X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=src%2Fstacked_borrows.rs;h=616950eb0a0a44a5ca923ae78a7a68c3c2c6e9e3;hb=69fb6413ddc5b7fd5d9cb0a68ebf58ee513bf9d5;hp=2188b9d5394a310557ba0cb8a2ba67054c04f075;hpb=f912a8b0540fbade8394068a264fb729c237ef3d;p=rust.git diff --git a/src/stacked_borrows.rs b/src/stacked_borrows.rs index 2188b9d5394..616950eb0a0 100644 --- a/src/stacked_borrows.rs +++ b/src/stacked_borrows.rs @@ -2,19 +2,19 @@ //! for further information. use std::cell::RefCell; -use std::collections::{HashMap, HashSet}; -use std::rc::Rc; use std::fmt; use std::num::NonZeroU64; +use std::rc::Rc; -use rustc::ty::{self, layout::Size}; -use rustc::hir::{MutMutable, MutImmutable}; -use rustc::mir::RetagKind; +use log::trace; -use crate::{ - InterpResult, HelpersEvalContextExt, - MemoryKind, MiriMemoryKind, RangeMap, AllocId, Pointer, Immediate, ImmTy, PlaceTy, MPlaceTy, -}; +use rustc_data_structures::fx::{FxHashMap, FxHashSet}; +use rustc_middle::mir::RetagKind; +use rustc_middle::ty; +use rustc_target::abi::{Align, LayoutOf, Size}; +use rustc_hir::Mutability; + +use crate::*; pub type PtrId = NonZeroU64; pub type CallId = NonZeroU64; @@ -82,7 +82,6 @@ pub struct Stack { borrows: Vec, } - /// Extra per-allocation state. #[derive(Clone, Debug)] pub struct Stacks { @@ -100,11 +99,17 @@ pub struct GlobalState { /// Table storing the "base" tag for each allocation. /// The base tag is the one used for the initial pointer. /// We need this in a separate table to handle cyclic statics. - base_ptr_ids: HashMap, + base_ptr_ids: FxHashMap, /// Next unused call ID (for protectors). next_call_id: CallId, /// Those call IDs corresponding to functions that are still running. - active_calls: HashSet, + active_calls: FxHashSet, + /// The pointer id to trace + tracked_pointer_tag: Option, + /// The call id to trace + tracked_call_id: Option, + /// Whether to track raw pointers. + track_raw: bool, } /// Memory extra state gives us interior mutable access to the global state. pub type MemoryExtra = Rc>; @@ -151,20 +156,24 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { } /// Utilities for initialization and ID generation -impl Default for GlobalState { - fn default() -> Self { +impl GlobalState { + pub fn new(tracked_pointer_tag: Option, tracked_call_id: Option, track_raw: bool) -> Self { GlobalState { next_ptr_id: NonZeroU64::new(1).unwrap(), - base_ptr_ids: HashMap::default(), + base_ptr_ids: FxHashMap::default(), next_call_id: NonZeroU64::new(1).unwrap(), - active_calls: HashSet::default(), + active_calls: FxHashSet::default(), + tracked_pointer_tag, + tracked_call_id, + track_raw, } } -} -impl GlobalState { fn new_ptr(&mut self) -> PtrId { let id = self.next_ptr_id; + if Some(id) == self.tracked_pointer_tag { + register_diagnostic(NonHaltingDiagnostic::CreatedPointerTag(id)); + } self.next_ptr_id = NonZeroU64::new(id.get() + 1).unwrap(); id } @@ -172,6 +181,9 @@ fn new_ptr(&mut self) -> PtrId { pub fn new_call(&mut self) -> CallId { let id = self.next_call_id; trace!("new_call: Assigning ID {}", id); + if Some(id) == self.tracked_call_id { + register_diagnostic(NonHaltingDiagnostic::CreatedCallId(id)); + } assert!(self.active_calls.insert(id)); self.next_call_id = NonZeroU64::new(id.get() + 1).unwrap(); id @@ -185,7 +197,7 @@ fn is_active(&self, id: CallId) -> bool { self.active_calls.contains(&id) } - pub fn static_base_ptr(&mut self, id: AllocId) -> Tag { + pub fn global_base_ptr(&mut self, id: AllocId) -> Tag { self.base_ptr_ids.get(&id).copied().unwrap_or_else(|| { let tag = Tag::Tagged(self.new_ptr()); trace!("New allocation {:?} has base tag {:?}", id, tag); @@ -195,6 +207,14 @@ pub fn static_base_ptr(&mut self, id: AllocId) -> Tag { } } +/// Error reporting +fn err_sb_ub(msg: String) -> InterpError<'static> { + err_machine_stop!(TerminationInfo::ExperimentalUb { + msg, + url: format!("https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/stacked-borrows.md"), + }) +} + // # Stacked Borrows Core Begin /// We need to make at least the following things true: @@ -216,7 +236,8 @@ impl Permission { /// This defines for a given permission, whether it permits the given kind of access. fn grants(self, access: AccessKind) -> bool { // Disabled grants nothing. Otherwise, all items grant read access, and except for SharedReadOnly they grant write access. - self != Permission::Disabled && (access == AccessKind::Read || self != Permission::SharedReadOnly) + self != Permission::Disabled + && (access == AccessKind::Read || self != Permission::SharedReadOnly) } } @@ -225,32 +246,28 @@ impl<'tcx> Stack { /// Find the item granting the given kind of access to the given tag, and return where /// it is on the stack. fn find_granting(&self, access: AccessKind, tag: Tag) -> Option { - self.borrows.iter() + self.borrows + .iter() .enumerate() // we also need to know *where* in the stack .rev() // search top-to-bottom // Return permission of first item that grants access. // We require a permission with the right tag, ensuring U3 and F3. - .find_map(|(idx, item)| - if tag == item.tag && item.perm.grants(access) { - Some(idx) - } else { - None - } + .find_map( + |(idx, item)| { + if tag == item.tag && item.perm.grants(access) { Some(idx) } else { None } + }, ) } /// Find the first write-incompatible item above the given one -- /// i.e, find the height to which the stack will be truncated when writing to `granting`. - fn find_first_write_incompaible(&self, granting: usize) -> usize { + fn find_first_write_incompatible(&self, granting: usize) -> usize { let perm = self.borrows[granting].perm; match perm { - Permission::SharedReadOnly => - bug!("Cannot use SharedReadOnly for writing"), - Permission::Disabled => - bug!("Cannot use Disabled for anything"), - Permission::Unique => - // On a write, everything above us is incompatible. - granting + 1, + Permission::SharedReadOnly => bug!("Cannot use SharedReadOnly for writing"), + Permission::Disabled => bug!("Cannot use Disabled for anything"), + // On a write, everything above us is incompatible. + Permission::Unique => granting + 1, Permission::SharedReadWrite => { // The SharedReadWrite *just* above us are compatible, to skip those. let mut idx = granting + 1; @@ -270,17 +287,23 @@ fn find_first_write_incompaible(&self, granting: usize) -> usize { /// Check if the given item is protected. fn check_protector(item: &Item, tag: Option, global: &GlobalState) -> InterpResult<'tcx> { + if let Tag::Tagged(id) = item.tag { + if Some(id) == global.tracked_pointer_tag { + register_diagnostic(NonHaltingDiagnostic::PoppedPointerTag(item.clone())); + } + } if let Some(call) = item.protector { if global.is_active(call) { if let Some(tag) = tag { - throw_ub!(UbExperimental(format!( + Err(err_sb_ub(format!( "not granting access to tag {:?} because incompatible item is protected: {:?}", tag, item - ))); + )))? } else { - throw_ub!(UbExperimental(format!( - "deallocating while item is protected: {:?}", item - ))); + Err(err_sb_ub(format!( + "deallocating while item is protected: {:?}", + item + )))? } } } @@ -289,30 +312,26 @@ fn check_protector(item: &Item, tag: Option, global: &GlobalState) -> Inter /// Test if a memory `access` using pointer tagged `tag` is granted. /// If yes, return the index of the item that granted it. - fn access( - &mut self, - access: AccessKind, - tag: Tag, - global: &GlobalState, - ) -> InterpResult<'tcx> { + fn access(&mut self, access: AccessKind, ptr: Pointer, global: &GlobalState) -> InterpResult<'tcx> { // Two main steps: Find granting item, remove incompatible items above. // Step 1: Find granting item. - let granting_idx = self.find_granting(access, tag) - .ok_or_else(|| err_ub!(UbExperimental(format!( - "no item granting {} to tag {:?} found in borrow stack", - access, tag, - ))))?; + let granting_idx = self.find_granting(access, ptr.tag).ok_or_else(|| { + err_sb_ub(format!( + "no item granting {} to tag {:?} at {} found in borrow stack.", + access, ptr.tag, ptr.erase_tag(), + )) + })?; // Step 2: Remove incompatible items above them. Make sure we do not remove protected // items. Behavior differs for reads and writes. if access == AccessKind::Write { // Remove everything above the write-compatible items, like a proper stack. This makes sure read-only and unique // pointers become invalid on write accesses (ensures F2a, and ensures U2 for write accesses). - let first_incompatible_idx = self.find_first_write_incompaible(granting_idx); + let first_incompatible_idx = self.find_first_write_incompatible(granting_idx); for item in self.borrows.drain(first_incompatible_idx..).rev() { trace!("access: popping item {:?}", item); - Stack::check_protector(&item, Some(tag), global)?; + Stack::check_protector(&item, Some(ptr.tag), global)?; } } else { // On a read, *disable* all `Unique` above the granting item. This ensures U2 for read accesses. @@ -323,11 +342,11 @@ fn access( // This pattern occurs a lot in the standard library: create a raw pointer, then also create a shared // reference and use that. // We *disable* instead of removing `Unique` to avoid "connecting" two neighbouring blocks of SRWs. - for idx in (granting_idx+1 .. self.borrows.len()).rev() { + for idx in ((granting_idx + 1)..self.borrows.len()).rev() { let item = &mut self.borrows[idx]; if item.perm == Permission::Unique { trace!("access: disabling item {:?}", item); - Stack::check_protector(item, Some(tag), global)?; + Stack::check_protector(item, Some(ptr.tag), global)?; item.perm = Permission::Disabled; } } @@ -339,17 +358,14 @@ fn access( /// Deallocate a location: Like a write access, but also there must be no /// active protectors at all because we will remove all items. - fn dealloc( - &mut self, - tag: Tag, - global: &GlobalState, - ) -> InterpResult<'tcx> { + fn dealloc(&mut self, ptr: Pointer, global: &GlobalState) -> InterpResult<'tcx> { // Step 1: Find granting item. - self.find_granting(AccessKind::Write, tag) - .ok_or_else(|| err_ub!(UbExperimental(format!( - "no item granting write access for deallocation to tag {:?} found in borrow stack", - tag, - ))))?; + self.find_granting(AccessKind::Write, ptr.tag).ok_or_else(|| { + err_sb_ub(format!( + "no item granting write access for deallocation to tag {:?} at {} found in borrow stack", + ptr.tag, ptr.erase_tag(), + )) + })?; // Step 2: Remove all items. Also checks for protectors. for item in self.borrows.drain(..).rev() { @@ -359,39 +375,35 @@ fn dealloc( Ok(()) } - /// Derived a new pointer from one with the given tag. + /// Derive a new pointer from one with the given tag. /// `weak` controls whether this operation is weak or strong: weak granting does not act as /// an access, and they add the new item directly on top of the one it is derived /// from instead of all the way at the top of the stack. - fn grant( - &mut self, - derived_from: Tag, - new: Item, - global: &GlobalState, - ) -> InterpResult<'tcx> { + fn grant(&mut self, derived_from: Pointer, new: Item, global: &GlobalState) -> InterpResult<'tcx> { // Figure out which access `perm` corresponds to. - let access = if new.perm.grants(AccessKind::Write) { - AccessKind::Write - } else { - AccessKind::Read - }; + let access = + if new.perm.grants(AccessKind::Write) { AccessKind::Write } else { AccessKind::Read }; // Now we figure out which item grants our parent (`derived_from`) this kind of access. // We use that to determine where to put the new item. - let granting_idx = self.find_granting(access, derived_from) - .ok_or_else(|| err_ub!(UbExperimental(format!( - "trying to reborrow for {:?}, but parent tag {:?} does not have an appropriate item in the borrow stack", new.perm, derived_from, - ))))?; + let granting_idx = self.find_granting(access, derived_from.tag) + .ok_or_else(|| err_sb_ub(format!( + "trying to reborrow for {:?} at {}, but parent tag {:?} does not have an appropriate item in the borrow stack", + new.perm, derived_from.erase_tag(), derived_from.tag, + )))?; // Compute where to put the new item. // Either way, we ensure that we insert the new item in a way such that between // `derived_from` and the new one, there are only items *compatible with* `derived_from`. let new_idx = if new.perm == Permission::SharedReadWrite { - assert!(access == AccessKind::Write, "this case only makes sense for stack-like accesses"); + assert!( + access == AccessKind::Write, + "this case only makes sense for stack-like accesses" + ); // SharedReadWrite can coexist with "existing loans", meaning they don't act like a write // access. Instead of popping the stack, we insert the item at the place the stack would // be popped to (i.e., we insert it above all the write-compatible items). // This ensures F2b by adding the new item below any potentially existing `SharedReadOnly`. - self.find_first_write_incompaible(granting_idx) + self.find_first_write_incompatible(granting_idx) } else { // A "safe" reborrow for a pointer that actually expects some aliasing guarantees. // Here, creating a reference actually counts as an access. @@ -406,7 +418,7 @@ fn grant( }; // Put the new item there. As an optimization, deduplicate if it is equal to one of its new neighbors. - if self.borrows[new_idx-1] == new || self.borrows.get(new_idx) == Some(&new) { + if self.borrows[new_idx - 1] == new || self.borrows.get(new_idx) == Some(&new) { // Optimization applies, done. trace!("reborrow: avoiding adding redundant item {:?}", new); } else { @@ -422,21 +434,11 @@ fn grant( /// Map per-stack operations to higher-level per-location-range operations. impl<'tcx> Stacks { /// Creates new stack with initial tag. - fn new( - size: Size, - perm: Permission, - tag: Tag, - extra: MemoryExtra, - ) -> Self { + fn new(size: Size, perm: Permission, tag: Tag, extra: MemoryExtra) -> Self { let item = Item { perm, tag, protector: None }; - let stack = Stack { - borrows: vec![item], - }; + let stack = Stack { borrows: vec![item] }; - Stacks { - stacks: RefCell::new(RangeMap::new(size, stack)), - global: extra, - } + Stacks { stacks: RefCell::new(RangeMap::new(size, stack)), global: extra } } /// Call `f` on every stack in the range. @@ -444,12 +446,14 @@ fn for_each( &self, ptr: Pointer, size: Size, - f: impl Fn(&mut Stack, &GlobalState) -> InterpResult<'tcx>, + f: impl Fn(Pointer, &mut Stack, &GlobalState) -> InterpResult<'tcx>, ) -> InterpResult<'tcx> { let global = self.global.borrow(); let mut stacks = self.stacks.borrow_mut(); - for stack in stacks.iter_mut(ptr.offset, size) { - f(stack, &*global)?; + for (offset, stack) in stacks.iter_mut(ptr.offset, size) { + let mut cur_ptr = ptr; + cur_ptr.offset = offset; + f(cur_ptr, stack, &*global)?; } Ok(()) } @@ -464,46 +468,40 @@ pub fn new_allocation( kind: MemoryKind, ) -> (Self, Tag) { let (tag, perm) = match kind { - MemoryKind::Stack => - // New unique borrow. This tag is not accessible by the program, - // so it will only ever be used when using the local directly (i.e., - // not through a pointer). That is, whenever we directly write to a local, this will pop - // everything else off the stack, invalidating all previous pointers, - // and in particular, *all* raw pointers. - (Tag::Tagged(extra.borrow_mut().new_ptr()), Permission::Unique), - MemoryKind::Machine(MiriMemoryKind::Static) => - (extra.borrow_mut().static_base_ptr(id), Permission::SharedReadWrite), - _ => - (Tag::Untagged, Permission::SharedReadWrite), + // New unique borrow. This tag is not accessible by the program, + // so it will only ever be used when using the local directly (i.e., + // not through a pointer). That is, whenever we directly write to a local, this will pop + // everything else off the stack, invalidating all previous pointers, + // and in particular, *all* raw pointers. + MemoryKind::Stack => (Tag::Tagged(extra.borrow_mut().new_ptr()), Permission::Unique), + // `Global` memory can be referenced by global pointers from `tcx`. + // Thus we call `global_base_ptr` such that the global pointers get the same tag + // as what we use here. + // `ExternStatic` is used for extern statics, and thus must also be listed here. + // `Env` we list because we can get away with precise tracking there. + // The base pointer is not unique, so the base permission is `SharedReadWrite`. + MemoryKind::Machine(MiriMemoryKind::Global | MiriMemoryKind::ExternStatic | MiriMemoryKind::Tls | MiriMemoryKind::Env) => + (extra.borrow_mut().global_base_ptr(id), Permission::SharedReadWrite), + // Everything else we handle like raw pointers for now. + _ => { + let mut extra = extra.borrow_mut(); + let tag = if extra.track_raw { Tag::Tagged(extra.new_ptr()) } else { Tag::Untagged }; + (tag, Permission::SharedReadWrite) + } }; - let stack = Stacks::new(size, perm, tag, extra); - (stack, tag) + (Stacks::new(size, perm, tag, extra), tag) } #[inline(always)] - pub fn memory_read<'tcx>( - &self, - ptr: Pointer, - size: Size, - ) -> InterpResult<'tcx> { + pub fn memory_read<'tcx>(&self, ptr: Pointer, size: Size) -> InterpResult<'tcx> { trace!("read access with tag {:?}: {:?}, size {}", ptr.tag, ptr.erase_tag(), size.bytes()); - self.for_each(ptr, size, |stack, global| { - stack.access(AccessKind::Read, ptr.tag, global)?; - Ok(()) - }) + self.for_each(ptr, size, |ptr, stack, global| stack.access(AccessKind::Read, ptr, global)) } #[inline(always)] - pub fn memory_written<'tcx>( - &mut self, - ptr: Pointer, - size: Size, - ) -> InterpResult<'tcx> { + pub fn memory_written<'tcx>(&mut self, ptr: Pointer, size: Size) -> InterpResult<'tcx> { trace!("write access with tag {:?}: {:?}, size {}", ptr.tag, ptr.erase_tag(), size.bytes()); - self.for_each(ptr, size, |stack, global| { - stack.access(AccessKind::Write, ptr.tag, global)?; - Ok(()) - }) + self.for_each(ptr, size, |ptr, stack, global| stack.access(AccessKind::Write, ptr, global)) } #[inline(always)] @@ -513,15 +511,13 @@ pub fn memory_deallocated<'tcx>( size: Size, ) -> InterpResult<'tcx> { trace!("deallocation with tag {:?}: {:?}, size {}", ptr.tag, ptr.erase_tag(), size.bytes()); - self.for_each(ptr, size, |stack, global| { - stack.dealloc(ptr.tag, global) - }) + self.for_each(ptr, size, |ptr, stack, global| stack.dealloc(ptr, global)) } } /// Retagging/reborrowing. There is some policy in here, such as which permissions /// to grant for which references, and when to add protectors. -impl<'mir, 'tcx> EvalContextPrivExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {} +impl<'mir, 'tcx: 'mir> EvalContextPrivExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {} trait EvalContextPrivExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> { fn reborrow( &mut self, @@ -532,16 +528,22 @@ fn reborrow( protect: bool, ) -> InterpResult<'tcx> { let this = self.eval_context_mut(); - let protector = if protect { Some(this.frame().extra) } else { None }; - let ptr = this.memory.check_ptr_access(place.ptr, size, place.align) - .expect("validity checks should have excluded dangling/unaligned pointer") - .expect("we shouldn't get here for ZST"); - trace!("reborrow: {} reference {:?} derived from {:?} (pointee {}): {:?}, size {}", - kind, new_tag, ptr.tag, place.layout.ty, ptr.erase_tag(), size.bytes()); + let protector = if protect { Some(this.frame().extra.call_id) } else { None }; + let ptr = place.ptr.assert_ptr(); + trace!( + "reborrow: {} reference {:?} derived from {:?} (pointee {}): {:?}, size {}", + kind, + new_tag, + ptr.tag, + place.layout.ty, + ptr.erase_tag(), + size.bytes() + ); // Get the allocation. It might not be mutable, so we cannot use `get_mut`. - let alloc = this.memory.get(ptr.alloc_id)?; - let stacked_borrows = alloc.extra.stacked_borrows.as_ref().expect("we should have Stacked Borrows data"); + let extra = &this.memory.get_raw(ptr.alloc_id)?.extra; + let stacked_borrows = + extra.stacked_borrows.as_ref().expect("we should have Stacked Borrows data"); // Update the stacks. // Make sure that raw pointers and mutable shared references are reborrowed "weak": // There could be existing unique pointers reborrowed from them that should remain valid! @@ -555,18 +557,20 @@ fn reborrow( // We need a frozen-sensitive reborrow. return this.visit_freeze_sensitive(place, size, |cur_ptr, size, frozen| { // We are only ever `SharedReadOnly` inside the frozen bits. - let perm = if frozen { Permission::SharedReadOnly } else { Permission::SharedReadWrite }; + let perm = if frozen { + Permission::SharedReadOnly + } else { + Permission::SharedReadWrite + }; let item = Item { perm, tag: new_tag, protector }; - stacked_borrows.for_each(cur_ptr, size, |stack, global| { - stack.grant(cur_ptr.tag, item, global) + stacked_borrows.for_each(cur_ptr, size, |cur_ptr, stack, global| { + stack.grant(cur_ptr, item, global) }) }); } }; let item = Item { perm, tag: new_tag, protector }; - stacked_borrows.for_each(ptr, size, |stack, global| { - stack.grant(ptr.tag, item, global) - }) + stacked_borrows.for_each(ptr, size, |ptr, stack, global| stack.grant(ptr, item, global)) } /// Retags an indidual pointer, returning the retagged version. @@ -576,23 +580,33 @@ fn retag_reference( val: ImmTy<'tcx, Tag>, kind: RefKind, protect: bool, - ) -> InterpResult<'tcx, Immediate> { + ) -> InterpResult<'tcx, ImmTy<'tcx, Tag>> { let this = self.eval_context_mut(); // We want a place for where the ptr *points to*, so we get one. let place = this.ref_to_mplace(val)?; - let size = this.size_and_align_of_mplace(place)? + let size = this + .size_and_align_of_mplace(place)? .map(|(size, _)| size) .unwrap_or_else(|| place.layout.size); + // `reborrow` relies on getting a `Pointer` and everything being in-bounds, + // so let's ensure that. However, we do not care about alignment. + // We can see dangling ptrs in here e.g. after a Box's `Unique` was + // updated using "self.0 = ..." (can happen in Box::from_raw) so we cannot ICE; see miri#1050. + let place = this.mplace_access_checked(place, Some(Align::from_bytes(1).unwrap()))?; + // Nothing to do for ZSTs. if size == Size::ZERO { - // Nothing to do for ZSTs. - return Ok(*val); + return Ok(val); } - let place = this.force_mplace_ptr(place)?; // Compute new borrow. - let new_tag = match kind { - RefKind::Raw { .. } => Tag::Untagged, - _ => Tag::Tagged(this.memory.extra.stacked_borrows.borrow_mut().new_ptr()), + let new_tag = { + let mut mem_extra = this.memory.extra.stacked_borrows.as_ref().unwrap().borrow_mut(); + match kind { + // Give up tracking for raw pointers. + RefKind::Raw { .. } if !mem_extra.track_raw => Tag::Untagged, + // All other pointers are properly tracked. + _ => Tag::Tagged(mem_extra.new_ptr()), + } }; // Reborrow. @@ -600,31 +614,29 @@ fn retag_reference( let new_place = place.replace_tag(new_tag); // Return new pointer. - Ok(new_place.to_ref()) + Ok(ImmTy::from_immediate(new_place.to_ref(), val.layout)) } } -impl<'mir, 'tcx> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {} +impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {} pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> { - fn retag( - &mut self, - kind: RetagKind, - place: PlaceTy<'tcx, Tag> - ) -> InterpResult<'tcx> { + fn retag(&mut self, kind: RetagKind, place: PlaceTy<'tcx, Tag>) -> InterpResult<'tcx> { let this = self.eval_context_mut(); // Determine mutability and whether to add a protector. // Cannot use `builtin_deref` because that reports *immutable* for `Box`, // making it useless. fn qualify(ty: ty::Ty<'_>, kind: RetagKind) -> Option<(RefKind, bool)> { - match ty.kind { + match ty.kind() { // References are simple. - ty::Ref(_, _, MutMutable) => - Some((RefKind::Unique { two_phase: kind == RetagKind::TwoPhase}, kind == RetagKind::FnEntry)), - ty::Ref(_, _, MutImmutable) => + ty::Ref(_, _, Mutability::Mut) => Some(( + RefKind::Unique { two_phase: kind == RetagKind::TwoPhase }, + kind == RetagKind::FnEntry, + )), + ty::Ref(_, _, Mutability::Not) => Some((RefKind::Shared, kind == RetagKind::FnEntry)), // Raw pointers need to be enabled. ty::RawPtr(tym) if kind == RetagKind::Raw => - Some((RefKind::Raw { mutable: tym.mutbl == MutMutable }, false)), + Some((RefKind::Raw { mutable: tym.mutbl == Mutability::Mut }, false)), // Boxes do not get a protector: protectors reflect that references outlive the call // they were passed in to; that's just not the case for boxes. ty::Adt(..) if ty.is_box() => Some((RefKind::Unique { two_phase: false }, false)), @@ -639,8 +651,41 @@ fn qualify(ty: ty::Ty<'_>, kind: RetagKind) -> Option<(RefKind, bool)> { // Fast path. let val = this.read_immediate(this.place_to_op(place)?)?; let val = this.retag_reference(val, mutbl, protector)?; - this.write_immediate(val, place)?; + this.write_immediate(*val, place)?; + } + + Ok(()) + } + + /// After a stack frame got pushed, retag the return place so that we are sure + /// it does not alias with anything. + /// + /// This is a HACK because there is nothing in MIR that would make the retag + /// explicit. Also see https://github.com/rust-lang/rust/issues/71117. + fn retag_return_place(&mut self) -> InterpResult<'tcx> { + let this = self.eval_context_mut(); + let return_place = if let Some(return_place) = this.frame_mut().return_place { + return_place + } else { + // No return place, nothing to do. + return Ok(()); + }; + if return_place.layout.is_zst() { + // There may not be any memory here, nothing to do. + return Ok(()); } + // We need this to be in-memory to use tagged pointers. + let return_place = this.force_allocation(return_place)?; + + // We have to turn the place into a pointer to use the existing code. + // (The pointer type does not matter, so we use a raw pointer.) + let ptr_layout = this.layout_of(this.tcx.mk_mut_ptr(return_place.layout.ty))?; + let val = ImmTy::from_immediate(return_place.to_ref(), ptr_layout); + // Reborrow it. + let val = this.retag_reference(val, RefKind::Unique { two_phase: false }, /*protector*/ true)?; + // And use reborrowed pointer for return place. + let return_place = this.ref_to_mplace(val)?; + this.frame_mut().return_place = Some(return_place.into()); Ok(()) }