750 lines
30 KiB
Rust
750 lines
30 KiB
Rust
use std::cell::RefCell;
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use std::collections::HashSet;
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use std::rc::Rc;
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use std::fmt;
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use std::num::NonZeroU64;
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use rustc::ty::{self, layout::Size};
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use rustc::hir::{MutMutable, MutImmutable};
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use rustc::mir::RetagKind;
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use crate::{
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EvalResult, InterpError, MiriEvalContext, HelpersEvalContextExt, Evaluator, MutValueVisitor,
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MemoryKind, MiriMemoryKind, RangeMap, Allocation, AllocationExtra,
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Pointer, Immediate, ImmTy, PlaceTy, MPlaceTy,
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};
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pub type PtrId = NonZeroU64;
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pub type CallId = NonZeroU64;
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/// Tracking pointer provenance
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#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
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pub enum Tag {
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Tagged(PtrId),
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Untagged,
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}
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impl fmt::Display for Tag {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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match self {
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Tag::Tagged(id) => write!(f, "{}", id),
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Tag::Untagged => write!(f, "<untagged>"),
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}
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}
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}
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/// Indicates which permission is granted (by this item to some pointers)
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#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
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pub enum Permission {
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/// Grants unique mutable access.
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Unique,
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/// Grants shared mutable access.
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SharedReadWrite,
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/// Greants shared read-only access.
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SharedReadOnly,
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}
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/// An item in the per-location borrow stack.
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#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
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pub struct Item {
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/// The permission this item grants.
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perm: Permission,
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/// The pointers the permission is granted to.
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tag: Tag,
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/// An optional protector, ensuring the item cannot get popped until `CallId` is over.
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protector: Option<CallId>,
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}
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impl fmt::Display for Item {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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write!(f, "[{:?} for {}", self.perm, self.tag)?;
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if let Some(call) = self.protector {
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write!(f, " (call {})", call)?;
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}
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write!(f, "]")?;
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Ok(())
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}
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}
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/// Extra per-location state.
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#[derive(Clone, Debug, PartialEq, Eq)]
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pub struct Stack {
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/// Used *mostly* as a stack; never empty.
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/// We sometimes push into the middle but never remove from the middle.
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/// The same tag may occur multiple times, e.g. from a two-phase borrow.
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/// Invariants:
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/// * Above a `SharedReadOnly` there can only be more `SharedReadOnly`.
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borrows: Vec<Item>,
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}
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/// Extra per-allocation state.
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#[derive(Clone, Debug)]
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pub struct Stacks {
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// Even reading memory can have effects on the stack, so we need a `RefCell` here.
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stacks: RefCell<RangeMap<Stack>>,
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// Pointer to global state
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global: MemoryState,
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}
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/// Extra global state, available to the memory access hooks.
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#[derive(Debug)]
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pub struct GlobalState {
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next_ptr_id: PtrId,
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next_call_id: CallId,
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active_calls: HashSet<CallId>,
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}
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pub type MemoryState = Rc<RefCell<GlobalState>>;
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/// Indicates which kind of access is being performed.
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#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
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pub enum AccessKind {
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Read,
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Write,
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}
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impl fmt::Display for AccessKind {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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match self {
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AccessKind::Read => write!(f, "read"),
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AccessKind::Write => write!(f, "write"),
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}
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}
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}
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/// Indicates which kind of reference is being created.
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/// Used by high-level `reborrow` to compute which permissions to grant to the
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/// new pointer.
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#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
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pub enum RefKind {
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/// `&mut` and `Box`.
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Unique,
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/// `&` with or without interior mutability.
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Shared,
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/// `*mut`/`*const` (raw pointers).
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Raw { mutable: bool },
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}
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impl fmt::Display for RefKind {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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match self {
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RefKind::Unique => write!(f, "unique"),
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RefKind::Shared => write!(f, "shared"),
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RefKind::Raw { mutable: true } => write!(f, "raw (mutable)"),
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RefKind::Raw { mutable: false } => write!(f, "raw (constant)"),
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}
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}
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}
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/// Utilities for initialization and ID generation
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impl Default for GlobalState {
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fn default() -> Self {
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GlobalState {
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next_ptr_id: NonZeroU64::new(1).unwrap(),
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next_call_id: NonZeroU64::new(1).unwrap(),
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active_calls: HashSet::default(),
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}
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}
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}
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impl GlobalState {
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pub fn new_ptr(&mut self) -> PtrId {
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let id = self.next_ptr_id;
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self.next_ptr_id = NonZeroU64::new(id.get() + 1).unwrap();
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id
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}
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pub fn new_call(&mut self) -> CallId {
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let id = self.next_call_id;
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trace!("new_call: Assigning ID {}", id);
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self.active_calls.insert(id);
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self.next_call_id = NonZeroU64::new(id.get() + 1).unwrap();
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id
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}
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pub fn end_call(&mut self, id: CallId) {
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assert!(self.active_calls.remove(&id));
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}
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fn is_active(&self, id: CallId) -> bool {
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self.active_calls.contains(&id)
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}
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}
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// # Stacked Borrows Core Begin
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/// We need to make at least the following things true:
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///
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/// U1: After creating a `Uniq`, it is at the top.
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/// U2: If the top is `Uniq`, accesses must be through that `Uniq` or remove it it.
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/// U3: If an access happens with a `Uniq`, it requires the `Uniq` to be in the stack.
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///
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/// F1: After creating a `&`, the parts outside `UnsafeCell` have our `SharedReadOnly` on top.
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/// F2: If a write access happens, it pops the `SharedReadOnly`. This has three pieces:
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/// F2a: If a write happens granted by an item below our `SharedReadOnly`, the `SharedReadOnly`
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/// gets popped.
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/// F2b: No `SharedReadWrite` or `Unique` will ever be added on top of our `SharedReadOnly`.
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/// F3: If an access happens with an `&` outside `UnsafeCell`,
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/// it requires the `SharedReadOnly` to still be in the stack.
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impl Default for Tag {
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#[inline(always)]
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fn default() -> Tag {
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Tag::Untagged
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}
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}
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/// Core relations on `Permission` define which accesses are allowed:
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/// On every access, we try to find a *granting* item, and then we remove all
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/// *incompatible* items above it.
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impl Permission {
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/// This defines for a given permission, whether it permits the given kind of access.
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fn grants(self, access: AccessKind) -> bool {
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match (self, access) {
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// Unique and SharedReadWrite allow any kind of access.
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(Permission::Unique, _) |
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(Permission::SharedReadWrite, _) =>
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true,
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// SharedReadOnly only permits read access.
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(Permission::SharedReadOnly, AccessKind::Read) =>
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true,
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(Permission::SharedReadOnly, AccessKind::Write) =>
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false,
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}
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}
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/// This defines for a given permission, which other permissions it can tolerate "above" itself
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/// for which kinds of accesses.
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/// If true, then `other` is allowed to remain on top of `self` when `access` happens.
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fn compatible_with(self, access: AccessKind, other: Permission) -> bool {
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use self::Permission::*;
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match (self, access, other) {
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// Some cases are impossible.
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(SharedReadOnly, _, SharedReadWrite) |
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(SharedReadOnly, _, Unique) =>
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bug!("There can never be a SharedReadWrite or a Unique on top of a SharedReadOnly"),
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// When `other` is `SharedReadOnly`, that is NEVER compatible with
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// write accesses.
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// This makes sure read-only pointers become invalid on write accesses (ensures F2a).
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(_, AccessKind::Write, SharedReadOnly) =>
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false,
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// When `other` is `Unique`, that is compatible with nothing.
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// This makes sure unique pointers become invalid on incompatible accesses (ensures U2).
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(_, _, Unique) =>
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false,
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// When we are unique and this is a write/dealloc, we tolerate nothing.
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// This makes sure we re-assert uniqueness ("being on top") on write accesses.
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// (This is particularily important such that when a new mutable ref gets created, it gets
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// pushed onto the right item -- this behaves like a write and we assert uniqueness of the
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// pointer from which this comes, *if* it was a unique pointer.)
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(Unique, AccessKind::Write, _) =>
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false,
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// `SharedReadWrite` items can tolerate any other akin items for any kind of access.
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(SharedReadWrite, _, SharedReadWrite) =>
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true,
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// Any item can tolerate read accesses for shared items.
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// This includes unique items! Reads from unique pointers do not invalidate
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// other pointers.
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(_, AccessKind::Read, SharedReadWrite) |
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(_, AccessKind::Read, SharedReadOnly) =>
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true,
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// That's it.
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}
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}
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}
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/// Core per-location operations: access, dealloc, reborrow.
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impl<'tcx> Stack {
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/// Find the item granting the given kind of access to the given tag, and where
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/// *the first incompatible item above it* is on the stack.
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fn find_granting(&self, access: AccessKind, tag: Tag) -> Option<(Permission, usize)> {
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let (perm, idx) = self.borrows.iter()
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.enumerate() // we also need to know *where* in the stack
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.rev() // search top-to-bottom
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// Return permission of first item that grants access.
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// We require a permission with the right tag, ensuring U3 and F3.
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.find_map(|(idx, item)|
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if item.perm.grants(access) && tag == item.tag {
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Some((item.perm, idx))
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} else {
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None
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}
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)?;
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let mut first_incompatible_idx = idx+1;
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while let Some(item) = self.borrows.get(first_incompatible_idx) {
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if perm.compatible_with(access, item.perm) {
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// Keep this, check next.
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first_incompatible_idx += 1;
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} else {
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// Found it!
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break;
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}
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}
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return Some((perm, first_incompatible_idx));
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}
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/// Test if a memory `access` using pointer tagged `tag` is granted.
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/// If yes, return the index of the item that granted it.
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fn access(
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&mut self,
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access: AccessKind,
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tag: Tag,
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global: &GlobalState,
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) -> EvalResult<'tcx> {
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// Two main steps: Find granting item, remove all incompatible items above.
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// Step 1: Find granting item.
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let (granting_perm, first_incompatible_idx) = self.find_granting(access, tag)
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.ok_or_else(|| InterpError::MachineError(format!(
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"no item granting {} access to tag {} found in borrow stack",
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access, tag,
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)))?;
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// Step 2: Remove everything incompatible above them. Make sure we do not remove protected
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// items.
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// For writes, this is a simple stack. For reads, however, it is not:
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// in `let raw = &mut *x as *mut _; let _val = *x;`, the second statement would pop the `Unique`
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// from the reborrow of the first statement, and subsequently also pop the `SharedReadWrite` for `raw`.
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// This pattern occurs a lot in the standard library: create a raw pointer, then also create a shared
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// reference and use that.
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{
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// Implemented with indices because there does not seem to be a nice iterator and range-based
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// API for this.
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let mut cur = first_incompatible_idx;
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while let Some(item) = self.borrows.get(cur) {
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// If this is a read, we double-check if we really want to kill this.
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if access == AccessKind::Read && granting_perm.compatible_with(access, item.perm) {
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// Keep this, check next.
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cur += 1;
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} else {
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// Aha! This is a bad one, remove it, and make sure it is not protected.
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let item = self.borrows.remove(cur);
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if let Some(call) = item.protector {
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if global.is_active(call) {
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return err!(MachineError(format!(
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"not granting {} access to tag {} because incompatible item {} is protected",
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access, tag, item
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)));
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}
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}
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trace!("access: removing item {}", item);
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}
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}
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}
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// Done.
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Ok(())
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}
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/// Deallocate a location: Like a write access, but also there must be no
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/// active protectors at all.
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fn dealloc(
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&mut self,
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tag: Tag,
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global: &GlobalState,
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) -> EvalResult<'tcx> {
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// Step 1: Find granting item.
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self.find_granting(AccessKind::Write, tag)
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.ok_or_else(|| InterpError::MachineError(format!(
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"no item granting write access for deallocation to tag {} found in borrow stack",
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tag,
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)))?;
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// We must make sure there are no protected items remaining on the stack.
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// Also clear the stack, no more accesses are possible.
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for item in self.borrows.drain(..) {
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if let Some(call) = item.protector {
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if global.is_active(call) {
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return err!(MachineError(format!(
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"deallocating with active protector ({})", call
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)))
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}
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}
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}
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Ok(())
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}
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/// `reborrow` helper function: test that the stack invariants are still maintained.
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fn test_invariants(&self) {
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let mut saw_shared_read_only = false;
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for item in self.borrows.iter() {
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match item.perm {
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Permission::SharedReadOnly => {
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saw_shared_read_only = true;
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}
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// Otherwise, if we saw one before, that's a bug.
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perm if saw_shared_read_only => {
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bug!("Found {:?} on top of a SharedReadOnly!", perm);
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}
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_ => {}
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}
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}
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}
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/// Derived a new pointer from one with the given tag.
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/// `weak` controls whether this operation is weak or strong: weak granting does not act as
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/// an access, and they add the new item directly on top of the one it is derived
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/// from instead of all the way at the top of the stack.
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fn grant(
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&mut self,
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derived_from: Tag,
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weak: bool,
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new: Item,
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global: &GlobalState,
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) -> EvalResult<'tcx> {
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// Figure out which access `perm` corresponds to.
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let access = if new.perm.grants(AccessKind::Write) {
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AccessKind::Write
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} else {
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AccessKind::Read
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};
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// Now we figure out which item grants our parent (`derived_from`) this kind of access.
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// We use that to determine where to put the new item.
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let (_, first_incompatible_idx) = self.find_granting(access, derived_from)
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.ok_or_else(|| InterpError::MachineError(format!(
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"no item to reborrow for {:?} from tag {} found in borrow stack", new.perm, derived_from,
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)))?;
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// Compute where to put the new item.
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// Either way, we ensure that we insert the new item in a way that between
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// `derived_from` and the new one, there are only items *compatible with* `derived_from`.
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let new_idx = if weak {
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// A weak SharedReadOnly reborrow might be added below other items, violating the
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// invariant that only SharedReadOnly can sit on top of SharedReadOnly.
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assert!(new.perm != Permission::SharedReadOnly, "Weak SharedReadOnly reborrows don't work");
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// A very liberal reborrow because the new pointer does not expect any kind of aliasing guarantee.
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// Just insert new permission as child of old permission, and maintain everything else.
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// This inserts "as far down as possible", which is good because it makes this pointer as
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// long-lived as possible *and* we want all the items that are incompatible with this
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// to actually get removed from the stack. If we pushed a `SharedReadWrite` on top of
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// a `SharedReadOnly`, we'd violate the invariant that `SaredReadOnly` are at the top
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// and we'd allow write access without invalidating frozen shared references!
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// This ensures F2b for `SharedReadWrite` by adding the new item below any
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// potentially existing `SharedReadOnly`.
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first_incompatible_idx
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} else {
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// A "safe" reborrow for a pointer that actually expects some aliasing guarantees.
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// Here, creating a reference actually counts as an access, and pops incompatible
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// stuff off the stack.
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// This ensures F2b for `Unique`, by removing offending `SharedReadOnly`.
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self.access(access, derived_from, global)?;
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if access == AccessKind::Write {
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// For write accesses, the position is the same as what it would have been weakly!
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assert_eq!(first_incompatible_idx, self.borrows.len());
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}
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// We insert "as far up as possible": We know only compatible items are remaining
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// on top of `derived_from`, and we want the new item at the top so that we
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// get the strongest possible guarantees.
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// This ensures U1 and F1.
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self.borrows.len()
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};
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// Put the new item there. As an optimization, deduplicate if it is equal to one of its new neighbors.
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if self.borrows[new_idx-1] == new || self.borrows.get(new_idx) == Some(&new) {
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// Optimization applies, done.
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trace!("reborrow: avoiding adding redundant item {}", new);
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} else {
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trace!("reborrow: adding item {}", new);
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self.borrows.insert(new_idx, new);
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}
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// Make sure that after all this, the stack's invariant is still maintained.
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if cfg!(debug_assertions) {
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self.test_invariants();
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}
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Ok(())
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}
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}
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// # Stacked Borrows Core End
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/// Map per-stack operations to higher-level per-location-range operations.
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impl<'tcx> Stacks {
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/// Creates new stack with initial tag.
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pub(crate) fn new(
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size: Size,
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tag: Tag,
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extra: MemoryState,
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) -> Self {
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let item = Item { perm: Permission::Unique, tag, protector: None };
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let stack = Stack {
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borrows: vec![item],
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};
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Stacks {
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stacks: RefCell::new(RangeMap::new(size, stack)),
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global: extra,
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}
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}
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/// Call `f` on every stack in the range.
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fn for_each(
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&self,
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ptr: Pointer<Tag>,
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size: Size,
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f: impl Fn(&mut Stack, &GlobalState) -> EvalResult<'tcx>,
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) -> EvalResult<'tcx> {
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let global = self.global.borrow();
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let mut stacks = self.stacks.borrow_mut();
|
|
for stack in stacks.iter_mut(ptr.offset, size) {
|
|
f(stack, &*global)?;
|
|
}
|
|
Ok(())
|
|
}
|
|
}
|
|
|
|
/// Glue code to connect with Miri Machine Hooks
|
|
impl Stacks {
|
|
pub fn new_allocation(
|
|
size: Size,
|
|
extra: &MemoryState,
|
|
kind: MemoryKind<MiriMemoryKind>,
|
|
) -> (Self, Tag) {
|
|
let tag = match kind {
|
|
MemoryKind::Stack => {
|
|
// New unique borrow. This `Uniq` is not accessible by the program,
|
|
// so it will only ever be used when using the local directly (i.e.,
|
|
// not through a pointer). That is, whenever we directly use a local, this will pop
|
|
// everything else off the stack, invalidating all previous pointers,
|
|
// and in particular, *all* raw pointers. This subsumes the explicit
|
|
// `reset` which the blog post [1] says to perform when accessing a local.
|
|
//
|
|
// [1]: <https://www.ralfj.de/blog/2018/08/07/stacked-borrows.html>
|
|
Tag::Tagged(extra.borrow_mut().new_ptr())
|
|
}
|
|
_ => {
|
|
Tag::Untagged
|
|
}
|
|
};
|
|
let stack = Stacks::new(size, tag, Rc::clone(extra));
|
|
(stack, tag)
|
|
}
|
|
}
|
|
|
|
impl AllocationExtra<Tag> for Stacks {
|
|
#[inline(always)]
|
|
fn memory_read<'tcx>(
|
|
alloc: &Allocation<Tag, Stacks>,
|
|
ptr: Pointer<Tag>,
|
|
size: Size,
|
|
) -> EvalResult<'tcx> {
|
|
trace!("read access with tag {}: {:?}, size {}", ptr.tag, ptr, size.bytes());
|
|
alloc.extra.for_each(ptr, size, |stack, global| {
|
|
stack.access(AccessKind::Read, ptr.tag, global)?;
|
|
Ok(())
|
|
})
|
|
}
|
|
|
|
#[inline(always)]
|
|
fn memory_written<'tcx>(
|
|
alloc: &mut Allocation<Tag, Stacks>,
|
|
ptr: Pointer<Tag>,
|
|
size: Size,
|
|
) -> EvalResult<'tcx> {
|
|
trace!("write access with tag {}: {:?}, size {}", ptr.tag, ptr, size.bytes());
|
|
alloc.extra.for_each(ptr, size, |stack, global| {
|
|
stack.access(AccessKind::Write, ptr.tag, global)?;
|
|
Ok(())
|
|
})
|
|
}
|
|
|
|
#[inline(always)]
|
|
fn memory_deallocated<'tcx>(
|
|
alloc: &mut Allocation<Tag, Stacks>,
|
|
ptr: Pointer<Tag>,
|
|
size: Size,
|
|
) -> EvalResult<'tcx> {
|
|
trace!("deallocation with tag {}: {:?}, size {}", ptr.tag, ptr, size.bytes());
|
|
alloc.extra.for_each(ptr, size, |stack, global| {
|
|
stack.dealloc(ptr.tag, global)
|
|
})
|
|
}
|
|
}
|
|
|
|
/// Retagging/reborrowing. There is some policy in here, such as which permissions
|
|
/// to grant for which references, when to add protectors, and how to realize two-phase
|
|
/// borrows in terms of the primitives above.
|
|
impl<'a, 'mir, 'tcx> EvalContextPrivExt<'a, 'mir, 'tcx> for crate::MiriEvalContext<'a, 'mir, 'tcx> {}
|
|
trait EvalContextPrivExt<'a, 'mir, 'tcx: 'a+'mir>: crate::MiriEvalContextExt<'a, 'mir, 'tcx> {
|
|
fn reborrow(
|
|
&mut self,
|
|
place: MPlaceTy<'tcx, Tag>,
|
|
size: Size,
|
|
kind: RefKind,
|
|
new_tag: Tag,
|
|
force_weak: bool,
|
|
protect: bool,
|
|
) -> EvalResult<'tcx> {
|
|
let this = self.eval_context_mut();
|
|
let protector = if protect { Some(this.frame().extra) } else { None };
|
|
let ptr = place.ptr.to_ptr()?;
|
|
trace!("reborrow: {:?} reference {} derived from {} (pointee {}): {:?}, size {}",
|
|
kind, new_tag, ptr.tag, place.layout.ty, ptr, size.bytes());
|
|
|
|
// Get the allocation. It might not be mutable, so we cannot use `get_mut`.
|
|
let alloc = this.memory().get(ptr.alloc_id)?;
|
|
alloc.check_bounds(this, ptr, size)?;
|
|
// Update the stacks.
|
|
// Make sure that raw pointers and mutable shared references are reborrowed "weak":
|
|
// There could be existing unique pointers reborrowed from them that should remain valid!
|
|
let perm = match kind {
|
|
RefKind::Unique => Permission::Unique,
|
|
RefKind::Raw { mutable: true } => Permission::SharedReadWrite,
|
|
RefKind::Shared | RefKind::Raw { mutable: false } => {
|
|
// Shared references and *const are a whole different kind of game, the
|
|
// permission is not uniform across the entire range!
|
|
// We need a frozen-sensitive reborrow.
|
|
return this.visit_freeze_sensitive(place, size, |cur_ptr, size, frozen| {
|
|
// We are only ever `SharedReadOnly` inside the frozen bits.
|
|
let perm = if frozen { Permission::SharedReadOnly } else { Permission::SharedReadWrite };
|
|
let weak = perm == Permission::SharedReadWrite;
|
|
let item = Item { perm, tag: new_tag, protector };
|
|
alloc.extra.for_each(cur_ptr, size, |stack, global| {
|
|
stack.grant(cur_ptr.tag, force_weak || weak, item, global)
|
|
})
|
|
});
|
|
}
|
|
};
|
|
debug_assert_ne!(perm, Permission::SharedReadOnly, "SharedReadOnly must be used frozen-sensitive");
|
|
let weak = perm == Permission::SharedReadWrite;
|
|
let item = Item { perm, tag: new_tag, protector };
|
|
alloc.extra.for_each(ptr, size, |stack, global| {
|
|
stack.grant(ptr.tag, force_weak || weak, item, global)
|
|
})
|
|
}
|
|
|
|
/// Retags an indidual pointer, returning the retagged version.
|
|
/// `mutbl` can be `None` to make this a raw pointer.
|
|
fn retag_reference(
|
|
&mut self,
|
|
val: ImmTy<'tcx, Tag>,
|
|
kind: RefKind,
|
|
protect: bool,
|
|
two_phase: bool,
|
|
) -> EvalResult<'tcx, Immediate<Tag>> {
|
|
let this = self.eval_context_mut();
|
|
// We want a place for where the ptr *points to*, so we get one.
|
|
let place = this.ref_to_mplace(val)?;
|
|
let size = this.size_and_align_of_mplace(place)?
|
|
.map(|(size, _)| size)
|
|
.unwrap_or_else(|| place.layout.size);
|
|
if size == Size::ZERO {
|
|
// Nothing to do for ZSTs.
|
|
return Ok(*val);
|
|
}
|
|
|
|
// Compute new borrow.
|
|
let new_tag = match kind {
|
|
RefKind::Raw { .. } => Tag::Untagged,
|
|
_ => Tag::Tagged(this.memory().extra.borrow_mut().new_ptr()),
|
|
};
|
|
|
|
// Reborrow.
|
|
// TODO: With `two_phase == true`, this performs a weak reborrow for a `Unique`. That
|
|
// can lead to some possibly surprising effects, if the parent permission is
|
|
// `SharedReadWrite` then we now have a `Unique` in the middle of them, which "splits"
|
|
// them in terms of what remains valid when the `Unique` gets used. Is that really
|
|
// what we want?
|
|
this.reborrow(place, size, kind, new_tag, /*force_weak:*/ two_phase, protect)?;
|
|
let new_place = place.replace_tag(new_tag);
|
|
// Handle two-phase borrows.
|
|
if two_phase {
|
|
assert!(kind == RefKind::Unique, "two-phase shared borrows make no sense");
|
|
// Grant read access *to the parent pointer* with the old tag *derived from the new tag* (`new_place`).
|
|
// This means the old pointer has multiple items in the stack now, which otherwise cannot happen
|
|
// for unique references -- but in this case it precisely expresses the semantics we want.
|
|
let old_tag = place.ptr.to_ptr().unwrap().tag;
|
|
this.reborrow(new_place, size, RefKind::Shared, old_tag, /*force_weak:*/ false, /*protect:*/ false)?;
|
|
}
|
|
|
|
// Return new pointer.
|
|
Ok(new_place.to_ref())
|
|
}
|
|
}
|
|
|
|
impl<'a, 'mir, 'tcx> EvalContextExt<'a, 'mir, 'tcx> for crate::MiriEvalContext<'a, 'mir, 'tcx> {}
|
|
pub trait EvalContextExt<'a, 'mir, 'tcx: 'a+'mir>: crate::MiriEvalContextExt<'a, 'mir, 'tcx> {
|
|
fn retag(
|
|
&mut self,
|
|
kind: RetagKind,
|
|
place: PlaceTy<'tcx, Tag>
|
|
) -> EvalResult<'tcx> {
|
|
let this = self.eval_context_mut();
|
|
// Determine mutability and whether to add a protector.
|
|
// Cannot use `builtin_deref` because that reports *immutable* for `Box`,
|
|
// making it useless.
|
|
fn qualify(ty: ty::Ty<'_>, kind: RetagKind) -> Option<(RefKind, bool)> {
|
|
match ty.sty {
|
|
// References are simple.
|
|
ty::Ref(_, _, MutMutable) =>
|
|
Some((RefKind::Unique, kind == RetagKind::FnEntry)),
|
|
ty::Ref(_, _, MutImmutable) =>
|
|
Some((RefKind::Shared, kind == RetagKind::FnEntry)),
|
|
// Raw pointers need to be enabled.
|
|
ty::RawPtr(tym) if kind == RetagKind::Raw =>
|
|
Some((RefKind::Raw { mutable: tym.mutbl == MutMutable }, false)),
|
|
// Boxes do not get a protector: protectors reflect that references outlive the call
|
|
// they were passed in to; that's just not the case for boxes.
|
|
ty::Adt(..) if ty.is_box() => Some((RefKind::Unique, false)),
|
|
_ => None,
|
|
}
|
|
}
|
|
|
|
// We need a visitor to visit all references. However, that requires
|
|
// a `MemPlace`, so we have a fast path for reference types that
|
|
// avoids allocating.
|
|
if let Some((mutbl, protector)) = qualify(place.layout.ty, kind) {
|
|
// Fast path.
|
|
let val = this.read_immediate(this.place_to_op(place)?)?;
|
|
let val = this.retag_reference(val, mutbl, protector, kind == RetagKind::TwoPhase)?;
|
|
this.write_immediate(val, place)?;
|
|
return Ok(());
|
|
}
|
|
let place = this.force_allocation(place)?;
|
|
|
|
let mut visitor = RetagVisitor { ecx: this, kind };
|
|
visitor.visit_value(place)?;
|
|
|
|
// The actual visitor.
|
|
struct RetagVisitor<'ecx, 'a, 'mir, 'tcx> {
|
|
ecx: &'ecx mut MiriEvalContext<'a, 'mir, 'tcx>,
|
|
kind: RetagKind,
|
|
}
|
|
impl<'ecx, 'a, 'mir, 'tcx>
|
|
MutValueVisitor<'a, 'mir, 'tcx, Evaluator<'tcx>>
|
|
for
|
|
RetagVisitor<'ecx, 'a, 'mir, 'tcx>
|
|
{
|
|
type V = MPlaceTy<'tcx, Tag>;
|
|
|
|
#[inline(always)]
|
|
fn ecx(&mut self) -> &mut MiriEvalContext<'a, 'mir, 'tcx> {
|
|
&mut self.ecx
|
|
}
|
|
|
|
// Primitives of reference type, that is the one thing we are interested in.
|
|
fn visit_primitive(&mut self, place: MPlaceTy<'tcx, Tag>) -> EvalResult<'tcx>
|
|
{
|
|
// Cannot use `builtin_deref` because that reports *immutable* for `Box`,
|
|
// making it useless.
|
|
if let Some((mutbl, protector)) = qualify(place.layout.ty, self.kind) {
|
|
let val = self.ecx.read_immediate(place.into())?;
|
|
let val = self.ecx.retag_reference(
|
|
val,
|
|
mutbl,
|
|
protector,
|
|
self.kind == RetagKind::TwoPhase
|
|
)?;
|
|
self.ecx.write_immediate(val, place.into())?;
|
|
}
|
|
Ok(())
|
|
}
|
|
}
|
|
|
|
Ok(())
|
|
}
|
|
}
|