avstack.pl

#!/usr/bin/perl -w
# avstack.pl: AVR stack checker
# Copyright (C) 2013 Daniel Beer <[email protected]>
#
# Permission to use, copy, modify, and/or distribute this software for
# any purpose with or without fee is hereby granted, provided that the
# above copyright notice and this permission notice appear in all
# copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
# WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
# WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
# AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
# DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
# PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
# TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
# PERFORMANCE OF THIS SOFTWARE.
#
# Usage
# -----
#
# This script requires that you compile your code with -fstack-usage.
# This results in GCC generating a .su file for each .o file. Once you
# have these, do:
#
#    ./avstack.pl <object files>
#
# This will disassemble .o files to construct a call graph, and read
# frame size information from .su. The call graph is traced to find, for
# each function:
#
#    - Call height: the maximum call height of any callee, plus 1
#      (defined to be 1 for any function which has no callees).
#
#    - Inherited frame: the maximum *inherited* frame of any callee, plus
#      the GCC-calculated frame size of the function in question.
#
# Using these two pieces of information, we calculate a cost (estimated
# peak stack usage) for calling the function. Functions are then listed
# on stdout in decreasing order of cost.
#
# Functions which are recursive are marked with an 'R' to the left of
# them. Their cost is calculated for a single level of recursion.
#
# The peak stack usage of your entire program can usually be estimated
# as the stack cost of "main", plus the maximum stack cost of any
# interrupt handler which might execute.

use strict;

# Configuration: set these as appropriate for your architecture/project.

my $objdump = "arm-none-eabi-objdump";
my $call_cost = 4;

# First, we need to read all object and corresponding .su files. We're
# gathering a mapping of functions to callees and functions to frame
# sizes. We're just parsing at this stage -- callee name resolution
# comes later.

my %frame_size;     # "func@file" -> size
my %call_graph;     # "func@file" -> {callees}
my %addresses;      # "addr@file" -> "func@file"

my %global_name;    # "func" -> "func@file"
my %ambiguous;      # "func" -> 1

foreach (@ARGV) {
	# Disassemble this object file to obtain a callees. Sources in the
	# call graph are named "func@file". Targets in the call graph are
	# named either "offset@file" or "funcname". We also keep a list of
	# the addresses and names of each function we encounter.
	my $objfile = $_;
	my $source;

	open(DISASSEMBLY, "$objdump -dr $objfile|") ||
	die "Can't disassemble $objfile";
	while (<DISASSEMBLY>) {
		chomp;

		if (/^([0-9a-fA-F]+) <(.*)>:/) {
			my $a = $1;
			my $name = $2;

			$source = "$name\@$objfile";
			$call_graph{$source} = {};
			$ambiguous{$name} = 1 if defined($global_name{$name});
			$global_name{$name} = "$name\@$objfile";

			$a =~ s/^0*//;
			$addresses{"$a\@$objfile"} = "$name\@$objfile";
		}

		if (/: R_[A-Za-z0-9_]+_CALL[ \t]+(.*)/) {
			my $t = $1;

			if ($t eq ".text") {
				$t = "\@$objfile";
			} elsif ($t =~ /^\.text\+0x(.*)$/) {
				$t = "$1\@$objfile";
			}

			$call_graph{$source}->{$t} = 1;
		}
	}
	close(DISASSEMBLY);

	# Extract frame sizes from the corresponding .su file.
	if ($objfile =~ /^(.*).o$/) {
		my $sufile = "$1.su";

		eval {
			open(SUFILE, "<$sufile") || die "Can't open $sufile";
			while (<SUFILE>) {
				$frame_size{"$1\@$objfile"} = $2 + $call_cost
				if /^.*:([^\t ]+)[ \t]+([0-9]+)/;
			}
			close(SUFILE);
		};
		if ($@) {
			warn $@;
		}
	}
}

# In this step, we enumerate each list of callees in the call graph and
# try to resolve the symbols. We omit ones we can't resolve, but keep a
# set of them anyway.

my %unresolved;

foreach (keys %call_graph) {
	my $from = $_;
	my $callees = $call_graph{$from};
	my %resolved;

	foreach (keys %$callees) {
		my $t = $_;

		if (defined($addresses{$t})) {
			$resolved{$addresses{$t}} = 1;
		} elsif (defined($global_name{$t})) {
			$resolved{$global_name{$t}} = 1;
			warn "Ambiguous resolution: $t" if defined ($ambiguous{$t});
		} elsif (defined($call_graph{$t})) {
			$resolved{$t} = 1;
		} else {
			$unresolved{$t} = 1;
		}
	}

	$call_graph{$from} = \%resolved;
}

# Create fake edges and nodes to account for dynamic behaviour.
$call_graph{"INTERRUPT"} = {};

foreach (keys %call_graph) {
	$call_graph{"INTERRUPT"}->{$_} = 1 if /^__vector_/;
}

# Trace the call graph and calculate, for each function:
#
#    - inherited frames: maximum inherited frame of callees, plus own
#      frame size.
#    - height: maximum height of callees, plus one.
#    - recursion: is the function called recursively (including indirect
#      recursion)?

my %has_caller;
my %visited;
my %total_cost;
my %call_depth;

sub trace {
	my $f = shift;

	if ($visited{$f}) {
		$visited{$f} = "R" if $visited{$f} eq "?";
		return;
	}

	$visited{$f} = "?";

	my $max_depth = 0;
	my $max_frame = 0;

	my $targets = $call_graph{$f} || die "Unknown function: $f";
	if (defined($targets)) {
		foreach (keys %$targets) {
			my $t = $_;

			$has_caller{$t} = 1;
			trace($t);

			my $is = $total_cost{$t};
			my $d = $call_depth{$t};

			$max_frame = $is if $is > $max_frame;
			$max_depth = $d if $d > $max_depth;
		}
	}

	$call_depth{$f} = $max_depth + 1;
	$total_cost{$f} = $max_frame + ($frame_size{$f} || 0);
	$visited{$f} = " " if $visited{$f} eq "?";
}

foreach (keys %call_graph) { trace $_; }

# Now, print results in a nice table.
printf "  %-30s %8s %8s %8s\n",
"Func", "Cost", "Frame", "Height";
print "------------------------------------";
print "------------------------------------\n";

my $max_iv = 0;
my $main = 0;

sub print_result {
	my ($_, $n) = @_;
	my $name = $_;
	my $cg = $call_graph{$_};
	if (/^(.*)@(.*)$/) {
		$name = $1 unless $ambiguous{$name};
	}

	my $tag = $visited{$_};
	my $cost = $total_cost{$_};

	$name = $_ if $ambiguous{$name};
	$tag = ">" unless $has_caller{$_};

	if (/^__vector_/) {
		$max_iv = $cost if $cost > $max_iv;
	} elsif (/^main@/) {
		$main = $cost;
	}

	if ($ambiguous{$name}) { $name = $_; }

	printf "%s %-50s %8d %8d %8d\n", $tag, '-' x ($n || 0) . $name, $cost, $frame_size{$_} || 0, $call_depth{$_};
	my $top = [ sort { $total_cost{$b} <=> $total_cost{$a} } keys %$cg ]->[0];
	return unless $top;
	print_result($top, ($n || 0) + 1);
}

foreach (sort { $total_cost{$b} <=> $total_cost{$a} } keys %visited) {
	print_result($_);
}

print "\n";

print "Peak execution estimate (main + worst-case IV):\n";
printf "  main = %d, worst IV = %d, total = %d\n",
$total_cost{$global_name{"main"}},
$total_cost{"INTERRUPT"},
$total_cost{$global_name{"main"}} + $total_cost{"INTERRUPT"};

print "\n";

print "The following functions were not resolved:\n";
foreach (keys %unresolved) { print "  $_\n"; }