Rollup merge of #105109 - rcvalle:rust-kcfi, r=bjorn3

Add LLVM KCFI support to the Rust compiler

This PR 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.

Thank you again, `@bjorn3,` `@eddyb,` `@nagisa,` and `@ojeda,` for all the help!

Author: matthiaskrgr

Cargo.lock

@@ -4403,6 +4403,7 @@ dependencies = [
  "rustc_span",
  "rustc_target",
  "tracing",
+ "twox-hash",
 ]
 
 [[package]]
@@ -5393,6 +5394,17 @@ dependencies = [
  "tracing-subscriber",
 ]
 
+[[package]]
+name = "twox-hash"
+version = "1.6.3"
+source = "registry+https://github.com./rust-lang/crates.io-index"
+checksum = "97fee6b57c6a41524a810daee9286c02d7752c4253064d0b05472833a438f675"
+dependencies = [
+ "cfg-if 1.0.0",
+ "rand 0.8.5",
+ "static_assertions",
+]
+
 [[package]]
 name = "type-map"
 version = "0.4.0"

compiler/rustc_codegen_gcc/src/type_.rs

@@ -300,4 +300,8 @@ impl<'gcc, 'tcx> TypeMembershipMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
         // Unsupported.
         self.context.new_rvalue_from_int(self.int_type, 0)
     }
+
+    fn set_kcfi_type_metadata(&self, _function: RValue<'gcc>, _kcfi_typeid: u32) {
+        // Unsupported.
+    }
 }

compiler/rustc_codegen_llvm/src/allocator.rs

@@ -88,7 +88,8 @@ pub(crate) unsafe fn codegen(
             callee,
             args.as_ptr(),
             args.len() as c_uint,
-            None,
+            [].as_ptr(),
+            0 as c_uint,
         );
         llvm::LLVMSetTailCall(ret, True);
         if output.is_some() {
@@ -132,8 +133,15 @@ pub(crate) unsafe fn codegen(
         .enumerate()
         .map(|(i, _)| llvm::LLVMGetParam(llfn, i as c_uint))
         .collect::<Vec<_>>();
-    let ret =
-        llvm::LLVMRustBuildCall(llbuilder, ty, callee, args.as_ptr(), args.len() as c_uint, None);
+    let ret = llvm::LLVMRustBuildCall(
+        llbuilder,
+        ty,
+        callee,
+        args.as_ptr(),
+        args.len() as c_uint,
+        [].as_ptr(),
+        0 as c_uint,
+    );
     llvm::LLVMSetTailCall(ret, True);
     llvm::LLVMBuildRetVoid(llbuilder);
     llvm::LLVMDisposeBuilder(llbuilder);

compiler/rustc_codegen_llvm/src/builder.rs

@@ -20,6 +20,7 @@ use rustc_middle::ty::layout::{
 };
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::Span;
+use rustc_symbol_mangling::typeid::kcfi_typeid_for_fnabi;
 use rustc_target::abi::{self, call::FnAbi, Align, Size, WrappingRange};
 use rustc_target::spec::{HasTargetSpec, Target};
 use std::borrow::Cow;
@@ -225,9 +226,25 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         debug!("invoke {:?} with args ({:?})", llfn, args);
 
         let args = self.check_call("invoke", llty, llfn, args);
-        let bundle = funclet.map(|funclet| funclet.bundle());
-        let bundle = bundle.as_ref().map(|b| &*b.raw);
+        let funclet_bundle = funclet.map(|funclet| funclet.bundle());
+        let funclet_bundle = funclet_bundle.as_ref().map(|b| &*b.raw);
+        let mut bundles = vec![funclet_bundle];
+
+        // Set KCFI operand bundle
+        let is_indirect_call = unsafe { llvm::LLVMIsAFunction(llfn).is_none() };
+        let kcfi_bundle =
+            if self.tcx.sess.is_sanitizer_kcfi_enabled() && fn_abi.is_some() && is_indirect_call {
+                let kcfi_typeid = kcfi_typeid_for_fnabi(self.tcx, fn_abi.unwrap());
+                Some(llvm::OperandBundleDef::new("kcfi", &[self.const_u32(kcfi_typeid)]))
+            } else {
+                None
+            };
+        if kcfi_bundle.is_some() {
+            let kcfi_bundle = kcfi_bundle.as_ref().map(|b| &*b.raw);
+            bundles.push(kcfi_bundle);
+        }
 
+        bundles.retain(|bundle| bundle.is_some());
         let invoke = unsafe {
             llvm::LLVMRustBuildInvoke(
                 self.llbuilder,
@@ -237,7 +254,8 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 args.len() as c_uint,
                 then,
                 catch,
-                bundle,
+                bundles.as_ptr(),
+                bundles.len() as c_uint,
                 UNNAMED,
             )
         };
@@ -1143,7 +1161,8 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 llfn,
                 args.as_ptr() as *const &llvm::Value,
                 args.len() as c_uint,
-                None,
+                [].as_ptr(),
+                0 as c_uint,
             );
         }
     }
@@ -1159,17 +1178,34 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         debug!("call {:?} with args ({:?})", llfn, args);
 
         let args = self.check_call("call", llty, llfn, args);
-        let bundle = funclet.map(|funclet| funclet.bundle());
-        let bundle = bundle.as_ref().map(|b| &*b.raw);
+        let funclet_bundle = funclet.map(|funclet| funclet.bundle());
+        let funclet_bundle = funclet_bundle.as_ref().map(|b| &*b.raw);
+        let mut bundles = vec![funclet_bundle];
+
+        // Set KCFI operand bundle
+        let is_indirect_call = unsafe { llvm::LLVMIsAFunction(llfn).is_none() };
+        let kcfi_bundle =
+            if self.tcx.sess.is_sanitizer_kcfi_enabled() && fn_abi.is_some() && is_indirect_call {
+                let kcfi_typeid = kcfi_typeid_for_fnabi(self.tcx, fn_abi.unwrap());
+                Some(llvm::OperandBundleDef::new("kcfi", &[self.const_u32(kcfi_typeid)]))
+            } else {
+                None
+            };
+        if kcfi_bundle.is_some() {
+            let kcfi_bundle = kcfi_bundle.as_ref().map(|b| &*b.raw);
+            bundles.push(kcfi_bundle);
+        }
 
+        bundles.retain(|bundle| bundle.is_some());
         let call = unsafe {
             llvm::LLVMRustBuildCall(
                 self.llbuilder,
                 llty,
                 llfn,
                 args.as_ptr() as *const &llvm::Value,
                 args.len() as c_uint,
-                bundle,
+                bundles.as_ptr(),
+                bundles.len() as c_uint,
             )
         };
         if let Some(fn_abi) = fn_abi {

compiler/rustc_codegen_llvm/src/context.rs

@@ -250,6 +250,11 @@ pub unsafe fn create_module<'ll>(
         );
     }
 
+    if sess.is_sanitizer_kcfi_enabled() {
+        let kcfi = "kcfi\0".as_ptr().cast();
+        llvm::LLVMRustAddModuleFlag(llmod, llvm::LLVMModFlagBehavior::Override, kcfi, 1);
+    }
+
     // Control Flow Guard is currently only supported by the MSVC linker on Windows.
     if sess.target.is_like_msvc {
         match sess.opts.cg.control_flow_guard {

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
     }
 

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -427,6 +427,7 @@ pub enum MetadataType {
     MD_type = 19,
     MD_vcall_visibility = 28,
     MD_noundef = 29,
+    MD_kcfi_type = 36,
 }
 
 /// LLVMRustAsmDialect
@@ -1063,6 +1064,7 @@ extern "C" {
     pub fn LLVMGlobalSetMetadata<'a>(Val: &'a Value, KindID: c_uint, Metadata: &'a Metadata);
     pub fn LLVMRustGlobalAddMetadata<'a>(Val: &'a Value, KindID: c_uint, Metadata: &'a Metadata);
     pub fn LLVMValueAsMetadata(Node: &Value) -> &Metadata;
+    pub fn LLVMIsAFunction(Val: &Value) -> Option<&Value>;
 
     // Operations on constants of any type
     pub fn LLVMConstNull(Ty: &Type) -> &Value;
@@ -1273,7 +1275,8 @@ extern "C" {
         NumArgs: c_uint,
         Then: &'a BasicBlock,
         Catch: &'a BasicBlock,
-        Bundle: Option<&OperandBundleDef<'a>>,
+        OpBundles: *const Option<&OperandBundleDef<'a>>,
+        NumOpBundles: c_uint,
         Name: *const c_char,
     ) -> &'a Value;
     pub fn LLVMBuildLandingPad<'a>(
@@ -1643,7 +1646,8 @@ extern "C" {
         Fn: &'a Value,
         Args: *const &'a Value,
         NumArgs: c_uint,
-        Bundle: Option<&OperandBundleDef<'a>>,
+        OpBundles: *const Option<&OperandBundleDef<'a>>,
+        NumOpBundles: c_uint,
     ) -> &'a Value;
     pub fn LLVMRustBuildMemCpy<'a>(
         B: &Builder<'a>,

compiler/rustc_codegen_llvm/src/type_.rs

@@ -316,4 +316,19 @@ impl<'ll, 'tcx> TypeMembershipMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             )
         }
     }
+
+    fn set_kcfi_type_metadata(&self, function: &'ll Value, kcfi_typeid: u32) {
+        let kcfi_type_metadata = self.const_u32(kcfi_typeid);
+        unsafe {
+            llvm::LLVMGlobalSetMetadata(
+                function,
+                llvm::MD_kcfi_type as c_uint,
+                llvm::LLVMMDNodeInContext2(
+                    self.llcx,
+                    &llvm::LLVMValueAsMetadata(kcfi_type_metadata),
+                    1,
+                ),
+            )
+        }
+    }
 }

compiler/rustc_codegen_ssa/src/traits/type_.rs

@@ -122,6 +122,7 @@ pub trait LayoutTypeMethods<'tcx>: Backend<'tcx> {
 pub trait TypeMembershipMethods<'tcx>: Backend<'tcx> {
     fn set_type_metadata(&self, function: Self::Function, typeid: String);
     fn typeid_metadata(&self, typeid: String) -> Self::Value;
+    fn set_kcfi_type_metadata(&self, function: Self::Function, typeid: u32);
 }
 
 pub trait ArgAbiMethods<'tcx>: HasCodegen<'tcx> {

compiler/rustc_feature/src/builtin_attrs.rs

@@ -394,7 +394,7 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
     ungated!(instruction_set, Normal, template!(List: "set"), ErrorPreceding),
     gated!(
         no_sanitize, Normal,
-        template!(List: "address, memory, thread"), DuplicatesOk,
+        template!(List: "address, kcfi, memory, thread"), DuplicatesOk,
         experimental!(no_sanitize)
     ),
     gated!(no_coverage, Normal, template!(Word), WarnFollowing, experimental!(no_coverage)),

compiler/rustc_hir_analysis/src/collect.rs

@@ -1846,6 +1846,8 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: DefId) -> CodegenFnAttrs {
                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
                     } else if item.has_name(sym::cfi) {
                         codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI;
+                    } else if item.has_name(sym::kcfi) {
+                        codegen_fn_attrs.no_sanitize |= SanitizerSet::KCFI;
                     } else if item.has_name(sym::memory) {
                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
                     } else if item.has_name(sym::memtag) {
@@ -1859,7 +1861,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: DefId) -> CodegenFnAttrs {
                     } else {
                         tcx.sess
                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
-                            .note("expected one of: `address`, `cfi`, `hwaddress`, `memory`, `memtag`, `shadow-call-stack`, or `thread`")
+                            .note("expected one of: `address`, `cfi`, `hwaddress`, `kcfi`, `memory`, `memtag`, `shadow-call-stack`, or `thread`")
                             .emit();
                     }
                 }

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -1476,13 +1476,13 @@ extern "C" void LLVMRustFreeOperandBundleDef(OperandBundleDef *Bundle) {
 
 extern "C" LLVMValueRef LLVMRustBuildCall(LLVMBuilderRef B, LLVMTypeRef Ty, LLVMValueRef Fn,
                                           LLVMValueRef *Args, unsigned NumArgs,
-                                          OperandBundleDef *Bundle) {
+                                          OperandBundleDef **OpBundles,
+                                          unsigned NumOpBundles) {
   Value *Callee = unwrap(Fn);
   FunctionType *FTy = unwrap<FunctionType>(Ty);
-  unsigned Len = Bundle ? 1 : 0;
-  ArrayRef<OperandBundleDef> Bundles = makeArrayRef(Bundle, Len);
   return wrap(unwrap(B)->CreateCall(
-      FTy, Callee, makeArrayRef(unwrap(Args), NumArgs), Bundles));
+      FTy, Callee, makeArrayRef(unwrap(Args), NumArgs),
+      makeArrayRef(*OpBundles, NumOpBundles)));
 }
 
 extern "C" LLVMValueRef LLVMRustGetInstrProfIncrementIntrinsic(LLVMModuleRef M) {
@@ -1522,14 +1522,14 @@ extern "C" LLVMValueRef
 LLVMRustBuildInvoke(LLVMBuilderRef B, LLVMTypeRef Ty, LLVMValueRef Fn,
                     LLVMValueRef *Args, unsigned NumArgs,
                     LLVMBasicBlockRef Then, LLVMBasicBlockRef Catch,
-                    OperandBundleDef *Bundle, const char *Name) {
+                    OperandBundleDef **OpBundles, unsigned NumOpBundles,
+                    const char *Name) {
   Value *Callee = unwrap(Fn);
   FunctionType *FTy = unwrap<FunctionType>(Ty);
-  unsigned Len = Bundle ? 1 : 0;
-  ArrayRef<OperandBundleDef> Bundles = makeArrayRef(Bundle, Len);
   return wrap(unwrap(B)->CreateInvoke(FTy, Callee, unwrap(Then), unwrap(Catch),
                                       makeArrayRef(unwrap(Args), NumArgs),
-                                      Bundles, Name));
+                                      makeArrayRef(*OpBundles, NumOpBundles),
+                                      Name));
 }
 
 extern "C" void LLVMRustPositionBuilderAtStart(LLVMBuilderRef B,

compiler/rustc_session/src/options.rs

@@ -368,7 +368,7 @@ mod desc {
     pub const parse_opt_panic_strategy: &str = parse_panic_strategy;
     pub const parse_oom_strategy: &str = "either `panic` or `abort`";
     pub const parse_relro_level: &str = "one of: `full`, `partial`, or `off`";
-    pub const parse_sanitizers: &str = "comma separated list of sanitizers: `address`, `cfi`, `hwaddress`, `leak`, `memory`, `memtag`, `shadow-call-stack`, or `thread`";
+    pub const parse_sanitizers: &str = "comma separated list of sanitizers: `address`, `cfi`, `hwaddress`, `kcfi`, `leak`, `memory`, `memtag`, `shadow-call-stack`, or `thread`";
     pub const parse_sanitizer_memory_track_origins: &str = "0, 1, or 2";
     pub const parse_cfguard: &str =
         "either a boolean (`yes`, `no`, `on`, `off`, etc), `checks`, or `nochecks`";
@@ -675,6 +675,7 @@ mod parse {
                 *slot |= match s {
                     "address" => SanitizerSet::ADDRESS,
                     "cfi" => SanitizerSet::CFI,
+                    "kcfi" => SanitizerSet::KCFI,
                     "leak" => SanitizerSet::LEAK,
                     "memory" => SanitizerSet::MEMORY,
                     "memtag" => SanitizerSet::MEMTAG,

compiler/rustc_session/src/session.rs

@@ -686,6 +686,10 @@ impl Session {
         self.opts.unstable_opts.sanitizer.contains(SanitizerSet::CFI)
     }
 
+    pub fn is_sanitizer_kcfi_enabled(&self) -> bool {
+        self.opts.unstable_opts.sanitizer.contains(SanitizerSet::KCFI)
+    }
+
     /// Check whether this compile session and crate type use static crt.
     pub fn crt_static(&self, crate_type: Option<CrateType>) -> bool {
         if !self.target.crt_static_respected {
@@ -1544,6 +1548,14 @@ fn validate_commandline_args_with_session_available(sess: &Session) {
         }
     }
 
+    // LLVM CFI and KCFI are mutually exclusive
+    if sess.is_sanitizer_cfi_enabled() && sess.is_sanitizer_kcfi_enabled() {
+        sess.emit_err(CannotMixAndMatchSanitizers {
+            first: "cfi".to_string(),
+            second: "kcfi".to_string(),
+        });
+    }
+
     if sess.opts.unstable_opts.stack_protector != StackProtector::None {
         if !sess.target.options.supports_stack_protector {
             sess.emit_warning(StackProtectorNotSupportedForTarget {

compiler/rustc_span/src/symbol.rs

@@ -828,6 +828,7 @@ symbols! {
         item_like_imports,
         iter,
         iter_repeat,
+        kcfi,
         keyword,
         kind,
         kreg,

compiler/rustc_symbol_mangling/Cargo.toml

@@ -10,6 +10,7 @@ bitflags = "1.2.1"
 tracing = "0.1"
 punycode = "0.4.0"
 rustc-demangle = "0.1.21"
+twox-hash = "1.6.3"
 
 rustc_span = { path = "../rustc_span" }
 rustc_middle = { path = "../rustc_middle" }