From 3fa692c8b22cfcd4d13e0568056b680235d0cef0 Mon Sep 17 00:00:00 2001 From: Ralf Jung Date: Sat, 3 Dec 2022 19:05:46 +0100 Subject: [PATCH] for now, do not do fake reads on non-Unpin mutable references --- .../src/borrow_tracker/stacked_borrows/mod.rs | 23 +++++++++------ .../notunpin_dereferenceable_fakeread.rs | 17 ----------- .../notunpin_dereferenceable_fakeread.stderr | 28 ------------------- 3 files changed, 14 insertions(+), 54 deletions(-) delete mode 100644 src/tools/miri/tests/fail/stacked_borrows/notunpin_dereferenceable_fakeread.rs delete mode 100644 src/tools/miri/tests/fail/stacked_borrows/notunpin_dereferenceable_fakeread.stderr diff --git a/src/tools/miri/src/borrow_tracker/stacked_borrows/mod.rs b/src/tools/miri/src/borrow_tracker/stacked_borrows/mod.rs index 50c2ad75ca7..bcac873251f 100644 --- a/src/tools/miri/src/borrow_tracker/stacked_borrows/mod.rs +++ b/src/tools/miri/src/borrow_tracker/stacked_borrows/mod.rs @@ -45,7 +45,9 @@ pub struct Stacks { /// new pointer. #[derive(Copy, Clone, Hash, PartialEq, Eq)] enum RefKind { - /// `&mut` and `Box`. + /// `Box`. + Box, + /// `&mut`. Unique { two_phase: bool }, /// `&` with or without interior mutability. Shared, @@ -56,6 +58,7 @@ enum RefKind { impl fmt::Display for RefKind { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { match self { + RefKind::Box => write!(f, "Box"), RefKind::Unique { two_phase: false } => write!(f, "unique reference"), RefKind::Unique { two_phase: true } => write!(f, "unique reference (two-phase)"), RefKind::Shared => write!(f, "shared reference"), @@ -654,15 +657,17 @@ trait EvalContextPrivExt<'mir: 'ecx, 'tcx: 'mir, 'ecx>: crate::MiriInterpCxExt<' let (perm, access) = match kind { RefKind::Unique { two_phase } => { // Permission is Unique only if the type is `Unpin` and this is not twophase - let perm = if !two_phase && place.layout.ty.is_unpin(*this.tcx, this.param_env()) { - Permission::Unique + if !two_phase && place.layout.ty.is_unpin(*this.tcx, this.param_env()) { + (Permission::Unique, Some(AccessKind::Write)) } else { - Permission::SharedReadWrite - }; - // We do an access for all full borrows, even if `!Unpin`. - let access = if !two_phase { Some(AccessKind::Write) } else { None }; - (perm, access) + // FIXME: We emit `dereferenceable` for `!Unpin` mutable references, so we + // should do fake accesses here. But then we run into + // , so for now + // we don't do that. + (Permission::SharedReadWrite, None) + } } + RefKind::Box => (Permission::Unique, Some(AccessKind::Write)), RefKind::Raw { mutable: true } => { // Creating a raw ptr does not count as an access (Permission::SharedReadWrite, None) @@ -853,7 +858,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> { // Boxes get a weak protectors, since they may be deallocated. self.retag_place( place, - RefKind::Unique { two_phase: false }, + RefKind::Box, self.retag_cause, /*protector*/ (self.kind == RetagKind::FnEntry).then_some(ProtectorKind::WeakProtector), diff --git a/src/tools/miri/tests/fail/stacked_borrows/notunpin_dereferenceable_fakeread.rs b/src/tools/miri/tests/fail/stacked_borrows/notunpin_dereferenceable_fakeread.rs deleted file mode 100644 index d660921bfe6..00000000000 --- a/src/tools/miri/tests/fail/stacked_borrows/notunpin_dereferenceable_fakeread.rs +++ /dev/null @@ -1,17 +0,0 @@ -//! Reborrowing a `&mut !Unpin` must still act like a (fake) read. -use std::marker::PhantomPinned; - -struct NotUnpin(i32, PhantomPinned); - -fn main() { - unsafe { - let mut x = NotUnpin(0, PhantomPinned); - // Mutable borrow of `Unpin` field (with lifetime laundering) - let fieldref = &mut *(&mut x.0 as *mut i32); - // Mutable reborrow of the entire `x`, which is `!Unpin` but should - // still count as a read since we would add `dereferenceable`. - let _xref = &mut x; - // That read should have invalidated `fieldref`. - *fieldref = 0; //~ ERROR: /write access .* tag does not exist in the borrow stack/ - } -} diff --git a/src/tools/miri/tests/fail/stacked_borrows/notunpin_dereferenceable_fakeread.stderr b/src/tools/miri/tests/fail/stacked_borrows/notunpin_dereferenceable_fakeread.stderr deleted file mode 100644 index 3ef8a8e0e9c..00000000000 --- a/src/tools/miri/tests/fail/stacked_borrows/notunpin_dereferenceable_fakeread.stderr +++ /dev/null @@ -1,28 +0,0 @@ -error: Undefined Behavior: attempting a write access using at ALLOC[0x0], but that tag does not exist in the borrow stack for this location - --> $DIR/notunpin_dereferenceable_fakeread.rs:LL:CC - | -LL | *fieldref = 0; - | ^^^^^^^^^^^^^ - | | - | attempting a write access using at ALLOC[0x0], but that tag does not exist in the borrow stack for this location - | this error occurs as part of an access at ALLOC[0x0..0x4] - | - = help: this indicates a potential bug in the program: it performed an invalid operation, but the Stacked Borrows rules it violated are still experimental - = help: see https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/stacked-borrows.md for further information -help: was created by a Unique retag at offsets [0x0..0x4] - --> $DIR/notunpin_dereferenceable_fakeread.rs:LL:CC - | -LL | let fieldref = &mut *(&mut x.0 as *mut i32); - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -help: was later invalidated at offsets [0x0..0x4] by a SharedReadWrite retag - --> $DIR/notunpin_dereferenceable_fakeread.rs:LL:CC - | -LL | let _xref = &mut x; - | ^^^^^^ - = note: BACKTRACE: - = note: inside `main` at $DIR/notunpin_dereferenceable_fakeread.rs:LL:CC - -note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace - -error: aborting due to previous error -