[Lldb-commits] [lldb] r222301 - Add additional checks to the SavedLocationForRegister method

[Jason Molenda]

Author: jmolenda
Date: Tue Nov 18 20:29:52 2014
New Revision: 222301

URL: http://llvm.org/viewvc/llvm-project?rev=222301&view=rev
Log:
Add additional checks to the SavedLocationForRegister method
where it is retrieving the Return Address register contents
on a target where that's a thing.  If we fail to get a valid
RA, we force a switch to the fallback unwind plan.  This patch
adds a sanity check for that fallback unwind plan -- it must
get a valid CFA for this frame in addition to being able to
retrieve the caller's PC -- and it correctly marks the unwind
rules as failing if the fallback unwind plan fails.

<rdar://problem/19010211> 

Modified:
    lldb/trunk/source/Plugins/Process/Utility/RegisterContextLLDB.cpp

Modified: lldb/trunk/source/Plugins/Process/Utility/RegisterContextLLDB.cpp
URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Plugins/Process/Utility/RegisterContextLLDB.cpp?rev=222301&r1=222300&r2=222301&view=diff
==============================================================================
--- lldb/trunk/source/Plugins/Process/Utility/RegisterContextLLDB.cpp (original)
+++ lldb/trunk/source/Plugins/Process/Utility/RegisterContextLLDB.cpp Tue Nov 18 20:29:52 2014
@@ -1267,12 +1267,30 @@ RegisterContextLLDB::SavedLocationForReg
                 // Throw away the full unwindplan; install the arch default unwindplan
                 if (ForceSwitchToFallbackUnwindPlan())
                 {
-                    // Now re-fetch the pc value we're searching for
-                    RegisterNumber arch_default_pc_reg (m_thread, eRegisterKindGeneric, LLDB_REGNUM_GENERIC_PC);
+                    // Update for the possibly new unwind plan
+                    unwindplan_registerkind = m_full_unwind_plan_sp->GetRegisterKind ();
                     UnwindPlan::RowSP active_row = m_full_unwind_plan_sp->GetRowForFunctionOffset (m_current_offset);
-                    if (arch_default_pc_reg.GetAsKind (unwindplan_registerkind) != LLDB_INVALID_REGNUM
-                        && active_row
-                        && active_row->GetRegisterInfo (arch_default_pc_reg.GetAsKind (unwindplan_registerkind), unwindplan_regloc))
+
+                    // Sanity check: Verify that we can fetch a pc value and CFA value with this unwind plan
+
+                    RegisterNumber arch_default_pc_reg (m_thread, eRegisterKindGeneric, LLDB_REGNUM_GENERIC_PC);
+                    bool can_fetch_pc_value = false;
+                    bool can_fetch_cfa = false;
+                    addr_t cfa_value;
+                    if (active_row)
+                    {
+                        if (arch_default_pc_reg.GetAsKind (unwindplan_registerkind) != LLDB_INVALID_REGNUM
+                            && active_row->GetRegisterInfo (arch_default_pc_reg.GetAsKind (unwindplan_registerkind), unwindplan_regloc))
+                        {
+                            can_fetch_pc_value = true;
+                        }
+                        if (ReadCFAValueForRow (unwindplan_registerkind, active_row, cfa_value))
+                        {
+                            can_fetch_cfa = true;
+                        }
+                    }
+
+                    if (can_fetch_pc_value && can_fetch_cfa)
                     {
                         have_unwindplan_regloc = true;
                     }
@@ -1281,6 +1299,11 @@ RegisterContextLLDB::SavedLocationForReg
                         have_unwindplan_regloc = false;
                     }
                 }
+                else
+                {
+                    // We were unable to fall back to another unwind plan
+                    have_unwindplan_regloc = false;
+                }
             }
         }
     }