"Mini debuginfo" is a special section in ELF executables containing minimal compressed debuginfo for non-exported symbols:
https://sourceware.org/gdb/onlinedocs/gdb/MiniDebugInfo.html It lets debugging tools produce better stack traces, including local function names, without incurring the space overhead of full debuginfo. The feature was originally developed for Fedora: https://fedoraproject.org/wiki/Features/MiniDebugInfo but nowadays it is widely supported in the ecosystem, including in gdb and elfutils (and therefore also in tools which use elfutils, such as systemd-coredump). This patch adds an optional extra step in package.bbclass to inject minidebuginfo while stripping and splitting out debuginfo. It can be enabled by setting PACKAGE_MINIDEBUGINFO=1. In my testing, this increases the size of resulting binaries by roughly 5%. The code for producing and re-injecting the minidebuginfo is my own Python implementation but corresponds directly to the shell implementation that RPM uses for doing the same: https://github.com/rpm-software-management/rpm/blob/rpm-4.15.1-release/scripts/find-debuginfo.sh#L261 Signed-off-by: Dan Callaghan <[email protected]> --- meta/classes/package.bbclass | 84 ++++++++++++++++++++++++++++++++++++ 1 file changed, 84 insertions(+) diff --git a/meta/classes/package.bbclass b/meta/classes/package.bbclass index d4c6a90e84..648297ad25 100644 --- a/meta/classes/package.bbclass +++ b/meta/classes/package.bbclass @@ -245,6 +245,8 @@ python () { deps = "" for dep in (d.getVar('PACKAGE_DEPENDS') or "").split(): deps += " %s:do_populate_sysroot" % dep + if d.getVar('PACKAGE_MINIDEBUGINFO') == '1': + deps += ' xz-native:do_populate_sysroot' d.appendVarFlag('do_package', 'depends', deps) # shlibs requires any DEPENDS to have already packaged for the *.list files @@ -459,6 +461,83 @@ def splitstaticdebuginfo(file, dvar, debugstaticdir, debugstaticlibdir, debugsta return (file, sources) +def inject_minidebuginfo(file, dvar, debugdir, debuglibdir, debugappend, debugsrcdir, d): + # Extract just the symbols from debuginfo into minidebuginfo, + # compress it with xz and inject it back into the binary in a .gnu_debugdata section. + # https://sourceware.org/gdb/onlinedocs/gdb/MiniDebugInfo.html + + import subprocess + + readelf = d.getVar('READELF') + nm = d.getVar('NM') + objcopy = d.getVar('OBJCOPY') + + minidebuginfodir = d.expand('${WORKDIR}/minidebuginfo') + + src = file[len(dvar):] + dest = debuglibdir + os.path.dirname(src) + debugdir + "/" + os.path.basename(src) + debugappend + debugfile = dvar + dest + minidebugfile = minidebuginfodir + src + '.minidebug' + bb.utils.mkdirhier(os.path.dirname(minidebugfile)) + + # If we didn't produce debuginfo for any reason, we can't produce minidebuginfo either + # so skip it. + if not os.path.exists(debugfile): + bb.debug(1, 'ELF file {} has no debuginfo, skipping minidebuginfo injection'.format(file)) + return + + # Find non-allocated PROGBITS, NOTE, and NOBITS sections in the debuginfo. + # We will exclude all of these from minidebuginfo to save space. + remove_section_names = [] + for line in subprocess.check_output([readelf, '-W', '-S', debugfile], universal_newlines=True).splitlines(): + fields = line.split() + if len(fields) < 8: + continue + name = fields[0] + type = fields[1] + flags = fields[7] + # .debug_ sections will be removed by objcopy -S so no need to explicitly remove them + if name.startswith('.debug_'): + continue + if 'A' not in flags and type in ['PROGBITS', 'NOTE', 'NOBITS']: + remove_section_names.append(name) + + # List dynamic symbols in the binary. We can exclude these from minidebuginfo + # because they are always present in the binary. + dynsyms = set() + for line in subprocess.check_output([nm, '-D', file, '--format=posix', '--defined-only'], universal_newlines=True).splitlines(): + dynsyms.add(line.split()[0]) + + # Find all function symbols from debuginfo which aren't in the dynamic symbols table. + # These are the ones we want to keep in minidebuginfo. + keep_symbols_file = minidebugfile + '.symlist' + found_any_symbols = False + with open(keep_symbols_file, 'w') as f: + for line in subprocess.check_output([nm, debugfile, '--format=sysv', '--defined-only'], universal_newlines=True).splitlines(): + fields = line.split('|') + if len(fields) < 7: + continue + name = fields[0].strip() + type = fields[3].strip() + if type == 'FUNC' and name not in dynsyms: + f.write('{}\n'.format(name)) + found_any_symbols = True + + if not found_any_symbols: + bb.debug(1, 'ELF file {} contains no symbols, skipping minidebuginfo injection'.format(file)) + return + + bb.utils.remove(minidebugfile) + bb.utils.remove(minidebugfile + '.xz') + + subprocess.check_call([objcopy, '-S'] + + ['--remove-section={}'.format(s) for s in remove_section_names] + + ['--keep-symbols={}'.format(keep_symbols_file), debugfile, minidebugfile]) + + subprocess.check_call(['xz', '--keep', minidebugfile]) + + subprocess.check_call([objcopy, '--add-section', '.gnu_debugdata={}.xz'.format(minidebugfile), file]) + def copydebugsources(debugsrcdir, sources, d): # The debug src information written out to sourcefile is further processed # and copied to the destination here. @@ -1185,6 +1264,11 @@ python split_and_strip_files () { oe.utils.multiprocess_launch(oe.package.runstrip, sfiles, d) + # Build "minidebuginfo" and reinject it back into the stripped binaries + if d.getVar('PACKAGE_MINIDEBUGINFO') == '1': + oe.utils.multiprocess_launch(inject_minidebuginfo, list(elffiles), d, + extraargs=(dvar, debugdir, debuglibdir, debugappend, debugsrcdir, d)) + # # End of strip # -- 2.21.1
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