ) {
        struct image *image;

        /* Find image */
        list_for_each_entry ( image, &images, list ) {
                if ( strcasecmp ( image->name, name ) == 0 )
                        return image;
        }

        return NULL;
}

/**
 * Get length of EFI file
 *
 * @v file              EFI file
 * @ret len             Length of file
 */
static size_t efi_file_len ( struct efi_file *file ) {
        struct efi_file_reader reader;

        /* If this is the root directory, then treat as length zero */
        if ( ! file->read )
                return 0;

        /* Initialise reader */
        reader.file = file;
        reader.pos = 0;
        reader.data = NULL;
        reader.len = 0;

        /* Perform dummy read to determine file length */
        file->read ( &reader );

        return reader.pos;
}

/**
 * Read chunk of EFI file
 *
 * @v reader            EFI file reader
 * @v data              Input data, or UNULL to zero-fill
 * @v len               Length of input data
 * @ret len             Length of output data
 */
static size_t efi_file_read_chunk ( struct efi_file_reader *reader,
                                    userptr_t data, size_t len ) {
        struct efi_file *file = reader->file;
        size_t offset;

        /* Calculate offset into input data */
        offset = ( file->pos - reader->pos );

        /* Consume input data range */
        reader->pos += len;

        /* Calculate output length */
        if ( offset < len ) {
                len -= offset;
        } else {
                len = 0;
        }
        if ( len > reader->len )
                len = reader->len;

        /* Copy or zero output data */
        if ( data ) {
                copy_from_user ( reader->data, data, offset, len );
        } else {
                memset ( reader->data, 0, len );
        }

        /* Consume output buffer */
        file->pos += len;
        reader->data += len;
        reader->len -= len;

        return len;
}

/**
 * Read from image-backed file
 *
 * @v reader            EFI file reader
 * @ret len             Length read
 */
static size_t efi_file_read_image ( struct efi_file_reader *reader ) {
        struct efi_file *file = reader->file;
        struct image *image = file->image;

        /* Read from file */
        return efi_file_read_chunk ( reader, image->data, image->len );
}

/**
 * Read from magic initrd file
 *
 * @v reader            EFI file reader
 * @ret len             Length read
 */
static size_t efi_file_read_initrd ( struct efi_file_reader *reader ) {
        struct efi_file *file = reader->file;
        struct cpio_header cpio;
        struct image *image;
        const char *name;
        size_t pad_len;
        size_t cpio_len;
        size_t name_len;
        size_t len;

        /* Read from file */
        len = 0;
        for_each_image ( image ) {

                /* Ignore currently executing image */
                if ( image == current_image )
                        continue;

                /* Pad to alignment boundary */
                pad_len = ( ( -reader->pos ) & ( INITRD_ALIGN - 1 ) );
                if ( pad_len ) {
                        DBGC ( file, "EFIFILE %s [%#08zx,%#08zx) pad\n",
                               efi_file_name ( file ), reader->pos,
                               ( reader->pos + pad_len ) );
                }
                len += efi_file_read_chunk ( reader, UNULL, pad_len );

                /* Read CPIO header, if applicable */
                cpio_len = cpio_header ( image, &cpio );
                if ( cpio_len ) {
                        name = cpio_name ( image );
                        name_len = cpio_name_len ( image );
                        pad_len = ( cpio_len - sizeof ( cpio ) - name_len );
                        DBGC ( file, "EFIFILE %s [%#08zx,%#08zx) %s header\n",
                               efi_file_name ( file ), reader->pos,
                               ( reader->pos + cpio_len ), image->name );
                        len += efi_file_read_chunk ( reader,
                                                     virt_to_user ( &cpio ),
                                                     sizeof ( cpio ) );
                        len += efi_file_read_chunk ( reader,
                                                     virt_to_user ( name ),
                                                     name_len );
                        len += efi_file_read_chunk ( reader, UNULL, pad_len );
                }

                /* Read file data */
                DBGC ( file, "EFIFILE %s [%#08zx,%#08zx) %s\n",
                       efi_file_name ( file ), reader->pos,
                       ( reader->pos + image->len ), image->name );
                len += efi_file_read_chunk ( reader, image->data, image->len );
        }

        return len;
}

/**
 * Open fixed file
 *
 * @v file              EFI file
 * @v new               New EFI file
 * @ret efirc           EFI status code
 */
static EFI_STATUS efi_file_open_fixed ( struct efi_file *file,
                                        EFI_FILE_PROTOCOL **new ) {

        /* Increment reference count */
        ref_get ( &file->refcnt );

        /* Return opened file */
        *new = &file->file;

        DBGC ( file, "EFIFILE %s opened\n", efi_file_name ( file ) );
        return 0;
}

/**
 * Associate file with image
 *
 * @v file              EFI file
 * @v image             Image
 */
static void efi_file_image ( struct efi_file *file, struct image *image ) {

        file->image = image;
        file->name = image->name;
        file->read = efi_file_read_image;
}

/**
 * Open file
 *
 * @v this              EFI file
 * @ret new             New EFI file
 * @v wname             Filename
 * @v mode              File mode
 * @v attributes        File attributes (for newly-created files)
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_file_open ( EFI_FILE_PROTOCOL *this, EFI_FILE_PROTOCOL **new,
                CHAR16 *wname, UINT64 mode, UINT64 attributes __unused ) {
        struct efi_file *file = container_of ( this, struct efi_file, file );
        char buf[ wcslen ( wname ) + 1 /* NUL */ ];
        struct efi_file *new_file;
        struct image *image;
        char *name;

        /* Convert name to ASCII */
        snprintf ( buf, sizeof ( buf ), "%ls", wname );
        name = buf;

        /* Initial '\' indicates opening from the root directory */
        while ( *name == '\\' ) {
                file = &efi_file_root;
                name++;
        }

        /* Allow root directory itself to be opened */
        if ( ( name[0] == '\0' ) || ( name[0] == '.' ) )
                return efi_file_open_fixed ( &efi_file_root, new );

        /* Fail unless opening from the root */
        if ( file != &efi_file_root ) {
                DBGC ( file, "EFIFILE %s is not a directory\n",
                       efi_file_name ( file ) );
                return EFI_NOT_FOUND;
        }

        /* Fail unless opening read-only */
        if ( mode != EFI_FILE_MODE_READ ) {
                DBGC ( file, "EFIFILE %s cannot be opened in mode %#08llx\n",
                       name, mode );
                return EFI_WRITE_PROTECTED;
        }

        /* Allow magic initrd to be opened */
        if ( strcasecmp ( name, efi_file_initrd.name ) == 0 )
                return efi_file_open_fixed ( &efi_file_initrd, new );

        /* Identify image */
        image = efi_file_find ( name );
        if ( ! image ) {
                DBGC ( file, "EFIFILE %s does not exist\n", name );
                return EFI_NOT_FOUND;
        }

        /* Allocate and initialise file */
        new_file = zalloc ( sizeof ( *new_file ) );
        if ( ! new_file )
                return EFI_OUT_OF_RESOURCES;
        ref_init ( &file->refcnt, efi_file_free );
        memcpy ( &new_file->file, &efi_file_root.file,
                 sizeof ( new_file->file ) );
        efi_file_image ( new_file, image_get ( image ) );
        *new = &new_file->file;
        DBGC ( new_file, "EFIFILE %s opened\n", efi_file_name ( new_file ) );

        return 0;
}

/**
 * Close file
 *
 * @v this              EFI file
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI efi_file_close ( EFI_FILE_PROTOCOL *this ) {
        struct efi_file *file = container_of ( this, struct efi_file, file );

        /* Close file */
        DBGC ( file, "EFIFILE %s closed\n", efi_file_name ( file ) );
        ref_put ( &file->refcnt );

        return 0;
}

/**
 * Close and delete file
 *
 * @v this              EFI file
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI efi_file_delete ( EFI_FILE_PROTOCOL *this ) {
        struct efi_file *file = container_of ( this, struct efi_file, file );

        DBGC ( file, "EFIFILE %s cannot be deleted\n", efi_file_name ( file ) );

        /* Close file */
        efi_file_close ( this );

        /* Warn of failure to delete */
        return EFI_WARN_DELETE_FAILURE;
}

/**
 * Return variable-length data structure
 *
 * @v base              Base data structure (starting with UINT64)
 * @v base_len          Length of base data structure
 * @v name              Name to append to base data structure
 * @v len               Length of data buffer
 * @v data              Data buffer
 * @ret efirc           EFI status code
 */
static EFI_STATUS efi_file_varlen ( UINT64 *base, size_t base_len,
                                    const char *name, UINTN *len, VOID *data ) {
        size_t name_len;

        /* Calculate structure length */
        name_len = strlen ( name );
        *base = ( base_len + ( name_len + 1 /* NUL */ ) * sizeof ( wchar_t ) );
        if ( *len < *base ) {
                *len = *base;
                return EFI_BUFFER_TOO_SMALL;
        }

        /* Copy data to buffer */
        *len = *base;
        memcpy ( data, base, base_len );
        efi_snprintf ( ( data + base_len ), ( name_len + 1 /* NUL */ ),
                       "%s", name );

        return 0;
}

/**
 * Return file information structure
 *
 * @v file              EFI file
 * @v len               Length of data buffer
 * @v data              Data buffer
 * @ret efirc           EFI status code
 */
static EFI_STATUS efi_file_info ( struct efi_file *file, UINTN *len,
                                  VOID *data ) {
        EFI_FILE_INFO info;
        size_t file_len;

        /* Get file length */
        file_len = efi_file_len ( file );

        /* Populate file information */
        memset ( &info, 0, sizeof ( info ) );
        info.FileSize = file_len;
        info.PhysicalSize = file_len;
        info.Attribute = EFI_FILE_READ_ONLY;
        if ( file == &efi_file_root )
                info.Attribute |= EFI_FILE_DIRECTORY;

        return efi_file_varlen ( &info.Size, SIZE_OF_EFI_FILE_INFO,
                                 file->name, len, data );
}

/**
 * Read directory entry
 *
 * @v file              EFI file
 * @v len               Length to read
 * @v data              Data buffer
 * @ret efirc           EFI status code
 */
static EFI_STATUS efi_file_read_dir ( struct efi_file *file, UINTN *len,
                                      VOID *data ) {
        EFI_STATUS efirc;
        struct efi_file entry;
        struct image *image;
        unsigned int index;

        /* Construct directory entries for image-backed files */
        index = file->pos;
        for_each_image ( image ) {
                if ( index-- == 0 ) {
                        efi_file_image ( &entry, image );
                        efirc = efi_file_info ( &entry, len, data );
                        if ( efirc == 0 )
                                file->pos++;
                        return efirc;
                }
        }

        /* No more entries */
        *len = 0;
        return 0;
}

/**
 * Read from file
 *
 * @v this              EFI file
 * @v len               Length to read
 * @v data              Data buffer
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI efi_file_read ( EFI_FILE_PROTOCOL *this,
                                         UINTN *len, VOID *data ) {
        struct efi_file *file = container_of ( this, struct efi_file, file );
        struct efi_file_reader reader;
        size_t pos = file->pos;

        /* If this is the root directory, then construct a directory entry */
        if ( ! file->read )
                return efi_file_read_dir ( file, len, data );

        /* Initialise reader */
        reader.file = file;
        reader.pos = 0;
        reader.data = data;
        reader.len = *len;

        /* Read from the file */
        DBGC ( file, "EFIFILE %s read [%#08zx,%#08zx)\n",
               efi_file_name ( file ), pos, file->pos );
        *len = file->read ( &reader );
        assert ( ( pos + *len ) == file->pos );

        return 0;
}

/**
 * Write to file
 *
 * @v this              EFI file
 * @v len               Length to write
 * @v data              Data buffer
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI efi_file_write ( EFI_FILE_PROTOCOL *this,
                                          UINTN *len, VOID *data __unused ) {
        struct efi_file *file = container_of ( this, struct efi_file, file );

        DBGC ( file, "EFIFILE %s cannot write [%#08zx, %#08zx)\n",
               efi_file_name ( file ), file->pos,
               ( ( size_t ) ( file->pos + *len ) ) );
        return EFI_WRITE_PROTECTED;
}

/**
 * Set file position
 *
 * @v this              EFI file
 * @v position          New file position
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI efi_file_set_position ( EFI_FILE_PROTOCOL *this,
                                                 UINT64 position ) {
        struct efi_file *file = container_of ( this, struct efi_file, file );
        size_t len;

        /* Get file length */
        len = efi_file_len ( file );

        /* Check for the magic end-of-file value */
        if ( position == 0xffffffffffffffffULL )
                position = len;

        /* Fail if we attempt to seek past the end of the file (since
         * we do not support writes).
         */
        if ( position > len ) {
                DBGC ( file, "EFIFILE %s cannot seek to %#08llx of %#08zx\n",
                       efi_file_name ( file ), position, len );
                return EFI_UNSUPPORTED;
        }

        /* Set position */
        file->pos = position;
        DBGC ( file, "EFIFILE %s position set to %#08zx\n",
               efi_file_name ( file ), file->pos );

        return 0;
}

/**
 * Get file position
 *
 * @v this              EFI file
 * @ret position        New file position
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI efi_file_get_position ( EFI_FILE_PROTOCOL *this,
                                                 UINT64 *position ) {
        struct efi_file *file = container_of ( this, struct efi_file, file );

        *position = file->pos;
        return 0;
}

/**
 * Get file information
 *
 * @v this              EFI file
 * @v type              Type of information
 * @v len               Buffer size
 * @v data              Buffer
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI efi_file_get_info ( EFI_FILE_PROTOCOL *this,
                                             EFI_GUID *type,
                                             UINTN *len, VOID *data ) {
        struct efi_file *file = container_of ( this, struct efi_file, file );
        EFI_FILE_SYSTEM_INFO fsinfo;
        struct image *image;

        /* Determine information to return */
        if ( memcmp ( type, &efi_file_info_id, sizeof ( *type ) ) == 0 ) {

                /* Get file information */
                DBGC ( file, "EFIFILE %s get file information\n",
                       efi_file_name ( file ) );
                return efi_file_info ( file, len, data );

        } else if ( memcmp ( type, &efi_file_system_info_id,
                             sizeof ( *type ) ) == 0 ) {

                /* Get file system information */
                DBGC ( file, "EFIFILE %s get file system information\n",
                       efi_file_name ( file ) );
                memset ( &fsinfo, 0, sizeof ( fsinfo ) );
                fsinfo.ReadOnly = 1;
                for_each_image ( image )
                        fsinfo.VolumeSize += image->len;
                return efi_file_varlen ( &fsinfo.Size,
                                         SIZE_OF_EFI_FILE_SYSTEM_INFO, "iPXE",
                                         len, data );
        } else {

                DBGC ( file, "EFIFILE %s cannot get information of type %s\n",
                       efi_file_name ( file ), efi_guid_ntoa ( type ) );
                return EFI_UNSUPPORTED;
        }
}

/**
 * Set file information
 *
 * @v this              EFI file
 * @v type              Type of information
 * @v len               Buffer size
 * @v data              Buffer
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_file_set_info ( EFI_FILE_PROTOCOL *this, EFI_GUID *type,
                    UINTN len __unused, VOID *data __unused ) {
        struct efi_file *file = container_of ( this, struct efi_file, file );

        DBGC ( file, "EFIFILE %s cannot set information of type %s\n",
               efi_file_name ( file ), efi_guid_ntoa ( type ) );
        return EFI_WRITE_PROTECTED;
}

/**
 * Flush file modified data
 *
 * @v this              EFI file
 * @v type              Type of information
 * @v len               Buffer size
 * @v data              Buffer
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI efi_file_flush ( EFI_FILE_PROTOCOL *this ) {
        struct efi_file *file = container_of ( this, struct efi_file, file );

        DBGC ( file, "EFIFILE %s flushed\n", efi_file_name ( file ) );
        return 0;
}

/** Root directory */
static struct efi_file efi_file_root = {
        .refcnt = REF_INIT ( ref_no_free ),
        .file = {
                .Revision = EFI_FILE_PROTOCOL_REVISION,
                .Open = efi_file_open,
                .Close = efi_file_close,
                .Delete = efi_file_delete,
                .Read = efi_file_read,
                .Write = efi_file_write,
                .GetPosition = efi_file_get_position,
                .SetPosition = efi_file_set_position,
                .GetInfo = efi_file_get_info,
                .SetInfo = efi_file_set_info,
                .Flush = efi_file_flush,
        },
        .image = NULL,
        .name = "",
};

/** Magic initrd file */
static struct efi_file efi_file_initrd = {
        .refcnt = REF_INIT ( ref_no_free ),
        .file = {
                .Revision = EFI_FILE_PROTOCOL_REVISION,
                .Open = efi_file_open,
                .Close = efi_file_close,
                .Delete = efi_file_delete,
                .Read = efi_file_read,
                .Write = efi_file_write,
                .GetPosition = efi_file_get_position,
                .SetPosition = efi_file_set_position,
                .GetInfo = efi_file_get_info,
                .SetInfo = efi_file_set_info,
                .Flush = efi_file_flush,
        },
        .image = NULL,
        .name = "initrd.magic",
        .read = efi_file_read_initrd,
};

/**
 * Open root directory
 *
 * @v filesystem        EFI simple file system
 * @ret file            EFI file handle
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_file_open_volume ( EFI_SIMPLE_FILE_SYSTEM_PROTOCOL *filesystem __unused,
                       EFI_FILE_PROTOCOL **file ) {

        DBGC ( &efi_file_root, "EFIFILE open volume\n" );
        return efi_file_open_fixed ( &efi_file_root, file );
}

/** EFI simple file system protocol */
static EFI_SIMPLE_FILE_SYSTEM_PROTOCOL efi_simple_file_system_protocol = {
        .Revision = EFI_SIMPLE_FILE_SYSTEM_PROTOCOL_REVISION,
        .OpenVolume = efi_file_open_volume,
};

/** Dummy block I/O reset */
static EFI_STATUS EFIAPI
efi_block_io_reset ( EFI_BLOCK_IO_PROTOCOL *this __unused, BOOLEAN extended ) {

        DBGC ( &efi_file_root, "EFIFILE block %sreset\n",
               ( extended ? "extended " : "" ) );
        return 0;
}

/** Dummy block I/O read */
static EFI_STATUS EFIAPI
efi_block_io_read_blocks ( EFI_BLOCK_IO_PROTOCOL *this __unused, UINT32 MediaId,
                           EFI_LBA lba, UINTN len, VOID *data ) {

        DBGC ( &efi_file_root, "EFIFILE block read ID %#08x LBA %#08llx -> "
               "%p+%zx\n", MediaId, ( ( unsigned long long ) lba ),
               data, ( ( size_t ) len ) );
        return EFI_NO_MEDIA;
}

/** Dummy block I/O write */
static EFI_STATUS EFIAPI
efi_block_io_write_blocks ( EFI_BLOCK_IO_PROTOCOL *this __unused,
                            UINT32 MediaId, EFI_LBA lba, UINTN len,
                            VOID *data ) {

        DBGC ( &efi_file_root, "EFIFILE block write ID %#08x LBA %#08llx <- "
               "%p+%zx\n", MediaId, ( ( unsigned long long ) lba ),
               data, ( ( size_t ) len ) );
        return EFI_NO_MEDIA;
}

/** Dummy block I/O flush */
static EFI_STATUS EFIAPI
efi_block_io_flush_blocks ( EFI_BLOCK_IO_PROTOCOL *this __unused ) {

        DBGC ( &efi_file_root, "EFIFILE block flush\n" );
        return 0;
}

/** Dummy block I/O media */
static EFI_BLOCK_IO_MEDIA efi_block_io_media = {
        .MediaId = EFI_MEDIA_ID_MAGIC,
        .MediaPresent = TRUE,
        .ReadOnly = TRUE,
        .BlockSize = 1,
};

/** Dummy EFI block I/O protocol */
static EFI_BLOCK_IO_PROTOCOL efi_block_io_protocol = {
        .Revision = EFI_BLOCK_IO_PROTOCOL_REVISION,
        .Media = &efi_block_io_media,
        .Reset = efi_block_io_reset,
        .ReadBlocks = efi_block_io_read_blocks,
        .WriteBlocks = efi_block_io_write_blocks,
        .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,
                        UINT64 offset, UINTN len, VOID *data ) {

        DBGC ( &efi_file_root, "EFIFILE disk read ID %#08x offset %#08llx -> "
               "%p+%zx\n", MediaId, ( ( unsigned long long ) offset ),
               data, ( ( size_t ) len ) );
        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,
                         UINT64 offset, UINTN len, VOID *data ) {

        DBGC ( &efi_file_root, "EFIFILE disk write ID %#08x offset %#08llx <- "
               "%p+%zx\n", MediaId, ( ( unsigned long long ) offset ),
               data, ( ( size_t ) len ) );
        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
 *
 * @v handle            EFI handle
 * @ret rc              Return status code
 */
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;

        /* Reset root directory state */
        efi_file_root.pos = 0;

        /* 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 "
                       "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 ) );
                DBGC_EFI_OPENERS ( handle, handle, &efi_disk_io_protocol_guid );
                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;
}

/**
 * Uninstall EFI simple file system protocol
 *
 * @v handle            EFI 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.
         */
        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 ) ) != 0 ) {
                rc = -EEFI ( efirc );
                DBGC ( handle, "Could not uninstall simple file system "
                       "protocols: %s\n", strerror ( rc ) );
                /* Oh dear */
        }
}