--- /dev/null
+//! This module contains everything needed to instantiate an interpreter.
+//! This separation exists to ensure that no fancy miri features like
+//! interpreting common C functions leak into CTFE.
+
+use std::borrow::{Borrow, Cow};
+use std::fmt::Debug;
+use std::hash::Hash;
+
+use rustc_middle::mir;
+use rustc_middle::ty::{self, Ty};
+use rustc_span::def_id::DefId;
+use rustc_target::abi::Size;
+use rustc_target::spec::abi::Abi;
+
+use super::{
+ AllocId, AllocRange, Allocation, Frame, ImmTy, InterpCx, InterpResult, LocalValue, MemPlace,
+ Memory, MemoryKind, OpTy, Operand, PlaceTy, Pointer, Provenance, Scalar, StackPopUnwind,
+};
+
+/// Data returned by Machine::stack_pop,
+/// to provide further control over the popping of the stack frame
+#[derive(Eq, PartialEq, Debug, Copy, Clone)]
+pub enum StackPopJump {
+ /// Indicates that no special handling should be
+ /// done - we'll either return normally or unwind
+ /// based on the terminator for the function
+ /// we're leaving.
+ Normal,
+
+ /// Indicates that we should *not* jump to the return/unwind address, as the callback already
+ /// took care of everything.
+ NoJump,
+}
+
+/// Whether this kind of memory is allowed to leak
+pub trait MayLeak: Copy {
+ fn may_leak(self) -> bool;
+}
+
+/// The functionality needed by memory to manage its allocations
+pub trait AllocMap<K: Hash + Eq, V> {
+ /// Tests if the map contains the given key.
+ /// Deliberately takes `&mut` because that is sufficient, and some implementations
+ /// can be more efficient then (using `RefCell::get_mut`).
+ fn contains_key<Q: ?Sized + Hash + Eq>(&mut self, k: &Q) -> bool
+ where
+ K: Borrow<Q>;
+
+ /// Inserts a new entry into the map.
+ fn insert(&mut self, k: K, v: V) -> Option<V>;
+
+ /// Removes an entry from the map.
+ fn remove<Q: ?Sized + Hash + Eq>(&mut self, k: &Q) -> Option<V>
+ where
+ K: Borrow<Q>;
+
+ /// Returns data based on the keys and values in the map.
+ fn filter_map_collect<T>(&self, f: impl FnMut(&K, &V) -> Option<T>) -> Vec<T>;
+
+ /// Returns a reference to entry `k`. If no such entry exists, call
+ /// `vacant` and either forward its error, or add its result to the map
+ /// and return a reference to *that*.
+ fn get_or<E>(&self, k: K, vacant: impl FnOnce() -> Result<V, E>) -> Result<&V, E>;
+
+ /// Returns a mutable reference to entry `k`. If no such entry exists, call
+ /// `vacant` and either forward its error, or add its result to the map
+ /// and return a reference to *that*.
+ fn get_mut_or<E>(&mut self, k: K, vacant: impl FnOnce() -> Result<V, E>) -> Result<&mut V, E>;
+
+ /// Read-only lookup.
+ fn get(&self, k: K) -> Option<&V> {
+ self.get_or(k, || Err(())).ok()
+ }
+
+ /// Mutable lookup.
+ fn get_mut(&mut self, k: K) -> Option<&mut V> {
+ self.get_mut_or(k, || Err(())).ok()
+ }
+}
+
+/// Methods of this trait signifies a point where CTFE evaluation would fail
+/// and some use case dependent behaviour can instead be applied.
+pub trait Machine<'mir, 'tcx>: Sized {
+ /// Additional memory kinds a machine wishes to distinguish from the builtin ones
+ type MemoryKind: Debug + std::fmt::Display + MayLeak + Eq + 'static;
+
+ /// Pointers are "tagged" with provenance information; typically the `AllocId` they belong to.
+ type PointerTag: Provenance + Eq + Hash + 'static;
+
+ /// Machines can define extra (non-instance) things that represent values of function pointers.
+ /// For example, Miri uses this to return a function pointer from `dlsym`
+ /// that can later be called to execute the right thing.
+ type ExtraFnVal: Debug + Copy;
+
+ /// Extra data stored in every call frame.
+ type FrameExtra;
+
+ /// Extra data stored in memory. A reference to this is available when `AllocExtra`
+ /// gets initialized, so you can e.g., have an `Rc` here if there is global state you
+ /// need access to in the `AllocExtra` hooks.
+ type MemoryExtra;
+
+ /// Extra data stored in every allocation.
+ type AllocExtra: Debug + Clone + 'static;
+
+ /// Memory's allocation map
+ type MemoryMap: AllocMap<
+ AllocId,
+ (MemoryKind<Self::MemoryKind>, Allocation<Self::PointerTag, Self::AllocExtra>),
+ > + Default
+ + Clone;
+
+ /// The memory kind to use for copied global memory (held in `tcx`) --
+ /// or None if such memory should not be mutated and thus any such attempt will cause
+ /// a `ModifiedStatic` error to be raised.
+ /// Statics are copied under two circumstances: When they are mutated, and when
+ /// `tag_allocation` (see below) returns an owned allocation
+ /// that is added to the memory so that the work is not done twice.
+ const GLOBAL_KIND: Option<Self::MemoryKind>;
+
+ /// Should the machine panic on allocation failures?
+ const PANIC_ON_ALLOC_FAIL: bool;
+
+ /// Whether memory accesses should be alignment-checked.
+ fn enforce_alignment(memory_extra: &Self::MemoryExtra) -> bool;
+
+ /// Whether, when checking alignment, we should `force_int` and thus support
+ /// custom alignment logic based on whatever the integer address happens to be.
+ fn force_int_for_alignment_check(memory_extra: &Self::MemoryExtra) -> bool;
+
+ /// Whether to enforce the validity invariant
+ fn enforce_validity(ecx: &InterpCx<'mir, 'tcx, Self>) -> bool;
+
+ /// Whether function calls should be [ABI](Abi)-checked.
+ fn enforce_abi(_ecx: &InterpCx<'mir, 'tcx, Self>) -> bool {
+ true
+ }
+
+ /// Entry point for obtaining the MIR of anything that should get evaluated.
+ /// So not just functions and shims, but also const/static initializers, anonymous
+ /// constants, ...
+ fn load_mir(
+ ecx: &InterpCx<'mir, 'tcx, Self>,
+ instance: ty::InstanceDef<'tcx>,
+ ) -> InterpResult<'tcx, &'tcx mir::Body<'tcx>> {
+ Ok(ecx.tcx.instance_mir(instance))
+ }
+
+ /// Entry point to all function calls.
+ ///
+ /// Returns either the mir to use for the call, or `None` if execution should
+ /// just proceed (which usually means this hook did all the work that the
+ /// called function should usually have done). In the latter case, it is
+ /// this hook's responsibility to advance the instruction pointer!
+ /// (This is to support functions like `__rust_maybe_catch_panic` that neither find a MIR
+ /// nor just jump to `ret`, but instead push their own stack frame.)
+ /// Passing `dest`and `ret` in the same `Option` proved very annoying when only one of them
+ /// was used.
+ fn find_mir_or_eval_fn(
+ ecx: &mut InterpCx<'mir, 'tcx, Self>,
+ instance: ty::Instance<'tcx>,
+ abi: Abi,
+ args: &[OpTy<'tcx, Self::PointerTag>],
+ ret: Option<(&PlaceTy<'tcx, Self::PointerTag>, mir::BasicBlock)>,
+ unwind: StackPopUnwind,
+ ) -> InterpResult<'tcx, Option<&'mir mir::Body<'tcx>>>;
+
+ /// Execute `fn_val`. It is the hook's responsibility to advance the instruction
+ /// pointer as appropriate.
+ fn call_extra_fn(
+ ecx: &mut InterpCx<'mir, 'tcx, Self>,
+ fn_val: Self::ExtraFnVal,
+ abi: Abi,
+ args: &[OpTy<'tcx, Self::PointerTag>],
+ ret: Option<(&PlaceTy<'tcx, Self::PointerTag>, mir::BasicBlock)>,
+ unwind: StackPopUnwind,
+ ) -> InterpResult<'tcx>;
+
+ /// Directly process an intrinsic without pushing a stack frame. It is the hook's
+ /// responsibility to advance the instruction pointer as appropriate.
+ fn call_intrinsic(
+ ecx: &mut InterpCx<'mir, 'tcx, Self>,
+ instance: ty::Instance<'tcx>,
+ args: &[OpTy<'tcx, Self::PointerTag>],
+ ret: Option<(&PlaceTy<'tcx, Self::PointerTag>, mir::BasicBlock)>,
+ unwind: StackPopUnwind,
+ ) -> InterpResult<'tcx>;
+
+ /// Called to evaluate `Assert` MIR terminators that trigger a panic.
+ fn assert_panic(
+ ecx: &mut InterpCx<'mir, 'tcx, Self>,
+ msg: &mir::AssertMessage<'tcx>,
+ unwind: Option<mir::BasicBlock>,
+ ) -> InterpResult<'tcx>;
+
+ /// Called to evaluate `Abort` MIR terminator.
+ fn abort(_ecx: &mut InterpCx<'mir, 'tcx, Self>, _msg: String) -> InterpResult<'tcx, !> {
+ throw_unsup_format!("aborting execution is not supported")
+ }
+
+ /// Called for all binary operations where the LHS has pointer type.
+ ///
+ /// Returns a (value, overflowed) pair if the operation succeeded
+ fn binary_ptr_op(
+ ecx: &InterpCx<'mir, 'tcx, Self>,
+ bin_op: mir::BinOp,
+ left: &ImmTy<'tcx, Self::PointerTag>,
+ right: &ImmTy<'tcx, Self::PointerTag>,
+ ) -> InterpResult<'tcx, (Scalar<Self::PointerTag>, bool, Ty<'tcx>)>;
+
+ /// Heap allocations via the `box` keyword.
+ fn box_alloc(
+ ecx: &mut InterpCx<'mir, 'tcx, Self>,
+ dest: &PlaceTy<'tcx, Self::PointerTag>,
+ ) -> InterpResult<'tcx>;
+
+ /// Called to read the specified `local` from the `frame`.
+ /// Since reading a ZST is not actually accessing memory or locals, this is never invoked
+ /// for ZST reads.
+ #[inline]
+ fn access_local(
+ _ecx: &InterpCx<'mir, 'tcx, Self>,
+ frame: &Frame<'mir, 'tcx, Self::PointerTag, Self::FrameExtra>,
+ local: mir::Local,
+ ) -> InterpResult<'tcx, Operand<Self::PointerTag>> {
+ frame.locals[local].access()
+ }
+
+ /// Called to write the specified `local` from the `frame`.
+ /// Since writing a ZST is not actually accessing memory or locals, this is never invoked
+ /// for ZST reads.
+ #[inline]
+ fn access_local_mut<'a>(
+ ecx: &'a mut InterpCx<'mir, 'tcx, Self>,
+ frame: usize,
+ local: mir::Local,
+ ) -> InterpResult<'tcx, Result<&'a mut LocalValue<Self::PointerTag>, MemPlace<Self::PointerTag>>>
+ where
+ 'tcx: 'mir,
+ {
+ ecx.stack_mut()[frame].locals[local].access_mut()
+ }
+
+ /// Called before a basic block terminator is executed.
+ /// You can use this to detect endlessly running programs.
+ #[inline]
+ fn before_terminator(_ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx> {
+ Ok(())
+ }
+
+ /// Called before a global allocation is accessed.
+ /// `def_id` is `Some` if this is the "lazy" allocation of a static.
+ #[inline]
+ fn before_access_global(
+ _memory_extra: &Self::MemoryExtra,
+ _alloc_id: AllocId,
+ _allocation: &Allocation,
+ _static_def_id: Option<DefId>,
+ _is_write: bool,
+ ) -> InterpResult<'tcx> {
+ Ok(())
+ }
+
+ /// Return the `AllocId` for the given thread-local static in the current thread.
+ fn thread_local_static_base_pointer(
+ _ecx: &mut InterpCx<'mir, 'tcx, Self>,
+ def_id: DefId,
+ ) -> InterpResult<'tcx, Pointer<Self::PointerTag>> {
+ throw_unsup!(ThreadLocalStatic(def_id))
+ }
+
+ /// Return the root pointer for the given `extern static`.
+ fn extern_static_base_pointer(
+ mem: &Memory<'mir, 'tcx, Self>,
+ def_id: DefId,
+ ) -> InterpResult<'tcx, Pointer<Self::PointerTag>>;
+
+ /// Return a "base" pointer for the given allocation: the one that is used for direct
+ /// accesses to this static/const/fn allocation, or the one returned from the heap allocator.
+ ///
+ /// Not called on `extern` or thread-local statics (those use the methods above).
+ fn tag_alloc_base_pointer(
+ mem: &Memory<'mir, 'tcx, Self>,
+ ptr: Pointer,
+ ) -> Pointer<Self::PointerTag>;
+
+ /// "Int-to-pointer cast"
+ fn ptr_from_addr(
+ mem: &Memory<'mir, 'tcx, Self>,
+ addr: u64,
+ ) -> Pointer<Option<Self::PointerTag>>;
+
+ /// Convert a pointer with provenance into an allocation-offset pair.
+ fn ptr_get_alloc(
+ mem: &Memory<'mir, 'tcx, Self>,
+ ptr: Pointer<Self::PointerTag>,
+ ) -> (AllocId, Size);
+
+ /// Called to initialize the "extra" state of an allocation and make the pointers
+ /// it contains (in relocations) tagged. The way we construct allocations is
+ /// to always first construct it without extra and then add the extra.
+ /// This keeps uniform code paths for handling both allocations created by CTFE
+ /// for globals, and allocations created by Miri during evaluation.
+ ///
+ /// `kind` is the kind of the allocation being tagged; it can be `None` when
+ /// it's a global and `GLOBAL_KIND` is `None`.
+ ///
+ /// This should avoid copying if no work has to be done! If this returns an owned
+ /// allocation (because a copy had to be done to add tags or metadata), machine memory will
+ /// cache the result. (This relies on `AllocMap::get_or` being able to add the
+ /// owned allocation to the map even when the map is shared.)
+ fn init_allocation_extra<'b>(
+ mem: &Memory<'mir, 'tcx, Self>,
+ id: AllocId,
+ alloc: Cow<'b, Allocation>,
+ kind: Option<MemoryKind<Self::MemoryKind>>,
+ ) -> Cow<'b, Allocation<Self::PointerTag, Self::AllocExtra>>;
+
+ /// Hook for performing extra checks on a memory read access.
+ ///
+ /// Takes read-only access to the allocation so we can keep all the memory read
+ /// operations take `&self`. Use a `RefCell` in `AllocExtra` if you
+ /// need to mutate.
+ #[inline(always)]
+ fn memory_read(
+ _memory_extra: &Self::MemoryExtra,
+ _alloc_extra: &Self::AllocExtra,
+ _tag: Self::PointerTag,
+ _range: AllocRange,
+ ) -> InterpResult<'tcx> {
+ Ok(())
+ }
+
+ /// Hook for performing extra checks on a memory write access.
+ #[inline(always)]
+ fn memory_written(
+ _memory_extra: &mut Self::MemoryExtra,
+ _alloc_extra: &mut Self::AllocExtra,
+ _tag: Self::PointerTag,
+ _range: AllocRange,
+ ) -> InterpResult<'tcx> {
+ Ok(())
+ }
+
+ /// Hook for performing extra operations on a memory deallocation.
+ #[inline(always)]
+ fn memory_deallocated(
+ _memory_extra: &mut Self::MemoryExtra,
+ _alloc_extra: &mut Self::AllocExtra,
+ _tag: Self::PointerTag,
+ _range: AllocRange,
+ ) -> InterpResult<'tcx> {
+ Ok(())
+ }
+
+ /// Executes a retagging operation.
+ #[inline]
+ fn retag(
+ _ecx: &mut InterpCx<'mir, 'tcx, Self>,
+ _kind: mir::RetagKind,
+ _place: &PlaceTy<'tcx, Self::PointerTag>,
+ ) -> InterpResult<'tcx> {
+ Ok(())
+ }
+
+ /// Called immediately before a new stack frame gets pushed.
+ fn init_frame_extra(
+ ecx: &mut InterpCx<'mir, 'tcx, Self>,
+ frame: Frame<'mir, 'tcx, Self::PointerTag>,
+ ) -> InterpResult<'tcx, Frame<'mir, 'tcx, Self::PointerTag, Self::FrameExtra>>;
+
+ /// Borrow the current thread's stack.
+ fn stack(
+ ecx: &'a InterpCx<'mir, 'tcx, Self>,
+ ) -> &'a [Frame<'mir, 'tcx, Self::PointerTag, Self::FrameExtra>];
+
+ /// Mutably borrow the current thread's stack.
+ fn stack_mut(
+ ecx: &'a mut InterpCx<'mir, 'tcx, Self>,
+ ) -> &'a mut Vec<Frame<'mir, 'tcx, Self::PointerTag, Self::FrameExtra>>;
+
+ /// Called immediately after a stack frame got pushed and its locals got initialized.
+ fn after_stack_push(_ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx> {
+ Ok(())
+ }
+
+ /// Called immediately after a stack frame got popped, but before jumping back to the caller.
+ fn after_stack_pop(
+ _ecx: &mut InterpCx<'mir, 'tcx, Self>,
+ _frame: Frame<'mir, 'tcx, Self::PointerTag, Self::FrameExtra>,
+ _unwinding: bool,
+ ) -> InterpResult<'tcx, StackPopJump> {
+ // By default, we do not support unwinding from panics
+ Ok(StackPopJump::Normal)
+ }
+}
+
+// A lot of the flexibility above is just needed for `Miri`, but all "compile-time" machines
+// (CTFE and ConstProp) use the same instance. Here, we share that code.
+pub macro compile_time_machine(<$mir: lifetime, $tcx: lifetime>) {
+ type PointerTag = AllocId;
+ type ExtraFnVal = !;
+
+ type MemoryMap =
+ rustc_data_structures::fx::FxHashMap<AllocId, (MemoryKind<Self::MemoryKind>, Allocation)>;
+ const GLOBAL_KIND: Option<Self::MemoryKind> = None; // no copying of globals from `tcx` to machine memory
+
+ type AllocExtra = ();
+ type FrameExtra = ();
+
+ #[inline(always)]
+ fn enforce_alignment(_memory_extra: &Self::MemoryExtra) -> bool {
+ // We do not check for alignment to avoid having to carry an `Align`
+ // in `ConstValue::ByRef`.
+ false
+ }
+
+ #[inline(always)]
+ fn force_int_for_alignment_check(_memory_extra: &Self::MemoryExtra) -> bool {
+ // We do not support `force_int`.
+ false
+ }
+
+ #[inline(always)]
+ fn enforce_validity(_ecx: &InterpCx<$mir, $tcx, Self>) -> bool {
+ false // for now, we don't enforce validity
+ }
+
+ #[inline(always)]
+ fn call_extra_fn(
+ _ecx: &mut InterpCx<$mir, $tcx, Self>,
+ fn_val: !,
+ _abi: Abi,
+ _args: &[OpTy<$tcx>],
+ _ret: Option<(&PlaceTy<$tcx>, mir::BasicBlock)>,
+ _unwind: StackPopUnwind,
+ ) -> InterpResult<$tcx> {
+ match fn_val {}
+ }
+
+ #[inline(always)]
+ fn init_allocation_extra<'b>(
+ _mem: &Memory<$mir, $tcx, Self>,
+ _id: AllocId,
+ alloc: Cow<'b, Allocation>,
+ _kind: Option<MemoryKind<Self::MemoryKind>>,
+ ) -> Cow<'b, Allocation<Self::PointerTag>> {
+ // We do not use a tag so we can just cheaply forward the allocation
+ alloc
+ }
+
+ fn extern_static_base_pointer(
+ mem: &Memory<$mir, $tcx, Self>,
+ def_id: DefId,
+ ) -> InterpResult<$tcx, Pointer> {
+ // Use the `AllocId` associated with the `DefId`. Any actual *access* will fail.
+ Ok(Pointer::new(mem.tcx.create_static_alloc(def_id), Size::ZERO))
+ }
+
+ #[inline(always)]
+ fn tag_alloc_base_pointer(
+ _mem: &Memory<$mir, $tcx, Self>,
+ ptr: Pointer<AllocId>,
+ ) -> Pointer<AllocId> {
+ ptr
+ }
+
+ #[inline(always)]
+ fn ptr_from_addr(_mem: &Memory<$mir, $tcx, Self>, addr: u64) -> Pointer<Option<AllocId>> {
+ Pointer::new(None, Size::from_bytes(addr))
+ }
+
+ #[inline(always)]
+ fn ptr_get_alloc(_mem: &Memory<$mir, $tcx, Self>, ptr: Pointer<AllocId>) -> (AllocId, Size) {
+ // We know `offset` is relative to the allocation, so we can use `into_parts`.
+ let (alloc_id, offset) = ptr.into_parts();
+ (alloc_id, offset)
+ }
+}
projects / rustc.git / blobdiff