630 lines
24 KiB
Rust
630 lines
24 KiB
Rust
use rustc_data_structures::fx::FxHashMap;
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use rustc_errors::struct_span_err;
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use rustc_hir as hir;
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use rustc_hir::def_id::{DefId, LocalDefId};
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use rustc_hir::hir_id::HirId;
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use rustc_hir::intravisit;
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use rustc_middle::mir::visit::{MutatingUseContext, PlaceContext, Visitor};
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use rustc_middle::ty::query::Providers;
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use rustc_middle::ty::{self, TyCtxt};
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use rustc_middle::{lint, mir::*};
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use rustc_session::lint::builtin::{UNSAFE_OP_IN_UNSAFE_FN, UNUSED_UNSAFE};
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use rustc_session::lint::Level;
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use std::collections::hash_map;
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use std::ops::Bound;
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pub struct UnsafetyChecker<'a, 'tcx> {
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body: &'a Body<'tcx>,
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body_did: LocalDefId,
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violations: Vec<UnsafetyViolation>,
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source_info: SourceInfo,
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tcx: TyCtxt<'tcx>,
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param_env: ty::ParamEnv<'tcx>,
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/// Used `unsafe` blocks in this function. This is used for the "unused_unsafe" lint.
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///
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/// The keys are the used `unsafe` blocks, the UnusedUnsafeKind indicates whether
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/// or not any of the usages happen at a place that doesn't allow `unsafe_op_in_unsafe_fn`.
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used_unsafe_blocks: FxHashMap<HirId, UsedUnsafeBlockData>,
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}
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impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> {
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fn new(
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body: &'a Body<'tcx>,
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body_did: LocalDefId,
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tcx: TyCtxt<'tcx>,
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param_env: ty::ParamEnv<'tcx>,
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) -> Self {
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Self {
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body,
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body_did,
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violations: vec![],
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source_info: SourceInfo::outermost(body.span),
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tcx,
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param_env,
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used_unsafe_blocks: Default::default(),
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}
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}
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}
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impl<'tcx> Visitor<'tcx> for UnsafetyChecker<'_, 'tcx> {
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fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
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self.source_info = terminator.source_info;
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match terminator.kind {
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TerminatorKind::Goto { .. }
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| TerminatorKind::SwitchInt { .. }
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| TerminatorKind::Drop { .. }
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| TerminatorKind::Yield { .. }
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| TerminatorKind::Assert { .. }
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| TerminatorKind::DropAndReplace { .. }
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| TerminatorKind::GeneratorDrop
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| TerminatorKind::Resume
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| TerminatorKind::Abort
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| TerminatorKind::Return
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| TerminatorKind::Unreachable
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| TerminatorKind::FalseEdge { .. }
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| TerminatorKind::FalseUnwind { .. } => {
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// safe (at least as emitted during MIR construction)
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}
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TerminatorKind::Call { ref func, .. } => {
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let func_ty = func.ty(self.body, self.tcx);
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let func_id =
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if let ty::FnDef(func_id, _) = func_ty.kind() { Some(func_id) } else { None };
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let sig = func_ty.fn_sig(self.tcx);
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if let hir::Unsafety::Unsafe = sig.unsafety() {
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self.require_unsafe(
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UnsafetyViolationKind::General,
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UnsafetyViolationDetails::CallToUnsafeFunction,
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)
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}
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if let Some(func_id) = func_id {
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self.check_target_features(*func_id);
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}
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}
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TerminatorKind::InlineAsm { .. } => self.require_unsafe(
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UnsafetyViolationKind::General,
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UnsafetyViolationDetails::UseOfInlineAssembly,
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),
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}
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self.super_terminator(terminator, location);
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}
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fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
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self.source_info = statement.source_info;
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match statement.kind {
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StatementKind::Assign(..)
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| StatementKind::FakeRead(..)
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| StatementKind::SetDiscriminant { .. }
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| StatementKind::Deinit(..)
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| StatementKind::StorageLive(..)
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| StatementKind::StorageDead(..)
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| StatementKind::Retag { .. }
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| StatementKind::AscribeUserType(..)
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| StatementKind::Coverage(..)
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| StatementKind::Nop => {
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// safe (at least as emitted during MIR construction)
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}
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StatementKind::CopyNonOverlapping(..) => unreachable!(),
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}
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self.super_statement(statement, location);
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}
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fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
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match rvalue {
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Rvalue::Aggregate(box ref aggregate, _) => match aggregate {
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&AggregateKind::Array(..) | &AggregateKind::Tuple => {}
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&AggregateKind::Adt(adt_did, ..) => {
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match self.tcx.layout_scalar_valid_range(adt_did) {
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(Bound::Unbounded, Bound::Unbounded) => {}
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_ => self.require_unsafe(
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UnsafetyViolationKind::General,
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UnsafetyViolationDetails::InitializingTypeWith,
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),
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}
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}
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&AggregateKind::Closure(def_id, _) | &AggregateKind::Generator(def_id, _, _) => {
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let UnsafetyCheckResult { violations, used_unsafe_blocks, .. } =
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self.tcx.unsafety_check_result(def_id.expect_local());
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self.register_violations(
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violations,
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used_unsafe_blocks.iter().map(|(&h, &d)| (h, d)),
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);
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}
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},
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_ => {}
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}
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self.super_rvalue(rvalue, location);
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}
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fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, _location: Location) {
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// On types with `scalar_valid_range`, prevent
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// * `&mut x.field`
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// * `x.field = y;`
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// * `&x.field` if `field`'s type has interior mutability
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// because either of these would allow modifying the layout constrained field and
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// insert values that violate the layout constraints.
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if context.is_mutating_use() || context.is_borrow() {
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self.check_mut_borrowing_layout_constrained_field(*place, context.is_mutating_use());
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}
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// Some checks below need the extra meta info of the local declaration.
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let decl = &self.body.local_decls[place.local];
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// Check the base local: it might be an unsafe-to-access static. We only check derefs of the
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// temporary holding the static pointer to avoid duplicate errors
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// <https://github.com/rust-lang/rust/pull/78068#issuecomment-731753506>.
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if decl.internal && place.projection.first() == Some(&ProjectionElem::Deref) {
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// If the projection root is an artificial local that we introduced when
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// desugaring `static`, give a more specific error message
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// (avoid the general "raw pointer" clause below, that would only be confusing).
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if let Some(box LocalInfo::StaticRef { def_id, .. }) = decl.local_info {
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if self.tcx.is_mutable_static(def_id) {
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self.require_unsafe(
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UnsafetyViolationKind::General,
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UnsafetyViolationDetails::UseOfMutableStatic,
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);
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return;
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} else if self.tcx.is_foreign_item(def_id) {
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self.require_unsafe(
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UnsafetyViolationKind::General,
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UnsafetyViolationDetails::UseOfExternStatic,
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);
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return;
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}
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}
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}
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// Check for raw pointer `Deref`.
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for (base, proj) in place.iter_projections() {
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if proj == ProjectionElem::Deref {
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let base_ty = base.ty(self.body, self.tcx).ty;
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if base_ty.is_unsafe_ptr() {
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self.require_unsafe(
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UnsafetyViolationKind::General,
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UnsafetyViolationDetails::DerefOfRawPointer,
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)
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}
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}
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}
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// Check for union fields. For this we traverse right-to-left, as the last `Deref` changes
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// whether we *read* the union field or potentially *write* to it (if this place is being assigned to).
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let mut saw_deref = false;
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for (base, proj) in place.iter_projections().rev() {
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if proj == ProjectionElem::Deref {
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saw_deref = true;
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continue;
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}
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let base_ty = base.ty(self.body, self.tcx).ty;
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if base_ty.is_union() {
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// If we did not hit a `Deref` yet and the overall place use is an assignment, the
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// rules are different.
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let assign_to_field = !saw_deref
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&& matches!(
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context,
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PlaceContext::MutatingUse(
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MutatingUseContext::Store
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| MutatingUseContext::Drop
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| MutatingUseContext::AsmOutput
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)
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);
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// If this is just an assignment, determine if the assigned type needs dropping.
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if assign_to_field {
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// We have to check the actual type of the assignment, as that determines if the
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// old value is being dropped.
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let assigned_ty = place.ty(&self.body.local_decls, self.tcx).ty;
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// To avoid semver hazard, we only consider `Copy` and `ManuallyDrop` non-dropping.
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let manually_drop = assigned_ty
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.ty_adt_def()
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.map_or(false, |adt_def| adt_def.is_manually_drop());
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let nodrop = manually_drop
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|| assigned_ty.is_copy_modulo_regions(
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self.tcx.at(self.source_info.span),
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self.param_env,
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);
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if !nodrop {
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self.require_unsafe(
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UnsafetyViolationKind::General,
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UnsafetyViolationDetails::AssignToDroppingUnionField,
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);
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} else {
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// write to non-drop union field, safe
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}
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} else {
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self.require_unsafe(
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UnsafetyViolationKind::General,
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UnsafetyViolationDetails::AccessToUnionField,
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)
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}
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}
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}
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}
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}
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impl<'tcx> UnsafetyChecker<'_, 'tcx> {
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fn require_unsafe(&mut self, kind: UnsafetyViolationKind, details: UnsafetyViolationDetails) {
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// Violations can turn out to be `UnsafeFn` during analysis, but they should not start out as such.
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assert_ne!(kind, UnsafetyViolationKind::UnsafeFn);
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let source_info = self.source_info;
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let lint_root = self.body.source_scopes[self.source_info.scope]
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.local_data
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.as_ref()
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.assert_crate_local()
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.lint_root;
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self.register_violations(
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[&UnsafetyViolation { source_info, lint_root, kind, details }],
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[],
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);
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}
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fn register_violations<'a>(
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&mut self,
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violations: impl IntoIterator<Item = &'a UnsafetyViolation>,
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new_used_unsafe_blocks: impl IntoIterator<Item = (HirId, UsedUnsafeBlockData)>,
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) {
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use UsedUnsafeBlockData::{AllAllowedInUnsafeFn, SomeDisallowedInUnsafeFn};
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let update_entry = |this: &mut Self, hir_id, new_usage| {
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match this.used_unsafe_blocks.entry(hir_id) {
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hash_map::Entry::Occupied(mut entry) => {
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if new_usage == SomeDisallowedInUnsafeFn {
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*entry.get_mut() = SomeDisallowedInUnsafeFn;
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}
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}
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hash_map::Entry::Vacant(entry) => {
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entry.insert(new_usage);
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}
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};
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};
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let safety = self.body.source_scopes[self.source_info.scope]
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.local_data
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.as_ref()
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.assert_crate_local()
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.safety;
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match safety {
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// `unsafe` blocks are required in safe code
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Safety::Safe => violations.into_iter().for_each(|&violation| {
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match violation.kind {
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UnsafetyViolationKind::General => {}
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UnsafetyViolationKind::UnsafeFn => {
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bug!("`UnsafetyViolationKind::UnsafeFn` in an `Safe` context")
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}
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}
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if !self.violations.contains(&violation) {
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self.violations.push(violation)
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}
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}),
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// With the RFC 2585, no longer allow `unsafe` operations in `unsafe fn`s
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Safety::FnUnsafe => violations.into_iter().for_each(|&(mut violation)| {
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violation.kind = UnsafetyViolationKind::UnsafeFn;
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if !self.violations.contains(&violation) {
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self.violations.push(violation)
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}
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}),
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Safety::BuiltinUnsafe => {}
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Safety::ExplicitUnsafe(hir_id) => violations.into_iter().for_each(|violation| {
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update_entry(
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self,
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hir_id,
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match self.tcx.lint_level_at_node(UNSAFE_OP_IN_UNSAFE_FN, violation.lint_root).0
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{
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Level::Allow => AllAllowedInUnsafeFn(violation.lint_root),
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_ => SomeDisallowedInUnsafeFn,
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},
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)
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}),
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};
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new_used_unsafe_blocks
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.into_iter()
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.for_each(|(hir_id, usage_data)| update_entry(self, hir_id, usage_data));
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}
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fn check_mut_borrowing_layout_constrained_field(
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&mut self,
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place: Place<'tcx>,
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is_mut_use: bool,
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) {
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for (place_base, elem) in place.iter_projections().rev() {
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match elem {
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// Modifications behind a dereference don't affect the value of
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// the pointer.
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ProjectionElem::Deref => return,
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ProjectionElem::Field(..) => {
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let ty = place_base.ty(&self.body.local_decls, self.tcx).ty;
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if let ty::Adt(def, _) = ty.kind() {
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if self.tcx.layout_scalar_valid_range(def.did())
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!= (Bound::Unbounded, Bound::Unbounded)
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{
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let details = if is_mut_use {
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UnsafetyViolationDetails::MutationOfLayoutConstrainedField
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// Check `is_freeze` as late as possible to avoid cycle errors
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// with opaque types.
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} else if !place
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.ty(self.body, self.tcx)
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.ty
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.is_freeze(self.tcx.at(self.source_info.span), self.param_env)
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{
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UnsafetyViolationDetails::BorrowOfLayoutConstrainedField
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} else {
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continue;
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};
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self.require_unsafe(UnsafetyViolationKind::General, details);
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}
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}
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}
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_ => {}
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}
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}
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}
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/// Checks whether calling `func_did` needs an `unsafe` context or not, i.e. whether
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/// the called function has target features the calling function hasn't.
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fn check_target_features(&mut self, func_did: DefId) {
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// Unsafety isn't required on wasm targets. For more information see
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// the corresponding check in typeck/src/collect.rs
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if self.tcx.sess.target.options.is_like_wasm {
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return;
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}
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let callee_features = &self.tcx.codegen_fn_attrs(func_did).target_features;
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// The body might be a constant, so it doesn't have codegen attributes.
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let self_features = &self.tcx.body_codegen_attrs(self.body_did.to_def_id()).target_features;
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// Is `callee_features` a subset of `calling_features`?
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if !callee_features.iter().all(|feature| self_features.contains(feature)) {
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self.require_unsafe(
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UnsafetyViolationKind::General,
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UnsafetyViolationDetails::CallToFunctionWith,
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)
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}
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}
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}
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pub(crate) fn provide(providers: &mut Providers) {
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*providers = Providers {
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unsafety_check_result: |tcx, def_id| {
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if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
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tcx.unsafety_check_result_for_const_arg(def)
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} else {
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unsafety_check_result(tcx, ty::WithOptConstParam::unknown(def_id))
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}
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},
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unsafety_check_result_for_const_arg: |tcx, (did, param_did)| {
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unsafety_check_result(
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tcx,
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ty::WithOptConstParam { did, const_param_did: Some(param_did) },
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)
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},
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..*providers
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};
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}
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/// Context information for [`UnusedUnsafeVisitor`] traversal,
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/// saves (innermost) relevant context
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#[derive(Copy, Clone, Debug)]
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enum Context {
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Safe,
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/// in an `unsafe fn`
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UnsafeFn(HirId),
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/// in a *used* `unsafe` block
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/// (i.e. a block without unused-unsafe warning)
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UnsafeBlock(HirId),
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}
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struct UnusedUnsafeVisitor<'a, 'tcx> {
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tcx: TyCtxt<'tcx>,
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used_unsafe_blocks: &'a FxHashMap<HirId, UsedUnsafeBlockData>,
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context: Context,
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unused_unsafes: &'a mut Vec<(HirId, UnusedUnsafe)>,
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}
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impl<'tcx> intravisit::Visitor<'tcx> for UnusedUnsafeVisitor<'_, 'tcx> {
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fn visit_block(&mut self, block: &'tcx hir::Block<'tcx>) {
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use UsedUnsafeBlockData::{AllAllowedInUnsafeFn, SomeDisallowedInUnsafeFn};
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if let hir::BlockCheckMode::UnsafeBlock(hir::UnsafeSource::UserProvided) = block.rules {
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let used = match self.tcx.lint_level_at_node(UNUSED_UNSAFE, block.hir_id) {
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(Level::Allow, _) => Some(SomeDisallowedInUnsafeFn),
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_ => self.used_unsafe_blocks.get(&block.hir_id).copied(),
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};
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let unused_unsafe = match (self.context, used) {
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(_, None) => UnusedUnsafe::Unused,
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(Context::Safe, Some(_))
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| (Context::UnsafeFn(_), Some(SomeDisallowedInUnsafeFn)) => {
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let previous_context = self.context;
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self.context = Context::UnsafeBlock(block.hir_id);
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intravisit::walk_block(self, block);
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self.context = previous_context;
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return;
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}
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(Context::UnsafeFn(hir_id), Some(AllAllowedInUnsafeFn(lint_root))) => {
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UnusedUnsafe::InUnsafeFn(hir_id, lint_root)
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}
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(Context::UnsafeBlock(hir_id), Some(_)) => UnusedUnsafe::InUnsafeBlock(hir_id),
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};
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self.unused_unsafes.push((block.hir_id, unused_unsafe));
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}
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intravisit::walk_block(self, block);
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}
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fn visit_fn(
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&mut self,
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fk: intravisit::FnKind<'tcx>,
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_fd: &'tcx hir::FnDecl<'tcx>,
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b: hir::BodyId,
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_s: rustc_span::Span,
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_id: HirId,
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) {
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if matches!(fk, intravisit::FnKind::Closure) {
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|
self.visit_body(self.tcx.hir().body(b))
|
|
}
|
|
}
|
|
}
|
|
|
|
fn check_unused_unsafe(
|
|
tcx: TyCtxt<'_>,
|
|
def_id: LocalDefId,
|
|
used_unsafe_blocks: &FxHashMap<HirId, UsedUnsafeBlockData>,
|
|
) -> Vec<(HirId, UnusedUnsafe)> {
|
|
let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
|
|
let body_id = tcx.hir().maybe_body_owned_by(hir_id);
|
|
|
|
let Some(body_id) = body_id else {
|
|
debug!("check_unused_unsafe({:?}) - no body found", def_id);
|
|
return vec![];
|
|
};
|
|
let body = tcx.hir().body(body_id);
|
|
|
|
let context = match tcx.hir().fn_sig_by_hir_id(hir_id) {
|
|
Some(sig) if sig.header.unsafety == hir::Unsafety::Unsafe => Context::UnsafeFn(hir_id),
|
|
_ => Context::Safe,
|
|
};
|
|
|
|
debug!(
|
|
"check_unused_unsafe({:?}, context={:?}, body={:?}, used_unsafe_blocks={:?})",
|
|
def_id, body, context, used_unsafe_blocks
|
|
);
|
|
|
|
let mut unused_unsafes = vec![];
|
|
|
|
let mut visitor = UnusedUnsafeVisitor {
|
|
tcx,
|
|
used_unsafe_blocks,
|
|
context,
|
|
unused_unsafes: &mut unused_unsafes,
|
|
};
|
|
intravisit::Visitor::visit_body(&mut visitor, body);
|
|
|
|
unused_unsafes
|
|
}
|
|
|
|
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 mut checker = UnsafetyChecker::new(body, def.did, tcx, param_env);
|
|
checker.visit_body(&body);
|
|
|
|
let unused_unsafes = (!tcx.is_closure(def.did.to_def_id()))
|
|
.then(|| check_unused_unsafe(tcx, def.did, &checker.used_unsafe_blocks));
|
|
|
|
tcx.arena.alloc(UnsafetyCheckResult {
|
|
violations: checker.violations,
|
|
used_unsafe_blocks: checker.used_unsafe_blocks,
|
|
unused_unsafes,
|
|
})
|
|
}
|
|
|
|
fn report_unused_unsafe(tcx: TyCtxt<'_>, kind: UnusedUnsafe, id: 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);
|
|
match kind {
|
|
UnusedUnsafe::Unused => {}
|
|
UnusedUnsafe::InUnsafeBlock(id) => {
|
|
db.span_label(
|
|
tcx.sess.source_map().guess_head_span(tcx.hir().span(id)),
|
|
"because it's nested under this `unsafe` block",
|
|
);
|
|
}
|
|
UnusedUnsafe::InUnsafeFn(id, usage_lint_root) => {
|
|
db.span_label(
|
|
tcx.sess.source_map().guess_head_span(tcx.hir().span(id)),
|
|
"because it's nested under this `unsafe` fn",
|
|
)
|
|
.note(
|
|
"this `unsafe` block does contain unsafe operations, \
|
|
but those are already allowed in an `unsafe fn`",
|
|
);
|
|
let (level, source) =
|
|
tcx.lint_level_at_node(UNSAFE_OP_IN_UNSAFE_FN, usage_lint_root);
|
|
assert_eq!(level, Level::Allow);
|
|
lint::explain_lint_level_source(
|
|
UNSAFE_OP_IN_UNSAFE_FN,
|
|
Level::Allow,
|
|
source,
|
|
&mut db,
|
|
);
|
|
}
|
|
}
|
|
|
|
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, unused_unsafes, .. } = 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();
|
|
},
|
|
),
|
|
}
|
|
}
|
|
|
|
for &(block_id, kind) in unused_unsafes.as_ref().unwrap() {
|
|
report_unused_unsafe(tcx, kind, 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
|
|
}
|