1 //! Check the validity invariant of a given value, and tell the user
2 //! where in the value it got violated.
3 //! In const context, this goes even further and tries to approximate const safety.
4 //! That's useful because it means other passes (e.g. promotion) can rely on `const`s
7 use std::convert::TryFrom;
8 use std::fmt::{Display, Write};
9 use std::num::NonZeroUsize;
11 use rustc_ast::Mutability;
12 use rustc_data_structures::fx::FxHashSet;
14 use rustc_middle::mir::interpret::InterpError;
16 use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
17 use rustc_span::symbol::{sym, Symbol};
18 use rustc_target::abi::{Abi, Scalar as ScalarAbi, Size, VariantIdx, Variants, WrappingRange};
22 // for the validation errors
23 use super::UndefinedBehaviorInfo::*;
25 CheckInAllocMsg, GlobalAlloc, ImmTy, Immediate, InterpCx, InterpResult, MPlaceTy, Machine,
26 MemPlaceMeta, OpTy, Scalar, ValueVisitor,
29 macro_rules! throw_validation_failure {
30 ($where:expr, { $( $what_fmt:expr ),+ } $( expected { $( $expected_fmt:expr ),+ } )?) => {{
31 let mut msg = String::new();
32 msg.push_str("encountered ");
33 write!(&mut msg, $($what_fmt),+).unwrap();
35 msg.push_str(", but expected ");
36 write!(&mut msg, $($expected_fmt),+).unwrap();
38 let path = rustc_middle::ty::print::with_no_trimmed_paths!({
40 if !where_.is_empty() {
41 let mut path = String::new();
42 write_path(&mut path, where_);
48 throw_ub!(ValidationFailure { path, msg })
52 /// If $e throws an error matching the pattern, throw a validation failure.
53 /// Other errors are passed back to the caller, unchanged -- and if they reach the root of
54 /// the visitor, we make sure only validation errors and `InvalidProgram` errors are left.
55 /// This lets you use the patterns as a kind of validation list, asserting which errors
56 /// can possibly happen:
58 /// ```ignore(illustrative)
59 /// let v = try_validation!(some_fn(), some_path, {
60 /// Foo | Bar | Baz => { "some failure" },
64 /// The patterns must be of type `UndefinedBehaviorInfo`.
65 /// An additional expected parameter can also be added to the failure message:
67 /// ```ignore(illustrative)
68 /// let v = try_validation!(some_fn(), some_path, {
69 /// Foo | Bar | Baz => { "some failure" } expected { "something that wasn't a failure" },
73 /// An additional nicety is that both parameters actually take format args, so you can just write
74 /// the format string in directly:
76 /// ```ignore(illustrative)
77 /// let v = try_validation!(some_fn(), some_path, {
78 /// Foo | Bar | Baz => { "{:?}", some_failure } expected { "{}", expected_value },
82 macro_rules! try_validation {
83 ($e:expr, $where:expr,
84 $( $( $p:pat_param )|+ => { $( $what_fmt:expr ),+ } $( expected { $( $expected_fmt:expr ),+ } )? ),+ $(,)?
88 // We catch the error and turn it into a validation failure. We are okay with
89 // allocation here as this can only slow down builds that fail anyway.
90 Err(e) => match e.kind() {
92 InterpError::UndefinedBehavior($($p)|+) =>
93 throw_validation_failure!(
95 { $( $what_fmt ),+ } $( expected { $( $expected_fmt ),+ } )?
98 #[allow(unreachable_patterns)]
105 /// We want to show a nice path to the invalid field for diagnostics,
106 /// but avoid string operations in the happy case where no error happens.
107 /// So we track a `Vec<PathElem>` where `PathElem` contains all the data we
108 /// need to later print something for the user.
109 #[derive(Copy, Clone, Debug)]
113 GeneratorState(VariantIdx),
123 /// Extra things to check for during validation of CTFE results.
124 pub enum CtfeValidationMode {
125 /// Regular validation, nothing special happening.
127 /// Validation of a `const`.
128 /// `inner` says if this is an inner, indirect allocation (as opposed to the top-level const
129 /// allocation). Being an inner allocation makes a difference because the top-level allocation
130 /// of a `const` is copied for each use, but the inner allocations are implicitly shared.
131 /// `allow_static_ptrs` says if pointers to statics are permitted (which is the case for promoteds in statics).
132 Const { inner: bool, allow_static_ptrs: bool },
135 /// State for tracking recursive validation of references
136 pub struct RefTracking<T, PATH = ()> {
137 pub seen: FxHashSet<T>,
138 pub todo: Vec<(T, PATH)>,
141 impl<T: Copy + Eq + Hash + std::fmt::Debug, PATH: Default> RefTracking<T, PATH> {
142 pub fn empty() -> Self {
143 RefTracking { seen: FxHashSet::default(), todo: vec![] }
145 pub fn new(op: T) -> Self {
146 let mut ref_tracking_for_consts =
147 RefTracking { seen: FxHashSet::default(), todo: vec![(op, PATH::default())] };
148 ref_tracking_for_consts.seen.insert(op);
149 ref_tracking_for_consts
152 pub fn track(&mut self, op: T, path: impl FnOnce() -> PATH) {
153 if self.seen.insert(op) {
154 trace!("Recursing below ptr {:#?}", op);
156 // Remember to come back to this later.
157 self.todo.push((op, path));
163 fn write_path(out: &mut String, path: &[PathElem]) {
164 use self::PathElem::*;
166 for elem in path.iter() {
168 Field(name) => write!(out, ".{}", name),
169 EnumTag => write!(out, ".<enum-tag>"),
170 Variant(name) => write!(out, ".<enum-variant({})>", name),
171 GeneratorTag => write!(out, ".<generator-tag>"),
172 GeneratorState(idx) => write!(out, ".<generator-state({})>", idx.index()),
173 CapturedVar(name) => write!(out, ".<captured-var({})>", name),
174 TupleElem(idx) => write!(out, ".{}", idx),
175 ArrayElem(idx) => write!(out, "[{}]", idx),
176 // `.<deref>` does not match Rust syntax, but it is more readable for long paths -- and
177 // some of the other items here also are not Rust syntax. Actually we can't
178 // even use the usual syntax because we are just showing the projections,
180 Deref => write!(out, ".<deref>"),
181 DynDowncast => write!(out, ".<dyn-downcast>"),
187 // Formats such that a sentence like "expected something {}" to mean
188 // "expected something <in the given range>" makes sense.
189 fn wrapping_range_format(r: WrappingRange, max_hi: u128) -> String {
190 let WrappingRange { start: lo, end: hi } = r;
191 assert!(hi <= max_hi);
193 format!("less or equal to {}, or greater or equal to {}", hi, lo)
195 format!("equal to {}", lo)
197 assert!(hi < max_hi, "should not be printing if the range covers everything");
198 format!("less or equal to {}", hi)
199 } else if hi == max_hi {
200 assert!(lo > 0, "should not be printing if the range covers everything");
201 format!("greater or equal to {}", lo)
203 format!("in the range {:?}", r)
207 struct ValidityVisitor<'rt, 'mir, 'tcx, M: Machine<'mir, 'tcx>> {
208 /// The `path` may be pushed to, but the part that is present when a function
209 /// starts must not be changed! `visit_fields` and `visit_array` rely on
210 /// this stack discipline.
212 ref_tracking: Option<&'rt mut RefTracking<MPlaceTy<'tcx, M::Provenance>, Vec<PathElem>>>,
213 /// `None` indicates this is not validating for CTFE (but for runtime).
214 ctfe_mode: Option<CtfeValidationMode>,
215 ecx: &'rt InterpCx<'mir, 'tcx, M>,
218 impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, 'tcx, M> {
219 fn aggregate_field_path_elem(&mut self, layout: TyAndLayout<'tcx>, field: usize) -> PathElem {
220 // First, check if we are projecting to a variant.
221 match layout.variants {
222 Variants::Multiple { tag_field, .. } => {
223 if tag_field == field {
224 return match layout.ty.kind() {
225 ty::Adt(def, ..) if def.is_enum() => PathElem::EnumTag,
226 ty::Generator(..) => PathElem::GeneratorTag,
227 _ => bug!("non-variant type {:?}", layout.ty),
231 Variants::Single { .. } => {}
234 // Now we know we are projecting to a field, so figure out which one.
235 match layout.ty.kind() {
236 // generators and closures.
237 ty::Closure(def_id, _) | ty::Generator(def_id, _, _) => {
239 // FIXME this should be more descriptive i.e. CapturePlace instead of CapturedVar
240 // https://github.com/rust-lang/project-rfc-2229/issues/46
241 if let Some(local_def_id) = def_id.as_local() {
242 let tables = self.ecx.tcx.typeck(local_def_id);
243 if let Some(captured_place) =
244 tables.closure_min_captures_flattened(local_def_id).nth(field)
246 // Sometimes the index is beyond the number of upvars (seen
248 let var_hir_id = captured_place.get_root_variable();
249 let node = self.ecx.tcx.hir().get(var_hir_id);
250 if let hir::Node::Pat(pat) = node {
251 if let hir::PatKind::Binding(_, _, ident, _) = pat.kind {
252 name = Some(ident.name);
258 PathElem::CapturedVar(name.unwrap_or_else(|| {
259 // Fall back to showing the field index.
265 ty::Tuple(_) => PathElem::TupleElem(field),
268 ty::Adt(def, ..) if def.is_enum() => {
269 // we might be projecting *to* a variant, or to a field *in* a variant.
270 match layout.variants {
271 Variants::Single { index } => {
273 PathElem::Field(def.variant(index).fields[field].name)
275 Variants::Multiple { .. } => bug!("we handled variants above"),
280 ty::Adt(def, _) => PathElem::Field(def.non_enum_variant().fields[field].name),
283 ty::Array(..) | ty::Slice(..) => PathElem::ArrayElem(field),
286 ty::Dynamic(..) => PathElem::DynDowncast,
288 // nothing else has an aggregate layout
289 _ => bug!("aggregate_field_path_elem: got non-aggregate type {:?}", layout.ty),
296 f: impl FnOnce(&mut Self) -> InterpResult<'tcx, R>,
297 ) -> InterpResult<'tcx, R> {
298 // Remember the old state
299 let path_len = self.path.len();
300 // Record new element
301 self.path.push(elem);
305 self.path.truncate(path_len);
312 op: &OpTy<'tcx, M::Provenance>,
313 expected: impl Display,
314 ) -> InterpResult<'tcx, ImmTy<'tcx, M::Provenance>> {
316 self.ecx.read_immediate(op),
318 InvalidUninitBytes(None) => { "uninitialized memory" } expected { "{expected}" }
324 op: &OpTy<'tcx, M::Provenance>,
325 expected: impl Display,
326 ) -> InterpResult<'tcx, Scalar<M::Provenance>> {
327 Ok(self.read_immediate(op, expected)?.to_scalar())
330 fn check_wide_ptr_meta(
332 meta: MemPlaceMeta<M::Provenance>,
333 pointee: TyAndLayout<'tcx>,
334 ) -> InterpResult<'tcx> {
335 let tail = self.ecx.tcx.struct_tail_erasing_lifetimes(pointee.ty, self.ecx.param_env);
338 let vtable = meta.unwrap_meta().to_pointer(self.ecx)?;
339 // Make sure it is a genuine vtable pointer.
340 let (_ty, _trait) = try_validation!(
341 self.ecx.get_ptr_vtable(vtable),
343 DanglingIntPointer(..) |
344 InvalidVTablePointer(..) =>
345 { "{vtable}" } expected { "a vtable pointer" },
347 // FIXME: check if the type/trait match what ty::Dynamic says?
349 ty::Slice(..) | ty::Str => {
350 let _len = meta.unwrap_meta().to_machine_usize(self.ecx)?;
351 // We do not check that `len * elem_size <= isize::MAX`:
352 // that is only required for references, and there it falls out of the
353 // "dereferenceable" check performed by Stacked Borrows.
356 // Unsized, but not wide.
358 _ => bug!("Unexpected unsized type tail: {:?}", tail),
364 /// Check a reference or `Box`.
365 fn check_safe_pointer(
367 value: &OpTy<'tcx, M::Provenance>,
369 ) -> InterpResult<'tcx> {
371 self.ecx.ref_to_mplace(&self.read_immediate(value, format_args!("a {kind}"))?)?;
372 // Handle wide pointers.
373 // Check metadata early, for better diagnostics
374 if place.layout.is_unsized() {
375 self.check_wide_ptr_meta(place.meta, place.layout)?;
377 // Make sure this is dereferenceable and all.
378 let size_and_align = try_validation!(
379 self.ecx.size_and_align_of_mplace(&place),
381 InvalidMeta(msg) => { "invalid {} metadata: {}", kind, msg },
383 let (size, align) = size_and_align
384 // for the purpose of validity, consider foreign types to have
385 // alignment and size determined by the layout (size will be 0,
386 // alignment should take attributes into account).
387 .unwrap_or_else(|| (place.layout.size, place.layout.align.abi));
388 // Direct call to `check_ptr_access_align` checks alignment even on CTFE machines.
390 self.ecx.check_ptr_access_align(
394 CheckInAllocMsg::InboundsTest, // will anyway be replaced by validity message
397 AlignmentCheckFailed { required, has } =>
399 "an unaligned {kind} (required {} byte alignment but found {})",
403 DanglingIntPointer(0, _) =>
405 DanglingIntPointer(i, _) =>
406 { "a dangling {kind} (address {i:#x} is unallocated)" },
407 PointerOutOfBounds { .. } =>
408 { "a dangling {kind} (going beyond the bounds of its allocation)" },
409 // This cannot happen during const-eval (because interning already detects
410 // dangling pointers), but it can happen in Miri.
411 PointerUseAfterFree(..) =>
412 { "a dangling {kind} (use-after-free)" },
414 // Do not allow pointers to uninhabited types.
415 if place.layout.abi.is_uninhabited() {
416 throw_validation_failure!(self.path,
417 { "a {kind} pointing to uninhabited type {}", place.layout.ty }
420 // Recursive checking
421 if let Some(ref mut ref_tracking) = self.ref_tracking {
422 // Proceed recursively even for ZST, no reason to skip them!
423 // `!` is a ZST and we want to validate it.
424 if let Ok((alloc_id, _offset, _prov)) = self.ecx.ptr_try_get_alloc_id(place.ptr) {
425 // Let's see what kind of memory this points to.
426 let alloc_kind = self.ecx.tcx.try_get_global_alloc(alloc_id);
428 Some(GlobalAlloc::Static(did)) => {
429 // Special handling for pointers to statics (irrespective of their type).
430 assert!(!self.ecx.tcx.is_thread_local_static(did));
431 assert!(self.ecx.tcx.is_static(did));
434 Some(CtfeValidationMode::Const { allow_static_ptrs: false, .. })
436 // See const_eval::machine::MemoryExtra::can_access_statics for why
437 // this check is so important.
438 // This check is reachable when the const just referenced the static,
439 // but never read it (so we never entered `before_access_global`).
440 throw_validation_failure!(self.path,
441 { "a {} pointing to a static variable in a constant", kind }
444 // We skip recursively checking other statics. These statics must be sound by
445 // themselves, and the only way to get broken statics here is by using
447 // The reasons we don't check other statics is twofold. For one, in all
448 // sound cases, the static was already validated on its own, and second, we
449 // trigger cycle errors if we try to compute the value of the other static
450 // and that static refers back to us.
451 // We might miss const-invalid data,
452 // but things are still sound otherwise (in particular re: consts
453 // referring to statics).
456 Some(GlobalAlloc::Memory(alloc)) => {
457 if alloc.inner().mutability == Mutability::Mut
458 && matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { .. }))
460 // This should be unreachable, but if someone manages to copy a pointer
461 // out of a `static`, then that pointer might point to mutable memory,
462 // and we would catch that here.
463 throw_validation_failure!(self.path,
464 { "a {} pointing to mutable memory in a constant", kind }
468 // Nothing to check for these.
469 None | Some(GlobalAlloc::Function(..) | GlobalAlloc::VTable(..)) => {}
472 let path = &self.path;
473 ref_tracking.track(place, || {
474 // We need to clone the path anyway, make sure it gets created
475 // with enough space for the additional `Deref`.
476 let mut new_path = Vec::with_capacity(path.len() + 1);
477 new_path.extend(path);
478 new_path.push(PathElem::Deref);
485 /// Check if this is a value of primitive type, and if yes check the validity of the value
486 /// at that type. Return `true` if the type is indeed primitive.
487 fn try_visit_primitive(
489 value: &OpTy<'tcx, M::Provenance>,
490 ) -> InterpResult<'tcx, bool> {
491 // Go over all the primitive types
492 let ty = value.layout.ty;
495 let value = self.read_scalar(value, "a boolean")?;
500 { "{:x}", value } expected { "a boolean" },
505 let value = self.read_scalar(value, "a unicode scalar value")?;
510 { "{:x}", value } expected { "a valid unicode scalar value (in `0..=0x10FFFF` but not in `0xD800..=0xDFFF`)" },
514 ty::Float(_) | ty::Int(_) | ty::Uint(_) => {
515 // NOTE: Keep this in sync with the array optimization for int/float
517 let value = self.read_scalar(
519 if matches!(ty.kind(), ty::Float(..)) {
520 "a floating point number"
525 // As a special exception we *do* match on a `Scalar` here, since we truly want
526 // to know its underlying representation (and *not* cast it to an integer).
527 if matches!(value, Scalar::Ptr(..)) {
528 throw_validation_failure!(self.path,
529 { "{:x}", value } expected { "plain (non-pointer) bytes" }
535 // We are conservative with uninit for integers, but try to
536 // actually enforce the strict rules for raw pointers (mostly because
537 // that lets us re-use `ref_to_mplace`).
539 self.ecx.ref_to_mplace(&self.read_immediate(value, "a raw pointer")?)?;
540 if place.layout.is_unsized() {
541 self.check_wide_ptr_meta(place.meta, place.layout)?;
545 ty::Ref(_, ty, mutbl) => {
546 if matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { .. }))
547 && *mutbl == Mutability::Mut
549 // A mutable reference inside a const? That does not seem right (except if it is
551 let layout = self.ecx.layout_of(*ty)?;
552 if !layout.is_zst() {
553 throw_validation_failure!(self.path, { "mutable reference in a `const`" });
556 self.check_safe_pointer(value, "reference")?;
560 let value = self.read_scalar(value, "a function pointer")?;
562 // If we check references recursively, also check that this points to a function.
563 if let Some(_) = self.ref_tracking {
564 let ptr = value.to_pointer(self.ecx)?;
565 let _fn = try_validation!(
566 self.ecx.get_ptr_fn(ptr),
568 DanglingIntPointer(..) |
569 InvalidFunctionPointer(..) =>
570 { "{ptr}" } expected { "a function pointer" },
572 // FIXME: Check if the signature matches
574 // Otherwise (for standalone Miri), we have to still check it to be non-null.
575 if self.ecx.scalar_may_be_null(value)? {
576 throw_validation_failure!(self.path, { "a null function pointer" });
581 ty::Never => throw_validation_failure!(self.path, { "a value of the never type `!`" }),
582 ty::Foreign(..) | ty::FnDef(..) => {
586 // The above should be all the primitive types. The rest is compound, we
587 // check them by visiting their fields/variants.
595 | ty::Generator(..) => Ok(false),
596 // Some types only occur during typechecking, they have no layout.
597 // We should not see them here and we could not check them anyway.
600 | ty::Placeholder(..)
605 | ty::GeneratorWitness(..) => bug!("Encountered invalid type {:?}", ty),
611 scalar: Scalar<M::Provenance>,
612 scalar_layout: ScalarAbi,
613 ) -> InterpResult<'tcx> {
614 let size = scalar_layout.size(self.ecx);
615 let valid_range = scalar_layout.valid_range(self.ecx);
616 let WrappingRange { start, end } = valid_range;
617 let max_value = size.unsigned_int_max();
618 assert!(end <= max_value);
619 let bits = match scalar.try_to_int() {
620 Ok(int) => int.assert_bits(size),
622 // So this is a pointer then, and casting to an int failed.
623 // Can only happen during CTFE.
624 // We support 2 kinds of ranges here: full range, and excluding zero.
625 if start == 1 && end == max_value {
626 // Only null is the niche. So make sure the ptr is NOT null.
627 if self.ecx.scalar_may_be_null(scalar)? {
628 throw_validation_failure!(self.path,
629 { "a potentially null pointer" }
631 "something that cannot possibly fail to be {}",
632 wrapping_range_format(valid_range, max_value)
638 } else if scalar_layout.is_always_valid(self.ecx) {
639 // Easy. (This is reachable if `enforce_number_validity` is set.)
642 // Conservatively, we reject, because the pointer *could* have a bad
644 throw_validation_failure!(self.path,
647 "something that cannot possibly fail to be {}",
648 wrapping_range_format(valid_range, max_value)
655 if valid_range.contains(bits) {
658 throw_validation_failure!(self.path,
660 expected { "something {}", wrapping_range_format(valid_range, max_value) }
666 impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
667 for ValidityVisitor<'rt, 'mir, 'tcx, M>
669 type V = OpTy<'tcx, M::Provenance>;
672 fn ecx(&self) -> &InterpCx<'mir, 'tcx, M> {
676 fn read_discriminant(
678 op: &OpTy<'tcx, M::Provenance>,
679 ) -> InterpResult<'tcx, VariantIdx> {
680 self.with_elem(PathElem::EnumTag, move |this| {
682 this.ecx.read_discriminant(op),
685 { "{:x}", val } expected { "a valid enum tag" },
686 InvalidUninitBytes(None) =>
687 { "uninitialized bytes" } expected { "a valid enum tag" },
696 old_op: &OpTy<'tcx, M::Provenance>,
698 new_op: &OpTy<'tcx, M::Provenance>,
699 ) -> InterpResult<'tcx> {
700 let elem = self.aggregate_field_path_elem(old_op.layout, field);
701 self.with_elem(elem, move |this| this.visit_value(new_op))
707 old_op: &OpTy<'tcx, M::Provenance>,
708 variant_id: VariantIdx,
709 new_op: &OpTy<'tcx, M::Provenance>,
710 ) -> InterpResult<'tcx> {
711 let name = match old_op.layout.ty.kind() {
712 ty::Adt(adt, _) => PathElem::Variant(adt.variant(variant_id).name),
713 // Generators also have variants
714 ty::Generator(..) => PathElem::GeneratorState(variant_id),
715 _ => bug!("Unexpected type with variant: {:?}", old_op.layout.ty),
717 self.with_elem(name, move |this| this.visit_value(new_op))
723 op: &OpTy<'tcx, M::Provenance>,
724 _fields: NonZeroUsize,
725 ) -> InterpResult<'tcx> {
726 // Special check preventing `UnsafeCell` inside unions in the inner part of constants.
727 if matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { inner: true, .. })) {
728 if !op.layout.ty.is_freeze(*self.ecx.tcx, self.ecx.param_env) {
729 throw_validation_failure!(self.path, { "`UnsafeCell` in a `const`" });
736 fn visit_box(&mut self, op: &OpTy<'tcx, M::Provenance>) -> InterpResult<'tcx> {
737 self.check_safe_pointer(op, "box")?;
742 fn visit_value(&mut self, op: &OpTy<'tcx, M::Provenance>) -> InterpResult<'tcx> {
743 trace!("visit_value: {:?}, {:?}", *op, op.layout);
745 // Check primitive types -- the leaves of our recursive descent.
746 if self.try_visit_primitive(op)? {
750 // Special check preventing `UnsafeCell` in the inner part of constants
751 if let Some(def) = op.layout.ty.ty_adt_def() {
752 if matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { inner: true, .. }))
753 && def.is_unsafe_cell()
755 throw_validation_failure!(self.path, { "`UnsafeCell` in a `const`" });
759 // Recursively walk the value at its type.
760 self.walk_value(op)?;
762 // *After* all of this, check the ABI. We need to check the ABI to handle
763 // types like `NonNull` where the `Scalar` info is more restrictive than what
764 // the fields say (`rustc_layout_scalar_valid_range_start`).
765 // But in most cases, this will just propagate what the fields say,
766 // and then we want the error to point at the field -- so, first recurse,
769 // FIXME: We could avoid some redundant checks here. For newtypes wrapping
770 // scalars, we do the same check on every "level" (e.g., first we check
771 // MyNewtype and then the scalar in there).
772 match op.layout.abi {
773 Abi::Uninhabited => {
774 throw_validation_failure!(self.path,
775 { "a value of uninhabited type {:?}", op.layout.ty }
778 Abi::Scalar(scalar_layout) => {
779 if !scalar_layout.is_uninit_valid() {
780 // There is something to check here.
781 let scalar = self.read_scalar(op, "initiailized scalar value")?;
782 self.visit_scalar(scalar, scalar_layout)?;
785 Abi::ScalarPair(a_layout, b_layout) => {
786 // There is no `rustc_layout_scalar_valid_range_start` for pairs, so
787 // we would validate these things as we descend into the fields,
788 // but that can miss bugs in layout computation. Layout computation
789 // is subtle due to enums having ScalarPair layout, where one field
790 // is the discriminant.
791 if cfg!(debug_assertions)
792 && !a_layout.is_uninit_valid()
793 && !b_layout.is_uninit_valid()
795 // We can only proceed if *both* scalars need to be initialized.
796 // FIXME: find a way to also check ScalarPair when one side can be uninit but
797 // the other must be init.
799 self.read_immediate(op, "initiailized scalar value")?.to_scalar_pair();
800 self.visit_scalar(a, a_layout)?;
801 self.visit_scalar(b, b_layout)?;
804 Abi::Vector { .. } => {
805 // No checks here, we assume layout computation gets this right.
806 // (This is harder to check since Miri does not represent these as `Immediate`. We
807 // also cannot use field projections since this might be a newtype around a vector.)
809 Abi::Aggregate { .. } => {
819 op: &OpTy<'tcx, M::Provenance>,
820 fields: impl Iterator<Item = InterpResult<'tcx, Self::V>>,
821 ) -> InterpResult<'tcx> {
822 match op.layout.ty.kind() {
824 let mplace = op.assert_mem_place(); // strings are unsized and hence never immediate
825 let len = mplace.len(self.ecx)?;
827 self.ecx.read_bytes_ptr_strip_provenance(mplace.ptr, Size::from_bytes(len)),
829 InvalidUninitBytes(..) => { "uninitialized data in `str`" },
832 ty::Array(tys, ..) | ty::Slice(tys)
833 // This optimization applies for types that can hold arbitrary bytes (such as
834 // integer and floating point types) or for structs or tuples with no fields.
835 // FIXME(wesleywiser) This logic could be extended further to arbitrary structs
836 // or tuples made up of integer/floating point types or inhabited ZSTs with no
838 if matches!(tys.kind(), ty::Int(..) | ty::Uint(..) | ty::Float(..))
841 // Optimized handling for arrays of integer/float type.
843 // This is the length of the array/slice.
844 let len = op.len(self.ecx)?;
845 // This is the element type size.
846 let layout = self.ecx.layout_of(*tys)?;
847 // This is the size in bytes of the whole array. (This checks for overflow.)
848 let size = layout.size * len;
849 // If the size is 0, there is nothing to check.
850 // (`size` can only be 0 of `len` is 0, and empty arrays are always valid.)
851 if size == Size::ZERO {
854 // Now that we definitely have a non-ZST array, we know it lives in memory.
855 let mplace = match op.try_as_mplace() {
856 Ok(mplace) => mplace,
857 Err(imm) => match *imm {
859 throw_validation_failure!(self.path, { "uninitialized bytes" }),
860 Immediate::Scalar(..) | Immediate::ScalarPair(..) =>
861 bug!("arrays/slices can never have Scalar/ScalarPair layout"),
865 // Optimization: we just check the entire range at once.
866 // NOTE: Keep this in sync with the handling of integer and float
867 // types above, in `visit_primitive`.
868 // In run-time mode, we accept pointers in here. This is actually more
869 // permissive than a per-element check would be, e.g., we accept
870 // a &[u8] that contains a pointer even though bytewise checking would
871 // reject it. However, that's good: We don't inherently want
872 // to reject those pointers, we just do not have the machinery to
873 // talk about parts of a pointer.
874 // We also accept uninit, for consistency with the slow path.
875 let alloc = self.ecx.get_ptr_alloc(mplace.ptr, size, mplace.align)?.expect("we already excluded size 0");
877 match alloc.get_bytes_strip_provenance() {
878 // In the happy case, we needn't check anything else.
880 // Some error happened, try to provide a more detailed description.
882 // For some errors we might be able to provide extra information.
883 // (This custom logic does not fit the `try_validation!` macro.)
885 err_ub!(InvalidUninitBytes(Some((_alloc_id, access)))) => {
886 // Some byte was uninitialized, determine which
887 // element that byte belongs to so we can
889 let i = usize::try_from(
890 access.uninit.start.bytes() / layout.size.bytes(),
893 self.path.push(PathElem::ArrayElem(i));
895 throw_validation_failure!(self.path, { "uninitialized bytes" })
898 // Propagate upwards (that will also check for unexpected errors).
899 _ => return Err(err),
904 // Fast path for arrays and slices of ZSTs. We only need to check a single ZST element
905 // of an array and not all of them, because there's only a single value of a specific
906 // ZST type, so either validation fails for all elements or none.
907 ty::Array(tys, ..) | ty::Slice(tys) if self.ecx.layout_of(*tys)?.is_zst() => {
908 // Validate just the first element (if any).
909 self.walk_aggregate(op, fields.take(1))?
912 self.walk_aggregate(op, fields)? // default handler
919 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
920 fn validate_operand_internal(
922 op: &OpTy<'tcx, M::Provenance>,
924 ref_tracking: Option<&mut RefTracking<MPlaceTy<'tcx, M::Provenance>, Vec<PathElem>>>,
925 ctfe_mode: Option<CtfeValidationMode>,
926 ) -> InterpResult<'tcx> {
927 trace!("validate_operand_internal: {:?}, {:?}", *op, op.layout.ty);
929 // Construct a visitor
930 let mut visitor = ValidityVisitor { path, ref_tracking, ctfe_mode, ecx: self };
933 match visitor.visit_value(&op) {
935 // Pass through validation failures.
936 Err(err) if matches!(err.kind(), err_ub!(ValidationFailure { .. })) => Err(err),
937 // Complain about any other kind of UB error -- those are bad because we'd like to
938 // report them in a way that shows *where* in the value the issue lies.
939 Err(err) if matches!(err.kind(), InterpError::UndefinedBehavior(_)) => {
940 err.print_backtrace();
941 bug!("Unexpected Undefined Behavior error during validation: {}", err);
943 // Pass through everything else.
944 Err(err) => Err(err),
948 /// This function checks the data at `op` to be const-valid.
949 /// `op` is assumed to cover valid memory if it is an indirect operand.
950 /// It will error if the bits at the destination do not match the ones described by the layout.
952 /// `ref_tracking` is used to record references that we encounter so that they
953 /// can be checked recursively by an outside driving loop.
955 /// `constant` controls whether this must satisfy the rules for constants:
956 /// - no pointers to statics.
957 /// - no `UnsafeCell` or non-ZST `&mut`.
959 pub fn const_validate_operand(
961 op: &OpTy<'tcx, M::Provenance>,
963 ref_tracking: &mut RefTracking<MPlaceTy<'tcx, M::Provenance>, Vec<PathElem>>,
964 ctfe_mode: CtfeValidationMode,
965 ) -> InterpResult<'tcx> {
966 self.validate_operand_internal(op, path, Some(ref_tracking), Some(ctfe_mode))
969 /// This function checks the data at `op` to be runtime-valid.
970 /// `op` is assumed to cover valid memory if it is an indirect operand.
971 /// It will error if the bits at the destination do not match the ones described by the layout.
973 pub fn validate_operand(&self, op: &OpTy<'tcx, M::Provenance>) -> InterpResult<'tcx> {
974 // Note that we *could* actually be in CTFE here with `-Zextra-const-ub-checks`, but it's
975 // still correct to not use `ctfe_mode`: that mode is for validation of the final constant
976 // value, it rules out things like `UnsafeCell` in awkward places. It also can make checking
977 // recurse through references which, for now, we don't want here, either.
978 self.validate_operand_internal(op, vec![], None, None)