[llvm-branch-commits] Add pointer field protection feature. (PR #133538)

[Oliver Hunt via llvm-branch-commits]

================
@@ -441,6 +445,254 @@ bool PreISelIntrinsicLowering::expandMemIntrinsicUses(Function &F) const {
   return Changed;
 }
 
+namespace {
+
+enum class PointerEncoding {
+  Rotate,
+  PACCopyable,
+  PACNonCopyable,
+};
+
+bool expandProtectedFieldPtr(Function &Intr) {
+  Module &M = *Intr.getParent();
+  bool IsAArch64 = Triple(M.getTargetTriple()).isAArch64();
+
+  std::set<Metadata *> NonPFPFields;
+  std::set<Instruction *> LoadsStores;
+
+  Type *Int8Ty = Type::getInt8Ty(M.getContext());
+  Type *Int64Ty = Type::getInt64Ty(M.getContext());
+  PointerType *PtrTy = PointerType::get(M.getContext(), 0);
+
+  Function *SignIntr =
+      Intrinsic::getOrInsertDeclaration(&M, Intrinsic::ptrauth_sign, {});
+  Function *AuthIntr =
+      Intrinsic::getOrInsertDeclaration(&M, Intrinsic::ptrauth_auth, {});
+
+  auto *EmuFnTy = FunctionType::get(Int64Ty, {Int64Ty, Int64Ty}, false);
+  FunctionCallee EmuSignIntr = M.getOrInsertFunction("__emupac_pacda", EmuFnTy);
+  FunctionCallee EmuAuthIntr = M.getOrInsertFunction("__emupac_autda", EmuFnTy);
+
+  auto CreateSign = [&](IRBuilder<> &B, Value *Val, Value *Disc,
+                       OperandBundleDef DSBundle) {
+    Function *F = B.GetInsertBlock()->getParent();
+    Attribute FSAttr = F->getFnAttribute("target-features");
+    if (FSAttr.isValid() && FSAttr.getValueAsString().contains("+pauth"))
+      return B.CreateCall(SignIntr, {Val, B.getInt32(2), Disc}, DSBundle);
+    return B.CreateCall(EmuSignIntr, {Val, Disc}, DSBundle);
+  };
+
+  auto CreateAuth = [&](IRBuilder<> &B, Value *Val, Value *Disc,
+                       OperandBundleDef DSBundle) {
+    Function *F = B.GetInsertBlock()->getParent();
+    Attribute FSAttr = F->getFnAttribute("target-features");
+    if (FSAttr.isValid() && FSAttr.getValueAsString().contains("+pauth"))
+      return B.CreateCall(AuthIntr, {Val, B.getInt32(2), Disc}, DSBundle);
+    return B.CreateCall(EmuAuthIntr, {Val, Disc}, DSBundle);
+  };
+
+  for (User *U : Intr.users()) {
+    auto *Call = cast<CallInst>(U);
+    auto *FieldName = cast<Metadata>(
----------------
ojhunt wrote:

I'm not really a backend person, but I feel that it's incorrect for the discriminator selection/computation to be occurring in llvm. I think clang should be passing the discriminator as a parameter to the intrinsics - this would also permit the PFP system to allow users to override the discriminator for fields, which is likely to end up being necessary, as time changes the exact types or naming of fields (side note: because I'm a muppet, I only just realized that the current model derives the discriminator from the name of the field which means the names of fields actually becomes ABI - it might be better to use something like "name of struct + offset in struct + type" though obviously that reduces the variation in discriminators - OTOH it's not uncommon for different projects to declare there own versions of POD structs with slightly different naming so maybe it helps there)

https://github.com/llvm/llvm-project/pull/133538