scripts/leaking_addresses.pl - kernel/msm-5.4 - Gitiles

 #!/usr/bin/env perl
 #
 # (c) 2017 Tobin C. Harding <me@tobin.cc>
 # Licensed under the terms of the GNU GPL License version 2
 #
 # leaking_addresses.pl: Scan the kernel for potential leaking addresses.
 #  - Scans dmesg output.
 #  - Walks directory tree and parses each file (for each directory in @DIRS).
 #
 # Use --debug to output path before parsing, this is useful to find files that
 # cause the script to choke.

 #
 # When the system is idle it is likely that most files under /proc/PID will be
 # identical for various processes.  Scanning _all_ the PIDs under /proc is
 # unnecessary and implies that we are thoroughly scanning /proc.  This is _not_
 # the case because there may be ways userspace can trigger creation of /proc
 # files that leak addresses but were not present during a scan.  For these two
 # reasons we exclude all PID directories under /proc except '1/'

 use warnings;
 use strict;
 use POSIX;
 use File::Basename;
 use File::Spec;
 use Cwd 'abs_path';
 use Term::ANSIColor qw(:constants);
 use Getopt::Long qw(:config no_auto_abbrev);
 use Config;
 use bigint qw/hex/;
 use feature 'state';

 my $P = $0;

 # Directories to scan.
 my @DIRS = ('/proc', '/sys');

 # Timer for parsing each file, in seconds.
 my $TIMEOUT = 10;

 # Kernel addresses vary by architecture.  We can only auto-detect the following
 # architectures (using `uname -m`).  (flag --32-bit overrides auto-detection.)
 my @SUPPORTED_ARCHITECTURES = ('x86_64', 'ppc64', 'x86');

 # Command line options.
 my $help = 0;
 my $debug = 0;
 my $raw = 0;
 my $output_raw = "";	# Write raw results to file.
 my $input_raw = "";	# Read raw results from file instead of scanning.
 my $suppress_dmesg = 0;		# Don't show dmesg in output.
 my $squash_by_path = 0;		# Summary report grouped by absolute path.
 my $squash_by_filename = 0;	# Summary report grouped by filename.
 my $kernel_config_file = "";	# Kernel configuration file.
 my $opt_32bit = 0;		# Scan 32-bit kernel.
 my $page_offset_32bit = 0;	# Page offset for 32-bit kernel.

 # Skip these absolute paths.
 my @skip_abs = (
 	'/proc/kmsg',
 	'/proc/device-tree',
 	'/proc/1/syscall',
 	'/sys/firmware/devicetree',
 	'/sys/kernel/debug/tracing/trace_pipe',
 	'/sys/kernel/security/apparmor/revision');

 # Skip these under any subdirectory.
 my @skip_any = (
 	'pagemap',
 	'events',
 	'access',
 	'registers',
 	'snapshot_raw',
 	'trace_pipe_raw',
 	'ptmx',
 	'trace_pipe',
 	'fd',
 	'usbmon');

 sub help
 {
 	my ($exitcode) = @_;

 	print << "EOM";

 Usage: $P [OPTIONS]

 Options:

 	-o, --output-raw=<file>		Save results for future processing.
 	-i, --input-raw=<file>		Read results from file instead of scanning.
 	      --raw			Show raw results (default).
 	      --suppress-dmesg		Do not show dmesg results.
 	      --squash-by-path		Show one result per unique path.
 	      --squash-by-filename	Show one result per unique filename.
 	--kernel-config-file=<file>     Kernel configuration file (e.g /boot/config)
 	--32-bit			Scan 32-bit kernel.
 	--page-offset-32-bit=o		Page offset (for 32-bit kernel 0xABCD1234).
 	-d, --debug			Display debugging output.
 	-h, --help			Display this help and exit.

 Scans the running kernel for potential leaking addresses.

 EOM
 	exit($exitcode);
 }

 GetOptions(
 	'd|debug'		=> \$debug,
 	'h|help'		=> \$help,
 	'o|output-raw=s'        => \$output_raw,
 	'i|input-raw=s'         => \$input_raw,
 	'suppress-dmesg'        => \$suppress_dmesg,
 	'squash-by-path'        => \$squash_by_path,
 	'squash-by-filename'    => \$squash_by_filename,
 	'raw'                   => \$raw,
 	'kernel-config-file=s'	=> \$kernel_config_file,
 	'32-bit'		=> \$opt_32bit,
 	'page-offset-32-bit=o'	=> \$page_offset_32bit,
 ) or help(1);

 help(0) if ($help);

 if ($input_raw) {
 	format_output($input_raw);
 	exit(0);
 }

 if (!$input_raw and ($squash_by_path or $squash_by_filename)) {
 	printf "\nSummary reporting only available with --input-raw=<file>\n";
 	printf "(First run scan with --output-raw=<file>.)\n";
 	exit(128);
 }

 if (!(is_supported_architecture() or $opt_32bit or $page_offset_32bit)) {
 	printf "\nScript does not support your architecture, sorry.\n";
 	printf "\nCurrently we support: \n\n";
 	foreach(@SUPPORTED_ARCHITECTURES) {
 		printf "\t%s\n", $_;
 	}
 	printf("\n");

 	printf("If you are running a 32-bit architecture you may use:\n");
 	printf("\n\t--32-bit or --page-offset-32-bit=<page offset>\n\n");

 	my $archname = `uname -m`;
 	printf("Machine hardware name (`uname -m`): %s\n", $archname);

 	exit(129);
 }

 if ($output_raw) {
 	open my $fh, '>', $output_raw or die "$0: $output_raw: $!\n";
 	select $fh;
 }

 parse_dmesg();
 walk(@DIRS);

 exit 0;

 sub dprint
 {
 	printf(STDERR @_) if $debug;
 }

 sub is_supported_architecture
 {
 	return (is_x86_64() or is_ppc64() or is_ix86_32());
 }

 sub is_32bit
 {
 	# Allow --32-bit or --page-offset-32-bit to override
 	if ($opt_32bit or $page_offset_32bit) {
 		return 1;
 	}

 	return is_ix86_32();
 }

 sub is_ix86_32
 {
        state $arch = `uname -m`;

        chomp $arch;
        if ($arch =~ m/i[3456]86/) {
                return 1;
        }
        return 0;
 }

 sub is_arch
 {
        my ($desc) = @_;
        my $arch = `uname -m`;

        chomp $arch;
        if ($arch eq $desc) {
                return 1;
        }
        return 0;
 }

 sub is_x86_64
 {
 	state $is = is_arch('x86_64');
 	return $is;
 }

 sub is_ppc64
 {
 	state $is = is_arch('ppc64');
 	return $is;
 }

 # Gets config option value from kernel config file.
 # Returns "" on error or if config option not found.
 sub get_kernel_config_option
 {
 	my ($option) = @_;
 	my $value = "";
 	my $tmp_file = "";
 	my @config_files;

 	# Allow --kernel-config-file to override.
 	if ($kernel_config_file ne "") {
 		@config_files = ($kernel_config_file);
 	} elsif (-R "/proc/config.gz") {
 		my $tmp_file = "/tmp/tmpkconf";

 		if (system("gunzip < /proc/config.gz > $tmp_file")) {
 			dprint("system(gunzip < /proc/config.gz) failed\n");
 			return "";
 		} else {
 			@config_files = ($tmp_file);
 		}
 	} else {
 		my $file = '/boot/config-' . `uname -r`;
 		chomp $file;
 		@config_files = ($file, '/boot/config');
 	}

 	foreach my $file (@config_files) {
 		dprint("parsing config file: $file\n");
 		$value = option_from_file($option, $file);
 		if ($value ne "") {
 			last;
 		}
 	}

 	if ($tmp_file ne "") {
 		system("rm -f $tmp_file");
 	}

 	return $value;
 }

 # Parses $file and returns kernel configuration option value.
 sub option_from_file
 {
 	my ($option, $file) = @_;
 	my $str = "";
 	my $val = "";

 	open(my $fh, "<", $file) or return "";
 	while (my $line = <$fh> ) {
 		if ($line =~ /^$option/) {
 			($str, $val) = split /=/, $line;
 			chomp $val;
 			last;
 		}
 	}

 	close $fh;
 	return $val;
 }

 sub is_false_positive
 {
 	my ($match) = @_;

 	if (is_32bit()) {
 		return is_false_positive_32bit($match);
 	}

 	# 64 bit false positives.

 	if ($match =~ '\b(0x)?(f|F){16}\b' or
 	    $match =~ '\b(0x)?0{16}\b') {
 		return 1;
 	}

 	if (is_x86_64() and is_in_vsyscall_memory_region($match)) {
 		return 1;
 	}

 	return 0;
 }

 sub is_false_positive_32bit
 {
        my ($match) = @_;
        state $page_offset = get_page_offset();

        if ($match =~ '\b(0x)?(f|F){8}\b') {
                return 1;
        }

        if (hex($match) < $page_offset) {
                return 1;
        }

        return 0;
 }

 # returns integer value
 sub get_page_offset
 {
        my $page_offset;
        my $default_offset = 0xc0000000;

        # Allow --page-offset-32bit to override.
        if ($page_offset_32bit != 0) {
                return $page_offset_32bit;
        }

        $page_offset = get_kernel_config_option('CONFIG_PAGE_OFFSET');
        if (!$page_offset) {
 	       return $default_offset;
        }
        return $page_offset;
 }

 sub is_in_vsyscall_memory_region
 {
 	my ($match) = @_;

 	my $hex = hex($match);
 	my $region_min = hex("0xffffffffff600000");
 	my $region_max = hex("0xffffffffff601000");

 	return ($hex >= $region_min and $hex <= $region_max);
 }

 # True if argument potentially contains a kernel address.
 sub may_leak_address
 {
 	my ($line) = @_;
 	my $address_re;

 	# Signal masks.
 	if ($line =~ '^SigBlk:' or
 	    $line =~ '^SigIgn:' or
 	    $line =~ '^SigCgt:') {
 		return 0;
 	}

 	if ($line =~ '\bKEY=[[:xdigit:]]{14} [[:xdigit:]]{16} [[:xdigit:]]{16}\b' or
 	    $line =~ '\b[[:xdigit:]]{14} [[:xdigit:]]{16} [[:xdigit:]]{16}\b') {
 		return 0;
 	}

 	$address_re = get_address_re();
 	while ($line =~ /($address_re)/g) {
 		if (!is_false_positive($1)) {
 			return 1;
 		}
 	}

 	return 0;
 }

 sub get_address_re
 {
 	if (is_ppc64()) {
 		return '\b(0x)?[89abcdef]00[[:xdigit:]]{13}\b';
 	} elsif (is_32bit()) {
 		return '\b(0x)?[[:xdigit:]]{8}\b';
 	}

 	return get_x86_64_re();
 }

 sub get_x86_64_re
 {
 	# We handle page table levels but only if explicitly configured using
 	# CONFIG_PGTABLE_LEVELS.  If config file parsing fails or config option
 	# is not found we default to using address regular expression suitable
 	# for 4 page table levels.
 	state $ptl = get_kernel_config_option('CONFIG_PGTABLE_LEVELS');

 	if ($ptl == 5) {
 		return '\b(0x)?ff[[:xdigit:]]{14}\b';
 	}
 	return '\b(0x)?ffff[[:xdigit:]]{12}\b';
 }

 sub parse_dmesg
 {
 	open my $cmd, '-|', 'dmesg';
 	while (<$cmd>) {
 		if (may_leak_address($_)) {
 			print 'dmesg: ' . $_;
 		}
 	}
 	close $cmd;
 }

 # True if we should skip this path.
 sub skip
 {
 	my ($path) = @_;

 	foreach (@skip_abs) {
 		return 1 if (/^$path$/);
 	}

 	my($filename, $dirs, $suffix) = fileparse($path);
 	foreach (@skip_any) {
 		return 1 if (/^$filename$/);
 	}

 	return 0;
 }

 sub timed_parse_file
 {
 	my ($file) = @_;

 	eval {
 		local $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n required.
 		alarm $TIMEOUT;
 		parse_file($file);
 		alarm 0;
 	};

 	if ($@) {
 		die unless $@ eq "alarm\n";	# Propagate unexpected errors.
 		printf STDERR "timed out parsing: %s\n", $file;
 	}
 }

 sub parse_file
 {
 	my ($file) = @_;

 	if (! -R $file) {
 		return;
 	}

 	if (! -T $file) {
 		return;
 	}

 	open my $fh, "<", $file or return;
 	while ( <$fh> ) {
 		if (may_leak_address($_)) {
 			print $file . ': ' . $_;
 		}
 	}
 	close $fh;
 }

 # Checks if the actual path name is leaking a kernel address.
 sub check_path_for_leaks
 {
 	my ($path) = @_;

 	if (may_leak_address($path)) {
 		printf("Path name may contain address: $path\n");
 	}
 }

 # Recursively walk directory tree.
 sub walk
 {
 	my @dirs = @_;

 	while (my $pwd = shift @dirs) {
 		next if (!opendir(DIR, $pwd));
 		my @files = readdir(DIR);
 		closedir(DIR);

 		foreach my $file (@files) {
 			next if ($file eq '.' or $file eq '..');

 			my $path = "$pwd/$file";
 			next if (-l $path);

 			# skip /proc/PID except /proc/1
 			next if (($path =~ /^\/proc\/[0-9]+$/) &&
 				 ($path !~ /^\/proc\/1$/));

 			next if (skip($path));

 			check_path_for_leaks($path);

 			if (-d $path) {
 				push @dirs, $path;
 				next;
 			}

 			dprint("parsing: $path\n");
 			timed_parse_file($path);
 		}
 	}
 }

 sub format_output
 {
 	my ($file) = @_;

 	# Default is to show raw results.
 	if ($raw or (!$squash_by_path and !$squash_by_filename)) {
 		dump_raw_output($file);
 		return;
 	}

 	my ($total, $dmesg, $paths, $files) = parse_raw_file($file);

 	printf "\nTotal number of results from scan (incl dmesg): %d\n", $total;

 	if (!$suppress_dmesg) {
 		print_dmesg($dmesg);
 	}

 	if ($squash_by_filename) {
 		squash_by($files, 'filename');
 	}

 	if ($squash_by_path) {
 		squash_by($paths, 'path');
 	}
 }

 sub dump_raw_output
 {
 	my ($file) = @_;

 	open (my $fh, '<', $file) or die "$0: $file: $!\n";
 	while (<$fh>) {
 		if ($suppress_dmesg) {
 			if ("dmesg:" eq substr($_, 0, 6)) {
 				next;
 			}
 		}
 		print $_;
 	}
 	close $fh;
 }

 sub parse_raw_file
 {
 	my ($file) = @_;

 	my $total = 0;          # Total number of lines parsed.
 	my @dmesg;              # dmesg output.
 	my %files;              # Unique filenames containing leaks.
 	my %paths;              # Unique paths containing leaks.

 	open (my $fh, '<', $file) or die "$0: $file: $!\n";
 	while (my $line = <$fh>) {
 		$total++;

 		if ("dmesg:" eq substr($line, 0, 6)) {
 			push @dmesg, $line;
 			next;
 		}

 		cache_path(\%paths, $line);
 		cache_filename(\%files, $line);
 	}

 	return $total, \@dmesg, \%paths, \%files;
 }

 sub print_dmesg
 {
 	my ($dmesg) = @_;

 	print "\ndmesg output:\n";

 	if (@$dmesg == 0) {
 		print "<no results>\n";
 		return;
 	}

 	foreach(@$dmesg) {
 		my $index = index($_, ': ');
 		$index += 2;    # skid ': '
 		print substr($_, $index);
 	}
 }

 sub squash_by
 {
 	my ($ref, $desc) = @_;

 	print "\nResults squashed by $desc (excl dmesg). ";
 	print "Displaying [<number of results> <$desc>], <example result>\n";

 	if (keys %$ref == 0) {
 		print "<no results>\n";
 		return;
 	}

 	foreach(keys %$ref) {
 		my $lines = $ref->{$_};
 		my $length = @$lines;
 		printf "[%d %s] %s", $length, $_, @$lines[0];
 	}
 }

 sub cache_path
 {
 	my ($paths, $line) = @_;

 	my $index = index($line, ': ');
 	my $path = substr($line, 0, $index);

 	$index += 2;            # skip ': '
 	add_to_cache($paths, $path, substr($line, $index));
 }

 sub cache_filename
 {
 	my ($files, $line) = @_;

 	my $index = index($line, ': ');
 	my $path = substr($line, 0, $index);
 	my $filename = basename($path);

 	$index += 2;            # skip ': '
 	add_to_cache($files, $filename, substr($line, $index));
 }

 sub add_to_cache
 {
 	my ($cache, $key, $value) = @_;

 	if (!$cache->{$key}) {
 		$cache->{$key} = ();
 	}
 	push @{$cache->{$key}}, $value;
 }
	#!/usr/bin/env perl
	#
	# (c) 2017 Tobin C. Harding <me@tobin.cc>
	# Licensed under the terms of the GNU GPL License version 2
	#
	# leaking_addresses.pl: Scan the kernel for potential leaking addresses.
	# - Scans dmesg output.
	# - Walks directory tree and parses each file (for each directory in @DIRS).
	#
	# Use --debug to output path before parsing, this is useful to find files that
	# cause the script to choke.

	#
	# When the system is idle it is likely that most files under /proc/PID will be
	# identical for various processes. Scanning _all_ the PIDs under /proc is
	# unnecessary and implies that we are thoroughly scanning /proc. This is _not_
	# the case because there may be ways userspace can trigger creation of /proc
	# files that leak addresses but were not present during a scan. For these two
	# reasons we exclude all PID directories under /proc except '1/'

	use warnings;
	use strict;
	use POSIX;
	use File::Basename;
	use File::Spec;
	use Cwd 'abs_path';
	use Term::ANSIColor qw(:constants);
	use Getopt::Long qw(:config no_auto_abbrev);
	use Config;
	use bigint qw/hex/;
	use feature 'state';

	my $P = $0;

	# Directories to scan.
	my @DIRS = ('/proc', '/sys');

	# Timer for parsing each file, in seconds.
	my $TIMEOUT = 10;

	# Kernel addresses vary by architecture. We can only auto-detect the following
	# architectures (using `uname -m`). (flag --32-bit overrides auto-detection.)
	my @SUPPORTED_ARCHITECTURES = ('x86_64', 'ppc64', 'x86');

	# Command line options.
	my $help = 0;
	my $debug = 0;
	my $raw = 0;
	my $output_raw = ""; # Write raw results to file.
	my $input_raw = ""; # Read raw results from file instead of scanning.
	my $suppress_dmesg = 0; # Don't show dmesg in output.
	my $squash_by_path = 0; # Summary report grouped by absolute path.
	my $squash_by_filename = 0; # Summary report grouped by filename.
	my $kernel_config_file = ""; # Kernel configuration file.
	my $opt_32bit = 0; # Scan 32-bit kernel.
	my $page_offset_32bit = 0; # Page offset for 32-bit kernel.

	# Skip these absolute paths.
	my @skip_abs = (
	'/proc/kmsg',
	'/proc/device-tree',
	'/proc/1/syscall',
	'/sys/firmware/devicetree',
	'/sys/kernel/debug/tracing/trace_pipe',
	'/sys/kernel/security/apparmor/revision');

	# Skip these under any subdirectory.
	my @skip_any = (
	'pagemap',
	'events',
	'access',
	'registers',
	'snapshot_raw',
	'trace_pipe_raw',
	'ptmx',
	'trace_pipe',
	'fd',
	'usbmon');

	sub help
	{
	my ($exitcode) = @_;

	print << "EOM";

	Usage: $P [OPTIONS]

	Options:

	-o, --output-raw=<file> Save results for future processing.
	-i, --input-raw=<file> Read results from file instead of scanning.
	--raw Show raw results (default).
	--suppress-dmesg Do not show dmesg results.
	--squash-by-path Show one result per unique path.
	--squash-by-filename Show one result per unique filename.
	--kernel-config-file=<file> Kernel configuration file (e.g /boot/config)
	--32-bit Scan 32-bit kernel.
	--page-offset-32-bit=o Page offset (for 32-bit kernel 0xABCD1234).
	-d, --debug Display debugging output.
	-h, --help Display this help and exit.

	Scans the running kernel for potential leaking addresses.

	EOM
	exit($exitcode);
	}

	GetOptions(
	'd\|debug' => \$debug,
	'h\|help' => \$help,
	'o\|output-raw=s' => \$output_raw,
	'i\|input-raw=s' => \$input_raw,
	'suppress-dmesg' => \$suppress_dmesg,
	'squash-by-path' => \$squash_by_path,
	'squash-by-filename' => \$squash_by_filename,
	'raw' => \$raw,
	'kernel-config-file=s' => \$kernel_config_file,
	'32-bit' => \$opt_32bit,
	'page-offset-32-bit=o' => \$page_offset_32bit,
	) or help(1);

	help(0) if ($help);

	if ($input_raw) {
	format_output($input_raw);
	exit(0);
	}

	if (!$input_raw and ($squash_by_path or $squash_by_filename)) {
	printf "\nSummary reporting only available with --input-raw=<file>\n";
	printf "(First run scan with --output-raw=<file>.)\n";
	exit(128);
	}

	if (!(is_supported_architecture() or $opt_32bit or $page_offset_32bit)) {
	printf "\nScript does not support your architecture, sorry.\n";
	printf "\nCurrently we support: \n\n";
	foreach(@SUPPORTED_ARCHITECTURES) {
	printf "\t%s\n", $_;
	}
	printf("\n");

	printf("If you are running a 32-bit architecture you may use:\n");
	printf("\n\t--32-bit or --page-offset-32-bit=<page offset>\n\n");

	my $archname = `uname -m`;
	printf("Machine hardware name (`uname -m`): %s\n", $archname);

	exit(129);
	}

	if ($output_raw) {
	open my $fh, '>', $output_raw or die "$0: $output_raw: $!\n";
	select $fh;
	}

	parse_dmesg();
	walk(@DIRS);

	exit 0;

	sub dprint
	{
	printf(STDERR @_) if $debug;
	}

	sub is_supported_architecture
	{
	return (is_x86_64() or is_ppc64() or is_ix86_32());
	}

	sub is_32bit
	{
	# Allow --32-bit or --page-offset-32-bit to override
	if ($opt_32bit or $page_offset_32bit) {
	return 1;
	}

	return is_ix86_32();
	}

	sub is_ix86_32
	{
	state $arch = `uname -m`;

	chomp $arch;
	if ($arch =~ m/i[3456]86/) {
	return 1;
	}
	return 0;
	}

	sub is_arch
	{
	my ($desc) = @_;
	my $arch = `uname -m`;

	chomp $arch;
	if ($arch eq $desc) {
	return 1;
	}
	return 0;
	}

	sub is_x86_64
	{
	state $is = is_arch('x86_64');
	return $is;
	}

	sub is_ppc64
	{
	state $is = is_arch('ppc64');
	return $is;
	}

	# Gets config option value from kernel config file.
	# Returns "" on error or if config option not found.
	sub get_kernel_config_option
	{
	my ($option) = @_;
	my $value = "";
	my $tmp_file = "";
	my @config_files;

	# Allow --kernel-config-file to override.
	if ($kernel_config_file ne "") {
	@config_files = ($kernel_config_file);
	} elsif (-R "/proc/config.gz") {
	my $tmp_file = "/tmp/tmpkconf";

	if (system("gunzip < /proc/config.gz > $tmp_file")) {
	dprint("system(gunzip < /proc/config.gz) failed\n");
	return "";
	} else {
	@config_files = ($tmp_file);
	}
	} else {
	my $file = '/boot/config-' . `uname -r`;
	chomp $file;
	@config_files = ($file, '/boot/config');
	}

	foreach my $file (@config_files) {
	dprint("parsing config file: $file\n");
	$value = option_from_file($option, $file);
	if ($value ne "") {
	last;
	}
	}

	if ($tmp_file ne "") {
	system("rm -f $tmp_file");
	}

	return $value;
	}

	# Parses $file and returns kernel configuration option value.
	sub option_from_file
	{
	my ($option, $file) = @_;
	my $str = "";
	my $val = "";

	open(my $fh, "<", $file) or return "";
	while (my $line = <$fh> ) {
	if ($line =~ /^$option/) {
	($str, $val) = split /=/, $line;
	chomp $val;
	last;
	}
	}

	close $fh;
	return $val;
	}

	sub is_false_positive
	{
	my ($match) = @_;

	if (is_32bit()) {
	return is_false_positive_32bit($match);
	}

	# 64 bit false positives.

	if ($match =~ '\b(0x)?(f\|F){16}\b' or
	$match =~ '\b(0x)?0{16}\b') {
	return 1;
	}

	if (is_x86_64() and is_in_vsyscall_memory_region($match)) {
	return 1;
	}

	return 0;
	}

	sub is_false_positive_32bit
	{
	my ($match) = @_;
	state $page_offset = get_page_offset();

	if ($match =~ '\b(0x)?(f\|F){8}\b') {
	return 1;
	}

	if (hex($match) < $page_offset) {
	return 1;
	}

	return 0;
	}

	# returns integer value
	sub get_page_offset
	{
	my $page_offset;
	my $default_offset = 0xc0000000;

	# Allow --page-offset-32bit to override.
	if ($page_offset_32bit != 0) {
	return $page_offset_32bit;
	}

	$page_offset = get_kernel_config_option('CONFIG_PAGE_OFFSET');
	if (!$page_offset) {
	return $default_offset;
	}
	return $page_offset;
	}

	sub is_in_vsyscall_memory_region
	{
	my ($match) = @_;

	my $hex = hex($match);
	my $region_min = hex("0xffffffffff600000");
	my $region_max = hex("0xffffffffff601000");

	return ($hex >= $region_min and $hex <= $region_max);
	}

	# True if argument potentially contains a kernel address.
	sub may_leak_address
	{
	my ($line) = @_;
	my $address_re;

	# Signal masks.
	if ($line =~ '^SigBlk:' or
	$line =~ '^SigIgn:' or
	$line =~ '^SigCgt:') {
	return 0;
	}

	if ($line =~ '\bKEY=[[:xdigit:]]{14} [[:xdigit:]]{16} [[:xdigit:]]{16}\b' or
	$line =~ '\b[[:xdigit:]]{14} [[:xdigit:]]{16} [[:xdigit:]]{16}\b') {
	return 0;
	}

	$address_re = get_address_re();
	while ($line =~ /($address_re)/g) {
	if (!is_false_positive($1)) {
	return 1;
	}
	}

	return 0;
	}

	sub get_address_re
	{
	if (is_ppc64()) {
	return '\b(0x)?[89abcdef]00[[:xdigit:]]{13}\b';
	} elsif (is_32bit()) {
	return '\b(0x)?[[:xdigit:]]{8}\b';
	}

	return get_x86_64_re();
	}

	sub get_x86_64_re
	{
	# We handle page table levels but only if explicitly configured using
	# CONFIG_PGTABLE_LEVELS. If config file parsing fails or config option
	# is not found we default to using address regular expression suitable
	# for 4 page table levels.
	state $ptl = get_kernel_config_option('CONFIG_PGTABLE_LEVELS');

	if ($ptl == 5) {
	return '\b(0x)?ff[[:xdigit:]]{14}\b';
	}
	return '\b(0x)?ffff[[:xdigit:]]{12}\b';
	}

	sub parse_dmesg
	{
	open my $cmd, '-\|', 'dmesg';
	while (<$cmd>) {
	if (may_leak_address($_)) {
	print 'dmesg: ' . $_;
	}
	}
	close $cmd;
	}

	# True if we should skip this path.
	sub skip
	{
	my ($path) = @_;

	foreach (@skip_abs) {
	return 1 if (/^$path$/);
	}

	my($filename, $dirs, $suffix) = fileparse($path);
	foreach (@skip_any) {
	return 1 if (/^$filename$/);
	}

	return 0;
	}

	sub timed_parse_file
	{
	my ($file) = @_;

	eval {
	local $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n required.
	alarm $TIMEOUT;
	parse_file($file);
	alarm 0;
	};

	if ($@) {
	die unless $@ eq "alarm\n"; # Propagate unexpected errors.
	printf STDERR "timed out parsing: %s\n", $file;
	}
	}

	sub parse_file
	{
	my ($file) = @_;

	if (! -R $file) {
	return;
	}

	if (! -T $file) {
	return;
	}

	open my $fh, "<", $file or return;
	while ( <$fh> ) {
	if (may_leak_address($_)) {
	print $file . ': ' . $_;
	}
	}
	close $fh;
	}

	# Checks if the actual path name is leaking a kernel address.
	sub check_path_for_leaks
	{
	my ($path) = @_;

	if (may_leak_address($path)) {
	printf("Path name may contain address: $path\n");
	}
	}

	# Recursively walk directory tree.
	sub walk
	{
	my @dirs = @_;

	while (my $pwd = shift @dirs) {
	next if (!opendir(DIR, $pwd));
	my @files = readdir(DIR);
	closedir(DIR);

	foreach my $file (@files) {
	next if ($file eq '.' or $file eq '..');

	my $path = "$pwd/$file";
	next if (-l $path);

	# skip /proc/PID except /proc/1
	next if (($path =~ /^\/proc\/[0-9]+$/) &&
	($path !~ /^\/proc\/1$/));

	next if (skip($path));

	check_path_for_leaks($path);

	if (-d $path) {
	push @dirs, $path;
	next;
	}

	dprint("parsing: $path\n");
	timed_parse_file($path);
	}
	}
	}

	sub format_output
	{
	my ($file) = @_;

	# Default is to show raw results.
	if ($raw or (!$squash_by_path and !$squash_by_filename)) {
	dump_raw_output($file);
	return;
	}

	my ($total, $dmesg, $paths, $files) = parse_raw_file($file);

	printf "\nTotal number of results from scan (incl dmesg): %d\n", $total;

	if (!$suppress_dmesg) {
	print_dmesg($dmesg);
	}

	if ($squash_by_filename) {
	squash_by($files, 'filename');
	}

	if ($squash_by_path) {
	squash_by($paths, 'path');
	}
	}

	sub dump_raw_output
	{
	my ($file) = @_;

	open (my $fh, '<', $file) or die "$0: $file: $!\n";
	while (<$fh>) {
	if ($suppress_dmesg) {
	if ("dmesg:" eq substr($_, 0, 6)) {
	next;
	}
	}
	print $_;
	}
	close $fh;
	}

	sub parse_raw_file
	{
	my ($file) = @_;

	my $total = 0; # Total number of lines parsed.
	my @dmesg; # dmesg output.
	my %files; # Unique filenames containing leaks.
	my %paths; # Unique paths containing leaks.

	open (my $fh, '<', $file) or die "$0: $file: $!\n";
	while (my $line = <$fh>) {
	$total++;

	if ("dmesg:" eq substr($line, 0, 6)) {
	push @dmesg, $line;
	next;
	}

	cache_path(\%paths, $line);
	cache_filename(\%files, $line);
	}

	return $total, \@dmesg, \%paths, \%files;
	}

	sub print_dmesg
	{
	my ($dmesg) = @_;

	print "\ndmesg output:\n";

	if (@$dmesg == 0) {
	print "<no results>\n";
	return;
	}

	foreach(@$dmesg) {
	my $index = index($_, ': ');
	$index += 2; # skid ': '
	print substr($_, $index);
	}
	}

	sub squash_by
	{
	my ($ref, $desc) = @_;

	print "\nResults squashed by $desc (excl dmesg). ";
	print "Displaying [<number of results> <$desc>], <example result>\n";

	if (keys %$ref == 0) {
	print "<no results>\n";
	return;
	}

	foreach(keys %$ref) {
	my $lines = $ref->{$_};
	my $length = @$lines;
	printf "[%d %s] %s", $length, $_, @$lines[0];
	}
	}

	sub cache_path
	{
	my ($paths, $line) = @_;

	my $index = index($line, ': ');
	my $path = substr($line, 0, $index);

	$index += 2; # skip ': '
	add_to_cache($paths, $path, substr($line, $index));
	}

	sub cache_filename
	{
	my ($files, $line) = @_;

	my $index = index($line, ': ');
	my $path = substr($line, 0, $index);
	my $filename = basename($path);

	$index += 2; # skip ': '
	add_to_cache($files, $filename, substr($line, $index));
	}

	sub add_to_cache
	{
	my ($cache, $key, $value) = @_;

	if (!$cache->{$key}) {
	$cache->{$key} = ();
	}
	push @{$cache->{$key}}, $value;
	}