rustc_const_eval/interpret/place.rs
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//! Computations on places -- field projections, going from mir::Place, and writing
//! into a place.
//! All high-level functions to write to memory work on places as destinations.
use std::assert_matches::assert_matches;
use either::{Either, Left, Right};
use rustc_abi::{Align, BackendRepr, HasDataLayout, Size};
use rustc_ast::Mutability;
use rustc_middle::ty::Ty;
use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
use rustc_middle::{bug, mir, span_bug};
use tracing::{instrument, trace};
use super::{
AllocRef, AllocRefMut, CheckAlignMsg, CtfeProvenance, ImmTy, Immediate, InterpCx, InterpResult,
Machine, MemoryKind, Misalignment, OffsetMode, OpTy, Operand, Pointer, Projectable, Provenance,
Scalar, alloc_range, interp_ok, mir_assign_valid_types,
};
#[derive(Copy, Clone, Hash, PartialEq, Eq, Debug)]
/// Information required for the sound usage of a `MemPlace`.
pub enum MemPlaceMeta<Prov: Provenance = CtfeProvenance> {
/// The unsized payload (e.g. length for slices or vtable pointer for trait objects).
Meta(Scalar<Prov>),
/// `Sized` types or unsized `extern type`
None,
}
impl<Prov: Provenance> MemPlaceMeta<Prov> {
#[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980)
pub fn unwrap_meta(self) -> Scalar<Prov> {
match self {
Self::Meta(s) => s,
Self::None => {
bug!("expected wide pointer extra data (e.g. slice length or trait object vtable)")
}
}
}
#[inline(always)]
pub fn has_meta(self) -> bool {
match self {
Self::Meta(_) => true,
Self::None => false,
}
}
}
#[derive(Copy, Clone, Hash, PartialEq, Eq, Debug)]
pub(super) struct MemPlace<Prov: Provenance = CtfeProvenance> {
/// The pointer can be a pure integer, with the `None` provenance.
pub ptr: Pointer<Option<Prov>>,
/// Metadata for unsized places. Interpretation is up to the type.
/// Must not be present for sized types, but can be missing for unsized types
/// (e.g., `extern type`).
pub meta: MemPlaceMeta<Prov>,
/// Stores whether this place was created based on a sufficiently aligned pointer.
misaligned: Option<Misalignment>,
}
impl<Prov: Provenance> MemPlace<Prov> {
/// Adjust the provenance of the main pointer (metadata is unaffected).
fn map_provenance(self, f: impl FnOnce(Prov) -> Prov) -> Self {
MemPlace { ptr: self.ptr.map_provenance(|p| p.map(f)), ..self }
}
/// Turn a mplace into a (thin or wide) pointer, as a reference, pointing to the same space.
#[inline]
fn to_ref(self, cx: &impl HasDataLayout) -> Immediate<Prov> {
Immediate::new_pointer_with_meta(self.ptr, self.meta, cx)
}
#[inline]
// Not called `offset_with_meta` to avoid confusion with the trait method.
fn offset_with_meta_<'tcx, M: Machine<'tcx, Provenance = Prov>>(
self,
offset: Size,
mode: OffsetMode,
meta: MemPlaceMeta<Prov>,
ecx: &InterpCx<'tcx, M>,
) -> InterpResult<'tcx, Self> {
debug_assert!(
!meta.has_meta() || self.meta.has_meta(),
"cannot use `offset_with_meta` to add metadata to a place"
);
let ptr = match mode {
OffsetMode::Inbounds => {
ecx.ptr_offset_inbounds(self.ptr, offset.bytes().try_into().unwrap())?
}
OffsetMode::Wrapping => self.ptr.wrapping_offset(offset, ecx),
};
interp_ok(MemPlace { ptr, meta, misaligned: self.misaligned })
}
}
/// A MemPlace with its layout. Constructing it is only possible in this module.
#[derive(Clone, Hash, Eq, PartialEq)]
pub struct MPlaceTy<'tcx, Prov: Provenance = CtfeProvenance> {
mplace: MemPlace<Prov>,
pub layout: TyAndLayout<'tcx>,
}
impl<Prov: Provenance> std::fmt::Debug for MPlaceTy<'_, Prov> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
// Printing `layout` results in too much noise; just print a nice version of the type.
f.debug_struct("MPlaceTy")
.field("mplace", &self.mplace)
.field("ty", &format_args!("{}", self.layout.ty))
.finish()
}
}
impl<'tcx, Prov: Provenance> MPlaceTy<'tcx, Prov> {
/// Produces a MemPlace that works for ZST but nothing else.
/// Conceptually this is a new allocation, but it doesn't actually create an allocation so you
/// don't need to worry about memory leaks.
#[inline]
pub fn fake_alloc_zst(layout: TyAndLayout<'tcx>) -> Self {
assert!(layout.is_zst());
let align = layout.align.abi;
let ptr = Pointer::from_addr_invalid(align.bytes()); // no provenance, absolute address
MPlaceTy { mplace: MemPlace { ptr, meta: MemPlaceMeta::None, misaligned: None }, layout }
}
/// Adjust the provenance of the main pointer (metadata is unaffected).
pub fn map_provenance(self, f: impl FnOnce(Prov) -> Prov) -> Self {
MPlaceTy { mplace: self.mplace.map_provenance(f), ..self }
}
#[inline(always)]
pub(super) fn mplace(&self) -> &MemPlace<Prov> {
&self.mplace
}
#[inline(always)]
pub fn ptr(&self) -> Pointer<Option<Prov>> {
self.mplace.ptr
}
#[inline(always)]
pub fn to_ref(&self, cx: &impl HasDataLayout) -> Immediate<Prov> {
self.mplace.to_ref(cx)
}
}
impl<'tcx, Prov: Provenance> Projectable<'tcx, Prov> for MPlaceTy<'tcx, Prov> {
#[inline(always)]
fn layout(&self) -> TyAndLayout<'tcx> {
self.layout
}
#[inline(always)]
fn meta(&self) -> MemPlaceMeta<Prov> {
self.mplace.meta
}
fn offset_with_meta<M: Machine<'tcx, Provenance = Prov>>(
&self,
offset: Size,
mode: OffsetMode,
meta: MemPlaceMeta<Prov>,
layout: TyAndLayout<'tcx>,
ecx: &InterpCx<'tcx, M>,
) -> InterpResult<'tcx, Self> {
interp_ok(MPlaceTy {
mplace: self.mplace.offset_with_meta_(offset, mode, meta, ecx)?,
layout,
})
}
#[inline(always)]
fn to_op<M: Machine<'tcx, Provenance = Prov>>(
&self,
_ecx: &InterpCx<'tcx, M>,
) -> InterpResult<'tcx, OpTy<'tcx, M::Provenance>> {
interp_ok(self.clone().into())
}
}
#[derive(Copy, Clone, Debug)]
pub(super) enum Place<Prov: Provenance = CtfeProvenance> {
/// A place referring to a value allocated in the `Memory` system.
Ptr(MemPlace<Prov>),
/// To support alloc-free locals, we are able to write directly to a local. The offset indicates
/// where in the local this place is located; if it is `None`, no projection has been applied
/// and the type of the place is exactly the type of the local.
/// Such projections are meaningful even if the offset is 0, since they can change layouts.
/// (Without that optimization, we'd just always be a `MemPlace`.)
/// `Local` places always refer to the current stack frame, so they are unstable under
/// function calls/returns and switching betweens stacks of different threads!
/// We carry around the address of the `locals` buffer of the correct stack frame as a sanity
/// check to be able to catch some cases of using a dangling `Place`.
///
/// This variant shall not be used for unsized types -- those must always live in memory.
Local { local: mir::Local, offset: Option<Size>, locals_addr: usize },
}
/// An evaluated place, together with its type.
///
/// This may reference a stack frame by its index, so `PlaceTy` should generally not be kept around
/// for longer than a single operation. Popping and then pushing a stack frame can make `PlaceTy`
/// point to the wrong destination. If the interpreter has multiple stacks, stack switching will
/// also invalidate a `PlaceTy`.
#[derive(Clone)]
pub struct PlaceTy<'tcx, Prov: Provenance = CtfeProvenance> {
place: Place<Prov>, // Keep this private; it helps enforce invariants.
pub layout: TyAndLayout<'tcx>,
}
impl<Prov: Provenance> std::fmt::Debug for PlaceTy<'_, Prov> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
// Printing `layout` results in too much noise; just print a nice version of the type.
f.debug_struct("PlaceTy")
.field("place", &self.place)
.field("ty", &format_args!("{}", self.layout.ty))
.finish()
}
}
impl<'tcx, Prov: Provenance> From<MPlaceTy<'tcx, Prov>> for PlaceTy<'tcx, Prov> {
#[inline(always)]
fn from(mplace: MPlaceTy<'tcx, Prov>) -> Self {
PlaceTy { place: Place::Ptr(mplace.mplace), layout: mplace.layout }
}
}
impl<'tcx, Prov: Provenance> PlaceTy<'tcx, Prov> {
#[inline(always)]
pub(super) fn place(&self) -> &Place<Prov> {
&self.place
}
/// A place is either an mplace or some local.
#[inline(always)]
pub fn as_mplace_or_local(
&self,
) -> Either<MPlaceTy<'tcx, Prov>, (mir::Local, Option<Size>, usize, TyAndLayout<'tcx>)> {
match self.place {
Place::Ptr(mplace) => Left(MPlaceTy { mplace, layout: self.layout }),
Place::Local { local, offset, locals_addr } => {
Right((local, offset, locals_addr, self.layout))
}
}
}
#[inline(always)]
#[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980)
pub fn assert_mem_place(&self) -> MPlaceTy<'tcx, Prov> {
self.as_mplace_or_local().left().unwrap_or_else(|| {
bug!(
"PlaceTy of type {} was a local when it was expected to be an MPlace",
self.layout.ty
)
})
}
}
impl<'tcx, Prov: Provenance> Projectable<'tcx, Prov> for PlaceTy<'tcx, Prov> {
#[inline(always)]
fn layout(&self) -> TyAndLayout<'tcx> {
self.layout
}
#[inline]
fn meta(&self) -> MemPlaceMeta<Prov> {
match self.as_mplace_or_local() {
Left(mplace) => mplace.meta(),
Right(_) => {
debug_assert!(self.layout.is_sized(), "unsized locals should live in memory");
MemPlaceMeta::None
}
}
}
fn offset_with_meta<M: Machine<'tcx, Provenance = Prov>>(
&self,
offset: Size,
mode: OffsetMode,
meta: MemPlaceMeta<Prov>,
layout: TyAndLayout<'tcx>,
ecx: &InterpCx<'tcx, M>,
) -> InterpResult<'tcx, Self> {
interp_ok(match self.as_mplace_or_local() {
Left(mplace) => mplace.offset_with_meta(offset, mode, meta, layout, ecx)?.into(),
Right((local, old_offset, locals_addr, _)) => {
debug_assert!(layout.is_sized(), "unsized locals should live in memory");
assert_matches!(meta, MemPlaceMeta::None); // we couldn't store it anyway...
// `Place::Local` are always in-bounds of their surrounding local, so we can just
// check directly if this remains in-bounds. This cannot actually be violated since
// projections are type-checked and bounds-checked.
assert!(offset + layout.size <= self.layout.size);
// Size `+`, ensures no overflow.
let new_offset = old_offset.unwrap_or(Size::ZERO) + offset;
PlaceTy {
place: Place::Local { local, offset: Some(new_offset), locals_addr },
layout,
}
}
})
}
#[inline(always)]
fn to_op<M: Machine<'tcx, Provenance = Prov>>(
&self,
ecx: &InterpCx<'tcx, M>,
) -> InterpResult<'tcx, OpTy<'tcx, M::Provenance>> {
ecx.place_to_op(self)
}
}
// These are defined here because they produce a place.
impl<'tcx, Prov: Provenance> OpTy<'tcx, Prov> {
#[inline(always)]
pub fn as_mplace_or_imm(&self) -> Either<MPlaceTy<'tcx, Prov>, ImmTy<'tcx, Prov>> {
match self.op() {
Operand::Indirect(mplace) => Left(MPlaceTy { mplace: *mplace, layout: self.layout }),
Operand::Immediate(imm) => Right(ImmTy::from_immediate(*imm, self.layout)),
}
}
#[inline(always)]
#[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980)
pub fn assert_mem_place(&self) -> MPlaceTy<'tcx, Prov> {
self.as_mplace_or_imm().left().unwrap_or_else(|| {
bug!(
"OpTy of type {} was immediate when it was expected to be an MPlace",
self.layout.ty
)
})
}
}
/// The `Weiteable` trait describes interpreter values that can be written to.
pub trait Writeable<'tcx, Prov: Provenance>: Projectable<'tcx, Prov> {
fn to_place(&self) -> PlaceTy<'tcx, Prov>;
fn force_mplace<M: Machine<'tcx, Provenance = Prov>>(
&self,
ecx: &mut InterpCx<'tcx, M>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, Prov>>;
}
impl<'tcx, Prov: Provenance> Writeable<'tcx, Prov> for PlaceTy<'tcx, Prov> {
#[inline(always)]
fn to_place(&self) -> PlaceTy<'tcx, Prov> {
self.clone()
}
#[inline(always)]
fn force_mplace<M: Machine<'tcx, Provenance = Prov>>(
&self,
ecx: &mut InterpCx<'tcx, M>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, Prov>> {
ecx.force_allocation(self)
}
}
impl<'tcx, Prov: Provenance> Writeable<'tcx, Prov> for MPlaceTy<'tcx, Prov> {
#[inline(always)]
fn to_place(&self) -> PlaceTy<'tcx, Prov> {
self.clone().into()
}
#[inline(always)]
fn force_mplace<M: Machine<'tcx, Provenance = Prov>>(
&self,
_ecx: &mut InterpCx<'tcx, M>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, Prov>> {
interp_ok(self.clone())
}
}
// FIXME: Working around https://github.com/rust-lang/rust/issues/54385
impl<'tcx, Prov, M> InterpCx<'tcx, M>
where
Prov: Provenance,
M: Machine<'tcx, Provenance = Prov>,
{
fn ptr_with_meta_to_mplace(
&self,
ptr: Pointer<Option<M::Provenance>>,
meta: MemPlaceMeta<M::Provenance>,
layout: TyAndLayout<'tcx>,
unaligned: bool,
) -> MPlaceTy<'tcx, M::Provenance> {
let misaligned =
if unaligned { None } else { self.is_ptr_misaligned(ptr, layout.align.abi) };
MPlaceTy { mplace: MemPlace { ptr, meta, misaligned }, layout }
}
pub fn ptr_to_mplace(
&self,
ptr: Pointer<Option<M::Provenance>>,
layout: TyAndLayout<'tcx>,
) -> MPlaceTy<'tcx, M::Provenance> {
assert!(layout.is_sized());
self.ptr_with_meta_to_mplace(ptr, MemPlaceMeta::None, layout, /*unaligned*/ false)
}
pub fn ptr_to_mplace_unaligned(
&self,
ptr: Pointer<Option<M::Provenance>>,
layout: TyAndLayout<'tcx>,
) -> MPlaceTy<'tcx, M::Provenance> {
assert!(layout.is_sized());
self.ptr_with_meta_to_mplace(ptr, MemPlaceMeta::None, layout, /*unaligned*/ true)
}
/// Take a value, which represents a (thin or wide) reference, and make it a place.
/// Alignment is just based on the type. This is the inverse of `mplace_to_ref()`.
///
/// Only call this if you are sure the place is "valid" (aligned and inbounds), or do not
/// want to ever use the place for memory access!
/// Generally prefer `deref_pointer`.
pub fn ref_to_mplace(
&self,
val: &ImmTy<'tcx, M::Provenance>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
let pointee_type =
val.layout.ty.builtin_deref(true).expect("`ref_to_mplace` called on non-ptr type");
let layout = self.layout_of(pointee_type)?;
let (ptr, meta) = val.to_scalar_and_meta();
// `ref_to_mplace` is called on raw pointers even if they don't actually get dereferenced;
// we hence can't call `size_and_align_of` since that asserts more validity than we want.
let ptr = ptr.to_pointer(self)?;
interp_ok(self.ptr_with_meta_to_mplace(ptr, meta, layout, /*unaligned*/ false))
}
/// Turn a mplace into a (thin or wide) mutable raw pointer, pointing to the same space.
/// `align` information is lost!
/// This is the inverse of `ref_to_mplace`.
pub fn mplace_to_ref(
&self,
mplace: &MPlaceTy<'tcx, M::Provenance>,
) -> InterpResult<'tcx, ImmTy<'tcx, M::Provenance>> {
let imm = mplace.mplace.to_ref(self);
let layout = self.layout_of(Ty::new_mut_ptr(self.tcx.tcx, mplace.layout.ty))?;
interp_ok(ImmTy::from_immediate(imm, layout))
}
/// Take an operand, representing a pointer, and dereference it to a place.
/// Corresponds to the `*` operator in Rust.
#[instrument(skip(self), level = "trace")]
pub fn deref_pointer(
&self,
src: &impl Projectable<'tcx, M::Provenance>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
if src.layout().ty.is_box() {
// Derefer should have removed all Box derefs.
// Some `Box` are not immediates (if they have a custom allocator)
// so the code below would fail.
bug!("dereferencing {}", src.layout().ty);
}
let val = self.read_immediate(src)?;
trace!("deref to {} on {:?}", val.layout.ty, *val);
let mplace = self.ref_to_mplace(&val)?;
interp_ok(mplace)
}
#[inline]
pub(super) fn get_place_alloc(
&self,
mplace: &MPlaceTy<'tcx, M::Provenance>,
) -> InterpResult<'tcx, Option<AllocRef<'_, 'tcx, M::Provenance, M::AllocExtra, M::Bytes>>>
{
let (size, _align) = self
.size_and_align_of_mplace(mplace)?
.unwrap_or((mplace.layout.size, mplace.layout.align.abi));
// We check alignment separately, and *after* checking everything else.
// If an access is both OOB and misaligned, we want to see the bounds error.
let a = self.get_ptr_alloc(mplace.ptr(), size)?;
self.check_misalign(mplace.mplace.misaligned, CheckAlignMsg::BasedOn)?;
interp_ok(a)
}
#[inline]
pub(super) fn get_place_alloc_mut(
&mut self,
mplace: &MPlaceTy<'tcx, M::Provenance>,
) -> InterpResult<'tcx, Option<AllocRefMut<'_, 'tcx, M::Provenance, M::AllocExtra, M::Bytes>>>
{
let (size, _align) = self
.size_and_align_of_mplace(mplace)?
.unwrap_or((mplace.layout.size, mplace.layout.align.abi));
// We check alignment separately, and raise that error *after* checking everything else.
// If an access is both OOB and misaligned, we want to see the bounds error.
// However we have to call `check_misalign` first to make the borrow checker happy.
let misalign_res = self.check_misalign(mplace.mplace.misaligned, CheckAlignMsg::BasedOn);
// An error from get_ptr_alloc_mut takes precedence.
let (a, ()) = self.get_ptr_alloc_mut(mplace.ptr(), size).and(misalign_res)?;
interp_ok(a)
}
/// Turn a local in the current frame into a place.
pub fn local_to_place(
&self,
local: mir::Local,
) -> InterpResult<'tcx, PlaceTy<'tcx, M::Provenance>> {
let frame = self.frame();
let layout = self.layout_of_local(frame, local, None)?;
let place = if layout.is_sized() {
// We can just always use the `Local` for sized values.
Place::Local { local, offset: None, locals_addr: frame.locals_addr() }
} else {
// Other parts of the system rely on `Place::Local` never being unsized.
match frame.locals[local].access()? {
Operand::Immediate(_) => bug!(),
Operand::Indirect(mplace) => Place::Ptr(*mplace),
}
};
interp_ok(PlaceTy { place, layout })
}
/// Computes a place. You should only use this if you intend to write into this
/// place; for reading, a more efficient alternative is `eval_place_to_op`.
#[instrument(skip(self), level = "trace")]
pub fn eval_place(
&self,
mir_place: mir::Place<'tcx>,
) -> InterpResult<'tcx, PlaceTy<'tcx, M::Provenance>> {
let mut place = self.local_to_place(mir_place.local)?;
// Using `try_fold` turned out to be bad for performance, hence the loop.
for elem in mir_place.projection.iter() {
place = self.project(&place, elem)?
}
trace!("{:?}", self.dump_place(&place));
// Sanity-check the type we ended up with.
if cfg!(debug_assertions) {
let normalized_place_ty = self
.instantiate_from_current_frame_and_normalize_erasing_regions(
mir_place.ty(&self.frame().body.local_decls, *self.tcx).ty,
)?;
if !mir_assign_valid_types(
*self.tcx,
self.typing_env,
self.layout_of(normalized_place_ty)?,
place.layout,
) {
span_bug!(
self.cur_span(),
"eval_place of a MIR place with type {} produced an interpreter place with type {}",
normalized_place_ty,
place.layout.ty,
)
}
}
interp_ok(place)
}
/// Given a place, returns either the underlying mplace or a reference to where the value of
/// this place is stored.
#[inline(always)]
fn as_mplace_or_mutable_local(
&mut self,
place: &PlaceTy<'tcx, M::Provenance>,
) -> InterpResult<
'tcx,
Either<
MPlaceTy<'tcx, M::Provenance>,
(&mut Immediate<M::Provenance>, TyAndLayout<'tcx>, mir::Local),
>,
> {
interp_ok(match place.to_place().as_mplace_or_local() {
Left(mplace) => Left(mplace),
Right((local, offset, locals_addr, layout)) => {
if offset.is_some() {
// This has been projected to a part of this local, or had the type changed.
// FIMXE: there are cases where we could still avoid allocating an mplace.
Left(place.force_mplace(self)?)
} else {
debug_assert_eq!(locals_addr, self.frame().locals_addr());
debug_assert_eq!(self.layout_of_local(self.frame(), local, None)?, layout);
match self.frame_mut().locals[local].access_mut()? {
Operand::Indirect(mplace) => {
// The local is in memory.
Left(MPlaceTy { mplace: *mplace, layout })
}
Operand::Immediate(local_val) => {
// The local still has the optimized representation.
Right((local_val, layout, local))
}
}
}
}
})
}
/// Write an immediate to a place
#[inline(always)]
#[instrument(skip(self), level = "trace")]
pub fn write_immediate(
&mut self,
src: Immediate<M::Provenance>,
dest: &impl Writeable<'tcx, M::Provenance>,
) -> InterpResult<'tcx> {
self.write_immediate_no_validate(src, dest)?;
if M::enforce_validity(self, dest.layout()) {
// Data got changed, better make sure it matches the type!
// Also needed to reset padding.
self.validate_operand(
&dest.to_place(),
M::enforce_validity_recursively(self, dest.layout()),
/*reset_provenance_and_padding*/ true,
)?;
}
interp_ok(())
}
/// Write a scalar to a place
#[inline(always)]
pub fn write_scalar(
&mut self,
val: impl Into<Scalar<M::Provenance>>,
dest: &impl Writeable<'tcx, M::Provenance>,
) -> InterpResult<'tcx> {
self.write_immediate(Immediate::Scalar(val.into()), dest)
}
/// Write a pointer to a place
#[inline(always)]
pub fn write_pointer(
&mut self,
ptr: impl Into<Pointer<Option<M::Provenance>>>,
dest: &impl Writeable<'tcx, M::Provenance>,
) -> InterpResult<'tcx> {
self.write_scalar(Scalar::from_maybe_pointer(ptr.into(), self), dest)
}
/// Write an immediate to a place.
/// If you use this you are responsible for validating that things got copied at the
/// right type.
pub(super) fn write_immediate_no_validate(
&mut self,
src: Immediate<M::Provenance>,
dest: &impl Writeable<'tcx, M::Provenance>,
) -> InterpResult<'tcx> {
assert!(dest.layout().is_sized(), "Cannot write unsized immediate data");
match self.as_mplace_or_mutable_local(&dest.to_place())? {
Right((local_val, local_layout, local)) => {
// Local can be updated in-place.
*local_val = src;
// Call the machine hook (the data race detector needs to know about this write).
if !self.validation_in_progress() {
M::after_local_write(self, local, /*storage_live*/ false)?;
}
// Double-check that the value we are storing and the local fit to each other.
// Things can ge wrong in quite weird ways when this is violated.
// Unfortunately this is too expensive to do in release builds.
if cfg!(debug_assertions) {
src.assert_matches_abi(
local_layout.backend_repr,
"invalid immediate for given destination place",
self,
);
}
}
Left(mplace) => {
self.write_immediate_to_mplace_no_validate(src, mplace.layout, mplace.mplace)?;
}
}
interp_ok(())
}
/// Write an immediate to memory.
/// If you use this you are responsible for validating that things got copied at the
/// right layout.
fn write_immediate_to_mplace_no_validate(
&mut self,
value: Immediate<M::Provenance>,
layout: TyAndLayout<'tcx>,
dest: MemPlace<M::Provenance>,
) -> InterpResult<'tcx> {
// We use the sizes from `value` below.
// Ensure that matches the type of the place it is written to.
value.assert_matches_abi(
layout.backend_repr,
"invalid immediate for given destination place",
self,
);
// Note that it is really important that the type here is the right one, and matches the
// type things are read at. In case `value` is a `ScalarPair`, we don't do any magic here
// to handle padding properly, which is only correct if we never look at this data with the
// wrong type.
let tcx = *self.tcx;
let Some(mut alloc) = self.get_place_alloc_mut(&MPlaceTy { mplace: dest, layout })? else {
// zero-sized access
return interp_ok(());
};
match value {
Immediate::Scalar(scalar) => {
alloc.write_scalar(alloc_range(Size::ZERO, scalar.size()), scalar)
}
Immediate::ScalarPair(a_val, b_val) => {
let BackendRepr::ScalarPair(a, b) = layout.backend_repr else {
span_bug!(
self.cur_span(),
"write_immediate_to_mplace: invalid ScalarPair layout: {:#?}",
layout
)
};
let b_offset = a.size(&tcx).align_to(b.align(&tcx).abi);
assert!(b_offset.bytes() > 0); // in `operand_field` we use the offset to tell apart the fields
// It is tempting to verify `b_offset` against `layout.fields.offset(1)`,
// but that does not work: We could be a newtype around a pair, then the
// fields do not match the `ScalarPair` components.
alloc.write_scalar(alloc_range(Size::ZERO, a_val.size()), a_val)?;
alloc.write_scalar(alloc_range(b_offset, b_val.size()), b_val)?;
// We don't have to reset padding here, `write_immediate` will anyway do a validation run.
interp_ok(())
}
Immediate::Uninit => alloc.write_uninit_full(),
}
}
pub fn write_uninit(
&mut self,
dest: &impl Writeable<'tcx, M::Provenance>,
) -> InterpResult<'tcx> {
match self.as_mplace_or_mutable_local(&dest.to_place())? {
Right((local_val, _local_layout, local)) => {
*local_val = Immediate::Uninit;
// Call the machine hook (the data race detector needs to know about this write).
if !self.validation_in_progress() {
M::after_local_write(self, local, /*storage_live*/ false)?;
}
}
Left(mplace) => {
let Some(mut alloc) = self.get_place_alloc_mut(&mplace)? else {
// Zero-sized access
return interp_ok(());
};
alloc.write_uninit_full()?;
}
}
interp_ok(())
}
/// Remove all provenance in the given place.
pub fn clear_provenance(
&mut self,
dest: &impl Writeable<'tcx, M::Provenance>,
) -> InterpResult<'tcx> {
match self.as_mplace_or_mutable_local(&dest.to_place())? {
Right((local_val, _local_layout, local)) => {
local_val.clear_provenance()?;
// Call the machine hook (the data race detector needs to know about this write).
if !self.validation_in_progress() {
M::after_local_write(self, local, /*storage_live*/ false)?;
}
}
Left(mplace) => {
let Some(mut alloc) = self.get_place_alloc_mut(&mplace)? else {
// Zero-sized access
return interp_ok(());
};
alloc.clear_provenance()?;
}
}
interp_ok(())
}
/// Copies the data from an operand to a place.
/// The layouts of the `src` and `dest` may disagree.
/// Does not perform validation of the destination.
/// The only known use case for this function is checking the return
/// value of a static during stack frame popping.
#[inline(always)]
pub(super) fn copy_op_no_dest_validation(
&mut self,
src: &impl Projectable<'tcx, M::Provenance>,
dest: &impl Writeable<'tcx, M::Provenance>,
) -> InterpResult<'tcx> {
self.copy_op_inner(
src, dest, /* allow_transmute */ true, /* validate_dest */ false,
)
}
/// Copies the data from an operand to a place.
/// The layouts of the `src` and `dest` may disagree.
#[inline(always)]
pub fn copy_op_allow_transmute(
&mut self,
src: &impl Projectable<'tcx, M::Provenance>,
dest: &impl Writeable<'tcx, M::Provenance>,
) -> InterpResult<'tcx> {
self.copy_op_inner(
src, dest, /* allow_transmute */ true, /* validate_dest */ true,
)
}
/// Copies the data from an operand to a place.
/// `src` and `dest` must have the same layout and the copied value will be validated.
#[inline(always)]
pub fn copy_op(
&mut self,
src: &impl Projectable<'tcx, M::Provenance>,
dest: &impl Writeable<'tcx, M::Provenance>,
) -> InterpResult<'tcx> {
self.copy_op_inner(
src, dest, /* allow_transmute */ false, /* validate_dest */ true,
)
}
/// Copies the data from an operand to a place.
/// `allow_transmute` indicates whether the layouts may disagree.
#[inline(always)]
#[instrument(skip(self), level = "trace")]
fn copy_op_inner(
&mut self,
src: &impl Projectable<'tcx, M::Provenance>,
dest: &impl Writeable<'tcx, M::Provenance>,
allow_transmute: bool,
validate_dest: bool,
) -> InterpResult<'tcx> {
// These are technically *two* typed copies: `src` is a not-yet-loaded value,
// so we're going a typed copy at `src` type from there to some intermediate storage.
// And then we're doing a second typed copy from that intermediate storage to `dest`.
// But as an optimization, we only make a single direct copy here.
// Do the actual copy.
self.copy_op_no_validate(src, dest, allow_transmute)?;
if validate_dest && M::enforce_validity(self, dest.layout()) {
let dest = dest.to_place();
// Given that there were two typed copies, we have to ensure this is valid at both types,
// and we have to ensure this loses provenance and padding according to both types.
// But if the types are identical, we only do one pass.
if allow_transmute && src.layout().ty != dest.layout().ty {
self.validate_operand(
&dest.transmute(src.layout(), self)?,
M::enforce_validity_recursively(self, src.layout()),
/*reset_provenance_and_padding*/ true,
)?;
}
self.validate_operand(
&dest,
M::enforce_validity_recursively(self, dest.layout()),
/*reset_provenance_and_padding*/ true,
)?;
}
interp_ok(())
}
/// Copies the data from an operand to a place.
/// `allow_transmute` indicates whether the layouts may disagree.
/// Also, if you use this you are responsible for validating that things get copied at the
/// right type.
#[instrument(skip(self), level = "trace")]
fn copy_op_no_validate(
&mut self,
src: &impl Projectable<'tcx, M::Provenance>,
dest: &impl Writeable<'tcx, M::Provenance>,
allow_transmute: bool,
) -> InterpResult<'tcx> {
// We do NOT compare the types for equality, because well-typed code can
// actually "transmute" `&mut T` to `&T` in an assignment without a cast.
let layout_compat =
mir_assign_valid_types(*self.tcx, self.typing_env, src.layout(), dest.layout());
if !allow_transmute && !layout_compat {
span_bug!(
self.cur_span(),
"type mismatch when copying!\nsrc: {},\ndest: {}",
src.layout().ty,
dest.layout().ty,
);
}
// Let us see if the layout is simple so we take a shortcut,
// avoid force_allocation.
let src = match self.read_immediate_raw(src)? {
Right(src_val) => {
assert!(!src.layout().is_unsized());
assert!(!dest.layout().is_unsized());
assert_eq!(src.layout().size, dest.layout().size);
// Yay, we got a value that we can write directly.
return if layout_compat {
self.write_immediate_no_validate(*src_val, dest)
} else {
// This is tricky. The problematic case is `ScalarPair`: the `src_val` was
// loaded using the offsets defined by `src.layout`. When we put this back into
// the destination, we have to use the same offsets! So (a) we make sure we
// write back to memory, and (b) we use `dest` *with the source layout*.
let dest_mem = dest.force_mplace(self)?;
self.write_immediate_to_mplace_no_validate(
*src_val,
src.layout(),
dest_mem.mplace,
)
};
}
Left(mplace) => mplace,
};
// Slow path, this does not fit into an immediate. Just memcpy.
trace!("copy_op: {:?} <- {:?}: {}", *dest, src, dest.layout().ty);
let dest = dest.force_mplace(self)?;
let Some((dest_size, _)) = self.size_and_align_of_mplace(&dest)? else {
span_bug!(self.cur_span(), "copy_op needs (dynamically) sized values")
};
if cfg!(debug_assertions) {
let src_size = self.size_and_align_of_mplace(&src)?.unwrap().0;
assert_eq!(src_size, dest_size, "Cannot copy differently-sized data");
} else {
// As a cheap approximation, we compare the fixed parts of the size.
assert_eq!(src.layout.size, dest.layout.size);
}
// Setting `nonoverlapping` here only has an effect when we don't hit the fast-path above,
// but that should at least match what LLVM does where `memcpy` is also only used when the
// type does not have Scalar/ScalarPair layout.
// (Or as the `Assign` docs put it, assignments "not producing primitives" must be
// non-overlapping.)
// We check alignment separately, and *after* checking everything else.
// If an access is both OOB and misaligned, we want to see the bounds error.
self.mem_copy(src.ptr(), dest.ptr(), dest_size, /*nonoverlapping*/ true)?;
self.check_misalign(src.mplace.misaligned, CheckAlignMsg::BasedOn)?;
self.check_misalign(dest.mplace.misaligned, CheckAlignMsg::BasedOn)?;
interp_ok(())
}
/// Ensures that a place is in memory, and returns where it is.
/// If the place currently refers to a local that doesn't yet have a matching allocation,
/// create such an allocation.
/// This is essentially `force_to_memplace`.
#[instrument(skip(self), level = "trace")]
pub fn force_allocation(
&mut self,
place: &PlaceTy<'tcx, M::Provenance>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
let mplace = match place.place {
Place::Local { local, offset, locals_addr } => {
debug_assert_eq!(locals_addr, self.frame().locals_addr());
let whole_local = match self.frame_mut().locals[local].access_mut()? {
&mut Operand::Immediate(local_val) => {
// We need to make an allocation.
// We need the layout of the local. We can NOT use the layout we got,
// that might e.g., be an inner field of a struct with `Scalar` layout,
// that has different alignment than the outer field.
let local_layout = self.layout_of_local(&self.frame(), local, None)?;
assert!(local_layout.is_sized(), "unsized locals cannot be immediate");
let mplace = self.allocate(local_layout, MemoryKind::Stack)?;
// Preserve old value. (As an optimization, we can skip this if it was uninit.)
if !matches!(local_val, Immediate::Uninit) {
// We don't have to validate as we can assume the local was already
// valid for its type. We must not use any part of `place` here, that
// could be a projection to a part of the local!
self.write_immediate_to_mplace_no_validate(
local_val,
local_layout,
mplace.mplace,
)?;
}
M::after_local_moved_to_memory(self, local, &mplace)?;
// Now we can call `access_mut` again, asserting it goes well, and actually
// overwrite things. This points to the entire allocation, not just the part
// the place refers to, i.e. we do this before we apply `offset`.
*self.frame_mut().locals[local].access_mut().unwrap() =
Operand::Indirect(mplace.mplace);
mplace.mplace
}
&mut Operand::Indirect(mplace) => mplace, // this already was an indirect local
};
if let Some(offset) = offset {
// This offset is always inbounds, no need to check it again.
whole_local.offset_with_meta_(
offset,
OffsetMode::Wrapping,
MemPlaceMeta::None,
self,
)?
} else {
// Preserve wide place metadata, do not call `offset`.
whole_local
}
}
Place::Ptr(mplace) => mplace,
};
// Return with the original layout and align, so that the caller can go on
interp_ok(MPlaceTy { mplace, layout: place.layout })
}
pub fn allocate_dyn(
&mut self,
layout: TyAndLayout<'tcx>,
kind: MemoryKind<M::MemoryKind>,
meta: MemPlaceMeta<M::Provenance>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
let Some((size, align)) = self.size_and_align_of(&meta, &layout)? else {
span_bug!(self.cur_span(), "cannot allocate space for `extern` type, size is not known")
};
let ptr = self.allocate_ptr(size, align, kind)?;
interp_ok(self.ptr_with_meta_to_mplace(ptr.into(), meta, layout, /*unaligned*/ false))
}
pub fn allocate(
&mut self,
layout: TyAndLayout<'tcx>,
kind: MemoryKind<M::MemoryKind>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
assert!(layout.is_sized());
self.allocate_dyn(layout, kind, MemPlaceMeta::None)
}
/// Returns a wide MPlace of type `str` to a new 1-aligned allocation.
/// Immutable strings are deduplicated and stored in global memory.
pub fn allocate_str(
&mut self,
str: &str,
kind: MemoryKind<M::MemoryKind>,
mutbl: Mutability,
) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
let tcx = self.tcx.tcx;
// Use cache for immutable strings.
let ptr = if mutbl.is_not() {
// Use dedup'd allocation function.
let salt = M::get_global_alloc_salt(self, None);
let id = tcx.allocate_bytes_dedup(str.as_bytes(), salt);
// Turn untagged "global" pointers (obtained via `tcx`) into the machine pointer to the allocation.
M::adjust_alloc_root_pointer(&self, Pointer::from(id), Some(kind))?
} else {
self.allocate_bytes_ptr(str.as_bytes(), Align::ONE, kind, mutbl)?
};
let meta = Scalar::from_target_usize(u64::try_from(str.len()).unwrap(), self);
let layout = self.layout_of(self.tcx.types.str_).unwrap();
interp_ok(self.ptr_with_meta_to_mplace(
ptr.into(),
MemPlaceMeta::Meta(meta),
layout,
/*unaligned*/ false,
))
}
pub fn raw_const_to_mplace(
&self,
raw: mir::ConstAlloc<'tcx>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
// This must be an allocation in `tcx`
let _ = self.tcx.global_alloc(raw.alloc_id);
let ptr = self.global_root_pointer(Pointer::from(raw.alloc_id))?;
let layout = self.layout_of(raw.ty)?;
interp_ok(self.ptr_to_mplace(ptr.into(), layout))
}
}
// Some nodes are used a lot. Make sure they don't unintentionally get bigger.
#[cfg(target_pointer_width = "64")]
mod size_asserts {
use rustc_data_structures::static_assert_size;
use super::*;
// tidy-alphabetical-start
static_assert_size!(MemPlace, 48);
static_assert_size!(MemPlaceMeta, 24);
static_assert_size!(MPlaceTy<'_>, 64);
static_assert_size!(Place, 48);
static_assert_size!(PlaceTy<'_>, 64);
// tidy-alphabetical-end
}