| use rustc_data_structures::fx::FxHashSet; |
| use rustc_errors::struct_span_err; |
| use rustc_hir as hir; |
| use rustc_hir::def_id::{DefId, LocalDefId}; |
| use rustc_hir::hir_id::HirId; |
| use rustc_hir::intravisit; |
| use rustc_hir::Node; |
| use rustc_middle::mir::visit::{MutatingUseContext, PlaceContext, Visitor}; |
| use rustc_middle::mir::*; |
| use rustc_middle::ty::cast::CastTy; |
| use rustc_middle::ty::query::Providers; |
| use rustc_middle::ty::{self, TyCtxt}; |
| use rustc_session::lint::builtin::{UNSAFE_OP_IN_UNSAFE_FN, UNUSED_UNSAFE}; |
| use rustc_session::lint::Level; |
| |
| use std::ops::Bound; |
| |
| pub struct UnsafetyChecker<'a, 'tcx> { |
| body: &'a Body<'tcx>, |
| body_did: LocalDefId, |
| const_context: bool, |
| violations: Vec<UnsafetyViolation>, |
| source_info: SourceInfo, |
| tcx: TyCtxt<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| /// Mark an `unsafe` block as used, so we don't lint it. |
| used_unsafe: FxHashSet<hir::HirId>, |
| inherited_blocks: Vec<(hir::HirId, bool)>, |
| } |
| |
| impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> { |
| fn new( |
| const_context: bool, |
| body: &'a Body<'tcx>, |
| body_did: LocalDefId, |
| tcx: TyCtxt<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| ) -> Self { |
| Self { |
| body, |
| body_did, |
| const_context, |
| violations: vec![], |
| source_info: SourceInfo::outermost(body.span), |
| tcx, |
| param_env, |
| used_unsafe: Default::default(), |
| inherited_blocks: vec![], |
| } |
| } |
| } |
| |
| impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> { |
| fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) { |
| self.source_info = terminator.source_info; |
| match terminator.kind { |
| TerminatorKind::Goto { .. } |
| | TerminatorKind::SwitchInt { .. } |
| | TerminatorKind::Drop { .. } |
| | TerminatorKind::Yield { .. } |
| | TerminatorKind::Assert { .. } |
| | TerminatorKind::DropAndReplace { .. } |
| | TerminatorKind::GeneratorDrop |
| | TerminatorKind::Resume |
| | TerminatorKind::Abort |
| | TerminatorKind::Return |
| | TerminatorKind::Unreachable |
| | TerminatorKind::FalseEdge { .. } |
| | TerminatorKind::FalseUnwind { .. } => { |
| // safe (at least as emitted during MIR construction) |
| } |
| |
| TerminatorKind::Call { ref func, .. } => { |
| let func_ty = func.ty(self.body, self.tcx); |
| let sig = func_ty.fn_sig(self.tcx); |
| if let hir::Unsafety::Unsafe = sig.unsafety() { |
| self.require_unsafe( |
| UnsafetyViolationKind::General, |
| UnsafetyViolationDetails::CallToUnsafeFunction, |
| ) |
| } |
| |
| if let ty::FnDef(func_id, _) = func_ty.kind() { |
| self.check_target_features(*func_id); |
| } |
| } |
| |
| TerminatorKind::InlineAsm { .. } => self.require_unsafe( |
| UnsafetyViolationKind::General, |
| UnsafetyViolationDetails::UseOfInlineAssembly, |
| ), |
| } |
| self.super_terminator(terminator, location); |
| } |
| |
| fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) { |
| self.source_info = statement.source_info; |
| match statement.kind { |
| StatementKind::Assign(..) |
| | StatementKind::FakeRead(..) |
| | StatementKind::SetDiscriminant { .. } |
| | StatementKind::StorageLive(..) |
| | StatementKind::StorageDead(..) |
| | StatementKind::Retag { .. } |
| | StatementKind::AscribeUserType(..) |
| | StatementKind::Coverage(..) |
| | StatementKind::Nop => { |
| // safe (at least as emitted during MIR construction) |
| } |
| |
| StatementKind::LlvmInlineAsm { .. } => self.require_unsafe( |
| UnsafetyViolationKind::General, |
| UnsafetyViolationDetails::UseOfInlineAssembly, |
| ), |
| StatementKind::CopyNonOverlapping(..) => unreachable!(), |
| } |
| self.super_statement(statement, location); |
| } |
| |
| fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) { |
| match rvalue { |
| Rvalue::Aggregate(box ref aggregate, _) => match aggregate { |
| &AggregateKind::Array(..) | &AggregateKind::Tuple => {} |
| &AggregateKind::Adt(ref def, ..) => { |
| match self.tcx.layout_scalar_valid_range(def.did) { |
| (Bound::Unbounded, Bound::Unbounded) => {} |
| _ => self.require_unsafe( |
| UnsafetyViolationKind::General, |
| UnsafetyViolationDetails::InitializingTypeWith, |
| ), |
| } |
| } |
| &AggregateKind::Closure(def_id, _) | &AggregateKind::Generator(def_id, _, _) => { |
| let UnsafetyCheckResult { violations, unsafe_blocks } = |
| self.tcx.unsafety_check_result(def_id.expect_local()); |
| self.register_violations(&violations, &unsafe_blocks); |
| } |
| }, |
| // casting pointers to ints is unsafe in const fn because the const evaluator cannot |
| // possibly know what the result of various operations like `address / 2` would be |
| // pointers during const evaluation have no integral address, only an abstract one |
| Rvalue::Cast(CastKind::Misc, ref operand, cast_ty) |
| if self.const_context && self.tcx.features().const_raw_ptr_to_usize_cast => |
| { |
| let operand_ty = operand.ty(self.body, self.tcx); |
| let cast_in = CastTy::from_ty(operand_ty).expect("bad input type for cast"); |
| let cast_out = CastTy::from_ty(cast_ty).expect("bad output type for cast"); |
| match (cast_in, cast_out) { |
| (CastTy::Ptr(_) | CastTy::FnPtr, CastTy::Int(_)) => { |
| self.require_unsafe( |
| UnsafetyViolationKind::General, |
| UnsafetyViolationDetails::CastOfPointerToInt, |
| ); |
| } |
| _ => {} |
| } |
| } |
| _ => {} |
| } |
| self.super_rvalue(rvalue, location); |
| } |
| |
| fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, _location: Location) { |
| // On types with `scalar_valid_range`, prevent |
| // * `&mut x.field` |
| // * `x.field = y;` |
| // * `&x.field` if `field`'s type has interior mutability |
| // because either of these would allow modifying the layout constrained field and |
| // insert values that violate the layout constraints. |
| if context.is_mutating_use() || context.is_borrow() { |
| self.check_mut_borrowing_layout_constrained_field(*place, context.is_mutating_use()); |
| } |
| |
| // Some checks below need the extra metainfo of the local declaration. |
| let decl = &self.body.local_decls[place.local]; |
| |
| // Check the base local: it might be an unsafe-to-access static. We only check derefs of the |
| // temporary holding the static pointer to avoid duplicate errors |
| // <https://github.com/rust-lang/rust/pull/78068#issuecomment-731753506>. |
| if decl.internal && place.projection.first() == Some(&ProjectionElem::Deref) { |
| // If the projection root is an artifical local that we introduced when |
| // desugaring `static`, give a more specific error message |
| // (avoid the general "raw pointer" clause below, that would only be confusing). |
| if let Some(box LocalInfo::StaticRef { def_id, .. }) = decl.local_info { |
| if self.tcx.is_mutable_static(def_id) { |
| self.require_unsafe( |
| UnsafetyViolationKind::General, |
| UnsafetyViolationDetails::UseOfMutableStatic, |
| ); |
| return; |
| } else if self.tcx.is_foreign_item(def_id) { |
| self.require_unsafe( |
| UnsafetyViolationKind::General, |
| UnsafetyViolationDetails::UseOfExternStatic, |
| ); |
| return; |
| } |
| } |
| } |
| |
| // Check for raw pointer `Deref`. |
| for (base, proj) in place.iter_projections() { |
| if proj == ProjectionElem::Deref { |
| let base_ty = base.ty(self.body, self.tcx).ty; |
| if base_ty.is_unsafe_ptr() { |
| self.require_unsafe( |
| UnsafetyViolationKind::General, |
| UnsafetyViolationDetails::DerefOfRawPointer, |
| ) |
| } |
| } |
| } |
| |
| // Check for union fields. For this we traverse right-to-left, as the last `Deref` changes |
| // whether we *read* the union field or potentially *write* to it (if this place is being assigned to). |
| let mut saw_deref = false; |
| for (base, proj) in place.iter_projections().rev() { |
| if proj == ProjectionElem::Deref { |
| saw_deref = true; |
| continue; |
| } |
| |
| let base_ty = base.ty(self.body, self.tcx).ty; |
| if base_ty.ty_adt_def().map_or(false, |adt| adt.is_union()) { |
| // If we did not hit a `Deref` yet and the overall place use is an assignment, the |
| // rules are different. |
| let assign_to_field = !saw_deref |
| && matches!( |
| context, |
| PlaceContext::MutatingUse( |
| MutatingUseContext::Store |
| | MutatingUseContext::Drop |
| | MutatingUseContext::AsmOutput |
| ) |
| ); |
| // If this is just an assignment, determine if the assigned type needs dropping. |
| if assign_to_field { |
| // We have to check the actual type of the assignment, as that determines if the |
| // old value is being dropped. |
| let assigned_ty = place.ty(&self.body.local_decls, self.tcx).ty; |
| // To avoid semver hazard, we only consider `Copy` and `ManuallyDrop` non-dropping. |
| let manually_drop = assigned_ty |
| .ty_adt_def() |
| .map_or(false, |adt_def| adt_def.is_manually_drop()); |
| let nodrop = manually_drop |
| || assigned_ty.is_copy_modulo_regions( |
| self.tcx.at(self.source_info.span), |
| self.param_env, |
| ); |
| if !nodrop { |
| self.require_unsafe( |
| UnsafetyViolationKind::General, |
| UnsafetyViolationDetails::AssignToDroppingUnionField, |
| ); |
| } else { |
| // write to non-drop union field, safe |
| } |
| } else { |
| self.require_unsafe( |
| UnsafetyViolationKind::General, |
| UnsafetyViolationDetails::AccessToUnionField, |
| ) |
| } |
| } |
| } |
| } |
| } |
| |
| impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> { |
| fn require_unsafe(&mut self, kind: UnsafetyViolationKind, details: UnsafetyViolationDetails) { |
| // Violations can turn out to be `UnsafeFn` during analysis, but they should not start out as such. |
| assert_ne!(kind, UnsafetyViolationKind::UnsafeFn); |
| |
| let source_info = self.source_info; |
| let lint_root = self.body.source_scopes[self.source_info.scope] |
| .local_data |
| .as_ref() |
| .assert_crate_local() |
| .lint_root; |
| self.register_violations( |
| &[UnsafetyViolation { source_info, lint_root, kind, details }], |
| &[], |
| ); |
| } |
| |
| fn register_violations( |
| &mut self, |
| violations: &[UnsafetyViolation], |
| unsafe_blocks: &[(hir::HirId, bool)], |
| ) { |
| let safety = self.body.source_scopes[self.source_info.scope] |
| .local_data |
| .as_ref() |
| .assert_crate_local() |
| .safety; |
| let within_unsafe = match safety { |
| // `unsafe` blocks are required in safe code |
| Safety::Safe => { |
| for violation in violations { |
| match violation.kind { |
| UnsafetyViolationKind::General => {} |
| UnsafetyViolationKind::UnsafeFn => { |
| bug!("`UnsafetyViolationKind::UnsafeFn` in an `Safe` context") |
| } |
| } |
| if !self.violations.contains(violation) { |
| self.violations.push(*violation) |
| } |
| } |
| false |
| } |
| // With the RFC 2585, no longer allow `unsafe` operations in `unsafe fn`s |
| Safety::FnUnsafe => { |
| for violation in violations { |
| let mut violation = *violation; |
| |
| violation.kind = UnsafetyViolationKind::UnsafeFn; |
| if !self.violations.contains(&violation) { |
| self.violations.push(violation) |
| } |
| } |
| false |
| } |
| Safety::BuiltinUnsafe => true, |
| Safety::ExplicitUnsafe(hir_id) => { |
| // mark unsafe block as used if there are any unsafe operations inside |
| if !violations.is_empty() { |
| self.used_unsafe.insert(hir_id); |
| } |
| true |
| } |
| }; |
| self.inherited_blocks.extend( |
| unsafe_blocks.iter().map(|&(hir_id, is_used)| (hir_id, is_used && !within_unsafe)), |
| ); |
| } |
| fn check_mut_borrowing_layout_constrained_field( |
| &mut self, |
| place: Place<'tcx>, |
| is_mut_use: bool, |
| ) { |
| for (place_base, elem) in place.iter_projections().rev() { |
| match elem { |
| // Modifications behind a dereference don't affect the value of |
| // the pointer. |
| ProjectionElem::Deref => return, |
| ProjectionElem::Field(..) => { |
| let ty = place_base.ty(&self.body.local_decls, self.tcx).ty; |
| if let ty::Adt(def, _) = ty.kind() { |
| if self.tcx.layout_scalar_valid_range(def.did) |
| != (Bound::Unbounded, Bound::Unbounded) |
| { |
| let details = if is_mut_use { |
| UnsafetyViolationDetails::MutationOfLayoutConstrainedField |
| |
| // Check `is_freeze` as late as possible to avoid cycle errors |
| // with opaque types. |
| } else if !place |
| .ty(self.body, self.tcx) |
| .ty |
| .is_freeze(self.tcx.at(self.source_info.span), self.param_env) |
| { |
| UnsafetyViolationDetails::BorrowOfLayoutConstrainedField |
| } else { |
| continue; |
| }; |
| self.require_unsafe(UnsafetyViolationKind::General, details); |
| } |
| } |
| } |
| _ => {} |
| } |
| } |
| } |
| |
| /// Checks whether calling `func_did` needs an `unsafe` context or not, i.e. whether |
| /// the called function has target features the calling function hasn't. |
| fn check_target_features(&mut self, func_did: DefId) { |
| let callee_features = &self.tcx.codegen_fn_attrs(func_did).target_features; |
| let self_features = &self.tcx.codegen_fn_attrs(self.body_did).target_features; |
| |
| // Is `callee_features` a subset of `calling_features`? |
| if !callee_features.iter().all(|feature| self_features.contains(feature)) { |
| self.require_unsafe( |
| UnsafetyViolationKind::General, |
| UnsafetyViolationDetails::CallToFunctionWith, |
| ) |
| } |
| } |
| } |
| |
| pub(crate) fn provide(providers: &mut Providers) { |
| *providers = Providers { |
| unsafety_check_result: |tcx, def_id| { |
| if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) { |
| tcx.unsafety_check_result_for_const_arg(def) |
| } else { |
| unsafety_check_result(tcx, ty::WithOptConstParam::unknown(def_id)) |
| } |
| }, |
| unsafety_check_result_for_const_arg: |tcx, (did, param_did)| { |
| unsafety_check_result( |
| tcx, |
| ty::WithOptConstParam { did, const_param_did: Some(param_did) }, |
| ) |
| }, |
| ..*providers |
| }; |
| } |
| |
| struct UnusedUnsafeVisitor<'a> { |
| used_unsafe: &'a FxHashSet<hir::HirId>, |
| unsafe_blocks: &'a mut Vec<(hir::HirId, bool)>, |
| } |
| |
| impl<'a, 'tcx> intravisit::Visitor<'tcx> for UnusedUnsafeVisitor<'a> { |
| type Map = intravisit::ErasedMap<'tcx>; |
| |
| fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> { |
| intravisit::NestedVisitorMap::None |
| } |
| |
| fn visit_block(&mut self, block: &'tcx hir::Block<'tcx>) { |
| intravisit::walk_block(self, block); |
| |
| if let hir::BlockCheckMode::UnsafeBlock(hir::UnsafeSource::UserProvided) = block.rules { |
| self.unsafe_blocks.push((block.hir_id, self.used_unsafe.contains(&block.hir_id))); |
| } |
| } |
| } |
| |
| fn check_unused_unsafe( |
| tcx: TyCtxt<'_>, |
| def_id: LocalDefId, |
| used_unsafe: &FxHashSet<hir::HirId>, |
| unsafe_blocks: &mut Vec<(hir::HirId, bool)>, |
| ) { |
| let body_id = tcx.hir().maybe_body_owned_by(tcx.hir().local_def_id_to_hir_id(def_id)); |
| |
| let body_id = match body_id { |
| Some(body) => body, |
| None => { |
| debug!("check_unused_unsafe({:?}) - no body found", def_id); |
| return; |
| } |
| }; |
| let body = tcx.hir().body(body_id); |
| debug!("check_unused_unsafe({:?}, body={:?}, used_unsafe={:?})", def_id, body, used_unsafe); |
| |
| let mut visitor = UnusedUnsafeVisitor { used_unsafe, unsafe_blocks }; |
| intravisit::Visitor::visit_body(&mut visitor, body); |
| } |
| |
| fn unsafety_check_result<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| def: ty::WithOptConstParam<LocalDefId>, |
| ) -> &'tcx UnsafetyCheckResult { |
| debug!("unsafety_violations({:?})", def); |
| |
| // N.B., this borrow is valid because all the consumers of |
| // `mir_built` force this. |
| let body = &tcx.mir_built(def).borrow(); |
| |
| let param_env = tcx.param_env(def.did); |
| |
| let id = tcx.hir().local_def_id_to_hir_id(def.did); |
| let const_context = match tcx.hir().body_owner_kind(id) { |
| hir::BodyOwnerKind::Closure => false, |
| hir::BodyOwnerKind::Fn => tcx.is_const_fn_raw(def.did.to_def_id()), |
| hir::BodyOwnerKind::Const | hir::BodyOwnerKind::Static(_) => true, |
| }; |
| let mut checker = UnsafetyChecker::new(const_context, body, def.did, tcx, param_env); |
| checker.visit_body(&body); |
| |
| check_unused_unsafe(tcx, def.did, &checker.used_unsafe, &mut checker.inherited_blocks); |
| |
| tcx.arena.alloc(UnsafetyCheckResult { |
| violations: checker.violations.into(), |
| unsafe_blocks: checker.inherited_blocks.into(), |
| }) |
| } |
| |
| /// Returns the `HirId` for an enclosing scope that is also `unsafe`. |
| fn is_enclosed( |
| tcx: TyCtxt<'_>, |
| used_unsafe: &FxHashSet<hir::HirId>, |
| id: hir::HirId, |
| unsafe_op_in_unsafe_fn_allowed: bool, |
| ) -> Option<(&'static str, hir::HirId)> { |
| let parent_id = tcx.hir().get_parent_node(id); |
| if parent_id != id { |
| if used_unsafe.contains(&parent_id) { |
| Some(("block", parent_id)) |
| } else if let Some(Node::Item(&hir::Item { |
| kind: hir::ItemKind::Fn(ref sig, _, _), .. |
| })) = tcx.hir().find(parent_id) |
| { |
| if sig.header.unsafety == hir::Unsafety::Unsafe && unsafe_op_in_unsafe_fn_allowed { |
| Some(("fn", parent_id)) |
| } else { |
| None |
| } |
| } else { |
| is_enclosed(tcx, used_unsafe, parent_id, unsafe_op_in_unsafe_fn_allowed) |
| } |
| } else { |
| None |
| } |
| } |
| |
| fn report_unused_unsafe(tcx: TyCtxt<'_>, used_unsafe: &FxHashSet<hir::HirId>, id: hir::HirId) { |
| let span = tcx.sess.source_map().guess_head_span(tcx.hir().span(id)); |
| tcx.struct_span_lint_hir(UNUSED_UNSAFE, id, span, |lint| { |
| let msg = "unnecessary `unsafe` block"; |
| let mut db = lint.build(msg); |
| db.span_label(span, msg); |
| if let Some((kind, id)) = |
| is_enclosed(tcx, used_unsafe, id, unsafe_op_in_unsafe_fn_allowed(tcx, id)) |
| { |
| db.span_label( |
| tcx.sess.source_map().guess_head_span(tcx.hir().span(id)), |
| format!("because it's nested under this `unsafe` {}", kind), |
| ); |
| } |
| db.emit(); |
| }); |
| } |
| |
| pub fn check_unsafety(tcx: TyCtxt<'_>, def_id: LocalDefId) { |
| debug!("check_unsafety({:?})", def_id); |
| |
| // closures are handled by their parent fn. |
| if tcx.is_closure(def_id.to_def_id()) { |
| return; |
| } |
| |
| let UnsafetyCheckResult { violations, unsafe_blocks } = tcx.unsafety_check_result(def_id); |
| |
| for &UnsafetyViolation { source_info, lint_root, kind, details } in violations.iter() { |
| let (description, note) = details.description_and_note(); |
| |
| // Report an error. |
| let unsafe_fn_msg = |
| if unsafe_op_in_unsafe_fn_allowed(tcx, lint_root) { " function or" } else { "" }; |
| |
| match kind { |
| UnsafetyViolationKind::General => { |
| // once |
| struct_span_err!( |
| tcx.sess, |
| source_info.span, |
| E0133, |
| "{} is unsafe and requires unsafe{} block", |
| description, |
| unsafe_fn_msg, |
| ) |
| .span_label(source_info.span, description) |
| .note(note) |
| .emit(); |
| } |
| UnsafetyViolationKind::UnsafeFn => tcx.struct_span_lint_hir( |
| UNSAFE_OP_IN_UNSAFE_FN, |
| lint_root, |
| source_info.span, |
| |lint| { |
| lint.build(&format!( |
| "{} is unsafe and requires unsafe block (error E0133)", |
| description, |
| )) |
| .span_label(source_info.span, description) |
| .note(note) |
| .emit(); |
| }, |
| ), |
| } |
| } |
| |
| let (mut unsafe_used, mut unsafe_unused): (FxHashSet<_>, Vec<_>) = Default::default(); |
| for &(block_id, is_used) in unsafe_blocks.iter() { |
| if is_used { |
| unsafe_used.insert(block_id); |
| } else { |
| unsafe_unused.push(block_id); |
| } |
| } |
| // The unused unsafe blocks might not be in source order; sort them so that the unused unsafe |
| // error messages are properly aligned and the issue-45107 and lint-unused-unsafe tests pass. |
| unsafe_unused.sort_by_cached_key(|hir_id| tcx.hir().span(*hir_id)); |
| |
| for &block_id in &unsafe_unused { |
| report_unused_unsafe(tcx, &unsafe_used, block_id); |
| } |
| } |
| |
| fn unsafe_op_in_unsafe_fn_allowed(tcx: TyCtxt<'_>, id: HirId) -> bool { |
| tcx.lint_level_at_node(UNSAFE_OP_IN_UNSAFE_FN, id).0 == Level::Allow |
| } |
