[efi] Allow for non-image-backed virtual files

Restructure the EFI_SIMPLE_FILE_SYSTEM_PROTOCOL implementation to
allow for the existence of virtual files that are not simply backed by
a single underlying image.

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

1 files changed, 221 insertions, 69 deletions

diff --git a/src/interface/efi/efi_file.c b/src/interface/efi/efi_file.c
index 52de098..c67fdea 100644
--- a/src/interface/efi/efi_file.c
+++ b/src/interface/efi/efi_file.c
@@ -50,19 +50,55 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 /** EFI media ID */
 #define EFI_MEDIA_ID_MAGIC 0x69505845
 
-/** An image exposed as an EFI file */
+/** 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 */
+	/** 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;
 
 /**
+ * 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
@@ -70,28 +106,140 @@ static struct efi_file efi_file_root;
  */
 static const char * efi_file_name ( struct efi_file *file ) {
 
-	return ( file->image ? file->image->name : "<root>" );
+	return ( file == &efi_file_root ? "<root>" : file->name );
 }
 
 /**
  * Find EFI file image
  *
- * @v wname		Filename
+ * @v name		Filename
  * @ret image		Image, or NULL
  */
-static struct image * efi_file_find ( const CHAR16 *wname ) {
-	char name[ wcslen ( wname ) + 1 /* NUL */ ];
+static struct image * efi_file_find ( const char *name ) {
 	struct image *image;
 
 	/* Find image */
-	snprintf ( name, sizeof ( name ), "%ls", wname );
 	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 );
+}
+
+/**
+ * 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;
 }
 
 /**
@@ -106,50 +254,56 @@ static struct image * efi_file_find ( const CHAR16 *wname ) {
  */
 static EFI_STATUS EFIAPI
 efi_file_open ( EFI_FILE_PROTOCOL *this, EFI_FILE_PROTOCOL **new,
-		CHAR16 *wname, UINT64 mode __unused,
-		UINT64 attributes __unused ) {
+		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 ( *wname == L'\\' ) {
+	while ( *name == '\\' ) {
 		file = &efi_file_root;
-		wname++;
+		name++;
 	}
 
 	/* Allow root directory itself to be opened */
-	if ( ( wname[0] == L'\0' ) || ( wname[0] == L'.' ) ) {
-		*new = &efi_file_root.file;
-		return 0;
-	}
+	if ( ( name[0] == '\0' ) || ( name[0] == '.' ) )
+		return efi_file_open_fixed ( &efi_file_root, new );
 
 	/* Fail unless opening from the root */
-	if ( file->image ) {
+	if ( file != &efi_file_root ) {
 		DBGC ( file, "EFIFILE %s is not a directory\n",
 		       efi_file_name ( file ) );
 		return EFI_NOT_FOUND;
 	}
 
-	/* Identify image */
-	image = efi_file_find ( wname );
-	if ( ! image ) {
-		DBGC ( file, "EFIFILE \"%ls\" does not exist\n", wname );
-		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",
-		       image->name, mode );
+		       name, mode );
 		return EFI_WRITE_PROTECTED;
 	}
 
+	/* 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 ) );
-	new_file->image = image_get ( image );
+	efi_file_image ( new_file, image_get ( image ) );
 	*new = &new_file->file;
 	DBGC ( new_file, "EFIFILE %s opened\n", efi_file_name ( new_file ) );
 
@@ -165,14 +319,9 @@ efi_file_open ( EFI_FILE_PROTOCOL *this, EFI_FILE_PROTOCOL **new,
 static EFI_STATUS EFIAPI efi_file_close ( EFI_FILE_PROTOCOL *this ) {
 	struct efi_file *file = container_of ( this, struct efi_file, file );
 
-	/* Do nothing if this is the root */
-	if ( ! file->image )
-		return 0;
-
 	/* Close file */
 	DBGC ( file, "EFIFILE %s closed\n", efi_file_name ( file ) );
-	image_put ( file->image );
-	free ( file );
+	ref_put ( &file->refcnt );
 
 	return 0;
 }
@@ -229,30 +378,29 @@ static EFI_STATUS efi_file_varlen ( UINT64 *base, size_t base_len,
 /**
  * Return file information structure
  *
- * @v image		Image, or NULL for the root directory
+ * @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 image *image, UINTN *len,
+static EFI_STATUS efi_file_info ( struct efi_file *file, UINTN *len,
 				  VOID *data ) {
 	EFI_FILE_INFO info;
-	const char *name;
+	size_t file_len;
+
+	/* Get file length */
+	file_len = efi_file_len ( file );
 
 	/* Populate file information */
 	memset ( &info, 0, sizeof ( info ) );
-	if ( image ) {
-		info.FileSize = image->len;
-		info.PhysicalSize = image->len;
-		info.Attribute = EFI_FILE_READ_ONLY;
-		name = image->name;
-	} else {
-		info.Attribute = ( EFI_FILE_READ_ONLY | EFI_FILE_DIRECTORY );
-		name = "";
-	}
-
-	return efi_file_varlen ( &info.Size, SIZE_OF_EFI_FILE_INFO, name,
-				 len, data );
+	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 );
 }
 
 /**
@@ -266,14 +414,16 @@ static EFI_STATUS efi_file_info ( struct image *image, UINTN *len,
 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 entry at current position */
+	/* Construct directory entries for image-backed files */
 	index = file->pos;
 	for_each_image ( image ) {
 		if ( index-- == 0 ) {
-			efirc = efi_file_info ( image, len, data );
+			efi_file_image ( &entry, image );
+			efirc = efi_file_info ( &entry, len, data );
 			if ( efirc == 0 )
 				file->pos++;
 			return efirc;
@@ -296,21 +446,25 @@ static EFI_STATUS efi_file_read_dir ( struct efi_file *file, UINTN *len,
 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 );
-	size_t remaining;
+	struct efi_file_reader reader;
+	size_t pos = file->pos;
 
 	/* If this is the root directory, then construct a directory entry */
-	if ( ! file->image )
+	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 */
-	remaining = ( file->image->len - file->pos );
-	if ( *len > remaining )
-		*len = remaining;
 	DBGC ( file, "EFIFILE %s read [%#08zx,%#08zx)\n",
-	       efi_file_name ( file ), file->pos,
-	       ( ( size_t ) ( file->pos + *len ) ) );
-	copy_from_user ( data, file->image->data, file->pos, *len );
-	file->pos += *len;
+	       efi_file_name ( file ), pos, file->pos );
+	*len = file->read ( &reader );
+	assert ( ( pos + *len ) == file->pos );
+
 	return 0;
 }
 
@@ -342,24 +496,21 @@ static EFI_STATUS EFIAPI efi_file_write ( EFI_FILE_PROTOCOL *this,
 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;
 
-	/* If this is the root directory, reset to the start */
-	if ( ! file->image ) {
-		DBGC ( file, "EFIFILE root directory rewound\n" );
-		file->pos = 0;
-		return 0;
-	}
+	/* Get file length */
+	len = efi_file_len ( file );
 
 	/* Check for the magic end-of-file value */
 	if ( position == 0xffffffffffffffffULL )
-		position = file->image->len;
+		position = len;
 
 	/* Fail if we attempt to seek past the end of the file (since
 	 * we do not support writes).
 	 */
-	if ( position > file->image->len ) {
+	if ( position > len ) {
 		DBGC ( file, "EFIFILE %s cannot seek to %#08llx of %#08zx\n",
-		       efi_file_name ( file ), position, file->image->len );
+		       efi_file_name ( file ), position, len );
 		return EFI_UNSUPPORTED;
 	}
 
@@ -408,7 +559,7 @@ static EFI_STATUS EFIAPI efi_file_get_info ( EFI_FILE_PROTOCOL *this,
 		/* Get file information */
 		DBGC ( file, "EFIFILE %s get file information\n",
 		       efi_file_name ( file ) );
-		return efi_file_info ( file->image, len, data );
+		return efi_file_info ( file, len, data );
 
 	} else if ( memcmp ( type, &efi_file_system_info_id,
 			     sizeof ( *type ) ) == 0 ) {
@@ -468,6 +619,7 @@ static EFI_STATUS EFIAPI efi_file_flush ( EFI_FILE_PROTOCOL *this ) {
 
 /** 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,
@@ -482,6 +634,7 @@ static struct efi_file efi_file_root = {
 		.Flush = efi_file_flush,
 	},
 	.image = NULL,
+	.name = "",
 };
 
 /**
@@ -496,8 +649,7 @@ efi_file_open_volume ( EFI_SIMPLE_FILE_SYSTEM_PROTOCOL *filesystem __unused,
 		       EFI_FILE_PROTOCOL **file ) {
 
 	DBGC ( &efi_file_root, "EFIFILE open volume\n" );
-	*file = &efi_file_root.file;
-	return 0;
+	return efi_file_open_fixed ( &efi_file_root, file );
 }
 
 /** EFI simple file system protocol */