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CFI: Fix methods as function pointer cast
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Fix casting between methods and function pointers by assigning a
secondary type id to methods with their concrete self so they can be
used as function pointers.
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rcvalle committed Mar 27, 2024
1 parent 8b9e47c commit 58d656b
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Showing 5 changed files with 75 additions and 15 deletions.
41 changes: 27 additions & 14 deletions compiler/rustc_codegen_llvm/src/declare.rs
Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@ use crate::llvm;
use crate::llvm::AttributePlace::Function;
use crate::type_::Type;
use crate::value::Value;
use itertools::Itertools;
use rustc_codegen_ssa::traits::TypeMembershipMethods;
use rustc_middle::ty::{Instance, Ty};
use rustc_symbol_mangling::typeid::{
Expand Down Expand Up @@ -141,20 +142,32 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {

if self.tcx.sess.is_sanitizer_cfi_enabled() {
if let Some(instance) = instance {
let typeid = typeid_for_instance(self.tcx, instance, TypeIdOptions::empty());
self.set_type_metadata(llfn, typeid);
let typeid =
typeid_for_instance(self.tcx, instance, TypeIdOptions::GENERALIZE_POINTERS);
self.add_type_metadata(llfn, typeid);
let typeid =
typeid_for_instance(self.tcx, instance, TypeIdOptions::NORMALIZE_INTEGERS);
self.add_type_metadata(llfn, typeid);
let typeid = typeid_for_instance(
self.tcx,
instance,
TypeIdOptions::GENERALIZE_POINTERS | TypeIdOptions::NORMALIZE_INTEGERS,
);
self.add_type_metadata(llfn, typeid);
let mut typeids = Vec::new();
for options in
[TypeIdOptions::GENERALIZE_POINTERS, TypeIdOptions::NORMALIZE_INTEGERS]
.into_iter()
.powerset()
.map(TypeIdOptions::from_iter)
{
let typeid = typeid_for_instance(self.tcx, instance, options);
typeids.push(typeid.clone());
self.add_type_metadata(llfn, typeid);
}
for options in [
TypeIdOptions::NO_TYPE_ERASURE,
TypeIdOptions::GENERALIZE_POINTERS,
TypeIdOptions::NORMALIZE_INTEGERS,
]
.into_iter()
.powerset()
.map(TypeIdOptions::from_iter)
{
let typeid = typeid_for_instance(self.tcx, instance, options);
if !typeids.contains(&typeid) {
typeids.push(typeid.clone());
self.add_type_metadata(llfn, typeid);
}
}
} else {
let typeid = typeid_for_fnabi(self.tcx, fn_abi, TypeIdOptions::empty());
self.set_type_metadata(llfn, typeid);
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_symbol_mangling/src/typeid.rs
Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ bitflags! {
const GENERALIZE_POINTERS = 1;
const GENERALIZE_REPR_C = 2;
const NORMALIZE_INTEGERS = 4;
const NO_TYPE_ERASURE = 8;
}
}

Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -1116,7 +1116,8 @@ pub fn typeid_for_instance<'tcx>(
instance.args = strip_receiver_auto(tcx, instance.args)
}

if let Some(impl_id) = tcx.impl_of_method(instance.def_id())
if !options.contains(EncodeTyOptions::NO_TYPE_ERASURE)
&& let Some(impl_id) = tcx.impl_of_method(instance.def_id())
&& let Some(trait_ref) = tcx.impl_trait_ref(impl_id)
{
let impl_method = tcx.associated_item(instance.def_id());
Expand Down
Original file line number Diff line number Diff line change
@@ -0,0 +1,22 @@
// Verifies that a secondary type metadata identifier is assigned to methods with their concrete
// self so they can be used as function pointers.
//
//@ needs-sanitizer-cfi
//@ compile-flags: -Clto -Cno-prepopulate-passes -Copt-level=0 -Zsanitizer=cfi -Ctarget-feature=-crt-static

#![crate_type="lib"]

trait Trait1 {
fn foo(&self);
}

struct Type1;

impl Trait1 for Type1 {
fn foo(&self) {}
// CHECK: define{{.*}}3foo{{.*}}!type ![[TYPE1:[0-9]+]] !type !{{[0-9]+}} !type !{{[0-9]+}} !type !{{[0-9]+}} !type ![[TYPE2:[0-9]+]] !type !{{[0-9]+}}
}


// CHECK: ![[TYPE1]] = !{i64 0, !"_ZTSFvu3refIu3dynIu{{[0-9]+}}NtC{{[[:print:]]+}}_{{[[:print:]]+}}6Trait1u6regionEEE"}
// CHECK: ![[TYPE2]] = !{i64 0, !"_ZTSFvu3refIu{{[0-9]+}}NtC{{[[:print:]]+}}_{{[[:print:]]+}}5Type1EE"}
23 changes: 23 additions & 0 deletions tests/ui/sanitizer/cfi-method-fn-ptr-cast.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,23 @@
// Verifies that casting a method to a function pointer works.
//
// FIXME(#122848): Remove only-linux when fixed.
//@ only-linux
//@ needs-sanitizer-cfi
//@ compile-flags: -Clto -Copt-level=0 -Cprefer-dynamic=off -Ctarget-feature=-crt-static -Zsanitizer=cfi
//@ run-pass

trait Trait1 {
fn foo(&self);
}

struct Type1;

impl Trait1 for Type1 {
fn foo(&self) {}
}

fn main() {
let type1 = Type1 {};
let f = <Type1 as Trait1>::foo;
f(&type1);
}

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