Fix alignment issue when converting to/from native context.

When building in release mode, the code in CONTEXTFromNativeContext and
CONTEXTToNativeContext was using the movaps instruction to move the float
and XMM register values to/from the native context. This is because the
macros FPREG_St and FPREG_Xmm were casting unaligned pointers to an
aligned struct type (M128A). This change adds a type M128U which is the
same as M128A but without the alignment guarantee. Using this type in
those macros prevents the compiler from trying to use movaps on
potentially unaligned memory. This bug manifested when trying to call
these functions with native contexts that were passed into a real-time
signal handler.

1 files changed, 6 insertions, 6 deletions

diff --git a/src/pal/src/arch/i386/context.cpp b/src/pal/src/arch/i386/context.cpp
index d749f874bb..14a96bb9b0 100644
--- a/src/pal/src/arch/i386/context.cpp
+++ b/src/pal/src/arch/i386/context.cpp
@@ -402,13 +402,13 @@ void CONTEXTToNativeContext(CONST CONTEXT *lpContext, native_context_t *native)
 
         for (int i = 0; i < 8; i++)
         {
-            FPREG_St(native, i) = lpContext->FltSave.FloatRegisters[i];
+            FPREG_St(native, i) = ((M128U*)lpContext->FltSave.FloatRegisters)[i];
         }
 
         for (int i = 0; i < 16; i++)
         {
-            FPREG_Xmm(native, i) = lpContext->FltSave.XmmRegisters[i];
-        }        
+            FPREG_Xmm(native, i) = ((M128U*)lpContext->FltSave.XmmRegisters)[i];
+        }
     }
 }
 
@@ -459,13 +459,13 @@ void CONTEXTFromNativeContext(const native_context_t *native, LPCONTEXT lpContex
 
         for (int i = 0; i < 8; i++)
         {
-            lpContext->FltSave.FloatRegisters[i] = FPREG_St(native, i);
+            ((M128U*)lpContext->FltSave.FloatRegisters)[i] = FPREG_St(native, i);
         }
 
         for (int i = 0; i < 16; i++)
         {
-            lpContext->FltSave.XmmRegisters[i] = FPREG_Xmm(native, i);
-        }        
+            ((M128U*)lpContext->FltSave.XmmRegisters)[i] = FPREG_Xmm(native, i);
+        }
     }
 }