Add LLVM CFI support to the Rust compiler

This commit adds LLVM Control Flow Integrity (CFI) support to the Rust
compiler. It initially provides forward-edge control flow protection for
Rust-compiled code only by aggregating function pointers in groups
identified by their number of arguments.

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 defining and using compatible type identifiers
(see Type metadata in the design document in the tracking issue #89653).

LLVM CFI can be enabled with -Zsanitizer=cfi and requires LTO (i.e.,
-Clto).

2 files changed, 4 insertions, 0 deletions

diff --git a/compiler/rustc_codegen_ssa/src/traits/builder.rs b/compiler/rustc_codegen_ssa/src/traits/builder.rs
index e7da96f0ada..158e658301e 100644
--- a/compiler/rustc_codegen_ssa/src/traits/builder.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/builder.rs
@@ -158,6 +158,8 @@ pub trait BuilderMethods<'a, 'tcx>:
 
     fn range_metadata(&mut self, load: Self::Value, range: WrappingRange);
     fn nonnull_metadata(&mut self, load: Self::Value);
+    fn type_metadata(&mut self, function: Self::Function, typeid: String);
+    fn typeid_metadata(&mut self, typeid: String) -> Self::Value;
 
     fn store(&mut self, val: Self::Value, ptr: Self::Value, align: Align) -> Self::Value;
     fn store_with_flags(
diff --git a/compiler/rustc_codegen_ssa/src/traits/intrinsic.rs b/compiler/rustc_codegen_ssa/src/traits/intrinsic.rs
index 777436ad2ae..78bf22ef9f2 100644
--- a/compiler/rustc_codegen_ssa/src/traits/intrinsic.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/intrinsic.rs
@@ -24,6 +24,8 @@ pub trait IntrinsicCallMethods<'tcx>: BackendTypes {
     ///
     /// Currently has any effect only when LLVM versions prior to 12.0 are used as the backend.
     fn sideeffect(&mut self);
+    /// Trait method used to test whether a given pointer is associated with a type identifier.
+    fn type_test(&mut self, pointer: Self::Value, typeid: Self::Value) -> Self::Value;
     /// Trait method used to inject `va_start` on the "spoofed" `VaListImpl` in
     /// Rust defined C-variadic functions.
     fn va_start(&mut self, val: Self::Value) -> Self::Value;