[Lldb-commits] [PATCH] D15877: Fix for undefined behavior while updating PC value on arm-linux

[Muhammad Omair Javaid via lldb-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL256847: Fix for undefined behavior while updating PC value on arm-linux (authored by omjavaid).

Changed prior to commit:
  http://reviews.llvm.org/D15877?vs=43941&id=44015#toc

Repository:
  rL LLVM

http://reviews.llvm.org/D15877

Files:
  lldb/trunk/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm.cpp

Index: lldb/trunk/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm.cpp
===================================================================
--- lldb/trunk/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm.cpp
+++ lldb/trunk/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm.cpp
@@ -973,7 +973,24 @@
     if (error.Fail())
         return error;
 
-    m_gpr_arm[offset / sizeof(uint32_t)] = value.GetAsUInt32();
+    uint32_t reg_value = value.GetAsUInt32();
+    // As precaution for an undefined behavior encountered while setting PC we
+    // will clear thumb bit of new PC if we are already in thumb mode; that is
+    // CPSR thumb mode bit is set.
+    if (offset / sizeof(uint32_t) == gpr_pc_arm)
+    {
+        // Check if we are already in thumb mode and
+        // thumb bit of current PC is read out to be zero and
+        // thumb bit of next PC is read out to be one.
+        if ((m_gpr_arm[gpr_cpsr_arm] &  0x20) &&
+            !(m_gpr_arm[gpr_pc_arm] &  0x01) &&
+            (value.GetAsUInt32() & 0x01))
+        {
+            reg_value &= (~1ull);
+        }
+    }
+
+    m_gpr_arm[offset / sizeof(uint32_t)] = reg_value;
     return DoWriteGPR(m_gpr_arm, sizeof(m_gpr_arm));
 }
 


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