#!/usr/bin/env python
#
# Copyright (c) 2008, Bjoern B. Brandenburg <bbb [at] cs.unc.edu>
#
# All rights reserved.
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"""
Purpose: This tool displays the assembly code of all symbols matching a given
         pattern in a given set of files. It is a quick&dirty wrapper around
         the nm(1) and objdump(1) tools. Its main advantage is that it does not
         require you to find out the addresses of a given set of symbols
         manually. Also, it's considerably faster than just disassembling the
         whole Linux kernel on slow systems.

Example: show_asm printk vmlinux
         Disassemble printk-related functions in the Linux kernel.

         show_asm 'main|foo|bar' *.o
         Disassemble all main, foo, and bar
         functions in all object files in the current directory.
"""

from subprocess import Popen, PIPE, call
import re
import sys
import os

NM_FORMAT = "([0-9a-f]+) *([0-9a-f]*) *([AaBbCcDdGgIiNnRrSsTtUuVvWw])" + \
    " ([_a-zA-Z.0-9]+)"

nm_re = re.compile(NM_FORMAT)

def parse_nm_output(str):
    "returns (start, length, type, name)"
    m = nm_re.match(str)
    if m:
        start  = int(m.group(1), 16)
        if m.group(2) != '':
            length = int(m.group(2), 16)
        else:
            length = 0
        return (start, length, m.group(3), m.group(4))
    else:
        return None

def symbol_is_text(addr):
    return addr[2] in "tT"

def nm(file):
    cmd = "nm -S %s" % file
    p = Popen(cmd, shell=True, stdout=PIPE)
    return p.stdout

def nm_filtered(file, symbol):
    cmd = "nm -S %s | egrep '%s' " % (file, symbol)
    p = Popen(cmd, shell=True, stdout=PIPE)
    return p.stdout

def objdump_symbol(file, addr):
    objdump_cmd = "objdump -S -d --start-address=0x%x --stop-address=0x%x %s" \
        % (addr[0], addr[0] + addr[1], file)
    filter_cmd  = "egrep -v 'Disassembly of|file format|^$'"
    pipe_cmd    = "%s | %s" % (objdump_cmd, filter_cmd)
    print "=====[ %s:%s (0x%x - 0x%x, type: %s) ]=====" % \
        (file, addr[3], addr[0], addr[0] + addr[1], addr[2])
    sys.stdout.flush()
    call(pipe_cmd, shell=True)


def get_address_ranges(file, symbol):
    for line in nm_filtered(file, symbol):
        addr = parse_nm_output(line)
        if addr and addr[1] > 0 and symbol_is_text(addr):
            objdump_symbol(file, addr)

if __name__ == "__main__":
    if len(sys.argv) < 3:
        name = os.path.basename(sys.argv[0])
        print "Usage..: %s <symbol pattern> <object file>+" % name
        print __doc__
    else:
        for file in sys.argv[2:]:
            get_address_ranges(file, sys.argv[1])