Add support for .ARM.exidx unwind information

.ARM.exidx/.ARM.extab sections contain unwind information used on ARM
architecture from unwinding from an exception.

Differential revision: http://reviews.llvm.org/D13245

llvm-svn: 248903

1 files changed, 23 insertions, 8 deletions

diff --git a/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.cpp b/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.cpp
index 669db2f40ff..302f2034b94 100644
--- a/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.cpp
+++ b/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.cpp
@@ -17,6 +17,7 @@
 #include "lldb/Core/RegisterValue.h"
 #include "lldb/Core/Value.h"
 #include "lldb/Expression/DWARFExpression.h"
+#include "lldb/Symbol/ArmUnwindInfo.h"
 #include "lldb/Symbol/DWARFCallFrameInfo.h"
 #include "lldb/Symbol/FuncUnwinders.h"
 #include "lldb/Symbol/Function.h"
@@ -794,24 +795,38 @@ RegisterContextLLDB::GetFullUnwindPlanForFrame ()
         func_unwinders_sp = pc_module_sp->GetObjectFile()->GetUnwindTable().GetFuncUnwindersContainingAddress (m_current_pc, m_sym_ctx);
     }
 
-    // No FuncUnwinders available for this pc (i.e. a stripped function symbol and -fomit-frame-pointer).
-    // Try using the eh_frame information relative to the current PC,
-    // and finally fall back on the architectural default unwind.
+    // No FuncUnwinders available for this pc (stripped function symbols, lldb could not augment its
+    // function table with another source, like LC_FUNCTION_STARTS or eh_frame in ObjectFileMachO).
+    // See if eh_frame or the .ARM.exidx tables have unwind information for this address, else fall
+    // back to the architectural default unwind.
     if (!func_unwinders_sp)
     {
-        DWARFCallFrameInfo *eh_frame = pc_module_sp && pc_module_sp->GetObjectFile() ? 
-            pc_module_sp->GetObjectFile()->GetUnwindTable().GetEHFrameInfo() : nullptr;
-
         m_frame_type = eNormalFrame;
-        if (eh_frame && m_current_pc.IsValid())
+
+        if (!pc_module_sp || !pc_module_sp->GetObjectFile() || !m_current_pc.IsValid())
+            return arch_default_unwind_plan_sp;
+
+        // Even with -fomit-frame-pointer, we can try eh_frame to get back on track.
+        DWARFCallFrameInfo *eh_frame = pc_module_sp->GetObjectFile()->GetUnwindTable().GetEHFrameInfo();
+        if (eh_frame)
         {
             unwind_plan_sp.reset (new UnwindPlan (lldb::eRegisterKindGeneric));
-            // Even with -fomit-frame-pointer, we can try eh_frame to get back on track.
             if (eh_frame->GetUnwindPlan (m_current_pc, *unwind_plan_sp))
                 return unwind_plan_sp;
             else
                 unwind_plan_sp.reset();
         }
+
+        ArmUnwindInfo *arm_exidx = pc_module_sp->GetObjectFile()->GetUnwindTable().GetArmUnwindInfo();
+        if (arm_exidx)
+        {
+            unwind_plan_sp.reset (new UnwindPlan (lldb::eRegisterKindGeneric));
+            if (arm_exidx->GetUnwindPlan (exe_ctx.GetTargetRef(), m_current_pc, *unwind_plan_sp))
+                return unwind_plan_sp;
+            else
+                unwind_plan_sp.reset();
+        }
+
         return arch_default_unwind_plan_sp;
     }