Disable MSan unpoisoning of memory writes

Prior to supporting MemorySanitizer instrumentation of Reactor routines, false positives in C++ code were avoided by marking all memory that was written to by the Reactor routines as unpoisoned. Now this can be disabled to avoid false negatives, i.e. uses of uninitialized data either in the Reactor routine or originating from it. REACTOR_ENABLE_MEMORY_SANITIZER_INSTRUMENTATION controls whether we get the new behavior or the old unpoisoning. Bug: b/155148722 Change-Id: Ia35e3cdc1a60ba44045869884c64e9875c030291 Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/49889 Kokoro-Result: kokoro <noreply+kokoro@google.com> Tested-by: Nicolas Capens <nicolascapens@google.com> Presubmit-Ready: Nicolas Capens <nicolascapens@google.com> Reviewed-by: Alexis Hétu <sugoi@google.com>

Disable MSan unpoisoning of memory writes
dc5bb219 · Nicolas Capens · Nicolas Capens · f890890f · dc5bb219 · dc5bb219
Commit dc5bb219 authored Nov 02, 2020 by Nicolas Capens Committed by Nicolas Capens Feb 18, 2021
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Showing with 12 additions and 4 deletions

LLVMJIT.cpp src/Reactor/LLVMJIT.cpp +10 -2

LLVMReactor.cpp src/Reactor/LLVMReactor.cpp +2 -2

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--- a/src/Reactor/LLVMJIT.cpp
+++ b/src/Reactor/LLVMJIT.cpp
@@ -54,7 +54,11 @@ extern "C" signed __aeabi_idivmod();
 #endif
 #if __has_feature(memory_sanitizer)
-#	include "sanitizer/msan_interface.h"  // TODO(b/155148722): Remove when we no longer unpoison all writes.
+// TODO(b/155148722): Remove when we no longer unpoison all writes.
+#	if !REACTOR_ENABLE_MEMORY_SANITIZER_INSTRUMENTATION
+#		include "sanitizer/msan_interface.h"
+#	endif
 #	include <dlfcn.h>  // dlsym()
@@ -540,7 +544,11 @@ class ExternalSymbolGenerator : public llvm::orc::JITDylib::DefinitionGenerator
 #	endif
 #endif
 #if __has_feature(memory_sanitizer)
-			functions.try_emplace("msan_unpoison", reinterpret_cast<void *>(__msan_unpoison));  // TODO(b/155148722): Remove when we no longer unpoison all writes.
+// TODO(b/155148722): Remove when we no longer unpoison all writes.
+#	if !REACTOR_ENABLE_MEMORY_SANITIZER_INSTRUMENTATION
+			functions.try_emplace("msan_unpoison", reinterpret_cast<void *>(__msan_unpoison));
+#	endif
 			functions.try_emplace("emutls_get_address", reinterpret_cast<void *>(rr::getTLSAddress));
 			functions.try_emplace("emutls_v.__msan_retval_tls", reinterpret_cast<void *>(static_cast<uintptr_t>(rr::MSanTLS::retval)));

--- a/src/Reactor/LLVMReactor.cpp
+++ b/src/Reactor/LLVMReactor.cpp
@@ -985,7 +985,7 @@ Value *Nucleus::createStore(Value *value, Value *ptr, Type *type, bool isVolatil
 			auto elTy = T(type);
 			ASSERT(V(ptr)->getType()->getContainedType(0) == elTy);
-			if(__has_feature(memory_sanitizer))
+			if(__has_feature(memory_sanitizer) && !REACTOR_ENABLE_MEMORY_SANITIZER_INSTRUMENTATION)
 			{
 				// Mark all memory writes as initialized by calling __msan_unpoison
 				// void __msan_unpoison(const volatile void *a, size_t size)
@@ -1091,7 +1091,7 @@ void Nucleus::createMaskedStore(Value *ptr, Value *val, Value *mask, unsigned in
 	auto func = llvm::Intrinsic::getDeclaration(jit->module.get(), llvm::Intrinsic::masked_store, { elVecTy, elVecPtrTy });
 	jit->builder->CreateCall(func, { V(val), V(ptr), align, i1Mask });
-	if(__has_feature(memory_sanitizer))
+	if(__has_feature(memory_sanitizer) && !REACTOR_ENABLE_MEMORY_SANITIZER_INSTRUMENTATION)
 	{
 		// Mark memory writes as initialized by calling __msan_unpoison
 		// void __msan_unpoison(const volatile void *a, size_t size)