diff options
Diffstat (limited to 'dh_dwz')
| -rwxr-xr-x | dh_dwz | 185 |
1 files changed, 185 insertions, 0 deletions
@@ -0,0 +1,185 @@ +#!/usr/bin/perl + +=head1 NAME + +dh_dwz - optimize DWARF debug information in ELF binaries via dwz + +=cut + +use strict; +use warnings; +use File::Find; +use Debian::Debhelper::Dh_Lib; + +our $VERSION = DH_BUILTIN_VERSION; + +=head1 SYNOPSIS + +B<dh_dwz> [S<I<debhelper options>>] [B<-X>I<item>] [S<B<--> I<params>>] + +=head1 DESCRIPTION + +B<dh_dwz> is a debhelper program that will optimize the (uncompressed) +size of the DWARF debug information in ELF binaries. It does so by +running L<dwz(1)> on all the ELF binaries in the package. + +=head1 OPTIONS + +=over 4 + +=item B<--dwz-multifile>, B<--no-dwz-multifile> + +Whether L<dwz(1)> should generate a I<multifile> from the ELF binaries +in the same package. When enabled, if a package ships at least 2 ELF +binaries, B<dh_dwz> will instruct L<dwz(1)> to generate a multifile +for the package. + +By default, B<dh_dwz> will attempt to create a multifile but will +continue without if L<dwz(1)> does not create one (but succeeds anyway). +This commonly happens when the debug files do not contain debug +symbols (e.g. a missing -g to the compiler) or when the debug +symbols are compressed (see Debian bug #931891). If B<--dwz-multifile> +is passed, then B<dh_dwz> will abort with an error if L<dwz(1)> does +not create a multifile. + +Note this options may not work if a package contains more ELF binaries +than can fit on a single command line. If this becomes a problem, +please pass B<--no-dwz-multifile> to work around the issue. + +The generated multifile will be compressed with B<objcopy +--compress-debug-sections>. + +Note for B<udeb> packages: B<dh_dwz> will never generate multifiles +for B<udeb> packages. It will still use B<dwz> to reduce the +file size of debug files if it finds any. + +=item B<-X>I<item>, B<--exclude=>I<item> + +Exclude files that contain I<item> anywhere in their filename from being +stripped. You may use this option multiple times to build up a list of +things to exclude. + +=item B<--> I<params> + +Pass I<params> to L<dwz(1)> when it processes ELF binaries. This is +mostly useful for setting memory related parameters (e.g. -l and -L). + +=back + +=head1 NOTES + +If the B<DEB_BUILD_OPTIONS> environment variable contains B<nostrip>, +nothing will be stripped, in accordance with Debian policy (section +10.1 "Binaries"). + +While this tool technically does not remove debug information from +binaries, it is still skipped when the B<DEB_BUILD_OPTIONS> +environment variable contains B<nostrip>. This is because B<nostrip> +is often used to optimize build times (e.g. for "build and +test"-cycles) rather than optimizing for size. + +=cut + +my $create_multifile = 'auto'; + +init(options => { + 'dwz-multifile!' => \$create_multifile, +}); + +# This variable can be used to turn off stripping (see Policy). +exit 0 if get_buildoption('nostrip'); +if (not has_tool('dwz')) { + warning("Assuming bootstrap scenario and skipping regular dh_dwz feature, since dwz is not in PATH!"); + exit 0; +} + +my @elf_files; + +sub has_tool { + my ($cmd) = @_; + for my $p (split(m/:/, $ENV{PATH})) { + return 1 if -f -x "${p}/${cmd}"; + } + return 0; +} + +sub testfile { + my $fn = $_; + return if -l $fn; # Always skip symlinks. + + # See if we were asked to exclude this file. + # Note that we have to test on the full filename, including directory. + if (excludefile($fn)) { + $File::Find::prune = 1 if -d _; + return; + } + return if -d _; + # Do not process output files from dwz + return if index($fn, '/debug/.dwz/') > -1; + if (is_so_or_exec_elf_file($fn)) { + push(@elf_files, $fn); + } + return; +} + +on_items_in_parallel(\@{$dh{DOPACKAGES}}, sub { +foreach my $package (@_) { + my $tmp = tmpdir($package); + + next if not -d $tmp; + + @elf_files = (); + find({ + wanted => \&testfile, + no_chdir => 1, + }, $tmp); + next if not @elf_files; + # Consistent order; + @elf_files = sort(@elf_files); + my ($unique_files, $hardlinks) = find_hardlinks(@elf_files); + if ($create_multifile and @{$unique_files} > 1 and not is_udeb($package)) { + my $objcopy = cross_command($package, 'objcopy'); + my $ma_dir = dpkg_architecture_value('DEB_HOST_MULTIARCH'); + my $dwz_dir = "usr/lib/debug/.dwz/${ma_dir}"; + my $m = "${dwz_dir}/${package}.debug"; + my @dwz_options = ("-m${tmp}/${m}", "-M/${m}"); + install_dir("${tmp}/${dwz_dir}"); + doit('dwz', @dwz_options, @{$dh{U_PARAMS}}, '--', @{$unique_files}); + if ( -f "${tmp}/${m}") { + doit($objcopy, '--compress-debug-sections', "${tmp}/${m}"); + reset_perm_and_owner(0644, "${tmp}/${m}"); + } else { + error("dwz failed to create a multifile as requested") if $create_multifile ne 'auto'; + warning("No dwz multifile created, but not explicitly requested either so ignoring it."); + warning("Common issues include no debug information at all (missing -g) and"); + warning("compressed debug information (#931891)."); + # Clean up after ourselves to avoid leaving empty directories in packages + doit('rmdir', '-p', '--ignore-fail-on-non-empty', "${tmp}/${dwz_dir}"); + } + } else { + xargs($unique_files, 'dwz', @{$dh{U_PARAMS}}, '--'); + } + + + # Now change over any files we can that used to be hard links so + # they are again. + for my $hardlink (keys %{$hardlinks}) { + my $target = $hardlinks->{$hardlink}; + # Remove old file. + rm_files($hardlink); + # Make new hardlink. + doit('ln', '-f', $target, $hardlink); + } +}}); + +=head1 SEE ALSO + +L<debhelper(7)> + +This program is a part of debhelper. + +=head1 AUTHOR + +Niels Thykier <niels@thykier.net> + +=cut |