llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-lldb
Author: Jason Molenda (jasonmolenda)
<details>
<summary>Changes</summary>
In
commit 2f63718f8567413a1c596bda803663eb58d6da5a
Author: Jason Molenda <jmolenda@<!-- -->apple.com>
Date: Tue Mar 26 09:07:15 2024 -0700
[lldb] Don't clear a Module's UnwindTable when adding a SymbolFile (#<!-- -->86603)
I stopped clearing a Module's UnwindTable when we add a SymbolFile to avoid the memory management problems with adding a symbol file asynchronously while the UnwindTable is being accessed on another thread. This broke the target-symbols-add-unwind.test shell test on Linux which removes the DWARF debub_frame section from a binary, loads it, then loads the unstripped binary with the DWARF debug_frame section and checks that the UnwindPlans for a function include debug_frame.
I originally decided that I was willing to sacrifice the possiblity of additional unwind sources from a symbol file because we rely on assembly emulation so heavily, they're rarely critical. But there are targets where we we don't have emluation and rely on things like DWARF debug_frame a lot more, so this probably wasn't a good choice.
This patch adds a new UnwindTable::Update method which looks for any new sources of unwind information and adds it to the UnwindTable, and calls that after a new SymbolFile has been added to a Module.
---
Full diff: https://github.com/llvm/llvm-project/pull/86770.diff
4 Files Affected:
- (modified) lldb/include/lldb/Symbol/UnwindTable.h (+4)
- (modified) lldb/source/Core/Module.cpp (+2)
- (modified) lldb/source/Symbol/UnwindTable.cpp (+45)
- (added) lldb/test/Shell/SymbolFile/target-symbols-add-unwind.test (+27)
``````````diff
diff --git a/lldb/include/lldb/Symbol/UnwindTable.h b/lldb/include/lldb/Symbol/UnwindTable.h
index f0ce7047de2d1e..26826e5d1b497c 100644
--- a/lldb/include/lldb/Symbol/UnwindTable.h
+++ b/lldb/include/lldb/Symbol/UnwindTable.h
@@ -57,6 +57,10 @@ class UnwindTable {
ArchSpec GetArchitecture();
+ /// Called after a SymbolFile has been added to a Module to add any new
+ /// unwind sections that may now be available.
+ void Update();
+
private:
void Dump(Stream &s);
diff --git a/lldb/source/Core/Module.cpp b/lldb/source/Core/Module.cpp
index a520523a96521a..9c105b3f0e57a1 100644
--- a/lldb/source/Core/Module.cpp
+++ b/lldb/source/Core/Module.cpp
@@ -1009,6 +1009,8 @@ SymbolFile *Module::GetSymbolFile(bool can_create, Stream *feedback_strm) {
m_symfile_up.reset(
SymbolVendor::FindPlugin(shared_from_this(), feedback_strm));
m_did_load_symfile = true;
+ if (m_unwind_table)
+ m_unwind_table->Update();
}
}
}
diff --git a/lldb/source/Symbol/UnwindTable.cpp b/lldb/source/Symbol/UnwindTable.cpp
index 3c1a5187b11054..11bedf3d6052e7 100644
--- a/lldb/source/Symbol/UnwindTable.cpp
+++ b/lldb/source/Symbol/UnwindTable.cpp
@@ -84,6 +84,51 @@ void UnwindTable::Initialize() {
}
}
+void UnwindTable::Update() {
+ if (!m_initialized)
+ return Initialize();
+
+ std::lock_guard<std::mutex> guard(m_mutex);
+
+ ObjectFile *object_file = m_module.GetObjectFile();
+ if (!object_file)
+ return;
+
+ if (!m_object_file_unwind_up)
+ m_object_file_unwind_up = object_file->CreateCallFrameInfo();
+
+ SectionList *sl = m_module.GetSectionList();
+ if (!sl)
+ return;
+
+ SectionSP sect = sl->FindSectionByType(eSectionTypeEHFrame, true);
+ if (!m_eh_frame_up && sect) {
+ m_eh_frame_up = std::make_unique<DWARFCallFrameInfo>(
+ *object_file, sect, DWARFCallFrameInfo::EH);
+ }
+
+ sect = sl->FindSectionByType(eSectionTypeDWARFDebugFrame, true);
+ if (!m_debug_frame_up && sect) {
+ m_debug_frame_up = std::make_unique<DWARFCallFrameInfo>(
+ *object_file, sect, DWARFCallFrameInfo::DWARF);
+ }
+
+ sect = sl->FindSectionByType(eSectionTypeCompactUnwind, true);
+ if (!m_compact_unwind_up && sect) {
+ m_compact_unwind_up =
+ std::make_unique<CompactUnwindInfo>(*object_file, sect);
+ }
+
+ sect = sl->FindSectionByType(eSectionTypeARMexidx, true);
+ if (!m_arm_unwind_up && sect) {
+ SectionSP sect_extab = sl->FindSectionByType(eSectionTypeARMextab, true);
+ if (sect_extab.get()) {
+ m_arm_unwind_up =
+ std::make_unique<ArmUnwindInfo>(*object_file, sect, sect_extab);
+ }
+ }
+}
+
UnwindTable::~UnwindTable() = default;
std::optional<AddressRange>
diff --git a/lldb/test/Shell/SymbolFile/target-symbols-add-unwind.test b/lldb/test/Shell/SymbolFile/target-symbols-add-unwind.test
new file mode 100644
index 00000000000000..5420213d405e86
--- /dev/null
+++ b/lldb/test/Shell/SymbolFile/target-symbols-add-unwind.test
@@ -0,0 +1,27 @@
+# TODO: When it's possible to run "image show-unwind" without a running
+# process, we can remove the unsupported line below, and hard-code an ELF
+# triple in the test.
+# UNSUPPORTED: system-windows, system-darwin
+
+# RUN: cd %T
+# RUN: %clang_host %S/Inputs/target-symbols-add-unwind.c -g \
+# RUN: -fno-unwind-tables -fno-asynchronous-unwind-tables \
+# RUN: -o target-symbols-add-unwind.debug
+# RUN: llvm-objcopy --strip-debug target-symbols-add-unwind.debug \
+# RUN: target-symbols-add-unwind.stripped
+# RUN: %lldb target-symbols-add-unwind.stripped -s %s -o quit | FileCheck %s
+
+process launch --stop-at-entry
+image show-unwind -n main
+# CHECK-LABEL: image show-unwind -n main
+# CHECK-NOT: debug_frame UnwindPlan:
+
+target symbols add -s target-symbols-add-unwind.stripped target-symbols-add-unwind.debug
+# CHECK-LABEL: target symbols add
+# CHECK: symbol file {{.*}} has been added to {{.*}}
+
+image show-unwind -n main
+# CHECK-LABEL: image show-unwind -n main
+# CHECK: debug_frame UnwindPlan:
+# CHECK-NEXT: This UnwindPlan originally sourced from DWARF CFI
+# CHECK-NEXT: This UnwindPlan is sourced from the compiler: yes.
``````````
</details>
https://github.com/llvm/llvm-project/pull/86770