1 //! This module contains everything needed to instantiate an interpreter.
2 //! This separation exists to ensure that no fancy miri features like
3 //! interpreting common C functions leak into CTFE.
5 use std::borrow::{Borrow, Cow};
8 use rustc::hir::def_id::DefId;
10 use rustc::ty::{self, Ty, TyCtxt};
14 AllocId, Allocation, AllocationExtra, AssertMessage, Frame, ImmTy, InterpCx, InterpResult,
15 Memory, MemoryKind, OpTy, Operand, PlaceTy, Pointer, Scalar,
18 /// Data returned by Machine::stack_pop,
19 /// to provide further control over the popping of the stack frame
20 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
21 pub enum StackPopInfo {
22 /// Indicates that no special handling should be
23 /// done - we'll either return normally or unwind
24 /// based on the terminator for the function
28 /// Indicates that we should stop unwinding,
29 /// as we've reached a catch frame
33 /// Whether this kind of memory is allowed to leak
34 pub trait MayLeak: Copy {
35 fn may_leak(self) -> bool;
38 /// The functionality needed by memory to manage its allocations
39 pub trait AllocMap<K: Hash + Eq, V> {
40 /// Tests if the map contains the given key.
41 /// Deliberately takes `&mut` because that is sufficient, and some implementations
42 /// can be more efficient then (using `RefCell::get_mut`).
43 fn contains_key<Q: ?Sized + Hash + Eq>(&mut self, k: &Q) -> bool
47 /// Inserts a new entry into the map.
48 fn insert(&mut self, k: K, v: V) -> Option<V>;
50 /// Removes an entry from the map.
51 fn remove<Q: ?Sized + Hash + Eq>(&mut self, k: &Q) -> Option<V>
55 /// Returns data based the keys and values in the map.
56 fn filter_map_collect<T>(&self, f: impl FnMut(&K, &V) -> Option<T>) -> Vec<T>;
58 /// Returns a reference to entry `k`. If no such entry exists, call
59 /// `vacant` and either forward its error, or add its result to the map
60 /// and return a reference to *that*.
61 fn get_or<E>(&self, k: K, vacant: impl FnOnce() -> Result<V, E>) -> Result<&V, E>;
63 /// Returns a mutable reference to entry `k`. If no such entry exists, call
64 /// `vacant` and either forward its error, or add its result to the map
65 /// and return a reference to *that*.
66 fn get_mut_or<E>(&mut self, k: K, vacant: impl FnOnce() -> Result<V, E>) -> Result<&mut V, E>;
69 fn get(&self, k: K) -> Option<&V> {
70 self.get_or(k, || Err(())).ok()
74 fn get_mut(&mut self, k: K) -> Option<&mut V> {
75 self.get_mut_or(k, || Err(())).ok()
79 /// Methods of this trait signifies a point where CTFE evaluation would fail
80 /// and some use case dependent behaviour can instead be applied.
81 pub trait Machine<'mir, 'tcx>: Sized {
82 /// Additional memory kinds a machine wishes to distinguish from the builtin ones
83 type MemoryKinds: ::std::fmt::Debug + MayLeak + Eq + 'static;
85 /// Tag tracked alongside every pointer. This is used to implement "Stacked Borrows"
86 /// <https://www.ralfj.de/blog/2018/08/07/stacked-borrows.html>.
87 /// The `default()` is used for pointers to consts, statics, vtables and functions.
88 type PointerTag: ::std::fmt::Debug + Copy + Eq + Hash + 'static;
90 /// Machines can define extra (non-instance) things that represent values of function pointers.
91 /// For example, Miri uses this to return a function pointer from `dlsym`
92 /// that can later be called to execute the right thing.
93 type ExtraFnVal: ::std::fmt::Debug + Copy;
95 /// Extra data stored in every call frame.
98 /// Extra data stored in memory. A reference to this is available when `AllocExtra`
99 /// gets initialized, so you can e.g., have an `Rc` here if there is global state you
100 /// need access to in the `AllocExtra` hooks.
103 /// Extra data stored in every allocation.
104 type AllocExtra: AllocationExtra<Self::PointerTag> + 'static;
106 /// Memory's allocation map
107 type MemoryMap: AllocMap<
109 (MemoryKind<Self::MemoryKinds>, Allocation<Self::PointerTag, Self::AllocExtra>),
113 /// The memory kind to use for copied statics -- or None if statics should not be mutated
114 /// and thus any such attempt will cause a `ModifiedStatic` error to be raised.
115 /// Statics are copied under two circumstances: When they are mutated, and when
116 /// `tag_allocation` or `find_foreign_static` (see below) returns an owned allocation
117 /// that is added to the memory so that the work is not done twice.
118 const STATIC_KIND: Option<Self::MemoryKinds>;
120 /// Whether memory accesses should be alignment-checked.
121 const CHECK_ALIGN: bool;
123 /// Whether to enforce the validity invariant
124 fn enforce_validity(ecx: &InterpCx<'mir, 'tcx, Self>) -> bool;
126 /// Called before a basic block terminator is executed.
127 /// You can use this to detect endlessly running programs.
128 fn before_terminator(ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx>;
130 /// Entry point to all function calls.
132 /// Returns either the mir to use for the call, or `None` if execution should
133 /// just proceed (which usually means this hook did all the work that the
134 /// called function should usually have done). In the latter case, it is
135 /// this hook's responsibility to advance the instruction pointer!
136 /// (This is to support functions like `__rust_maybe_catch_panic` that neither find a MIR
137 /// nor just jump to `ret`, but instead push their own stack frame.)
138 /// Passing `dest`and `ret` in the same `Option` proved very annoying when only one of them
140 fn find_mir_or_eval_fn(
141 ecx: &mut InterpCx<'mir, 'tcx, Self>,
142 instance: ty::Instance<'tcx>,
143 args: &[OpTy<'tcx, Self::PointerTag>],
144 ret: Option<(PlaceTy<'tcx, Self::PointerTag>, mir::BasicBlock)>,
145 unwind: Option<mir::BasicBlock>,
146 ) -> InterpResult<'tcx, Option<&'mir mir::Body<'tcx>>>;
148 /// Execute `fn_val`. It is the hook's responsibility to advance the instruction
149 /// pointer as appropriate.
151 ecx: &mut InterpCx<'mir, 'tcx, Self>,
152 fn_val: Self::ExtraFnVal,
153 args: &[OpTy<'tcx, Self::PointerTag>],
154 ret: Option<(PlaceTy<'tcx, Self::PointerTag>, mir::BasicBlock)>,
155 unwind: Option<mir::BasicBlock>,
156 ) -> InterpResult<'tcx>;
158 /// Directly process an intrinsic without pushing a stack frame. It is the hook's
159 /// responsibility to advance the instruction pointer as appropriate.
161 ecx: &mut InterpCx<'mir, 'tcx, Self>,
163 instance: ty::Instance<'tcx>,
164 args: &[OpTy<'tcx, Self::PointerTag>],
165 ret: Option<(PlaceTy<'tcx, Self::PointerTag>, mir::BasicBlock)>,
166 unwind: Option<mir::BasicBlock>,
167 ) -> InterpResult<'tcx>;
169 /// Called to evaluate `Assert` MIR terminators that trigger a panic.
171 ecx: &mut InterpCx<'mir, 'tcx, Self>,
173 msg: &AssertMessage<'tcx>,
174 unwind: Option<mir::BasicBlock>,
175 ) -> InterpResult<'tcx>;
177 /// Called for read access to a foreign static item.
179 /// This will only be called once per static and machine; the result is cached in
180 /// the machine memory. (This relies on `AllocMap::get_or` being able to add the
181 /// owned allocation to the map even when the map is shared.)
183 /// This allocation will then be fed to `tag_allocation` to initialize the "extra" state.
184 fn find_foreign_static(
187 ) -> InterpResult<'tcx, Cow<'tcx, Allocation>>;
189 /// Called for all binary operations where the LHS has pointer type.
191 /// Returns a (value, overflowed) pair if the operation succeeded
193 ecx: &InterpCx<'mir, 'tcx, Self>,
195 left: ImmTy<'tcx, Self::PointerTag>,
196 right: ImmTy<'tcx, Self::PointerTag>,
197 ) -> InterpResult<'tcx, (Scalar<Self::PointerTag>, bool, Ty<'tcx>)>;
199 /// Heap allocations via the `box` keyword.
201 ecx: &mut InterpCx<'mir, 'tcx, Self>,
202 dest: PlaceTy<'tcx, Self::PointerTag>,
203 ) -> InterpResult<'tcx>;
205 /// Called to read the specified `local` from the `frame`.
207 _ecx: &InterpCx<'mir, 'tcx, Self>,
208 frame: &Frame<'mir, 'tcx, Self::PointerTag, Self::FrameExtra>,
210 ) -> InterpResult<'tcx, Operand<Self::PointerTag>> {
211 frame.locals[local].access()
214 /// Called before a `StaticKind::Static` value is accessed.
215 fn before_access_static(_allocation: &Allocation) -> InterpResult<'tcx> {
219 /// Called to initialize the "extra" state of an allocation and make the pointers
220 /// it contains (in relocations) tagged. The way we construct allocations is
221 /// to always first construct it without extra and then add the extra.
222 /// This keeps uniform code paths for handling both allocations created by CTFE
223 /// for statics, and allocations ceated by Miri during evaluation.
225 /// `kind` is the kind of the allocation being tagged; it can be `None` when
226 /// it's a static and `STATIC_KIND` is `None`.
228 /// This should avoid copying if no work has to be done! If this returns an owned
229 /// allocation (because a copy had to be done to add tags or metadata), machine memory will
230 /// cache the result. (This relies on `AllocMap::get_or` being able to add the
231 /// owned allocation to the map even when the map is shared.)
233 /// Also return the "base" tag to use for this allocation: the one that is used for direct
234 /// accesses to this allocation. If `kind == STATIC_KIND`, this tag must be consistent
235 /// with `tag_static_base_pointer`.
236 fn init_allocation_extra<'b>(
237 memory_extra: &Self::MemoryExtra,
239 alloc: Cow<'b, Allocation>,
240 kind: Option<MemoryKind<Self::MemoryKinds>>,
241 ) -> (Cow<'b, Allocation<Self::PointerTag, Self::AllocExtra>>, Self::PointerTag);
243 /// Return the "base" tag for the given *static* allocation: the one that is used for direct
244 /// accesses to this static/const/fn allocation. If `id` is not a static allocation,
245 /// this will return an unusable tag (i.e., accesses will be UB)!
246 fn tag_static_base_pointer(memory_extra: &Self::MemoryExtra, id: AllocId) -> Self::PointerTag;
248 /// Executes a retagging operation
251 _ecx: &mut InterpCx<'mir, 'tcx, Self>,
252 _kind: mir::RetagKind,
253 _place: PlaceTy<'tcx, Self::PointerTag>,
254 ) -> InterpResult<'tcx> {
258 /// Called immediately before a new stack frame got pushed
259 fn stack_push(ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx, Self::FrameExtra>;
261 /// Called immediately after a stack frame gets popped
263 _ecx: &mut InterpCx<'mir, 'tcx, Self>,
264 _extra: Self::FrameExtra,
266 ) -> InterpResult<'tcx, StackPopInfo> {
267 // By default, we do not support unwinding from panics
268 Ok(StackPopInfo::Normal)
272 _mem: &Memory<'mir, 'tcx, Self>,
274 ) -> InterpResult<'tcx, Pointer<Self::PointerTag>> {
276 err_unsup!(InvalidNullPointerUsage)
278 err_unsup!(ReadBytesAsPointer)
284 _mem: &Memory<'mir, 'tcx, Self>,
285 _ptr: Pointer<Self::PointerTag>,
286 ) -> InterpResult<'tcx, u64>;