1 // Copyright 2018 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! This module contains everything needed to instantiate an interpreter.
12 //! This separation exists to ensure that no fancy miri features like
13 //! interpreting common C functions leak into CTFE.
15 use std::borrow::{Borrow, Cow};
18 use rustc::hir::{self, def_id::DefId};
20 use rustc::ty::{self, layout::TyLayout, query::TyCtxtAt};
23 Allocation, AllocId, EvalResult, Scalar, AllocationExtra,
24 EvalContext, PlaceTy, MPlaceTy, OpTy, Pointer, MemoryKind,
27 /// Whether this kind of memory is allowed to leak
28 pub trait MayLeak: Copy {
29 fn may_leak(self) -> bool;
32 /// The functionality needed by memory to manage its allocations
33 pub trait AllocMap<K: Hash + Eq, V> {
34 /// Test if the map contains the given key.
35 /// Deliberately takes `&mut` because that is sufficient, and some implementations
36 /// can be more efficient then (using `RefCell::get_mut`).
37 fn contains_key<Q: ?Sized + Hash + Eq>(&mut self, k: &Q) -> bool
40 /// Insert new entry into the map.
41 fn insert(&mut self, k: K, v: V) -> Option<V>;
43 /// Remove entry from the map.
44 fn remove<Q: ?Sized + Hash + Eq>(&mut self, k: &Q) -> Option<V>
47 /// Return data based the keys and values in the map.
48 fn filter_map_collect<T>(&self, f: impl FnMut(&K, &V) -> Option<T>) -> Vec<T>;
50 /// Return a reference to entry `k`. If no such entry exists, call
51 /// `vacant` and either forward its error, or add its result to the map
52 /// and return a reference to *that*.
56 vacant: impl FnOnce() -> Result<V, E>
59 /// Return a mutable reference to entry `k`. If no such entry exists, call
60 /// `vacant` and either forward its error, or add its result to the map
61 /// and return a reference to *that*.
65 vacant: impl FnOnce() -> Result<V, E>
66 ) -> Result<&mut V, E>;
69 /// Methods of this trait signifies a point where CTFE evaluation would fail
70 /// and some use case dependent behaviour can instead be applied.
71 pub trait Machine<'a, 'mir, 'tcx>: Sized {
72 /// Additional memory kinds a machine wishes to distinguish from the builtin ones
73 type MemoryKinds: ::std::fmt::Debug + MayLeak + Eq + 'static;
75 /// Tag tracked alongside every pointer. This is used to implement "Stacked Borrows"
76 /// <https://www.ralfj.de/blog/2018/08/07/stacked-borrows.html>.
77 /// The `default()` is used for pointers to consts, statics, vtables and functions.
78 type PointerTag: ::std::fmt::Debug + Default + Copy + Eq + Hash + 'static;
80 /// Extra data stored in every allocation.
81 type AllocExtra: AllocationExtra<Self::PointerTag>;
83 /// Memory's allocation map
87 (MemoryKind<Self::MemoryKinds>, Allocation<Self::PointerTag, Self::AllocExtra>)
92 /// The memory kind to use for copied statics -- or None if those are not supported.
93 /// Statics are copied under two circumstances: When they are mutated, and when
94 /// `static_with_default_tag` or `find_foreign_static` (see below) returns an owned allocation
95 /// that is added to the memory so that the work is not done twice.
96 const STATIC_KIND: Option<Self::MemoryKinds>;
98 /// Whether to enforce the validity invariant
99 fn enforce_validity(ecx: &EvalContext<'a, 'mir, 'tcx, Self>) -> bool;
101 /// Called before a basic block terminator is executed.
102 /// You can use this to detect endlessly running programs.
103 fn before_terminator(ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>) -> EvalResult<'tcx>;
105 /// Entry point to all function calls.
107 /// Returns either the mir to use for the call, or `None` if execution should
108 /// just proceed (which usually means this hook did all the work that the
109 /// called function should usually have done). In the latter case, it is
110 /// this hook's responsibility to call `goto_block(ret)` to advance the instruction pointer!
111 /// (This is to support functions like `__rust_maybe_catch_panic` that neither find a MIR
112 /// nor just jump to `ret`, but instead push their own stack frame.)
113 /// Passing `dest`and `ret` in the same `Option` proved very annoying when only one of them
116 ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
117 instance: ty::Instance<'tcx>,
118 args: &[OpTy<'tcx, Self::PointerTag>],
119 dest: Option<PlaceTy<'tcx, Self::PointerTag>>,
120 ret: Option<mir::BasicBlock>,
121 ) -> EvalResult<'tcx, Option<&'mir mir::Mir<'tcx>>>;
123 /// Directly process an intrinsic without pushing a stack frame.
124 /// If this returns successfully, the engine will take care of jumping to the next block.
126 ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
127 instance: ty::Instance<'tcx>,
128 args: &[OpTy<'tcx, Self::PointerTag>],
129 dest: PlaceTy<'tcx, Self::PointerTag>,
130 ) -> EvalResult<'tcx>;
132 /// Called for read access to a foreign static item.
134 /// This will only be called once per static and machine; the result is cached in
135 /// the machine memory. (This relies on `AllocMap::get_or` being able to add the
136 /// owned allocation to the map even when the map is shared.)
137 fn find_foreign_static(
138 tcx: TyCtxtAt<'a, 'tcx, 'tcx>,
140 ) -> EvalResult<'tcx, Cow<'tcx, Allocation<Self::PointerTag, Self::AllocExtra>>>;
142 /// Called to turn an allocation obtained from the `tcx` into one that has
143 /// the right type for this machine.
145 /// This should avoid copying if no work has to be done! If this returns an owned
146 /// allocation (because a copy had to be done to add tags or metadata), machine memory will
147 /// cache the result. (This relies on `AllocMap::get_or` being able to add the
148 /// owned allocation to the map even when the map is shared.)
149 fn adjust_static_allocation(
150 alloc: &'_ Allocation
151 ) -> Cow<'_, Allocation<Self::PointerTag, Self::AllocExtra>>;
153 /// Called for all binary operations on integer(-like) types when one operand is a pointer
154 /// value, and for the `Offset` operation that is inherently about pointers.
156 /// Returns a (value, overflowed) pair if the operation succeeded
158 ecx: &EvalContext<'a, 'mir, 'tcx, Self>,
160 left: Scalar<Self::PointerTag>,
161 left_layout: TyLayout<'tcx>,
162 right: Scalar<Self::PointerTag>,
163 right_layout: TyLayout<'tcx>,
164 ) -> EvalResult<'tcx, (Scalar<Self::PointerTag>, bool)>;
166 /// Heap allocations via the `box` keyword.
168 ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
169 dest: PlaceTy<'tcx, Self::PointerTag>,
170 ) -> EvalResult<'tcx>;
172 /// Add the tag for a newly allocated pointer.
173 fn tag_new_allocation(
174 ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
176 kind: MemoryKind<Self::MemoryKinds>,
177 ) -> EvalResult<'tcx, Pointer<Self::PointerTag>>;
179 /// Executed when evaluating the `*` operator: Following a reference.
180 /// This has the chance to adjust the tag. It should not change anything else!
181 /// `mutability` can be `None` in case a raw ptr is being dereferenced.
184 _ecx: &EvalContext<'a, 'mir, 'tcx, Self>,
185 place: MPlaceTy<'tcx, Self::PointerTag>,
186 _mutability: Option<hir::Mutability>,
187 ) -> EvalResult<'tcx, Scalar<Self::PointerTag>> {
191 /// Execute a retagging operation
194 _ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
196 _place: PlaceTy<'tcx, Self::PointerTag>,
197 ) -> EvalResult<'tcx> {
201 /// Execute an escape-to-raw operation
204 _ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
205 _ptr: OpTy<'tcx, Self::PointerTag>,
206 ) -> EvalResult<'tcx> {