233 lines
9.8 KiB
Rust
233 lines
9.8 KiB
Rust
use std::mem;
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use rustc::ty::{self, layout::{self, Size}};
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use rustc::hir::def_id::{DefId, CRATE_DEF_INDEX};
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use crate::*;
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impl<'mir, 'tcx> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
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pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
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/// Gets an instance for a path.
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fn resolve_path(&self, path: &[&str]) -> InterpResult<'tcx, ty::Instance<'tcx>> {
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let this = self.eval_context_ref();
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this.tcx
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.crates()
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.iter()
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.find(|&&krate| this.tcx.original_crate_name(krate).as_str() == path[0])
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.and_then(|krate| {
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let krate = DefId {
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krate: *krate,
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index: CRATE_DEF_INDEX,
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};
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let mut items = this.tcx.item_children(krate);
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let mut path_it = path.iter().skip(1).peekable();
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while let Some(segment) = path_it.next() {
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for item in mem::replace(&mut items, Default::default()).iter() {
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if item.ident.name.as_str() == *segment {
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if path_it.peek().is_none() {
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return Some(ty::Instance::mono(this.tcx.tcx, item.res.def_id()));
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}
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items = this.tcx.item_children(item.res.def_id());
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break;
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}
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}
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}
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None
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})
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.ok_or_else(|| {
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let path = path.iter().map(|&s| s.to_owned()).collect();
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InterpError::PathNotFound(path).into()
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})
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}
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/// Write a 0 of the appropriate size to `dest`.
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fn write_null(&mut self, dest: PlaceTy<'tcx, Tag>) -> InterpResult<'tcx> {
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self.eval_context_mut().write_scalar(Scalar::from_int(0, dest.layout.size), dest)
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}
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/// Test if this immediate equals 0.
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fn is_null(&self, val: Scalar<Tag>) -> InterpResult<'tcx, bool> {
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let this = self.eval_context_ref();
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let null = Scalar::from_int(0, this.memory().pointer_size());
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this.ptr_eq(val, null)
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}
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/// Turn a Scalar into an Option<NonNullScalar>
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fn test_null(&self, val: Scalar<Tag>) -> InterpResult<'tcx, Option<Scalar<Tag>>> {
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let this = self.eval_context_ref();
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Ok(if this.is_null(val)? {
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None
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} else {
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Some(val)
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})
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}
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/// Visits the memory covered by `place`, sensitive to freezing: the 3rd parameter
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/// will be true if this is frozen, false if this is in an `UnsafeCell`.
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fn visit_freeze_sensitive(
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&self,
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place: MPlaceTy<'tcx, Tag>,
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size: Size,
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mut action: impl FnMut(Pointer<Tag>, Size, bool) -> InterpResult<'tcx>,
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) -> InterpResult<'tcx> {
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let this = self.eval_context_ref();
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trace!("visit_frozen(place={:?}, size={:?})", *place, size);
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debug_assert_eq!(size,
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this.size_and_align_of_mplace(place)?
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.map(|(size, _)| size)
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.unwrap_or_else(|| place.layout.size)
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);
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assert!(size.bytes() > 0);
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// Store how far we proceeded into the place so far. Everything to the left of
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// this offset has already been handled, in the sense that the frozen parts
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// have had `action` called on them.
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let mut end_ptr = place.ptr;
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// Called when we detected an `UnsafeCell` at the given offset and size.
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// Calls `action` and advances `end_ptr`.
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let mut unsafe_cell_action = |unsafe_cell_ptr: Scalar<Tag>, unsafe_cell_size: Size| {
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if unsafe_cell_size != Size::ZERO {
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debug_assert_eq!(unsafe_cell_ptr.to_ptr().unwrap().alloc_id,
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end_ptr.to_ptr().unwrap().alloc_id);
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debug_assert_eq!(unsafe_cell_ptr.to_ptr().unwrap().tag,
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end_ptr.to_ptr().unwrap().tag);
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}
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// We assume that we are given the fields in increasing offset order,
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// and nothing else changes.
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let unsafe_cell_offset = unsafe_cell_ptr.get_ptr_offset(this);
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let end_offset = end_ptr.get_ptr_offset(this);
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assert!(unsafe_cell_offset >= end_offset);
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let frozen_size = unsafe_cell_offset - end_offset;
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// Everything between the end_ptr and this `UnsafeCell` is frozen.
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if frozen_size != Size::ZERO {
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action(end_ptr.to_ptr()?, frozen_size, /*frozen*/true)?;
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}
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// This `UnsafeCell` is NOT frozen.
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if unsafe_cell_size != Size::ZERO {
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action(unsafe_cell_ptr.to_ptr()?, unsafe_cell_size, /*frozen*/false)?;
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}
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// Update end end_ptr.
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end_ptr = unsafe_cell_ptr.ptr_wrapping_offset(unsafe_cell_size, this);
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// Done
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Ok(())
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};
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// Run a visitor
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{
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let mut visitor = UnsafeCellVisitor {
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ecx: this,
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unsafe_cell_action: |place| {
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trace!("unsafe_cell_action on {:?}", place.ptr);
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// We need a size to go on.
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let unsafe_cell_size = this.size_and_align_of_mplace(place)?
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.map(|(size, _)| size)
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// for extern types, just cover what we can
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.unwrap_or_else(|| place.layout.size);
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// Now handle this `UnsafeCell`, unless it is empty.
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if unsafe_cell_size != Size::ZERO {
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unsafe_cell_action(place.ptr, unsafe_cell_size)
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} else {
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Ok(())
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}
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},
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};
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visitor.visit_value(place)?;
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}
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// The part between the end_ptr and the end of the place is also frozen.
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// So pretend there is a 0-sized `UnsafeCell` at the end.
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unsafe_cell_action(place.ptr.ptr_wrapping_offset(size, this), Size::ZERO)?;
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// Done!
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return Ok(());
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/// Visiting the memory covered by a `MemPlace`, being aware of
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/// whether we are inside an `UnsafeCell` or not.
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struct UnsafeCellVisitor<'ecx, 'mir, 'tcx, F>
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where F: FnMut(MPlaceTy<'tcx, Tag>) -> InterpResult<'tcx>
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{
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ecx: &'ecx MiriEvalContext<'mir, 'tcx>,
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unsafe_cell_action: F,
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}
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impl<'ecx, 'mir, 'tcx, F>
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ValueVisitor<'mir, 'tcx, Evaluator<'tcx>>
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for
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UnsafeCellVisitor<'ecx, 'mir, 'tcx, F>
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where
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F: FnMut(MPlaceTy<'tcx, Tag>) -> InterpResult<'tcx>
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{
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type V = MPlaceTy<'tcx, Tag>;
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#[inline(always)]
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fn ecx(&self) -> &MiriEvalContext<'mir, 'tcx> {
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&self.ecx
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}
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// Hook to detect `UnsafeCell`.
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fn visit_value(&mut self, v: MPlaceTy<'tcx, Tag>) -> InterpResult<'tcx>
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{
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trace!("UnsafeCellVisitor: {:?} {:?}", *v, v.layout.ty);
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let is_unsafe_cell = match v.layout.ty.sty {
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ty::Adt(adt, _) => Some(adt.did) == self.ecx.tcx.lang_items().unsafe_cell_type(),
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_ => false,
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};
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if is_unsafe_cell {
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// We do not have to recurse further, this is an `UnsafeCell`.
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(self.unsafe_cell_action)(v)
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} else if self.ecx.type_is_freeze(v.layout.ty) {
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// This is `Freeze`, there cannot be an `UnsafeCell`
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Ok(())
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} else {
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// Proceed further
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self.walk_value(v)
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}
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}
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// Make sure we visit aggregrates in increasing offset order.
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fn visit_aggregate(
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&mut self,
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place: MPlaceTy<'tcx, Tag>,
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fields: impl Iterator<Item=InterpResult<'tcx, MPlaceTy<'tcx, Tag>>>,
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) -> InterpResult<'tcx> {
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match place.layout.fields {
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layout::FieldPlacement::Array { .. } => {
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// For the array layout, we know the iterator will yield sorted elements so
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// we can avoid the allocation.
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self.walk_aggregate(place, fields)
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}
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layout::FieldPlacement::Arbitrary { .. } => {
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// Gather the subplaces and sort them before visiting.
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let mut places = fields.collect::<InterpResult<'tcx, Vec<MPlaceTy<'tcx, Tag>>>>()?;
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places.sort_by_key(|place| place.ptr.get_ptr_offset(self.ecx()));
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self.walk_aggregate(place, places.into_iter().map(Ok))
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}
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layout::FieldPlacement::Union { .. } => {
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// Uh, what?
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bug!("a union is not an aggregate we should ever visit")
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}
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}
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}
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// We have to do *something* for unions.
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fn visit_union(&mut self, v: MPlaceTy<'tcx, Tag>) -> InterpResult<'tcx>
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{
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// With unions, we fall back to whatever the type says, to hopefully be consistent
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// with LLVM IR.
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// FIXME: are we consistent, and is this really the behavior we want?
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let frozen = self.ecx.type_is_freeze(v.layout.ty);
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if frozen {
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Ok(())
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} else {
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(self.unsafe_cell_action)(v)
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}
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}
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// We should never get to a primitive, but always short-circuit somewhere above.
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fn visit_primitive(&mut self, _v: MPlaceTy<'tcx, Tag>) -> InterpResult<'tcx>
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{
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bug!("we should always short-circuit before coming to a primitive")
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}
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}
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}
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}
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