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Diffstat (limited to 'compiler/rustc_const_eval/src/interpret/validity.rs')
| -rw-r--r-- | compiler/rustc_const_eval/src/interpret/validity.rs | 986 |
1 files changed, 986 insertions, 0 deletions
diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs new file mode 100644 index 000000000..0e50d1ed4 --- /dev/null +++ b/compiler/rustc_const_eval/src/interpret/validity.rs @@ -0,0 +1,986 @@ +//! Check the validity invariant of a given value, and tell the user +//! where in the value it got violated. +//! In const context, this goes even further and tries to approximate const safety. +//! That's useful because it means other passes (e.g. promotion) can rely on `const`s +//! to be const-safe. + +use std::convert::TryFrom; +use std::fmt::Write; +use std::num::NonZeroUsize; + +use rustc_data_structures::fx::FxHashSet; +use rustc_hir as hir; +use rustc_middle::mir::interpret::InterpError; +use rustc_middle::ty; +use rustc_middle::ty::layout::{LayoutOf, TyAndLayout}; +use rustc_span::symbol::{sym, Symbol}; +use rustc_span::DUMMY_SP; +use rustc_target::abi::{Abi, Scalar as ScalarAbi, Size, VariantIdx, Variants, WrappingRange}; + +use std::hash::Hash; + +use super::{ + alloc_range, CheckInAllocMsg, GlobalAlloc, Immediate, InterpCx, InterpResult, MPlaceTy, + Machine, MemPlaceMeta, OpTy, Scalar, ScalarMaybeUninit, ValueVisitor, +}; + +macro_rules! throw_validation_failure { + ($where:expr, { $( $what_fmt:expr ),+ } $( expected { $( $expected_fmt:expr ),+ } )?) => {{ + let mut msg = String::new(); + msg.push_str("encountered "); + write!(&mut msg, $($what_fmt),+).unwrap(); + $( + msg.push_str(", but expected "); + write!(&mut msg, $($expected_fmt),+).unwrap(); + )? + let path = rustc_middle::ty::print::with_no_trimmed_paths!({ + let where_ = &$where; + if !where_.is_empty() { + let mut path = String::new(); + write_path(&mut path, where_); + Some(path) + } else { + None + } + }); + throw_ub!(ValidationFailure { path, msg }) + }}; +} + +/// If $e throws an error matching the pattern, throw a validation failure. +/// Other errors are passed back to the caller, unchanged -- and if they reach the root of +/// the visitor, we make sure only validation errors and `InvalidProgram` errors are left. +/// This lets you use the patterns as a kind of validation list, asserting which errors +/// can possibly happen: +/// +/// ``` +/// let v = try_validation!(some_fn(), some_path, { +/// Foo | Bar | Baz => { "some failure" }, +/// }); +/// ``` +/// +/// An additional expected parameter can also be added to the failure message: +/// +/// ``` +/// let v = try_validation!(some_fn(), some_path, { +/// Foo | Bar | Baz => { "some failure" } expected { "something that wasn't a failure" }, +/// }); +/// ``` +/// +/// An additional nicety is that both parameters actually take format args, so you can just write +/// the format string in directly: +/// +/// ``` +/// let v = try_validation!(some_fn(), some_path, { +/// Foo | Bar | Baz => { "{:?}", some_failure } expected { "{}", expected_value }, +/// }); +/// ``` +/// +macro_rules! try_validation { + ($e:expr, $where:expr, + $( $( $p:pat_param )|+ => { $( $what_fmt:expr ),+ } $( expected { $( $expected_fmt:expr ),+ } )? ),+ $(,)? + ) => {{ + match $e { + Ok(x) => x, + // We catch the error and turn it into a validation failure. We are okay with + // allocation here as this can only slow down builds that fail anyway. + Err(e) => match e.kind() { + $( + $($p)|+ => + throw_validation_failure!( + $where, + { $( $what_fmt ),+ } $( expected { $( $expected_fmt ),+ } )? + ) + ),+, + #[allow(unreachable_patterns)] + _ => Err::<!, _>(e)?, + } + } + }}; +} + +/// We want to show a nice path to the invalid field for diagnostics, +/// but avoid string operations in the happy case where no error happens. +/// So we track a `Vec<PathElem>` where `PathElem` contains all the data we +/// need to later print something for the user. +#[derive(Copy, Clone, Debug)] +pub enum PathElem { + Field(Symbol), + Variant(Symbol), + GeneratorState(VariantIdx), + CapturedVar(Symbol), + ArrayElem(usize), + TupleElem(usize), + Deref, + EnumTag, + GeneratorTag, + DynDowncast, +} + +/// Extra things to check for during validation of CTFE results. +pub enum CtfeValidationMode { + /// Regular validation, nothing special happening. + Regular, + /// Validation of a `const`. + /// `inner` says if this is an inner, indirect allocation (as opposed to the top-level const + /// allocation). Being an inner allocation makes a difference because the top-level allocation + /// of a `const` is copied for each use, but the inner allocations are implicitly shared. + /// `allow_static_ptrs` says if pointers to statics are permitted (which is the case for promoteds in statics). + Const { inner: bool, allow_static_ptrs: bool }, +} + +/// State for tracking recursive validation of references +pub struct RefTracking<T, PATH = ()> { + pub seen: FxHashSet<T>, + pub todo: Vec<(T, PATH)>, +} + +impl<T: Copy + Eq + Hash + std::fmt::Debug, PATH: Default> RefTracking<T, PATH> { + pub fn empty() -> Self { + RefTracking { seen: FxHashSet::default(), todo: vec![] } + } + pub fn new(op: T) -> Self { + let mut ref_tracking_for_consts = + RefTracking { seen: FxHashSet::default(), todo: vec![(op, PATH::default())] }; + ref_tracking_for_consts.seen.insert(op); + ref_tracking_for_consts + } + + pub fn track(&mut self, op: T, path: impl FnOnce() -> PATH) { + if self.seen.insert(op) { + trace!("Recursing below ptr {:#?}", op); + let path = path(); + // Remember to come back to this later. + self.todo.push((op, path)); + } + } +} + +/// Format a path +fn write_path(out: &mut String, path: &[PathElem]) { + use self::PathElem::*; + + for elem in path.iter() { + match elem { + Field(name) => write!(out, ".{}", name), + EnumTag => write!(out, ".<enum-tag>"), + Variant(name) => write!(out, ".<enum-variant({})>", name), + GeneratorTag => write!(out, ".<generator-tag>"), + GeneratorState(idx) => write!(out, ".<generator-state({})>", idx.index()), + CapturedVar(name) => write!(out, ".<captured-var({})>", name), + TupleElem(idx) => write!(out, ".{}", idx), + ArrayElem(idx) => write!(out, "[{}]", idx), + // `.<deref>` does not match Rust syntax, but it is more readable for long paths -- and + // some of the other items here also are not Rust syntax. Actually we can't + // even use the usual syntax because we are just showing the projections, + // not the root. + Deref => write!(out, ".<deref>"), + DynDowncast => write!(out, ".<dyn-downcast>"), + } + .unwrap() + } +} + +// Formats such that a sentence like "expected something {}" to mean +// "expected something <in the given range>" makes sense. +fn wrapping_range_format(r: WrappingRange, max_hi: u128) -> String { + let WrappingRange { start: lo, end: hi } = r; + assert!(hi <= max_hi); + if lo > hi { + format!("less or equal to {}, or greater or equal to {}", hi, lo) + } else if lo == hi { + format!("equal to {}", lo) + } else if lo == 0 { + assert!(hi < max_hi, "should not be printing if the range covers everything"); + format!("less or equal to {}", hi) + } else if hi == max_hi { + assert!(lo > 0, "should not be printing if the range covers everything"); + format!("greater or equal to {}", lo) + } else { + format!("in the range {:?}", r) + } +} + +struct ValidityVisitor<'rt, 'mir, 'tcx, M: Machine<'mir, 'tcx>> { + /// The `path` may be pushed to, but the part that is present when a function + /// starts must not be changed! `visit_fields` and `visit_array` rely on + /// this stack discipline. + path: Vec<PathElem>, + ref_tracking: Option<&'rt mut RefTracking<MPlaceTy<'tcx, M::Provenance>, Vec<PathElem>>>, + /// `None` indicates this is not validating for CTFE (but for runtime). + ctfe_mode: Option<CtfeValidationMode>, + ecx: &'rt InterpCx<'mir, 'tcx, M>, +} + +impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, 'tcx, M> { + fn aggregate_field_path_elem(&mut self, layout: TyAndLayout<'tcx>, field: usize) -> PathElem { + // First, check if we are projecting to a variant. + match layout.variants { + Variants::Multiple { tag_field, .. } => { + if tag_field == field { + return match layout.ty.kind() { + ty::Adt(def, ..) if def.is_enum() => PathElem::EnumTag, + ty::Generator(..) => PathElem::GeneratorTag, + _ => bug!("non-variant type {:?}", layout.ty), + }; + } + } + Variants::Single { .. } => {} + } + + // Now we know we are projecting to a field, so figure out which one. + match layout.ty.kind() { + // generators and closures. + ty::Closure(def_id, _) | ty::Generator(def_id, _, _) => { + let mut name = None; + // FIXME this should be more descriptive i.e. CapturePlace instead of CapturedVar + // https://github.com/rust-lang/project-rfc-2229/issues/46 + if let Some(local_def_id) = def_id.as_local() { + let tables = self.ecx.tcx.typeck(local_def_id); + if let Some(captured_place) = + tables.closure_min_captures_flattened(local_def_id).nth(field) + { + // Sometimes the index is beyond the number of upvars (seen + // for a generator). + let var_hir_id = captured_place.get_root_variable(); + let node = self.ecx.tcx.hir().get(var_hir_id); + if let hir::Node::Pat(pat) = node { + if let hir::PatKind::Binding(_, _, ident, _) = pat.kind { + name = Some(ident.name); + } + } + } + } + + PathElem::CapturedVar(name.unwrap_or_else(|| { + // Fall back to showing the field index. + sym::integer(field) + })) + } + + // tuples + ty::Tuple(_) => PathElem::TupleElem(field), + + // enums + ty::Adt(def, ..) if def.is_enum() => { + // we might be projecting *to* a variant, or to a field *in* a variant. + match layout.variants { + Variants::Single { index } => { + // Inside a variant + PathElem::Field(def.variant(index).fields[field].name) + } + Variants::Multiple { .. } => bug!("we handled variants above"), + } + } + + // other ADTs + ty::Adt(def, _) => PathElem::Field(def.non_enum_variant().fields[field].name), + + // arrays/slices + ty::Array(..) | ty::Slice(..) => PathElem::ArrayElem(field), + + // dyn traits + ty::Dynamic(..) => PathElem::DynDowncast, + + // nothing else has an aggregate layout + _ => bug!("aggregate_field_path_elem: got non-aggregate type {:?}", layout.ty), + } + } + + fn with_elem<R>( + &mut self, + elem: PathElem, + f: impl FnOnce(&mut Self) -> InterpResult<'tcx, R>, + ) -> InterpResult<'tcx, R> { + // Remember the old state + let path_len = self.path.len(); + // Record new element + self.path.push(elem); + // Perform operation + let r = f(self)?; + // Undo changes + self.path.truncate(path_len); + // Done + Ok(r) + } + + fn check_wide_ptr_meta( + &mut self, + meta: MemPlaceMeta<M::Provenance>, + pointee: TyAndLayout<'tcx>, + ) -> InterpResult<'tcx> { + let tail = self.ecx.tcx.struct_tail_erasing_lifetimes(pointee.ty, self.ecx.param_env); + match tail.kind() { + ty::Dynamic(..) => { + let vtable = meta.unwrap_meta().to_pointer(self.ecx)?; + // Make sure it is a genuine vtable pointer. + let (_ty, _trait) = try_validation!( + self.ecx.get_ptr_vtable(vtable), + self.path, + err_ub!(DanglingIntPointer(..)) | + err_ub!(InvalidVTablePointer(..)) => + { "{vtable}" } expected { "a vtable pointer" }, + ); + // FIXME: check if the type/trait match what ty::Dynamic says? + } + ty::Slice(..) | ty::Str => { + let _len = meta.unwrap_meta().to_machine_usize(self.ecx)?; + // We do not check that `len * elem_size <= isize::MAX`: + // that is only required for references, and there it falls out of the + // "dereferenceable" check performed by Stacked Borrows. + } + ty::Foreign(..) => { + // Unsized, but not wide. + } + _ => bug!("Unexpected unsized type tail: {:?}", tail), + } + + Ok(()) + } + + /// Check a reference or `Box`. + fn check_safe_pointer( + &mut self, + value: &OpTy<'tcx, M::Provenance>, + kind: &str, + ) -> InterpResult<'tcx> { + let value = self.ecx.read_immediate(value)?; + // Handle wide pointers. + // Check metadata early, for better diagnostics + let place = try_validation!( + self.ecx.ref_to_mplace(&value), + self.path, + err_ub!(InvalidUninitBytes(None)) => { "uninitialized {}", kind }, + ); + if place.layout.is_unsized() { + self.check_wide_ptr_meta(place.meta, place.layout)?; + } + // Make sure this is dereferenceable and all. + let size_and_align = try_validation!( + self.ecx.size_and_align_of_mplace(&place), + self.path, + err_ub!(InvalidMeta(msg)) => { "invalid {} metadata: {}", kind, msg }, + ); + let (size, align) = size_and_align + // for the purpose of validity, consider foreign types to have + // alignment and size determined by the layout (size will be 0, + // alignment should take attributes into account). + .unwrap_or_else(|| (place.layout.size, place.layout.align.abi)); + // Direct call to `check_ptr_access_align` checks alignment even on CTFE machines. + try_validation!( + self.ecx.check_ptr_access_align( + place.ptr, + size, + align, + CheckInAllocMsg::InboundsTest, // will anyway be replaced by validity message + ), + self.path, + err_ub!(AlignmentCheckFailed { required, has }) => + { + "an unaligned {kind} (required {} byte alignment but found {})", + required.bytes(), + has.bytes() + }, + err_ub!(DanglingIntPointer(0, _)) => + { "a null {kind}" }, + err_ub!(DanglingIntPointer(i, _)) => + { "a dangling {kind} (address {i:#x} is unallocated)" }, + err_ub!(PointerOutOfBounds { .. }) => + { "a dangling {kind} (going beyond the bounds of its allocation)" }, + // This cannot happen during const-eval (because interning already detects + // dangling pointers), but it can happen in Miri. + err_ub!(PointerUseAfterFree(..)) => + { "a dangling {kind} (use-after-free)" }, + ); + // Do not allow pointers to uninhabited types. + if place.layout.abi.is_uninhabited() { + throw_validation_failure!(self.path, + { "a {kind} pointing to uninhabited type {}", place.layout.ty } + ) + } + // Recursive checking + if let Some(ref mut ref_tracking) = self.ref_tracking { + // Proceed recursively even for ZST, no reason to skip them! + // `!` is a ZST and we want to validate it. + if let Ok((alloc_id, _offset, _prov)) = self.ecx.ptr_try_get_alloc_id(place.ptr) { + // Special handling for pointers to statics (irrespective of their type). + let alloc_kind = self.ecx.tcx.try_get_global_alloc(alloc_id); + if let Some(GlobalAlloc::Static(did)) = alloc_kind { + assert!(!self.ecx.tcx.is_thread_local_static(did)); + assert!(self.ecx.tcx.is_static(did)); + if matches!( + self.ctfe_mode, + Some(CtfeValidationMode::Const { allow_static_ptrs: false, .. }) + ) { + // See const_eval::machine::MemoryExtra::can_access_statics for why + // this check is so important. + // This check is reachable when the const just referenced the static, + // but never read it (so we never entered `before_access_global`). + throw_validation_failure!(self.path, + { "a {} pointing to a static variable", kind } + ); + } + // We skip checking other statics. These statics must be sound by + // themselves, and the only way to get broken statics here is by using + // unsafe code. + // The reasons we don't check other statics is twofold. For one, in all + // sound cases, the static was already validated on its own, and second, we + // trigger cycle errors if we try to compute the value of the other static + // and that static refers back to us. + // We might miss const-invalid data, + // but things are still sound otherwise (in particular re: consts + // referring to statics). + return Ok(()); + } + } + let path = &self.path; + ref_tracking.track(place, || { + // We need to clone the path anyway, make sure it gets created + // with enough space for the additional `Deref`. + let mut new_path = Vec::with_capacity(path.len() + 1); + new_path.extend(path); + new_path.push(PathElem::Deref); + new_path + }); + } + Ok(()) + } + + fn read_scalar( + &self, + op: &OpTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx, ScalarMaybeUninit<M::Provenance>> { + self.ecx.read_scalar(op) + } + + fn read_immediate_forced( + &self, + op: &OpTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx, Immediate<M::Provenance>> { + Ok(*self.ecx.read_immediate_raw(op, /*force*/ true)?.unwrap()) + } + + /// Check if this is a value of primitive type, and if yes check the validity of the value + /// at that type. Return `true` if the type is indeed primitive. + fn try_visit_primitive( + &mut self, + value: &OpTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx, bool> { + // Go over all the primitive types + let ty = value.layout.ty; + match ty.kind() { + ty::Bool => { + let value = self.read_scalar(value)?; + try_validation!( + value.to_bool(), + self.path, + err_ub!(InvalidBool(..)) | err_ub!(InvalidUninitBytes(None)) => + { "{:x}", value } expected { "a boolean" }, + ); + Ok(true) + } + ty::Char => { + let value = self.read_scalar(value)?; + try_validation!( + value.to_char(), + self.path, + err_ub!(InvalidChar(..)) | err_ub!(InvalidUninitBytes(None)) => + { "{:x}", value } expected { "a valid unicode scalar value (in `0..=0x10FFFF` but not in `0xD800..=0xDFFF`)" }, + ); + Ok(true) + } + ty::Float(_) | ty::Int(_) | ty::Uint(_) => { + let value = self.read_scalar(value)?; + // NOTE: Keep this in sync with the array optimization for int/float + // types below! + if M::enforce_number_init(self.ecx) { + try_validation!( + value.check_init(), + self.path, + err_ub!(InvalidUninitBytes(..)) => + { "{:x}", value } expected { "initialized bytes" } + ); + } + // As a special exception we *do* match on a `Scalar` here, since we truly want + // to know its underlying representation (and *not* cast it to an integer). + let is_ptr = value.check_init().map_or(false, |v| matches!(v, Scalar::Ptr(..))); + if is_ptr { + throw_validation_failure!(self.path, + { "{:x}", value } expected { "plain (non-pointer) bytes" } + ) + } + Ok(true) + } + ty::RawPtr(..) => { + // We are conservative with uninit for integers, but try to + // actually enforce the strict rules for raw pointers (mostly because + // that lets us re-use `ref_to_mplace`). + let place = try_validation!( + self.ecx.read_immediate(value).and_then(|ref i| self.ecx.ref_to_mplace(i)), + self.path, + err_ub!(InvalidUninitBytes(None)) => { "uninitialized raw pointer" }, + ); + if place.layout.is_unsized() { + self.check_wide_ptr_meta(place.meta, place.layout)?; + } + Ok(true) + } + ty::Ref(_, ty, mutbl) => { + if matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { .. })) + && *mutbl == hir::Mutability::Mut + { + // A mutable reference inside a const? That does not seem right (except if it is + // a ZST). + let layout = self.ecx.layout_of(*ty)?; + if !layout.is_zst() { + throw_validation_failure!(self.path, { "mutable reference in a `const`" }); + } + } + self.check_safe_pointer(value, "reference")?; + Ok(true) + } + ty::FnPtr(_sig) => { + let value = try_validation!( + self.ecx.read_scalar(value).and_then(|v| v.check_init()), + self.path, + err_ub!(InvalidUninitBytes(None)) => { "uninitialized bytes" } expected { "a proper pointer or integer value" }, + ); + + // If we check references recursively, also check that this points to a function. + if let Some(_) = self.ref_tracking { + let ptr = value.to_pointer(self.ecx)?; + let _fn = try_validation!( + self.ecx.get_ptr_fn(ptr), + self.path, + err_ub!(DanglingIntPointer(..)) | + err_ub!(InvalidFunctionPointer(..)) => + { "{ptr}" } expected { "a function pointer" }, + ); + // FIXME: Check if the signature matches + } else { + // Otherwise (for standalone Miri), we have to still check it to be non-null. + if self.ecx.scalar_may_be_null(value)? { + throw_validation_failure!(self.path, { "a null function pointer" }); + } + } + Ok(true) + } + ty::Never => throw_validation_failure!(self.path, { "a value of the never type `!`" }), + ty::Foreign(..) | ty::FnDef(..) => { + // Nothing to check. + Ok(true) + } + // The above should be all the primitive types. The rest is compound, we + // check them by visiting their fields/variants. + ty::Adt(..) + | ty::Tuple(..) + | ty::Array(..) + | ty::Slice(..) + | ty::Str + | ty::Dynamic(..) + | ty::Closure(..) + | ty::Generator(..) => Ok(false), + // Some types only occur during typechecking, they have no layout. + // We should not see them here and we could not check them anyway. + ty::Error(_) + | ty::Infer(..) + | ty::Placeholder(..) + | ty::Bound(..) + | ty::Param(..) + | ty::Opaque(..) + | ty::Projection(..) + | ty::GeneratorWitness(..) => bug!("Encountered invalid type {:?}", ty), + } + } + + fn visit_scalar( + &mut self, + scalar: ScalarMaybeUninit<M::Provenance>, + scalar_layout: ScalarAbi, + ) -> InterpResult<'tcx> { + // We check `is_full_range` in a slightly complicated way because *if* we are checking + // number validity, then we want to ensure that `Scalar::Initialized` is indeed initialized, + // i.e. that we go over the `check_init` below. + let size = scalar_layout.size(self.ecx); + let is_full_range = match scalar_layout { + ScalarAbi::Initialized { .. } => { + if M::enforce_number_init(self.ecx) { + false // not "full" since uninit is not accepted + } else { + scalar_layout.is_always_valid(self.ecx) + } + } + ScalarAbi::Union { .. } => true, + }; + if is_full_range { + // Nothing to check. Cruciall we don't even `read_scalar` until here, since that would + // fail for `Union` scalars! + return Ok(()); + } + // We have something to check: it must at least be initialized. + let valid_range = scalar_layout.valid_range(self.ecx); + let WrappingRange { start, end } = valid_range; + let max_value = size.unsigned_int_max(); + assert!(end <= max_value); + let value = try_validation!( + scalar.check_init(), + self.path, + err_ub!(InvalidUninitBytes(None)) => { "{:x}", scalar } + expected { "something {}", wrapping_range_format(valid_range, max_value) }, + ); + let bits = match value.try_to_int() { + Ok(int) => int.assert_bits(size), + Err(_) => { + // So this is a pointer then, and casting to an int failed. + // Can only happen during CTFE. + // We support 2 kinds of ranges here: full range, and excluding zero. + if start == 1 && end == max_value { + // Only null is the niche. So make sure the ptr is NOT null. + if self.ecx.scalar_may_be_null(value)? { + throw_validation_failure!(self.path, + { "a potentially null pointer" } + expected { + "something that cannot possibly fail to be {}", + wrapping_range_format(valid_range, max_value) + } + ) + } else { + return Ok(()); + } + } else if scalar_layout.is_always_valid(self.ecx) { + // Easy. (This is reachable if `enforce_number_validity` is set.) + return Ok(()); + } else { + // Conservatively, we reject, because the pointer *could* have a bad + // value. + throw_validation_failure!(self.path, + { "a pointer" } + expected { + "something that cannot possibly fail to be {}", + wrapping_range_format(valid_range, max_value) + } + ) + } + } + }; + // Now compare. + if valid_range.contains(bits) { + Ok(()) + } else { + throw_validation_failure!(self.path, + { "{}", bits } + expected { "something {}", wrapping_range_format(valid_range, max_value) } + ) + } + } +} + +impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M> + for ValidityVisitor<'rt, 'mir, 'tcx, M> +{ + type V = OpTy<'tcx, M::Provenance>; + + #[inline(always)] + fn ecx(&self) -> &InterpCx<'mir, 'tcx, M> { + &self.ecx + } + + fn read_discriminant( + &mut self, + op: &OpTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx, VariantIdx> { + self.with_elem(PathElem::EnumTag, move |this| { + Ok(try_validation!( + this.ecx.read_discriminant(op), + this.path, + err_ub!(InvalidTag(val)) => + { "{:x}", val } expected { "a valid enum tag" }, + err_ub!(InvalidUninitBytes(None)) => + { "uninitialized bytes" } expected { "a valid enum tag" }, + ) + .1) + }) + } + + #[inline] + fn visit_field( + &mut self, + old_op: &OpTy<'tcx, M::Provenance>, + field: usize, + new_op: &OpTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx> { + let elem = self.aggregate_field_path_elem(old_op.layout, field); + self.with_elem(elem, move |this| this.visit_value(new_op)) + } + + #[inline] + fn visit_variant( + &mut self, + old_op: &OpTy<'tcx, M::Provenance>, + variant_id: VariantIdx, + new_op: &OpTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx> { + let name = match old_op.layout.ty.kind() { + ty::Adt(adt, _) => PathElem::Variant(adt.variant(variant_id).name), + // Generators also have variants + ty::Generator(..) => PathElem::GeneratorState(variant_id), + _ => bug!("Unexpected type with variant: {:?}", old_op.layout.ty), + }; + self.with_elem(name, move |this| this.visit_value(new_op)) + } + + #[inline(always)] + fn visit_union( + &mut self, + op: &OpTy<'tcx, M::Provenance>, + _fields: NonZeroUsize, + ) -> InterpResult<'tcx> { + // Special check preventing `UnsafeCell` inside unions in the inner part of constants. + if matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { inner: true, .. })) { + if !op.layout.ty.is_freeze(self.ecx.tcx.at(DUMMY_SP), self.ecx.param_env) { + throw_validation_failure!(self.path, { "`UnsafeCell` in a `const`" }); + } + } + Ok(()) + } + + #[inline] + fn visit_box(&mut self, op: &OpTy<'tcx, M::Provenance>) -> InterpResult<'tcx> { + self.check_safe_pointer(op, "box")?; + Ok(()) + } + + #[inline] + fn visit_value(&mut self, op: &OpTy<'tcx, M::Provenance>) -> InterpResult<'tcx> { + trace!("visit_value: {:?}, {:?}", *op, op.layout); + + // Check primitive types -- the leaves of our recursive descent. + if self.try_visit_primitive(op)? { + return Ok(()); + } + + // Special check preventing `UnsafeCell` in the inner part of constants + if let Some(def) = op.layout.ty.ty_adt_def() { + if matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { inner: true, .. })) + && def.is_unsafe_cell() + { + throw_validation_failure!(self.path, { "`UnsafeCell` in a `const`" }); + } + } + + // Recursively walk the value at its type. + self.walk_value(op)?; + + // *After* all of this, check the ABI. We need to check the ABI to handle + // types like `NonNull` where the `Scalar` info is more restrictive than what + // the fields say (`rustc_layout_scalar_valid_range_start`). + // But in most cases, this will just propagate what the fields say, + // and then we want the error to point at the field -- so, first recurse, + // then check ABI. + // + // FIXME: We could avoid some redundant checks here. For newtypes wrapping + // scalars, we do the same check on every "level" (e.g., first we check + // MyNewtype and then the scalar in there). + match op.layout.abi { + Abi::Uninhabited => { + throw_validation_failure!(self.path, + { "a value of uninhabited type {:?}", op.layout.ty } + ); + } + Abi::Scalar(scalar_layout) => { + // We use a 'forced' read because we always need a `Immediate` here + // and treating "partially uninit" as "fully uninit" is fine for us. + let scalar = self.read_immediate_forced(op)?.to_scalar_or_uninit(); + self.visit_scalar(scalar, scalar_layout)?; + } + Abi::ScalarPair(a_layout, b_layout) => { + // There is no `rustc_layout_scalar_valid_range_start` for pairs, so + // we would validate these things as we descend into the fields, + // but that can miss bugs in layout computation. Layout computation + // is subtle due to enums having ScalarPair layout, where one field + // is the discriminant. + if cfg!(debug_assertions) { + // We use a 'forced' read because we always need a `Immediate` here + // and treating "partially uninit" as "fully uninit" is fine for us. + let (a, b) = self.read_immediate_forced(op)?.to_scalar_or_uninit_pair(); + self.visit_scalar(a, a_layout)?; + self.visit_scalar(b, b_layout)?; + } + } + Abi::Vector { .. } => { + // No checks here, we assume layout computation gets this right. + // (This is harder to check since Miri does not represent these as `Immediate`. We + // also cannot use field projections since this might be a newtype around a vector.) + } + Abi::Aggregate { .. } => { + // Nothing to do. + } + } + + Ok(()) + } + + fn visit_aggregate( + &mut self, + op: &OpTy<'tcx, M::Provenance>, + fields: impl Iterator<Item = InterpResult<'tcx, Self::V>>, + ) -> InterpResult<'tcx> { + match op.layout.ty.kind() { + ty::Str => { + let mplace = op.assert_mem_place(); // strings are unsized and hence never immediate + let len = mplace.len(self.ecx)?; + try_validation!( + self.ecx.read_bytes_ptr(mplace.ptr, Size::from_bytes(len)), + self.path, + err_ub!(InvalidUninitBytes(..)) => { "uninitialized data in `str`" }, + ); + } + ty::Array(tys, ..) | ty::Slice(tys) + // This optimization applies for types that can hold arbitrary bytes (such as + // integer and floating point types) or for structs or tuples with no fields. + // FIXME(wesleywiser) This logic could be extended further to arbitrary structs + // or tuples made up of integer/floating point types or inhabited ZSTs with no + // padding. + if matches!(tys.kind(), ty::Int(..) | ty::Uint(..) | ty::Float(..)) + => + { + // Optimized handling for arrays of integer/float type. + + // This is the length of the array/slice. + let len = op.len(self.ecx)?; + // This is the element type size. + let layout = self.ecx.layout_of(*tys)?; + // This is the size in bytes of the whole array. (This checks for overflow.) + let size = layout.size * len; + // If the size is 0, there is nothing to check. + // (`size` can only be 0 of `len` is 0, and empty arrays are always valid.) + if size == Size::ZERO { + return Ok(()); + } + // Now that we definitely have a non-ZST array, we know it lives in memory. + let mplace = match op.try_as_mplace() { + Ok(mplace) => mplace, + Err(imm) => match *imm { + Immediate::Uninit => + throw_validation_failure!(self.path, { "uninitialized bytes" }), + Immediate::Scalar(..) | Immediate::ScalarPair(..) => + bug!("arrays/slices can never have Scalar/ScalarPair layout"), + } + }; + + // Optimization: we just check the entire range at once. + // NOTE: Keep this in sync with the handling of integer and float + // types above, in `visit_primitive`. + // In run-time mode, we accept pointers in here. This is actually more + // permissive than a per-element check would be, e.g., we accept + // a &[u8] that contains a pointer even though bytewise checking would + // reject it. However, that's good: We don't inherently want + // to reject those pointers, we just do not have the machinery to + // talk about parts of a pointer. + // We also accept uninit, for consistency with the slow path. + let alloc = self.ecx.get_ptr_alloc(mplace.ptr, size, mplace.align)?.expect("we already excluded size 0"); + + match alloc.check_bytes( + alloc_range(Size::ZERO, size), + /*allow_uninit*/ !M::enforce_number_init(self.ecx), + /*allow_ptr*/ false, + ) { + // In the happy case, we needn't check anything else. + Ok(()) => {} + // Some error happened, try to provide a more detailed description. + Err(err) => { + // For some errors we might be able to provide extra information. + // (This custom logic does not fit the `try_validation!` macro.) + match err.kind() { + err_ub!(InvalidUninitBytes(Some((_alloc_id, access)))) => { + // Some byte was uninitialized, determine which + // element that byte belongs to so we can + // provide an index. + let i = usize::try_from( + access.uninit.start.bytes() / layout.size.bytes(), + ) + .unwrap(); + self.path.push(PathElem::ArrayElem(i)); + + throw_validation_failure!(self.path, { "uninitialized bytes" }) + } + + // Propagate upwards (that will also check for unexpected errors). + _ => return Err(err), + } + } + } + } + // Fast path for arrays and slices of ZSTs. We only need to check a single ZST element + // of an array and not all of them, because there's only a single value of a specific + // ZST type, so either validation fails for all elements or none. + ty::Array(tys, ..) | ty::Slice(tys) if self.ecx.layout_of(*tys)?.is_zst() => { + // Validate just the first element (if any). + self.walk_aggregate(op, fields.take(1))? + } + _ => { + self.walk_aggregate(op, fields)? // default handler + } + } + Ok(()) + } +} + +impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { + fn validate_operand_internal( + &self, + op: &OpTy<'tcx, M::Provenance>, + path: Vec<PathElem>, + ref_tracking: Option<&mut RefTracking<MPlaceTy<'tcx, M::Provenance>, Vec<PathElem>>>, + ctfe_mode: Option<CtfeValidationMode>, + ) -> InterpResult<'tcx> { + trace!("validate_operand_internal: {:?}, {:?}", *op, op.layout.ty); + + // Construct a visitor + let mut visitor = ValidityVisitor { path, ref_tracking, ctfe_mode, ecx: self }; + + // Run it. + match visitor.visit_value(&op) { + Ok(()) => Ok(()), + // Pass through validation failures. + Err(err) if matches!(err.kind(), err_ub!(ValidationFailure { .. })) => Err(err), + // Complain about any other kind of UB error -- those are bad because we'd like to + // report them in a way that shows *where* in the value the issue lies. + Err(err) if matches!(err.kind(), InterpError::UndefinedBehavior(_)) => { + err.print_backtrace(); + bug!("Unexpected Undefined Behavior error during validation: {}", err); + } + // Pass through everything else. + Err(err) => Err(err), + } + } + + /// This function checks the data at `op` to be const-valid. + /// `op` is assumed to cover valid memory if it is an indirect operand. + /// It will error if the bits at the destination do not match the ones described by the layout. + /// + /// `ref_tracking` is used to record references that we encounter so that they + /// can be checked recursively by an outside driving loop. + /// + /// `constant` controls whether this must satisfy the rules for constants: + /// - no pointers to statics. + /// - no `UnsafeCell` or non-ZST `&mut`. + #[inline(always)] + pub fn const_validate_operand( + &self, + op: &OpTy<'tcx, M::Provenance>, + path: Vec<PathElem>, + ref_tracking: &mut RefTracking<MPlaceTy<'tcx, M::Provenance>, Vec<PathElem>>, + ctfe_mode: CtfeValidationMode, + ) -> InterpResult<'tcx> { + self.validate_operand_internal(op, path, Some(ref_tracking), Some(ctfe_mode)) + } + + /// This function checks the data at `op` to be runtime-valid. + /// `op` is assumed to cover valid memory if it is an indirect operand. + /// It will error if the bits at the destination do not match the ones described by the layout. + #[inline(always)] + pub fn validate_operand(&self, op: &OpTy<'tcx, M::Provenance>) -> InterpResult<'tcx> { + self.validate_operand_internal(op, vec![], None, None) + } +} |