use std::cell::RefCell;
+use std::cmp::max;
+use std::collections::hash_map::Entry;
-use rustc::mir::interpret::AllocId;
+use log::trace;
+use rand::Rng;
-pub type MemoryState = RefCell<GlobalState>;
+use rustc_data_structures::fx::FxHashMap;
+use rustc_target::abi::{Size, HasDataLayout};
+
+use crate::*;
+
+pub type MemoryExtra = RefCell<GlobalState>;
#[derive(Clone, Debug)]
pub struct GlobalState {
- pub vec: Vec<(u64, AllocId)>,
- pub addr: u64,
+ /// This is used as a map between the address of each allocation and its `AllocId`.
+ /// It is always sorted
+ pub int_to_ptr_map: Vec<(u64, AllocId)>,
+ /// The base address for each allocation. We cannot put that into
+ /// `AllocExtra` because function pointers also have a base address, and
+ /// they do not have an `AllocExtra`.
+ /// This is the inverse of `int_to_ptr_map`.
+ pub base_addr: FxHashMap<AllocId, u64>,
+ /// 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.
+ pub next_base_addr: u64,
}
impl Default for GlobalState {
fn default() -> Self {
GlobalState {
- vec: Vec::default(),
- addr: 2u64.pow(16)
+ int_to_ptr_map: Vec::default(),
+ base_addr: FxHashMap::default(),
+ next_base_addr: STACK_ADDR,
+ }
+ }
+}
+
+impl<'mir, 'tcx> GlobalState {
+ pub fn int_to_ptr(
+ int: u64,
+ memory: &Memory<'mir, 'tcx, Evaluator<'mir, 'tcx>>,
+ ) -> InterpResult<'tcx, Pointer<Tag>> {
+ let global_state = memory.extra.intptrcast.borrow();
+ let pos = global_state.int_to_ptr_map.binary_search_by_key(&int, |(addr, _)| *addr);
+
+ // The int must be in-bounds after being cast to a pointer, so we error
+ // with `CheckInAllocMsg::InboundsTest`.
+ Ok(match pos {
+ Ok(pos) => {
+ let (_, alloc_id) = global_state.int_to_ptr_map[pos];
+ // `int` is equal to the starting address for an allocation, the offset should be
+ // zero. The pointer is untagged because it was created from a cast
+ Pointer::new_with_tag(alloc_id, Size::from_bytes(0), Tag::Untagged)
+ }
+ Err(0) => throw_ub!(DanglingIntPointer(int, CheckInAllocMsg::InboundsTest)),
+ Err(pos) => {
+ // This is the largest of the adresses smaller than `int`,
+ // i.e. the greatest lower bound (glb)
+ let (glb, alloc_id) = global_state.int_to_ptr_map[pos - 1];
+ // This never overflows because `int >= glb`
+ let offset = int - glb;
+ // If the offset exceeds the size of the allocation, this access is illegal
+ if offset <= memory.get_size_and_align(alloc_id, AllocCheck::MaybeDead)?.0.bytes() {
+ // This pointer is untagged because it was created from a cast
+ Pointer::new_with_tag(alloc_id, Size::from_bytes(offset), Tag::Untagged)
+ } else {
+ throw_ub!(DanglingIntPointer(int, CheckInAllocMsg::InboundsTest))
+ }
+ }
+ })
+ }
+
+ pub fn ptr_to_int(
+ ptr: Pointer<Tag>,
+ memory: &Memory<'mir, 'tcx, Evaluator<'mir, 'tcx>>,
+ ) -> InterpResult<'tcx, u64> {
+ let mut global_state = memory.extra.intptrcast.borrow_mut();
+ let global_state = &mut *global_state;
+ let id = ptr.alloc_id;
+
+ // There is nothing wrong with a raw pointer being cast to an integer only after
+ // it became dangling. Hence `MaybeDead`.
+ let (size, align) = memory.get_size_and_align(id, AllocCheck::MaybeDead)?;
+
+ let base_addr = match global_state.base_addr.entry(id) {
+ Entry::Occupied(entry) => *entry.get(),
+ Entry::Vacant(entry) => {
+ // 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.
+ let slack = {
+ let mut rng = memory.extra.rng.borrow_mut();
+ // This means that `(global_state.next_base_addr + slack) % 16` is uniformly distributed.
+ rng.gen_range(0, 16)
+ };
+ // From next_base_addr + slack, round up to adjust for alignment.
+ let base_addr = global_state.next_base_addr.checked_add(slack).unwrap();
+ let base_addr = Self::align_addr(base_addr, align.bytes());
+ entry.insert(base_addr);
+ trace!(
+ "Assigning base address {:#x} to allocation {:?} (slack: {}, align: {})",
+ base_addr,
+ id,
+ slack,
+ align.bytes(),
+ );
+
+ // 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.
+ 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, id));
+
+ base_addr
+ }
+ };
+
+ // Sanity check that the base address is aligned.
+ debug_assert_eq!(base_addr % align.bytes(), 0);
+ // Add offset with the right kind of pointer-overflowing arithmetic.
+ let dl = memory.data_layout();
+ Ok(dl.overflowing_offset(base_addr, ptr.offset.bytes()).0)
+ }
+
+ /// Shifts `addr` to make it aligned with `align` by rounding `addr` to the smallest multiple
+ /// of `align` that is larger or equal to `addr`
+ fn align_addr(addr: u64, align: u64) -> u64 {
+ match addr % align {
+ 0 => addr,
+ rem => addr.checked_add(align).unwrap() - rem,
}
}
}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+
+ #[test]
+ fn test_align_addr() {
+ assert_eq!(GlobalState::align_addr(37, 4), 40);
+ assert_eq!(GlobalState::align_addr(44, 4), 44);
+ }
+}
projects / rust.git / blobdiff