RhpUniversalTransition improvements

[tfs-changeset: 1562851]

1 files changed, 69 insertions, 0 deletions

diff --git a/src/Native/Runtime/UniversalTransitionHelpers.cpp b/src/Native/Runtime/UniversalTransitionHelpers.cpp
new file mode 100644
index 000000000..1c423b379
--- /dev/null
+++ b/src/Native/Runtime/UniversalTransitionHelpers.cpp
@@ -0,0 +1,69 @@
+//
+// Copyright (c) Microsoft Corporation.  All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+#include "common.h"
+#include "CommonTypes.h"
+#include "CommonMacros.h"
+#include "PalRedhawkCommon.h"
+#include "PalRedhawk.h"
+
+#ifdef _DEBUG
+#define TRASH_SAVED_ARGUMENT_REGISTERS
+#endif
+
+#ifdef TRASH_SAVED_ARGUMENT_REGISTERS
+
+//
+// Define tables of predictable distinguished values that RhpUniversalTransition can use to
+// trash argument registers after they have been saved into the transition frame.
+//
+// Trashing these registers is a testability aid that makes it easier to detect bugs where
+// the transition frame content is not correctly propagated to the eventual callee.
+//
+// In the absence of trashing, such bugs can become undetectable if the code that
+// dispatches the call happens to never touch the impacted argument register (e.g., xmm3 on
+// amd64 or d5 on arm32). In such a case, the original enregistered argument will flow
+// unmodified into the eventual callee, obscuring the fact that the dispatcher failed to
+// propagate the transition frame copy of this register.
+//
+// These tables are manually aligned as a conservative safeguard to ensure that the
+// consumers can use arbitrary access widths without ever needing to worry about alignment.
+// The comments in each table show the %d/%f renderings of each 32-bit value, plus the
+// %I64d/%f rendering of the combined 64-bit value of each aligned pair of 32-bit values.
+//
+
+#define TRASH_VALUE_ALIGNMENT 16
+
+EXTERN_C
+DECLSPEC_ALIGN(TRASH_VALUE_ALIGNMENT)
+const UInt32 RhpIntegerTrashValues[] = {
+ // Lo32         Hi32               Lo32       Hi32        Hi32:Lo32
+ // -----------  -----------        ---------  ---------   ------------------
+    0x07801001U, 0x07802002U,   // (125833217, 125837314) (540467148372316161)
+    0x07803003U, 0x07804004U,   // (125841411, 125845508) (540502341334347779)
+    0x07805005U, 0x07806006U,   // (125849605, 125853702) (540537534296379397)
+    0x07807007U, 0x07808008U,   // (125857799, 125861896) (540572727258411015)
+    0x07809009U, 0x0780a00aU,   // (125865993, 125870090) (540607920220442633)
+    0x0780b00bU, 0x0780c00cU,   // (125874187, 125878284) (540643113182474251)
+    0x0780d00dU, 0x0780e00eU,   // (125882381, 125886478) (540678306144505869)
+    0x0780f00fU, 0x07810010U,   // (125890575, 125894672) (540713499106537487)
+};
+
+EXTERN_C
+DECLSPEC_ALIGN(TRASH_VALUE_ALIGNMENT)
+const UInt32 RhpFpTrashValues[] = {
+ // Lo32         Hi32               Lo32                 Hi32                  Hi32:Lo32
+ // -----------  -----------        -------------------  -------------------   -------------------
+    0x42001001U, 0x42002002U,   // (32.0156288146972660, 32.0312576293945310) (8657061952.00781440)
+    0x42003003U, 0x42004004U,   // (32.0468864440917970, 32.0625152587890630) (8724187200.02344320)
+    0x42005005U, 0x42006006U,   // (32.0781440734863280, 32.0937728881835940) (8791312448.03907200)
+    0x42007007U, 0x42008008U,   // (32.1094017028808590, 32.1250305175781250) (8858437696.05470090)
+    0x42009009U, 0x4200a00aU,   // (32.1406593322753910, 32.1562881469726560) (8925562944.07032970)
+    0x4200b00bU, 0x4200c00cU,   // (32.1719169616699220, 32.1875457763671880) (8992688192.08595850)
+    0x4200d00dU, 0x4200e00eU,   // (32.2031745910644530, 32.2188034057617190) (9059813440.10158730)
+    0x4200f00fU, 0x42010010U,   // (32.2344322204589840, 32.2500610351562500) (9126938688.11721610)
+};
+
+#endif // TRASH_SAVED_ARGUMENT_REGISTERS
+