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//! 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::fmt::Write;
use std::num::NonZeroUsize;
use either::{Left, Right};
use rustc_ast::Mutability;
use rustc_data_structures::fx::FxHashSet;
use rustc_hir as hir;
use rustc_middle::mir::interpret::{
ExpectedKind, InterpError, InvalidMetaKind, PointerKind, ValidationErrorInfo,
ValidationErrorKind, ValidationErrorKind::*,
};
use rustc_middle::ty;
use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
use rustc_span::symbol::{sym, Symbol};
use rustc_target::abi::{
Abi, FieldIdx, Scalar as ScalarAbi, Size, VariantIdx, Variants, WrappingRange,
};
use std::hash::Hash;
use super::{
AllocId, CheckInAllocMsg, GlobalAlloc, ImmTy, Immediate, InterpCx, InterpResult, MPlaceTy,
Machine, MemPlaceMeta, OpTy, Pointer, Projectable, Scalar, ValueVisitor,
};
// for the validation errors
use super::InterpError::UndefinedBehavior as Ub;
use super::InterpError::Unsupported as Unsup;
use super::UndefinedBehaviorInfo::*;
use super::UnsupportedOpInfo::*;
macro_rules! throw_validation_failure {
($where:expr, $kind: expr) => {{
let where_ = &$where;
let path = if !where_.is_empty() {
let mut path = String::new();
write_path(&mut path, where_);
Some(path)
} else {
None
};
throw_ub!(ValidationError(ValidationErrorInfo { path, kind: $kind }))
}};
}
/// If $e throws an error matching the pattern, throw a validation failure.
/// Other errors are passed back to the caller, unchanged -- and if they reach the root of
/// the visitor, we make sure only validation errors and `InvalidProgram` errors are left.
/// This lets you use the patterns as a kind of validation list, asserting which errors
/// can possibly happen:
///
/// ```ignore(illustrative)
/// let v = try_validation!(some_fn(), some_path, {
/// Foo | Bar | Baz => { "some failure" },
/// });
/// ```
///
/// The patterns must be of type `UndefinedBehaviorInfo`.
/// An additional expected parameter can also be added to the failure message:
///
/// ```ignore(illustrative)
/// let v = try_validation!(some_fn(), some_path, {
/// Foo | Bar | Baz => { "some failure" } expected { "something that wasn't a failure" },
/// });
/// ```
///
/// An additional nicety is that both parameters actually take format args, so you can just write
/// the format string in directly:
///
/// ```ignore(illustrative)
/// let v = try_validation!(some_fn(), some_path, {
/// Foo | Bar | Baz => { "{:?}", some_failure } expected { "{}", expected_value },
/// });
/// ```
///
macro_rules! try_validation {
($e:expr, $where:expr,
$( $( $p:pat_param )|+ => $kind: 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,
$kind
)
),+,
#[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: Clone + 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.clone(), 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.clone()) {
trace!("Recursing below ptr {:#?}", op);
let path = path();
// Remember to come back to this later.
self.todo.push((op, path));
}
}
}
// FIXME make this translatable as well?
/// 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()
}
}
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 captures = self.ecx.tcx.closure_captures(local_def_id);
if let Some(captured_place) = captures.get(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[FieldIdx::from_usize(field)].name)
}
Variants::Multiple { .. } => bug!("we handled variants above"),
}
}
// other ADTs
ty::Adt(def, _) => {
PathElem::Field(def.non_enum_variant().fields[FieldIdx::from_usize(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 read_immediate(
&self,
op: &OpTy<'tcx, M::Provenance>,
expected: ExpectedKind,
) -> InterpResult<'tcx, ImmTy<'tcx, M::Provenance>> {
Ok(try_validation!(
self.ecx.read_immediate(op),
self.path,
Ub(InvalidUninitBytes(None)) =>
Uninit { expected },
// The `Unsup` cases can only occur during CTFE
Unsup(ReadPointerAsInt(_)) =>
PointerAsInt { expected },
Unsup(ReadPartialPointer(_)) =>
PartialPointer,
))
}
fn read_scalar(
&self,
op: &OpTy<'tcx, M::Provenance>,
expected: ExpectedKind,
) -> InterpResult<'tcx, Scalar<M::Provenance>> {
Ok(self.read_immediate(op, expected)?.to_scalar())
}
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(_, _, ty::Dyn) => {
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,
Ub(DanglingIntPointer(..) | InvalidVTablePointer(..)) =>
InvalidVTablePtr { value: format!("{vtable}") }
);
// FIXME: check if the type/trait match what ty::Dynamic says?
}
ty::Slice(..) | ty::Str => {
let _len = meta.unwrap_meta().to_target_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>,
ptr_kind: PointerKind,
) -> InterpResult<'tcx> {
// Not using `deref_pointer` since we do the dereferenceable check ourselves below.
let place = self.ecx.ref_to_mplace(&self.read_immediate(value, ptr_kind.into())?)?;
// Handle wide pointers.
// Check metadata early, for better diagnostics
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,
Ub(InvalidMeta(msg)) => match msg {
InvalidMetaKind::SliceTooBig => InvalidMetaSliceTooLarge { ptr_kind },
InvalidMetaKind::TooBig => InvalidMetaTooLarge { ptr_kind },
}
);
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,
Ub(AlignmentCheckFailed { required, has }) => UnalignedPtr {
ptr_kind,
required_bytes: required.bytes(),
found_bytes: has.bytes()
},
Ub(DanglingIntPointer(0, _)) => NullPtr { ptr_kind },
Ub(DanglingIntPointer(i, _)) => DanglingPtrNoProvenance {
ptr_kind,
// FIXME this says "null pointer" when null but we need translate
pointer: format!("{}", Pointer::<Option<AllocId>>::from_addr_invalid(*i))
},
Ub(PointerOutOfBounds { .. }) => DanglingPtrOutOfBounds {
ptr_kind
},
// This cannot happen during const-eval (because interning already detects
// dangling pointers), but it can happen in Miri.
Ub(PointerUseAfterFree(..)) => DanglingPtrUseAfterFree {
ptr_kind,
},
);
// Do not allow pointers to uninhabited types.
if place.layout.abi.is_uninhabited() {
let ty = place.layout.ty;
throw_validation_failure!(self.path, PtrToUninhabited { ptr_kind, ty })
}
// Recursive checking
if let Some(ref_tracking) = self.ref_tracking.as_deref_mut() {
// 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()) {
// Let's see what kind of memory this points to.
let alloc_kind = self.ecx.tcx.try_get_global_alloc(alloc_id);
match alloc_kind {
Some(GlobalAlloc::Static(did)) => {
// Special handling for pointers to statics (irrespective of their type).
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, PtrToStatic { ptr_kind });
}
// We skip recursively 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(());
}
Some(GlobalAlloc::Memory(alloc)) => {
if alloc.inner().mutability == Mutability::Mut
&& matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { .. }))
{
// This should be unreachable, but if someone manages to copy a pointer
// out of a `static`, then that pointer might point to mutable memory,
// and we would catch that here.
throw_validation_failure!(self.path, PtrToMut { ptr_kind });
}
}
// Nothing to check for these.
None | Some(GlobalAlloc::Function(..) | GlobalAlloc::VTable(..)) => {}
}
}
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(())
}
/// 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.
///
/// Note that not all of these have `FieldsShape::Primitive`, e.g. wide references.
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, ExpectedKind::Bool)?;
try_validation!(
value.to_bool(),
self.path,
Ub(InvalidBool(..)) => ValidationErrorKind::InvalidBool {
value: format!("{value:x}"),
}
);
Ok(true)
}
ty::Char => {
let value = self.read_scalar(value, ExpectedKind::Char)?;
try_validation!(
value.to_char(),
self.path,
Ub(InvalidChar(..)) => ValidationErrorKind::InvalidChar {
value: format!("{value:x}"),
}
);
Ok(true)
}
ty::Float(_) | ty::Int(_) | ty::Uint(_) => {
// NOTE: Keep this in sync with the array optimization for int/float
// types below!
self.read_scalar(
value,
if matches!(ty.kind(), ty::Float(..)) {
ExpectedKind::Float
} else {
ExpectedKind::Int
},
)?;
Ok(true)
}
ty::RawPtr(..) => {
let place =
self.ecx.ref_to_mplace(&self.read_immediate(value, ExpectedKind::RawPtr)?)?;
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 == 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, MutableRefInConst);
}
}
self.check_safe_pointer(value, PointerKind::Ref)?;
Ok(true)
}
ty::FnPtr(_sig) => {
let value = self.read_scalar(value, ExpectedKind::FnPtr)?;
// 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,
Ub(DanglingIntPointer(..) | InvalidFunctionPointer(..)) =>
InvalidFnPtr { value: format!("{ptr}") },
);
// 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, NullFnPtr);
}
}
Ok(true)
}
ty::Never => throw_validation_failure!(self.path, NeverVal),
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::Alias(..)
| ty::GeneratorWitness(..) => bug!("Encountered invalid type {:?}", ty),
}
}
fn visit_scalar(
&mut self,
scalar: Scalar<M::Provenance>,
scalar_layout: ScalarAbi,
) -> InterpResult<'tcx> {
let size = scalar_layout.size(self.ecx);
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 bits = match scalar.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(scalar)? {
throw_validation_failure!(
self.path,
NullablePtrOutOfRange { range: 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,
PtrOutOfRange { range: valid_range, max_value }
)
}
}
};
// Now compare.
if valid_range.contains(bits) {
Ok(())
} else {
throw_validation_failure!(
self.path,
OutOfRange { value: format!("{bits}"), range: 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,
Ub(InvalidTag(val)) => InvalidEnumTag {
value: format!("{val:x}"),
},
Ub(UninhabitedEnumVariantRead(_)) => UninhabitedEnumVariant,
// Uninit / bad provenance are not possible since the field was already previously
// checked at its integer type.
))
})
}
#[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, self.ecx.param_env) {
throw_validation_failure!(self.path, UnsafeCell);
}
}
Ok(())
}
#[inline]
fn visit_box(&mut self, op: &OpTy<'tcx, M::Provenance>) -> InterpResult<'tcx> {
self.check_safe_pointer(op, PointerKind::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);
}
}
// Recursively walk the value at its type. Apply optimizations for some large types.
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_strip_provenance(mplace.ptr(), Size::from_bytes(len)),
self.path,
Ub(InvalidUninitBytes(..)) => Uninit { expected: ExpectedKind::Str },
Unsup(ReadPointerAsInt(_)) => PointerAsInt { expected: ExpectedKind::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(..))
=>
{
let expected = if tys.is_integral() { ExpectedKind::Int } else { ExpectedKind::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.as_mplace_or_imm() {
Left(mplace) => mplace,
Right(imm) => match *imm {
Immediate::Uninit =>
throw_validation_failure!(self.path, Uninit { expected }),
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.get_bytes_strip_provenance() {
// 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() {
Ub(InvalidUninitBytes(Some((_alloc_id, access)))) | Unsup(ReadPointerAsInt(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.bad.start.bytes() / layout.size.bytes(),
)
.unwrap();
self.path.push(PathElem::ArrayElem(i));
if matches!(err.kind(), Ub(InvalidUninitBytes(_))) {
throw_validation_failure!(self.path, Uninit { expected })
} else {
throw_validation_failure!(self.path, PointerAsInt { expected })
}
}
// 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).
if op.len(self.ecx)? > 0 {
self.visit_field(op, 0, &self.ecx.project_index(op, 0)?)?;
}
}
_ => {
self.walk_value(op)?; // default handler
}
}
// *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 => {
let ty = op.layout.ty;
throw_validation_failure!(self.path, UninhabitedVal { ty });
}
Abi::Scalar(scalar_layout) => {
if !scalar_layout.is_uninit_valid() {
// There is something to check here.
let scalar = self.read_scalar(op, ExpectedKind::InitScalar)?;
self.visit_scalar(scalar, scalar_layout)?;
}
}
Abi::ScalarPair(a_layout, b_layout) => {
// We can only proceed if *both* scalars need to be initialized.
// FIXME: find a way to also check ScalarPair when one side can be uninit but
// the other must be init.
if !a_layout.is_uninit_valid() && !b_layout.is_uninit_valid() {
let (a, b) =
self.read_immediate(op, ExpectedKind::InitScalar)?.to_scalar_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(())
}
}
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 and "invalid program" issues.
Err(err)
if matches!(
err.kind(),
err_ub!(ValidationError { .. }) | InterpError::InvalidProgram(_)
) =>
{
Err(err)
}
// Complain about any other kind of 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) => {
bug!(
"Unexpected Undefined Behavior error during validation: {}",
self.format_error(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> {
// Note that we *could* actually be in CTFE here with `-Zextra-const-ub-checks`, but it's
// still correct to not use `ctfe_mode`: that mode is for validation of the final constant
// value, it rules out things like `UnsafeCell` in awkward places. It also can make checking
// recurse through references which, for now, we don't want here, either.
self.validate_operand_internal(op, vec![], None, None)
}
}