Have the FuncUnwinder object request & provide an architecture-defined

UnwindPlan for unwinding from the first instruction of an otherwise
unknown function call (GetUnwindPlanArchitectureDefaultAtFunctionEntry()).

Update RegisterContextLLDB::GetFullUnwindPlanForFrame() to detect the
case of a frame 0 at address 0x0 which indicates that we jumped through
a NULL function pointer.  Use the ABI's FunctionEntryUnwindPlan to
find the caller frame.

These changes make it so lldb can identify the calling frame correctly
in code like

int main ()
{
  void (*f)(void) = 0;
  f();
}

llvm-svn: 139760

4 files changed, 16 insertions, 4 deletions

diff --git a/lldb/source/Plugins/ABI/MacOSX-arm/ABIMacOSX_arm.cpp b/lldb/source/Plugins/ABI/MacOSX-arm/ABIMacOSX_arm.cpp
index 03fa88ed93a..6035b051559 100644
--- a/lldb/source/Plugins/ABI/MacOSX-arm/ABIMacOSX_arm.cpp
+++ b/lldb/source/Plugins/ABI/MacOSX-arm/ABIMacOSX_arm.cpp
@@ -538,7 +538,7 @@ ABIMacOSX_arm::CreateFunctionEntryUnwindPlan (UnwindPlan &unwind_plan)
     
     // All other registers are the same.
     
-    unwind_plan.SetSourceName (pluginName);
+    unwind_plan.SetSourceName ("arm at-func-entry default");
     return true;
 }
 
diff --git a/lldb/source/Plugins/ABI/MacOSX-i386/ABIMacOSX_i386.cpp b/lldb/source/Plugins/ABI/MacOSX-i386/ABIMacOSX_i386.cpp
index 57593c9f4af..b356d774d4d 100644
--- a/lldb/source/Plugins/ABI/MacOSX-i386/ABIMacOSX_i386.cpp
+++ b/lldb/source/Plugins/ABI/MacOSX-i386/ABIMacOSX_i386.cpp
@@ -803,7 +803,7 @@ ABIMacOSX_i386::CreateFunctionEntryUnwindPlan (UnwindPlan &unwind_plan)
     row.SetCFAOffset (4);
     row.SetRegisterLocationToAtCFAPlusOffset(pc_reg_num, -4, false);    
     unwind_plan.AppendRow (row);
-    unwind_plan.SetSourceName (pluginName);
+    unwind_plan.SetSourceName ("i386 at-func-entry default");
     return true;
 }
 
diff --git a/lldb/source/Plugins/ABI/SysV-x86_64/ABISysV_x86_64.cpp b/lldb/source/Plugins/ABI/SysV-x86_64/ABISysV_x86_64.cpp
index 53437185bcf..f7f5c011828 100644
--- a/lldb/source/Plugins/ABI/SysV-x86_64/ABISysV_x86_64.cpp
+++ b/lldb/source/Plugins/ABI/SysV-x86_64/ABISysV_x86_64.cpp
@@ -661,7 +661,7 @@ ABISysV_x86_64::CreateFunctionEntryUnwindPlan (UnwindPlan &unwind_plan)
     row.SetCFAOffset (8);
     row.SetRegisterLocationToAtCFAPlusOffset(pc_reg_num, -8, false);    
     unwind_plan.AppendRow (row);
-    unwind_plan.SetSourceName (pluginName);
+    unwind_plan.SetSourceName ("x86_64 at-func-entry default");
     return true;
 }
 
diff --git a/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.cpp b/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.cpp
index 9759a66ec64..5a4e8b44d4a 100644
--- a/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.cpp
+++ b/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.cpp
@@ -552,7 +552,19 @@ RegisterContextLLDB::GetFullUnwindPlanForFrame ()
         m_all_registers_available = true;
     }
 
-    // No Module for the current pc, try using the architecture default unwind.
+    // If we've done a jmp 0x0 / bl 0x0 (called through a null function pointer) so the pc is 0x0
+    // in the zeroth frame, we need to use the "unwind at first instruction" arch default UnwindPlan
+    if (behaves_like_zeroth_frame 
+        && m_current_pc.IsValid() 
+        && m_current_pc.GetLoadAddress (&m_thread.GetProcess().GetTarget()) == 0)
+    {
+        unwind_plan_sp.reset (new UnwindPlan (lldb::eRegisterKindGeneric));
+        abi->CreateFunctionEntryUnwindPlan(*unwind_plan_sp);
+        m_frame_type = eNormalFrame;
+        return unwind_plan_sp;
+    }
+
+    // No Module fm_current_pc.GetLoadAddress (&m_thread.GetProcess().GetTarget()or the current pc, try using the architecture default unwind.
     if (!m_current_pc.IsValid() || m_current_pc.GetModule() == NULL || m_current_pc.GetModule()->GetObjectFile() == NULL)
     {
         m_frame_type = eNormalFrame;