Sdk: Create build-ID-based hard links to detached debug symbols

Legacy path-based names are more difficult to use against a sysroot:
if your sysroot is in ~/sysroot and your detached debug symbols are
in ~/symbols, and you want to find detached debug symbols for
~/sysroot/usr/lib/x86_64-linux-gnu/libfoo.so.0 by using
"gdb -iex set-debug-file-directory /home/me/symbols:/usr/lib/debug",
then you would have to create a symlink
~/symbols/home/me/sysroot/usr pointing to ~/symbols/usr. Build-ID-based
names do not have this issue.

This change is based on code in steam-runtime, which uses symbolic
links. Hard links are a somewhat better fit for OSTree, since they
are automatically deduplicated, and also have the advantage that
multiple .build-id directories can easily be combined with rsync.
Signed-off-by: Simon McVittie <smcv@collabora.com>

flatdeb/dbgsym-use-build-id

+#!/usr/bin/env python3
+
+# Copyright 2013-2019 Valve Corporation
+# Copyright 2019 Collabora Ltd.
+#
+# SPDX-License-Identifier: MIT
+#
+# Permission is hereby granted, free of charge, to any person obtaining
+# a copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+#
+# The above copyright notice and this permission notice shall be included
+# in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+# CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+import argparse
+import logging
+import os
+import re
+import subprocess
+import sys
+
+
+"""
+Provide build-ID-based hard links to legacy path-based debugging symbols.
+
+Based on build-runtime.py in steam-runtime.
+"""
+
+
+logger = logging.getLogger('flatdeb.dbgsym-use-build-id')
+
+
+def main():
+    # type: (...) -> None
+
+    parser = argparse.ArgumentParser(
+        description=(
+            'Provide build-ID-based hard links for legacy debug symbols',
+        ),
+    )
+    parser.add_argument(
+        '--dry-run',
+        action='store_true',
+        default=False,
+    )
+    parser.add_argument('--debug-dir', default='/usr/lib/debug')
+
+    args = parser.parse_args()
+
+    for dirname, subdirs, files in os.walk(args.debug_dir):
+        # Skip build-ID directory: it is already in the form we wanted
+        if '.build-id' in subdirs:
+            subdirs.remove('.build-id')
+
+        for f in files:
+            # Scrape the output of readelf to find the build-ID for this
+            # binary
+            path = os.path.join(dirname, f)
+
+            with subprocess.Popen([
+                os.environ.get('READELF', 'readelf'), '-n', path,
+            ], stdout=subprocess.PIPE, universal_newlines=True) as p:
+                for line in p.stdout:
+                    m = re.search(
+                        r'Build ID: ([a-fA-F0-9]{2})([a-fA-F0-9]+)',
+                        line,
+                        re.ASCII,
+                    )
+                    if m is None:
+                        continue
+
+                    # ensure no path traversal
+                    assert '.' not in m.group(1)
+                    assert '.' not in m.group(2)
+                    linkdir = os.path.join(
+                        args.debug_dir, '.build-id', m.group(1),
+                    )
+                    link = os.path.join(linkdir, m.group(2) + '.debug')
+
+                    if args.dry_run:
+                        logger.info('Would hard-link %s as %s', path, link)
+                    else:
+                        logger.info('Hard-linking %s as %s', path, link)
+
+                        if not os.access(linkdir, os.W_OK):
+                            os.makedirs(linkdir)
+
+                        if os.path.lexists(link):
+                            os.unlink(link)
+
+                        os.link(os.path.join(dirname, f), link)
+
+                    break
+                else:
+                    logger.warning(
+                        'Unable to create build-ID-based hard link to %s',
+                        path,
+                    )
+
+
+if __name__ == '__main__':
+    if sys.stderr.isatty():
+        try:
+            import colorlog
+        except ImportError:
+            pass
+        else:
+            formatter = colorlog.ColoredFormatter(
+                '%(log_color)s%(levelname)s:%(name)s:%(reset)s %(message)s')
+            handler = logging.StreamHandler()
+            handler.setFormatter(formatter)
+            logging.getLogger().addHandler(handler)
+    else:
+        logging.basicConfig()
+
+    logging.getLogger().setLevel(logging.DEBUG)
+
+    try:
+        main()
+    except KeyboardInterrupt:
+        raise SystemExit(130)

flatdeb/debos-runtimes.yaml

@@ -234,6 +234,15 @@ actions:
     chroot: true
     script: symlink-alternatives
 
+  - action: run
+    label: dbgsym-use-build-id
+    chroot: false
+    command: |
+      set -eux
+      if [ -d "$ROOTDIR/usr/lib/debug" ]; then
+        "$RECIPEDIR/dbgsym-use-build-id" --debug-dir "$ROOTDIR/usr/lib/debug"
+      fi
+
   {{ if $sdk }}
   - action: run
     label: make-flatpak-friendly --sdk

run.py

@@ -827,6 +827,7 @@ class Builder:
                 'clean-up-base',
                 'clean-up-before-pack',
                 'collect-source-code',
+                'dbgsym-use-build-id',
                 'disable-services',
                 'make-flatpak-friendly',
                 'platformize',

t/mypy.sh

@@ -14,6 +14,7 @@ for script in \
     ./*.py \
     flatdeb/apt-install \
     flatdeb/collect-source-code \
+    flatdeb/dbgsym-use-build-id \
     flatdeb/purge-conffiles \
     flatdeb/set-build-id \
 ; do

t/pycodestyle.sh

@@ -14,6 +14,7 @@ elif "${PYCODESTYLE}" \
     ./*.py \
     flatdeb/apt-install \
     flatdeb/collect-source-code \
+    flatdeb/dbgsym-use-build-id \
     flatdeb/purge-conffiles \
     flatdeb/set-build-id \
     >&2; then

t/pyflakes.sh

@@ -14,6 +14,7 @@ elif "${PYFLAKES}" \
     ./*.py \
     flatdeb/apt-install \
     flatdeb/collect-source-code \
+    flatdeb/dbgsym-use-build-id \
     flatdeb/purge-conffiles \
     flatdeb/set-build-id \
     >&2; then