#!/usr/bin/python

import os, re, getopt, sys
from stat import ST_SIZE
from subprocess import PIPE, Popen

verbose = 0


# return address of 4K page following the spefified address
def round_page(addr):
	page_size = 0x1000
	return (addr + page_size) & ~(page_size - 1)


def first_free_addr_after_program(elf, cross_prefix = ""):
	try:
		objdump = cross_prefix + "objdump"
		objdump_output = Popen([objdump, "-p", elf],
		                       stdout=PIPE).communicate()[0]
	except OSError:
		print "Error: execution of " + objdump + " failed, invalid cross-tool prefix?"
		exit(3)

	#
	# The output of 'objdump -p' contains the list of program segments. Each
	# segment has two lines of text, the first containing the 'vaddr' value and
	# the latter containing the 'memsz' value. For each line, we match for both
	# 'vaddr' and 'memsz' fields. When observing a line with a 'memsz' field,
	# we know that the previous line contained the corresponding 'vaddr' and
	# that the end address of the segment is the sum of the current 'vaddr'
	# and 'memsz' values.
	#
	max_end_addr = 0
	for line in objdump_output.splitlines():
		match_vaddr = re.compile(".*vaddr (0x[0-9a-f]*).*").match(line)
		match_memsz = re.compile(".*memsz (0x[0-9a-f]*).*").match(line)
		if (match_vaddr):
			vaddr = int(match_vaddr.group(1), 0)
		if (match_memsz):
			memsz = int(match_memsz.group(1), 0)
			max_end_addr = max(max_end_addr, vaddr + memsz)

	# align the first free address at the next page boundary
	return round_page(max_end_addr)


def generate_modules_asm(modules):
	"""
	Generate assembly code aggregating boot-module data from specified files.
	The generated assembly code looks as follows:

	/*
	 * The ELF image consists only of a data section. At file offset 0, there
	 * is a magic cookie that core validates when accessing the ROM fs. It is
	 * followed by the end address of the meta data.
	 */
	.section .data
	.string "GROM"     /* magic cookie used by core to identify a ROM fs image*/
	.long header_end   /* end of ROM fs meta data */

	/*
	 * Each module is represented by a struct of 3 long values. The first
	 * value is pointer to the module name. A null-pointer marks the end of
	 * the module list.
	 */
	.long mod1_name             /* pointer to the null-terminated module name */
	.long mod1_start            /* pointer to the module data */
	.long mod1_end - mod1_start /* size of the module data */

	.long 0

	/*
	 * For each module, there exists a null-terminated string labeled with
	 * 'mod<index>_name' referenced by the module list above.
	 */
	mod1_name:
	.string "name of data module"
	.byte 0

	header_end:

	/*
	 * The data of each module must be aligned at a page boundary to enable
	 * the mapping of individual modules to different address spaces.
	 */
	.align 4096
	mod1_start: .incbin "data"
	mod1_end:
	"""

	asm_src = ""

	# header
	asm_src += ".section .data\nmodule_list:\n"
	asm_src += ".ascii \"GROM\"\n"
	asm_src += ".long header_end\n"

	# module list
	i = 1
	for module in modules:
		asm_src += ".long mod" + str(i) + "_name\n"
		asm_src += ".long mod" + str(i) + "_start\n"
		asm_src += ".long mod" + str(i) + "_end - mod" + str(i) + "_start\n"
		i = i + 1
	asm_src += ".long 0\n"

	# module names
	i = 1
	for module in modules:
		asm_src += "mod" + str(i) + "_name: .string \"" + os.path.split(module)[1] + "\"; .byte 0\n"
		i = i + 1

	asm_src += "header_end:\n"

	# module data
	i = 1
	for module in modules:
		asm_src += ".p2align 12,0\n"
		asm_src += "mod" + str(i) + "_start: .incbin \"" + module + "\"; "
		asm_src += "mod" + str(i) + "_end:\n"
		i = i + 1

	return asm_src

instructions = """
usage: gen_romfs [-v] [-p <cross-prefix>] -c <core-elf> -o <output> [modules ...]

Generates Genode ROM file system as ELF file loadable into a Codezero container

  -c|--core     ELF binary of Genode's core
  -o|--output   name of ELF image to generate
  -p|--prefix   cross toolchain prefix
  -v|--verbose  print details about generated ROM file systemn
"""

def usage():
	print instructions

def user_error(message):
	print "Error: " + message
	usage
	sys.exit(2)

# default values for command-line arguments
cross_prefix = ""
core_elf     = ""
dst_elf      = ""

# parse command line arguments
try:
	opts, modules = getopt.getopt(sys.argv[1:],
	                              "c:o:p:v",
	                              ["core=", "output=", "prefix=", "verbose"])
except getopt.GetoptError:
	usage()
	sys.exit(2)
for opt, arg in opts:
	if opt in ("-c", "--core"):
		core_elf = arg
	elif opt in ("-o", "--output"):
		dst_elf = arg
	elif opt in ("-p", "--prefix"):
		cross_prefix = arg
	elif opt in ("-v", "--verbose"):
		verbose = 1
	else:
		user_error("invalid argument \"" + arg + "\"")

# validate arguments
if (core_elf     == ""): user_error("no core binary specified")
if (len(modules) ==  0): user_error("no modules specified")
if (dst_elf      == ""): user_error("no output file spefied")

# determine destination address of the modules ELF image
modules_start_addr = first_free_addr_after_program(core_elf, cross_prefix)

if (verbose):
	print "module address: " + hex(modules_start_addr)

# generate assembly code aggregating the module data
asm_src = generate_modules_asm(modules)

if (verbose):
	print "generated assember code:"
	for line in asm_src.splitlines():
		print "  " + line

# invoke assembler and linker through the gcc front end
gcc_cmd = [cross_prefix + "gcc",
           "-nostdlib",
           "-x", "assembler",
           "-Wl,--entry=0",
           "-Wl,--section-start=.data="   + hex(modules_start_addr),
           "-o", dst_elf,
           "-"]

if (verbose):
	print "gcc command line:"
	print "  " + ' '.join(gcc_cmd)

Popen(gcc_cmd, stdin=PIPE).communicate(asm_src)[0]