move validation to its own file

Author: RalfJung

src/librustc_mir/interpret/eval_context.rs

@@ -7,15 +7,15 @@ use rustc::hir::def::Def;
 use rustc::hir::map::definitions::DefPathData;
 use rustc::mir;
 use rustc::ty::layout::{
-    self, Size, Align, HasDataLayout, LayoutOf, TyLayout, Primitive
+    self, Size, Align, HasDataLayout, LayoutOf, TyLayout
 };
 use rustc::ty::subst::{Subst, Substs};
 use rustc::ty::{self, Ty, TyCtxt, TypeFoldable};
 use rustc::ty::query::TyCtxtAt;
 use rustc_data_structures::fx::{FxHashSet, FxHasher};
 use rustc_data_structures::indexed_vec::IndexVec;
 use rustc::mir::interpret::{
-    GlobalId, Scalar, FrameInfo, AllocType,
+    GlobalId, Scalar, FrameInfo,
     EvalResult, EvalErrorKind,
     ScalarMaybeUndef,
     truncate, sign_extend,
@@ -29,31 +29,6 @@ use super::{
     Memory, Machine
 };
 
-macro_rules! validation_failure{
-    ($what:expr, $where:expr, $details:expr) => {{
-        let where_ = if $where.is_empty() {
-            String::new()
-        } else {
-            format!(" at {}", $where)
-        };
-        err!(ValidationFailure(format!(
-            "encountered {}{}, but expected {}",
-            $what, where_, $details,
-        )))
-    }};
-    ($what:expr, $where:expr) => {{
-        let where_ = if $where.is_empty() {
-            String::new()
-        } else {
-            format!(" at {}", $where)
-        };
-        err!(ValidationFailure(format!(
-            "encountered {}{}",
-            $what, where_,
-        )))
-    }};
-}
-
 pub struct EvalContext<'a, 'mir, 'tcx: 'a + 'mir, M: Machine<'mir, 'tcx>> {
     /// Stores the `Machine` instance.
     pub machine: M,
@@ -670,243 +645,6 @@ impl<'a, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M
         self.tcx.const_eval(param_env.and(gid)).map_err(|err| EvalErrorKind::ReferencedConstant(err).into())
     }
 
-    fn validate_scalar(
-        &self,
-        value: ScalarMaybeUndef,
-        size: Size,
-        scalar: &layout::Scalar,
-        path: &str,
-        ty: Ty,
-    ) -> EvalResult<'tcx> {
-        trace!("validate scalar: {:#?}, {:#?}, {:#?}, {}", value, size, scalar, ty);
-        let (lo, hi) = scalar.valid_range.clone().into_inner();
-
-        let value = match value {
-            ScalarMaybeUndef::Scalar(scalar) => scalar,
-            ScalarMaybeUndef::Undef => return validation_failure!("undefined bytes", path),
-        };
-
-        let bits = match value {
-            Scalar::Bits { bits, size: value_size } => {
-                assert_eq!(value_size as u64, size.bytes());
-                bits
-            },
-            Scalar::Ptr(_) => {
-                let ptr_size = self.memory.pointer_size();
-                let ptr_max = u128::max_value() >> (128 - ptr_size.bits());
-                return if lo > hi {
-                    if lo - hi == 1 {
-                        // no gap, all values are ok
-                        Ok(())
-                    } else if hi < ptr_max || lo > 1 {
-                        let max = u128::max_value() >> (128 - size.bits());
-                        validation_failure!(
-                            "pointer",
-                            path,
-                            format!("something in the range {:?} or {:?}", 0..=lo, hi..=max)
-                        )
-                    } else {
-                        Ok(())
-                    }
-                } else if hi < ptr_max || lo > 1 {
-                    validation_failure!(
-                        "pointer",
-                        path,
-                        format!("something in the range {:?}", scalar.valid_range)
-                    )
-                } else {
-                    Ok(())
-                };
-            },
-        };
-
-        // char gets a special treatment, because its number space is not contiguous so `TyLayout`
-        // has no special checks for chars
-        match ty.sty {
-            ty::TyChar => {
-                debug_assert_eq!(size.bytes(), 4);
-                if ::std::char::from_u32(bits as u32).is_none() {
-                    return err!(InvalidChar(bits));
-                }
-            }
-            _ => {},
-        }
-
-        use std::ops::RangeInclusive;
-        let in_range = |bound: RangeInclusive<u128>| bound.contains(&bits);
-        if lo > hi {
-            if in_range(0..=hi) || in_range(lo..=u128::max_value()) {
-                Ok(())
-            } else {
-                validation_failure!(
-                    bits,
-                    path,
-                    format!("something in the range {:?} or {:?}", ..=hi, lo..)
-                )
-            }
-        } else {
-            if in_range(scalar.valid_range.clone()) {
-                Ok(())
-            } else {
-                validation_failure!(
-                    bits,
-                    path,
-                    format!("something in the range {:?}", scalar.valid_range)
-                )
-            }
-        }
-    }
-
-    /// This function checks the memory where `ptr` points to.
-    /// It will error if the bits at the destination do not match the ones described by the layout.
-    pub fn validate_mplace(
-        &self,
-        dest: MPlaceTy<'tcx>,
-        path: String,
-        seen: &mut FxHashSet<(MPlaceTy<'tcx>)>,
-        todo: &mut Vec<(MPlaceTy<'tcx>, String)>,
-    ) -> EvalResult<'tcx> {
-        self.memory.dump_alloc(dest.to_ptr()?.alloc_id);
-        trace!("validate_mplace: {:?}, {:#?}", *dest, dest.layout);
-
-        // Find the right variant
-        let (variant, dest) = match dest.layout.variants {
-            layout::Variants::NicheFilling { niche: ref tag, .. } |
-            layout::Variants::Tagged { ref tag, .. } => {
-                let size = tag.value.size(self);
-                // we first read the tag value as scalar, to be able to validate it
-                let tag_mplace = self.mplace_field(dest, 0)?;
-                let tag_value = self.read_scalar(tag_mplace.into())?;
-                let path = format!("{}.TAG", path);
-                self.validate_scalar(
-                    tag_value, size, tag, &path, tag_mplace.layout.ty
-                )?;
-                // then we read it again to get the index, to continue
-                let variant = self.read_discriminant_as_variant_index(dest.into())?;
-                let dest = self.mplace_downcast(dest, variant)?;
-                trace!("variant layout: {:#?}", dest.layout);
-                (variant, dest)
-            },
-            layout::Variants::Single { index } => {
-                (index, dest)
-            }
-        };
-
-        // Validate all fields
-        match dest.layout.fields {
-            // primitives are unions with zero fields
-            layout::FieldPlacement::Union(0) => {
-                match dest.layout.abi {
-                    // nothing to do, whatever the pointer points to, it is never going to be read
-                    layout::Abi::Uninhabited => validation_failure!("a value of an uninhabited type", path),
-                    // check that the scalar is a valid pointer or that its bit range matches the
-                    // expectation.
-                    layout::Abi::Scalar(ref scalar_layout) => {
-                        let size = scalar_layout.value.size(self);
-                        let value = self.read_value(dest.into())?;
-                        let scalar = value.to_scalar_or_undef();
-                        self.validate_scalar(scalar, size, scalar_layout, &path, dest.layout.ty)?;
-                        if scalar_layout.value == Primitive::Pointer {
-                            // ignore integer pointers, we can't reason about the final hardware
-                            if let Scalar::Ptr(ptr) = scalar.not_undef()? {
-                                let alloc_kind = self.tcx.alloc_map.lock().get(ptr.alloc_id);
-                                if let Some(AllocType::Static(did)) = alloc_kind {
-                                    // statics from other crates are already checked
-                                    // extern statics should not be validated as they have no body
-                                    if !did.is_local() || self.tcx.is_foreign_item(did) {
-                                        return Ok(());
-                                    }
-                                }
-                                if value.layout.ty.builtin_deref(false).is_some() {
-                                    trace!("Recursing below ptr {:#?}", value);
-                                    let ptr_place = self.ref_to_mplace(value)?;
-                                    // we have not encountered this pointer+layout combination before
-                                    if seen.insert(ptr_place) {
-                                        todo.push((ptr_place, format!("(*{})", path)))
-                                    }
-                                }
-                            }
-                        }
-                        Ok(())
-                    },
-                    _ => bug!("bad abi for FieldPlacement::Union(0): {:#?}", dest.layout.abi),
-                }
-            }
-            layout::FieldPlacement::Union(_) => {
-                // We can't check unions, their bits are allowed to be anything.
-                // The fields don't need to correspond to any bit pattern of the union's fields.
-                // See https://github.com/rust-lang/rust/issues/32836#issuecomment-406875389
-                Ok(())
-            },
-            layout::FieldPlacement::Array { count, .. } => {
-                for i in 0..count {
-                    let mut path = path.clone();
-                    self.dump_field_name(&mut path, dest.layout.ty, i as usize, variant).unwrap();
-                    let field = self.mplace_field(dest, i)?;
-                    self.validate_mplace(field, path, seen, todo)?;
-                }
-                Ok(())
-            },
-            layout::FieldPlacement::Arbitrary { ref offsets, .. } => {
-                // fat pointers need special treatment
-                match dest.layout.ty.builtin_deref(false).map(|tam| &tam.ty.sty) {
-                    | Some(ty::TyStr)
-                    | Some(ty::TySlice(_)) => {
-                        // check the length (for nicer error messages)
-                        let len_mplace = self.mplace_field(dest, 1)?;
-                        let len = self.read_scalar(len_mplace.into())?;
-                        let len = match len.to_bits(len_mplace.layout.size) {
-                            Err(_) => return validation_failure!("length is not a valid integer", path),
-                            Ok(len) => len as u64,
-                        };
-                        // get the fat ptr, and recursively check it
-                        let ptr = self.ref_to_mplace(self.read_value(dest.into())?)?;
-                        assert_eq!(ptr.extra, PlaceExtra::Length(len));
-                        let unpacked_ptr = self.unpack_unsized_mplace(ptr)?;
-                        if seen.insert(unpacked_ptr) {
-                            let mut path = path.clone();
-                            self.dump_field_name(&mut path, dest.layout.ty, 0, 0).unwrap();
-                            todo.push((unpacked_ptr, path))
-                        }
-                    },
-                    Some(ty::TyDynamic(..)) => {
-                        // check the vtable (for nicer error messages)
-                        let vtable = self.read_scalar(self.mplace_field(dest, 1)?.into())?;
-                        let vtable = match vtable.to_ptr() {
-                            Err(_) => return validation_failure!("vtable address is not a pointer", path),
-                            Ok(vtable) => vtable,
-                        };
-                        // get the fat ptr, and recursively check it
-                        let ptr = self.ref_to_mplace(self.read_value(dest.into())?)?;
-                        assert_eq!(ptr.extra, PlaceExtra::Vtable(vtable));
-                        let unpacked_ptr = self.unpack_unsized_mplace(ptr)?;
-                        if seen.insert(unpacked_ptr) {
-                            let mut path = path.clone();
-                            self.dump_field_name(&mut path, dest.layout.ty, 0, 0).unwrap();
-                            todo.push((unpacked_ptr, path))
-                        }
-                        // FIXME: More checks for the vtable... making sure it is exactly
-                        // the one one would expect for this type.
-                    },
-                    Some(ty) =>
-                        bug!("Unexpected fat pointer target type {:?}", ty),
-                    None => {
-                        // Not a pointer, perform regular aggregate handling below
-                        for i in 0..offsets.len() {
-                            let mut path = path.clone();
-                            self.dump_field_name(&mut path, dest.layout.ty, i, variant).unwrap();
-                            let field = self.mplace_field(dest, i as u64)?;
-                            self.validate_mplace(field, path, seen, todo)?;
-                        }
-                        // FIXME: For a TyStr, check that this is valid UTF-8.
-                    },
-                }
-
-                Ok(())
-            }
-        }
-    }
-
     #[inline(always)]
     pub fn frame(&self) -> &Frame<'mir, 'tcx> {
         self.stack.last().expect("no call frames exist")
@@ -1041,72 +779,5 @@ impl<'a, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M
     pub fn truncate(&self, value: u128, ty: TyLayout<'_>) -> u128 {
         truncate(value, ty.size)
     }
-
-    fn dump_field_name(&self, s: &mut String, ty: Ty<'tcx>, i: usize, variant: usize) -> ::std::fmt::Result {
-        match ty.sty {
-            ty::TyBool |
-            ty::TyChar |
-            ty::TyInt(_) |
-            ty::TyUint(_) |
-            ty::TyFloat(_) |
-            ty::TyFnPtr(_) |
-            ty::TyNever |
-            ty::TyFnDef(..) |
-            ty::TyGeneratorWitness(..) |
-            ty::TyForeign(..) |
-            ty::TyDynamic(..) => {
-                bug!("field_name({:?}): not applicable", ty)
-            }
-
-            // Potentially-fat pointers.
-            ty::TyRef(_, pointee, _) |
-            ty::TyRawPtr(ty::TypeAndMut { ty: pointee, .. }) => {
-                assert!(i < 2);
-
-                // Reuse the fat *T type as its own thin pointer data field.
-                // This provides information about e.g. DST struct pointees
-                // (which may have no non-DST form), and will work as long
-                // as the `Abi` or `FieldPlacement` is checked by users.
-                if i == 0 {
-                    return write!(s, ".data_ptr");
-                }
-
-                match self.tcx.struct_tail(pointee).sty {
-                    ty::TySlice(_) |
-                    ty::TyStr => write!(s, ".len"),
-                    ty::TyDynamic(..) => write!(s, ".vtable_ptr"),
-                    _ => bug!("field_name({:?}): not applicable", ty)
-                }
-            }
-
-            // Arrays and slices.
-            ty::TyArray(_, _) |
-            ty::TySlice(_) |
-            ty::TyStr => write!(s, "[{}]", i),
-
-            // generators and closures.
-            ty::TyClosure(def_id, _) | ty::TyGenerator(def_id, _, _) => {
-                let node_id = self.tcx.hir.as_local_node_id(def_id).unwrap();
-                let freevar = self.tcx.with_freevars(node_id, |fv| fv[i]);
-                write!(s, ".upvar({})", self.tcx.hir.name(freevar.var_id()))
-            }
-
-            ty::TyTuple(_) => write!(s, ".{}", i),
-
-            // enums
-            ty::TyAdt(def, ..) if def.is_enum() => {
-                let variant = &def.variants[variant];
-                write!(s, ".{}::{}", variant.name, variant.fields[i].ident)
-            }
-
-            // other ADTs.
-            ty::TyAdt(def, _) => write!(s, ".{}", def.non_enum_variant().fields[i].ident),
-
-            ty::TyProjection(_) | ty::TyAnon(..) | ty::TyParam(_) |
-            ty::TyInfer(_) | ty::TyError => {
-                bug!("dump_field_name: unexpected type `{}`", ty)
-            }
-        }
-    }
 }
 

src/librustc_mir/interpret/mod.rs

@@ -11,6 +11,7 @@ mod step;
 mod terminator;
 mod traits;
 mod const_eval;
+mod validity;
 
 pub use self::eval_context::{
     EvalContext, Frame, StackPopCleanup, LocalValue,