120 lines
3.4 KiB
Python
120 lines
3.4 KiB
Python
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# SPDX-License-Identifier: GPL-2.0+
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# Copyright (c) 2018 Google, Inc
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# Written by Simon Glass <sjg@chromium.org>
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#
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# Support for flashrom's FMAP format. This supports a header followed by a
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# number of 'areas', describing regions of a firmware storage device,
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# generally SPI flash.
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import collections
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import struct
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import sys
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import tools
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# constants imported from lib/fmap.h
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FMAP_SIGNATURE = b'__FMAP__'
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FMAP_VER_MAJOR = 1
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FMAP_VER_MINOR = 0
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FMAP_STRLEN = 32
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FMAP_AREA_STATIC = 1 << 0
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FMAP_AREA_COMPRESSED = 1 << 1
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FMAP_AREA_RO = 1 << 2
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FMAP_HEADER_LEN = 56
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FMAP_AREA_LEN = 42
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FMAP_HEADER_FORMAT = '<8sBBQI%dsH'% (FMAP_STRLEN)
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FMAP_AREA_FORMAT = '<II%dsH' % (FMAP_STRLEN)
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FMAP_HEADER_NAMES = (
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'signature',
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'ver_major',
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'ver_minor',
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'base',
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'image_size',
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'name',
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'nareas',
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)
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FMAP_AREA_NAMES = (
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'offset',
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'size',
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'name',
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'flags',
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)
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# These are the two data structures supported by flashrom, a header (which
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# appears once at the start) and an area (which is repeated until the end of
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# the list of areas)
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FmapHeader = collections.namedtuple('FmapHeader', FMAP_HEADER_NAMES)
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FmapArea = collections.namedtuple('FmapArea', FMAP_AREA_NAMES)
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def NameToFmap(name):
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if type(name) == bytes and sys.version_info[0] >= 3:
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name = name.decode('utf-8') # pragma: no cover (for Python 2)
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return name.replace('\0', '').replace('-', '_').upper()
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def ConvertName(field_names, fields):
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"""Convert a name to something flashrom likes
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Flashrom requires upper case, underscores instead of hyphens. We remove any
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null characters as well. This updates the 'name' value in fields.
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Args:
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field_names: List of field names for this struct
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fields: Dict:
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key: Field name
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value: value of that field (string for the ones we support)
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"""
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name_index = field_names.index('name')
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fields[name_index] = tools.ToBytes(NameToFmap(fields[name_index]))
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def DecodeFmap(data):
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"""Decode a flashmap into a header and list of areas
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Args:
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data: Data block containing the FMAP
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Returns:
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Tuple:
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header: FmapHeader object
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List of FmapArea objects
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"""
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fields = list(struct.unpack(FMAP_HEADER_FORMAT, data[:FMAP_HEADER_LEN]))
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ConvertName(FMAP_HEADER_NAMES, fields)
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header = FmapHeader(*fields)
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areas = []
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data = data[FMAP_HEADER_LEN:]
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for area in range(header.nareas):
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fields = list(struct.unpack(FMAP_AREA_FORMAT, data[:FMAP_AREA_LEN]))
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ConvertName(FMAP_AREA_NAMES, fields)
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areas.append(FmapArea(*fields))
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data = data[FMAP_AREA_LEN:]
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return header, areas
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def EncodeFmap(image_size, name, areas):
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"""Create a new FMAP from a list of areas
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Args:
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image_size: Size of image, to put in the header
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name: Name of image, to put in the header
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areas: List of FmapArea objects
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Returns:
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String containing the FMAP created
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"""
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def _FormatBlob(fmt, names, obj):
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params = [getattr(obj, name) for name in names]
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ConvertName(names, params)
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return struct.pack(fmt, *params)
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values = FmapHeader(FMAP_SIGNATURE, 1, 0, 0, image_size,
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tools.FromUnicode(name), len(areas))
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blob = _FormatBlob(FMAP_HEADER_FORMAT, FMAP_HEADER_NAMES, values)
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for area in areas:
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blob += _FormatBlob(FMAP_AREA_FORMAT, FMAP_AREA_NAMES, area)
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return blob
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