[lldb] Remove unused UnwindPlan functions

[labath]

GetLSDAAddress and GetPersonalityRoutinePtrAddress are unused and they create a bit of a problem for discontinuous functions, because the unwind plan for these consists of multiple eh_frame descriptors and (at least in theory) each of them could have a different value for these entities.

We could say we only support functions for which these are always the same, or create some sort of a Address2LSDA lookup map, but I think it's better to leave this question to someone who actually needs this.

[llvmbot]

@llvm/pr-subscribers-lldb

Author: Pavel Labath (labath)

Changes

GetLSDAAddress and GetPersonalityRoutinePtrAddress are unused and they create a bit of a problem for discontinuous functions, because the unwind plan for these consists of multiple eh_frame descriptors and (at least in theory) each of them could have a different value for these entities.

We could say we only support functions for which these are always the same, or create some sort of a Address2LSDA lookup map, but I think it's better to leave this question to someone who actually needs this.

---

Full diff: https://github.com/llvm/llvm-project/pull/134630.diff

6 Files Affected:

• (modified) lldb/include/lldb/Symbol/FuncUnwinders.h (-13)
• (modified) lldb/include/lldb/Symbol/UnwindPlan.h (+1-22)
• (modified) lldb/source/Symbol/CompactUnwindInfo.cpp (-12)
• (modified) lldb/source/Symbol/DWARFCallFrameInfo.cpp (+4-34)
• (modified) lldb/source/Symbol/FuncUnwinders.cpp (-36)
• (modified) lldb/source/Symbol/UnwindPlan.cpp (-13)

diff --git a/lldb/include/lldb/Symbol/FuncUnwinders.h b/lldb/include/lldb/Symbol/FuncUnwinders.h
index 479ccf87b6e2c..c21a1af5c56a2 100644
--- a/lldb/include/lldb/Symbol/FuncUnwinders.h
+++ b/lldb/include/lldb/Symbol/FuncUnwinders.h
@@ -61,19 +61,6 @@ class FuncUnwinders {
     });
   }
 
-  // A function may have a Language Specific Data Area specified -- a block of
-  // data in
-  // the object file which is used in the processing of an exception throw /
-  // catch. If any of the UnwindPlans have the address of the LSDA region for
-  // this function, this will return it.
-  Address GetLSDAAddress(Target &target);
-
-  // A function may have a Personality Routine associated with it -- used in the
-  // processing of throwing an exception.  If any of the UnwindPlans have the
-  // address of the personality routine, this will return it.  Read the target-
-  // pointer at this address to get the personality function address.
-  Address GetPersonalityRoutinePtrAddress(Target &target);
-
   // The following methods to retrieve specific unwind plans should rarely be
   // used. Instead, clients should ask for the *behavior* they are looking for,
   // using one of the above UnwindPlan retrieval methods.
diff --git a/lldb/include/lldb/Symbol/UnwindPlan.h b/lldb/include/lldb/Symbol/UnwindPlan.h
index 6640a23a3e868..eee932492a550 100644
--- a/lldb/include/lldb/Symbol/UnwindPlan.h
+++ b/lldb/include/lldb/Symbol/UnwindPlan.h
@@ -445,9 +445,7 @@ class UnwindPlan {
         m_plan_is_sourced_from_compiler(rhs.m_plan_is_sourced_from_compiler),
         m_plan_is_valid_at_all_instruction_locations(
             rhs.m_plan_is_valid_at_all_instruction_locations),
-        m_plan_is_for_signal_trap(rhs.m_plan_is_for_signal_trap),
-        m_lsda_address(rhs.m_lsda_address),
-        m_personality_func_addr(rhs.m_personality_func_addr) {
+        m_plan_is_for_signal_trap(rhs.m_plan_is_for_signal_trap) {
     m_row_list.reserve(rhs.m_row_list.size());
     for (const RowSP &row_sp : rhs.m_row_list)
       m_row_list.emplace_back(new Row(*row_sp));
@@ -553,22 +551,10 @@ class UnwindPlan {
     m_plan_is_sourced_from_compiler = eLazyBoolCalculate;
     m_plan_is_valid_at_all_instruction_locations = eLazyBoolCalculate;
     m_plan_is_for_signal_trap = eLazyBoolCalculate;
-    m_lsda_address.Clear();
-    m_personality_func_addr.Clear();
   }
 
   const RegisterInfo *GetRegisterInfo(Thread *thread, uint32_t reg_num) const;
 
-  Address GetLSDAAddress() const { return m_lsda_address; }
-
-  void SetLSDAAddress(Address lsda_addr) { m_lsda_address = lsda_addr; }
-
-  Address GetPersonalityFunctionPtr() const { return m_personality_func_addr; }
-
-  void SetPersonalityFunctionPtr(Address presonality_func_ptr) {
-    m_personality_func_addr = presonality_func_ptr;
-  }
-
 private:
   std::vector<RowSP> m_row_list;
   std::vector<AddressRange> m_plan_valid_ranges;
@@ -583,13 +569,6 @@ class UnwindPlan {
   lldb_private::LazyBool m_plan_is_sourced_from_compiler;
   lldb_private::LazyBool m_plan_is_valid_at_all_instruction_locations;
   lldb_private::LazyBool m_plan_is_for_signal_trap;
-
-  Address m_lsda_address; // Where the language specific data area exists in the
-                          // module - used
-                          // in exception handling.
-  Address m_personality_func_addr; // The address of a pointer to the
-                                   // personality function - used in
-                                   // exception handling.
 };                                 // class UnwindPlan
 
 } // namespace lldb_private
diff --git a/lldb/source/Symbol/CompactUnwindInfo.cpp b/lldb/source/Symbol/CompactUnwindInfo.cpp
index 3c97d2ca11fbc..cdbbeb554c688 100644
--- a/lldb/source/Symbol/CompactUnwindInfo.cpp
+++ b/lldb/source/Symbol/CompactUnwindInfo.cpp
@@ -741,9 +741,6 @@ bool CompactUnwindInfo::CreateUnwindPlan_x86_64(Target &target,
   unwind_plan.SetUnwindPlanForSignalTrap(eLazyBoolNo);
   unwind_plan.SetRegisterKind(eRegisterKindEHFrame);
 
-  unwind_plan.SetLSDAAddress(function_info.lsda_address);
-  unwind_plan.SetPersonalityFunctionPtr(function_info.personality_ptr_address);
-
   UnwindPlan::Row row;
 
   const int wordsize = 8;
@@ -1011,9 +1008,6 @@ bool CompactUnwindInfo::CreateUnwindPlan_i386(Target &target,
   unwind_plan.SetUnwindPlanForSignalTrap(eLazyBoolNo);
   unwind_plan.SetRegisterKind(eRegisterKindEHFrame);
 
-  unwind_plan.SetLSDAAddress(function_info.lsda_address);
-  unwind_plan.SetPersonalityFunctionPtr(function_info.personality_ptr_address);
-
   UnwindPlan::Row row;
 
   const int wordsize = 4;
@@ -1306,9 +1300,6 @@ bool CompactUnwindInfo::CreateUnwindPlan_arm64(Target &target,
   unwind_plan.SetUnwindPlanForSignalTrap(eLazyBoolNo);
   unwind_plan.SetRegisterKind(eRegisterKindEHFrame);
 
-  unwind_plan.SetLSDAAddress(function_info.lsda_address);
-  unwind_plan.SetPersonalityFunctionPtr(function_info.personality_ptr_address);
-
   UnwindPlan::Row row;
 
   const int wordsize = 8;
@@ -1437,9 +1428,6 @@ bool CompactUnwindInfo::CreateUnwindPlan_armv7(Target &target,
   unwind_plan.SetUnwindPlanForSignalTrap(eLazyBoolNo);
   unwind_plan.SetRegisterKind(eRegisterKindEHFrame);
 
-  unwind_plan.SetLSDAAddress(function_info.lsda_address);
-  unwind_plan.SetPersonalityFunctionPtr(function_info.personality_ptr_address);
-
   UnwindPlan::Row row;
 
   const int wordsize = 4;
diff --git a/lldb/source/Symbol/DWARFCallFrameInfo.cpp b/lldb/source/Symbol/DWARFCallFrameInfo.cpp
index 957818e8d077f..1ea2dce85a930 100644
--- a/lldb/source/Symbol/DWARFCallFrameInfo.cpp
+++ b/lldb/source/Symbol/DWARFCallFrameInfo.cpp
@@ -583,43 +583,13 @@ bool DWARFCallFrameInfo::FDEToUnwindPlan(dw_offset_t dwarf_offset,
                      m_objfile.GetSectionList());
   range.SetByteSize(range_len);
 
-  addr_t lsda_data_file_address = LLDB_INVALID_ADDRESS;
-
-  if (cie->augmentation[0] == 'z') {
-    uint32_t aug_data_len = (uint32_t)m_cfi_data.GetULEB128(&offset);
-    if (aug_data_len != 0 && cie->lsda_addr_encoding != DW_EH_PE_omit) {
-      lldb::offset_t saved_offset = offset;
-      lsda_data_file_address =
-          GetGNUEHPointer(m_cfi_data, &offset, cie->lsda_addr_encoding,
-                          pc_rel_addr, text_addr, data_addr);
-      if (offset - saved_offset != aug_data_len) {
-        // There is more in the augmentation region than we know how to process;
-        // don't read anything.
-        lsda_data_file_address = LLDB_INVALID_ADDRESS;
-      }
-      offset = saved_offset;
-    }
-    offset += aug_data_len;
-  }
+  // Skip the LSDA, if present.
+  if (cie->augmentation[0] == 'z')
+    offset += (uint32_t)m_cfi_data.GetULEB128(&offset);
+
   unwind_plan.SetUnwindPlanForSignalTrap(
     strchr(cie->augmentation, 'S') ? eLazyBoolYes : eLazyBoolNo);
 
-  Address lsda_data;
-  Address personality_function_ptr;
-
-  if (lsda_data_file_address != LLDB_INVALID_ADDRESS &&
-      cie->personality_loc != LLDB_INVALID_ADDRESS) {
-    m_objfile.GetModule()->ResolveFileAddress(lsda_data_file_address,
-                                              lsda_data);
-    m_objfile.GetModule()->ResolveFileAddress(cie->personality_loc,
-                                              personality_function_ptr);
-  }
-
-  if (lsda_data.IsValid() && personality_function_ptr.IsValid()) {
-    unwind_plan.SetLSDAAddress(lsda_data);
-    unwind_plan.SetPersonalityFunctionPtr(personality_function_ptr);
-  }
-
   uint32_t code_align = cie->code_align;
   int32_t data_align = cie->data_align;
 
diff --git a/lldb/source/Symbol/FuncUnwinders.cpp b/lldb/source/Symbol/FuncUnwinders.cpp
index a74029d8343c7..11600825e8e38 100644
--- a/lldb/source/Symbol/FuncUnwinders.cpp
+++ b/lldb/source/Symbol/FuncUnwinders.cpp
@@ -537,39 +537,3 @@ FuncUnwinders::GetUnwindAssemblyProfiler(Target &target) {
   }
   return assembly_profiler_sp;
 }
-
-Address FuncUnwinders::GetLSDAAddress(Target &target) {
-  Address lsda_addr;
-
-  std::shared_ptr<const UnwindPlan> unwind_plan_sp =
-      GetEHFrameUnwindPlan(target);
-  if (unwind_plan_sp.get() == nullptr) {
-    unwind_plan_sp = GetCompactUnwindUnwindPlan(target);
-  }
-  if (unwind_plan_sp.get() == nullptr) {
-    unwind_plan_sp = GetObjectFileUnwindPlan(target);
-  }
-  if (unwind_plan_sp.get() && unwind_plan_sp->GetLSDAAddress().IsValid()) {
-    lsda_addr = unwind_plan_sp->GetLSDAAddress();
-  }
-  return lsda_addr;
-}
-
-Address FuncUnwinders::GetPersonalityRoutinePtrAddress(Target &target) {
-  Address personality_addr;
-
-  std::shared_ptr<const UnwindPlan> unwind_plan_sp =
-      GetEHFrameUnwindPlan(target);
-  if (unwind_plan_sp.get() == nullptr) {
-    unwind_plan_sp = GetCompactUnwindUnwindPlan(target);
-  }
-  if (unwind_plan_sp.get() == nullptr) {
-    unwind_plan_sp = GetObjectFileUnwindPlan(target);
-  }
-  if (unwind_plan_sp.get() &&
-      unwind_plan_sp->GetPersonalityFunctionPtr().IsValid()) {
-    personality_addr = unwind_plan_sp->GetPersonalityFunctionPtr();
-  }
-
-  return personality_addr;
-}
diff --git a/lldb/source/Symbol/UnwindPlan.cpp b/lldb/source/Symbol/UnwindPlan.cpp
index cfa8eefaa55bb..6690e558e0257 100644
--- a/lldb/source/Symbol/UnwindPlan.cpp
+++ b/lldb/source/Symbol/UnwindPlan.cpp
@@ -511,19 +511,6 @@ void UnwindPlan::Dump(Stream &s, Thread *thread, lldb::addr_t base_addr) const {
     s.Printf("This UnwindPlan originally sourced from %s\n",
              m_source_name.GetCString());
   }
-  if (m_lsda_address.IsValid() && m_personality_func_addr.IsValid()) {
-    TargetSP target_sp(thread->CalculateTarget());
-    addr_t lsda_load_addr = m_lsda_address.GetLoadAddress(target_sp.get());
-    addr_t personality_func_load_addr =
-        m_personality_func_addr.GetLoadAddress(target_sp.get());
-
-    if (lsda_load_addr != LLDB_INVALID_ADDRESS &&
-        personality_func_load_addr != LLDB_INVALID_ADDRESS) {
-      s.Printf("LSDA address 0x%" PRIx64
-               ", personality routine is at address 0x%" PRIx64 "\n",
-               lsda_load_addr, personality_func_load_addr);
-    }
-  }
   s.Printf("This UnwindPlan is sourced from the compiler: ");
   switch (m_plan_is_sourced_from_compiler) {
   case eLazyBoolYes:

[jasonmolenda]

Yeah I think these are only used by the actual libunwind functions that unwind the stack. I'm sure we were only saving the information because it was there, and who knows, maybe we'd need it for something. But we never have.