X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=src%2Fstacked_borrows.rs;h=cfaf8a9005ca50295c30ca1805132585339d5db7;hb=2670839e1af540a496a0d889fce9ad42529ecc11;hp=89b2a8bb3e2b2734d3bc104f225a499160a4029e;hpb=147ea8f400de3ca529abcb5eb7b65f84a4896ae9;p=rust.git diff --git a/src/stacked_borrows.rs b/src/stacked_borrows.rs index 89b2a8bb3e2..cfaf8a9005c 100644 --- a/src/stacked_borrows.rs +++ b/src/stacked_borrows.rs @@ -11,7 +11,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet}; use rustc_middle::mir::RetagKind; use rustc_middle::ty; -use rustc_target::abi::Size; +use rustc_target::abi::{Align, LayoutOf, Size}; use rustc_hir::Mutability; use crate::*; @@ -104,8 +104,12 @@ pub struct GlobalState { next_call_id: CallId, /// Those call IDs corresponding to functions that are still running. active_calls: FxHashSet, - /// The id to trace in this execution run + /// 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>; @@ -153,18 +157,23 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { /// Utilities for initialization and ID generation impl GlobalState { - pub fn new(tracked_pointer_tag: Option) -> Self { + 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: FxHashMap::default(), next_call_id: NonZeroU64::new(1).unwrap(), active_calls: FxHashSet::default(), tracked_pointer_tag, + tracked_call_id, + track_raw, } } 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 @@ -277,7 +289,7 @@ fn find_first_write_incompatible(&self, granting: usize) -> usize { 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::PoppedTrackedPointerTag(item.clone())); + register_diagnostic(NonHaltingDiagnostic::PoppedPointerTag(item.clone())); } } if let Some(call) = item.protector { @@ -300,14 +312,14 @@ 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(|| { + let granting_idx = self.find_granting(access, ptr.tag).ok_or_else(|| { err_sb_ub(format!( - "no item granting {} to tag {:?} found in borrow stack.", - access, tag + "no item granting {} to tag {:?} at {} found in borrow stack.", + access, ptr.tag, ptr.erase_tag(), )) })?; @@ -319,7 +331,7 @@ fn access(&mut self, access: AccessKind, tag: Tag, global: &GlobalState) -> Inte 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. @@ -334,7 +346,7 @@ fn access(&mut self, access: AccessKind, tag: Tag, global: &GlobalState) -> Inte 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; } } @@ -346,12 +358,12 @@ fn access(&mut self, access: AccessKind, tag: Tag, global: &GlobalState) -> Inte /// 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(|| { + self.find_granting(AccessKind::Write, ptr.tag).ok_or_else(|| { err_sb_ub(format!( - "no item granting write access for deallocation to tag {:?} found in borrow stack", - tag, + "no item granting write access for deallocation to tag {:?} at {} found in borrow stack", + ptr.tag, ptr.erase_tag(), )) })?; @@ -363,20 +375,20 @@ fn dealloc(&mut self, tag: Tag, global: &GlobalState) -> InterpResult<'tcx> { 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 }; // 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) + let granting_idx = self.find_granting(access, derived_from.tag) .ok_or_else(|| err_sb_ub(format!( - "trying to reborrow for {:?}, but parent tag {:?} does not have an appropriate item in the borrow stack", - new.perm, derived_from, + "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. @@ -434,12 +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(()) } @@ -460,17 +474,20 @@ pub fn new_allocation( // 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`. + // `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. - // `Machine` is used for extern statics, and thus must also be listed 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::Machine | MiriMemoryKind::Env) => + MemoryKind::Machine(MiriMemoryKind::Global | MiriMemoryKind::ExternStatic | MiriMemoryKind::Tls | MiriMemoryKind::Env) => (extra.borrow_mut().global_base_ptr(id), Permission::SharedReadWrite), - // Everything else we handle entirely untagged for now. - // FIXME: experiment with more precise tracking. - _ => (Tag::Untagged, 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) + } }; (Stacks::new(size, perm, tag, extra), tag) } @@ -478,19 +495,13 @@ pub fn new_allocation( #[inline(always)] 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> { 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)] @@ -500,17 +511,17 @@ 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, - place: MPlaceTy<'tcx, Tag>, + place: &MPlaceTy<'tcx, Tag>, size: Size, kind: RefKind, new_tag: Tag, @@ -552,70 +563,78 @@ fn reborrow( 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. /// `mutbl` can be `None` to make this a raw pointer. fn retag_reference( &mut self, - val: ImmTy<'tcx, Tag>, + 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)? - .map(|(size, _)| size) - .unwrap_or_else(|| place.layout.size); + .size_and_align_of_mplace(&place)? + .map(|(size, _)| size); + // FIXME: If we cannot determine the size (because the unsized tail is an `extern type`), + // bail out -- we cannot reasonably figure out which memory range to reborrow. + // See https://github.com/rust-lang/unsafe-code-guidelines/issues/276. + let size = match size { + Some(size) => size, + None => return Ok(*val), + }; + // `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); see miri#1050. - let place = this.mplace_access_checked(place)?; - if size == Size::ZERO { - // Nothing to do for ZSTs. + // 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. We use `is_bits` here because we *do* need to retag even ZSTs + // when there actually is a tag (to avoid inheriting a tag that would let us access more + // than 0 bytes). + if size == Size::ZERO && place.ptr.is_bits() { return Ok(*val); } // Compute new borrow. - let new_tag = match kind { - // Give up tracking for raw pointers. - // FIXME: Experiment with more precise tracking. Blocked on `&raw` - // because `Rc::into_raw` currently creates intermediate references, - // breaking `Rc::from_raw`. - RefKind::Raw { .. } => Tag::Untagged, - // All other pointesr are properly tracked. - _ => Tag::Tagged( - this.memory.extra.stacked_borrows.as_ref().unwrap().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. - this.reborrow(place, size, kind, new_tag, protect)?; + this.reborrow(&place, size, kind, new_tag, protect)?; 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(_, _, Mutability::Mut) => Some(( RefKind::Unique { two_phase: kind == RetagKind::TwoPhase }, @@ -638,10 +657,43 @@ fn qualify(ty: ty::Ty<'_>, kind: RetagKind) -> Option<(RefKind, bool)> { // but might also cost us optimization and analyses. We will have to experiment more with this. if let Some((mutbl, protector)) = qualify(place.layout.ty, kind) { // 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)?; + let val = this.read_immediate(&this.place_to_op(place)?)?; + let val = this.retag_reference(&val, mutbl, protector)?; + 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(()) }