Add LLVM KCFI support to the Rust compiler

This commit adds LLVM Kernel Control Flow Integrity (KCFI) support to
the Rust compiler. It initially provides forward-edge control flow
protection for operating systems kernels for Rust-compiled code only by
aggregating function pointers in groups identified by their return and
parameter types. (See llvm/llvm-project@cff5bef.)

Forward-edge control flow protection for C or C++ and Rust -compiled
code "mixed binaries" (i.e., for when C or C++ and Rust -compiled code
share the same virtual address space) will be provided in later work as
part of this project by identifying C char and integer type uses at the
time types are encoded (see Type metadata in the design document in the
tracking issue #89653).

LLVM KCFI can be enabled with -Zsanitizer=kcfi.

Co-authored-by: bjorn3 <17426603+bjorn3@users.noreply.github.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/compiler/rustc_codegen_llvm/src/declare.rs b/compiler/rustc_codegen_llvm/src/declare.rs
index dc21a02cec4..6a575095f7e 100644
--- a/compiler/rustc_codegen_llvm/src/declare.rs
+++ b/compiler/rustc_codegen_llvm/src/declare.rs
@@ -20,7 +20,7 @@ use crate::type_::Type;
 use crate::value::Value;
 use rustc_codegen_ssa::traits::TypeMembershipMethods;
 use rustc_middle::ty::Ty;
-use rustc_symbol_mangling::typeid::typeid_for_fnabi;
+use rustc_symbol_mangling::typeid::{kcfi_typeid_for_fnabi, typeid_for_fnabi};
 use smallvec::SmallVec;
 
 /// Declare a function.
@@ -136,6 +136,11 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
             self.set_type_metadata(llfn, typeid);
         }
 
+        if self.tcx.sess.is_sanitizer_kcfi_enabled() {
+            let kcfi_typeid = kcfi_typeid_for_fnabi(self.tcx, fn_abi);
+            self.set_kcfi_type_metadata(llfn, kcfi_typeid);
+        }
+
         llfn
     }