use std::cell::RefCell;
+use std::cmp::max;
use std::collections::hash_map::Entry;
use log::trace;
use rand::Rng;
-use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_span::Span;
use rustc_target::abi::{HasDataLayout, Size};
use crate::*;
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum ProvenanceMode {
+ /// We support `expose_addr`/`from_exposed_addr` via "wildcard" provenance.
+ /// However, we want on `from_exposed_addr` to alert the user of the precision loss.
+ Default,
+ /// Like `Default`, but without the warning.
+ Permissive,
+ /// We error on `from_exposed_addr`, ensuring no precision loss.
+ Strict,
+}
+
pub type GlobalState = RefCell<GlobalStateInner>;
#[derive(Clone, Debug)]
/// they do not have an `AllocExtra`.
/// This is the inverse of `int_to_ptr_map`.
base_addr: FxHashMap<AllocId, u64>,
+ /// Whether an allocation has been exposed or not. This cannot be put
+ /// into `AllocExtra` for the same reason as `base_addr`.
+ exposed: FxHashSet<AllocId>,
/// This is used as a memory address when a new pointer is casted to an integer. It
/// is always larger than any address that was previously made part of a block.
next_base_addr: u64,
- /// Whether to enforce "strict provenance" rules. Enabling this means int2ptr casts return
- /// pointers with an invalid provenance, i.e., not valid for any memory access.
- strict_provenance: bool,
+ /// The provenance to use for int2ptr casts
+ provenance_mode: ProvenanceMode,
}
impl GlobalStateInner {
GlobalStateInner {
int_to_ptr_map: Vec::default(),
base_addr: FxHashMap::default(),
+ exposed: FxHashSet::default(),
next_base_addr: STACK_ADDR,
- strict_provenance: config.strict_provenance,
+ provenance_mode: config.provenance_mode,
}
}
}
impl<'mir, 'tcx> GlobalStateInner {
- pub fn ptr_from_addr(addr: u64, ecx: &MiriEvalContext<'mir, 'tcx>) -> Pointer<Option<Tag>> {
- trace!("Casting 0x{:x} to a pointer", addr);
+ // Returns the exposed `AllocId` that corresponds to the specified addr,
+ // or `None` if the addr is out of bounds
+ fn alloc_id_from_addr(ecx: &MiriEvalContext<'mir, 'tcx>, addr: u64) -> Option<AllocId> {
let global_state = ecx.machine.intptrcast.borrow();
-
- if global_state.strict_provenance {
- return Pointer::new(None, Size::from_bytes(addr));
- }
+ assert!(global_state.provenance_mode != ProvenanceMode::Strict);
let pos = global_state.int_to_ptr_map.binary_search_by_key(&addr, |(addr, _)| *addr);
+
+ // Determine the in-bounds provenance for this pointer.
+ // (This is only called on an actual access, so in-bounds is the only possible kind of provenance.)
let alloc_id = match pos {
Ok(pos) => Some(global_state.int_to_ptr_map[pos].1),
Err(0) => None,
// This never overflows because `addr >= glb`
let offset = addr - glb;
// If the offset exceeds the size of the allocation, don't use this `alloc_id`.
- if offset
- <= ecx
- .get_alloc_size_and_align(alloc_id, AllocCheck::MaybeDead)
- .unwrap()
- .0
- .bytes()
- {
- Some(alloc_id)
- } else {
- None
+ let size = ecx.get_alloc_info(alloc_id).0;
+ if offset <= size.bytes() { Some(alloc_id) } else { None }
+ }
+ }?;
+
+ // We only use this provenance if it has been exposed, *and* is still live.
+ if global_state.exposed.contains(&alloc_id) {
+ let (_size, _align, kind) = ecx.get_alloc_info(alloc_id);
+ match kind {
+ AllocKind::LiveData | AllocKind::Function | AllocKind::VTable => {
+ return Some(alloc_id);
}
+ AllocKind::Dead => {}
}
- };
- // Pointers created from integers are untagged.
- Pointer::new(
- alloc_id.map(|alloc_id| Tag { alloc_id, sb: SbTag::Untagged }),
- Size::from_bytes(addr),
- )
+ }
+
+ None
+ }
+
+ pub fn expose_ptr(
+ ecx: &mut MiriEvalContext<'mir, 'tcx>,
+ alloc_id: AllocId,
+ sb: SbTag,
+ ) -> InterpResult<'tcx> {
+ let global_state = ecx.machine.intptrcast.get_mut();
+ // In strict mode, we don't need this, so we can save some cycles by not tracking it.
+ if global_state.provenance_mode != ProvenanceMode::Strict {
+ trace!("Exposing allocation id {alloc_id:?}");
+ global_state.exposed.insert(alloc_id);
+ if ecx.machine.stacked_borrows.is_some() {
+ ecx.expose_tag(alloc_id, sb)?;
+ }
+ }
+ Ok(())
+ }
+
+ pub fn ptr_from_addr_transmute(
+ _ecx: &MiriEvalContext<'mir, 'tcx>,
+ addr: u64,
+ ) -> Pointer<Option<Provenance>> {
+ trace!("Transmuting {:#x} to a pointer", addr);
+
+ // We consider transmuted pointers to be "invalid" (`None` provenance).
+ Pointer::new(None, Size::from_bytes(addr))
+ }
+
+ pub fn ptr_from_addr_cast(
+ ecx: &MiriEvalContext<'mir, 'tcx>,
+ addr: u64,
+ ) -> InterpResult<'tcx, Pointer<Option<Provenance>>> {
+ trace!("Casting {:#x} to a pointer", addr);
+
+ let global_state = ecx.machine.intptrcast.borrow();
+
+ match global_state.provenance_mode {
+ ProvenanceMode::Default => {
+ // The first time this happens at a particular location, print a warning.
+ thread_local! {
+ // `Span` is non-`Send`, so we use a thread-local instead.
+ static PAST_WARNINGS: RefCell<FxHashSet<Span>> = RefCell::default();
+ }
+ PAST_WARNINGS.with_borrow_mut(|past_warnings| {
+ let first = past_warnings.is_empty();
+ if past_warnings.insert(ecx.cur_span()) {
+ // Newly inserted, so first time we see this span.
+ register_diagnostic(NonHaltingDiagnostic::Int2Ptr { details: first });
+ }
+ });
+ }
+ ProvenanceMode::Strict => {
+ throw_machine_stop!(TerminationInfo::Int2PtrWithStrictProvenance);
+ }
+ ProvenanceMode::Permissive => {}
+ }
+
+ // This is how wildcard pointers are born.
+ Ok(Pointer::new(Some(Provenance::Wildcard), Size::from_bytes(addr)))
}
fn alloc_base_addr(ecx: &MiriEvalContext<'mir, 'tcx>, alloc_id: AllocId) -> u64 {
Entry::Occupied(entry) => *entry.get(),
Entry::Vacant(entry) => {
// There is nothing wrong with a raw pointer being cast to an integer only after
- // it became dangling. Hence `MaybeDead`.
- let (size, align) =
- ecx.get_alloc_size_and_align(alloc_id, AllocCheck::MaybeDead).unwrap();
+ // it became dangling. Hence we allow dead allocations.
+ let (size, align, _kind) = ecx.get_alloc_info(alloc_id);
// This allocation does not have a base address yet, pick one.
// Leave some space to the previous allocation, to give it some chance to be less aligned.
slack,
);
- // Remember next base address. Leave a gap of at least 1 to avoid two zero-sized allocations
- // having the same base address, and to avoid ambiguous provenance for the address between two
- // allocations (also see https://github.com/rust-lang/unsafe-code-guidelines/issues/313).
- let size_plus_1 = size.bytes().checked_add(1).unwrap();
- global_state.next_base_addr = base_addr.checked_add(size_plus_1).unwrap();
+ // Remember next base address. If this allocation is zero-sized, leave a gap
+ // of at least 1 to avoid two allocations having the same base address.
+ // (The logic in `alloc_id_from_addr` assumes unique addresses, and different
+ // function/vtable pointers need to be distinguishable!)
+ global_state.next_base_addr = base_addr.checked_add(max(size.bytes(), 1)).unwrap();
// Given that `next_base_addr` increases in each allocation, pushing the
// corresponding tuple keeps `int_to_ptr_map` sorted
global_state.int_to_ptr_map.push((base_addr, alloc_id));
dl.overflowing_offset(base_addr, offset.bytes()).0
}
- pub fn abs_ptr_to_rel(ecx: &MiriEvalContext<'mir, 'tcx>, ptr: Pointer<Tag>) -> Size {
+ /// When a pointer is used for a memory access, this computes where in which allocation the
+ /// access is going.
+ pub fn abs_ptr_to_rel(
+ ecx: &MiriEvalContext<'mir, 'tcx>,
+ ptr: Pointer<Provenance>,
+ ) -> Option<(AllocId, Size)> {
let (tag, addr) = ptr.into_parts(); // addr is absolute (Tag provenance)
- let base_addr = GlobalStateInner::alloc_base_addr(ecx, tag.alloc_id);
+
+ let alloc_id = if let Provenance::Concrete { alloc_id, .. } = tag {
+ alloc_id
+ } else {
+ // A wildcard pointer.
+ GlobalStateInner::alloc_id_from_addr(ecx, addr.bytes())?
+ };
+
+ let base_addr = GlobalStateInner::alloc_base_addr(ecx, alloc_id);
// Wrapping "addr - base_addr"
let dl = ecx.data_layout();
let neg_base_addr = (base_addr as i64).wrapping_neg();
- Size::from_bytes(dl.overflowing_signed_offset(addr.bytes(), neg_base_addr).0)
+ Some((
+ alloc_id,
+ Size::from_bytes(dl.overflowing_signed_offset(addr.bytes(), neg_base_addr).0),
+ ))
}
/// Shifts `addr` to make it aligned with `align` by rounding `addr` to the smallest multiple
projects / rust.git / blobdiff