tools/binman/etype/intel_descriptor.py

# SPDX-License-Identifier: GPL-2.0+
# Copyright (c) 2016 Google, Inc
# Written by Simon Glass <sjg@chromium.org>
#
# Entry-type module for 'u-boot'
#

import struct

from entry import Entry
from blob import Entry_blob

FD_SIGNATURE   = struct.pack('<L', 0x0ff0a55a)
MAX_REGIONS    = 5

# Region numbers supported by the Intel firmware format
(REGION_DESCRIPTOR, REGION_BIOS, REGION_ME, REGION_GBE,
        REGION_PDATA) = range(5)

class Region:
    def __init__(self, data, frba, region_num):
        pos = frba + region_num * 4
        val = struct.unpack('<L', data[pos:pos + 4])[0]
        self.base = (val & 0xfff) << 12
        self.limit = ((val & 0x0fff0000) >> 4) | 0xfff
        self.size = self.limit - self.base + 1

class Entry_intel_descriptor(Entry_blob):
    """Intel flash descriptor block (4KB)

    Properties / Entry arguments:
        filename: Filename of file containing the descriptor. This is typically
            a 4KB binary file, sometimes called 'descriptor.bin'

    This entry is placed at the start of flash and provides information about
    the SPI flash regions. In particular it provides the base address and
    size of the ME (Management Engine) region, allowing us to place the ME
    binary in the right place.

    With this entry in your image, the position of the 'intel-me' entry will be
    fixed in the image, which avoids you needed to specify an offset for that
    region. This is useful, because it is not possible to change the position
    of the ME region without updating the descriptor.

    See README.x86 for information about x86 binary blobs.
    """
    def __init__(self, section, etype, node):
        Entry_blob.__init__(self, section, etype, node)
        self._regions = []

    def GetOffsets(self):
        offset = self.data.find(FD_SIGNATURE)
        if offset == -1:
            self.Raise('Cannot find FD signature')
        flvalsig, flmap0, flmap1, flmap2 = struct.unpack('<LLLL',
                                                self.data[offset:offset + 16])
        frba = ((flmap0 >> 16) & 0xff) << 4
        for i in range(MAX_REGIONS):
            self._regions.append(Region(self.data, frba, i))

        # Set the offset for ME only, for now, since the others are not used
        return {'intel-me': [self._regions[REGION_ME].base,
                             self._regions[REGION_ME].size]}