#!/usr/bin/perl
# check_stack --- check for too deep stack depths; it most likely only
#		only works for the linux kernel....

use 5.006;
use strict;
use warnings;
use Getopt::Std;
use lib "blib/lib";
use Disassemble::X86;

use vars qw ( $opt_d );
getopts ("d") and $#ARGV == 1 or die <<END_USAGE;
usage: $0 [-d] vmlinux System.map
-d  debug ON
END_USAGE

# slurp up the whole object file
open OBJ, "<$ARGV[0]" or die "$0: can't read $ARGV[0]: $!\n";
my $slash_save = $/;
undef $/;
my $file = <OBJ>;
close OBJ;
$/ = $slash_save;

# init the disassembler
my $dis = Disassemble::X86->new (
	start => 0xc0100000 - 0x1000,	# text addr - file offset
	pos   => 0,
	size  => 32,
	text  => $file,
);

# you may change these as you see fit

# max_check is the maximum number of instructions to scan for the 'sub esp,...'
#	before giving up
my $max_check = 10;

# stack_limit is the size that we'll consider worthy of reporting
my $stack_limit = 512;

# end of changables

# max_stack is the maximum stack size we saw
my $max_stack = 0;

# open System.map.  It contains the address, type, and names of each function
#		(among other things)
open MAP, "<$ARGV[1]" or die "$0: can't read $ARGV[1]: $!\n";

while (<MAP>) {
	my ($addr, $type, $name) = split (' ', $_);
	next if $name =~ /^\./;		# we don't want names like '.yadda'
	if ($type =~ /^[Tt]$/) {	# we only want text symbols
		print "looking at $name ($addr)\n" if $opt_d;

		$dis->pos (hex ($addr));
		for (my $i = 0; $i < $max_check && !$dis->at_end; $i++) {
			my $op = $dis->disasm ();
			printf "%04x %s\n", $dis->op_start (), $op if $opt_d;
			next if (!defined $op);
			if ($op =~ /sub esp,(0x[[:xdigit:]]+)/) {
				my $stack = hex ($1);
				$max_stack = $stack if $stack > $max_stack;
				printf "check $name (stack %d)\n", $stack
				    if $stack >= $stack_limit;
				last;
			}
		}

	}
}
close MAP;

print "max single stack used is $max_stack\n";

exit 0;

# end check_stack