-use std::cell::{Cell, RefCell};
+use std::cell::RefCell;
+use std::collections::{HashMap, hash_map::Entry};
+use std::cmp::max;
-use rustc::mir::interpret::{AllocId, Pointer, InterpResult};
-use rustc_mir::interpret::Memory;
+use rand::Rng;
+
+use rustc::ty::layout::HasDataLayout;
+use rustc_mir::interpret::{AllocId, Pointer, InterpResult, Memory, AllocCheck, PointerArithmetic};
use rustc_target::abi::Size;
-use crate::stacked_borrows::Tag;
-use crate::Evaluator;
+use crate::{Evaluator, Tag, STACK_ADDR};
pub type MemoryExtra = RefCell<GlobalState>;
-#[derive(Clone, Debug, Default)]
-pub struct AllocExtra {
- base_addr: Cell<Option<u64>>
-}
-
#[derive(Clone, Debug)]
pub struct GlobalState {
/// 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: HashMap<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 {
- // FIXME: Query the page size in the future
fn default() -> Self {
GlobalState {
int_to_ptr_map: Vec::default(),
- next_base_addr: 2u64.pow(16)
+ base_addr: HashMap::default(),
+ next_base_addr: STACK_ADDR,
}
}
}
impl<'mir, 'tcx> GlobalState {
pub fn int_to_ptr(
- base_addr: u64,
+ int: u64,
memory: &Memory<'mir, 'tcx, Evaluator<'tcx>>,
) -> InterpResult<'tcx, Pointer<Tag>> {
let global_state = memory.extra.intptrcast.borrow();
- match global_state.int_to_ptr_map.binary_search_by_key(&base_addr, |(addr, _)| *addr) {
+ match global_state.int_to_ptr_map.binary_search_by_key(&int, |(addr, _)| *addr) {
Ok(pos) => {
let (_, alloc_id) = global_state.int_to_ptr_map[pos];
- // `base_addr` is the starting address for an allocation, the offset should be
+ // `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
Ok(Pointer::new_with_tag(alloc_id, Size::from_bytes(0), Tag::Untagged))
},
Err(0) => err!(DanglingPointerDeref),
Err(pos) => {
- // This is the gargest of the adresses smaller than `base_addr`,
+ // 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 `base_addr >= glb`
- let offset = base_addr - glb;
+ // 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(alloc_id)?.bytes.len() as u64 {
// This pointer is untagged because it was created from a cast
memory: &Memory<'mir, 'tcx, Evaluator<'tcx>>,
) -> InterpResult<'tcx, u64> {
let mut global_state = memory.extra.intptrcast.borrow_mut();
+ let global_state = &mut *global_state;
- let alloc = memory.get(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(ptr.alloc_id, AllocCheck::MaybeDead)?;
- let base_addr = match alloc.extra.intptrcast.base_addr.get() {
- Some(base_addr) => base_addr,
- None => {
- let base_addr = global_state.next_base_addr;
- global_state.next_base_addr += alloc.bytes.len() as u64;
-
- alloc.extra.intptrcast.base_addr.set(Some(base_addr));
-
- let elem = (base_addr, ptr.alloc_id);
+ let base_addr = match global_state.base_addr.entry(ptr.alloc_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.as_ref().unwrap().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 = Self::align_addr(global_state.next_base_addr + slack, align.bytes());
+ entry.insert(base_addr);
+ trace!(
+ "Assigning base address {:#x} to allocation {:?} (slack: {}, align: {})",
+ base_addr, ptr.alloc_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 + max(size.bytes(), 1);
// 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(elem);
+ global_state.int_to_ptr_map.push((base_addr, ptr.alloc_id));
base_addr
}
};
- Ok(base_addr + ptr.offset.bytes())
+ debug_assert_eq!(base_addr % align.bytes(), 0); // sanity check
+ // 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 + align - 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