X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=src%2Fstacked_borrows.rs;h=616950eb0a0a44a5ca923ae78a7a68c3c2c6e9e3;hb=69fb6413ddc5b7fd5d9cb0a68ebf58ee513bf9d5;hp=ace4fef3ce3b4dfcd9c79b712e450723f68b1357;hpb=aec175e0deb39d35a9b5c0f329141c4b22930e01;p=rust.git diff --git a/src/stacked_borrows.rs b/src/stacked_borrows.rs index ace4fef3ce3..616950eb0a0 100644 --- a/src/stacked_borrows.rs +++ b/src/stacked_borrows.rs @@ -2,16 +2,17 @@ //! for further information. use std::cell::RefCell; -use std::collections::{HashMap, HashSet}; use std::fmt; -use std::fmt::Write; use std::num::NonZeroU64; use std::rc::Rc; +use log::trace; + +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 rustc::mir::RetagKind; -use rustc::ty::{self, layout::Size}; -use rustc_mir::interpret::InterpError; use crate::*; @@ -98,13 +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, - /// The id to trace in this execution run + 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>; @@ -152,18 +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: 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, } } 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 } @@ -171,6 +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 @@ -184,7 +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); @@ -194,6 +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: @@ -268,29 +289,21 @@ 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_err( - InterpError::MachineStop(Box::new(TerminationInfo::PoppedTrackedPointerTag( - item.clone(), - ))) - .into(), - ); + register_diagnostic(NonHaltingDiagnostic::PoppedPointerTag(item.clone())); } } if let Some(call) = item.protector { if global.is_active(call) { if let Some(tag) = tag { - return Err(err_ub_experimental( - tag, - format!( - "not granting access to tag {:?} because incompatible item is protected: {:?}", - tag, item - ), - )); + Err(err_sb_ub(format!( + "not granting access to tag {:?} because incompatible item is protected: {:?}", + tag, item + )))? } else { - throw_ub!(UbExperimental(format!( + Err(err_sb_ub(format!( "deallocating while item is protected: {:?}", item - ))); + )))? } } } @@ -299,15 +312,15 @@ 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_experimental( - tag, - 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 @@ -318,7 +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. @@ -333,7 +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; } } @@ -345,13 +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(|| { - err_ub_experimental( - tag,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(), )) })?; @@ -363,25 +375,21 @@ 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) - .ok_or_else(|| - err_ub_experimental( - derived_from, - 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 @@ -438,12 +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(()) } @@ -464,15 +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), - // Static memory can be referenced by "global" pointers from `tcx`. - // Thus we call `static_base_ptr` such that the global pointers get the same tag + // `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::Static) => - (extra.borrow_mut().static_base_ptr(id), Permission::SharedReadWrite), - // Everything else we handle entirely untagged for now. - // FIXME: experiment with more precise tracking. - _ => (Tag::Untagged, Permission::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) + } }; (Stacks::new(size, perm, tag, extra), tag) } @@ -480,19 +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)] @@ -502,13 +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, @@ -554,14 +563,14 @@ 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. @@ -571,7 +580,7 @@ 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)?; @@ -579,23 +588,25 @@ fn retag_reference( .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); see miri#1050. - let place = this.mplace_access_checked(place)?; + // 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); } // 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.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. @@ -603,11 +614,11 @@ 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> { let this = self.eval_context_mut(); @@ -615,7 +626,7 @@ fn retag(&mut self, kind: RetagKind, place: PlaceTy<'tcx, Tag>) -> InterpResult< // 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 }, @@ -640,17 +651,42 @@ 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(()) } -} -fn err_ub_experimental(tag: Tag, mut msg: String) -> InterpErrorInfo<'static> { - if let Tag::Tagged(id) = tag { - // FIXME: do not add this message when the flag is already set - write!(msg, " Rerun with `-Zmiri-track-pointer-tag={}` for more information", id).unwrap(); + /// 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(()) } - err_ub!(UbExperimental(msg)).into() }