#! /usr/bin/env python
"""
===========================================================================

  Copyright (c) 2012 Qualcomm Technologies, Inc.  All Rights Reserved.
  Qualcomm Technologies Proprietary and Confidential.

===========================================================================
"""

"""
Splits elf files into segments.

If the elf is signed, the elf headers and the hash segment are output to
the *.mdt file, and then the segments are output to *.b<n> files.

If the elf isn't signed each segment is output to a *.b<n> file and the
elf headers are output to the *.mdt file.
"""

import sys
import struct

def die(message):
	print message
	exit(1)

def usage():
	print "Usage: %s <elf> <prefix>" % sys.argv[0]
	exit(1)

def dump_data(input, output, start, size):
	"""Dump 'size' bytes from 'input' at 'start' into newfile 'output'"""

	if size == 0:
		return

	input.seek(start)
	outFile = open(output, 'wb')
	outFile.write(input.read(size))
	outFile.close()

	print 'BIN %s' % output

def append_data(input, output, start, size):
	"""Append 'size' bytes from 'input' at 'start' to 'output' file"""

	if size == 0:
		return

	input.seek(start)
	outFile = open(output, 'ab')
	outFile.write(input.read(size))
	outFile.close()

def gen_struct(format, image):
	"""Generates a dictionary from the format tuple by reading image"""

	str = "<%s" % "".join([x[1] for x in format])
	elems = struct.unpack(str, image.read(struct.calcsize(str)))
	keys = [x[0] for x in format]
	return dict(zip(keys, elems))

def parse_metadata(image):
	"""Parses elf header metadata"""
	metadata = {}

	elf32_hdr = [
			("ident", "16s"),
			("type", "H"),
			("machine", "H"),
			("version", "I"),
			("entry", "I"),
			("phoff", "I"),
			("shoff", "I"),
			("flags", "I"),
			("ehsize", "H"),
			("phentsize", "H"),
			("phnum", "H"),
			("shentsize", "H"),
			("shnum", "H"),
			("shstrndx", "H"),
			]
	elf32_hdr = gen_struct(elf32_hdr, image)
	metadata['num_segments'] = elf32_hdr['phnum']
	metadata['pg_start'] = elf32_hdr['phoff']

	elf32_phdr = [
			("type", "I"),
			("offset", "I"),
			("vaddr", "I"),
			("paddr", "I"),
			("filesz", "I"),
			("memsz", "I"),
			("flags", "I"),
			("align", "I"),
			]

	metadata['segments'] = []
	for i in xrange(metadata['num_segments']):
		image.seek(metadata['pg_start'] + (i * elf32_hdr['phentsize']))
		phdr = gen_struct(elf32_phdr, image)
		metadata['segments'].append(phdr)
		phdr['hash'] = (phdr['flags'] & (0x7 << 24)) == (0x2 << 24)

	return metadata

def dump_metadata(metadata, image, name):
	"""Creates <name>.mdt file from elf metadata"""

	name = "%s.mdt" % name
	# Dump out the elf header
	dump_data(image, name, 0, 52)
	# Append the program headers
	append_data(image, name, metadata['pg_start'], 32 * metadata['num_segments'])

	for seg in metadata['segments']:
		if seg['hash']:
			append_data(image, name, seg['offset'], seg['filesz'])
			break

def dump_segments(metadata, image, name):
	"""Creates <name>.bXX files for each segment"""
	for i, seg in enumerate(metadata['segments']):
		start = seg['offset']
		size = seg['filesz']
		output = "%s.b%02d" % (name, i)
		dump_data(image, output, start, size)

def is_elf(file):
	"""Verifies a file as being an ELF file"""
	file.seek(0)
	magic = file.read(4)
	image.seek(0)
	return magic == '\x7fELF'

if __name__ == "__main__":

	if len(sys.argv) != 3:
		usage()

	image = open(sys.argv[1], 'rb')
	if not is_elf(image):
		usage()

	prefix = sys.argv[2]
	metadata = parse_metadata(image)
	dump_metadata(metadata, image, prefix)
	dump_segments(metadata, image, prefix)