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Auto merge of #104054 - RalfJung:byte-provenance, r=oli-obk

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interpret: support for per-byte provenance

Also factors the provenance map into its own module.

The third commit does the same for the init mask. I can move it in a separate PR if you prefer.

Fixes https://github.com/rust-lang/miri/issues/2181

r? `@oli-obk`
This commit is contained in:
bors 2022-11-15 17:37:15 +00:00
commit a00f8ba7fc
30 changed files with 1253 additions and 959 deletions
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4
compiler/rustc_codegen_cranelift/src/constant.rs
View File

@ -398,7 +398,7 @@ fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut Constant
let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(0..alloc.len()).to_vec();
data_ctx.define(bytes.into_boxed_slice());
for &(offset, alloc_id) in alloc.provenance().iter() {
for &(offset, alloc_id) in alloc.provenance().ptrs().iter() {
let addend = {
let endianness = tcx.data_layout.endian;
let offset = offset.bytes() as usize;
@ -431,7 +431,7 @@ fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut Constant
{
tcx.sess.fatal(&format!(
"Allocation {:?} contains reference to TLS value {:?}",
alloc, def_id
alloc_id, def_id
));
}

4
compiler/rustc_codegen_gcc/src/consts.rs
View File

@ -297,12 +297,12 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
pub fn const_alloc_to_gcc<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, alloc: ConstAllocation<'tcx>) -> RValue<'gcc> {
let alloc = alloc.inner();
let mut llvals = Vec::with_capacity(alloc.provenance().len() + 1);
let mut llvals = Vec::with_capacity(alloc.provenance().ptrs().len() + 1);
let dl = cx.data_layout();
let pointer_size = dl.pointer_size.bytes() as usize;
let mut next_offset = 0;
for &(offset, alloc_id) in alloc.provenance().iter() {
for &(offset, alloc_id) in alloc.provenance().ptrs().iter() {
let offset = offset.bytes();
assert_eq!(offset as usize as u64, offset);
let offset = offset as usize;

12
compiler/rustc_codegen_llvm/src/consts.rs
View File

@ -28,7 +28,7 @@ use std::ops::Range;
pub fn const_alloc_to_llvm<'ll>(cx: &CodegenCx<'ll, '_>, alloc: ConstAllocation<'_>) -> &'ll Value {
let alloc = alloc.inner();
let mut llvals = Vec::with_capacity(alloc.provenance().len() + 1);
let mut llvals = Vec::with_capacity(alloc.provenance().ptrs().len() + 1);
let dl = cx.data_layout();
let pointer_size = dl.pointer_size.bytes() as usize;
@ -40,9 +40,7 @@ pub fn const_alloc_to_llvm<'ll>(cx: &CodegenCx<'ll, '_>, alloc: ConstAllocation<
alloc: &'a Allocation,
range: Range<usize>,
) {
let chunks = alloc
.init_mask()
.range_as_init_chunks(Size::from_bytes(range.start), Size::from_bytes(range.end));
let chunks = alloc.init_mask().range_as_init_chunks(range.clone().into());
let chunk_to_llval = move |chunk| match chunk {
InitChunk::Init(range) => {
@ -80,7 +78,7 @@ pub fn const_alloc_to_llvm<'ll>(cx: &CodegenCx<'ll, '_>, alloc: ConstAllocation<
}
let mut next_offset = 0;
for &(offset, alloc_id) in alloc.provenance().iter() {
for &(offset, alloc_id) in alloc.provenance().ptrs().iter() {
let offset = offset.bytes();
assert_eq!(offset as usize as u64, offset);
let offset = offset as usize;
@ -489,7 +487,7 @@ impl<'ll> StaticMethods for CodegenCx<'ll, '_> {
// happens to be zero. Instead, we should only check the value of defined bytes
// and set all undefined bytes to zero if this allocation is headed for the
// BSS.
let all_bytes_are_zero = alloc.provenance().is_empty()
let all_bytes_are_zero = alloc.provenance().ptrs().is_empty()
&& alloc
.inspect_with_uninit_and_ptr_outside_interpreter(0..alloc.len())
.iter()
@ -513,7 +511,7 @@ impl<'ll> StaticMethods for CodegenCx<'ll, '_> {
section.as_str().as_ptr().cast(),
section.as_str().len() as c_uint,
);
assert!(alloc.provenance().is_empty());
assert!(alloc.provenance().ptrs().is_empty());
// The `inspect` method is okay here because we checked for provenance, and
// because we are doing this access to inspect the final interpreter state (not

4
compiler/rustc_const_eval/src/interpret/intern.rs
View File

@ -134,7 +134,7 @@ fn intern_shallow<'rt, 'mir, 'tcx, M: CompileTimeMachine<'mir, 'tcx, const_eval:
alloc.mutability = Mutability::Not;
};
// link the alloc id to the actual allocation
leftover_allocations.extend(alloc.provenance().iter().map(|&(_, alloc_id)| alloc_id));
leftover_allocations.extend(alloc.provenance().ptrs().iter().map(|&(_, alloc_id)| alloc_id));
let alloc = tcx.intern_const_alloc(alloc);
tcx.set_alloc_id_memory(alloc_id, alloc);
None
@ -439,7 +439,7 @@ pub fn intern_const_alloc_recursive<
}
let alloc = tcx.intern_const_alloc(alloc);
tcx.set_alloc_id_memory(alloc_id, alloc);
for &(_, alloc_id) in alloc.inner().provenance().iter() {
for &(_, alloc_id) in alloc.inner().provenance().ptrs().iter() {
if leftover_allocations.insert(alloc_id) {
todo.push(alloc_id);
}

41
compiler/rustc_const_eval/src/interpret/memory.rs
View File

@ -112,7 +112,7 @@ pub struct Memory<'mir, 'tcx, M: Machine<'mir, 'tcx>> {
/// A reference to some allocation that was already bounds-checked for the given region
/// and had the on-access machine hooks run.
#[derive(Copy, Clone)]
pub struct AllocRef<'a, 'tcx, Prov, Extra> {
pub struct AllocRef<'a, 'tcx, Prov: Provenance, Extra> {
alloc: &'a Allocation<Prov, Extra>,
range: AllocRange,
tcx: TyCtxt<'tcx>,
@ -120,7 +120,7 @@ pub struct AllocRef<'a, 'tcx, Prov, Extra> {
}
/// A reference to some allocation that was already bounds-checked for the given region
/// and had the on-access machine hooks run.
pub struct AllocRefMut<'a, 'tcx, Prov, Extra> {
pub struct AllocRefMut<'a, 'tcx, Prov: Provenance, Extra> {
alloc: &'a mut Allocation<Prov, Extra>,
range: AllocRange,
tcx: TyCtxt<'tcx>,
@ -302,8 +302,6 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
.into());
};
debug!(?alloc);
if alloc.mutability == Mutability::Not {
throw_ub_format!("deallocating immutable allocation {alloc_id:?}");
}
@ -797,7 +795,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
// This is a new allocation, add the allocation it points to `todo`.
if let Some((_, alloc)) = self.memory.alloc_map.get(id) {
todo.extend(
alloc.provenance().values().filter_map(|prov| prov.get_alloc_id()),
alloc.provenance().provenances().filter_map(|prov| prov.get_alloc_id()),
);
}
}
@ -833,7 +831,8 @@ impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> std::fmt::Debug for DumpAllocs<'a,
allocs_to_print: &mut VecDeque<AllocId>,
alloc: &Allocation<Prov, Extra>,
) -> std::fmt::Result {
for alloc_id in alloc.provenance().values().filter_map(|prov| prov.get_alloc_id()) {
for alloc_id in alloc.provenance().provenances().filter_map(|prov| prov.get_alloc_id())
{
allocs_to_print.push_back(alloc_id);
}
write!(fmt, "{}", display_allocation(tcx, alloc))
@ -962,7 +961,7 @@ impl<'tcx, 'a, Prov: Provenance, Extra> AllocRef<'a, 'tcx, Prov, Extra> {
/// Returns whether the allocation has provenance anywhere in the range of the `AllocRef`.
pub(crate) fn has_provenance(&self) -> bool {
self.alloc.range_has_provenance(&self.tcx, self.range)
!self.alloc.provenance().range_empty(self.range, &self.tcx)
}
}
@ -1060,7 +1059,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
// Source alloc preparations and access hooks.
let Some((src_alloc_id, src_offset, src_prov)) = src_parts else {
// Zero-sized *source*, that means dst is also zero-sized and we have nothing to do.
// Zero-sized *source*, that means dest is also zero-sized and we have nothing to do.
return Ok(());
};
let src_alloc = self.get_alloc_raw(src_alloc_id)?;
@ -1079,22 +1078,18 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
return Ok(());
};
// Checks provenance edges on the src, which needs to happen before
// `prepare_provenance_copy`.
if src_alloc.range_has_provenance(&tcx, alloc_range(src_range.start, Size::ZERO)) {
throw_unsup!(PartialPointerCopy(Pointer::new(src_alloc_id, src_range.start)));
}
if src_alloc.range_has_provenance(&tcx, alloc_range(src_range.end(), Size::ZERO)) {
throw_unsup!(PartialPointerCopy(Pointer::new(src_alloc_id, src_range.end())));
}
// Prepare getting source provenance.
let src_bytes = src_alloc.get_bytes_unchecked(src_range).as_ptr(); // raw ptr, so we can also get a ptr to the destination allocation
// first copy the provenance to a temporary buffer, because
// `get_bytes_mut` will clear the provenance, which is correct,
// since we don't want to keep any provenance at the target.
let provenance =
src_alloc.prepare_provenance_copy(self, src_range, dest_offset, num_copies);
// This will also error if copying partial provenance is not supported.
let provenance = src_alloc
.provenance()
.prepare_copy(src_range, dest_offset, num_copies, self)
.map_err(|e| e.to_interp_error(dest_alloc_id))?;
// Prepare a copy of the initialization mask.
let compressed = src_alloc.compress_uninit_range(src_range);
let init = src_alloc.init_mask().prepare_copy(src_range);
// Destination alloc preparations and access hooks.
let (dest_alloc, extra) = self.get_alloc_raw_mut(dest_alloc_id)?;
@ -1111,7 +1106,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
.map_err(|e| e.to_interp_error(dest_alloc_id))?
.as_mut_ptr();
if compressed.no_bytes_init() {
if init.no_bytes_init() {
// Fast path: If all bytes are `uninit` then there is nothing to copy. The target range
// is marked as uninitialized but we otherwise omit changing the byte representation which may
// be arbitrary for uninitialized bytes.
@ -1160,13 +1155,13 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
}
// now fill in all the "init" data
dest_alloc.mark_compressed_init_range(
&compressed,
dest_alloc.init_mask_apply_copy(
init,
alloc_range(dest_offset, size), // just a single copy (i.e., not full `dest_range`)
num_copies,
);
// copy the provenance to the destination
dest_alloc.mark_provenance_range(provenance);
dest_alloc.provenance_apply_copy(provenance);
Ok(())
}

2
compiler/rustc_hir_analysis/src/check/mod.rs
View File

@ -159,7 +159,7 @@ fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: LocalDefId) {
// the consumer's responsibility to ensure all bytes that have been read
// have defined values.
if let Ok(alloc) = tcx.eval_static_initializer(id.to_def_id())
&& alloc.inner().provenance().len() != 0
&& alloc.inner().provenance().ptrs().len() != 0
{
let msg = "statics with a custom `#[link_section]` must be a \
simple list of bytes on the wasm target with no \

837
compiler/rustc_middle/src/mir/interpret/allocation.rs
View File

@ -1,16 +1,18 @@
//! The virtual memory representation of the MIR interpreter.
mod init_mask;
mod provenance_map;
#[cfg(test)]
mod tests;
use std::borrow::Cow;
use std::convert::{TryFrom, TryInto};
use std::fmt;
use std::hash;
use std::iter;
use std::ops::{Deref, Range};
use std::ops::Range;
use std::ptr;
use rustc_ast::Mutability;
use rustc_data_structures::intern::Interned;
use rustc_data_structures::sorted_map::SortedMap;
use rustc_span::DUMMY_SP;
use rustc_target::abi::{Align, HasDataLayout, Size};
@ -20,6 +22,10 @@ use super::{
UnsupportedOpInfo,
};
use crate::ty;
use init_mask::*;
use provenance_map::*;
pub use init_mask::{InitChunk, InitChunkIter};
/// This type represents an Allocation in the Miri/CTFE core engine.
///
@ -28,9 +34,9 @@ use crate::ty;
/// module provides higher-level access.
// Note: for performance reasons when interning, some of the `Allocation` fields can be partially
// hashed. (see the `Hash` impl below for more details), so the impl is not derived.
#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, TyEncodable, TyDecodable)]
#[derive(Clone, Eq, PartialEq, PartialOrd, Ord, TyEncodable, TyDecodable)]
#[derive(HashStable)]
pub struct Allocation<Prov = AllocId, Extra = ()> {
pub struct Allocation<Prov: Provenance = AllocId, Extra = ()> {
/// The actual bytes of the allocation.
/// Note that the bytes of a pointer represent the offset of the pointer.
bytes: Box<[u8]>,
@ -102,20 +108,18 @@ impl hash::Hash for Allocation {
/// (`ConstAllocation`) are used quite a bit.
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, HashStable)]
#[rustc_pass_by_value]
pub struct ConstAllocation<'tcx, Prov = AllocId, Extra = ()>(
pub Interned<'tcx, Allocation<Prov, Extra>>,
);
pub struct ConstAllocation<'tcx>(pub Interned<'tcx, Allocation>);
impl<'tcx> fmt::Debug for ConstAllocation<'tcx> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
// This matches how `Allocation` is printed. We print it like this to
// avoid having to update expected output in a lot of tests.
write!(f, "{:?}", self.inner())
// The debug representation of this is very verbose and basically useless,
// so don't print it.
write!(f, "ConstAllocation {{ .. }}")
}
}
impl<'tcx, Prov, Extra> ConstAllocation<'tcx, Prov, Extra> {
pub fn inner(self) -> &'tcx Allocation<Prov, Extra> {
impl<'tcx> ConstAllocation<'tcx> {
pub fn inner(self) -> &'tcx Allocation {
self.0.0
}
}
@ -183,12 +187,21 @@ pub fn alloc_range(start: Size, size: Size) -> AllocRange {
AllocRange { start, size }
}
impl AllocRange {
impl From<Range<Size>> for AllocRange {
#[inline]
pub fn from(r: Range<Size>) -> Self {
fn from(r: Range<Size>) -> Self {
alloc_range(r.start, r.end - r.start) // `Size` subtraction (overflow-checked)
}
}
impl From<Range<usize>> for AllocRange {
#[inline]
fn from(r: Range<usize>) -> Self {
AllocRange::from(Size::from_bytes(r.start)..Size::from_bytes(r.end))
}
}
impl AllocRange {
#[inline(always)]
pub fn end(self) -> Size {
self.start + self.size // This does overflow checking.
@ -205,7 +218,7 @@ impl AllocRange {
}
// The constructors are all without extra; the extra gets added by a machine hook later.
impl<Prov> Allocation<Prov> {
impl<Prov: Provenance> Allocation<Prov> {
/// Creates an allocation initialized by the given bytes
pub fn from_bytes<'a>(
slice: impl Into<Cow<'a, [u8]>>,
@ -263,7 +276,7 @@ impl<Prov> Allocation<Prov> {
impl Allocation {
/// Adjust allocation from the ones in tcx to a custom Machine instance
/// with a different Provenance and Extra type.
pub fn adjust_from_tcx<Prov, Extra, Err>(
pub fn adjust_from_tcx<Prov: Provenance, Extra, Err>(
self,
cx: &impl HasDataLayout,
extra: Extra,
@ -271,10 +284,10 @@ impl Allocation {
) -> Result<Allocation<Prov, Extra>, Err> {
// Compute new pointer provenance, which also adjusts the bytes.
let mut bytes = self.bytes;
let mut new_provenance = Vec::with_capacity(self.provenance.0.len());
let mut new_provenance = Vec::with_capacity(self.provenance.ptrs().len());
let ptr_size = cx.data_layout().pointer_size.bytes_usize();
let endian = cx.data_layout().endian;
for &(offset, alloc_id) in self.provenance.iter() {
for &(offset, alloc_id) in self.provenance.ptrs().iter() {
let idx = offset.bytes_usize();
let ptr_bytes = &mut bytes[idx..idx + ptr_size];
let bits = read_target_uint(endian, ptr_bytes).unwrap();
@ -286,7 +299,7 @@ impl Allocation {
// Create allocation.
Ok(Allocation {
bytes,
provenance: ProvenanceMap::from_presorted(new_provenance),
provenance: ProvenanceMap::from_presorted_ptrs(new_provenance),
init_mask: self.init_mask,
align: self.align,
mutability: self.mutability,
@ -296,7 +309,7 @@ impl Allocation {
}
/// Raw accessors. Provide access to otherwise private bytes.
impl<Prov, Extra> Allocation<Prov, Extra> {
impl<Prov: Provenance, Extra> Allocation<Prov, Extra> {
pub fn len(&self) -> usize {
self.bytes.len()
}
@ -349,9 +362,14 @@ impl<Prov: Provenance, Extra> Allocation<Prov, Extra> {
cx: &impl HasDataLayout,
range: AllocRange,
) -> AllocResult<&[u8]> {
self.check_init(range)?;
self.init_mask.is_range_initialized(range).map_err(|uninit_range| {
AllocError::InvalidUninitBytes(Some(UninitBytesAccess {
access: range,
uninit: uninit_range,
}))
})?;
if !Prov::OFFSET_IS_ADDR {
if self.range_has_provenance(cx, range) {
if !self.provenance.range_empty(range, cx) {
return Err(AllocError::ReadPointerAsBytes);
}
}
@ -370,7 +388,7 @@ impl<Prov: Provenance, Extra> Allocation<Prov, Extra> {
range: AllocRange,
) -> AllocResult<&mut [u8]> {
self.mark_init(range, true);
self.clear_provenance(cx, range)?;
self.provenance.clear(range, cx)?;
Ok(&mut self.bytes[range.start.bytes_usize()..range.end().bytes_usize()])
}
@ -382,7 +400,7 @@ impl<Prov: Provenance, Extra> Allocation<Prov, Extra> {
range: AllocRange,
) -> AllocResult<*mut [u8]> {
self.mark_init(range, true);
self.clear_provenance(cx, range)?;
self.provenance.clear(range, cx)?;
assert!(range.end().bytes_usize() <= self.bytes.len()); // need to do our own bounds-check
let begin_ptr = self.bytes.as_mut_ptr().wrapping_add(range.start.bytes_usize());
@ -393,6 +411,15 @@ impl<Prov: Provenance, Extra> Allocation<Prov, Extra> {
/// Reading and writing.
impl<Prov: Provenance, Extra> Allocation<Prov, Extra> {
/// Sets the init bit for the given range.
fn mark_init(&mut self, range: AllocRange, is_init: bool) {
if range.size.bytes() == 0 {
return;
}
assert!(self.mutability == Mutability::Mut);
self.init_mask.set_range(range, is_init);
}
/// Reads a *non-ZST* scalar.
///
/// If `read_provenance` is `true`, this will also read provenance; otherwise (if the machine
@ -410,7 +437,7 @@ impl<Prov: Provenance, Extra> Allocation<Prov, Extra> {
read_provenance: bool,
) -> AllocResult<Scalar<Prov>> {
// First and foremost, if anything is uninit, bail.
if self.is_init(range).is_err() {
if self.init_mask.is_range_initialized(range).is_err() {
return Err(AllocError::InvalidUninitBytes(None));
}
@ -423,7 +450,7 @@ impl<Prov: Provenance, Extra> Allocation<Prov, Extra> {
// When reading data with provenance, the easy case is finding provenance exactly where we
// are reading, then we can put data and provenance back together and return that.
if let Some(&prov) = self.provenance.get(&range.start) {
if let Some(prov) = self.provenance.get_ptr(range.start) {
// Now we can return the bits, with their appropriate provenance.
let ptr = Pointer::new(prov, Size::from_bytes(bits));
return Ok(Scalar::from_pointer(ptr, cx));
@ -431,10 +458,9 @@ impl<Prov: Provenance, Extra> Allocation<Prov, Extra> {
// If we can work on pointers byte-wise, join the byte-wise provenances.
if Prov::OFFSET_IS_ADDR {
let mut prov = self.offset_get_provenance(cx, range.start);
for offset in 1..range.size.bytes() {
let this_prov =
self.offset_get_provenance(cx, range.start + Size::from_bytes(offset));
let mut prov = self.provenance.get(range.start, cx);
for offset in Size::from_bytes(1)..range.size {
let this_prov = self.provenance.get(range.start + offset, cx);
prov = Prov::join(prov, this_prov);
}
// Now use this provenance.
@ -452,7 +478,7 @@ impl<Prov: Provenance, Extra> Allocation<Prov, Extra> {
// Fallback path for when we cannot treat provenance bytewise or ignore it.
assert!(!Prov::OFFSET_IS_ADDR);
if self.range_has_provenance(cx, range) {
if !self.provenance.range_empty(range, cx) {
return Err(AllocError::ReadPointerAsBytes);
}
// There is no provenance, we can just return the bits.
@ -466,7 +492,6 @@ impl<Prov: Provenance, Extra> Allocation<Prov, Extra> {
///
/// It is the caller's responsibility to check bounds and alignment beforehand.
/// Most likely, you want to call `InterpCx::write_scalar` instead of this method.
#[instrument(skip(self, cx), level = "debug")]
pub fn write_scalar(
&mut self,
cx: &impl HasDataLayout,
@ -491,7 +516,8 @@ impl<Prov: Provenance, Extra> Allocation<Prov, Extra> {
// See if we have to also store some provenance.
if let Some(provenance) = provenance {
self.provenance.0.insert(range.start, provenance);
assert_eq!(range.size, cx.data_layout().pointer_size);
self.provenance.insert_ptr(range.start, provenance, cx);
}
Ok(())
@ -500,750 +526,25 @@ impl<Prov: Provenance, Extra> Allocation<Prov, Extra> {
/// Write "uninit" to the given memory range.
pub fn write_uninit(&mut self, cx: &impl HasDataLayout, range: AllocRange) -> AllocResult {
self.mark_init(range, false);
self.clear_provenance(cx, range)?;
self.provenance.clear(range, cx)?;
return Ok(());
}
}
/// Provenance.
impl<Prov: Copy, Extra> Allocation<Prov, Extra> {
/// Returns all provenance overlapping with the given pointer-offset pair.
fn range_get_provenance(&self, cx: &impl HasDataLayout, range: AllocRange) -> &[(Size, Prov)] {
// We have to go back `pointer_size - 1` bytes, as that one would still overlap with
// the beginning of this range.
let start = range.start.bytes().saturating_sub(cx.data_layout().pointer_size.bytes() - 1);
self.provenance.range(Size::from_bytes(start)..range.end())
}
/// Get the provenance of a single byte.
fn offset_get_provenance(&self, cx: &impl HasDataLayout, offset: Size) -> Option<Prov> {
let prov = self.range_get_provenance(cx, alloc_range(offset, Size::from_bytes(1)));
assert!(prov.len() <= 1);
prov.first().map(|(_offset, prov)| *prov)
}
/// Returns whether this allocation has progrnance overlapping with the given range.
///
/// Note: this function exists to allow `range_get_provenance` to be private, in order to somewhat
/// limit access to provenance outside of the `Allocation` abstraction.
///
pub fn range_has_provenance(&self, cx: &impl HasDataLayout, range: AllocRange) -> bool {
!self.range_get_provenance(cx, range).is_empty()
}
/// Removes all provenance inside the given range.
/// If there is provenance overlapping with the edges, it
/// are removed as well *and* the bytes they cover are marked as
/// uninitialized. This is a somewhat odd "spooky action at a distance",
/// but it allows strictly more code to run than if we would just error
/// immediately in that case.
fn clear_provenance(&mut self, cx: &impl HasDataLayout, range: AllocRange) -> AllocResult
where
Prov: Provenance,
{
// Find the start and end of the given range and its outermost provenance.
let (first, last) = {
// Find all provenance overlapping the given range.
let provenance = self.range_get_provenance(cx, range);
if provenance.is_empty() {
return Ok(());
}
(
provenance.first().unwrap().0,
provenance.last().unwrap().0 + cx.data_layout().pointer_size,
)
};
let start = range.start;
let end = range.end();
// We need to handle clearing the provenance from parts of a pointer.
// FIXME: Miri should preserve partial provenance; see
// https://github.com/rust-lang/miri/issues/2181.
if first < start {
if Prov::ERR_ON_PARTIAL_PTR_OVERWRITE {
return Err(AllocError::PartialPointerOverwrite(first));
}
warn!(
"Partial pointer overwrite! De-initializing memory at offsets {first:?}..{start:?}."
);
self.init_mask.set_range(first, start, false);
}
if last > end {
if Prov::ERR_ON_PARTIAL_PTR_OVERWRITE {
return Err(AllocError::PartialPointerOverwrite(
last - cx.data_layout().pointer_size,
));
}
warn!(
"Partial pointer overwrite! De-initializing memory at offsets {end:?}..{last:?}."
);
self.init_mask.set_range(end, last, false);
}
// Forget all the provenance.
// Since provenance do not overlap, we know that removing until `last` (exclusive) is fine,
// i.e., this will not remove any other provenance just after the ones we care about.
self.provenance.0.remove_range(first..last);
Ok(())
}
}
/// Stores the provenance information of pointers stored in memory.
#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
pub struct ProvenanceMap<Prov = AllocId>(SortedMap<Size, Prov>);
impl<Prov> ProvenanceMap<Prov> {
pub fn new() -> Self {
ProvenanceMap(SortedMap::new())
}
// The caller must guarantee that the given provenance list is already sorted
// by address and contain no duplicates.
pub fn from_presorted(r: Vec<(Size, Prov)>) -> Self {
ProvenanceMap(SortedMap::from_presorted_elements(r))
}
}
impl<Prov> Deref for ProvenanceMap<Prov> {
type Target = SortedMap<Size, Prov>;
fn deref(&self) -> &Self::Target {
&self.0
}
}
/// A partial, owned list of provenance to transfer into another allocation.
///
/// Offsets are already adjusted to the destination allocation.
pub struct AllocationProvenance<Prov> {
dest_provenance: Vec<(Size, Prov)>,
}
impl<Prov: Copy, Extra> Allocation<Prov, Extra> {
pub fn prepare_provenance_copy(
&self,
cx: &impl HasDataLayout,
src: AllocRange,
dest: Size,
count: u64,
) -> AllocationProvenance<Prov> {
let provenance = self.range_get_provenance(cx, src);
if provenance.is_empty() {
return AllocationProvenance { dest_provenance: Vec::new() };
}
let size = src.size;
let mut new_provenance = Vec::with_capacity(provenance.len() * (count as usize));
// If `count` is large, this is rather wasteful -- we are allocating a big array here, which
// is mostly filled with redundant information since it's just N copies of the same `Prov`s
// at slightly adjusted offsets. The reason we do this is so that in `mark_provenance_range`
// we can use `insert_presorted`. That wouldn't work with an `Iterator` that just produces
// the right sequence of provenance for all N copies.
for i in 0..count {
new_provenance.extend(provenance.iter().map(|&(offset, reloc)| {
// compute offset for current repetition
let dest_offset = dest + size * i; // `Size` operations
(
// shift offsets from source allocation to destination allocation
(offset + dest_offset) - src.start, // `Size` operations
reloc,
)
}));
}
AllocationProvenance { dest_provenance: new_provenance }
}
/// Applies a provenance copy.
/// The affected range, as defined in the parameters to `prepare_provenance_copy` is expected
/// Applies a previously prepared provenance copy.
/// The affected range, as defined in the parameters to `provenance().prepare_copy` is expected
/// to be clear of provenance.
///
/// This is dangerous to use as it can violate internal `Allocation` invariants!
/// It only exists to support an efficient implementation of `mem_copy_repeatedly`.
pub fn mark_provenance_range(&mut self, provenance: AllocationProvenance<Prov>) {
self.provenance.0.insert_presorted(provenance.dest_provenance);
}
}
////////////////////////////////////////////////////////////////////////////////
// Uninitialized byte tracking
////////////////////////////////////////////////////////////////////////////////
type Block = u64;
/// A bitmask where each bit refers to the byte with the same index. If the bit is `true`, the byte
/// is initialized. If it is `false` the byte is uninitialized.
// Note: for performance reasons when interning, some of the `InitMask` fields can be partially
// hashed. (see the `Hash` impl below for more details), so the impl is not derived.
#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, TyEncodable, TyDecodable)]
#[derive(HashStable)]
pub struct InitMask {
blocks: Vec<Block>,
len: Size,
}
// Const allocations are only hashed for interning. However, they can be large, making the hashing
// expensive especially since it uses `FxHash`: it's better suited to short keys, not potentially
// big buffers like the allocation's init mask. We can partially hash some fields when they're
// large.
impl hash::Hash for InitMask {
fn hash<H: hash::Hasher>(&self, state: &mut H) {
const MAX_BLOCKS_TO_HASH: usize = MAX_BYTES_TO_HASH / std::mem::size_of::<Block>();
const MAX_BLOCKS_LEN: usize = MAX_HASHED_BUFFER_LEN / std::mem::size_of::<Block>();
// Partially hash the `blocks` buffer when it is large. To limit collisions with common
// prefixes and suffixes, we hash the length and some slices of the buffer.
let block_count = self.blocks.len();
if block_count > MAX_BLOCKS_LEN {
// Hash the buffer's length.
block_count.hash(state);
// And its head and tail.
self.blocks[..MAX_BLOCKS_TO_HASH].hash(state);
self.blocks[block_count - MAX_BLOCKS_TO_HASH..].hash(state);
} else {
self.blocks.hash(state);
}
// Hash the other fields as usual.
self.len.hash(state);
}
}
impl InitMask {
pub const BLOCK_SIZE: u64 = 64;
#[inline]
fn bit_index(bits: Size) -> (usize, usize) {
// BLOCK_SIZE is the number of bits that can fit in a `Block`.
// Each bit in a `Block` represents the initialization state of one byte of an allocation,
// so we use `.bytes()` here.
let bits = bits.bytes();
let a = bits / InitMask::BLOCK_SIZE;
let b = bits % InitMask::BLOCK_SIZE;
(usize::try_from(a).unwrap(), usize::try_from(b).unwrap())
pub fn provenance_apply_copy(&mut self, copy: ProvenanceCopy<Prov>) {
self.provenance.apply_copy(copy)
}
#[inline]
fn size_from_bit_index(block: impl TryInto<u64>, bit: impl TryInto<u64>) -> Size {
let block = block.try_into().ok().unwrap();
let bit = bit.try_into().ok().unwrap();
Size::from_bytes(block * InitMask::BLOCK_SIZE + bit)
}
pub fn new(size: Size, state: bool) -> Self {
let mut m = InitMask { blocks: vec![], len: Size::ZERO };
m.grow(size, state);
m
}
pub fn set_range(&mut self, start: Size, end: Size, new_state: bool) {
let len = self.len;
if end > len {
self.grow(end - len, new_state);
}
self.set_range_inbounds(start, end, new_state);
}
pub fn set_range_inbounds(&mut self, start: Size, end: Size, new_state: bool) {
let (blocka, bita) = Self::bit_index(start);
let (blockb, bitb) = Self::bit_index(end);
if blocka == blockb {
// First set all bits except the first `bita`,
// then unset the last `64 - bitb` bits.
let range = if bitb == 0 {
u64::MAX << bita
} else {
(u64::MAX << bita) & (u64::MAX >> (64 - bitb))
};
if new_state {
self.blocks[blocka] |= range;
} else {
self.blocks[blocka] &= !range;
}
return;
}
// across block boundaries
if new_state {
// Set `bita..64` to `1`.
self.blocks[blocka] |= u64::MAX << bita;
// Set `0..bitb` to `1`.
if bitb != 0 {
self.blocks[blockb] |= u64::MAX >> (64 - bitb);
}
// Fill in all the other blocks (much faster than one bit at a time).
for block in (blocka + 1)..blockb {
self.blocks[block] = u64::MAX;
}
} else {
// Set `bita..64` to `0`.
self.blocks[blocka] &= !(u64::MAX << bita);
// Set `0..bitb` to `0`.
if bitb != 0 {
self.blocks[blockb] &= !(u64::MAX >> (64 - bitb));
}
// Fill in all the other blocks (much faster than one bit at a time).
for block in (blocka + 1)..blockb {
self.blocks[block] = 0;
}
}
}
#[inline]
pub fn get(&self, i: Size) -> bool {
let (block, bit) = Self::bit_index(i);
(self.blocks[block] & (1 << bit)) != 0
}
#[inline]
pub fn set(&mut self, i: Size, new_state: bool) {
let (block, bit) = Self::bit_index(i);
self.set_bit(block, bit, new_state);
}
#[inline]
fn set_bit(&mut self, block: usize, bit: usize, new_state: bool) {
if new_state {
self.blocks[block] |= 1 << bit;
} else {
self.blocks[block] &= !(1 << bit);
}
}
pub fn grow(&mut self, amount: Size, new_state: bool) {
if amount.bytes() == 0 {
return;
}
let unused_trailing_bits =
u64::try_from(self.blocks.len()).unwrap() * Self::BLOCK_SIZE - self.len.bytes();
if amount.bytes() > unused_trailing_bits {
let additional_blocks = amount.bytes() / Self::BLOCK_SIZE + 1;
self.blocks.extend(
// FIXME(oli-obk): optimize this by repeating `new_state as Block`.
iter::repeat(0).take(usize::try_from(additional_blocks).unwrap()),
);
}
let start = self.len;
self.len += amount;
self.set_range_inbounds(start, start + amount, new_state); // `Size` operation
}
/// Returns the index of the first bit in `start..end` (end-exclusive) that is equal to is_init.
fn find_bit(&self, start: Size, end: Size, is_init: bool) -> Option<Size> {
/// A fast implementation of `find_bit`,
/// which skips over an entire block at a time if it's all 0s (resp. 1s),
/// and finds the first 1 (resp. 0) bit inside a block using `trailing_zeros` instead of a loop.
///
/// Note that all examples below are written with 8 (instead of 64) bit blocks for simplicity,
/// and with the least significant bit (and lowest block) first:
/// ```text
/// 00000000|00000000
/// ^ ^ ^ ^
/// index: 0 7 8 15
/// ```
/// Also, if not stated, assume that `is_init = true`, that is, we are searching for the first 1 bit.
fn find_bit_fast(
init_mask: &InitMask,
start: Size,
end: Size,
is_init: bool,
) -> Option<Size> {
/// Search one block, returning the index of the first bit equal to `is_init`.
fn search_block(
bits: Block,
block: usize,
start_bit: usize,
is_init: bool,
) -> Option<Size> {
// For the following examples, assume this function was called with:
// bits = 0b00111011
// start_bit = 3
// is_init = false
// Note that, for the examples in this function, the most significant bit is written first,
// which is backwards compared to the comments in `find_bit`/`find_bit_fast`.
// Invert bits so we're always looking for the first set bit.
// ! 0b00111011
// bits = 0b11000100
let bits = if is_init { bits } else { !bits };
// Mask off unused start bits.
// 0b11000100
// & 0b11111000
// bits = 0b11000000
let bits = bits & (!0 << start_bit);
// Find set bit, if any.
// bit = trailing_zeros(0b11000000)
// bit = 6
if bits == 0 {
None
} else {
let bit = bits.trailing_zeros();
Some(InitMask::size_from_bit_index(block, bit))
}
}
if start >= end {
return None;
}
// Convert `start` and `end` to block indexes and bit indexes within each block.
// We must convert `end` to an inclusive bound to handle block boundaries correctly.
//
// For example:
//
// (a) 00000000|00000000 (b) 00000000|
// ^~~~~~~~~~~^ ^~~~~~~~~^
// start end start end
//
// In both cases, the block index of `end` is 1.
// But we do want to search block 1 in (a), and we don't in (b).
//
// We subtract 1 from both end positions to make them inclusive:
//
// (a) 00000000|00000000 (b) 00000000|
// ^~~~~~~~~~^ ^~~~~~~^
// start end_inclusive start end_inclusive
//
// For (a), the block index of `end_inclusive` is 1, and for (b), it's 0.
// This provides the desired behavior of searching blocks 0 and 1 for (a),
// and searching only block 0 for (b).
// There is no concern of overflows since we checked for `start >= end` above.
let (start_block, start_bit) = InitMask::bit_index(start);
let end_inclusive = Size::from_bytes(end.bytes() - 1);
let (end_block_inclusive, _) = InitMask::bit_index(end_inclusive);
// Handle first block: need to skip `start_bit` bits.
//
// We need to handle the first block separately,
// because there may be bits earlier in the block that should be ignored,
// such as the bit marked (1) in this example:
//
// (1)
// -|------
// (c) 01000000|00000000|00000001
// ^~~~~~~~~~~~~~~~~~^
// start end
if let Some(i) =
search_block(init_mask.blocks[start_block], start_block, start_bit, is_init)
{
// If the range is less than a block, we may find a matching bit after `end`.
//
// For example, we shouldn't successfully find bit (2), because it's after `end`:
//
// (2)
// -------|
// (d) 00000001|00000000|00000001
// ^~~~~^
// start end
//
// An alternative would be to mask off end bits in the same way as we do for start bits,
// but performing this check afterwards is faster and simpler to implement.
if i < end {
return Some(i);
} else {
return None;
}
}
// Handle remaining blocks.
//
// We can skip over an entire block at once if it's all 0s (resp. 1s).
// The block marked (3) in this example is the first block that will be handled by this loop,
// and it will be skipped for that reason:
//
// (3)
// --------
// (e) 01000000|00000000|00000001
// ^~~~~~~~~~~~~~~~~~^
// start end
if start_block < end_block_inclusive {
// This loop is written in a specific way for performance.
// Notably: `..end_block_inclusive + 1` is used for an inclusive range instead of `..=end_block_inclusive`,
// and `.zip(start_block + 1..)` is used to track the index instead of `.enumerate().skip().take()`,
// because both alternatives result in significantly worse codegen.
// `end_block_inclusive + 1` is guaranteed not to wrap, because `end_block_inclusive <= end / BLOCK_SIZE`,
// and `BLOCK_SIZE` (the number of bits per block) will always be at least 8 (1 byte).
for (&bits, block) in init_mask.blocks[start_block + 1..end_block_inclusive + 1]
.iter()
.zip(start_block + 1..)
{
if let Some(i) = search_block(bits, block, 0, is_init) {
// If this is the last block, we may find a matching bit after `end`.
//
// For example, we shouldn't successfully find bit (4), because it's after `end`:
//
// (4)
// -------|
// (f) 00000001|00000000|00000001
// ^~~~~~~~~~~~~~~~~~^
// start end
//
// As above with example (d), we could handle the end block separately and mask off end bits,
// but unconditionally searching an entire block at once and performing this check afterwards
// is faster and much simpler to implement.
if i < end {
return Some(i);
} else {
return None;
}
}
}
}
None
}
#[cfg_attr(not(debug_assertions), allow(dead_code))]
fn find_bit_slow(
init_mask: &InitMask,
start: Size,
end: Size,
is_init: bool,
) -> Option<Size> {
(start..end).find(|&i| init_mask.get(i) == is_init)
}
let result = find_bit_fast(self, start, end, is_init);
debug_assert_eq!(
result,
find_bit_slow(self, start, end, is_init),
"optimized implementation of find_bit is wrong for start={:?} end={:?} is_init={} init_mask={:#?}",
start,
end,
is_init,
self
);
result
}
}
/// A contiguous chunk of initialized or uninitialized memory.
pub enum InitChunk {
Init(Range<Size>),
Uninit(Range<Size>),
}
impl InitChunk {
#[inline]
pub fn is_init(&self) -> bool {
match self {
Self::Init(_) => true,
Self::Uninit(_) => false,
}
}
#[inline]
pub fn range(&self) -> Range<Size> {
match self {
Self::Init(r) => r.clone(),
Self::Uninit(r) => r.clone(),
}
}
}
impl InitMask {
/// Checks whether the range `start..end` (end-exclusive) is entirely initialized.
///
/// Returns `Ok(())` if it's initialized. Otherwise returns a range of byte
/// indexes for the first contiguous span of the uninitialized access.
#[inline]
pub fn is_range_initialized(&self, start: Size, end: Size) -> Result<(), AllocRange> {
if end > self.len {
return Err(AllocRange::from(self.len..end));
}
let uninit_start = self.find_bit(start, end, false);
match uninit_start {
Some(uninit_start) => {
let uninit_end = self.find_bit(uninit_start, end, true).unwrap_or(end);
Err(AllocRange::from(uninit_start..uninit_end))
}
None => Ok(()),
}
}
/// Returns an iterator, yielding a range of byte indexes for each contiguous region
/// of initialized or uninitialized bytes inside the range `start..end` (end-exclusive).
///
/// The iterator guarantees the following:
/// - Chunks are nonempty.
/// - Chunks are adjacent (each range's start is equal to the previous range's end).
/// - Chunks span exactly `start..end` (the first starts at `start`, the last ends at `end`).
/// - Chunks alternate between [`InitChunk::Init`] and [`InitChunk::Uninit`].
#[inline]
pub fn range_as_init_chunks(&self, start: Size, end: Size) -> InitChunkIter<'_> {
assert!(end <= self.len);
let is_init = if start < end {
self.get(start)
} else {
// `start..end` is empty: there are no chunks, so use some arbitrary value
false
};
InitChunkIter { init_mask: self, is_init, start, end }
}
}
/// Yields [`InitChunk`]s. See [`InitMask::range_as_init_chunks`].
#[derive(Clone)]
pub struct InitChunkIter<'a> {
init_mask: &'a InitMask,
/// Whether the next chunk we will return is initialized.
/// If there are no more chunks, contains some arbitrary value.
is_init: bool,
/// The current byte index into `init_mask`.
start: Size,
/// The end byte index into `init_mask`.
end: Size,
}
impl<'a> Iterator for InitChunkIter<'a> {
type Item = InitChunk;
#[inline]
fn next(&mut self) -> Option<Self::Item> {
if self.start >= self.end {
return None;
}
let end_of_chunk =
self.init_mask.find_bit(self.start, self.end, !self.is_init).unwrap_or(self.end);
let range = self.start..end_of_chunk;
let ret =
Some(if self.is_init { InitChunk::Init(range) } else { InitChunk::Uninit(range) });
self.is_init = !self.is_init;
self.start = end_of_chunk;
ret
}
}
/// Uninitialized bytes.
impl<Prov: Copy, Extra> Allocation<Prov, Extra> {
/// Checks whether the given range is entirely initialized.
///
/// Returns `Ok(())` if it's initialized. Otherwise returns the range of byte
/// indexes of the first contiguous uninitialized access.
fn is_init(&self, range: AllocRange) -> Result<(), AllocRange> {
self.init_mask.is_range_initialized(range.start, range.end()) // `Size` addition
}
/// Checks that a range of bytes is initialized. If not, returns the `InvalidUninitBytes`
/// error which will report the first range of bytes which is uninitialized.
fn check_init(&self, range: AllocRange) -> AllocResult {
self.is_init(range).map_err(|uninit_range| {
AllocError::InvalidUninitBytes(Some(UninitBytesAccess {
access: range,
uninit: uninit_range,
}))
})
}
fn mark_init(&mut self, range: AllocRange, is_init: bool) {
if range.size.bytes() == 0 {
return;
}
assert!(self.mutability == Mutability::Mut);
self.init_mask.set_range(range.start, range.end(), is_init);
}
}
/// Run-length encoding of the uninit mask.
/// Used to copy parts of a mask multiple times to another allocation.
pub struct InitMaskCompressed {
/// Whether the first range is initialized.
initial: bool,
/// The lengths of ranges that are run-length encoded.
/// The initialization state of the ranges alternate starting with `initial`.
ranges: smallvec::SmallVec<[u64; 1]>,
}
impl InitMaskCompressed {
pub fn no_bytes_init(&self) -> bool {
// The `ranges` are run-length encoded and of alternating initialization state.
// So if `ranges.len() > 1` then the second block is an initialized range.
!self.initial && self.ranges.len() == 1
}
}
/// Transferring the initialization mask to other allocations.
impl<Prov, Extra> Allocation<Prov, Extra> {
/// Creates a run-length encoding of the initialization mask; panics if range is empty.
///
/// This is essentially a more space-efficient version of
/// `InitMask::range_as_init_chunks(...).collect::<Vec<_>>()`.
pub fn compress_uninit_range(&self, range: AllocRange) -> InitMaskCompressed {
// Since we are copying `size` bytes from `src` to `dest + i * size` (`for i in 0..repeat`),
// a naive initialization mask copying algorithm would repeatedly have to read the initialization mask from
// the source and write it to the destination. Even if we optimized the memory accesses,
// we'd be doing all of this `repeat` times.
// Therefore we precompute a compressed version of the initialization mask of the source value and
// then write it back `repeat` times without computing any more information from the source.
// A precomputed cache for ranges of initialized / uninitialized bits
// 0000010010001110 will become
// `[5, 1, 2, 1, 3, 3, 1]`,
// where each element toggles the state.
let mut ranges = smallvec::SmallVec::<[u64; 1]>::new();
let mut chunks = self.init_mask.range_as_init_chunks(range.start, range.end()).peekable();
let initial = chunks.peek().expect("range should be nonempty").is_init();
// Here we rely on `range_as_init_chunks` to yield alternating init/uninit chunks.
for chunk in chunks {
let len = chunk.range().end.bytes() - chunk.range().start.bytes();
ranges.push(len);
}
InitMaskCompressed { ranges, initial }
}
/// Applies multiple instances of the run-length encoding to the initialization mask.
/// Applies a previously prepared copy of the init mask.
///
/// This is dangerous to use as it can violate internal `Allocation` invariants!
/// It only exists to support an efficient implementation of `mem_copy_repeatedly`.
pub fn mark_compressed_init_range(
&mut self,
defined: &InitMaskCompressed,
range: AllocRange,
repeat: u64,
) {
// An optimization where we can just overwrite an entire range of initialization
// bits if they are going to be uniformly `1` or `0`.
if defined.ranges.len() <= 1 {
self.init_mask.set_range_inbounds(
range.start,
range.start + range.size * repeat, // `Size` operations
defined.initial,
);
return;
}
for mut j in 0..repeat {
j *= range.size.bytes();
j += range.start.bytes();
let mut cur = defined.initial;
for range in &defined.ranges {
let old_j = j;
j += range;
self.init_mask.set_range_inbounds(
Size::from_bytes(old_j),
Size::from_bytes(j),
cur,
);
cur = !cur;
}
}
pub fn init_mask_apply_copy(&mut self, copy: InitCopy, range: AllocRange, repeat: u64) {
self.init_mask.apply_copy(copy, range, repeat)
}
}

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compiler/rustc_middle/src/mir/interpret/allocation/init_mask.rs Normal file
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@ -0,0 +1,530 @@
use std::hash;
use std::iter;
use std::ops::Range;
use rustc_target::abi::Size;
use super::AllocRange;
type Block = u64;
/// A bitmask where each bit refers to the byte with the same index. If the bit is `true`, the byte
/// is initialized. If it is `false` the byte is uninitialized.
// Note: for performance reasons when interning, some of the `InitMask` fields can be partially
// hashed. (see the `Hash` impl below for more details), so the impl is not derived.
#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, TyEncodable, TyDecodable)]
#[derive(HashStable)]
pub struct InitMask {
blocks: Vec<Block>,
len: Size,
}
// Const allocations are only hashed for interning. However, they can be large, making the hashing
// expensive especially since it uses `FxHash`: it's better suited to short keys, not potentially
// big buffers like the allocation's init mask. We can partially hash some fields when they're
// large.
impl hash::Hash for InitMask {
fn hash<H: hash::Hasher>(&self, state: &mut H) {
const MAX_BLOCKS_TO_HASH: usize = super::MAX_BYTES_TO_HASH / std::mem::size_of::<Block>();
const MAX_BLOCKS_LEN: usize = super::MAX_HASHED_BUFFER_LEN / std::mem::size_of::<Block>();
// Partially hash the `blocks` buffer when it is large. To limit collisions with common
// prefixes and suffixes, we hash the length and some slices of the buffer.
let block_count = self.blocks.len();
if block_count > MAX_BLOCKS_LEN {
// Hash the buffer's length.
block_count.hash(state);
// And its head and tail.
self.blocks[..MAX_BLOCKS_TO_HASH].hash(state);
self.blocks[block_count - MAX_BLOCKS_TO_HASH..].hash(state);
} else {
self.blocks.hash(state);
}
// Hash the other fields as usual.
self.len.hash(state);
}
}
impl InitMask {
pub const BLOCK_SIZE: u64 = 64;
pub fn new(size: Size, state: bool) -> Self {
let mut m = InitMask { blocks: vec![], len: Size::ZERO };
m.grow(size, state);
m
}
#[inline]
fn bit_index(bits: Size) -> (usize, usize) {
// BLOCK_SIZE is the number of bits that can fit in a `Block`.
// Each bit in a `Block` represents the initialization state of one byte of an allocation,
// so we use `.bytes()` here.
let bits = bits.bytes();
let a = bits / InitMask::BLOCK_SIZE;
let b = bits % InitMask::BLOCK_SIZE;
(usize::try_from(a).unwrap(), usize::try_from(b).unwrap())
}
#[inline]
fn size_from_bit_index(block: impl TryInto<u64>, bit: impl TryInto<u64>) -> Size {
let block = block.try_into().ok().unwrap();
let bit = bit.try_into().ok().unwrap();
Size::from_bytes(block * InitMask::BLOCK_SIZE + bit)
}
/// Checks whether the `range` is entirely initialized.
///
/// Returns `Ok(())` if it's initialized. Otherwise returns a range of byte
/// indexes for the first contiguous span of the uninitialized access.
#[inline]
pub fn is_range_initialized(&self, range: AllocRange) -> Result<(), AllocRange> {
let end = range.end();
if end > self.len {
return Err(AllocRange::from(self.len..end));
}
let uninit_start = self.find_bit(range.start, end, false);
match uninit_start {
Some(uninit_start) => {
let uninit_end = self.find_bit(uninit_start, end, true).unwrap_or(end);
Err(AllocRange::from(uninit_start..uninit_end))
}
None => Ok(()),
}
}
pub fn set_range(&mut self, range: AllocRange, new_state: bool) {
let end = range.end();
let len = self.len;
if end > len {
self.grow(end - len, new_state);
}
self.set_range_inbounds(range.start, end, new_state);
}
fn set_range_inbounds(&mut self, start: Size, end: Size, new_state: bool) {
let (blocka, bita) = Self::bit_index(start);
let (blockb, bitb) = Self::bit_index(end);
if blocka == blockb {
// First set all bits except the first `bita`,
// then unset the last `64 - bitb` bits.
let range = if bitb == 0 {
u64::MAX << bita
} else {
(u64::MAX << bita) & (u64::MAX >> (64 - bitb))
};
if new_state {
self.blocks[blocka] |= range;
} else {
self.blocks[blocka] &= !range;
}
return;
}
// across block boundaries
if new_state {
// Set `bita..64` to `1`.
self.blocks[blocka] |= u64::MAX << bita;
// Set `0..bitb` to `1`.
if bitb != 0 {
self.blocks[blockb] |= u64::MAX >> (64 - bitb);
}
// Fill in all the other blocks (much faster than one bit at a time).
for block in (blocka + 1)..blockb {
self.blocks[block] = u64::MAX;
}
} else {
// Set `bita..64` to `0`.
self.blocks[blocka] &= !(u64::MAX << bita);
// Set `0..bitb` to `0`.
if bitb != 0 {
self.blocks[blockb] &= !(u64::MAX >> (64 - bitb));
}
// Fill in all the other blocks (much faster than one bit at a time).
for block in (blocka + 1)..blockb {
self.blocks[block] = 0;
}
}
}
#[inline]
pub fn get(&self, i: Size) -> bool {
let (block, bit) = Self::bit_index(i);
(self.blocks[block] & (1 << bit)) != 0
}
fn grow(&mut self, amount: Size, new_state: bool) {
if amount.bytes() == 0 {
return;
}
let unused_trailing_bits =
u64::try_from(self.blocks.len()).unwrap() * Self::BLOCK_SIZE - self.len.bytes();
if amount.bytes() > unused_trailing_bits {
let additional_blocks = amount.bytes() / Self::BLOCK_SIZE + 1;
self.blocks.extend(
// FIXME(oli-obk): optimize this by repeating `new_state as Block`.
iter::repeat(0).take(usize::try_from(additional_blocks).unwrap()),
);
}
let start = self.len;
self.len += amount;
self.set_range_inbounds(start, start + amount, new_state); // `Size` operation
}
/// Returns the index of the first bit in `start..end` (end-exclusive) that is equal to is_init.
fn find_bit(&self, start: Size, end: Size, is_init: bool) -> Option<Size> {
/// A fast implementation of `find_bit`,
/// which skips over an entire block at a time if it's all 0s (resp. 1s),
/// and finds the first 1 (resp. 0) bit inside a block using `trailing_zeros` instead of a loop.
///
/// Note that all examples below are written with 8 (instead of 64) bit blocks for simplicity,
/// and with the least significant bit (and lowest block) first:
/// ```text
/// 00000000|00000000
/// ^ ^ ^ ^
/// index: 0 7 8 15
/// ```
/// Also, if not stated, assume that `is_init = true`, that is, we are searching for the first 1 bit.
fn find_bit_fast(
init_mask: &InitMask,
start: Size,
end: Size,
is_init: bool,
) -> Option<Size> {
/// Search one block, returning the index of the first bit equal to `is_init`.
fn search_block(
bits: Block,
block: usize,
start_bit: usize,
is_init: bool,
) -> Option<Size> {
// For the following examples, assume this function was called with:
// bits = 0b00111011
// start_bit = 3
// is_init = false
// Note that, for the examples in this function, the most significant bit is written first,
// which is backwards compared to the comments in `find_bit`/`find_bit_fast`.
// Invert bits so we're always looking for the first set bit.
// ! 0b00111011
// bits = 0b11000100
let bits = if is_init { bits } else { !bits };
// Mask off unused start bits.
// 0b11000100
// & 0b11111000
// bits = 0b11000000
let bits = bits & (!0 << start_bit);
// Find set bit, if any.
// bit = trailing_zeros(0b11000000)
// bit = 6
if bits == 0 {
None
} else {
let bit = bits.trailing_zeros();
Some(InitMask::size_from_bit_index(block, bit))
}
}
if start >= end {
return None;
}
// Convert `start` and `end` to block indexes and bit indexes within each block.
// We must convert `end` to an inclusive bound to handle block boundaries correctly.
//
// For example:
//
// (a) 00000000|00000000 (b) 00000000|
// ^~~~~~~~~~~^ ^~~~~~~~~^
// start end start end
//
// In both cases, the block index of `end` is 1.
// But we do want to search block 1 in (a), and we don't in (b).
//
// We subtract 1 from both end positions to make them inclusive:
//
// (a) 00000000|00000000 (b) 00000000|
// ^~~~~~~~~~^ ^~~~~~~^
// start end_inclusive start end_inclusive
//
// For (a), the block index of `end_inclusive` is 1, and for (b), it's 0.
// This provides the desired behavior of searching blocks 0 and 1 for (a),
// and searching only block 0 for (b).
// There is no concern of overflows since we checked for `start >= end` above.
let (start_block, start_bit) = InitMask::bit_index(start);
let end_inclusive = Size::from_bytes(end.bytes() - 1);
let (end_block_inclusive, _) = InitMask::bit_index(end_inclusive);
// Handle first block: need to skip `start_bit` bits.
//
// We need to handle the first block separately,
// because there may be bits earlier in the block that should be ignored,
// such as the bit marked (1) in this example:
//
// (1)
// -|------
// (c) 01000000|00000000|00000001
// ^~~~~~~~~~~~~~~~~~^
// start end
if let Some(i) =
search_block(init_mask.blocks[start_block], start_block, start_bit, is_init)
{
// If the range is less than a block, we may find a matching bit after `end`.
//
// For example, we shouldn't successfully find bit (2), because it's after `end`:
//
// (2)
// -------|
// (d) 00000001|00000000|00000001
// ^~~~~^
// start end
//
// An alternative would be to mask off end bits in the same way as we do for start bits,
// but performing this check afterwards is faster and simpler to implement.
if i < end {
return Some(i);
} else {
return None;
}
}
// Handle remaining blocks.
//
// We can skip over an entire block at once if it's all 0s (resp. 1s).
// The block marked (3) in this example is the first block that will be handled by this loop,
// and it will be skipped for that reason:
//
// (3)
// --------
// (e) 01000000|00000000|00000001
// ^~~~~~~~~~~~~~~~~~^
// start end
if start_block < end_block_inclusive {
// This loop is written in a specific way for performance.
// Notably: `..end_block_inclusive + 1` is used for an inclusive range instead of `..=end_block_inclusive`,
// and `.zip(start_block + 1..)` is used to track the index instead of `.enumerate().skip().take()`,
// because both alternatives result in significantly worse codegen.
// `end_block_inclusive + 1` is guaranteed not to wrap, because `end_block_inclusive <= end / BLOCK_SIZE`,
// and `BLOCK_SIZE` (the number of bits per block) will always be at least 8 (1 byte).
for (&bits, block) in init_mask.blocks[start_block + 1..end_block_inclusive + 1]
.iter()
.zip(start_block + 1..)
{
if let Some(i) = search_block(bits, block, 0, is_init) {
// If this is the last block, we may find a matching bit after `end`.
//
// For example, we shouldn't successfully find bit (4), because it's after `end`:
//
// (4)
// -------|
// (f) 00000001|00000000|00000001
// ^~~~~~~~~~~~~~~~~~^
// start end
//
// As above with example (d), we could handle the end block separately and mask off end bits,
// but unconditionally searching an entire block at once and performing this check afterwards
// is faster and much simpler to implement.
if i < end {
return Some(i);
} else {
return None;
}
}
}
}
None
}
#[cfg_attr(not(debug_assertions), allow(dead_code))]
fn find_bit_slow(
init_mask: &InitMask,
start: Size,
end: Size,
is_init: bool,
) -> Option<Size> {
(start..end).find(|&i| init_mask.get(i) == is_init)
}
let result = find_bit_fast(self, start, end, is_init);
debug_assert_eq!(
result,
find_bit_slow(self, start, end, is_init),
"optimized implementation of find_bit is wrong for start={:?} end={:?} is_init={} init_mask={:#?}",
start,
end,
is_init,
self
);
result
}
}
/// A contiguous chunk of initialized or uninitialized memory.
pub enum InitChunk {
Init(Range<Size>),
Uninit(Range<Size>),
}
impl InitChunk {
#[inline]
pub fn is_init(&self) -> bool {
match self {
Self::Init(_) => true,
Self::Uninit(_) => false,
}
}
#[inline]
pub fn range(&self) -> Range<Size> {
match self {
Self::Init(r) => r.clone(),
Self::Uninit(r) => r.clone(),
}
}
}
impl InitMask {
/// Returns an iterator, yielding a range of byte indexes for each contiguous region
/// of initialized or uninitialized bytes inside the range `start..end` (end-exclusive).
///
/// The iterator guarantees the following:
/// - Chunks are nonempty.
/// - Chunks are adjacent (each range's start is equal to the previous range's end).
/// - Chunks span exactly `start..end` (the first starts at `start`, the last ends at `end`).
/// - Chunks alternate between [`InitChunk::Init`] and [`InitChunk::Uninit`].
#[inline]
pub fn range_as_init_chunks(&self, range: AllocRange) -> InitChunkIter<'_> {
let start = range.start;
let end = range.end();
assert!(end <= self.len);
let is_init = if start < end {
self.get(start)
} else {
// `start..end` is empty: there are no chunks, so use some arbitrary value
false
};
InitChunkIter { init_mask: self, is_init, start, end }
}
}
/// Yields [`InitChunk`]s. See [`InitMask::range_as_init_chunks`].
#[derive(Clone)]
pub struct InitChunkIter<'a> {
init_mask: &'a InitMask,
/// Whether the next chunk we will return is initialized.
/// If there are no more chunks, contains some arbitrary value.
is_init: bool,
/// The current byte index into `init_mask`.
start: Size,
/// The end byte index into `init_mask`.
end: Size,
}
impl<'a> Iterator for InitChunkIter<'a> {
type Item = InitChunk;
#[inline]
fn next(&mut self) -> Option<Self::Item> {
if self.start >= self.end {
return None;
}
let end_of_chunk =
self.init_mask.find_bit(self.start, self.end, !self.is_init).unwrap_or(self.end);
let range = self.start..end_of_chunk;
let ret =
Some(if self.is_init { InitChunk::Init(range) } else { InitChunk::Uninit(range) });
self.is_init = !self.is_init;
self.start = end_of_chunk;
ret
}
}
/// Run-length encoding of the uninit mask.
/// Used to copy parts of a mask multiple times to another allocation.
pub struct InitCopy {
/// Whether the first range is initialized.
initial: bool,
/// The lengths of ranges that are run-length encoded.
/// The initialization state of the ranges alternate starting with `initial`.
ranges: smallvec::SmallVec<[u64; 1]>,
}
impl InitCopy {
pub fn no_bytes_init(&self) -> bool {
// The `ranges` are run-length encoded and of alternating initialization state.
// So if `ranges.len() > 1` then the second block is an initialized range.
!self.initial && self.ranges.len() == 1
}
}
/// Transferring the initialization mask to other allocations.
impl InitMask {
/// Creates a run-length encoding of the initialization mask; panics if range is empty.
///
/// This is essentially a more space-efficient version of
/// `InitMask::range_as_init_chunks(...).collect::<Vec<_>>()`.
pub fn prepare_copy(&self, range: AllocRange) -> InitCopy {
// Since we are copying `size` bytes from `src` to `dest + i * size` (`for i in 0..repeat`),
// a naive initialization mask copying algorithm would repeatedly have to read the initialization mask from
// the source and write it to the destination. Even if we optimized the memory accesses,
// we'd be doing all of this `repeat` times.
// Therefore we precompute a compressed version of the initialization mask of the source value and
// then write it back `repeat` times without computing any more information from the source.
// A precomputed cache for ranges of initialized / uninitialized bits
// 0000010010001110 will become
// `[5, 1, 2, 1, 3, 3, 1]`,
// where each element toggles the state.
let mut ranges = smallvec::SmallVec::<[u64; 1]>::new();
let mut chunks = self.range_as_init_chunks(range).peekable();
let initial = chunks.peek().expect("range should be nonempty").is_init();
// Here we rely on `range_as_init_chunks` to yield alternating init/uninit chunks.
for chunk in chunks {
let len = chunk.range().end.bytes() - chunk.range().start.bytes();
ranges.push(len);
}
InitCopy { ranges, initial }
}
/// Applies multiple instances of the run-length encoding to the initialization mask.
pub fn apply_copy(&mut self, defined: InitCopy, range: AllocRange, repeat: u64) {
// An optimization where we can just overwrite an entire range of initialization
// bits if they are going to be uniformly `1` or `0`.
if defined.ranges.len() <= 1 {
self.set_range_inbounds(
range.start,
range.start + range.size * repeat, // `Size` operations
defined.initial,
);
return;
}
for mut j in 0..repeat {
j *= range.size.bytes();
j += range.start.bytes();
let mut cur = defined.initial;
for range in &defined.ranges {
let old_j = j;
j += range;
self.set_range_inbounds(Size::from_bytes(old_j), Size::from_bytes(j), cur);
cur = !cur;
}
}
}
}

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compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs Normal file
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//! Store the provenance for each byte in the range, with a more efficient
//! representation for the common case where PTR_SIZE consecutive bytes have the same provenance.
use std::cmp;
use rustc_data_structures::sorted_map::SortedMap;
use rustc_target::abi::{HasDataLayout, Size};
use super::{alloc_range, AllocError, AllocId, AllocRange, AllocResult, Provenance};
use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
/// Stores the provenance information of pointers stored in memory.
#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
#[derive(HashStable)]
pub struct ProvenanceMap<Prov = AllocId> {
/// Provenance in this map applies from the given offset for an entire pointer-size worth of
/// bytes. Two entires in this map are always at least a pointer size apart.
ptrs: SortedMap<Size, Prov>,
/// Provenance in this map only applies to the given single byte.
/// This map is disjoint from the previous. It will always be empty when
/// `Prov::OFFSET_IS_ADDR` is false.
bytes: Option<Box<SortedMap<Size, Prov>>>,
}
impl<D: Decoder, Prov: Provenance + Decodable<D>> Decodable<D> for ProvenanceMap<Prov> {
fn decode(d: &mut D) -> Self {
assert!(!Prov::OFFSET_IS_ADDR); // only `AllocId` is ever serialized
Self { ptrs: Decodable::decode(d), bytes: None }
}
}
impl<S: Encoder, Prov: Provenance + Encodable<S>> Encodable<S> for ProvenanceMap<Prov> {
fn encode(&self, s: &mut S) {
let Self { ptrs, bytes } = self;
assert!(!Prov::OFFSET_IS_ADDR); // only `AllocId` is ever serialized
debug_assert!(bytes.is_none());
ptrs.encode(s)
}
}
impl<Prov> ProvenanceMap<Prov> {
pub fn new() -> Self {
ProvenanceMap { ptrs: SortedMap::new(), bytes: None }
}
/// The caller must guarantee that the given provenance list is already sorted
/// by address and contain no duplicates.
pub fn from_presorted_ptrs(r: Vec<(Size, Prov)>) -> Self {
ProvenanceMap { ptrs: SortedMap::from_presorted_elements(r), bytes: None }
}
}
impl ProvenanceMap {
/// Give access to the ptr-sized provenances (which can also be thought of as relocations, and
/// indeed that is how codegen treats them).
///
/// Only exposed with `AllocId` provenance, since it panics if there is bytewise provenance.
#[inline]
pub fn ptrs(&self) -> &SortedMap<Size, AllocId> {
debug_assert!(self.bytes.is_none()); // `AllocId::OFFSET_IS_ADDR` is false so this cannot fail
&self.ptrs
}
}
impl<Prov: Provenance> ProvenanceMap<Prov> {
/// Returns all ptr-sized provenance in the given range.
/// If the range has length 0, returns provenance that crosses the edge between `start-1` and
/// `start`.
fn range_get_ptrs(&self, range: AllocRange, cx: &impl HasDataLayout) -> &[(Size, Prov)] {
// We have to go back `pointer_size - 1` bytes, as that one would still overlap with
// the beginning of this range.
let adjusted_start = Size::from_bytes(
range.start.bytes().saturating_sub(cx.data_layout().pointer_size.bytes() - 1),
);
self.ptrs.range(adjusted_start..range.end())
}
/// Returns all byte-wise provenance in the given range.
fn range_get_bytes(&self, range: AllocRange) -> &[(Size, Prov)] {
if let Some(bytes) = self.bytes.as_ref() {
bytes.range(range.start..range.end())
} else {
&[]
}
}
/// Get the provenance of a single byte.
pub fn get(&self, offset: Size, cx: &impl HasDataLayout) -> Option<Prov> {
let prov = self.range_get_ptrs(alloc_range(offset, Size::from_bytes(1)), cx);
debug_assert!(prov.len() <= 1);
if let Some(entry) = prov.first() {
// If it overlaps with this byte, it is on this byte.
debug_assert!(self.bytes.as_ref().map_or(true, |b| b.get(&offset).is_none()));
Some(entry.1)
} else {
// Look up per-byte provenance.
self.bytes.as_ref().and_then(|b| b.get(&offset).copied())
}
}
/// Check if here is ptr-sized provenance at the given index.
/// Does not mean anything for bytewise provenance! But can be useful as an optimization.
pub fn get_ptr(&self, offset: Size) -> Option<Prov> {
self.ptrs.get(&offset).copied()
}
/// Returns whether this allocation has provenance overlapping with the given range.
///
/// Note: this function exists to allow `range_get_provenance` to be private, in order to somewhat
/// limit access to provenance outside of the `Allocation` abstraction.
///
pub fn range_empty(&self, range: AllocRange, cx: &impl HasDataLayout) -> bool {
self.range_get_ptrs(range, cx).is_empty() && self.range_get_bytes(range).is_empty()
}
/// Yields all the provenances stored in this map.
pub fn provenances(&self) -> impl Iterator<Item = Prov> + '_ {
let bytes = self.bytes.iter().flat_map(|b| b.values());
self.ptrs.values().chain(bytes).copied()
}
pub fn insert_ptr(&mut self, offset: Size, prov: Prov, cx: &impl HasDataLayout) {
debug_assert!(self.range_empty(alloc_range(offset, cx.data_layout().pointer_size), cx));
self.ptrs.insert(offset, prov);
}
/// Removes all provenance inside the given range.
/// If there is provenance overlapping with the edges, might result in an error.
pub fn clear(&mut self, range: AllocRange, cx: &impl HasDataLayout) -> AllocResult {
let start = range.start;
let end = range.end();
// Clear the bytewise part -- this is easy.
if Prov::OFFSET_IS_ADDR {
if let Some(bytes) = self.bytes.as_mut() {
bytes.remove_range(start..end);
}
} else {
debug_assert!(self.bytes.is_none());
}
// For the ptr-sized part, find the first (inclusive) and last (exclusive) byte of
// provenance that overlaps with the given range.
let (first, last) = {
// Find all provenance overlapping the given range.
let provenance = self.range_get_ptrs(range, cx);
if provenance.is_empty() {
// No provenance in this range, we are done.
return Ok(());
}
(
provenance.first().unwrap().0,
provenance.last().unwrap().0 + cx.data_layout().pointer_size,
)
};
// We need to handle clearing the provenance from parts of a pointer.
if first < start {
if !Prov::OFFSET_IS_ADDR {
// We can't split up the provenance into less than a pointer.
return Err(AllocError::PartialPointerOverwrite(first));
}
// Insert the remaining part in the bytewise provenance.
let prov = self.ptrs[&first];
let bytes = self.bytes.get_or_insert_with(Box::default);
for offset in first..start {
bytes.insert(offset, prov);
}
}
if last > end {
let begin_of_last = last - cx.data_layout().pointer_size;
if !Prov::OFFSET_IS_ADDR {
// We can't split up the provenance into less than a pointer.
return Err(AllocError::PartialPointerOverwrite(begin_of_last));
}
// Insert the remaining part in the bytewise provenance.
let prov = self.ptrs[&begin_of_last];
let bytes = self.bytes.get_or_insert_with(Box::default);
for offset in end..last {
bytes.insert(offset, prov);
}
}
// Forget all the provenance.
// Since provenance do not overlap, we know that removing until `last` (exclusive) is fine,
// i.e., this will not remove any other provenance just after the ones we care about.
self.ptrs.remove_range(first..last);
Ok(())
}
}
/// A partial, owned list of provenance to transfer into another allocation.
///
/// Offsets are already adjusted to the destination allocation.
pub struct ProvenanceCopy<Prov> {
dest_ptrs: Option<Box<[(Size, Prov)]>>,
dest_bytes: Option<Box<[(Size, Prov)]>>,
}
impl<Prov: Provenance> ProvenanceMap<Prov> {
pub fn prepare_copy(
&self,
src: AllocRange,
dest: Size,
count: u64,
cx: &impl HasDataLayout,
) -> AllocResult<ProvenanceCopy<Prov>> {
let shift_offset = move |idx, offset| {
// compute offset for current repetition
let dest_offset = dest + src.size * idx; // `Size` operations
// shift offsets from source allocation to destination allocation
(offset - src.start) + dest_offset // `Size` operations
};
let ptr_size = cx.data_layout().pointer_size;
// # Pointer-sized provenances
// Get the provenances that are entirely within this range.
// (Different from `range_get_ptrs` which asks if they overlap the range.)
// Only makes sense if we are copying at least one pointer worth of bytes.
let mut dest_ptrs_box = None;
if src.size >= ptr_size {
let adjusted_end = Size::from_bytes(src.end().bytes() - (ptr_size.bytes() - 1));
let ptrs = self.ptrs.range(src.start..adjusted_end);
// If `count` is large, this is rather wasteful -- we are allocating a big array here, which
// is mostly filled with redundant information since it's just N copies of the same `Prov`s
// at slightly adjusted offsets. The reason we do this is so that in `mark_provenance_range`
// we can use `insert_presorted`. That wouldn't work with an `Iterator` that just produces
// the right sequence of provenance for all N copies.
// Basically, this large array would have to be created anyway in the target allocation.
let mut dest_ptrs = Vec::with_capacity(ptrs.len() * (count as usize));
for i in 0..count {
dest_ptrs
.extend(ptrs.iter().map(|&(offset, reloc)| (shift_offset(i, offset), reloc)));
}
debug_assert_eq!(dest_ptrs.len(), dest_ptrs.capacity());
dest_ptrs_box = Some(dest_ptrs.into_boxed_slice());
};
// # Byte-sized provenances
// This includes the existing bytewise provenance in the range, and ptr provenance
// that overlaps with the begin/end of the range.
let mut dest_bytes_box = None;
let begin_overlap = self.range_get_ptrs(alloc_range(src.start, Size::ZERO), cx).first();
let end_overlap = self.range_get_ptrs(alloc_range(src.end(), Size::ZERO), cx).first();
if !Prov::OFFSET_IS_ADDR {
// There can't be any bytewise provenance, and we cannot split up the begin/end overlap.
if let Some(entry) = begin_overlap {
return Err(AllocError::PartialPointerCopy(entry.0));
}
if let Some(entry) = end_overlap {
return Err(AllocError::PartialPointerCopy(entry.0));
}
debug_assert!(self.bytes.is_none());
} else {
let mut bytes = Vec::new();
// First, if there is a part of a pointer at the start, add that.
if let Some(entry) = begin_overlap {
trace!("start overlapping entry: {entry:?}");
// For really small copies, make sure we don't run off the end of the `src` range.
let entry_end = cmp::min(entry.0 + ptr_size, src.end());
for offset in src.start..entry_end {
bytes.push((offset, entry.1));
}
} else {
trace!("no start overlapping entry");
}
// Then the main part, bytewise provenance from `self.bytes`.
if let Some(all_bytes) = self.bytes.as_ref() {
bytes.extend(all_bytes.range(src.start..src.end()));
}
// And finally possibly parts of a pointer at the end.
if let Some(entry) = end_overlap {
trace!("end overlapping entry: {entry:?}");
// For really small copies, make sure we don't start before `src` does.
let entry_start = cmp::max(entry.0, src.start);
for offset in entry_start..src.end() {
if bytes.last().map_or(true, |bytes_entry| bytes_entry.0 < offset) {
// The last entry, if it exists, has a lower offset than us.
bytes.push((offset, entry.1));
} else {
// There already is an entry for this offset in there! This can happen when the
// start and end range checks actually end up hitting the same pointer, so we
// already added this in the "pointer at the start" part above.
assert!(entry.0 <= src.start);
}
}
} else {
trace!("no end overlapping entry");
}
trace!("byte provenances: {bytes:?}");
// And again a buffer for the new list on the target side.
let mut dest_bytes = Vec::with_capacity(bytes.len() * (count as usize));
for i in 0..count {
dest_bytes
.extend(bytes.iter().map(|&(offset, reloc)| (shift_offset(i, offset), reloc)));
}
debug_assert_eq!(dest_bytes.len(), dest_bytes.capacity());
dest_bytes_box = Some(dest_bytes.into_boxed_slice());
}
Ok(ProvenanceCopy { dest_ptrs: dest_ptrs_box, dest_bytes: dest_bytes_box })
}
/// Applies a provenance copy.
/// The affected range, as defined in the parameters to `prepare_copy` is expected
/// to be clear of provenance.
pub fn apply_copy(&mut self, copy: ProvenanceCopy<Prov>) {
if let Some(dest_ptrs) = copy.dest_ptrs {
self.ptrs.insert_presorted(dest_ptrs.into());
}
if Prov::OFFSET_IS_ADDR {
if let Some(dest_bytes) = copy.dest_bytes && !dest_bytes.is_empty() {
self.bytes.get_or_insert_with(Box::default).insert_presorted(dest_bytes.into());
}
} else {
debug_assert!(copy.dest_bytes.is_none());
}
}
}

19
compiler/rustc_middle/src/mir/interpret/allocation/tests.rs Normal file
View File

@ -0,0 +1,19 @@
use super::*;
#[test]
fn uninit_mask() {
let mut mask = InitMask::new(Size::from_bytes(500), false);
assert!(!mask.get(Size::from_bytes(499)));
mask.set_range(alloc_range(Size::from_bytes(499), Size::from_bytes(1)), true);
assert!(mask.get(Size::from_bytes(499)));
mask.set_range((100..256).into(), true);
for i in 0..100 {
assert!(!mask.get(Size::from_bytes(i)), "{i} should not be set");
}
for i in 100..256 {
assert!(mask.get(Size::from_bytes(i)), "{i} should be set");
}
for i in 256..499 {
assert!(!mask.get(Size::from_bytes(i)), "{i} should not be set");
}
}

13
compiler/rustc_middle/src/mir/interpret/error.rs
View File

@ -401,16 +401,15 @@ impl fmt::Display for UndefinedBehaviorInfo {
pub enum UnsupportedOpInfo {
/// Free-form case. Only for errors that are never caught!
Unsupported(String),
/// Overwriting parts of a pointer; the resulting state cannot be represented in our
/// `Allocation` data structure. See <https://github.com/rust-lang/miri/issues/2181>.
PartialPointerOverwrite(Pointer<AllocId>),
/// Attempting to `copy` parts of a pointer to somewhere else; the resulting state cannot be
/// represented in our `Allocation` data structure. See
/// <https://github.com/rust-lang/miri/issues/2181>.
PartialPointerCopy(Pointer<AllocId>),
//
// The variants below are only reachable from CTFE/const prop, miri will never emit them.
//
/// Overwriting parts of a pointer; without knowing absolute addresses, the resulting state
/// cannot be represented by the CTFE interpreter.
PartialPointerOverwrite(Pointer<AllocId>),
/// Attempting to `copy` parts of a pointer to somewhere else; without knowing absolute
/// addresses, the resulting state cannot be represented by the CTFE interpreter.
PartialPointerCopy(Pointer<AllocId>),
/// Encountered a pointer where we needed raw bytes.
ReadPointerAsBytes,
/// Accessing thread local statics

4
compiler/rustc_middle/src/mir/interpret/mod.rs
View File

@ -128,8 +128,8 @@ pub use self::error::{
pub use self::value::{get_slice_bytes, ConstAlloc, ConstValue, Scalar};
pub use self::allocation::{
alloc_range, AllocRange, Allocation, ConstAllocation, InitChunk, InitChunkIter, InitMask,
ProvenanceMap,
alloc_range, AllocError, AllocRange, AllocResult, Allocation, ConstAllocation, InitChunk,
InitChunkIter,
};
pub use self::pointer::{Pointer, PointerArithmetic, Provenance};

25
compiler/rustc_middle/src/mir/interpret/pointer.rs
View File

@ -103,8 +103,7 @@ impl<T: HasDataLayout> PointerArithmetic for T {}
/// This trait abstracts over the kind of provenance that is associated with a `Pointer`. It is
/// mostly opaque; the `Machine` trait extends it with some more operations that also have access to
/// some global state.
/// We don't actually care about this `Debug` bound (we use `Provenance::fmt` to format the entire
/// pointer), but `derive` adds some unnecessary bounds.
/// The `Debug` rendering is used to distplay bare provenance, and for the default impl of `fmt`.
pub trait Provenance: Copy + fmt::Debug {
/// Says whether the `offset` field of `Pointer`s with this provenance is the actual physical address.
/// - If `false`, the offset *must* be relative. This means the bytes representing a pointer are
@ -115,14 +114,23 @@ pub trait Provenance: Copy + fmt::Debug {
/// pointer, and implement ptr-to-int transmutation by stripping provenance.
const OFFSET_IS_ADDR: bool;
/// We also use this trait to control whether to abort execution when a pointer is being partially overwritten
/// (this avoids a separate trait in `allocation.rs` just for this purpose).
const ERR_ON_PARTIAL_PTR_OVERWRITE: bool;
/// Determines how a pointer should be printed.
///
/// Default impl is only good for when `OFFSET_IS_ADDR == true`.
fn fmt(ptr: &Pointer<Self>, f: &mut fmt::Formatter<'_>) -> fmt::Result
where
Self: Sized;
Self: Sized,
{
assert!(Self::OFFSET_IS_ADDR);
let (prov, addr) = ptr.into_parts(); // address is absolute
write!(f, "{:#x}", addr.bytes())?;
if f.alternate() {
write!(f, "{prov:#?}")?;
} else {
write!(f, "{prov:?}")?;
}
Ok(())
}
/// If `OFFSET_IS_ADDR == false`, provenance must always be able to
/// identify the allocation this ptr points to (i.e., this must return `Some`).
@ -139,9 +147,6 @@ impl Provenance for AllocId {
// so ptr-to-int casts are not possible (since we do not know the global physical offset).
const OFFSET_IS_ADDR: bool = false;
// For now, do not allow this, so that we keep our options open.
const ERR_ON_PARTIAL_PTR_OVERWRITE: bool = true;
fn fmt(ptr: &Pointer<Self>, f: &mut fmt::Formatter<'_>) -> fmt::Result {
// Forward `alternate` flag to `alloc_id` printing.
if f.alternate() {

40
compiler/rustc_middle/src/mir/pretty.rs
View File

@ -12,8 +12,8 @@ use rustc_data_structures::fx::FxHashMap;
use rustc_hir::def_id::DefId;
use rustc_index::vec::Idx;
use rustc_middle::mir::interpret::{
read_target_uint, AllocId, Allocation, ConstAllocation, ConstValue, GlobalAlloc, Pointer,
Provenance,
alloc_range, read_target_uint, AllocId, Allocation, ConstAllocation, ConstValue, GlobalAlloc,
Pointer, Provenance,
};
use rustc_middle::mir::visit::Visitor;
use rustc_middle::mir::MirSource;
@ -685,7 +685,7 @@ pub fn write_allocations<'tcx>(
fn alloc_ids_from_alloc(
alloc: ConstAllocation<'_>,
) -> impl DoubleEndedIterator<Item = AllocId> + '_ {
alloc.inner().provenance().values().map(|id| *id)
alloc.inner().provenance().ptrs().values().map(|id| *id)
}
fn alloc_ids_from_const_val(val: ConstValue<'_>) -> impl Iterator<Item = AllocId> + '_ {
@ -788,7 +788,7 @@ pub fn write_allocations<'tcx>(
/// After the hex dump, an ascii dump follows, replacing all unprintable characters (control
/// characters or characters whose value is larger than 127) with a `.`
/// This also prints provenance adequately.
pub fn display_allocation<'a, 'tcx, Prov, Extra>(
pub fn display_allocation<'a, 'tcx, Prov: Provenance, Extra>(
tcx: TyCtxt<'tcx>,
alloc: &'a Allocation<Prov, Extra>,
) -> RenderAllocation<'a, 'tcx, Prov, Extra> {
@ -796,7 +796,7 @@ pub fn display_allocation<'a, 'tcx, Prov, Extra>(
}
#[doc(hidden)]
pub struct RenderAllocation<'a, 'tcx, Prov, Extra> {
pub struct RenderAllocation<'a, 'tcx, Prov: Provenance, Extra> {
tcx: TyCtxt<'tcx>,
alloc: &'a Allocation<Prov, Extra>,
}
@ -882,9 +882,9 @@ fn write_allocation_bytes<'tcx, Prov: Provenance, Extra>(
if i != line_start {
write!(w, " ")?;
}
if let Some(&prov) = alloc.provenance().get(&i) {
if let Some(prov) = alloc.provenance().get_ptr(i) {
// Memory with provenance must be defined
assert!(alloc.init_mask().is_range_initialized(i, i + ptr_size).is_ok());
assert!(alloc.init_mask().is_range_initialized(alloc_range(i, ptr_size)).is_ok());
let j = i.bytes_usize();
let offset = alloc
.inspect_with_uninit_and_ptr_outside_interpreter(j..j + ptr_size.bytes_usize());
@ -904,9 +904,9 @@ fn write_allocation_bytes<'tcx, Prov: Provenance, Extra>(
let overflow = ptr_size - remainder;
let remainder_width = provenance_width(remainder.bytes_usize()) - 2;
let overflow_width = provenance_width(overflow.bytes_usize() - 1) + 1;
ascii.push('╾');
for _ in 0..remainder.bytes() - 1 {
ascii.push('─');
ascii.push('╾'); // HEAVY LEFT AND LIGHT RIGHT
for _ in 1..remainder.bytes() {
ascii.push('─'); // LIGHT HORIZONTAL
}
if overflow_width > remainder_width && overflow_width >= target.len() {
// The case where the provenance fits into the part in the next line
@ -926,7 +926,7 @@ fn write_allocation_bytes<'tcx, Prov: Provenance, Extra>(
for _ in 0..overflow.bytes() - 1 {
ascii.push('─');
}
ascii.push('╼');
ascii.push('╼'); // LIGHT LEFT AND HEAVY RIGHT
i += ptr_size;
continue;
} else {
@ -941,7 +941,23 @@ fn write_allocation_bytes<'tcx, Prov: Provenance, Extra>(
ascii.push('╼');
i += ptr_size;
}
} else if alloc.init_mask().is_range_initialized(i, i + Size::from_bytes(1)).is_ok() {
} else if let Some(prov) = alloc.provenance().get(i, &tcx) {
// Memory with provenance must be defined
assert!(
alloc.init_mask().is_range_initialized(alloc_range(i, Size::from_bytes(1))).is_ok()
);
ascii.push('━'); // HEAVY HORIZONTAL
// We have two characters to display this, which is obviously not enough.
// Format is similar to "oversized" above.
let j = i.bytes_usize();
let c = alloc.inspect_with_uninit_and_ptr_outside_interpreter(j..j + 1)[0];
write!(w, "╾{:02x}{:#?} (1 ptr byte)╼", c, prov)?;
i += Size::from_bytes(1);
} else if alloc
.init_mask()
.is_range_initialized(alloc_range(i, Size::from_bytes(1)))
.is_ok()
{
let j = i.bytes_usize();
// Checked definedness (and thus range) and provenance. This access also doesn't

13
compiler/rustc_middle/src/ty/impls_ty.rs
View File

@ -112,19 +112,6 @@ impl<'a> HashStable<StableHashingContext<'a>> for mir::interpret::AllocId {
}
}
// `Relocations` with default type parameters is a sorted map.
impl<'a, Prov> HashStable<StableHashingContext<'a>> for mir::interpret::ProvenanceMap<Prov>
where
Prov: HashStable<StableHashingContext<'a>>,
{
fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
self.len().hash_stable(hcx, hasher);
for reloc in self.iter() {
reloc.hash_stable(hcx, hasher);
}
}
}
impl<'a> ToStableHashKey<StableHashingContext<'a>> for region::Scope {
type KeyType = region::Scope;

2
compiler/rustc_mir_transform/src/const_prop.rs
View File

@ -266,7 +266,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for ConstPropMachine<'mir, 'tcx>
_tcx: TyCtxt<'tcx>,
_machine: &Self,
_alloc_id: AllocId,
alloc: ConstAllocation<'tcx, Self::Provenance, Self::AllocExtra>,
alloc: ConstAllocation<'tcx>,
_static_def_id: Option<DefId>,
is_write: bool,
) -> InterpResult<'tcx> {

6
compiler/rustc_monomorphize/src/collector.rs
View File

@ -456,7 +456,7 @@ fn collect_items_rec<'tcx>(
recursion_depth_reset = None;
if let Ok(alloc) = tcx.eval_static_initializer(def_id) {
for &id in alloc.inner().provenance().values() {
for &id in alloc.inner().provenance().ptrs().values() {
collect_miri(tcx, id, &mut neighbors);
}
}
@ -1404,7 +1404,7 @@ fn collect_miri<'tcx>(tcx: TyCtxt<'tcx>, alloc_id: AllocId, output: &mut MonoIte
}
GlobalAlloc::Memory(alloc) => {
trace!("collecting {:?} with {:#?}", alloc_id, alloc);
for &inner in alloc.inner().provenance().values() {
for &inner in alloc.inner().provenance().ptrs().values() {
rustc_data_structures::stack::ensure_sufficient_stack(|| {
collect_miri(tcx, inner, output);
});
@ -1443,7 +1443,7 @@ fn collect_const_value<'tcx>(
match value {
ConstValue::Scalar(Scalar::Ptr(ptr, _size)) => collect_miri(tcx, ptr.provenance, output),
ConstValue::Slice { data: alloc, start: _, end: _ } | ConstValue::ByRef { alloc, .. } => {
for &id in alloc.inner().provenance().values() {
for &id in alloc.inner().provenance().ptrs().values() {
collect_miri(tcx, id, output);
}
}

5
library/core/src/mem/mod.rs
View File

@ -725,10 +725,7 @@ pub const fn swap<T>(x: &mut T, y: &mut T) {
// understanding `mem::replace`, `Option::take`, etc. - a better overall
// solution might be to make `ptr::swap_nonoverlapping` into an intrinsic, which
// a backend can choose to implement using the block optimization, or not.
// NOTE(scottmcm) MIRI is disabled here as reading in smaller units is a
// pessimization for it. Also, if the type contains any unaligned pointers,
// copying those over multiple reads is difficult to support.
#[cfg(not(any(target_arch = "spirv", miri)))]
#[cfg(not(any(target_arch = "spirv")))]
{
// For types that are larger multiples of their alignment, the simple way
// tends to copy the whole thing to stack rather than doing it one part

22
library/core/src/ptr/mod.rs
View File

@ -908,21 +908,15 @@ pub const unsafe fn swap_nonoverlapping<T>(x: *mut T, y: *mut T, count: usize) {
);
}
// NOTE(scottmcm) Miri is disabled here as reading in smaller units is a
// pessimization for it. Also, if the type contains any unaligned pointers,
// copying those over multiple reads is difficult to support.
#[cfg(not(miri))]
// Split up the slice into small power-of-two-sized chunks that LLVM is able
// to vectorize (unless it's a special type with more-than-pointer alignment,
// because we don't want to pessimize things like slices of SIMD vectors.)
if mem::align_of::<T>() <= mem::size_of::<usize>()
&& (!mem::size_of::<T>().is_power_of_two()
|| mem::size_of::<T>() > mem::size_of::<usize>() * 2)
{
// Split up the slice into small power-of-two-sized chunks that LLVM is able
// to vectorize (unless it's a special type with more-than-pointer alignment,
// because we don't want to pessimize things like slices of SIMD vectors.)
if mem::align_of::<T>() <= mem::size_of::<usize>()
&& (!mem::size_of::<T>().is_power_of_two()
|| mem::size_of::<T>() > mem::size_of::<usize>() * 2)
{
attempt_swap_as_chunks!(usize);
attempt_swap_as_chunks!(u8);
}
attempt_swap_as_chunks!(usize);
attempt_swap_as_chunks!(u8);
}
// SAFETY: Same preconditions as this function

28
src/test/ui-fulldeps/uninit_mask.rs
View File

@ -1,28 +0,0 @@
// run-pass
// ignore-cross-compile
// ignore-stage1
#![feature(rustc_private)]
extern crate rustc_middle;
extern crate rustc_target;
use rustc_middle::mir::interpret::InitMask;
use rustc_target::abi::Size;
fn main() {
let mut mask = InitMask::new(Size::from_bytes(500), false);
assert!(!mask.get(Size::from_bytes(499)));
mask.set(Size::from_bytes(499), true);
assert!(mask.get(Size::from_bytes(499)));
mask.set_range_inbounds(Size::from_bytes(100), Size::from_bytes(256), true);
for i in 0..100 {
assert!(!mask.get(Size::from_bytes(i)));
}
for i in 100..256 {
assert!(mask.get(Size::from_bytes(i)));
}
for i in 256..499 {
assert!(!mask.get(Size::from_bytes(i)));
}
}

6
src/tools/miri/src/diagnostics.rs
View File

@ -229,13 +229,13 @@ pub fn report_error<'tcx, 'mir>(
Unsupported(
UnsupportedOpInfo::ThreadLocalStatic(_) |
UnsupportedOpInfo::ReadExternStatic(_) |
UnsupportedOpInfo::PartialPointerOverwrite(_) | // we make memory uninit instead
UnsupportedOpInfo::PartialPointerOverwrite(_) |
UnsupportedOpInfo::PartialPointerCopy(_) |
UnsupportedOpInfo::ReadPointerAsBytes
) =>
panic!("Error should never be raised by Miri: {kind:?}", kind = e.kind()),
Unsupported(
UnsupportedOpInfo::Unsupported(_) |
UnsupportedOpInfo::PartialPointerCopy(_)
UnsupportedOpInfo::Unsupported(_)
) =>
vec![(None, format!("this is likely not a bug in the program; it indicates that the program performed an operation that the interpreter does not support"))],
UndefinedBehavior(UndefinedBehaviorInfo::AlignmentCheckFailed { .. })

23
src/tools/miri/src/machine.rs
View File

@ -133,7 +133,7 @@ impl fmt::Display for MiriMemoryKind {
}
/// Pointer provenance.
#[derive(Debug, Clone, Copy)]
#[derive(Clone, Copy)]
pub enum Provenance {
Concrete {
alloc_id: AllocId,
@ -176,18 +176,9 @@ static_assert_size!(Pointer<Provenance>, 24);
#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
static_assert_size!(Scalar<Provenance>, 32);
impl interpret::Provenance for Provenance {
/// We use absolute addresses in the `offset` of a `Pointer<Provenance>`.
const OFFSET_IS_ADDR: bool = true;
/// We cannot err on partial overwrites, it happens too often in practice (due to unions).
const ERR_ON_PARTIAL_PTR_OVERWRITE: bool = false;
fn fmt(ptr: &Pointer<Self>, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let (prov, addr) = ptr.into_parts(); // address is absolute
write!(f, "{:#x}", addr.bytes())?;
match prov {
impl fmt::Debug for Provenance {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
Provenance::Concrete { alloc_id, sb } => {
// Forward `alternate` flag to `alloc_id` printing.
if f.alternate() {
@ -202,9 +193,13 @@ impl interpret::Provenance for Provenance {
write!(f, "[wildcard]")?;
}
}
Ok(())
}
}
impl interpret::Provenance for Provenance {
/// We use absolute addresses in the `offset` of a `Pointer<Provenance>`.
const OFFSET_IS_ADDR: bool = true;
fn get_alloc_id(self) -> Option<AllocId> {
match self {

2
src/tools/miri/src/tag_gc.rs
View File

@ -127,7 +127,7 @@ impl VisitTags for Operand<Provenance> {
impl VisitTags for Allocation<Provenance, AllocExtra> {
fn visit_tags(&self, visit: &mut dyn FnMut(SbTag)) {
for (_size, prov) in self.provenance().iter() {
for prov in self.provenance().provenances() {
prov.visit_tags(visit);
}

21
src/tools/miri/tests/fail/copy_half_a_pointer.rs
View File

@ -1,21 +0,0 @@
//@normalize-stderr-test: "\+0x[48]" -> "+HALF_PTR"
#![allow(dead_code)]
// We use packed structs to get around alignment restrictions
#[repr(packed)]
struct Data {
pad: u8,
ptr: &'static i32,
}
static G: i32 = 0;
fn main() {
let mut d = Data { pad: 0, ptr: &G };
// Get a pointer to the beginning of the Data struct (one u8 byte, then the pointer bytes).
let d_alias = &mut d as *mut _ as *mut *const u8;
unsafe {
let _x = d_alias.read_unaligned(); //~ERROR: unable to copy parts of a pointer
}
}

14
src/tools/miri/tests/fail/copy_half_a_pointer.stderr
View File

@ -1,14 +0,0 @@
error: unsupported operation: unable to copy parts of a pointer from memory at ALLOC+HALF_PTR
--> $DIR/copy_half_a_pointer.rs:LL:CC
|
LL | let _x = d_alias.read_unaligned();
| ^^^^^^^^^^^^^^^^^^^^^^^^ unable to copy parts of a pointer from memory at ALLOC+HALF_PTR
|
= help: this is likely not a bug in the program; it indicates that the program performed an operation that the interpreter does not support
= note: BACKTRACE:
= note: inside `main` at $DIR/copy_half_a_pointer.rs:LL:CC
note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
error: aborting due to previous error

7
src/tools/miri/tests/fail/pointer_partial_overwrite.rs → src/tools/miri/tests/fail/provenance/pointer_partial_overwrite.rs
View File

@ -2,16 +2,13 @@
//@compile-flags: -Zmiri-disable-alignment-check -Zmiri-disable-stacked-borrows -Zmiri-disable-validation
// Test what happens when we overwrite parts of a pointer.
// Also see <https://github.com/rust-lang/miri/issues/2181>.
fn main() {
let mut p = &42;
unsafe {
let ptr: *mut _ = &mut p;
*(ptr as *mut u8) = 123; // if we ever support 8 bit pointers, this is gonna cause
// "attempted to interpret some raw bytes as a pointer address" instead of
// "attempted to read undefined bytes"
*(ptr as *mut u8) = 123; // this removes provenance from one of the bytes, meaning the entire ptr is considered to have no provenance.
}
let x = *p; //~ ERROR: this operation requires initialized memory
let x = *p; //~ ERROR: no provenance
panic!("this should never print: {}", x);
}

4
src/tools/miri/tests/fail/pointer_partial_overwrite.stderr → src/tools/miri/tests/fail/provenance/pointer_partial_overwrite.stderr
View File

@ -1,8 +1,8 @@
error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
error: Undefined Behavior: dereferencing pointer failed: $HEX[noalloc] is a dangling pointer (it has no provenance)
--> $DIR/pointer_partial_overwrite.rs:LL:CC
|
LL | let x = *p;
| ^^ using uninitialized data, but this operation requires initialized memory
| ^^ dereferencing pointer failed: $HEX[noalloc] is a dangling pointer (it has no provenance)
|
= help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
= help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information

32
src/tools/miri/tests/fail/uninit_buffer_with_provenance.rs Normal file
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//@error-pattern: memory is uninitialized at [0x4..0x8]
//@normalize-stderr-test: "a[0-9]+" -> "ALLOC"
#![feature(strict_provenance)]
// Test printing allocations that contain single-byte provenance.
use std::alloc::{alloc, dealloc, Layout};
use std::mem::{self, MaybeUninit};
use std::slice::from_raw_parts;
fn byte_with_provenance<T>(val: u8, prov: *const T) -> MaybeUninit<u8> {
let ptr = prov.with_addr(val as usize);
let bytes: [MaybeUninit<u8>; mem::size_of::<*const ()>()] = unsafe { mem::transmute(ptr) };
let lsb = if cfg!(target_endian = "little") { 0 } else { bytes.len() - 1 };
bytes[lsb]
}
fn main() {
let layout = Layout::from_size_align(16, 8).unwrap();
unsafe {
let ptr = alloc(layout);
let ptr_raw = ptr.cast::<MaybeUninit<u8>>();
*ptr_raw.add(0) = byte_with_provenance(0x42, &42u8);
*ptr.add(1) = 0x12;
*ptr.add(2) = 0x13;
*ptr_raw.add(3) = byte_with_provenance(0x43, &0u8);
let slice1 = from_raw_parts(ptr, 8);
let slice2 = from_raw_parts(ptr.add(8), 8);
drop(slice1.cmp(slice2));
dealloc(ptr, layout);
}
}

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src/tools/miri/tests/fail/uninit_buffer_with_provenance.stderr Normal file
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error: Undefined Behavior: reading memory at ALLOC[0x0..0x8], but memory is uninitialized at [0x4..0x8], and this operation requires initialized memory
--> RUSTLIB/core/src/slice/cmp.rs:LL:CC
|
LL | let mut order = unsafe { memcmp(left.as_ptr(), right.as_ptr(), len) as isize };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ reading memory at ALLOC[0x0..0x8], but memory is uninitialized at [0x4..0x8], and this operation requires initialized memory
|
= help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
= help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
= note: BACKTRACE:
= note: inside `<u8 as core::slice::cmp::SliceOrd>::compare` at RUSTLIB/core/src/slice/cmp.rs:LL:CC
= note: inside `core::slice::cmp::<impl std::cmp::Ord for [u8]>::cmp` at RUSTLIB/core/src/slice/cmp.rs:LL:CC
note: inside `main` at $DIR/uninit_buffer_with_provenance.rs:LL:CC
--> $DIR/uninit_buffer_with_provenance.rs:LL:CC
|
LL | drop(slice1.cmp(slice2));
| ^^^^^^^^^^^^^^^^^^
note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
Uninitialized memory occurred at ALLOC[0x4..0x8], in this allocation:
ALLOC (Rust heap, size: 16, align: 8) {
╾42[ALLOC]<TAG> (1 ptr byte)╼ 12 13 ╾43[ALLOC]<TAG> (1 ptr byte)╼ __ __ __ __ __ __ __ __ __ __ __ __ │ ━..━░░░░░░░░░░░░
}
ALLOC (global (static or const), size: 1, align: 1) {
2a │ *
}
ALLOC (global (static or const), size: 1, align: 1) {
00 │ .
}
error: aborting due to previous error

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src/tools/miri/tests/pass/provenance.rs Normal file
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#![feature(strict_provenance)]
#![feature(pointer_byte_offsets)]
use std::{mem, ptr};
const PTR_SIZE: usize = mem::size_of::<&i32>();
fn main() {
basic();
partial_overwrite_then_restore();
bytewise_ptr_methods();
bytewise_custom_memcpy();
bytewise_custom_memcpy_chunked();
}
/// Some basic smoke tests for provenance.
fn basic() {
let x = &42;
let ptr = x as *const i32;
let addr: usize = unsafe { mem::transmute(ptr) }; // an integer without provenance
// But we can give provenance back via `with_addr`.
let ptr_back = ptr.with_addr(addr);
assert_eq!(unsafe { *ptr_back }, 42);
// It is preserved by MaybeUninit.
let addr_mu: mem::MaybeUninit<usize> = unsafe { mem::transmute(ptr) };
let ptr_back: *const i32 = unsafe { mem::transmute(addr_mu) };
assert_eq!(unsafe { *ptr_back }, 42);
}
/// Overwrite one byte of a pointer, then restore it.
fn partial_overwrite_then_restore() {
unsafe fn ptr_bytes<'x>(ptr: &'x mut *const i32) -> &'x mut [mem::MaybeUninit<u8>; PTR_SIZE] {
mem::transmute(ptr)
}
// Returns a value with the same provenance as `x` but 0 for the integer value.
// `x` must be initialized.
unsafe fn zero_with_provenance(x: mem::MaybeUninit<u8>) -> mem::MaybeUninit<u8> {
let ptr = [x; PTR_SIZE];
let ptr: *const i32 = mem::transmute(ptr);
let mut ptr = ptr.with_addr(0);
ptr_bytes(&mut ptr)[0]
}
unsafe {
let ptr = &42;
let mut ptr = ptr as *const i32;
// Get a bytewise view of the pointer.
let ptr_bytes = ptr_bytes(&mut ptr);
// The highest bytes must be 0 for this to work.
let hi = if cfg!(target_endian = "little") { ptr_bytes.len() - 1 } else { 0 };
assert_eq!(*ptr_bytes[hi].as_ptr().cast::<u8>(), 0);
// Overwrite provenance on the last byte.
ptr_bytes[hi] = mem::MaybeUninit::new(0);
// Restore it from the another byte.
ptr_bytes[hi] = zero_with_provenance(ptr_bytes[1]);
// Now ptr should be good again.
assert_eq!(*ptr, 42);
}
}
fn bytewise_ptr_methods() {
let mut ptr1 = &1;
let mut ptr2 = &2;
// Swap them, bytewise.
unsafe {
ptr::swap_nonoverlapping(
&mut ptr1 as *mut _ as *mut mem::MaybeUninit<u8>,
&mut ptr2 as *mut _ as *mut mem::MaybeUninit<u8>,
mem::size_of::<&i32>(),
);
}
// Make sure they still work.
assert_eq!(*ptr1, 2);
assert_eq!(*ptr2, 1);
// TODO: also test ptr::swap, ptr::copy, ptr::copy_nonoverlapping.
}
fn bytewise_custom_memcpy() {
unsafe fn memcpy<T>(to: *mut T, from: *const T) {
let to = to.cast::<mem::MaybeUninit<u8>>();
let from = from.cast::<mem::MaybeUninit<u8>>();
for i in 0..mem::size_of::<T>() {
let b = from.add(i).read();
to.add(i).write(b);
}
}
let ptr1 = &1;
let mut ptr2 = &2;
// Copy, bytewise.
unsafe { memcpy(&mut ptr2, &ptr1) };
// Make sure they still work.
assert_eq!(*ptr1, 1);
assert_eq!(*ptr2, 1);
}
fn bytewise_custom_memcpy_chunked() {
unsafe fn memcpy<T>(to: *mut T, from: *const T) {
assert!(mem::size_of::<T>() % mem::size_of::<usize>() == 0);
let count = mem::size_of::<T>() / mem::size_of::<usize>();
let to = to.cast::<mem::MaybeUninit<usize>>();
let from = from.cast::<mem::MaybeUninit<usize>>();
for i in 0..count {
let b = from.add(i).read();
to.add(i).write(b);
}
}
// Prepare an array where pointers are stored at... interesting... offsets.
let mut data = [0usize; 2 * PTR_SIZE];
let mut offsets = vec![];
for i in 0..mem::size_of::<usize>() {
// We have 2*PTR_SIZE room for each of these pointers.
let base = i * 2 * PTR_SIZE;
// This one is mis-aligned by `i`.
let offset = base + i;
offsets.push(offset);
// Store it there.
unsafe { data.as_mut_ptr().byte_add(offset).cast::<&i32>().write_unaligned(&42) };
}
// Now memcpy that.
let mut data2 = [0usize; 2 * PTR_SIZE];
unsafe { memcpy(&mut data2, &data) };
// And check the result.
for &offset in &offsets {
let ptr = unsafe { data2.as_ptr().byte_add(offset).cast::<&i32>().read_unaligned() };
assert_eq!(*ptr, 42);
}
}