1 //! The memory subsystem.
3 //! Generally, we use `Pointer` to denote memory addresses. However, some operations
4 //! have a "size"-like parameter, and they take `Scalar` for the address because
5 //! if the size is 0, then the pointer can also be a (properly aligned, non-NULL)
6 //! integer. It is crucial that these operations call `check_align` *before*
7 //! short-circuiting the empty case!
9 use std::collections::VecDeque;
13 use rustc::ty::{self, Instance, ParamEnv, query::TyCtxtAt};
14 use rustc::ty::layout::{Align, TargetDataLayout, Size, HasDataLayout};
15 use rustc_data_structures::fx::{FxHashSet, FxHashMap};
17 use syntax::ast::Mutability;
20 Pointer, AllocId, Allocation, GlobalId, AllocationExtra,
21 InterpResult, Scalar, InterpError, GlobalAlloc, PointerArithmetic,
22 Machine, AllocMap, MayLeak, ErrorHandled, CheckInAllocMsg,
25 #[derive(Debug, PartialEq, Eq, Copy, Clone, Hash)]
26 pub enum MemoryKind<T> {
27 /// Error if deallocated except during a stack pop
29 /// Error if ever deallocated
31 /// Additional memory kinds a machine wishes to distinguish from the builtin ones
35 impl<T: MayLeak> MayLeak for MemoryKind<T> {
37 fn may_leak(self) -> bool {
39 MemoryKind::Stack => false,
40 MemoryKind::Vtable => true,
41 MemoryKind::Machine(k) => k.may_leak()
46 /// Used by `get_size_and_align` to indicate whether the allocation needs to be live.
47 #[derive(Debug, Copy, Clone)]
49 /// Allocation must be live and not a function pointer.
51 /// Allocations needs to be live, but may be a function pointer.
53 /// Allocation may be dead.
57 /// The value of a function pointer.
58 #[derive(Debug, Copy, Clone)]
59 pub enum FnVal<'tcx, Other> {
60 Instance(Instance<'tcx>),
64 impl<'tcx, Other> FnVal<'tcx, Other> {
65 pub fn as_instance(self) -> InterpResult<'tcx, Instance<'tcx>> {
67 FnVal::Instance(instance) =>
71 format!("Expected instance function pointer, got 'other' pointer")
77 // `Memory` has to depend on the `Machine` because some of its operations
78 // (e.g., `get`) call a `Machine` hook.
79 pub struct Memory<'mir, 'tcx, M: Machine<'mir, 'tcx>> {
80 /// Allocations local to this instance of the miri engine. The kind
81 /// helps ensure that the same mechanism is used for allocation and
82 /// deallocation. When an allocation is not found here, it is a
83 /// static and looked up in the `tcx` for read access. Some machines may
84 /// have to mutate this map even on a read-only access to a static (because
85 /// they do pointer provenance tracking and the allocations in `tcx` have
86 /// the wrong type), so we let the machine override this type.
87 /// Either way, if the machine allows writing to a static, doing so will
88 /// create a copy of the static allocation here.
89 // FIXME: this should not be public, but interning currently needs access to it
90 pub(super) alloc_map: M::MemoryMap,
92 /// Map for "extra" function pointers.
93 extra_fn_ptr_map: FxHashMap<AllocId, M::ExtraFnVal>,
95 /// To be able to compare pointers with NULL, and to check alignment for accesses
96 /// to ZSTs (where pointers may dangle), we keep track of the size even for allocations
97 /// that do not exist any more.
98 // FIXME: this should not be public, but interning currently needs access to it
99 pub(super) dead_alloc_map: FxHashMap<AllocId, (Size, Align)>,
101 /// Extra data added by the machine.
102 pub extra: M::MemoryExtra,
104 /// Lets us implement `HasDataLayout`, which is awfully convenient.
105 pub tcx: TyCtxtAt<'tcx>,
108 impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> HasDataLayout for Memory<'mir, 'tcx, M> {
110 fn data_layout(&self) -> &TargetDataLayout {
111 &self.tcx.data_layout
115 // FIXME: Really we shouldn't clone memory, ever. Snapshot machinery should instead
116 // carefully copy only the reachable parts.
117 impl<'mir, 'tcx, M> Clone for Memory<'mir, 'tcx, M>
119 M: Machine<'mir, 'tcx, PointerTag = (), AllocExtra = (), MemoryExtra = ()>,
120 M::MemoryMap: AllocMap<AllocId, (MemoryKind<M::MemoryKinds>, Allocation)>,
122 fn clone(&self) -> Self {
124 alloc_map: self.alloc_map.clone(),
125 extra_fn_ptr_map: self.extra_fn_ptr_map.clone(),
126 dead_alloc_map: self.dead_alloc_map.clone(),
133 impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
134 pub fn new(tcx: TyCtxtAt<'tcx>, extra: M::MemoryExtra) -> Self {
136 alloc_map: M::MemoryMap::default(),
137 extra_fn_ptr_map: FxHashMap::default(),
138 dead_alloc_map: FxHashMap::default(),
145 pub fn tag_static_base_pointer(&self, ptr: Pointer) -> Pointer<M::PointerTag> {
146 ptr.with_tag(M::tag_static_base_pointer(&self.extra, ptr.alloc_id))
149 pub fn create_fn_alloc(
151 fn_val: FnVal<'tcx, M::ExtraFnVal>,
152 ) -> Pointer<M::PointerTag>
154 let id = match fn_val {
155 FnVal::Instance(instance) => self.tcx.alloc_map.lock().create_fn_alloc(instance),
156 FnVal::Other(extra) => {
157 // FIXME(RalfJung): Should we have a cache here?
158 let id = self.tcx.alloc_map.lock().reserve();
159 let old = self.extra_fn_ptr_map.insert(id, extra);
160 assert!(old.is_none());
164 self.tag_static_base_pointer(Pointer::from(id))
171 kind: MemoryKind<M::MemoryKinds>,
172 ) -> Pointer<M::PointerTag> {
173 let alloc = Allocation::undef(size, align);
174 self.allocate_with(alloc, kind)
177 pub fn allocate_static_bytes(
180 kind: MemoryKind<M::MemoryKinds>,
181 ) -> Pointer<M::PointerTag> {
182 let alloc = Allocation::from_byte_aligned_bytes(bytes);
183 self.allocate_with(alloc, kind)
186 pub fn allocate_with(
189 kind: MemoryKind<M::MemoryKinds>,
190 ) -> Pointer<M::PointerTag> {
191 let id = self.tcx.alloc_map.lock().reserve();
192 let (alloc, tag) = M::tag_allocation(&self.extra, id, Cow::Owned(alloc), Some(kind));
193 self.alloc_map.insert(id, (kind, alloc.into_owned()));
194 Pointer::from(id).with_tag(tag)
199 ptr: Pointer<M::PointerTag>,
200 old_size_and_align: Option<(Size, Align)>,
203 kind: MemoryKind<M::MemoryKinds>,
204 ) -> InterpResult<'tcx, Pointer<M::PointerTag>> {
205 if ptr.offset.bytes() != 0 {
206 return err!(ReallocateNonBasePtr);
209 // For simplicities' sake, we implement reallocate as "alloc, copy, dealloc".
210 // This happens so rarely, the perf advantage is outweighed by the maintenance cost.
211 let new_ptr = self.allocate(new_size, new_align, kind);
212 let old_size = match old_size_and_align {
213 Some((size, _align)) => size,
214 None => Size::from_bytes(self.get(ptr.alloc_id)?.bytes.len() as u64),
219 old_size.min(new_size),
220 /*nonoverlapping*/ true,
222 self.deallocate(ptr, old_size_and_align, kind)?;
227 /// Deallocate a local, or do nothing if that local has been made into a static
228 pub fn deallocate_local(&mut self, ptr: Pointer<M::PointerTag>) -> InterpResult<'tcx> {
229 // The allocation might be already removed by static interning.
230 // This can only really happen in the CTFE instance, not in miri.
231 if self.alloc_map.contains_key(&ptr.alloc_id) {
232 self.deallocate(ptr, None, MemoryKind::Stack)
240 ptr: Pointer<M::PointerTag>,
241 old_size_and_align: Option<(Size, Align)>,
242 kind: MemoryKind<M::MemoryKinds>,
243 ) -> InterpResult<'tcx> {
244 trace!("deallocating: {}", ptr.alloc_id);
246 if ptr.offset.bytes() != 0 {
247 return err!(DeallocateNonBasePtr);
250 let (alloc_kind, mut alloc) = match self.alloc_map.remove(&ptr.alloc_id) {
251 Some(alloc) => alloc,
253 // Deallocating static memory -- always an error
254 return match self.tcx.alloc_map.lock().get(ptr.alloc_id) {
255 Some(GlobalAlloc::Function(..)) => err!(DeallocatedWrongMemoryKind(
256 "function".to_string(),
257 format!("{:?}", kind),
259 Some(GlobalAlloc::Static(..)) |
260 Some(GlobalAlloc::Memory(..)) => err!(DeallocatedWrongMemoryKind(
261 "static".to_string(),
262 format!("{:?}", kind),
264 None => err!(DoubleFree)
269 if alloc_kind != kind {
270 return err!(DeallocatedWrongMemoryKind(
271 format!("{:?}", alloc_kind),
272 format!("{:?}", kind),
275 if let Some((size, align)) = old_size_and_align {
276 if size.bytes() != alloc.bytes.len() as u64 || align != alloc.align {
277 let bytes = Size::from_bytes(alloc.bytes.len() as u64);
278 return err!(IncorrectAllocationInformation(size,
285 // Let the machine take some extra action
286 let size = Size::from_bytes(alloc.bytes.len() as u64);
287 AllocationExtra::memory_deallocated(&mut alloc, ptr, size)?;
289 // Don't forget to remember size and align of this now-dead allocation
290 let old = self.dead_alloc_map.insert(
292 (Size::from_bytes(alloc.bytes.len() as u64), alloc.align)
295 bug!("Nothing can be deallocated twice");
301 /// Check if the given scalar is allowed to do a memory access of given `size`
302 /// and `align`. On success, returns `None` for zero-sized accesses (where
303 /// nothing else is left to do) and a `Pointer` to use for the actual access otherwise.
304 /// Crucially, if the input is a `Pointer`, we will test it for liveness
305 /// *even of* the size is 0.
307 /// Everyone accessing memory based on a `Scalar` should use this method to get the
308 /// `Pointer` they need. And even if you already have a `Pointer`, call this method
309 /// to make sure it is sufficiently aligned and not dangling. Not doing that may
312 /// Most of the time you should use `check_mplace_access`, but when you just have a pointer,
313 /// this method is still appropriate.
314 pub fn check_ptr_access(
316 sptr: Scalar<M::PointerTag>,
319 ) -> InterpResult<'tcx, Option<Pointer<M::PointerTag>>> {
320 fn check_offset_align(offset: u64, align: Align) -> InterpResult<'static> {
321 if offset % align.bytes() == 0 {
324 // The biggest power of two through which `offset` is divisible.
325 let offset_pow2 = 1 << offset.trailing_zeros();
326 err!(AlignmentCheckFailed {
327 has: Align::from_bytes(offset_pow2).unwrap(),
333 // Normalize to a `Pointer` if we definitely need one.
334 let normalized = if size.bytes() == 0 {
335 // Can be an integer, just take what we got. We do NOT `force_bits` here;
336 // if this is already a `Pointer` we want to do the bounds checks!
339 // A "real" access, we must get a pointer.
340 Scalar::Ptr(self.force_ptr(sptr)?)
342 Ok(match normalized.to_bits_or_ptr(self.pointer_size(), self) {
344 let bits = bits as u64; // it's ptr-sized
345 assert!(size.bytes() == 0);
346 // Must be non-NULL and aligned.
348 return err!(InvalidNullPointerUsage);
350 check_offset_align(bits, align)?;
354 let (allocation_size, alloc_align) =
355 self.get_size_and_align(ptr.alloc_id, AllocCheck::Dereferencable)?;
356 // Test bounds. This also ensures non-NULL.
357 // It is sufficient to check this for the end pointer. The addition
358 // checks for overflow.
359 let end_ptr = ptr.offset(size, self)?;
360 end_ptr.check_in_alloc(allocation_size, CheckInAllocMsg::MemoryAccessTest)?;
361 // Test align. Check this last; if both bounds and alignment are violated
362 // we want the error to be about the bounds.
363 if alloc_align.bytes() < align.bytes() {
364 // The allocation itself is not aligned enough.
365 // FIXME: Alignment check is too strict, depending on the base address that
366 // got picked we might be aligned even if this check fails.
367 // We instead have to fall back to converting to an integer and checking
368 // the "real" alignment.
369 return err!(AlignmentCheckFailed {
374 check_offset_align(ptr.offset.bytes(), align)?;
376 // We can still be zero-sized in this branch, in which case we have to
378 if size.bytes() == 0 { None } else { Some(ptr) }
383 /// Test if the pointer might be NULL.
384 pub fn ptr_may_be_null(
386 ptr: Pointer<M::PointerTag>,
388 let (size, _align) = self.get_size_and_align(ptr.alloc_id, AllocCheck::MaybeDead)
389 .expect("alloc info with MaybeDead cannot fail");
390 ptr.check_in_alloc(size, CheckInAllocMsg::NullPointerTest).is_err()
394 /// Allocation accessors
395 impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
396 /// Helper function to obtain the global (tcx) allocation for a static.
397 /// This attempts to return a reference to an existing allocation if
398 /// one can be found in `tcx`. That, however, is only possible if `tcx` and
399 /// this machine use the same pointer tag, so it is indirected through
400 /// `M::tag_allocation`.
402 /// Notice that every static has two `AllocId` that will resolve to the same
403 /// thing here: one maps to `GlobalAlloc::Static`, this is the "lazy" ID,
404 /// and the other one is maps to `GlobalAlloc::Memory`, this is returned by
405 /// `const_eval_raw` and it is the "resolved" ID.
406 /// The resolved ID is never used by the interpreted progrma, it is hidden.
407 /// The `GlobalAlloc::Memory` branch here is still reachable though; when a static
408 /// contains a reference to memory that was created during its evaluation (i.e., not to
409 /// another static), those inner references only exist in "resolved" form.
411 memory_extra: &M::MemoryExtra,
414 ) -> InterpResult<'tcx, Cow<'tcx, Allocation<M::PointerTag, M::AllocExtra>>> {
415 let alloc = tcx.alloc_map.lock().get(id);
416 let alloc = match alloc {
417 Some(GlobalAlloc::Memory(mem)) =>
419 Some(GlobalAlloc::Function(..)) =>
420 return err!(DerefFunctionPointer),
422 return err!(DanglingPointerDeref),
423 Some(GlobalAlloc::Static(def_id)) => {
424 // We got a "lazy" static that has not been computed yet.
425 if tcx.is_foreign_item(def_id) {
426 trace!("static_alloc: foreign item {:?}", def_id);
427 M::find_foreign_static(tcx.tcx, def_id)?
429 trace!("static_alloc: Need to compute {:?}", def_id);
430 let instance = Instance::mono(tcx.tcx, def_id);
435 // use the raw query here to break validation cycles. Later uses of the static
436 // will call the full query anyway
437 let raw_const = tcx.const_eval_raw(ty::ParamEnv::reveal_all().and(gid))
439 // no need to report anything, the const_eval call takes care of that
441 assert!(tcx.is_static(def_id));
443 ErrorHandled::Reported => InterpError::ReferencedConstant,
444 ErrorHandled::TooGeneric => InterpError::TooGeneric,
447 // Make sure we use the ID of the resolved memory, not the lazy one!
448 let id = raw_const.alloc_id;
449 let allocation = tcx.alloc_map.lock().unwrap_memory(id);
450 Cow::Borrowed(allocation)
454 // We got tcx memory. Let the machine figure out whether and how to
455 // turn that into memory with the right pointer tag.
456 Ok(M::tag_allocation(
458 id, // always use the ID we got as input, not the "hidden" one.
460 M::STATIC_KIND.map(MemoryKind::Machine),
467 ) -> InterpResult<'tcx, &Allocation<M::PointerTag, M::AllocExtra>> {
468 // The error type of the inner closure here is somewhat funny. We have two
469 // ways of "erroring": An actual error, or because we got a reference from
470 // `get_static_alloc` that we can actually use directly without inserting anything anywhere.
471 // So the error type is `InterpResult<'tcx, &Allocation<M::PointerTag>>`.
472 let a = self.alloc_map.get_or(id, || {
473 let alloc = Self::get_static_alloc(&self.extra, self.tcx, id).map_err(Err)?;
475 Cow::Borrowed(alloc) => {
476 // We got a ref, cheaply return that as an "error" so that the
477 // map does not get mutated.
480 Cow::Owned(alloc) => {
481 // Need to put it into the map and return a ref to that
482 let kind = M::STATIC_KIND.expect(
483 "I got an owned allocation that I have to copy but the machine does \
484 not expect that to happen"
486 Ok((MemoryKind::Machine(kind), alloc))
490 // Now unpack that funny error type
500 ) -> InterpResult<'tcx, &mut Allocation<M::PointerTag, M::AllocExtra>> {
502 let memory_extra = &self.extra;
503 let a = self.alloc_map.get_mut_or(id, || {
504 // Need to make a copy, even if `get_static_alloc` is able
505 // to give us a cheap reference.
506 let alloc = Self::get_static_alloc(memory_extra, tcx, id)?;
507 if alloc.mutability == Mutability::Immutable {
508 return err!(ModifiedConstantMemory);
510 match M::STATIC_KIND {
511 Some(kind) => Ok((MemoryKind::Machine(kind), alloc.into_owned())),
512 None => err!(ModifiedStatic),
515 // Unpack the error type manually because type inference doesn't
516 // work otherwise (and we cannot help it because `impl Trait`)
521 if a.mutability == Mutability::Immutable {
522 return err!(ModifiedConstantMemory);
529 /// Obtain the size and alignment of an allocation, even if that allocation has
530 /// been deallocated.
532 /// If `liveness` is `AllocCheck::MaybeDead`, this function always returns `Ok`.
533 pub fn get_size_and_align(
536 liveness: AllocCheck,
537 ) -> InterpResult<'static, (Size, Align)> {
538 let alloc_or_size_align = self.alloc_map.get_or(id, || -> Result<_, InterpResult<'static, (Size, Align)>> {
539 // Can't do this in the match argument, we may get cycle errors since the lock would
540 // be held throughout the match.
541 let alloc = self.tcx.alloc_map.lock().get(id);
543 Some(GlobalAlloc::Static(did)) => {
544 // Use size and align of the type
545 let ty = self.tcx.type_of(did);
546 let layout = self.tcx.layout_of(ParamEnv::empty().and(ty)).unwrap();
547 Ok((layout.size, layout.align.abi))
549 Some(GlobalAlloc::Memory(alloc)) =>
550 // this duplicates the logic on the `match alloc_or_size_align`, but due to the
551 // API of `get_or` there's no way around that.
552 Ok((Size::from_bytes(alloc.bytes.len() as u64), alloc.align)),
553 Some(GlobalAlloc::Function(_)) => if let AllocCheck::Dereferencable = liveness {
554 // The caller requested no function pointers.
555 err!(DerefFunctionPointer)
557 Ok((Size::ZERO, Align::from_bytes(1).unwrap()))
559 // The rest must be dead.
560 None => if let AllocCheck::MaybeDead = liveness {
561 // Deallocated pointers are allowed, we should be able to find
563 Ok(*self.dead_alloc_map.get(&id)
564 .expect("deallocated pointers should all be recorded in `dead_alloc_map`"))
566 err!(DanglingPointerDeref)
570 match alloc_or_size_align {
571 Ok((_, alloc)) => Ok((Size::from_bytes(alloc.bytes.len() as u64), alloc.align)),
576 fn get_fn_alloc(&self, id: AllocId) -> InterpResult<'tcx, FnVal<'tcx, M::ExtraFnVal>> {
577 trace!("reading fn ptr: {}", id);
578 if let Some(extra) = self.extra_fn_ptr_map.get(&id) {
579 Ok(FnVal::Other(*extra))
581 match self.tcx.alloc_map.lock().get(id) {
582 Some(GlobalAlloc::Function(instance)) => Ok(FnVal::Instance(instance)),
583 _ => Err(InterpError::ExecuteMemory.into()),
590 ptr: Scalar<M::PointerTag>,
591 ) -> InterpResult<'tcx, FnVal<'tcx, M::ExtraFnVal>> {
592 let ptr = self.force_ptr(ptr)?; // We definitely need a pointer value.
593 if ptr.offset.bytes() != 0 {
594 return err!(InvalidFunctionPointer);
596 self.get_fn_alloc(ptr.alloc_id)
599 pub fn mark_immutable(&mut self, id: AllocId) -> InterpResult<'tcx> {
600 self.get_mut(id)?.mutability = Mutability::Immutable;
604 /// For debugging, print an allocation and all allocations it points to, recursively.
605 pub fn dump_alloc(&self, id: AllocId) {
606 self.dump_allocs(vec![id]);
609 fn dump_alloc_helper<Tag, Extra>(
611 allocs_seen: &mut FxHashSet<AllocId>,
612 allocs_to_print: &mut VecDeque<AllocId>,
614 alloc: &Allocation<Tag, Extra>,
619 let prefix_len = msg.len();
620 let mut relocations = vec![];
622 for i in 0..(alloc.bytes.len() as u64) {
623 let i = Size::from_bytes(i);
624 if let Some(&(_, target_id)) = alloc.relocations.get(&i) {
625 if allocs_seen.insert(target_id) {
626 allocs_to_print.push_back(target_id);
628 relocations.push((i, target_id));
630 if alloc.undef_mask.is_range_defined(i, i + Size::from_bytes(1)).is_ok() {
631 // this `as usize` is fine, since `i` came from a `usize`
632 write!(msg, "{:02x} ", alloc.bytes[i.bytes() as usize]).unwrap();
639 "{}({} bytes, alignment {}){}",
646 if !relocations.is_empty() {
648 write!(msg, "{:1$}", "", prefix_len).unwrap(); // Print spaces.
649 let mut pos = Size::ZERO;
650 let relocation_width = (self.pointer_size().bytes() - 1) * 3;
651 for (i, target_id) in relocations {
652 // this `as usize` is fine, since we can't print more chars than `usize::MAX`
653 write!(msg, "{:1$}", "", ((i - pos) * 3).bytes() as usize).unwrap();
654 let target = format!("({})", target_id);
655 // this `as usize` is fine, since we can't print more chars than `usize::MAX`
656 write!(msg, "└{0:─^1$}┘ ", target, relocation_width as usize).unwrap();
657 pos = i + self.pointer_size();
663 /// For debugging, print a list of allocations and all allocations they point to, recursively.
664 pub fn dump_allocs(&self, mut allocs: Vec<AllocId>) {
665 if !log_enabled!(::log::Level::Trace) {
670 let mut allocs_to_print = VecDeque::from(allocs);
671 let mut allocs_seen = FxHashSet::default();
673 while let Some(id) = allocs_to_print.pop_front() {
674 let msg = format!("Alloc {:<5} ", format!("{}:", id));
677 match self.alloc_map.get_or(id, || Err(())) {
678 Ok((kind, alloc)) => {
679 let extra = match kind {
680 MemoryKind::Stack => " (stack)".to_owned(),
681 MemoryKind::Vtable => " (vtable)".to_owned(),
682 MemoryKind::Machine(m) => format!(" ({:?})", m),
684 self.dump_alloc_helper(
685 &mut allocs_seen, &mut allocs_to_print,
691 match self.tcx.alloc_map.lock().get(id) {
692 Some(GlobalAlloc::Memory(alloc)) => {
693 self.dump_alloc_helper(
694 &mut allocs_seen, &mut allocs_to_print,
695 msg, alloc, " (immutable)".to_owned()
698 Some(GlobalAlloc::Function(func)) => {
699 trace!("{} {}", msg, func);
701 Some(GlobalAlloc::Static(did)) => {
702 trace!("{} {:?}", msg, did);
705 trace!("{} (deallocated)", msg);
714 pub fn leak_report(&self) -> usize {
715 trace!("### LEAK REPORT ###");
716 let leaks: Vec<_> = self.alloc_map.filter_map_collect(|&id, &(kind, _)| {
717 if kind.may_leak() { None } else { Some(id) }
720 self.dump_allocs(leaks);
724 /// This is used by [priroda](https://github.com/oli-obk/priroda)
725 pub fn alloc_map(&self) -> &M::MemoryMap {
730 /// Reading and writing.
731 impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
732 /// Reads the given number of bytes from memory. Returns them as a slice.
734 /// Performs appropriate bounds checks.
737 ptr: Scalar<M::PointerTag>,
739 ) -> InterpResult<'tcx, &[u8]> {
740 let ptr = match self.check_ptr_access(ptr, size, Align::from_bytes(1).unwrap())? {
742 None => return Ok(&[]), // zero-sized access
744 self.get(ptr.alloc_id)?.get_bytes(self, ptr, size)
747 /// Reads a 0-terminated sequence of bytes from memory. Returns them as a slice.
749 /// Performs appropriate bounds checks.
750 pub fn read_c_str(&self, ptr: Scalar<M::PointerTag>) -> InterpResult<'tcx, &[u8]> {
751 let ptr = self.force_ptr(ptr)?; // We need to read at least 1 byte, so we *need* a ptr.
752 self.get(ptr.alloc_id)?.read_c_str(self, ptr)
755 /// Expects the caller to have checked bounds and alignment.
758 src: Pointer<M::PointerTag>,
759 dest: Pointer<M::PointerTag>,
761 nonoverlapping: bool,
762 ) -> InterpResult<'tcx> {
763 self.copy_repeatedly(src, dest, size, 1, nonoverlapping)
766 /// Expects the caller to have checked bounds and alignment.
767 pub fn copy_repeatedly(
769 src: Pointer<M::PointerTag>,
770 dest: Pointer<M::PointerTag>,
773 nonoverlapping: bool,
774 ) -> InterpResult<'tcx> {
775 // first copy the relocations to a temporary buffer, because
776 // `get_bytes_mut` will clear the relocations, which is correct,
777 // since we don't want to keep any relocations at the target.
778 // (`get_bytes_with_undef_and_ptr` below checks that there are no
779 // relocations overlapping the edges; those would not be handled correctly).
781 let relocations = self.get(src.alloc_id)?.relocations(self, src, size);
782 if relocations.is_empty() {
783 // nothing to copy, ignore even the `length` loop
786 let mut new_relocations = Vec::with_capacity(relocations.len() * (length as usize));
788 new_relocations.extend(
791 .map(|&(offset, reloc)| {
792 // compute offset for current repetition
793 let dest_offset = dest.offset + (i * size);
795 // shift offsets from source allocation to destination allocation
796 offset + dest_offset - src.offset,
807 let tcx = self.tcx.tcx;
809 // This checks relocation edges on the src.
810 let src_bytes = self.get(src.alloc_id)?
811 .get_bytes_with_undef_and_ptr(&tcx, src, size)?
813 let dest_bytes = self.get_mut(dest.alloc_id)?
814 .get_bytes_mut(&tcx, dest, size * length)?
817 // SAFE: The above indexing would have panicked if there weren't at least `size` bytes
818 // behind `src` and `dest`. Also, we use the overlapping-safe `ptr::copy` if `src` and
819 // `dest` could possibly overlap.
820 // The pointers above remain valid even if the `HashMap` table is moved around because they
821 // point into the `Vec` storing the bytes.
823 assert_eq!(size.bytes() as usize as u64, size.bytes());
824 if src.alloc_id == dest.alloc_id {
826 if (src.offset <= dest.offset && src.offset + size > dest.offset) ||
827 (dest.offset <= src.offset && dest.offset + size > src.offset)
829 return err!(Intrinsic(
830 "copy_nonoverlapping called on overlapping ranges".to_string(),
837 dest_bytes.offset((size.bytes() * i) as isize),
838 size.bytes() as usize);
842 ptr::copy_nonoverlapping(src_bytes,
843 dest_bytes.offset((size.bytes() * i) as isize),
844 size.bytes() as usize);
849 // copy definedness to the destination
850 self.copy_undef_mask(src, dest, size, length)?;
851 // copy the relocations to the destination
852 self.get_mut(dest.alloc_id)?.relocations.insert_presorted(relocations);
859 impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
860 // FIXME: Add a fast version for the common, nonoverlapping case
863 src: Pointer<M::PointerTag>,
864 dest: Pointer<M::PointerTag>,
867 ) -> InterpResult<'tcx> {
868 // The bits have to be saved locally before writing to dest in case src and dest overlap.
869 assert_eq!(size.bytes() as usize as u64, size.bytes());
871 let undef_mask = &self.get(src.alloc_id)?.undef_mask;
873 // Since we are copying `size` bytes from `src` to `dest + i * size` (`for i in 0..repeat`),
874 // a naive undef mask copying algorithm would repeatedly have to read the undef mask from
875 // the source and write it to the destination. Even if we optimized the memory accesses,
876 // we'd be doing all of this `repeat` times.
877 // Therefor we precompute a compressed version of the undef mask of the source value and
878 // then write it back `repeat` times without computing any more information from the source.
880 // a precomputed cache for ranges of defined/undefined bits
881 // 0000010010001110 will become
882 // [5, 1, 2, 1, 3, 3, 1]
883 // where each element toggles the state
884 let mut ranges = smallvec::SmallVec::<[u64; 1]>::new();
885 let first = undef_mask.get(src.offset);
888 for i in 1..size.bytes() {
889 // FIXME: optimize to bitshift the current undef block's bits and read the top bit
890 if undef_mask.get(src.offset + Size::from_bytes(i)) == cur {
893 ranges.push(cur_len);
899 // now fill in all the data
900 let dest_allocation = self.get_mut(dest.alloc_id)?;
901 // an optimization where we can just overwrite an entire range of definedness bits if
902 // they are going to be uniformly `1` or `0`.
903 if ranges.is_empty() {
904 dest_allocation.undef_mask.set_range_inbounds(
906 dest.offset + size * repeat,
912 // remember to fill in the trailing bits
913 ranges.push(cur_len);
915 for mut j in 0..repeat {
917 j += dest.offset.bytes();
919 for range in &ranges {
922 dest_allocation.undef_mask.set_range_inbounds(
923 Size::from_bytes(old_j),
935 scalar: Scalar<M::PointerTag>,
936 ) -> InterpResult<'tcx, Pointer<M::PointerTag>> {
938 Scalar::Ptr(ptr) => Ok(ptr),
939 _ => M::int_to_ptr(&self, scalar.to_usize(self)?)
945 scalar: Scalar<M::PointerTag>,
947 ) -> InterpResult<'tcx, u128> {
948 match scalar.to_bits_or_ptr(size, self) {
949 Ok(bits) => Ok(bits),
950 Err(ptr) => Ok(M::ptr_to_int(&self, ptr)? as u128)