rustc_const_eval/interpret/validity.rs
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
5//! to be const-safe.
6
7use std::borrow::Cow;
8use std::fmt::Write;
9use std::hash::Hash;
10use std::num::NonZero;
11
12use either::{Left, Right};
13use hir::def::DefKind;
14use rustc_abi::{
15 BackendRepr, FieldIdx, FieldsShape, Scalar as ScalarAbi, Size, VariantIdx, Variants,
16 WrappingRange,
17};
18use rustc_ast::Mutability;
19use rustc_data_structures::fx::FxHashSet;
20use rustc_hir as hir;
21use rustc_middle::bug;
22use rustc_middle::mir::interpret::ValidationErrorKind::{self, *};
23use rustc_middle::mir::interpret::{
24 ExpectedKind, InterpErrorKind, InvalidMetaKind, Misalignment, PointerKind, Provenance,
25 UnsupportedOpInfo, ValidationErrorInfo, alloc_range, interp_ok,
26};
27use rustc_middle::ty::layout::{LayoutCx, TyAndLayout};
28use rustc_middle::ty::{self, Ty};
29use rustc_span::{Symbol, sym};
30use tracing::trace;
31
32use super::machine::AllocMap;
33use super::{
34 AllocId, CheckInAllocMsg, GlobalAlloc, ImmTy, Immediate, InterpCx, InterpResult, MPlaceTy,
35 Machine, MemPlaceMeta, PlaceTy, Pointer, Projectable, Scalar, ValueVisitor, err_ub,
36 format_interp_error,
37};
38use crate::enter_trace_span;
39
40// for the validation errors
41#[rustfmt::skip]
42use super::InterpErrorKind::UndefinedBehavior as Ub;
43use super::InterpErrorKind::Unsupported as Unsup;
44use super::UndefinedBehaviorInfo::*;
45use super::UnsupportedOpInfo::*;
46
47macro_rules! err_validation_failure {
48 ($where:expr, $kind: expr) => {{
49 let where_ = &$where;
50 let path = if !where_.is_empty() {
51 let mut path = String::new();
52 write_path(&mut path, where_);
53 Some(path)
54 } else {
55 None
56 };
57
58 err_ub!(ValidationError(ValidationErrorInfo { path, kind: $kind }))
59 }};
60}
61
62macro_rules! throw_validation_failure {
63 ($where:expr, $kind: expr) => {
64 do yeet err_validation_failure!($where, $kind)
65 };
66}
67
68/// If $e throws an error matching the pattern, throw a validation failure.
69/// Other errors are passed back to the caller, unchanged -- and if they reach the root of
70/// the visitor, we make sure only validation errors and `InvalidProgram` errors are left.
71/// This lets you use the patterns as a kind of validation list, asserting which errors
72/// can possibly happen:
73///
74/// ```ignore(illustrative)
75/// let v = try_validation!(some_fn(), some_path, {
76/// Foo | Bar | Baz => { "some failure" },
77/// });
78/// ```
79///
80/// The patterns must be of type `UndefinedBehaviorInfo`.
81/// An additional expected parameter can also be added to the failure message:
82///
83/// ```ignore(illustrative)
84/// let v = try_validation!(some_fn(), some_path, {
85/// Foo | Bar | Baz => { "some failure" } expected { "something that wasn't a failure" },
86/// });
87/// ```
88///
89/// An additional nicety is that both parameters actually take format args, so you can just write
90/// the format string in directly:
91///
92/// ```ignore(illustrative)
93/// let v = try_validation!(some_fn(), some_path, {
94/// Foo | Bar | Baz => { "{:?}", some_failure } expected { "{}", expected_value },
95/// });
96/// ```
97///
98macro_rules! try_validation {
99 ($e:expr, $where:expr,
100 $( $( $p:pat_param )|+ => $kind: expr ),+ $(,)?
101 ) => {{
102 $e.map_err_kind(|e| {
103 // We catch the error and turn it into a validation failure. We are okay with
104 // allocation here as this can only slow down builds that fail anyway.
105 match e {
106 $(
107 $($p)|+ => {
108 err_validation_failure!(
109 $where,
110 $kind
111 )
112 }
113 ),+,
114 e => e,
115 }
116 })?
117 }};
118}
119
120/// We want to show a nice path to the invalid field for diagnostics,
121/// but avoid string operations in the happy case where no error happens.
122/// So we track a `Vec<PathElem>` where `PathElem` contains all the data we
123/// need to later print something for the user.
124#[derive(Copy, Clone, Debug)]
125pub enum PathElem {
126 Field(Symbol),
127 Variant(Symbol),
128 CoroutineState(VariantIdx),
129 CapturedVar(Symbol),
130 ArrayElem(usize),
131 TupleElem(usize),
132 Deref,
133 EnumTag,
134 CoroutineTag,
135 DynDowncast,
136 Vtable,
137}
138
139/// Extra things to check for during validation of CTFE results.
140#[derive(Copy, Clone)]
141pub enum CtfeValidationMode {
142 /// Validation of a `static`
143 Static { mutbl: Mutability },
144 /// Validation of a promoted.
145 Promoted,
146 /// Validation of a `const`.
147 /// `allow_immutable_unsafe_cell` says whether we allow `UnsafeCell` in immutable memory (which is the
148 /// case for the top-level allocation of a `const`, where this is fine because the allocation will be
149 /// copied at each use site).
150 Const { allow_immutable_unsafe_cell: bool },
151}
152
153impl CtfeValidationMode {
154 fn allow_immutable_unsafe_cell(self) -> bool {
155 match self {
156 CtfeValidationMode::Static { .. } => false,
157 CtfeValidationMode::Promoted { .. } => false,
158 CtfeValidationMode::Const { allow_immutable_unsafe_cell, .. } => {
159 allow_immutable_unsafe_cell
160 }
161 }
162 }
163}
164
165/// State for tracking recursive validation of references
166pub struct RefTracking<T, PATH = ()> {
167 seen: FxHashSet<T>,
168 todo: Vec<(T, PATH)>,
169}
170
171impl<T: Clone + Eq + Hash + std::fmt::Debug, PATH: Default> RefTracking<T, PATH> {
172 pub fn empty() -> Self {
173 RefTracking { seen: FxHashSet::default(), todo: vec![] }
174 }
175 pub fn new(val: T) -> Self {
176 let mut ref_tracking_for_consts =
177 RefTracking { seen: FxHashSet::default(), todo: vec![(val.clone(), PATH::default())] };
178 ref_tracking_for_consts.seen.insert(val);
179 ref_tracking_for_consts
180 }
181 pub fn next(&mut self) -> Option<(T, PATH)> {
182 self.todo.pop()
183 }
184
185 fn track(&mut self, val: T, path: impl FnOnce() -> PATH) {
186 if self.seen.insert(val.clone()) {
187 trace!("Recursing below ptr {:#?}", val);
188 let path = path();
189 // Remember to come back to this later.
190 self.todo.push((val, path));
191 }
192 }
193}
194
195// FIXME make this translatable as well?
196/// Format a path
197fn write_path(out: &mut String, path: &[PathElem]) {
198 use self::PathElem::*;
199
200 for elem in path.iter() {
201 match elem {
202 Field(name) => write!(out, ".{name}"),
203 EnumTag => write!(out, ".<enum-tag>"),
204 Variant(name) => write!(out, ".<enum-variant({name})>"),
205 CoroutineTag => write!(out, ".<coroutine-tag>"),
206 CoroutineState(idx) => write!(out, ".<coroutine-state({})>", idx.index()),
207 CapturedVar(name) => write!(out, ".<captured-var({name})>"),
208 TupleElem(idx) => write!(out, ".{idx}"),
209 ArrayElem(idx) => write!(out, "[{idx}]"),
210 // `.<deref>` does not match Rust syntax, but it is more readable for long paths -- and
211 // some of the other items here also are not Rust syntax. Actually we can't
212 // even use the usual syntax because we are just showing the projections,
213 // not the root.
214 Deref => write!(out, ".<deref>"),
215 DynDowncast => write!(out, ".<dyn-downcast>"),
216 Vtable => write!(out, ".<vtable>"),
217 }
218 .unwrap()
219 }
220}
221
222/// Represents a set of `Size` values as a sorted list of ranges.
223// These are (offset, length) pairs, and they are sorted and mutually disjoint,
224// and never adjacent (i.e. there's always a gap between two of them).
225#[derive(Debug, Clone)]
226pub struct RangeSet(Vec<(Size, Size)>);
227
228impl RangeSet {
229 fn add_range(&mut self, offset: Size, size: Size) {
230 if size.bytes() == 0 {
231 // No need to track empty ranges.
232 return;
233 }
234 let v = &mut self.0;
235 // We scan for a partition point where the left partition is all the elements that end
236 // strictly before we start. Those are elements that are too "low" to merge with us.
237 let idx =
238 v.partition_point(|&(other_offset, other_size)| other_offset + other_size < offset);
239 // Now we want to either merge with the first element of the second partition, or insert ourselves before that.
240 if let Some(&(other_offset, other_size)) = v.get(idx)
241 && offset + size >= other_offset
242 {
243 // Their end is >= our start (otherwise it would not be in the 2nd partition) and
244 // our end is >= their start. This means we can merge the ranges.
245 let new_start = other_offset.min(offset);
246 let mut new_end = (other_offset + other_size).max(offset + size);
247 // We grew to the right, so merge with overlapping/adjacent elements.
248 // (We also may have grown to the left, but that can never make us adjacent with
249 // anything there since we selected the first such candidate via `partition_point`.)
250 let mut scan_right = 1;
251 while let Some(&(next_offset, next_size)) = v.get(idx + scan_right)
252 && new_end >= next_offset
253 {
254 // Increase our size to absorb the next element.
255 new_end = new_end.max(next_offset + next_size);
256 // Look at the next element.
257 scan_right += 1;
258 }
259 // Update the element we grew.
260 v[idx] = (new_start, new_end - new_start);
261 // Remove the elements we absorbed (if any).
262 if scan_right > 1 {
263 drop(v.drain((idx + 1)..(idx + scan_right)));
264 }
265 } else {
266 // Insert new element.
267 v.insert(idx, (offset, size));
268 }
269 }
270}
271
272struct ValidityVisitor<'rt, 'tcx, M: Machine<'tcx>> {
273 /// The `path` may be pushed to, but the part that is present when a function
274 /// starts must not be changed! `visit_fields` and `visit_array` rely on
275 /// this stack discipline.
276 path: Vec<PathElem>,
277 ref_tracking: Option<&'rt mut RefTracking<MPlaceTy<'tcx, M::Provenance>, Vec<PathElem>>>,
278 /// `None` indicates this is not validating for CTFE (but for runtime).
279 ctfe_mode: Option<CtfeValidationMode>,
280 ecx: &'rt mut InterpCx<'tcx, M>,
281 /// Whether provenance should be reset outside of pointers (emulating the effect of a typed
282 /// copy).
283 reset_provenance_and_padding: bool,
284 /// This tracks which byte ranges in this value contain data; the remaining bytes are padding.
285 /// The ideal representation here would be pointer-length pairs, but to keep things more compact
286 /// we only store a (range) set of offsets -- the base pointer is the same throughout the entire
287 /// visit, after all.
288 /// If this is `Some`, then `reset_provenance_and_padding` must be true (but not vice versa:
289 /// we might not track data vs padding bytes if the operand isn't stored in memory anyway).
290 data_bytes: Option<RangeSet>,
291}
292
293impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
294 fn aggregate_field_path_elem(&mut self, layout: TyAndLayout<'tcx>, field: usize) -> PathElem {
295 // First, check if we are projecting to a variant.
296 match layout.variants {
297 Variants::Multiple { tag_field, .. } => {
298 if tag_field.as_usize() == field {
299 return match layout.ty.kind() {
300 ty::Adt(def, ..) if def.is_enum() => PathElem::EnumTag,
301 ty::Coroutine(..) => PathElem::CoroutineTag,
302 _ => bug!("non-variant type {:?}", layout.ty),
303 };
304 }
305 }
306 Variants::Single { .. } | Variants::Empty => {}
307 }
308
309 // Now we know we are projecting to a field, so figure out which one.
310 match layout.ty.kind() {
311 // coroutines, closures, and coroutine-closures all have upvars that may be named.
312 ty::Closure(def_id, _) | ty::Coroutine(def_id, _) | ty::CoroutineClosure(def_id, _) => {
313 let mut name = None;
314 // FIXME this should be more descriptive i.e. CapturePlace instead of CapturedVar
315 // https://github.com/rust-lang/project-rfc-2229/issues/46
316 if let Some(local_def_id) = def_id.as_local() {
317 let captures = self.ecx.tcx.closure_captures(local_def_id);
318 if let Some(captured_place) = captures.get(field) {
319 // Sometimes the index is beyond the number of upvars (seen
320 // for a coroutine).
321 let var_hir_id = captured_place.get_root_variable();
322 let node = self.ecx.tcx.hir_node(var_hir_id);
323 if let hir::Node::Pat(pat) = node
324 && let hir::PatKind::Binding(_, _, ident, _) = pat.kind
325 {
326 name = Some(ident.name);
327 }
328 }
329 }
330
331 PathElem::CapturedVar(name.unwrap_or_else(|| {
332 // Fall back to showing the field index.
333 sym::integer(field)
334 }))
335 }
336
337 // tuples
338 ty::Tuple(_) => PathElem::TupleElem(field),
339
340 // enums
341 ty::Adt(def, ..) if def.is_enum() => {
342 // we might be projecting *to* a variant, or to a field *in* a variant.
343 match layout.variants {
344 Variants::Single { index } => {
345 // Inside a variant
346 PathElem::Field(def.variant(index).fields[FieldIdx::from_usize(field)].name)
347 }
348 Variants::Empty => panic!("there is no field in Variants::Empty types"),
349 Variants::Multiple { .. } => bug!("we handled variants above"),
350 }
351 }
352
353 // other ADTs
354 ty::Adt(def, _) => {
355 PathElem::Field(def.non_enum_variant().fields[FieldIdx::from_usize(field)].name)
356 }
357
358 // arrays/slices
359 ty::Array(..) | ty::Slice(..) => PathElem::ArrayElem(field),
360
361 // dyn traits
362 ty::Dynamic(..) => {
363 assert_eq!(field, 0);
364 PathElem::DynDowncast
365 }
366
367 // nothing else has an aggregate layout
368 _ => bug!("aggregate_field_path_elem: got non-aggregate type {:?}", layout.ty),
369 }
370 }
371
372 fn with_elem<R>(
373 &mut self,
374 elem: PathElem,
375 f: impl FnOnce(&mut Self) -> InterpResult<'tcx, R>,
376 ) -> InterpResult<'tcx, R> {
377 // Remember the old state
378 let path_len = self.path.len();
379 // Record new element
380 self.path.push(elem);
381 // Perform operation
382 let r = f(self)?;
383 // Undo changes
384 self.path.truncate(path_len);
385 // Done
386 interp_ok(r)
387 }
388
389 fn read_immediate(
390 &self,
391 val: &PlaceTy<'tcx, M::Provenance>,
392 expected: ExpectedKind,
393 ) -> InterpResult<'tcx, ImmTy<'tcx, M::Provenance>> {
394 interp_ok(try_validation!(
395 self.ecx.read_immediate(val),
396 self.path,
397 Ub(InvalidUninitBytes(_)) =>
398 Uninit { expected },
399 // The `Unsup` cases can only occur during CTFE
400 Unsup(ReadPointerAsInt(_)) =>
401 PointerAsInt { expected },
402 Unsup(ReadPartialPointer(_)) =>
403 PartialPointer,
404 ))
405 }
406
407 fn read_scalar(
408 &self,
409 val: &PlaceTy<'tcx, M::Provenance>,
410 expected: ExpectedKind,
411 ) -> InterpResult<'tcx, Scalar<M::Provenance>> {
412 interp_ok(self.read_immediate(val, expected)?.to_scalar())
413 }
414
415 fn deref_pointer(
416 &mut self,
417 val: &PlaceTy<'tcx, M::Provenance>,
418 expected: ExpectedKind,
419 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
420 // Not using `ecx.deref_pointer` since we want to use our `read_immediate` wrapper.
421 let imm = self.read_immediate(val, expected)?;
422 // Reset provenance: ensure slice tail metadata does not preserve provenance,
423 // and ensure all pointers do not preserve partial provenance.
424 if self.reset_provenance_and_padding {
425 if matches!(imm.layout.backend_repr, BackendRepr::Scalar(..)) {
426 // A thin pointer. If it has provenance, we don't have to do anything.
427 // If it does not, ensure we clear the provenance in memory.
428 if matches!(imm.to_scalar(), Scalar::Int(..)) {
429 self.ecx.clear_provenance(val)?;
430 }
431 } else {
432 // A wide pointer. This means we have to worry both about the pointer itself and the
433 // metadata. We do the lazy thing and just write back the value we got. Just
434 // clearing provenance in a targeted manner would be more efficient, but unless this
435 // is a perf hotspot it's just not worth the effort.
436 self.ecx.write_immediate_no_validate(*imm, val)?;
437 }
438 // The entire thing is data, not padding.
439 self.add_data_range_place(val);
440 }
441 // Now turn it into a place.
442 self.ecx.ref_to_mplace(&imm)
443 }
444
445 fn check_wide_ptr_meta(
446 &mut self,
447 meta: MemPlaceMeta<M::Provenance>,
448 pointee: TyAndLayout<'tcx>,
449 ) -> InterpResult<'tcx> {
450 let tail = self.ecx.tcx.struct_tail_for_codegen(pointee.ty, self.ecx.typing_env);
451 match tail.kind() {
452 ty::Dynamic(data, _) => {
453 let vtable = meta.unwrap_meta().to_pointer(self.ecx)?;
454 // Make sure it is a genuine vtable pointer for the right trait.
455 try_validation!(
456 self.ecx.get_ptr_vtable_ty(vtable, Some(data)),
457 self.path,
458 Ub(DanglingIntPointer{ .. } | InvalidVTablePointer(..)) =>
459 InvalidVTablePtr { value: format!("{vtable}") },
460 Ub(InvalidVTableTrait { vtable_dyn_type, expected_dyn_type }) => {
461 InvalidMetaWrongTrait { vtable_dyn_type, expected_dyn_type }
462 },
463 );
464 }
465 ty::Slice(..) | ty::Str => {
466 let _len = meta.unwrap_meta().to_target_usize(self.ecx)?;
467 // We do not check that `len * elem_size <= isize::MAX`:
468 // that is only required for references, and there it falls out of the
469 // "dereferenceable" check performed by Stacked Borrows.
470 }
471 ty::Foreign(..) => {
472 // Unsized, but not wide.
473 }
474 _ => bug!("Unexpected unsized type tail: {:?}", tail),
475 }
476
477 interp_ok(())
478 }
479
480 /// Check a reference or `Box`.
481 fn check_safe_pointer(
482 &mut self,
483 value: &PlaceTy<'tcx, M::Provenance>,
484 ptr_kind: PointerKind,
485 ) -> InterpResult<'tcx> {
486 let place = self.deref_pointer(value, ptr_kind.into())?;
487 // Handle wide pointers.
488 // Check metadata early, for better diagnostics
489 if place.layout.is_unsized() {
490 self.check_wide_ptr_meta(place.meta(), place.layout)?;
491 }
492 // Make sure this is dereferenceable and all.
493 let size_and_align = try_validation!(
494 self.ecx.size_and_align_of_val(&place),
495 self.path,
496 Ub(InvalidMeta(msg)) => match msg {
497 InvalidMetaKind::SliceTooBig => InvalidMetaSliceTooLarge { ptr_kind },
498 InvalidMetaKind::TooBig => InvalidMetaTooLarge { ptr_kind },
499 }
500 );
501 let (size, align) = size_and_align
502 // for the purpose of validity, consider foreign types to have
503 // alignment and size determined by the layout (size will be 0,
504 // alignment should take attributes into account).
505 .unwrap_or_else(|| (place.layout.size, place.layout.align.abi));
506 // Direct call to `check_ptr_access_align` checks alignment even on CTFE machines.
507 try_validation!(
508 self.ecx.check_ptr_access(
509 place.ptr(),
510 size,
511 CheckInAllocMsg::Dereferenceable, // will anyway be replaced by validity message
512 ),
513 self.path,
514 Ub(DanglingIntPointer { addr: 0, .. }) => NullPtr { ptr_kind, maybe: false },
515 Ub(DanglingIntPointer { addr: i, .. }) => DanglingPtrNoProvenance {
516 ptr_kind,
517 // FIXME this says "null pointer" when null but we need translate
518 pointer: format!("{}", Pointer::<Option<AllocId>>::without_provenance(i))
519 },
520 Ub(PointerOutOfBounds { .. }) => DanglingPtrOutOfBounds {
521 ptr_kind
522 },
523 Ub(PointerUseAfterFree(..)) => DanglingPtrUseAfterFree {
524 ptr_kind,
525 },
526 );
527 try_validation!(
528 self.ecx.check_ptr_align(
529 place.ptr(),
530 align,
531 ),
532 self.path,
533 Ub(AlignmentCheckFailed(Misalignment { required, has }, _msg)) => UnalignedPtr {
534 ptr_kind,
535 required_bytes: required.bytes(),
536 found_bytes: has.bytes()
537 },
538 );
539 // Make sure this is non-null. We checked dereferenceability above, but if `size` is zero
540 // that does not imply non-null.
541 let scalar = Scalar::from_maybe_pointer(place.ptr(), self.ecx);
542 if self.ecx.scalar_may_be_null(scalar)? {
543 let maybe = !M::Provenance::OFFSET_IS_ADDR && matches!(scalar, Scalar::Ptr(..));
544 throw_validation_failure!(self.path, NullPtr { ptr_kind, maybe })
545 }
546 // Do not allow references to uninhabited types.
547 if place.layout.is_uninhabited() {
548 let ty = place.layout.ty;
549 throw_validation_failure!(self.path, PtrToUninhabited { ptr_kind, ty })
550 }
551 // Recursive checking
552 if let Some(ref_tracking) = self.ref_tracking.as_deref_mut() {
553 // Proceed recursively even for ZST, no reason to skip them!
554 // `!` is a ZST and we want to validate it.
555 if let Some(ctfe_mode) = self.ctfe_mode {
556 let mut skip_recursive_check = false;
557 // CTFE imposes restrictions on what references can point to.
558 if let Ok((alloc_id, _offset, _prov)) =
559 self.ecx.ptr_try_get_alloc_id(place.ptr(), 0)
560 {
561 // Everything should be already interned.
562 let Some(global_alloc) = self.ecx.tcx.try_get_global_alloc(alloc_id) else {
563 if self.ecx.memory.alloc_map.contains_key(&alloc_id) {
564 // This can happen when interning didn't complete due to, e.g.
565 // missing `make_global`. This must mean other errors are already
566 // being reported.
567 self.ecx.tcx.dcx().delayed_bug(
568 "interning did not complete, there should be an error",
569 );
570 return interp_ok(());
571 }
572 // We can't have *any* references to non-existing allocations in const-eval
573 // as the rest of rustc isn't happy with them... so we throw an error, even
574 // though for zero-sized references this isn't really UB.
575 // A potential future alternative would be to resurrect this as a zero-sized allocation
576 // (which codegen will then compile to an aligned dummy pointer anyway).
577 throw_validation_failure!(self.path, DanglingPtrUseAfterFree { ptr_kind });
578 };
579 let (size, _align) =
580 global_alloc.size_and_align(*self.ecx.tcx, self.ecx.typing_env);
581 let alloc_actual_mutbl =
582 global_alloc.mutability(*self.ecx.tcx, self.ecx.typing_env);
583
584 match global_alloc {
585 GlobalAlloc::Static(did) => {
586 let DefKind::Static { nested, .. } = self.ecx.tcx.def_kind(did) else {
587 bug!()
588 };
589 assert!(!self.ecx.tcx.is_thread_local_static(did));
590 assert!(self.ecx.tcx.is_static(did));
591 match ctfe_mode {
592 CtfeValidationMode::Static { .. }
593 | CtfeValidationMode::Promoted { .. } => {
594 // We skip recursively checking other statics. These statics must be sound by
595 // themselves, and the only way to get broken statics here is by using
596 // unsafe code.
597 // The reasons we don't check other statics is twofold. For one, in all
598 // sound cases, the static was already validated on its own, and second, we
599 // trigger cycle errors if we try to compute the value of the other static
600 // and that static refers back to us (potentially through a promoted).
601 // This could miss some UB, but that's fine.
602 // We still walk nested allocations, as they are fundamentally part of this validation run.
603 // This means we will also recurse into nested statics of *other*
604 // statics, even though we do not recurse into other statics directly.
605 // That's somewhat inconsistent but harmless.
606 skip_recursive_check = !nested;
607 }
608 CtfeValidationMode::Const { .. } => {
609 // If this is mutable memory or an `extern static`, there's no point in checking it -- we'd
610 // just get errors trying to read the value.
611 if alloc_actual_mutbl.is_mut()
612 || self.ecx.tcx.is_foreign_item(did)
613 {
614 skip_recursive_check = true;
615 }
616 }
617 }
618 }
619 _ => (),
620 }
621
622 // If this allocation has size zero, there is no actual mutability here.
623 if size != Size::ZERO {
624 // Determine whether this pointer expects to be pointing to something mutable.
625 let ptr_expected_mutbl = match ptr_kind {
626 PointerKind::Box => Mutability::Mut,
627 PointerKind::Ref(mutbl) => {
628 // We do not take into account interior mutability here since we cannot know if
629 // there really is an `UnsafeCell` inside `Option<UnsafeCell>` -- so we check
630 // that in the recursive descent behind this reference (controlled by
631 // `allow_immutable_unsafe_cell`).
632 mutbl
633 }
634 };
635 // Mutable pointer to immutable memory is no good.
636 if ptr_expected_mutbl == Mutability::Mut
637 && alloc_actual_mutbl == Mutability::Not
638 {
639 // This can actually occur with transmutes.
640 throw_validation_failure!(self.path, MutableRefToImmutable);
641 }
642 // In a const, any kind of mutable reference is not good.
643 if matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { .. })) {
644 if ptr_expected_mutbl == Mutability::Mut {
645 throw_validation_failure!(self.path, MutableRefInConst);
646 }
647 }
648 }
649 }
650 // Potentially skip recursive check.
651 if skip_recursive_check {
652 return interp_ok(());
653 }
654 } else {
655 // This is not CTFE, so it's Miri with recursive checking.
656 // FIXME: we do *not* check behind boxes, since creating a new box first creates it uninitialized
657 // and then puts the value in there, so briefly we have a box with uninit contents.
658 // FIXME: should we also skip `UnsafeCell` behind shared references? Currently that is not
659 // needed since validation reads bypass Stacked Borrows and data race checks.
660 if matches!(ptr_kind, PointerKind::Box) {
661 return interp_ok(());
662 }
663 }
664 let path = &self.path;
665 ref_tracking.track(place, || {
666 // We need to clone the path anyway, make sure it gets created
667 // with enough space for the additional `Deref`.
668 let mut new_path = Vec::with_capacity(path.len() + 1);
669 new_path.extend(path);
670 new_path.push(PathElem::Deref);
671 new_path
672 });
673 }
674 interp_ok(())
675 }
676
677 /// Check if this is a value of primitive type, and if yes check the validity of the value
678 /// at that type. Return `true` if the type is indeed primitive.
679 ///
680 /// Note that not all of these have `FieldsShape::Primitive`, e.g. wide references.
681 fn try_visit_primitive(
682 &mut self,
683 value: &PlaceTy<'tcx, M::Provenance>,
684 ) -> InterpResult<'tcx, bool> {
685 // Go over all the primitive types
686 let ty = value.layout.ty;
687 match ty.kind() {
688 ty::Bool => {
689 let scalar = self.read_scalar(value, ExpectedKind::Bool)?;
690 try_validation!(
691 scalar.to_bool(),
692 self.path,
693 Ub(InvalidBool(..)) => ValidationErrorKind::InvalidBool {
694 value: format!("{scalar:x}"),
695 }
696 );
697 if self.reset_provenance_and_padding {
698 self.ecx.clear_provenance(value)?;
699 self.add_data_range_place(value);
700 }
701 interp_ok(true)
702 }
703 ty::Char => {
704 let scalar = self.read_scalar(value, ExpectedKind::Char)?;
705 try_validation!(
706 scalar.to_char(),
707 self.path,
708 Ub(InvalidChar(..)) => ValidationErrorKind::InvalidChar {
709 value: format!("{scalar:x}"),
710 }
711 );
712 if self.reset_provenance_and_padding {
713 self.ecx.clear_provenance(value)?;
714 self.add_data_range_place(value);
715 }
716 interp_ok(true)
717 }
718 ty::Float(_) | ty::Int(_) | ty::Uint(_) => {
719 // NOTE: Keep this in sync with the array optimization for int/float
720 // types below!
721 self.read_scalar(
722 value,
723 if matches!(ty.kind(), ty::Float(..)) {
724 ExpectedKind::Float
725 } else {
726 ExpectedKind::Int
727 },
728 )?;
729 if self.reset_provenance_and_padding {
730 self.ecx.clear_provenance(value)?;
731 self.add_data_range_place(value);
732 }
733 interp_ok(true)
734 }
735 ty::RawPtr(..) => {
736 let place = self.deref_pointer(value, ExpectedKind::RawPtr)?;
737 if place.layout.is_unsized() {
738 self.check_wide_ptr_meta(place.meta(), place.layout)?;
739 }
740 interp_ok(true)
741 }
742 ty::Ref(_, _ty, mutbl) => {
743 self.check_safe_pointer(value, PointerKind::Ref(*mutbl))?;
744 interp_ok(true)
745 }
746 ty::FnPtr(..) => {
747 let scalar = self.read_scalar(value, ExpectedKind::FnPtr)?;
748
749 // If we check references recursively, also check that this points to a function.
750 if let Some(_) = self.ref_tracking {
751 let ptr = scalar.to_pointer(self.ecx)?;
752 let _fn = try_validation!(
753 self.ecx.get_ptr_fn(ptr),
754 self.path,
755 Ub(DanglingIntPointer{ .. } | InvalidFunctionPointer(..)) =>
756 InvalidFnPtr { value: format!("{ptr}") },
757 );
758 // FIXME: Check if the signature matches
759 } else {
760 // Otherwise (for standalone Miri and for `-Zextra-const-ub-checks`),
761 // we have to still check it to be non-null.
762 if self.ecx.scalar_may_be_null(scalar)? {
763 let maybe =
764 !M::Provenance::OFFSET_IS_ADDR && matches!(scalar, Scalar::Ptr(..));
765 throw_validation_failure!(self.path, NullFnPtr { maybe });
766 }
767 }
768 if self.reset_provenance_and_padding {
769 // Make sure we do not preserve partial provenance. This matches the thin
770 // pointer handling in `deref_pointer`.
771 if matches!(scalar, Scalar::Int(..)) {
772 self.ecx.clear_provenance(value)?;
773 }
774 self.add_data_range_place(value);
775 }
776 interp_ok(true)
777 }
778 ty::Never => throw_validation_failure!(self.path, NeverVal),
779 ty::Foreign(..) | ty::FnDef(..) => {
780 // Nothing to check.
781 interp_ok(true)
782 }
783 ty::UnsafeBinder(_) => todo!("FIXME(unsafe_binder)"),
784 // The above should be all the primitive types. The rest is compound, we
785 // check them by visiting their fields/variants.
786 ty::Adt(..)
787 | ty::Tuple(..)
788 | ty::Array(..)
789 | ty::Slice(..)
790 | ty::Str
791 | ty::Dynamic(..)
792 | ty::Closure(..)
793 | ty::Pat(..)
794 | ty::CoroutineClosure(..)
795 | ty::Coroutine(..) => interp_ok(false),
796 // Some types only occur during typechecking, they have no layout.
797 // We should not see them here and we could not check them anyway.
798 ty::Error(_)
799 | ty::Infer(..)
800 | ty::Placeholder(..)
801 | ty::Bound(..)
802 | ty::Param(..)
803 | ty::Alias(..)
804 | ty::CoroutineWitness(..) => bug!("Encountered invalid type {:?}", ty),
805 }
806 }
807
808 fn visit_scalar(
809 &mut self,
810 scalar: Scalar<M::Provenance>,
811 scalar_layout: ScalarAbi,
812 ) -> InterpResult<'tcx> {
813 let size = scalar_layout.size(self.ecx);
814 let valid_range = scalar_layout.valid_range(self.ecx);
815 let WrappingRange { start, end } = valid_range;
816 let max_value = size.unsigned_int_max();
817 assert!(end <= max_value);
818 let bits = match scalar.try_to_scalar_int() {
819 Ok(int) => int.to_bits(size),
820 Err(_) => {
821 // So this is a pointer then, and casting to an int failed.
822 // Can only happen during CTFE.
823 // We support 2 kinds of ranges here: full range, and excluding zero.
824 if start == 1 && end == max_value {
825 // Only null is the niche. So make sure the ptr is NOT null.
826 if self.ecx.scalar_may_be_null(scalar)? {
827 throw_validation_failure!(self.path, NonnullPtrMaybeNull)
828 } else {
829 return interp_ok(());
830 }
831 } else if scalar_layout.is_always_valid(self.ecx) {
832 // Easy. (This is reachable if `enforce_number_validity` is set.)
833 return interp_ok(());
834 } else {
835 // Conservatively, we reject, because the pointer *could* have a bad
836 // value.
837 throw_validation_failure!(
838 self.path,
839 PtrOutOfRange { range: valid_range, max_value }
840 )
841 }
842 }
843 };
844 // Now compare.
845 if valid_range.contains(bits) {
846 interp_ok(())
847 } else {
848 throw_validation_failure!(
849 self.path,
850 OutOfRange { value: format!("{bits}"), range: valid_range, max_value }
851 )
852 }
853 }
854
855 fn in_mutable_memory(&self, val: &PlaceTy<'tcx, M::Provenance>) -> bool {
856 debug_assert!(self.ctfe_mode.is_some());
857 if let Some(mplace) = val.as_mplace_or_local().left() {
858 if let Some(alloc_id) = mplace.ptr().provenance.and_then(|p| p.get_alloc_id()) {
859 let tcx = *self.ecx.tcx;
860 // Everything must be already interned.
861 let mutbl = tcx.global_alloc(alloc_id).mutability(tcx, self.ecx.typing_env);
862 if let Some((_, alloc)) = self.ecx.memory.alloc_map.get(alloc_id) {
863 assert_eq!(alloc.mutability, mutbl);
864 }
865 mutbl.is_mut()
866 } else {
867 // No memory at all.
868 false
869 }
870 } else {
871 // A local variable -- definitely mutable.
872 true
873 }
874 }
875
876 /// Add the given pointer-length pair to the "data" range of this visit.
877 fn add_data_range(&mut self, ptr: Pointer<Option<M::Provenance>>, size: Size) {
878 if let Some(data_bytes) = self.data_bytes.as_mut() {
879 // We only have to store the offset, the rest is the same for all pointers here.
880 // The logic is agnostic to whether the offset is relative or absolute as long as
881 // it is consistent.
882 let (_prov, offset) = ptr.into_raw_parts();
883 // Add this.
884 data_bytes.add_range(offset, size);
885 };
886 }
887
888 /// Add the entire given place to the "data" range of this visit.
889 fn add_data_range_place(&mut self, place: &PlaceTy<'tcx, M::Provenance>) {
890 // Only sized places can be added this way.
891 debug_assert!(place.layout.is_sized());
892 if let Some(data_bytes) = self.data_bytes.as_mut() {
893 let offset = Self::data_range_offset(self.ecx, place);
894 data_bytes.add_range(offset, place.layout.size);
895 }
896 }
897
898 /// Convert a place into the offset it starts at, for the purpose of data_range tracking.
899 /// Must only be called if `data_bytes` is `Some(_)`.
900 fn data_range_offset(ecx: &InterpCx<'tcx, M>, place: &PlaceTy<'tcx, M::Provenance>) -> Size {
901 // The presence of `data_bytes` implies that our place is in memory.
902 let ptr = ecx
903 .place_to_op(place)
904 .expect("place must be in memory")
905 .as_mplace_or_imm()
906 .expect_left("place must be in memory")
907 .ptr();
908 let (_prov, offset) = ptr.into_raw_parts();
909 offset
910 }
911
912 fn reset_padding(&mut self, place: &PlaceTy<'tcx, M::Provenance>) -> InterpResult<'tcx> {
913 let Some(data_bytes) = self.data_bytes.as_mut() else { return interp_ok(()) };
914 // Our value must be in memory, otherwise we would not have set up `data_bytes`.
915 let mplace = self.ecx.force_allocation(place)?;
916 // Determine starting offset and size.
917 let (_prov, start_offset) = mplace.ptr().into_raw_parts();
918 let (size, _align) = self
919 .ecx
920 .size_and_align_of_val(&mplace)?
921 .unwrap_or((mplace.layout.size, mplace.layout.align.abi));
922 // If there is no padding at all, we can skip the rest: check for
923 // a single data range covering the entire value.
924 if data_bytes.0 == &[(start_offset, size)] {
925 return interp_ok(());
926 }
927 // Get a handle for the allocation. Do this only once, to avoid looking up the same
928 // allocation over and over again. (Though to be fair, iterating the value already does
929 // exactly that.)
930 let Some(mut alloc) = self.ecx.get_ptr_alloc_mut(mplace.ptr(), size)? else {
931 // A ZST, no padding to clear.
932 return interp_ok(());
933 };
934 // Add a "finalizer" data range at the end, so that the iteration below finds all gaps
935 // between ranges.
936 data_bytes.0.push((start_offset + size, Size::ZERO));
937 // Iterate, and reset gaps.
938 let mut padding_cleared_until = start_offset;
939 for &(offset, size) in data_bytes.0.iter() {
940 assert!(
941 offset >= padding_cleared_until,
942 "reset_padding on {}: previous field ended at offset {}, next field starts at {} (and has a size of {} bytes)",
943 mplace.layout.ty,
944 (padding_cleared_until - start_offset).bytes(),
945 (offset - start_offset).bytes(),
946 size.bytes(),
947 );
948 if offset > padding_cleared_until {
949 // We found padding. Adjust the range to be relative to `alloc`, and make it uninit.
950 let padding_start = padding_cleared_until - start_offset;
951 let padding_size = offset - padding_cleared_until;
952 let range = alloc_range(padding_start, padding_size);
953 trace!("reset_padding on {}: resetting padding range {range:?}", mplace.layout.ty);
954 alloc.write_uninit(range);
955 }
956 padding_cleared_until = offset + size;
957 }
958 assert!(padding_cleared_until == start_offset + size);
959 interp_ok(())
960 }
961
962 /// Computes the data range of this union type:
963 /// which bytes are inside a field (i.e., not padding.)
964 fn union_data_range<'e>(
965 ecx: &'e mut InterpCx<'tcx, M>,
966 layout: TyAndLayout<'tcx>,
967 ) -> Cow<'e, RangeSet> {
968 assert!(layout.ty.is_union());
969 assert!(layout.is_sized(), "there are no unsized unions");
970 let layout_cx = LayoutCx::new(*ecx.tcx, ecx.typing_env);
971 return M::cached_union_data_range(ecx, layout.ty, || {
972 let mut out = RangeSet(Vec::new());
973 union_data_range_uncached(&layout_cx, layout, Size::ZERO, &mut out);
974 out
975 });
976
977 /// Helper for recursive traversal: add data ranges of the given type to `out`.
978 fn union_data_range_uncached<'tcx>(
979 cx: &LayoutCx<'tcx>,
980 layout: TyAndLayout<'tcx>,
981 base_offset: Size,
982 out: &mut RangeSet,
983 ) {
984 // If this is a ZST, we don't contain any data. In particular, this helps us to quickly
985 // skip over huge arrays of ZST.
986 if layout.is_zst() {
987 return;
988 }
989 // Just recursively add all the fields of everything to the output.
990 match &layout.fields {
991 FieldsShape::Primitive => {
992 out.add_range(base_offset, layout.size);
993 }
994 &FieldsShape::Union(fields) => {
995 // Currently, all fields start at offset 0 (relative to `base_offset`).
996 for field in 0..fields.get() {
997 let field = layout.field(cx, field);
998 union_data_range_uncached(cx, field, base_offset, out);
999 }
1000 }
1001 &FieldsShape::Array { stride, count } => {
1002 let elem = layout.field(cx, 0);
1003
1004 // Fast-path for large arrays of simple types that do not contain any padding.
1005 if elem.backend_repr.is_scalar() {
1006 out.add_range(base_offset, elem.size * count);
1007 } else {
1008 for idx in 0..count {
1009 // This repeats the same computation for every array element... but the alternative
1010 // is to allocate temporary storage for a dedicated `out` set for the array element,
1011 // and replicating that N times. Is that better?
1012 union_data_range_uncached(cx, elem, base_offset + idx * stride, out);
1013 }
1014 }
1015 }
1016 FieldsShape::Arbitrary { offsets, .. } => {
1017 for (field, &offset) in offsets.iter_enumerated() {
1018 let field = layout.field(cx, field.as_usize());
1019 union_data_range_uncached(cx, field, base_offset + offset, out);
1020 }
1021 }
1022 }
1023 // Don't forget potential other variants.
1024 match &layout.variants {
1025 Variants::Single { .. } | Variants::Empty => {
1026 // Fully handled above.
1027 }
1028 Variants::Multiple { variants, .. } => {
1029 for variant in variants.indices() {
1030 let variant = layout.for_variant(cx, variant);
1031 union_data_range_uncached(cx, variant, base_offset, out);
1032 }
1033 }
1034 }
1035 }
1036 }
1037}
1038
1039impl<'rt, 'tcx, M: Machine<'tcx>> ValueVisitor<'tcx, M> for ValidityVisitor<'rt, 'tcx, M> {
1040 type V = PlaceTy<'tcx, M::Provenance>;
1041
1042 #[inline(always)]
1043 fn ecx(&self) -> &InterpCx<'tcx, M> {
1044 self.ecx
1045 }
1046
1047 fn read_discriminant(
1048 &mut self,
1049 val: &PlaceTy<'tcx, M::Provenance>,
1050 ) -> InterpResult<'tcx, VariantIdx> {
1051 self.with_elem(PathElem::EnumTag, move |this| {
1052 interp_ok(try_validation!(
1053 this.ecx.read_discriminant(val),
1054 this.path,
1055 Ub(InvalidTag(val)) => InvalidEnumTag {
1056 value: format!("{val:x}"),
1057 },
1058 Ub(UninhabitedEnumVariantRead(_)) => UninhabitedEnumVariant,
1059 // Uninit / bad provenance are not possible since the field was already previously
1060 // checked at its integer type.
1061 ))
1062 })
1063 }
1064
1065 #[inline]
1066 fn visit_field(
1067 &mut self,
1068 old_val: &PlaceTy<'tcx, M::Provenance>,
1069 field: usize,
1070 new_val: &PlaceTy<'tcx, M::Provenance>,
1071 ) -> InterpResult<'tcx> {
1072 let elem = self.aggregate_field_path_elem(old_val.layout, field);
1073 self.with_elem(elem, move |this| this.visit_value(new_val))
1074 }
1075
1076 #[inline]
1077 fn visit_variant(
1078 &mut self,
1079 old_val: &PlaceTy<'tcx, M::Provenance>,
1080 variant_id: VariantIdx,
1081 new_val: &PlaceTy<'tcx, M::Provenance>,
1082 ) -> InterpResult<'tcx> {
1083 let name = match old_val.layout.ty.kind() {
1084 ty::Adt(adt, _) => PathElem::Variant(adt.variant(variant_id).name),
1085 // Coroutines also have variants
1086 ty::Coroutine(..) => PathElem::CoroutineState(variant_id),
1087 _ => bug!("Unexpected type with variant: {:?}", old_val.layout.ty),
1088 };
1089 self.with_elem(name, move |this| this.visit_value(new_val))
1090 }
1091
1092 #[inline(always)]
1093 fn visit_union(
1094 &mut self,
1095 val: &PlaceTy<'tcx, M::Provenance>,
1096 _fields: NonZero<usize>,
1097 ) -> InterpResult<'tcx> {
1098 // Special check for CTFE validation, preventing `UnsafeCell` inside unions in immutable memory.
1099 if self.ctfe_mode.is_some_and(|c| !c.allow_immutable_unsafe_cell()) {
1100 // Unsized unions are currently not a thing, but let's keep this code consistent with
1101 // the check in `visit_value`.
1102 let zst = self.ecx.size_and_align_of_val(val)?.is_some_and(|(s, _a)| s.bytes() == 0);
1103 if !zst && !val.layout.ty.is_freeze(*self.ecx.tcx, self.ecx.typing_env) {
1104 if !self.in_mutable_memory(val) {
1105 throw_validation_failure!(self.path, UnsafeCellInImmutable);
1106 }
1107 }
1108 }
1109 if self.reset_provenance_and_padding
1110 && let Some(data_bytes) = self.data_bytes.as_mut()
1111 {
1112 let base_offset = Self::data_range_offset(self.ecx, val);
1113 // Determine and add data range for this union.
1114 let union_data_range = Self::union_data_range(self.ecx, val.layout);
1115 for &(offset, size) in union_data_range.0.iter() {
1116 data_bytes.add_range(base_offset + offset, size);
1117 }
1118 }
1119 interp_ok(())
1120 }
1121
1122 #[inline]
1123 fn visit_box(
1124 &mut self,
1125 _box_ty: Ty<'tcx>,
1126 val: &PlaceTy<'tcx, M::Provenance>,
1127 ) -> InterpResult<'tcx> {
1128 self.check_safe_pointer(val, PointerKind::Box)?;
1129 interp_ok(())
1130 }
1131
1132 #[inline]
1133 fn visit_value(&mut self, val: &PlaceTy<'tcx, M::Provenance>) -> InterpResult<'tcx> {
1134 trace!("visit_value: {:?}, {:?}", *val, val.layout);
1135
1136 // Check primitive types -- the leaves of our recursive descent.
1137 // This is called even for enum discriminants (which are "fields" of their enum),
1138 // so for integer-typed discriminants the provenance reset will happen here.
1139 // We assume that the Scalar validity range does not restrict these values
1140 // any further than `try_visit_primitive` does!
1141 if self.try_visit_primitive(val)? {
1142 return interp_ok(());
1143 }
1144
1145 // Special check preventing `UnsafeCell` in the inner part of constants
1146 if self.ctfe_mode.is_some_and(|c| !c.allow_immutable_unsafe_cell()) {
1147 // Exclude ZST values. We need to compute the dynamic size/align to properly
1148 // handle slices and trait objects.
1149 let zst = self.ecx.size_and_align_of_val(val)?.is_some_and(|(s, _a)| s.bytes() == 0);
1150 if !zst
1151 && let Some(def) = val.layout.ty.ty_adt_def()
1152 && def.is_unsafe_cell()
1153 {
1154 if !self.in_mutable_memory(val) {
1155 throw_validation_failure!(self.path, UnsafeCellInImmutable);
1156 }
1157 }
1158 }
1159
1160 // Recursively walk the value at its type. Apply optimizations for some large types.
1161 match val.layout.ty.kind() {
1162 ty::Str => {
1163 let mplace = val.assert_mem_place(); // strings are unsized and hence never immediate
1164 let len = mplace.len(self.ecx)?;
1165 try_validation!(
1166 self.ecx.read_bytes_ptr_strip_provenance(mplace.ptr(), Size::from_bytes(len)),
1167 self.path,
1168 Ub(InvalidUninitBytes(..)) => Uninit { expected: ExpectedKind::Str },
1169 Unsup(ReadPointerAsInt(_)) => PointerAsInt { expected: ExpectedKind::Str }
1170 );
1171 }
1172 ty::Array(tys, ..) | ty::Slice(tys)
1173 // This optimization applies for types that can hold arbitrary non-provenance bytes (such as
1174 // integer and floating point types).
1175 // FIXME(wesleywiser) This logic could be extended further to arbitrary structs or
1176 // tuples made up of integer/floating point types or inhabited ZSTs with no padding.
1177 if matches!(tys.kind(), ty::Int(..) | ty::Uint(..) | ty::Float(..))
1178 =>
1179 {
1180 let expected = if tys.is_integral() { ExpectedKind::Int } else { ExpectedKind::Float };
1181 // Optimized handling for arrays of integer/float type.
1182
1183 // This is the length of the array/slice.
1184 let len = val.len(self.ecx)?;
1185 // This is the element type size.
1186 let layout = self.ecx.layout_of(*tys)?;
1187 // This is the size in bytes of the whole array. (This checks for overflow.)
1188 let size = layout.size * len;
1189 // If the size is 0, there is nothing to check.
1190 // (`size` can only be 0 if `len` is 0, and empty arrays are always valid.)
1191 if size == Size::ZERO {
1192 return interp_ok(());
1193 }
1194 // Now that we definitely have a non-ZST array, we know it lives in memory -- except it may
1195 // be an uninitialized local variable, those are also "immediate".
1196 let mplace = match val.to_op(self.ecx)?.as_mplace_or_imm() {
1197 Left(mplace) => mplace,
1198 Right(imm) => match *imm {
1199 Immediate::Uninit =>
1200 throw_validation_failure!(self.path, Uninit { expected }),
1201 Immediate::Scalar(..) | Immediate::ScalarPair(..) =>
1202 bug!("arrays/slices can never have Scalar/ScalarPair layout"),
1203 }
1204 };
1205
1206 // Optimization: we just check the entire range at once.
1207 // NOTE: Keep this in sync with the handling of integer and float
1208 // types above, in `visit_primitive`.
1209 // No need for an alignment check here, this is not an actual memory access.
1210 let alloc = self.ecx.get_ptr_alloc(mplace.ptr(), size)?.expect("we already excluded size 0");
1211
1212 alloc.get_bytes_strip_provenance().map_err_kind(|kind| {
1213 // Some error happened, try to provide a more detailed description.
1214 // For some errors we might be able to provide extra information.
1215 // (This custom logic does not fit the `try_validation!` macro.)
1216 match kind {
1217 Ub(InvalidUninitBytes(Some((_alloc_id, access)))) | Unsup(ReadPointerAsInt(Some((_alloc_id, access)))) => {
1218 // Some byte was uninitialized, determine which
1219 // element that byte belongs to so we can
1220 // provide an index.
1221 let i = usize::try_from(
1222 access.bad.start.bytes() / layout.size.bytes(),
1223 )
1224 .unwrap();
1225 self.path.push(PathElem::ArrayElem(i));
1226
1227 if matches!(kind, Ub(InvalidUninitBytes(_))) {
1228 err_validation_failure!(self.path, Uninit { expected })
1229 } else {
1230 err_validation_failure!(self.path, PointerAsInt { expected })
1231 }
1232 }
1233
1234 // Propagate upwards (that will also check for unexpected errors).
1235 err => err,
1236 }
1237 })?;
1238
1239 // Don't forget that these are all non-pointer types, and thus do not preserve
1240 // provenance.
1241 if self.reset_provenance_and_padding {
1242 // We can't share this with above as above, we might be looking at read-only memory.
1243 let mut alloc = self.ecx.get_ptr_alloc_mut(mplace.ptr(), size)?.expect("we already excluded size 0");
1244 alloc.clear_provenance();
1245 // Also, mark this as containing data, not padding.
1246 self.add_data_range(mplace.ptr(), size);
1247 }
1248 }
1249 // Fast path for arrays and slices of ZSTs. We only need to check a single ZST element
1250 // of an array and not all of them, because there's only a single value of a specific
1251 // ZST type, so either validation fails for all elements or none.
1252 ty::Array(tys, ..) | ty::Slice(tys) if self.ecx.layout_of(*tys)?.is_zst() => {
1253 // Validate just the first element (if any).
1254 if val.len(self.ecx)? > 0 {
1255 self.visit_field(val, 0, &self.ecx.project_index(val, 0)?)?;
1256 }
1257 }
1258 ty::Pat(base, pat) => {
1259 // First check that the base type is valid
1260 self.visit_value(&val.transmute(self.ecx.layout_of(*base)?, self.ecx)?)?;
1261 // When you extend this match, make sure to also add tests to
1262 // tests/ui/type/pattern_types/validity.rs((
1263 match **pat {
1264 // Range patterns are precisely reflected into `valid_range` and thus
1265 // handled fully by `visit_scalar` (called below).
1266 ty::PatternKind::Range { .. } => {},
1267
1268 // FIXME(pattern_types): check that the value is covered by one of the variants.
1269 // For now, we rely on layout computation setting the scalar's `valid_range` to
1270 // match the pattern. However, this cannot always work; the layout may
1271 // pessimistically cover actually illegal ranges and Miri would miss that UB.
1272 // The consolation here is that codegen also will miss that UB, so at least
1273 // we won't see optimizations actually breaking such programs.
1274 ty::PatternKind::Or(_patterns) => {}
1275 }
1276 }
1277 _ => {
1278 // default handler
1279 try_validation!(
1280 self.walk_value(val),
1281 self.path,
1282 // It's not great to catch errors here, since we can't give a very good path,
1283 // but it's better than ICEing.
1284 Ub(InvalidVTableTrait { vtable_dyn_type, expected_dyn_type }) => {
1285 InvalidMetaWrongTrait { vtable_dyn_type, expected_dyn_type }
1286 },
1287 );
1288 }
1289 }
1290
1291 // *After* all of this, check further information stored in the layout. We need to check
1292 // this to handle types like `NonNull` where the `Scalar` info is more restrictive than what
1293 // the fields say (`rustc_layout_scalar_valid_range_start`). But in most cases, this will
1294 // just propagate what the fields say, and then we want the error to point at the field --
1295 // so, we first recurse, then we do this check.
1296 //
1297 // FIXME: We could avoid some redundant checks here. For newtypes wrapping
1298 // scalars, we do the same check on every "level" (e.g., first we check
1299 // MyNewtype and then the scalar in there).
1300 if val.layout.is_uninhabited() {
1301 let ty = val.layout.ty;
1302 throw_validation_failure!(self.path, UninhabitedVal { ty });
1303 }
1304 match val.layout.backend_repr {
1305 BackendRepr::Scalar(scalar_layout) => {
1306 if !scalar_layout.is_uninit_valid() {
1307 // There is something to check here.
1308 let scalar = self.read_scalar(val, ExpectedKind::InitScalar)?;
1309 self.visit_scalar(scalar, scalar_layout)?;
1310 }
1311 }
1312 BackendRepr::ScalarPair(a_layout, b_layout) => {
1313 // We can only proceed if *both* scalars need to be initialized.
1314 // FIXME: find a way to also check ScalarPair when one side can be uninit but
1315 // the other must be init.
1316 if !a_layout.is_uninit_valid() && !b_layout.is_uninit_valid() {
1317 let (a, b) =
1318 self.read_immediate(val, ExpectedKind::InitScalar)?.to_scalar_pair();
1319 self.visit_scalar(a, a_layout)?;
1320 self.visit_scalar(b, b_layout)?;
1321 }
1322 }
1323 BackendRepr::SimdVector { .. } => {
1324 // No checks here, we assume layout computation gets this right.
1325 // (This is harder to check since Miri does not represent these as `Immediate`. We
1326 // also cannot use field projections since this might be a newtype around a vector.)
1327 }
1328 BackendRepr::Memory { .. } => {
1329 // Nothing to do.
1330 }
1331 }
1332
1333 interp_ok(())
1334 }
1335}
1336
1337impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
1338 fn validate_operand_internal(
1339 &mut self,
1340 val: &PlaceTy<'tcx, M::Provenance>,
1341 path: Vec<PathElem>,
1342 ref_tracking: Option<&mut RefTracking<MPlaceTy<'tcx, M::Provenance>, Vec<PathElem>>>,
1343 ctfe_mode: Option<CtfeValidationMode>,
1344 reset_provenance_and_padding: bool,
1345 ) -> InterpResult<'tcx> {
1346 trace!("validate_operand_internal: {:?}, {:?}", *val, val.layout.ty);
1347
1348 // Run the visitor.
1349 self.run_for_validation_mut(|ecx| {
1350 let reset_padding = reset_provenance_and_padding && {
1351 // Check if `val` is actually stored in memory. If not, padding is not even
1352 // represented and we need not reset it.
1353 ecx.place_to_op(val)?.as_mplace_or_imm().is_left()
1354 };
1355 let mut v = ValidityVisitor {
1356 path,
1357 ref_tracking,
1358 ctfe_mode,
1359 ecx,
1360 reset_provenance_and_padding,
1361 data_bytes: reset_padding.then_some(RangeSet(Vec::new())),
1362 };
1363 v.visit_value(val)?;
1364 v.reset_padding(val)?;
1365 interp_ok(())
1366 })
1367 .map_err_info(|err| {
1368 if !matches!(
1369 err.kind(),
1370 err_ub!(ValidationError { .. })
1371 | InterpErrorKind::InvalidProgram(_)
1372 | InterpErrorKind::Unsupported(UnsupportedOpInfo::ExternTypeField)
1373 ) {
1374 bug!(
1375 "Unexpected error during validation: {}",
1376 format_interp_error(self.tcx.dcx(), err)
1377 );
1378 }
1379 err
1380 })
1381 }
1382
1383 /// This function checks the data at `val` to be const-valid.
1384 /// `val` is assumed to cover valid memory if it is an indirect operand.
1385 /// It will error if the bits at the destination do not match the ones described by the layout.
1386 ///
1387 /// `ref_tracking` is used to record references that we encounter so that they
1388 /// can be checked recursively by an outside driving loop.
1389 ///
1390 /// `constant` controls whether this must satisfy the rules for constants:
1391 /// - no pointers to statics.
1392 /// - no `UnsafeCell` or non-ZST `&mut`.
1393 #[inline(always)]
1394 pub(crate) fn const_validate_operand(
1395 &mut self,
1396 val: &PlaceTy<'tcx, M::Provenance>,
1397 path: Vec<PathElem>,
1398 ref_tracking: &mut RefTracking<MPlaceTy<'tcx, M::Provenance>, Vec<PathElem>>,
1399 ctfe_mode: CtfeValidationMode,
1400 ) -> InterpResult<'tcx> {
1401 self.validate_operand_internal(
1402 val,
1403 path,
1404 Some(ref_tracking),
1405 Some(ctfe_mode),
1406 /*reset_provenance*/ false,
1407 )
1408 }
1409
1410 /// This function checks the data at `val` to be runtime-valid.
1411 /// `val` is assumed to cover valid memory if it is an indirect operand.
1412 /// It will error if the bits at the destination do not match the ones described by the layout.
1413 #[inline(always)]
1414 pub fn validate_operand(
1415 &mut self,
1416 val: &PlaceTy<'tcx, M::Provenance>,
1417 recursive: bool,
1418 reset_provenance_and_padding: bool,
1419 ) -> InterpResult<'tcx> {
1420 let _trace = enter_trace_span!(
1421 M,
1422 "validate_operand",
1423 recursive,
1424 reset_provenance_and_padding,
1425 ?val,
1426 );
1427
1428 // Note that we *could* actually be in CTFE here with `-Zextra-const-ub-checks`, but it's
1429 // still correct to not use `ctfe_mode`: that mode is for validation of the final constant
1430 // value, it rules out things like `UnsafeCell` in awkward places.
1431 if !recursive {
1432 return self.validate_operand_internal(
1433 val,
1434 vec![],
1435 None,
1436 None,
1437 reset_provenance_and_padding,
1438 );
1439 }
1440 // Do a recursive check.
1441 let mut ref_tracking = RefTracking::empty();
1442 self.validate_operand_internal(
1443 val,
1444 vec![],
1445 Some(&mut ref_tracking),
1446 None,
1447 reset_provenance_and_padding,
1448 )?;
1449 while let Some((mplace, path)) = ref_tracking.todo.pop() {
1450 // Things behind reference do *not* have the provenance reset.
1451 self.validate_operand_internal(
1452 &mplace.into(),
1453 path,
1454 Some(&mut ref_tracking),
1455 None,
1456 /*reset_provenance_and_padding*/ false,
1457 )?;
1458 }
1459 interp_ok(())
1460 }
1461}