prime/tools/franklite.py

53 lines
1.7 KiB
Python

#! /usr/bin/env python3
# Written by Ethan Roseman (ethteck)
# MIT License
# Copyright 2021
# Modified by EpochFlame
import argparse
# Byte sequences
BLR_BYTE_SEQ = b"\x4E\x80\x00\x20"
MTLR_BYTE_SEQ = b"\x7C\x08\x03\xA6"
# Example invocation: ./frank.py vanilla.o profile.o output.o
parser = argparse.ArgumentParser()
parser.add_argument("vanilla", help="Path to the vanilla object", type=argparse.FileType('rb'))
parser.add_argument("target", help="Path to the target object (to write)")
args = parser.parse_args()
# Read contents into bytearrays and close files
vanilla_bytes = args.vanilla.read()
args.vanilla.close()
# Reunify mtlr/blr instructions, shifting intermediary instructions up
idx = 0
while idx < len(vanilla_bytes):
# Find mtlr position
mtlr_found_pos = vanilla_bytes.find(MTLR_BYTE_SEQ, idx)
if mtlr_found_pos == -1:
break # break while loop when no targets remain
if mtlr_found_pos % 4 != 0: # check 4-byte alignment
idx += 4
continue
# Find paired blr position
blr_found_pos = vanilla_bytes.find(BLR_BYTE_SEQ, mtlr_found_pos)
if blr_found_pos == -1:
break # break while loop when no targets remain
if blr_found_pos % 4 != 0: # check 4-byte alignment
idx += 4
continue
if mtlr_found_pos + 4 == blr_found_pos:
idx += 4
continue # continue if mtlr is followed directly by blr
vanilla_bytes = vanilla_bytes[:mtlr_found_pos] + vanilla_bytes[mtlr_found_pos+4:blr_found_pos] + vanilla_bytes[mtlr_found_pos:mtlr_found_pos+4] + vanilla_bytes[blr_found_pos:]
idx = mtlr_found_pos + len(MTLR_BYTE_SEQ)
with open(args.target, "wb") as f:
f.write(vanilla_bytes)