[PATCH] D119296: KCFI sanitizer

[Peter Collingbourne via Phabricator via cfe-commits]

pcc added inline comments.


================
Comment at: clang/lib/CodeGen/CGExpr.cpp:3168
+      -1);
+  llvm::Value *Test = Builder.CreateICmpEQ(Builder.CreateLoad(HashPtr), Hash);
+  llvm::BasicBlock *ContBB = createBasicBlock("kcfi.cont");
----------------
We considered a scheme like this before and one problem that we discovered with comparing the hash in this way is that it can produce gadgets, e.g.
```
movabs $0x0123456789abcdef, %rax
cmp %rax, ...
```
the `cmp`instruction ends up being a valid target address because the `movabs` instruction ends in the hash. The way we thought about solving this was to introduce a new intrinsic that would materialize the constant without these gadgets (e.g. invert the `movabs` operand and follow it by a `not`).


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D119296/new/

https://reviews.llvm.org/D119296