[PATCH] D100546: [ARM][AArch64] SLSHardening: make non-comdat thunks possible

[Daniel Kiss via Phabricator via llvm-commits]

danielkiss created this revision.
danielkiss added reviewers: kristof.beyls, srhines.
Herald added a subscriber: hiraditya.
danielkiss requested review of this revision.
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Herald added a subscriber: llvm-commits.

Linker scripts might not handle COMDAT sections. SLSHardeing adds
new section for each __llvm_slsblr_thunk_xN. This new hidden option allows
the generation of the thunk into the normal text section to handle these
exceptional cases.


https://reviews.llvm.org/D100546

Files:
  llvm/include/llvm/CodeGen/IndirectThunks.h
  llvm/lib/Target/AArch64/AArch64SLSHardening.cpp
  llvm/lib/Target/ARM/ARMSLSHardening.cpp


Index: llvm/lib/Target/ARM/ARMSLSHardening.cpp
===================================================================
--- llvm/lib/Target/ARM/ARMSLSHardening.cpp
+++ llvm/lib/Target/ARM/ARMSLSHardening.cpp
@@ -30,6 +30,11 @@
 
 #define ARM_SLS_HARDENING_NAME "ARM sls hardening pass"
 
+static cl::opt<bool>
+    ComdatThunks("arm-sls-hardening-comdat",
+                 cl::desc("Output SLS hardening thunks in comdats"),
+                 cl::init(true), cl::Hidden);
+
 namespace {
 
 class ARMSLSHardening : public MachineFunctionPass {
@@ -179,7 +184,7 @@
   // based on which registers are actually used in indirect calls in this
   // function. But would that be a worthwhile optimization?
   for (auto T : SLSBLRThunks)
-    createThunkFunction(MMI, T.Name);
+    createThunkFunction(MMI, T.Name, ComdatThunks);
 }
 
 void SLSBLRThunkInserter::populateThunk(MachineFunction &MF) {
Index: llvm/lib/Target/AArch64/AArch64SLSHardening.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64SLSHardening.cpp
+++ llvm/lib/Target/AArch64/AArch64SLSHardening.cpp
@@ -38,6 +38,10 @@
 
 #define AARCH64_SLS_HARDENING_NAME "AArch64 sls hardening pass"
 
+static cl::opt<bool>
+    ComdatThunks("aarch64-sls-hardening-comdat",
+                 cl::desc("Output SLS hardening thunks in comdats"),
+                 cl::init(true), cl::Hidden);
 namespace {
 
 class AArch64SLSHardening : public MachineFunctionPass {
@@ -200,7 +204,7 @@
   // based on which registers are actually used in BLR instructions in this
   // function. But would that be a worthwhile optimization?
   for (auto T : SLSBLRThunks)
-    createThunkFunction(MMI, T.Name);
+    createThunkFunction(MMI, T.Name, ComdatThunks);
 }
 
 void SLSBLRThunkInserter::populateThunk(MachineFunction &MF) {
Index: llvm/include/llvm/CodeGen/IndirectThunks.h
===================================================================
--- llvm/include/llvm/CodeGen/IndirectThunks.h
+++ llvm/include/llvm/CodeGen/IndirectThunks.h
@@ -27,7 +27,8 @@
 protected:
   bool InsertedThunks;
   void doInitialization(Module &M) {}
-  void createThunkFunction(MachineModuleInfo &MMI, StringRef Name);
+  void createThunkFunction(MachineModuleInfo &MMI, StringRef Name,
+                           bool Comdat = true);
 
 public:
   void init(Module &M) {
@@ -40,17 +41,21 @@
 
 template <typename Derived>
 void ThunkInserter<Derived>::createThunkFunction(MachineModuleInfo &MMI,
-                                                 StringRef Name) {
+                                                 StringRef Name, bool Comdat) {
   assert(Name.startswith(getDerived().getThunkPrefix()) &&
          "Created a thunk with an unexpected prefix!");
 
   Module &M = const_cast<Module &>(*MMI.getModule());
   LLVMContext &Ctx = M.getContext();
   auto Type = FunctionType::get(Type::getVoidTy(Ctx), false);
-  Function *F =
-      Function::Create(Type, GlobalValue::LinkOnceODRLinkage, Name, &M);
-  F->setVisibility(GlobalValue::HiddenVisibility);
-  F->setComdat(M.getOrInsertComdat(Name));
+  Function *F = Function::Create(Type,
+                                 Comdat ? GlobalValue::LinkOnceODRLinkage
+                                        : GlobalValue::InternalLinkage,
+                                 Name, &M);
+  if (Comdat) {
+    F->setVisibility(GlobalValue::HiddenVisibility);
+    F->setComdat(M.getOrInsertComdat(Name));
+  }
 
   // Add Attributes so that we don't create a frame, unwind information, or
   // inline.


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