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basic dyn* support for Miri

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This commit is contained in:
Ralf Jung 2023-02-06 16:00:54 +01:00
parent dc89a803d6
commit b2f58146b9
16 changed files with 325 additions and 84 deletions
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11
compiler/rustc_const_eval/src/interpret/cast.rs
View file

@ -312,6 +312,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
}
}
/// `src` is a *pointer to* a `source_ty`, and in `dest` we should store a pointer to th same
/// data at type `cast_ty`.
fn unsize_into_ptr(
&mut self,
src: &OpTy<'tcx, M::Provenance>,
@ -335,7 +337,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
);
self.write_immediate(val, dest)
}
(ty::Dynamic(data_a, ..), ty::Dynamic(data_b, ..)) => {
(ty::Dynamic(data_a, _, ty::Dyn), ty::Dynamic(data_b, _, ty::Dyn)) => {
let val = self.read_immediate(src)?;
if data_a.principal() == data_b.principal() {
// A NOP cast that doesn't actually change anything, should be allowed even with mismatching vtables.
@ -359,7 +361,12 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
}
_ => {
span_bug!(self.cur_span(), "invalid unsizing {:?} -> {:?}", src.layout.ty, cast_ty)
span_bug!(
self.cur_span(),
"invalid pointer unsizing {:?} -> {:?}",
src.layout.ty,
cast_ty
)
}
}
}

2
compiler/rustc_const_eval/src/interpret/eval_context.rs
View file

@ -632,7 +632,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
}
Ok(Some((size, align)))
}
ty::Dynamic(..) => {
ty::Dynamic(_, _, ty::Dyn) => {
let vtable = metadata.unwrap_meta().to_pointer(self)?;
// Read size and align from vtable (already checks size).
Ok(Some(self.get_vtable_size_and_align(vtable)?))

2
compiler/rustc_const_eval/src/interpret/intern.rs
View file

@ -242,7 +242,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: CompileTimeMachine<'mir, 'tcx, const_eval::Memory
let mplace = self.ecx.ref_to_mplace(&value)?;
assert_eq!(mplace.layout.ty, referenced_ty);
// Handle trait object vtables.
if let ty::Dynamic(..) =
if let ty::Dynamic(_, _, ty::Dyn) =
tcx.struct_tail_erasing_lifetimes(referenced_ty, self.ecx.param_env).kind()
{
let ptr = mplace.meta.unwrap_meta().to_pointer(&tcx)?;

20
compiler/rustc_const_eval/src/interpret/operand.rs
View file

@ -255,7 +255,22 @@ impl<'tcx, Prov: Provenance> OpTy<'tcx, Prov> {
}
}
pub fn offset_with_meta(
/// Replace the layout of this operand. There's basically no sanity check that this makes sense,
/// you better know what you are doing! If this is an immediate, applying the wrong layout can
/// not just lead to invalid data, it can actually *shift the data around* since the offsets of
/// a ScalarPair are entirely determined by the layout, not the data.
pub fn transmute(&self, layout: TyAndLayout<'tcx>) -> Self {
assert_eq!(
self.layout.size, layout.size,
"transmuting with a size change, that doesn't seem right"
);
OpTy { layout, ..*self }
}
/// Offset the operand in memory (if possible) and change its metadata.
///
/// This can go wrong very easily if you give the wrong layout for the new place!
pub(super) fn offset_with_meta(
&self,
offset: Size,
meta: MemPlaceMeta<Prov>,
@ -276,6 +291,9 @@ impl<'tcx, Prov: Provenance> OpTy<'tcx, Prov> {
}
}
/// Offset the operand in memory (if possible).
///
/// This can go wrong very easily if you give the wrong layout for the new place!
pub fn offset(
&self,
offset: Size,

67
compiler/rustc_const_eval/src/interpret/place.rs
View file

@ -26,6 +26,7 @@ pub enum MemPlaceMeta<Prov: Provenance = AllocId> {
}
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,
@ -147,12 +148,16 @@ impl<Prov: Provenance> MemPlace<Prov> {
}
#[inline]
pub fn offset_with_meta<'tcx>(
pub(super) fn offset_with_meta<'tcx>(
self,
offset: Size,
meta: MemPlaceMeta<Prov>,
cx: &impl HasDataLayout,
) -> InterpResult<'tcx, Self> {
debug_assert!(
!meta.has_meta() || self.meta.has_meta(),
"cannot use `offset_with_meta` to add metadata to a place"
);
Ok(MemPlace { ptr: self.ptr.offset(offset, cx)?, meta })
}
}
@ -182,8 +187,11 @@ impl<'tcx, Prov: Provenance> MPlaceTy<'tcx, Prov> {
MPlaceTy { mplace: MemPlace { ptr, meta: MemPlaceMeta::None }, layout, align }
}
/// Offset the place in memory and change its metadata.
///
/// This can go wrong very easily if you give the wrong layout for the new place!
#[inline]
pub fn offset_with_meta(
pub(crate) fn offset_with_meta(
&self,
offset: Size,
meta: MemPlaceMeta<Prov>,
@ -197,6 +205,9 @@ impl<'tcx, Prov: Provenance> MPlaceTy<'tcx, Prov> {
})
}
/// Offset the place in memory.
///
/// This can go wrong very easily if you give the wrong layout for the new place!
pub fn offset(
&self,
offset: Size,
@ -241,14 +252,6 @@ impl<'tcx, Prov: Provenance> MPlaceTy<'tcx, Prov> {
}
}
}
#[inline]
pub(super) fn vtable(&self) -> Scalar<Prov> {
match self.layout.ty.kind() {
ty::Dynamic(..) => self.mplace.meta.unwrap_meta(),
_ => bug!("vtable not supported on type {:?}", self.layout.ty),
}
}
}
// These are defined here because they produce a place.
@ -266,7 +269,12 @@ impl<'tcx, Prov: Provenance> OpTy<'tcx, Prov> {
#[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()
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
)
})
}
}
@ -283,7 +291,12 @@ impl<'tcx, Prov: Provenance> PlaceTy<'tcx, Prov> {
#[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()
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
)
})
}
}
@ -807,11 +820,16 @@ where
}
/// Turn a place with a `dyn Trait` type into a place with the actual dynamic type.
/// Aso returns the vtable.
pub(super) fn unpack_dyn_trait(
&self,
mplace: &MPlaceTy<'tcx, M::Provenance>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
let vtable = mplace.vtable().to_pointer(self)?; // also sanity checks the type
) -> InterpResult<'tcx, (MPlaceTy<'tcx, M::Provenance>, Pointer<Option<M::Provenance>>)> {
assert!(
matches!(mplace.layout.ty.kind(), ty::Dynamic(_, _, ty::Dyn)),
"`unpack_dyn_trait` only makes sense on `dyn*` types"
);
let vtable = mplace.meta.unwrap_meta().to_pointer(self)?;
let (ty, _) = self.get_ptr_vtable(vtable)?;
let layout = self.layout_of(ty)?;
@ -820,7 +838,26 @@ where
layout,
align: layout.align.abi,
};
Ok(mplace)
Ok((mplace, vtable))
}
/// Turn an operand with a `dyn* Trait` type into an operand with the actual dynamic type.
/// Aso returns the vtable.
pub(super) fn unpack_dyn_star(
&self,
op: &OpTy<'tcx, M::Provenance>,
) -> InterpResult<'tcx, (OpTy<'tcx, M::Provenance>, Pointer<Option<M::Provenance>>)> {
assert!(
matches!(op.layout.ty.kind(), ty::Dynamic(_, _, ty::DynStar)),
"`unpack_dyn_star` only makes sense on `dyn*` types"
);
let data = self.operand_field(&op, 0)?;
let vtable = self.operand_field(&op, 1)?;
let vtable = self.read_pointer(&vtable)?;
let (ty, _) = self.get_ptr_vtable(vtable)?;
let layout = self.layout_of(ty)?;
let data = data.transmute(layout);
Ok((data, vtable))
}
}

127
compiler/rustc_const_eval/src/interpret/terminator.rs
View file

@ -538,10 +538,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
// pointer or `dyn Trait` type, but it could be wrapped in newtypes. So recursively
// unwrap those newtypes until we are there.
let mut receiver = args[0].clone();
let receiver_place = loop {
let receiver = loop {
match receiver.layout.ty.kind() {
ty::Ref(..) | ty::RawPtr(..) => break self.deref_operand(&receiver)?,
ty::Dynamic(..) => break receiver.assert_mem_place(), // no immediate unsized values
ty::Dynamic(..) | ty::Ref(..) | ty::RawPtr(..) => break receiver,
_ => {
// Not there yet, search for the only non-ZST field.
let mut non_zst_field = None;
@ -567,39 +566,83 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
}
}
};
// Obtain the underlying trait we are working on.
let receiver_tail = self
.tcx
.struct_tail_erasing_lifetimes(receiver_place.layout.ty, self.param_env);
let ty::Dynamic(data, ..) = receiver_tail.kind() else {
span_bug!(self.cur_span(), "dynamic call on non-`dyn` type {}", receiver_tail)
};
// Get the required information from the vtable.
let vptr = receiver_place.meta.unwrap_meta().to_pointer(self)?;
let (dyn_ty, dyn_trait) = self.get_ptr_vtable(vptr)?;
if dyn_trait != data.principal() {
throw_ub_format!(
"`dyn` call on a pointer whose vtable does not match its type"
);
}
// break self.deref_operand(&receiver)?.into();
// Obtain the underlying trait we are working on, and the adjusted receiver argument.
let recv_ty = receiver.layout.ty;
let (vptr, dyn_ty, adjusted_receiver) = match recv_ty.kind() {
ty::Ref(..) | ty::RawPtr(..)
if matches!(
recv_ty.builtin_deref(true).unwrap().ty.kind(),
ty::Dynamic(_, _, ty::DynStar)
) =>
{
let receiver = self.deref_operand(&receiver)?;
let ty::Dynamic(data, ..) = receiver.layout.ty.kind() else { bug!() };
let (recv, vptr) = self.unpack_dyn_star(&receiver.into())?;
let (dyn_ty, dyn_trait) = self.get_ptr_vtable(vptr)?;
if dyn_trait != data.principal() {
throw_ub_format!(
"`dyn*` call on a pointer whose vtable does not match its type"
);
}
let recv = recv.assert_mem_place(); // we passed an MPlaceTy to `unpack_dyn_star` so we definitely still have one
(vptr, dyn_ty, recv.ptr)
}
ty::Dynamic(_, _, ty::DynStar) => {
// Not clear how to handle this, so far we assume the receiver is always a pointer.
span_bug!(
self.cur_span(),
"by-value calls on a `dyn*`... are those a thing?"
);
}
_ => {
let receiver_place = match recv_ty.kind() {
ty::Ref(..) | ty::RawPtr(..) => self.deref_operand(&receiver)?,
ty::Dynamic(_, _, ty::Dyn) => receiver.assert_mem_place(), // unsized (`dyn`) cannot be immediate
_ => bug!(),
};
// Doesn't have to be a `dyn Trait`, but the unsized tail must be `dyn Trait`.
// (For that reason we also cannot use `unpack_dyn_trait`.)
let receiver_tail = self.tcx.struct_tail_erasing_lifetimes(
receiver_place.layout.ty,
self.param_env,
);
let ty::Dynamic(data, _, ty::Dyn) = receiver_tail.kind() else {
span_bug!(self.cur_span(), "dynamic call on non-`dyn` type {}", receiver_tail)
};
assert!(receiver_place.layout.is_unsized());
// Get the required information from the vtable.
let vptr = receiver_place.meta.unwrap_meta().to_pointer(self)?;
let (dyn_ty, dyn_trait) = self.get_ptr_vtable(vptr)?;
if dyn_trait != data.principal() {
throw_ub_format!(
"`dyn` call on a pointer whose vtable does not match its type"
);
}
// It might be surprising that we use a pointer as the receiver even if this
// is a by-val case; this works because by-val passing of an unsized `dyn
// Trait` to a function is actually desugared to a pointer.
(vptr, dyn_ty, receiver_place.ptr)
}
};
// Now determine the actual method to call. We can do that in two different ways and
// compare them to ensure everything fits.
let Some(ty::VtblEntry::Method(fn_inst)) = self.get_vtable_entries(vptr)?.get(idx).copied() else {
throw_ub_format!("`dyn` call trying to call something that is not a method")
};
trace!("Virtual call dispatches to {fn_inst:#?}");
if cfg!(debug_assertions) {
let tcx = *self.tcx;
let trait_def_id = tcx.trait_of_item(def_id).unwrap();
let virtual_trait_ref =
ty::TraitRef::from_method(tcx, trait_def_id, instance.substs);
assert_eq!(
receiver_tail,
virtual_trait_ref.self_ty(),
"mismatch in underlying dyn trait computation within Miri and MIR building",
);
let existential_trait_ref =
ty::ExistentialTraitRef::erase_self_ty(tcx, virtual_trait_ref);
let concrete_trait_ref = existential_trait_ref.with_self_ty(tcx, dyn_ty);
@ -614,17 +657,12 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
assert_eq!(fn_inst, concrete_method);
}
// `*mut receiver_place.layout.ty` is almost the layout that we
// want for args[0]: We have to project to field 0 because we want
// a thin pointer.
assert!(receiver_place.layout.is_unsized());
let receiver_ptr_ty = self.tcx.mk_mut_ptr(receiver_place.layout.ty);
let this_receiver_ptr = self.layout_of(receiver_ptr_ty)?.field(self, 0);
// Adjust receiver argument.
args[0] = OpTy::from(ImmTy::from_immediate(
Scalar::from_maybe_pointer(receiver_place.ptr, self).into(),
this_receiver_ptr,
));
// Adjust receiver argument. Layout can be any (thin) ptr.
args[0] = ImmTy::from_immediate(
Scalar::from_maybe_pointer(adjusted_receiver, self).into(),
self.layout_of(self.tcx.mk_mut_ptr(dyn_ty))?,
)
.into();
trace!("Patched receiver operand to {:#?}", args[0]);
// recurse with concrete function
self.eval_fn_call(
@ -653,15 +691,24 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
// implementation fail -- a problem shared by rustc.
let place = self.force_allocation(place)?;
let (instance, place) = match place.layout.ty.kind() {
ty::Dynamic(..) => {
let place = match place.layout.ty.kind() {
ty::Dynamic(_, _, ty::Dyn) => {
// Dropping a trait object. Need to find actual drop fn.
let place = self.unpack_dyn_trait(&place)?;
let instance = ty::Instance::resolve_drop_in_place(*self.tcx, place.layout.ty);
(instance, place)
self.unpack_dyn_trait(&place)?.0
}
ty::Dynamic(_, _, ty::DynStar) => {
// Dropping a `dyn*`. Need to find actual drop fn.
self.unpack_dyn_star(&place.into())?.0.assert_mem_place()
}
_ => {
debug_assert_eq!(
instance,
ty::Instance::resolve_drop_in_place(*self.tcx, place.layout.ty)
);
place
}
_ => (instance, place),
};
let instance = ty::Instance::resolve_drop_in_place(*self.tcx, place.layout.ty);
let fn_abi = self.fn_abi_of_instance(instance, ty::List::empty())?;
let arg = ImmTy::from_immediate(

23
compiler/rustc_const_eval/src/interpret/validity.rs
View file

@ -23,18 +23,18 @@ use std::hash::Hash;
// for the validation errors
use super::UndefinedBehaviorInfo::*;
use super::{
CheckInAllocMsg, GlobalAlloc, ImmTy, Immediate, InterpCx, InterpResult, MPlaceTy, Machine,
MemPlaceMeta, OpTy, Scalar, ValueVisitor,
AllocId, CheckInAllocMsg, GlobalAlloc, ImmTy, Immediate, InterpCx, InterpResult, MPlaceTy,
Machine, MemPlaceMeta, OpTy, Pointer, Scalar, ValueVisitor,
};
macro_rules! throw_validation_failure {
($where:expr, { $( $what_fmt:expr ),+ } $( expected { $( $expected_fmt:expr ),+ } )?) => {{
($where:expr, { $( $what_fmt:tt )* } $( expected { $( $expected_fmt:tt )* } )?) => {{
let mut msg = String::new();
msg.push_str("encountered ");
write!(&mut msg, $($what_fmt),+).unwrap();
write!(&mut msg, $($what_fmt)*).unwrap();
$(
msg.push_str(", but expected ");
write!(&mut msg, $($expected_fmt),+).unwrap();
write!(&mut msg, $($expected_fmt)*).unwrap();
)?
let path = rustc_middle::ty::print::with_no_trimmed_paths!({
let where_ = &$where;
@ -82,7 +82,7 @@ macro_rules! throw_validation_failure {
///
macro_rules! try_validation {
($e:expr, $where:expr,
$( $( $p:pat_param )|+ => { $( $what_fmt:expr ),+ } $( expected { $( $expected_fmt:expr ),+ } )? ),+ $(,)?
$( $( $p:pat_param )|+ => { $( $what_fmt:tt )* } $( expected { $( $expected_fmt:tt )* } )? ),+ $(,)?
) => {{
match $e {
Ok(x) => x,
@ -93,7 +93,7 @@ macro_rules! try_validation {
InterpError::UndefinedBehavior($($p)|+) =>
throw_validation_failure!(
$where,
{ $( $what_fmt ),+ } $( expected { $( $expected_fmt ),+ } )?
{ $( $what_fmt )* } $( expected { $( $expected_fmt )* } )?
)
),+,
#[allow(unreachable_patterns)]
@ -335,7 +335,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
) -> InterpResult<'tcx> {
let tail = self.ecx.tcx.struct_tail_erasing_lifetimes(pointee.ty, self.ecx.param_env);
match tail.kind() {
ty::Dynamic(..) => {
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!(
@ -399,12 +399,15 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
{
"an unaligned {kind} (required {} byte alignment but found {})",
required.bytes(),
has.bytes()
has.bytes(),
},
DanglingIntPointer(0, _) =>
{ "a null {kind}" },
DanglingIntPointer(i, _) =>
{ "a dangling {kind} (address {i:#x} is unallocated)" },
{
"a dangling {kind} ({pointer} has no provenance)",
pointer = Pointer::<Option<AllocId>>::from_addr_invalid(*i),
},
PointerOutOfBounds { .. } =>
{ "a dangling {kind} (going beyond the bounds of its allocation)" },
// This cannot happen during const-eval (because interning already detects

16
compiler/rustc_const_eval/src/interpret/visitor.rs
View file

@ -284,7 +284,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueMut<'mir, 'tcx, M>
&self,
ecx: &InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, OpTy<'tcx, M::Provenance>> {
// We `force_allocation` here so that `from_op` below can work.
// No need for `force_allocation` since we are just going to read from this.
ecx.place_to_op(self)
}
@ -421,15 +421,25 @@ macro_rules! make_value_visitor {
// Special treatment for special types, where the (static) layout is not sufficient.
match *ty.kind() {
// If it is a trait object, switch to the real type that was used to create it.
ty::Dynamic(..) => {
ty::Dynamic(_, _, ty::Dyn) => {
// Dyn types. This is unsized, and the actual dynamic type of the data is given by the
// vtable stored in the place metadata.
// unsized values are never immediate, so we can assert_mem_place
let op = v.to_op_for_read(self.ecx())?;
let dest = op.assert_mem_place();
let inner_mplace = self.ecx().unpack_dyn_trait(&dest)?;
let inner_mplace = self.ecx().unpack_dyn_trait(&dest)?.0;
trace!("walk_value: dyn object layout: {:#?}", inner_mplace.layout);
// recurse with the inner type
return self.visit_field(&v, 0, &$value_trait::from_op(&inner_mplace.into()));
},
ty::Dynamic(_, _, ty::DynStar) => {
// DynStar types. Very different from a dyn type (but strangely part of the
// same variant in `TyKind`): These are pairs where the 2nd component is the
// vtable, and the first component is the data (which must be ptr-sized).
let op = v.to_op_for_proj(self.ecx())?;
let data = self.ecx().unpack_dyn_star(&op)?.0;
return self.visit_field(&v, 0, &$value_trait::from_op(&data));
}
// Slices do not need special handling here: they have `Array` field
// placement with length 0, so we enter the `Array` case below which
// indirectly uses the metadata to determine the actual length.