[Lldb-commits] [lldb] Fix the DWARF index cache when index is partial. (PR #118390)
Greg Clayton via lldb-commits
lldb-commits at lists.llvm.org
Mon Dec 2 11:41:17 PST 2024
https://github.com/clayborg created https://github.com/llvm/llvm-project/pull/118390
The ManualDWARFIndex class can create a index cache if the LLDB index cache is enabled. This used to save the index to the same file, regardless of wether the cache was a full index (no .debug_names) or a partial index (have .debug_names, but not all .o files were had .debug_names). So we could end up saving an index cache that was partial, and then later load that partial index as if it were a full index if the user set the 'settings set plugin.symbol-file.dwarf.ignore-file-indexes true'. This would cause us to ignore the .debug_names section, and if the index cache was enabled, we could end up loading the partial index as if it were a full DWARF index.
This patch detects when the ManualDWARFIndex is being used with .debug_names, and saves out a cache file with a suffix of "-full" or "-partial" to avoid this issue.
>From 8aa3f18f57908b4d1e5932ea5de94cf183b2542e Mon Sep 17 00:00:00 2001
From: Greg Clayton <clayborg at gmail.com>
Date: Mon, 2 Dec 2024 11:35:25 -0800
Subject: [PATCH] Fix the DWARF index cache when index is partial.
The ManualDWARFIndex class can create a index cache if the LLDB index cache is enabled. This used to save the index to the same file, regardless of wether the cache was a full index (no .debug_names) or a partial index (have .debug_names, but not all .o files were had .debug_names). So we could end up saving an index cache that was partial, and then later load that partial index as if it were a full index if the user set the 'settings set plugin.symbol-file.dwarf.ignore-file-indexes true'. This would cause us to ignore the .debug_names section, and if the index cache was enabled, we could end up loading the partial index as if it were a full DWARF index.
This patch detects when the ManualDWARFIndex is being used with .debug_names, and saves out a cache file with a suffix of "-full" or "-partial" to avoid this issue.
---
.../SymbolFile/DWARF/ManualDWARFIndex.cpp | 24 ++++++-
.../SymbolFile/DWARF/ManualDWARFIndex.h | 10 +++
.../SymbolFile/DWARF/x86/dwp-index-cache.cpp | 62 +++++++++++++++++++
3 files changed, 95 insertions(+), 1 deletion(-)
create mode 100644 lldb/test/Shell/SymbolFile/DWARF/x86/dwp-index-cache.cpp
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/ManualDWARFIndex.cpp b/lldb/source/Plugins/SymbolFile/DWARF/ManualDWARFIndex.cpp
index 1220e6115a2a95..0be19ab29ef082 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/ManualDWARFIndex.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/ManualDWARFIndex.cpp
@@ -706,6 +706,11 @@ bool ManualDWARFIndex::Encode(DataEncoder &encoder) const {
return true;
}
+bool ManualDWARFIndex::IsPartial() const {
+ // If we have units or type units to skip, then this index is partial.
+ return !m_units_to_avoid.empty() || !m_type_sigs_to_avoid.empty();
+}
+
std::string ManualDWARFIndex::GetCacheKey() {
std::string key;
llvm::raw_string_ostream strm(key);
@@ -713,9 +718,26 @@ std::string ManualDWARFIndex::GetCacheKey() {
// module can have one object file as the main executable and might have
// another object file in a separate symbol file, or we might have a .dwo file
// that claims its module is the main executable.
+
+ // This class can be used to index all of the DWARF, or part of the DWARF
+ // when there is a .debug_names index where some compile or type units were
+ // built without .debug_names. So we need to know when we have a full manual
+ // DWARF index or a partial manual DWARF index and save them to different
+ // cache files. Before this fix we might end up debugging a binary with
+ // .debug_names where some of the compile or type units weren't indexed, and
+ // find an issue with the .debug_names tables (bugs or being incomplete), and
+ // then we disable loading the .debug_names by setting a setting in LLDB by
+ // running "settings set plugin.symbol-file.dwarf.ignore-file-indexes 0" in
+ // another LLDB instance. The problem arose when there was an index cache from
+ // a previous run where .debug_names was enabled and it had saved a cache file
+ // that only covered the missing compile and type units from the .debug_names,
+ // and with the setting that disables the loading of the cache files we would
+ // load partial cache index cache. So we need to pick a unique cache suffix
+ // name that indicates if the cache is partial or full to avoid this problem.
+ llvm::StringRef dwarf_index_suffix(IsPartial() ? "partial-" : "full-");
ObjectFile *objfile = m_dwarf->GetObjectFile();
strm << objfile->GetModule()->GetCacheKey() << "-dwarf-index-"
- << llvm::format_hex(objfile->GetCacheHash(), 10);
+ << dwarf_index_suffix << llvm::format_hex(objfile->GetCacheHash(), 10);
return key;
}
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/ManualDWARFIndex.h b/lldb/source/Plugins/SymbolFile/DWARF/ManualDWARFIndex.h
index d8c4a22ab21f7b..6a52c88a99220f 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/ManualDWARFIndex.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/ManualDWARFIndex.h
@@ -168,6 +168,16 @@ class ManualDWARFIndex : public DWARFIndex {
const lldb::LanguageType cu_language,
IndexSet &set);
+ /// Return true if this manual DWARF index is covering only part of the DWARF.
+ ///
+ /// An instance of this class will be used to index all of the DWARF, but also
+ /// when we have .debug_names we will use one to index any compile or type
+ /// units that are not covered by the .debug_names table.
+ ///
+ /// \return
+ /// True if this index is a partial index, false otherwise.
+ bool IsPartial() const;
+
/// The DWARF file which we are indexing.
SymbolFileDWARF *m_dwarf;
/// Which dwarf units should we skip while building the index.
diff --git a/lldb/test/Shell/SymbolFile/DWARF/x86/dwp-index-cache.cpp b/lldb/test/Shell/SymbolFile/DWARF/x86/dwp-index-cache.cpp
new file mode 100644
index 00000000000000..3e97c3fb1ebc24
--- /dev/null
+++ b/lldb/test/Shell/SymbolFile/DWARF/x86/dwp-index-cache.cpp
@@ -0,0 +1,62 @@
+// REQUIRES: lld
+
+// Test if we build a mixed binary where one .o file has a .debug_names and
+// another doesn't have one, that we save a full or partial index cache.
+// Previous versions of LLDB would have ManualDWARFIndex.cpp that would save out
+// an index cache to the same file regardless of wether the index cache was a
+// full DWARF manual index, or just the CUs and TUs that were missing from any
+// .debug_names tables. If the user had a .debug_names table and debugged once
+// with index caching enabled, then debugged again but set the setting to ignore
+// .debug_names ('settings set plugin.symbol-file.dwarf.ignore-file-indexes 1')
+// this could cause LLDB to load the index cache from the previous run which
+// was incomplete and it only contained the manually indexed DWARF from the run
+// where we used .debug_names, but it would now load it as if it were the
+// complete DWARF index.
+
+// Test that if we don't have .debug_names, that we save a full DWARF index.
+// RUN: %clang -target x86_64-pc-linux -gsplit-dwarf -gdwarf-5 -DMAIN=1 -c %s -o %t.main.o
+// RUN: %clang -target x86_64-pc-linux -gsplit-dwarf -gdwarf-5 -DMAIN=0 -c %s -o %t.foo.o
+// RUN: ld.lld %t.main.o %t.foo.o -o %t.nonames
+// RUN: llvm-dwp %t.main.dwo %t.foo.dwo -o %t.nonames.dwp
+// RUN: rm %t.main.dwo %t.foo.dwo
+// Run one time with the index cache enabled to populate the index cache. When
+// we populate the index cache we have to parse all of the DWARF debug info
+// and it is always available.
+// RUN: rm -rf %t.lldb-index-cache
+// RUN: %lldb \
+// RUN: -O 'settings set symbols.enable-lldb-index-cache true' \
+// RUN: -O 'settings set symbols.lldb-index-cache-path %t.lldb-index-cache' \
+// RUN: -O 'settings set target.preload-symbols true' \
+// RUN: %t.nonames -b
+
+// Make sure there is a file with "dwarf-index-full" in its filename
+// RUN: ls %t.lldb-index-cache | FileCheck %s -check-prefix=FULL
+// FULL: {{dwp-index-cache.cpp.tmp.nonames.*-dwarf-index-full-}}
+
+// Test that if we have one .o file with .debug_names and one without, that we
+// save a partial DWARF index.
+// RUN: %clang -target x86_64-pc-linux -gsplit-dwarf -gdwarf-5 -DMAIN=1 -c %s -o %t.main.o -gpubnames
+// RUN: %clang -target x86_64-pc-linux -gsplit-dwarf -gdwarf-5 -DMAIN=0 -c %s -o %t.foo.o
+// RUN: ld.lld %t.main.o %t.foo.o -o %t.somenames
+// RUN: llvm-dwp %t.main.dwo %t.foo.dwo -o %t.somenames.dwp
+// RUN: rm %t.main.dwo %t.foo.dwo
+// Run one time with the index cache enabled to populate the index cache. When
+// we populate the index cache we have to parse all of the DWARF debug info
+// and it is always available.
+// RUN: rm -rf %t.lldb-index-cache
+// RUN: %lldb \
+// RUN: -O 'settings set symbols.enable-lldb-index-cache true' \
+// RUN: -O 'settings set symbols.lldb-index-cache-path %t.lldb-index-cache' \
+// RUN: -O 'settings set target.preload-symbols true' \
+// RUN: %t.somenames -b
+
+// Make sure there is a file with "dwarf-index-full" in its filename
+// RUN: ls %t.lldb-index-cache | FileCheck %s -check-prefix=PARTIAL
+// PARTIAL: {{dwp-index-cache.cpp.tmp.somenames.*-dwarf-index-partial-}}
+
+#if MAIN
+extern int foo();
+int main() { return foo(); }
+#else
+int foo() { return 0; }
+#endif
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