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Rollup merge of #115164 - RalfJung:no-in-place-packed, r=b-naber

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MIR validation: reject in-place argument/return for packed fields

As discussed [here](https://rust-lang.zulipchat.com/#narrow/stream/136281-t-opsem/topic/Packed.20fields.20and.20in-place.20function.20argument.2Freturn.20passing).
This commit is contained in:
Matthias Krüger 2023-08-28 19:53:54 +02:00 committed by GitHub
commit 88b476c388
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2 changed files with 29 additions and 3 deletions
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31
compiler/rustc_const_eval/src/transform/validate.rs
View File

@ -20,6 +20,8 @@
use rustc_target::abi::{Size, FIRST_VARIANT};
use rustc_target::spec::abi::Abi;
use crate::util::is_within_packed;
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
enum EdgeKind {
Unwind,
@ -93,6 +95,7 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
cfg_checker.visit_body(body);
cfg_checker.check_cleanup_control_flow();
// Also run the TypeChecker.
for (location, msg) in validate_types(tcx, self.mir_phase, param_env, body) {
cfg_checker.fail(location, msg);
}
@ -427,14 +430,34 @@ fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location
self.check_unwind_edge(location, *unwind);
// The call destination place and Operand::Move place used as an argument might be
// passed by a reference to the callee. Consequently they must be non-overlapping.
// Currently this simply checks for duplicate places.
// passed by a reference to the callee. Consequently they must be non-overlapping
// and cannot be packed. Currently this simply checks for duplicate places.
self.place_cache.clear();
self.place_cache.insert(destination.as_ref());
if is_within_packed(self.tcx, &self.body.local_decls, *destination).is_some() {
// This is bad! The callee will expect the memory to be aligned.
self.fail(
location,
format!(
"encountered packed place in `Call` terminator destination: {:?}",
terminator.kind,
),
);
}
let mut has_duplicates = false;
for arg in args {
if let Operand::Move(place) = arg {
has_duplicates |= !self.place_cache.insert(place.as_ref());
if is_within_packed(self.tcx, &self.body.local_decls, *place).is_some() {
// This is bad! The callee will expect the memory to be aligned.
self.fail(
location,
format!(
"encountered `Move` of a packed place in `Call` terminator: {:?}",
terminator.kind,
),
);
}
}
}
@ -442,7 +465,7 @@ fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location
self.fail(
location,
format!(
"encountered overlapping memory in `Call` terminator: {:?}",
"encountered overlapping memory in `Move` arguments to `Call` terminator: {:?}",
terminator.kind,
),
);
@ -541,6 +564,8 @@ fn visit_source_scope(&mut self, scope: SourceScope) {
}
}
/// A faster version of the validation pass that only checks those things which may break when apply
/// generic substitutions.
pub fn validate_types<'tcx>(
tcx: TyCtxt<'tcx>,
mir_phase: MirPhase,

1
compiler/rustc_const_eval/src/util/alignment.rs
View File

@ -34,6 +34,7 @@ pub fn is_disaligned<'tcx, L>(
false
}
_ => {
// We cannot figure out the layout. Conservatively assume that this is disaligned.
debug!("is_disaligned({:?}) - true", place);
true
}