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//! 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_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
use rustc_middle::mir;
use rustc_middle::ty::layout::TyAndLayout;
use rustc_middle::ty::{self, TyCtxt};
use rustc_span::def_id::DefId;
use rustc_target::abi::{Align, Size};
use rustc_target::spec::abi::Abi as CallAbi;
use crate::const_eval::CheckAlignment;
use super::{
AllocBytes, AllocId, AllocRange, Allocation, ConstAllocation, FnArg, Frame, ImmTy, InterpCx,
InterpResult, MPlaceTy, MemoryKind, OpTy, PlaceTy, Pointer, Provenance,
};
/// 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: 'mir>: 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 Provenance: Provenance + Eq + Hash + 'static;
/// When getting the AllocId of a pointer, some extra data is also obtained from the provenance
/// that is passed to memory access hooks so they can do things with it.
type ProvenanceExtra: Copy + '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 every allocation.
type AllocExtra: Debug + Clone + 'tcx;
/// Type for the bytes of the allocation.
type Bytes: AllocBytes + 'static;
/// Memory's allocation map
type MemoryMap: AllocMap<
AllocId,
(
MemoryKind<Self::MemoryKind>,
Allocation<Self::Provenance, Self::AllocExtra, Self::Bytes>,
),
> + 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
/// `adjust_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;
/// Should post-monomorphization checks be run when a stack frame is pushed?
const POST_MONO_CHECKS: bool = true;
/// Whether memory accesses should be alignment-checked.
fn enforce_alignment(ecx: &InterpCx<'mir, 'tcx, Self>) -> CheckAlignment;
/// Whether, when checking alignment, we should look at the actual address and thus support
/// custom alignment logic based on whatever the integer address happens to be.
///
/// If this returns true, Provenance::OFFSET_IS_ADDR must be true.
fn use_addr_for_alignment_check(ecx: &InterpCx<'mir, 'tcx, Self>) -> bool;
fn alignment_check_failed(
ecx: &InterpCx<'mir, 'tcx, Self>,
has: Align,
required: Align,
check: CheckAlignment,
) -> InterpResult<'tcx, ()>;
/// Whether to enforce the validity invariant for a specific layout.
fn enforce_validity(ecx: &InterpCx<'mir, 'tcx, Self>, layout: TyAndLayout<'tcx>) -> bool;
/// Whether function calls should be [ABI](CallAbi)-checked.
fn enforce_abi(_ecx: &InterpCx<'mir, 'tcx, Self>) -> bool {
true
}
/// Whether Assert(OverflowNeg) and Assert(Overflow) MIR terminators should actually
/// check for overflow.
fn ignore_optional_overflow_checks(_ecx: &InterpCx<'mir, 'tcx, Self>) -> bool;
/// 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: CallAbi,
args: &[FnArg<'tcx, Self::Provenance>],
destination: &PlaceTy<'tcx, Self::Provenance>,
target: Option<mir::BasicBlock>,
unwind: mir::UnwindAction,
) -> InterpResult<'tcx, Option<(&'mir mir::Body<'tcx>, ty::Instance<'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: CallAbi,
args: &[FnArg<'tcx, Self::Provenance>],
destination: &PlaceTy<'tcx, Self::Provenance>,
target: Option<mir::BasicBlock>,
unwind: mir::UnwindAction,
) -> 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::Provenance>],
destination: &PlaceTy<'tcx, Self::Provenance>,
target: Option<mir::BasicBlock>,
unwind: mir::UnwindAction,
) -> 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: mir::UnwindAction,
) -> InterpResult<'tcx>;
/// Called to trigger a non-unwinding panic.
fn panic_nounwind(_ecx: &mut InterpCx<'mir, 'tcx, Self>, msg: &str) -> InterpResult<'tcx>;
/// Called when unwinding reached a state where execution should be terminated.
fn unwind_terminate(
ecx: &mut InterpCx<'mir, 'tcx, Self>,
reason: mir::UnwindTerminateReason,
) -> InterpResult<'tcx>;
/// 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::Provenance>,
right: &ImmTy<'tcx, Self::Provenance>,
) -> InterpResult<'tcx, (ImmTy<'tcx, Self::Provenance>, bool)>;
/// Called before writing the specified `local` of the `frame`.
/// Since writing a ZST is not actually accessing memory or locals, this is never invoked
/// for ZST reads.
///
/// Due to borrow checker trouble, we indicate the `frame` as an index rather than an `&mut
/// Frame`.
#[inline(always)]
fn before_access_local_mut<'a>(
_ecx: &'a mut InterpCx<'mir, 'tcx, Self>,
_frame: usize,
_local: mir::Local,
) -> InterpResult<'tcx>
where
'tcx: 'mir,
{
Ok(())
}
/// Called before a basic block terminator is executed.
#[inline]
fn before_terminator(_ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx> {
Ok(())
}
/// Called when the interpreter encounters a `StatementKind::ConstEvalCounter` instruction.
/// You can use this to detect long or endlessly running programs.
#[inline]
fn increment_const_eval_counter(_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(
_tcx: TyCtxt<'tcx>,
_machine: &Self,
_alloc_id: AllocId,
_allocation: ConstAllocation<'tcx>,
_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::Provenance>> {
throw_unsup!(ThreadLocalStatic(def_id))
}
/// Return the root pointer for the given `extern static`.
fn extern_static_base_pointer(
ecx: &InterpCx<'mir, 'tcx, Self>,
def_id: DefId,
) -> InterpResult<'tcx, Pointer<Self::Provenance>>;
/// 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 adjust_alloc_base_pointer(
ecx: &InterpCx<'mir, 'tcx, Self>,
ptr: Pointer,
) -> InterpResult<'tcx, Pointer<Self::Provenance>>;
/// "Int-to-pointer cast"
fn ptr_from_addr_cast(
ecx: &InterpCx<'mir, 'tcx, Self>,
addr: u64,
) -> InterpResult<'tcx, Pointer<Option<Self::Provenance>>>;
/// Marks a pointer as exposed, allowing it's provenance
/// to be recovered. "Pointer-to-int cast"
fn expose_ptr(
ecx: &mut InterpCx<'mir, 'tcx, Self>,
ptr: Pointer<Self::Provenance>,
) -> InterpResult<'tcx>;
/// Convert a pointer with provenance into an allocation-offset pair
/// and extra provenance info.
///
/// The returned `AllocId` must be the same as `ptr.provenance.get_alloc_id()`.
///
/// When this fails, that means the pointer does not point to a live allocation.
fn ptr_get_alloc(
ecx: &InterpCx<'mir, 'tcx, Self>,
ptr: Pointer<Self::Provenance>,
) -> Option<(AllocId, Size, Self::ProvenanceExtra)>;
/// Called to adjust allocations to the Provenance and AllocExtra of this machine.
///
/// 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 adjusted; 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 adjust things), 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.)
///
/// This must only fail if `alloc` contains provenance.
fn adjust_allocation<'b>(
ecx: &InterpCx<'mir, 'tcx, Self>,
id: AllocId,
alloc: Cow<'b, Allocation>,
kind: Option<MemoryKind<Self::MemoryKind>>,
) -> InterpResult<'tcx, Cow<'b, Allocation<Self::Provenance, Self::AllocExtra, Self::Bytes>>>;
fn eval_inline_asm(
_ecx: &mut InterpCx<'mir, 'tcx, Self>,
_template: &'tcx [InlineAsmTemplatePiece],
_operands: &[mir::InlineAsmOperand<'tcx>],
_options: InlineAsmOptions,
) -> InterpResult<'tcx> {
throw_unsup_format!("inline assembly is not supported")
}
/// 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 before_memory_read(
_tcx: TyCtxt<'tcx>,
_machine: &Self,
_alloc_extra: &Self::AllocExtra,
_prov: (AllocId, Self::ProvenanceExtra),
_range: AllocRange,
) -> InterpResult<'tcx> {
Ok(())
}
/// Hook for performing extra checks on a memory write access.
#[inline(always)]
fn before_memory_write(
_tcx: TyCtxt<'tcx>,
_machine: &mut Self,
_alloc_extra: &mut Self::AllocExtra,
_prov: (AllocId, Self::ProvenanceExtra),
_range: AllocRange,
) -> InterpResult<'tcx> {
Ok(())
}
/// Hook for performing extra operations on a memory deallocation.
#[inline(always)]
fn before_memory_deallocation(
_tcx: TyCtxt<'tcx>,
_machine: &mut Self,
_alloc_extra: &mut Self::AllocExtra,
_prov: (AllocId, Self::ProvenanceExtra),
_range: AllocRange,
) -> InterpResult<'tcx> {
Ok(())
}
/// Executes a retagging operation for a single pointer.
/// Returns the possibly adjusted pointer.
#[inline]
fn retag_ptr_value(
_ecx: &mut InterpCx<'mir, 'tcx, Self>,
_kind: mir::RetagKind,
val: &ImmTy<'tcx, Self::Provenance>,
) -> InterpResult<'tcx, ImmTy<'tcx, Self::Provenance>> {
Ok(val.clone())
}
/// Executes a retagging operation on a compound value.
/// Replaces all pointers stored in the given place.
#[inline]
fn retag_place_contents(
_ecx: &mut InterpCx<'mir, 'tcx, Self>,
_kind: mir::RetagKind,
_place: &PlaceTy<'tcx, Self::Provenance>,
) -> InterpResult<'tcx> {
Ok(())
}
/// Called on places used for in-place function argument and return value handling.
///
/// These places need to be protected to make sure the program cannot tell whether the
/// argument/return value was actually copied or passed in-place..
fn protect_in_place_function_argument(
ecx: &mut InterpCx<'mir, 'tcx, Self>,
place: &PlaceTy<'tcx, Self::Provenance>,
) -> InterpResult<'tcx> {
// Without an aliasing model, all we can do is put `Uninit` into the place.
ecx.write_uninit(place)
}
/// Called immediately before a new stack frame gets pushed.
fn init_frame_extra(
ecx: &mut InterpCx<'mir, 'tcx, Self>,
frame: Frame<'mir, 'tcx, Self::Provenance>,
) -> InterpResult<'tcx, Frame<'mir, 'tcx, Self::Provenance, Self::FrameExtra>>;
/// Borrow the current thread's stack.
fn stack<'a>(
ecx: &'a InterpCx<'mir, 'tcx, Self>,
) -> &'a [Frame<'mir, 'tcx, Self::Provenance, Self::FrameExtra>];
/// Mutably borrow the current thread's stack.
fn stack_mut<'a>(
ecx: &'a mut InterpCx<'mir, 'tcx, Self>,
) -> &'a mut Vec<Frame<'mir, 'tcx, Self::Provenance, 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 just before the return value is copied to the caller-provided return place.
fn before_stack_pop(
_ecx: &InterpCx<'mir, 'tcx, Self>,
_frame: &Frame<'mir, 'tcx, Self::Provenance, Self::FrameExtra>,
) -> InterpResult<'tcx> {
Ok(())
}
/// Called immediately after a stack frame got popped, but before jumping back to the caller.
/// The `locals` have already been destroyed!
#[inline(always)]
fn after_stack_pop(
_ecx: &mut InterpCx<'mir, 'tcx, Self>,
_frame: Frame<'mir, 'tcx, Self::Provenance, Self::FrameExtra>,
unwinding: bool,
) -> InterpResult<'tcx, StackPopJump> {
// By default, we do not support unwinding from panics
assert!(!unwinding);
Ok(StackPopJump::Normal)
}
/// Called immediately after actual memory was allocated for a local
/// but before the local's stack frame is updated to point to that memory.
#[inline(always)]
fn after_local_allocated(
_ecx: &mut InterpCx<'mir, 'tcx, Self>,
_frame: usize,
_local: mir::Local,
_mplace: &MPlaceTy<'tcx, Self::Provenance>,
) -> InterpResult<'tcx> {
Ok(())
}
}
/// 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, $tcx: lifetime>) {
type Provenance = AllocId;
type ProvenanceExtra = ();
type ExtraFnVal = !;
type MemoryMap =
rustc_data_structures::fx::FxIndexMap<AllocId, (MemoryKind<Self::MemoryKind>, Allocation)>;
const GLOBAL_KIND: Option<Self::MemoryKind> = None; // no copying of globals from `tcx` to machine memory
type AllocExtra = ();
type FrameExtra = ();
type Bytes = Box<[u8]>;
#[inline(always)]
fn use_addr_for_alignment_check(_ecx: &InterpCx<$mir, $tcx, Self>) -> bool {
// We do not support `use_addr`.
false
}
#[inline(always)]
fn ignore_optional_overflow_checks(_ecx: &InterpCx<$mir, $tcx, Self>) -> bool {
false
}
#[inline(always)]
fn unwind_terminate(
_ecx: &mut InterpCx<$mir, $tcx, Self>,
_reason: mir::UnwindTerminateReason,
) -> InterpResult<$tcx> {
unreachable!("unwinding cannot happen during compile-time evaluation")
}
#[inline(always)]
fn call_extra_fn(
_ecx: &mut InterpCx<$mir, $tcx, Self>,
fn_val: !,
_abi: CallAbi,
_args: &[FnArg<$tcx>],
_destination: &PlaceTy<$tcx, Self::Provenance>,
_target: Option<mir::BasicBlock>,
_unwind: mir::UnwindAction,
) -> InterpResult<$tcx> {
match fn_val {}
}
#[inline(always)]
fn adjust_allocation<'b>(
_ecx: &InterpCx<$mir, $tcx, Self>,
_id: AllocId,
alloc: Cow<'b, Allocation>,
_kind: Option<MemoryKind<Self::MemoryKind>>,
) -> InterpResult<$tcx, Cow<'b, Allocation<Self::Provenance>>> {
Ok(alloc)
}
fn extern_static_base_pointer(
ecx: &InterpCx<$mir, $tcx, Self>,
def_id: DefId,
) -> InterpResult<$tcx, Pointer> {
// Use the `AllocId` associated with the `DefId`. Any actual *access* will fail.
Ok(Pointer::new(ecx.tcx.reserve_and_set_static_alloc(def_id), Size::ZERO))
}
#[inline(always)]
fn adjust_alloc_base_pointer(
_ecx: &InterpCx<$mir, $tcx, Self>,
ptr: Pointer<AllocId>,
) -> InterpResult<$tcx, Pointer<AllocId>> {
Ok(ptr)
}
#[inline(always)]
fn ptr_from_addr_cast(
_ecx: &InterpCx<$mir, $tcx, Self>,
addr: u64,
) -> InterpResult<$tcx, Pointer<Option<AllocId>>> {
// Allow these casts, but make the pointer not dereferenceable.
// (I.e., they behave like transmutation.)
// This is correct because no pointers can ever be exposed in compile-time evaluation.
Ok(Pointer::from_addr_invalid(addr))
}
#[inline(always)]
fn ptr_get_alloc(
_ecx: &InterpCx<$mir, $tcx, Self>,
ptr: Pointer<AllocId>,
) -> Option<(AllocId, Size, Self::ProvenanceExtra)> {
// We know `offset` is relative to the allocation, so we can use `into_parts`.
let (alloc_id, offset) = ptr.into_parts();
Some((alloc_id, offset, ()))
}
}