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SubjectRe: [PATCH] leaking_addresses: add 32-bit support
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Hi Tobin,

On Mon, 2018-01-29 at 15:51 +1100, Tobin C. Harding wrote:
> Currently script only supports x86_64 and ppc64. It would be nice to be
> able to scan 32-bit machines also. We can add support for
> 32-bit architectures by modifying how we check for false positives,
> taking advantage of the page offset used by the kernel, and using the
> correct regular expression.
>
> Support for 32-bit machines is enabled by the observation the kernel
> addresses on 32-bit machines are larger than the page offset. We can
> use this to filter false positives when scanning the kernel for leaking
> addresses.
>
> Programmatic determination of the running architecture is not
> immediately obvious. We therefore provide a flag to enable scanning of
> 32-bit kernels. Also we can check the kernel config file for the offset
> and if not found default to 0xc0000000. A command line option to parse
> in the page offset is also provided. We do automatically detect
> architecture if running on ix86.
>
> Add support for 32-bit kernels. Add a command line option for page
> offset.
>
> Suggested-by: Kaiwan N Billimoria <kaiwan.billimoria@gmail.com>
> Signed-off-by: Tobin C. Harding <me@tobin.cc>
> ---
>
> The basis for this patch has been in development for a while by Kaiwan
> but didn't get finished before the merge window opened. I'd like to
> fast track this and get it to Linus this merge window (considering
> Spectre/Meltdown). I have finished this work off and added the
> Suggested-by tag. Kaiwan I hope you are not upset by this, extra
> ordinary circumstances seemed to require this action.
Definitely not; I understand and am glad you're on it a 100%. Apologies
that I couldn't work on this right now.. will try and keep track too.

Thanks,
Kaiwan.
>
> thanks,
> Tobin.
>
> scripts/leaking_addresses.pl | 84 ++++++++++++++++++++++++++++++++++++++++----
> 1 file changed, 78 insertions(+), 6 deletions(-)
>
> diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl
> index 64a3cfa1175b..c13eb53d1c5a 100755
> --- a/scripts/leaking_addresses.pl
> +++ b/scripts/leaking_addresses.pl
> @@ -34,7 +34,7 @@ my $TIMEOUT = 10;
> # Script can only grep for kernel addresses on the following architectures. If
> # your architecture is not listed here and has a grep'able kernel address please
> # consider submitting a patch.
> -my @SUPPORTED_ARCHITECTURES = ('x86_64', 'ppc64');
> +my @SUPPORTED_ARCHITECTURES = ('x86_64', 'ppc64', 'x86');
>
> # Command line options.
> my $help = 0;
> @@ -46,6 +46,8 @@ 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 $page_offset_32bit = 0; # Page offset for 32-bit kernel.
>
> # Do not parse these files (absolute path).
> my @skip_parse_files_abs = ('/proc/kmsg',
> @@ -103,6 +105,8 @@ Options:
> --squash-by-path Show one result per unique path.
> --squash-by-filename Show one result per unique filename.
> --kernel-config-file=<file> Kernel configuration file (e.g /boot/config)
> + --32-bit Scan 32-bit kernel.
> + --page-offset-32-bit=o Page offset (for 32-bit kernel 0xABCD1234).
> -d, --debug Display debugging output.
> -h, --help, --versionq Display this help and exit.
>
> @@ -123,6 +127,8 @@ GetOptions(
> 'squash-by-filename' => \$squash_by_filename,
> 'raw' => \$raw,
> 'kernel-config-file=s' => \$kernel_config_file,
> + '32-bit' => \$opt_32bit,
> + 'page-offset-32-bit=o' => \$page_offset_32bit,
> ) or help(1);
>
> help(0) if ($help);
> @@ -138,7 +144,7 @@ if (!$input_raw and ($squash_by_path or $squash_by_filename)) {
> exit(128);
> }
>
> -if (!is_supported_architecture()) {
> +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) {
> @@ -146,6 +152,9 @@ if (!is_supported_architecture()) {
> }
> 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", $archname);
>
> @@ -169,7 +178,28 @@ sub dprint
>
> sub is_supported_architecture
> {
> - return (is_x86_64() or is_ppc64());
> + return (is_x86_64() or is_ppc64() or is_ix86_32());
> +}
> +
> +sub is_32bit
> +{
> + # Allow --32-bit or --page-offset-32-bit to override
> + if ($opt_32bit or $page_offset_32bit) {
> + return 1;
> + }
> +
> + return is_ix86_32();
> +}
> +
> +sub is_ix86_32
> +{
> + my $arch = `uname -m`;
> +
> + chomp $arch;
> + if ($arch =~ m/i[3456]86/) {
> + return 1;
> + }
> + return 0;
> }
>
> sub is_arch
> @@ -261,6 +291,12 @@ 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
> $match =~ '\b(0x)?0{16}\b') {
> return 1;
> @@ -273,6 +309,40 @@ sub is_false_positive
> return 0;
> }
>
> +sub is_false_positive_32bit
> +{
> + my ($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) = @_;
> @@ -314,11 +384,13 @@ sub may_leak_address
>
> sub get_address_re
> {
> - if (is_x86_64()) {
> - return get_x86_64_re();
> - } elsif (is_ppc64()) {
> + 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

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