DWZ 06/06: Fix for symlinked .build-id/**.debug files

[jankratochvil]

Summary

So far /usr/lib/debug/.build-id/**.debug files could be opened any way. But with DWZ they can contain relative filename reference to /usr/lib/debug/.dwz/* files which then depends on whether the build-id .debug file is a symlink or not. Resolve the symlinks first before storing the filename for later references.

Without this fix I was getting:

warning: (x86_64) /usr/lib64/python3.6/lib-dynload/_heapq.cpython-36m-x86_64-linux-gnu.so Cannot get DWZ common file - file "/usr/lib/debug/.build-id/99/../../../../.dwz/python3-3.6.4-7.fc27.x86_64" cannot be opened

All DWZ patches are also applied in: git clone -b dwz git://git.jankratochvil.net/lldb

[labath]

source/Host/common/Symbols.cpp

283–287

Do we need to check the equivalentness twice? My impression is that this function "sees through" symlinks (and even if it didn't, doing it post-resolve should be enough).

[jankratochvil]

source/Host/common/Symbols.cpp

283–287

You are right, llvm::sys::fs::equivalent does st_dev+st_ino comparison.

[jankratochvil]

The testcase needs some updates after recent upstream testsuite changes.

[jankratochvil]

Replaced by D96243.

packages/Python/lldbsuite/test/decorators.py

 from __future__ import absolute_import
 from __future__ import print_function
 
 # System modules
 from distutils.version import LooseVersion, StrictVersion
 from functools import wraps
 import inspect
 import os
 import platform
 import re
 import sys
 import tempfile
+import distutils.spawn
 
 # Third-party modules
 import six
 import unittest2
 
 # LLDB modules
 import use_lldb_suite
 

 
 def skipIfXmlSupportMissing(func):
     config = lldb.SBDebugger.GetBuildConfiguration()
     xml = config.GetValueForKey("xml")
 
     fail_value = True # More likely to notice if something goes wrong
     have_xml = xml.GetValueForKey("value").GetBooleanValue(fail_value)
     return unittest2.skipIf(not have_xml, "requires xml support")(func)
+
+def skipUnlessDWZInstalled(func):
+    """Decorate the item to skip tests when no DWZ optimization tool is available.
+       /usr/lib/rpm/sepdebugcrcfix is not tested here but it may be needed
+       when build-ids cannot be used."""
+
+    def is_dwz_missing(self):
+        if distutils.spawn.find_executable("dwz") is None:
+            return "skipping because dwz is not found"
+        # dwz has a bug it can process only separate debug info files.
+        # Moreover dwz is compatible only with debug infos created by eu-strip.
+        if distutils.spawn.find_executable("eu-strip") is None:
+            return "skipping because eu-strip is not found"
+        return None
+    return skipTestIfFn(is_dwz_missing)(func)

packages/Python/lldbsuite/test/linux/buildidsymlink/Makefile

+LEVEL = ../../make
+C_SOURCES := main.c
+LD_EXTRAS += -Wl,--build-id=sha1
+
+all: .build-id
+
+.PHONY: .build-id
+stripped.out stripped.debug stripped.debug.dwz: a.out
+  eu-strip --remove-comment -f stripped.debug -F stripped.debugx -o stripped.out $<
+  cp -p stripped.debug stripped.debug.dup
+  dwz -m stripped.debug.dwz stripped.debug stripped.debug.dup
+
+.build-id: stripped.debug
+  $(OBJCOPY) -j .note.gnu.build-id -O binary $< tmp
+  rm -rf .build-id
+  fn=`od -An -tx1 <tmp|tr -d ' \n'|sed -e 's/^.\{32\}//' -e 's#^..#.build-id/&/#' -e 's#$$#.debug#'` && \
+  mkdir -p `dirname $$fn` && \
+  ln -s ../../$< $$fn
+  $(RM) tmp
+
+clean::
+  $(RM) -r stripped.out .build-id stripped.debug stripped.debug.dup stripped.debug.dwz
+
+include $(LEVEL)/Makefile.rules

packages/Python/lldbsuite/test/linux/buildidsymlink/TestTargetSymbolsBuildidSymlink.py

+""" Testing separate debug info loading for base binary with a symlink. """
+import os
+import time
+import lldb
+import sys
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestTargetSymbolsBuildidSymlink(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    @no_debug_info_test  # Prevent the genaration of the dwarf version of this test
+    @skipUnlessPlatform(['linux'])
+    @skipIf(hostoslist=["windows"])
+    @skipIfRemote # llvm.org/pr36237
+    @skipUnlessDWZInstalled
+    def test_target_symbols_buildid_symlink(self):
+        self.build(clean=True)
+        exe = self.getBuildArtifact("stripped.out")
+
+        lldbutil.run_to_name_breakpoint(self, "main", exe_name = exe)

packages/Python/lldbsuite/test/linux/buildidsymlink/main.c

+struct s {
+  int i1, i2, i3, i4, i5, i6, i7, i8, i9;
+} v;
+int main() {
+  return 0;
+}

source/Host/common/Symbols.cpp

for (size_t idx = 0; idx < num_directories; ++idx) {
       if (!file_dir.IsEmpty())
         files.push_back(dirname + file_dir.AsCString() + "/" + symbol_filename);
 
       const uint32_t num_files = files.size();
       for (size_t idx_file = 0; idx_file < num_files; ++idx_file) {
         const std::string &filename = files[idx_file];
         FileSpec file_spec(filename, true);
 
         if (llvm::sys::fs::equivalent(file_spec.GetPath(),
                                       module_file_spec.GetPath()))
           continue;
+        if (FileSystem::ResolveSymbolicLink(file_spec, file_spec).Fail())
+          continue;
 
         if (file_spec.Exists()) {
           lldb_private::ModuleSpecList specs;
           const size_t num_specs =
               ObjectFile::GetModuleSpecifications(file_spec, 0, 0, specs);
           assert(num_specs <= 1 &&
                  "Symbol Vendor supports only a single architecture");
           if (num_specs == 1) {