binman: Add support for flashrom FMAP

Add an entry which can hold an FMAP region as used by flashrom, an
open-source flashing tool used on Linux x86 machines. This provides a
simplified non-hierarchical view of the entries in the image and has a
signature at the start to allow flashrom to find it in the image.

Signed-off-by: Simon Glass <sjg@chromium.org>

1 files changed, 109 insertions, 0 deletions

diff --git a/tools/binman/fmap_util.py b/tools/binman/fmap_util.py
new file mode 100644
index 0000000000..7d520e3391
--- /dev/null
+++ b/tools/binman/fmap_util.py
@@ -0,0 +1,109 @@
+# SPDX-License-Identifier: GPL-2.0+
+# Copyright (c) 2018 Google, Inc
+# Written by Simon Glass <sjg@chromium.org>
+#
+# Support for flashrom's FMAP format. This supports a header followed by a
+# number of 'areas', describing regions of a firmware storage device,
+# generally SPI flash.
+
+import collections
+import struct
+
+# constants imported from lib/fmap.h
+FMAP_SIGNATURE = '__FMAP__'
+FMAP_VER_MAJOR = 1
+FMAP_VER_MINOR = 0
+FMAP_STRLEN = 32
+
+FMAP_AREA_STATIC = 1 << 0
+FMAP_AREA_COMPRESSED = 1 << 1
+FMAP_AREA_RO = 1 << 2
+
+FMAP_HEADER_LEN = 56
+FMAP_AREA_LEN = 42
+
+FMAP_HEADER_FORMAT = '<8sBBQI%dsH'% (FMAP_STRLEN)
+FMAP_AREA_FORMAT = '<II%dsH' % (FMAP_STRLEN)
+
+FMAP_HEADER_NAMES = (
+    'signature',
+    'ver_major',
+    'ver_minor',
+    'base',
+    'image_size',
+    'name',
+    'nareas',
+)
+
+FMAP_AREA_NAMES = (
+    'offset',
+    'size',
+    'name',
+    'flags',
+)
+
+# These are the two data structures supported by flashrom, a header (which
+# appears once at the start) and an area (which is repeated until the end of
+# the list of areas)
+FmapHeader = collections.namedtuple('FmapHeader', FMAP_HEADER_NAMES)
+FmapArea = collections.namedtuple('FmapArea', FMAP_AREA_NAMES)
+
+
+def ConvertName(field_names, fields):
+    """Convert a name to something flashrom likes
+
+    Flashrom requires upper case, underscores instead of hyphens. We remove any
+    null characters as well. This updates the 'name' value in fields.
+
+    Args:
+        field_names: List of field names for this struct
+        fields: Dict:
+            key: Field name
+            value: value of that field (string for the ones we support)
+    """
+    name_index = field_names.index('name')
+    fields[name_index] = fields[name_index].replace('\0', '').replace('-', '_').upper()
+
+def DecodeFmap(data):
+    """Decode a flashmap into a header and list of areas
+
+    Args:
+        data: Data block containing the FMAP
+
+    Returns:
+        Tuple:
+            header: FmapHeader object
+            List of FmapArea objects
+    """
+    fields = list(struct.unpack(FMAP_HEADER_FORMAT, data[:FMAP_HEADER_LEN]))
+    ConvertName(FMAP_HEADER_NAMES, fields)
+    header = FmapHeader(*fields)
+    areas = []
+    data = data[FMAP_HEADER_LEN:]
+    for area in range(header.nareas):
+        fields = list(struct.unpack(FMAP_AREA_FORMAT, data[:FMAP_AREA_LEN]))
+        ConvertName(FMAP_AREA_NAMES, fields)
+        areas.append(FmapArea(*fields))
+        data = data[FMAP_AREA_LEN:]
+    return header, areas
+
+def EncodeFmap(image_size, name, areas):
+    """Create a new FMAP from a list of areas
+
+    Args:
+        image_size: Size of image, to put in the header
+        name: Name of image, to put in the header
+        areas: List of FmapArea objects
+
+    Returns:
+        String containing the FMAP created
+    """
+    def _FormatBlob(fmt, names, obj):
+        params = [getattr(obj, name) for name in names]
+        return struct.pack(fmt, *params)
+
+    values = FmapHeader(FMAP_SIGNATURE, 1, 0, 0, image_size, name, len(areas))
+    blob = _FormatBlob(FMAP_HEADER_FORMAT, FMAP_HEADER_NAMES, values)
+    for area in areas:
+        blob += _FormatBlob(FMAP_AREA_FORMAT, FMAP_AREA_NAMES, area)
+    return blob