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Auto merge of #75592 - RalfJung:miri-int-align, r=oli-obk

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miri engine: add option to use force_int for alignment check

This is needed for https://github.com/rust-lang/miri/issues/1074. The Miri-side patch is at https://github.com/rust-lang/miri/pull/1513.

r? @oli-obk
This commit is contained in:
bors 2020-08-17 12:11:41 +00:00
commit 8cdc94e840
2 changed files with 23 additions and 10 deletions
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10
src/librustc_mir/interpret/machine.rs
View file

@ -122,6 +122,10 @@ pub trait Machine<'mir, 'tcx>: Sized {
/// Whether memory accesses should be alignment-checked.
fn enforce_alignment(memory_extra: &Self::MemoryExtra) -> bool;
/// Whether, when checking alignment, we should `force_int` and thus support
/// custom alignment logic based on whatever the integer address happens to be.
fn force_int_for_alignment_check(memory_extra: &Self::MemoryExtra) -> bool;
/// Whether to enforce the validity invariant
fn enforce_validity(ecx: &InterpCx<'mir, 'tcx, Self>) -> bool;
@ -375,6 +379,12 @@ pub macro compile_time_machine(<$mir: lifetime, $tcx: lifetime>) {
false
}
#[inline(always)]
fn force_int_for_alignment_check(_memory_extra: &Self::MemoryExtra) -> bool {
// We do not support `force_int`.
false
}
#[inline(always)]
fn enforce_validity(_ecx: &InterpCx<$mir, $tcx, Self>) -> bool {
false // for now, we don't enforce validity

23
src/librustc_mir/interpret/memory.rs
View file

@ -8,7 +8,7 @@
use std::borrow::Cow;
use std::collections::VecDeque;
use std::convert::TryFrom;
use std::convert::{TryFrom, TryInto};
use std::fmt;
use std::ptr;
@ -380,7 +380,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
// if this is already a `Pointer` we want to do the bounds checks!
sptr
} else {
// A "real" access, we must get a pointer.
// A "real" access, we must get a pointer to be able to check the bounds.
Scalar::from(self.force_ptr(sptr)?)
};
Ok(match normalized.to_bits_or_ptr(self.pointer_size(), self) {
@ -411,15 +411,18 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
// Test align. Check this last; if both bounds and alignment are violated
// we want the error to be about the bounds.
if let Some(align) = align {
if alloc_align.bytes() < align.bytes() {
// The allocation itself is not aligned enough.
// FIXME: Alignment check is too strict, depending on the base address that
// got picked we might be aligned even if this check fails.
// We instead have to fall back to converting to an integer and checking
// the "real" alignment.
throw_ub!(AlignmentCheckFailed { has: alloc_align, required: align });
if M::force_int_for_alignment_check(&self.extra) {
let bits = self
.force_bits(ptr.into(), self.pointer_size())
.expect("ptr-to-int cast for align check should never fail");
check_offset_align(bits.try_into().unwrap(), align)?;
} else {
// Check allocation alignment and offset alignment.
if alloc_align.bytes() < align.bytes() {
throw_ub!(AlignmentCheckFailed { has: alloc_align, required: align });
}
check_offset_align(ptr.offset.bytes(), align)?;
}
check_offset_align(ptr.offset.bytes(), align)?;
}
// We can still be zero-sized in this branch, in which case we have to