commit 5bd669dc8fcd7bb28909493744463da47808a0f8
author Evgeniy Stepanov <eugeni.stepanov@gmail.com> Wed Jan 17 23:24:38 2018 +0000
committer Evgeniy Stepanov <eugeni.stepanov@gmail.com> Wed Jan 17 23:24:38 2018 +0000
tree 82598c349b0708de14618dcce14936ba0e0a87c0
parent fd2833992a93f0bb4f3ca535ddda8f600b722926

[hwasan] LLVM-level flags for linux kernel-compatible hwasan instrumentation.

Summary:
-hwasan-mapping-offset defines the non-zero shadow base address.
-hwasan-kernel disables calls to __hwasan_init in module constructors.
Unlike ASan, -hwasan-kernel does not force callback instrumentation.
This is controlled separately with -hwasan-instrument-with-calls.

Reviewers: kcc

Subscribers: srhines, hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D42141

llvm-svn: 322785

llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp

diff --git a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
index 3da9fe7..15d97b3 100644
--- a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
@@ -96,6 +96,15 @@
     cl::desc("generate new tags with runtime library calls"), cl::Hidden,
     cl::init(false));
 
+static cl::opt<unsigned long long> ClMappingOffset(
+    "hwasan-mapping-offset",
+    cl::desc("offset of hwasan shadow mapping [EXPERIMENTAL]"), cl::Hidden,
+    cl::init(0));
+
+static cl::opt<bool> ClEnableKhwasan(
+    "hwasan-kernel", cl::desc("Enable KernelHWAddressSanitizer instrumentation"),
+    cl::Hidden, cl::init(false));
+
 namespace {
 
 /// \brief An instrumentation pass implementing detection of addressability bugs
@@ -177,12 +186,14 @@
   IntptrTy = IRB.getIntPtrTy(DL);
   Int8Ty = IRB.getInt8Ty();
 
-  std::tie(HwasanCtorFunction, std::ignore) =
-      createSanitizerCtorAndInitFunctions(M, kHwasanModuleCtorName,
-                                          kHwasanInitName,
-                                          /*InitArgTypes=*/{},
-                                          /*InitArgs=*/{});
-  appendToGlobalCtors(M, HwasanCtorFunction, 0);
+  if (!ClEnableKhwasan) {
+    std::tie(HwasanCtorFunction, std::ignore) =
+        createSanitizerCtorAndInitFunctions(M, kHwasanModuleCtorName,
+                                            kHwasanInitName,
+                                            /*InitArgTypes=*/{},
+                                            /*InitArgs=*/{});
+    appendToGlobalCtors(M, HwasanCtorFunction, 0);
+  }
   return true;
 }
 
@@ -282,7 +293,12 @@
       IRB.CreateAnd(PtrLong, ConstantInt::get(PtrLong->getType(),
                                               ~(0xFFULL << kPointerTagShift)));
   Value *ShadowLong = IRB.CreateLShr(AddrLong, kShadowScale);
-  Value *MemTag = IRB.CreateLoad(IRB.CreateIntToPtr(ShadowLong, IRB.getInt8PtrTy()));
+  if (ClMappingOffset)
+    ShadowLong = IRB.CreateAdd(
+        ShadowLong, ConstantInt::get(PtrLong->getType(), ClMappingOffset,
+                                     /*isSigned=*/false));
+  Value *MemTag =
+      IRB.CreateLoad(IRB.CreateIntToPtr(ShadowLong, IRB.getInt8PtrTy()));
   Value *TagMismatch = IRB.CreateICmpNE(PtrTag, MemTag);
 
   TerminatorInst *CheckTerm =