basic diff between two device tree blobs, attempts to account for differing phandles

dtb_diff.py

#!/usr/bin/env python

# Copyright (C) 2019 Simon Shields <simon@lineageos.org>
#
# 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 3 of the License, or
# (at your option) 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, see <http://www.gnu.org/licenses/>.
from pyfdt.pyfdt import *
import sys

if len(sys.argv) < 3:
    print("Need two files");
    sys.exit(1)

with open(sys.argv[1], 'rb') as f:
    blob1 = FdtBlobParse(f).to_fdt()
with open(sys.argv[2], 'rb') as f:
    blob2 = FdtBlobParse(f).to_fdt()


print_buf = []
orig_print = print
indent = 0
def my_print(*args, **kwargs):
    global print_buf
    for p in print_buf:
        orig_print(p, end='')
    print_buf = []
    orig_print(indent * '    ', end='')
    orig_print(*args, **kwargs)

print = my_print

class Node:
    def __init__(self, node):
        self.props = {}
        for i in range(len(node)):
            el = node[i]
            if type(el) == FdtNode:
                continue
            self.props[el.get_name()] = el

        if 'phandle' in self.props:
            self.phandle = self.props['phandle'].words[0]
        else:
            self.phandle = None

    def __getitem__(self, val):
        return self.props[val]



def blob_to_dict(blob):
    ret = {}
    phandles = {}

    for (path, node) in blob.resolve_path('/').walk():
        if type(node) != FdtNode:
            continue
        ret[path] = Node(node)

        if ret[path].phandle is not None:
            phandles[ret[path].phandle] = path

    return (ret, phandles)

def check_is_phandle_equiv(v1, v2):
    global phandles1, phandles2, max_ph1, max_ph2
    if v1 > max_ph1 or v2 > max_ph2:
        return False

    if v1 not in phandles1 or v2 not in phandles2:
        return False

    if phandles1[v1] == phandles2[v2]:
        return True

    return False

def diff_props(prop1, prop2):
    global indent
    if type(prop1) != type(prop2):
        return 'different type (<< %s / >> %s)'%(str(type(prop1)), str(type(prop2)))

    has_diffs = False
    if type(prop1) == FdtPropertyStrings:
        i = 0
        while i < len(prop1.strings) and i < len(prop2.strings):
            if prop1.strings[i] != prop2.strings[i]:
                has_diffs = True
                print('%d: << "%s", >> "%s"'%(i, prop1.strings[i], prop2.strings[i]))
            i += 1
        if i < len(prop1.strings):
            has_diffs = True
            print('%d extra elements for <<: "%s"'%(len(prop1.strings) - len(prop2.strings),
                    '", "'.join(prop1.strings[i:])))
        elif i < len(prop2.strings):
            has_diffs = True
            print('%d extra elements for >>: "%s"'%(len(prop2.strings) - len(prop1.strings),
                    '", "'.join(prop2.strings[i:])))
    elif type(prop1) == FdtPropertyBytes:
        i = 0
        while i < len(prop1.bytes) and i < len(prop2.bytes):
            if prop1.bytes[i] != prop2.bytes[i]:
                has_diffs = True
                print('%d: << %#x, >> %#x'%(i, prop1.bytes[i], prop2.bytes[i]))
            i += 1
        if i < len(prop1.bytes):
            has_diffs = True
            print('%d extra elements for <<: "%s"'%(len(prop1.bytes) - len(prop2.bytes),
                    '", "'.join(map(lambda a: hex(ord(a)), prop1.bytes[i:]))))
        elif i < len(prop2.bytes):
            has_diffs = True
            print('%d extra elements for >>: "%s"'%(len(prop2.bytes) - len(prop1.bytes),
                    '", "'.join(map(lambda a: hex(ord(a)), prop2.bytes[i:]))))
    elif type(prop1) == FdtPropertyWords:
        i = 0
        while i < len(prop1.words) and i < len(prop2.words):
            if prop1.words[i] != prop2.words[i] and not \
                    check_is_phandle_equiv(prop1.words[i], prop2.words[i]):
                has_diffs = True
                print('%d: << %#x, >> %#x'%(i, prop1.words[i], prop2.words[i]))
            i += 1

        if i < len(prop1.words):
            has_diffs = True
            print('%d extra elements for <<: "%s"'%(len(prop1.words) - len(prop2.words),
                    '", "'.join(map(lambda a: hex(a), prop1.words[i:]))))
        elif i < len(prop2.words):
            has_diffs = True
            print('%d extra elements for >>: "%s"'%(len(prop2.words) - len(prop1.words),
                    '", "'.join(map(lambda a: hex(a), prop2.words[i:]))))



    if has_diffs:
        return

    return True

def diff_nodes(node1, node2):
    global indent, print_buf
    props = set(node1.props.keys())
    props.union(set(node2.props.keys()))
    for p in sorted(props):
        if p in node1.props and p in node2.props:
            print_buf.append((indent * '    ') + p + ':\n')
            indent += 1
            diff_props(node1.props[p], node2.props[p])
            indent -= 1
            if len(print_buf) > 0:
                print_buf.pop()
        elif p in node1.props:
            print(p + ': only <<')
        else:
            print(p + ': only >>')

def diff_tree(tree1, tree2):
    global indent, print_buf
    paths  = set(tree1.keys())
    paths.union(set(tree2.keys()))

    for p in sorted(paths):
        indent = p.count('/') - 1
        if p in tree1 and p in tree2:
            print_buf.append((indent * '    ') + p + ':\n')
            indent += 1
            diff_nodes(tree1[p], tree2[p])
            indent -= 1
            if len(print_buf) > 0:
                print_buf.pop()
        elif p in tree1:
            print(p, 'only in <<')
        else:
            print(p, 'only in >>')

(nodes1, phandles1) = blob_to_dict(blob1)
(nodes2, phandles2) = blob_to_dict(blob2)

max_ph1 = max(phandles1.keys())
max_ph2 = max(phandles2.keys())

diff_tree(nodes1, nodes2)