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|
//! The memory subsystem.
//!
//! Generally, we use `Pointer` to denote memory addresses. However, some operations
//! have a "size"-like parameter, and they take `Scalar` for the address because
//! if the size is 0, then the pointer can also be a (properly aligned, non-null)
//! integer. It is crucial that these operations call `check_align` *before*
//! short-circuiting the empty case!
use std::assert_matches::assert_matches;
use std::borrow::Cow;
use std::collections::VecDeque;
use std::fmt;
use std::ptr;
use rustc_ast::Mutability;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_middle::mir::display_allocation;
use rustc_middle::ty::{self, Instance, ParamEnv, Ty, TyCtxt};
use rustc_target::abi::{Align, HasDataLayout, Size};
use crate::const_eval::CheckAlignment;
use super::{
alloc_range, AllocBytes, AllocId, AllocMap, AllocRange, Allocation, CheckInAllocMsg,
GlobalAlloc, InterpCx, InterpResult, Machine, MayLeak, Pointer, PointerArithmetic, Provenance,
Scalar,
};
#[derive(Debug, PartialEq, Copy, Clone)]
pub enum MemoryKind<T> {
/// Stack memory. Error if deallocated except during a stack pop.
Stack,
/// Memory allocated by `caller_location` intrinsic. Error if ever deallocated.
CallerLocation,
/// Additional memory kinds a machine wishes to distinguish from the builtin ones.
Machine(T),
}
impl<T: MayLeak> MayLeak for MemoryKind<T> {
#[inline]
fn may_leak(self) -> bool {
match self {
MemoryKind::Stack => false,
MemoryKind::CallerLocation => true,
MemoryKind::Machine(k) => k.may_leak(),
}
}
}
impl<T: fmt::Display> fmt::Display for MemoryKind<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
MemoryKind::Stack => write!(f, "stack variable"),
MemoryKind::CallerLocation => write!(f, "caller location"),
MemoryKind::Machine(m) => write!(f, "{}", m),
}
}
}
/// The return value of `get_alloc_info` indicates the "kind" of the allocation.
pub enum AllocKind {
/// A regular live data allocation.
LiveData,
/// A function allocation (that fn ptrs point to).
Function,
/// A (symbolic) vtable allocation.
VTable,
/// A dead allocation.
Dead,
}
/// The value of a function pointer.
#[derive(Debug, Copy, Clone)]
pub enum FnVal<'tcx, Other> {
Instance(Instance<'tcx>),
Other(Other),
}
impl<'tcx, Other> FnVal<'tcx, Other> {
pub fn as_instance(self) -> InterpResult<'tcx, Instance<'tcx>> {
match self {
FnVal::Instance(instance) => Ok(instance),
FnVal::Other(_) => {
throw_unsup_format!("'foreign' function pointers are not supported in this context")
}
}
}
}
// `Memory` has to depend on the `Machine` because some of its operations
// (e.g., `get`) call a `Machine` hook.
pub struct Memory<'mir, 'tcx, M: Machine<'mir, 'tcx>> {
/// Allocations local to this instance of the miri engine. The kind
/// helps ensure that the same mechanism is used for allocation and
/// deallocation. When an allocation is not found here, it is a
/// global and looked up in the `tcx` for read access. Some machines may
/// have to mutate this map even on a read-only access to a global (because
/// they do pointer provenance tracking and the allocations in `tcx` have
/// the wrong type), so we let the machine override this type.
/// Either way, if the machine allows writing to a global, doing so will
/// create a copy of the global allocation here.
// FIXME: this should not be public, but interning currently needs access to it
pub(super) alloc_map: M::MemoryMap,
/// Map for "extra" function pointers.
extra_fn_ptr_map: FxHashMap<AllocId, M::ExtraFnVal>,
/// To be able to compare pointers with null, and to check alignment for accesses
/// to ZSTs (where pointers may dangle), we keep track of the size even for allocations
/// that do not exist any more.
// FIXME: this should not be public, but interning currently needs access to it
pub(super) dead_alloc_map: FxHashMap<AllocId, (Size, Align)>,
}
/// 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: Provenance, Extra, Bytes: AllocBytes = Box<[u8]>> {
alloc: &'a Allocation<Prov, Extra, Bytes>,
range: AllocRange,
tcx: TyCtxt<'tcx>,
alloc_id: AllocId,
}
/// 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: Provenance, Extra, Bytes: AllocBytes = Box<[u8]>> {
alloc: &'a mut Allocation<Prov, Extra, Bytes>,
range: AllocRange,
tcx: TyCtxt<'tcx>,
alloc_id: AllocId,
}
impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
pub fn new() -> Self {
Memory {
alloc_map: M::MemoryMap::default(),
extra_fn_ptr_map: FxHashMap::default(),
dead_alloc_map: FxHashMap::default(),
}
}
/// This is used by [priroda](https://github.com/oli-obk/priroda)
pub fn alloc_map(&self) -> &M::MemoryMap {
&self.alloc_map
}
}
impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
/// Call this to turn untagged "global" pointers (obtained via `tcx`) into
/// the machine pointer to the allocation. Must never be used
/// for any other pointers, nor for TLS statics.
///
/// Using the resulting pointer represents a *direct* access to that memory
/// (e.g. by directly using a `static`),
/// as opposed to access through a pointer that was created by the program.
///
/// This function can fail only if `ptr` points to an `extern static`.
#[inline]
pub fn global_base_pointer(
&self,
ptr: Pointer<AllocId>,
) -> InterpResult<'tcx, Pointer<M::Provenance>> {
let alloc_id = ptr.provenance;
// We need to handle `extern static`.
match self.tcx.try_get_global_alloc(alloc_id) {
Some(GlobalAlloc::Static(def_id)) if self.tcx.is_thread_local_static(def_id) => {
bug!("global memory cannot point to thread-local static")
}
Some(GlobalAlloc::Static(def_id)) if self.tcx.is_foreign_item(def_id) => {
return M::extern_static_base_pointer(self, def_id);
}
_ => {}
}
// And we need to get the provenance.
M::adjust_alloc_base_pointer(self, ptr)
}
pub fn create_fn_alloc_ptr(
&mut self,
fn_val: FnVal<'tcx, M::ExtraFnVal>,
) -> Pointer<M::Provenance> {
let id = match fn_val {
FnVal::Instance(instance) => self.tcx.create_fn_alloc(instance),
FnVal::Other(extra) => {
// FIXME(RalfJung): Should we have a cache here?
let id = self.tcx.reserve_alloc_id();
let old = self.memory.extra_fn_ptr_map.insert(id, extra);
assert!(old.is_none());
id
}
};
// Functions are global allocations, so make sure we get the right base pointer.
// We know this is not an `extern static` so this cannot fail.
self.global_base_pointer(Pointer::from(id)).unwrap()
}
pub fn allocate_ptr(
&mut self,
size: Size,
align: Align,
kind: MemoryKind<M::MemoryKind>,
) -> InterpResult<'tcx, Pointer<M::Provenance>> {
let alloc = Allocation::uninit(size, align, M::PANIC_ON_ALLOC_FAIL)?;
self.allocate_raw_ptr(alloc, kind)
}
pub fn allocate_bytes_ptr(
&mut self,
bytes: &[u8],
align: Align,
kind: MemoryKind<M::MemoryKind>,
mutability: Mutability,
) -> InterpResult<'tcx, Pointer<M::Provenance>> {
let alloc = Allocation::from_bytes(bytes, align, mutability);
self.allocate_raw_ptr(alloc, kind)
}
/// This can fail only if `alloc` contains provenance.
pub fn allocate_raw_ptr(
&mut self,
alloc: Allocation,
kind: MemoryKind<M::MemoryKind>,
) -> InterpResult<'tcx, Pointer<M::Provenance>> {
let id = self.tcx.reserve_alloc_id();
debug_assert_ne!(
Some(kind),
M::GLOBAL_KIND.map(MemoryKind::Machine),
"dynamically allocating global memory"
);
let alloc = M::adjust_allocation(self, id, Cow::Owned(alloc), Some(kind))?;
self.memory.alloc_map.insert(id, (kind, alloc.into_owned()));
M::adjust_alloc_base_pointer(self, Pointer::from(id))
}
pub fn reallocate_ptr(
&mut self,
ptr: Pointer<Option<M::Provenance>>,
old_size_and_align: Option<(Size, Align)>,
new_size: Size,
new_align: Align,
kind: MemoryKind<M::MemoryKind>,
) -> InterpResult<'tcx, Pointer<M::Provenance>> {
let (alloc_id, offset, _prov) = self.ptr_get_alloc_id(ptr)?;
if offset.bytes() != 0 {
throw_ub_format!(
"reallocating {:?} which does not point to the beginning of an object",
ptr
);
}
// For simplicities' sake, we implement reallocate as "alloc, copy, dealloc".
// This happens so rarely, the perf advantage is outweighed by the maintenance cost.
let new_ptr = self.allocate_ptr(new_size, new_align, kind)?;
let old_size = match old_size_and_align {
Some((size, _align)) => size,
None => self.get_alloc_raw(alloc_id)?.size(),
};
// This will also call the access hooks.
self.mem_copy(
ptr,
Align::ONE,
new_ptr.into(),
Align::ONE,
old_size.min(new_size),
/*nonoverlapping*/ true,
)?;
self.deallocate_ptr(ptr, old_size_and_align, kind)?;
Ok(new_ptr)
}
#[instrument(skip(self), level = "debug")]
pub fn deallocate_ptr(
&mut self,
ptr: Pointer<Option<M::Provenance>>,
old_size_and_align: Option<(Size, Align)>,
kind: MemoryKind<M::MemoryKind>,
) -> InterpResult<'tcx> {
let (alloc_id, offset, prov) = self.ptr_get_alloc_id(ptr)?;
trace!("deallocating: {alloc_id:?}");
if offset.bytes() != 0 {
throw_ub_format!(
"deallocating {:?} which does not point to the beginning of an object",
ptr
);
}
let Some((alloc_kind, mut alloc)) = self.memory.alloc_map.remove(&alloc_id) else {
// Deallocating global memory -- always an error
return Err(match self.tcx.try_get_global_alloc(alloc_id) {
Some(GlobalAlloc::Function(..)) => {
err_ub_format!("deallocating {alloc_id:?}, which is a function")
}
Some(GlobalAlloc::VTable(..)) => {
err_ub_format!("deallocating {alloc_id:?}, which is a vtable")
}
Some(GlobalAlloc::Static(..) | GlobalAlloc::Memory(..)) => {
err_ub_format!("deallocating {alloc_id:?}, which is static memory")
}
None => err_ub!(PointerUseAfterFree(alloc_id)),
}
.into());
};
if alloc.mutability.is_not() {
throw_ub_format!("deallocating immutable allocation {alloc_id:?}");
}
if alloc_kind != kind {
throw_ub_format!(
"deallocating {alloc_id:?}, which is {alloc_kind} memory, using {kind} deallocation operation"
);
}
if let Some((size, align)) = old_size_and_align {
if size != alloc.size() || align != alloc.align {
throw_ub_format!(
"incorrect layout on deallocation: {alloc_id:?} has size {} and alignment {}, but gave size {} and alignment {}",
alloc.size().bytes(),
alloc.align.bytes(),
size.bytes(),
align.bytes(),
)
}
}
// Let the machine take some extra action
let size = alloc.size();
M::before_memory_deallocation(
*self.tcx,
&mut self.machine,
&mut alloc.extra,
(alloc_id, prov),
alloc_range(Size::ZERO, size),
)?;
// Don't forget to remember size and align of this now-dead allocation
let old = self.memory.dead_alloc_map.insert(alloc_id, (size, alloc.align));
if old.is_some() {
bug!("Nothing can be deallocated twice");
}
Ok(())
}
/// Internal helper function to determine the allocation and offset of a pointer (if any).
#[inline(always)]
fn get_ptr_access(
&self,
ptr: Pointer<Option<M::Provenance>>,
size: Size,
align: Align,
) -> InterpResult<'tcx, Option<(AllocId, Size, M::ProvenanceExtra)>> {
self.check_and_deref_ptr(
ptr,
size,
align,
M::enforce_alignment(self),
CheckInAllocMsg::MemoryAccessTest,
|alloc_id, offset, prov| {
let (size, align) = self.get_live_alloc_size_and_align(alloc_id)?;
Ok((size, align, (alloc_id, offset, prov)))
},
)
}
/// Check if the given pointer points to live memory of given `size` and `align`
/// (ignoring `M::enforce_alignment`). The caller can control the error message for the
/// out-of-bounds case.
#[inline(always)]
pub fn check_ptr_access_align(
&self,
ptr: Pointer<Option<M::Provenance>>,
size: Size,
align: Align,
msg: CheckInAllocMsg,
) -> InterpResult<'tcx> {
self.check_and_deref_ptr(
ptr,
size,
align,
CheckAlignment::Error,
msg,
|alloc_id, _, _| {
let (size, align) = self.get_live_alloc_size_and_align(alloc_id)?;
Ok((size, align, ()))
},
)?;
Ok(())
}
/// Low-level helper function to check if a ptr is in-bounds and potentially return a reference
/// to the allocation it points to. Supports both shared and mutable references, as the actual
/// checking is offloaded to a helper closure. `align` defines whether and which alignment check
/// is done. Returns `None` for size 0, and otherwise `Some` of what `alloc_size` returned.
fn check_and_deref_ptr<T>(
&self,
ptr: Pointer<Option<M::Provenance>>,
size: Size,
align: Align,
check: CheckAlignment,
msg: CheckInAllocMsg,
alloc_size: impl FnOnce(
AllocId,
Size,
M::ProvenanceExtra,
) -> InterpResult<'tcx, (Size, Align, T)>,
) -> InterpResult<'tcx, Option<T>> {
Ok(match self.ptr_try_get_alloc_id(ptr) {
Err(addr) => {
// We couldn't get a proper allocation. This is only okay if the access size is 0,
// and the address is not null.
if size.bytes() > 0 || addr == 0 {
throw_ub!(DanglingIntPointer(addr, msg));
}
// Must be aligned.
if check.should_check() {
self.check_offset_align(addr, align, check)?;
}
None
}
Ok((alloc_id, offset, prov)) => {
let (alloc_size, alloc_align, ret_val) = alloc_size(alloc_id, offset, prov)?;
// Test bounds. This also ensures non-null.
// It is sufficient to check this for the end pointer. Also check for overflow!
if offset.checked_add(size, &self.tcx).map_or(true, |end| end > alloc_size) {
throw_ub!(PointerOutOfBounds {
alloc_id,
alloc_size,
ptr_offset: self.target_usize_to_isize(offset.bytes()),
ptr_size: size,
msg,
})
}
// Ensure we never consider the null pointer dereferenceable.
if M::Provenance::OFFSET_IS_ADDR {
assert_ne!(ptr.addr(), Size::ZERO);
}
// Test align. Check this last; if both bounds and alignment are violated
// we want the error to be about the bounds.
if check.should_check() {
if M::use_addr_for_alignment_check(self) {
// `use_addr_for_alignment_check` can only be true if `OFFSET_IS_ADDR` is true.
self.check_offset_align(ptr.addr().bytes(), align, check)?;
} else {
// Check allocation alignment and offset alignment.
if alloc_align.bytes() < align.bytes() {
M::alignment_check_failed(self, alloc_align, align, check)?;
}
self.check_offset_align(offset.bytes(), align, check)?;
}
}
// We can still be zero-sized in this branch, in which case we have to
// return `None`.
if size.bytes() == 0 { None } else { Some(ret_val) }
}
})
}
fn check_offset_align(
&self,
offset: u64,
align: Align,
check: CheckAlignment,
) -> InterpResult<'tcx> {
if offset % align.bytes() == 0 {
Ok(())
} else {
// The biggest power of two through which `offset` is divisible.
let offset_pow2 = 1 << offset.trailing_zeros();
M::alignment_check_failed(self, Align::from_bytes(offset_pow2).unwrap(), align, check)
}
}
}
/// Allocation accessors
impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
/// Helper function to obtain a global (tcx) allocation.
/// This attempts to return a reference to an existing allocation if
/// one can be found in `tcx`. That, however, is only possible if `tcx` and
/// this machine use the same pointer provenance, so it is indirected through
/// `M::adjust_allocation`.
fn get_global_alloc(
&self,
id: AllocId,
is_write: bool,
) -> InterpResult<'tcx, Cow<'tcx, Allocation<M::Provenance, M::AllocExtra, M::Bytes>>> {
let (alloc, def_id) = match self.tcx.try_get_global_alloc(id) {
Some(GlobalAlloc::Memory(mem)) => {
// Memory of a constant or promoted or anonymous memory referenced by a static.
(mem, None)
}
Some(GlobalAlloc::Function(..)) => throw_ub!(DerefFunctionPointer(id)),
Some(GlobalAlloc::VTable(..)) => throw_ub!(DerefVTablePointer(id)),
None => throw_ub!(PointerUseAfterFree(id)),
Some(GlobalAlloc::Static(def_id)) => {
assert!(self.tcx.is_static(def_id));
assert!(!self.tcx.is_thread_local_static(def_id));
// Notice that every static has two `AllocId` that will resolve to the same
// thing here: one maps to `GlobalAlloc::Static`, this is the "lazy" ID,
// and the other one is maps to `GlobalAlloc::Memory`, this is returned by
// `eval_static_initializer` and it is the "resolved" ID.
// The resolved ID is never used by the interpreted program, it is hidden.
// This is relied upon for soundness of const-patterns; a pointer to the resolved
// ID would "sidestep" the checks that make sure consts do not point to statics!
// The `GlobalAlloc::Memory` branch here is still reachable though; when a static
// contains a reference to memory that was created during its evaluation (i.e., not
// to another static), those inner references only exist in "resolved" form.
if self.tcx.is_foreign_item(def_id) {
// This is unreachable in Miri, but can happen in CTFE where we actually *do* support
// referencing arbitrary (declared) extern statics.
throw_unsup!(ReadExternStatic(def_id));
}
// We don't give a span -- statics don't need that, they cannot be generic or associated.
let val = self.ctfe_query(None, |tcx| tcx.eval_static_initializer(def_id))?;
(val, Some(def_id))
}
};
M::before_access_global(*self.tcx, &self.machine, id, alloc, def_id, is_write)?;
// We got tcx memory. Let the machine initialize its "extra" stuff.
M::adjust_allocation(
self,
id, // always use the ID we got as input, not the "hidden" one.
Cow::Borrowed(alloc.inner()),
M::GLOBAL_KIND.map(MemoryKind::Machine),
)
}
/// Get the base address for the bytes in an `Allocation` specified by the
/// `AllocID` passed in; error if no such allocation exists.
///
/// It is up to the caller to take sufficient care when using this address:
/// there could be provenance or uninit memory in there, and other memory
/// accesses could invalidate the exposed pointer.
pub fn alloc_base_addr(&self, id: AllocId) -> InterpResult<'tcx, *const u8> {
let alloc = self.get_alloc_raw(id)?;
Ok(alloc.base_addr())
}
/// Gives raw access to the `Allocation`, without bounds or alignment checks.
/// The caller is responsible for calling the access hooks!
///
/// You almost certainly want to use `get_ptr_alloc`/`get_ptr_alloc_mut` instead.
fn get_alloc_raw(
&self,
id: AllocId,
) -> InterpResult<'tcx, &Allocation<M::Provenance, M::AllocExtra, M::Bytes>> {
// The error type of the inner closure here is somewhat funny. We have two
// ways of "erroring": An actual error, or because we got a reference from
// `get_global_alloc` that we can actually use directly without inserting anything anywhere.
// So the error type is `InterpResult<'tcx, &Allocation<M::Provenance>>`.
let a = self.memory.alloc_map.get_or(id, || {
let alloc = self.get_global_alloc(id, /*is_write*/ false).map_err(Err)?;
match alloc {
Cow::Borrowed(alloc) => {
// We got a ref, cheaply return that as an "error" so that the
// map does not get mutated.
Err(Ok(alloc))
}
Cow::Owned(alloc) => {
// Need to put it into the map and return a ref to that
let kind = M::GLOBAL_KIND.expect(
"I got a global allocation that I have to copy but the machine does \
not expect that to happen",
);
Ok((MemoryKind::Machine(kind), alloc))
}
}
});
// Now unpack that funny error type
match a {
Ok(a) => Ok(&a.1),
Err(a) => a,
}
}
/// "Safe" (bounds and align-checked) allocation access.
pub fn get_ptr_alloc<'a>(
&'a self,
ptr: Pointer<Option<M::Provenance>>,
size: Size,
align: Align,
) -> InterpResult<'tcx, Option<AllocRef<'a, 'tcx, M::Provenance, M::AllocExtra, M::Bytes>>>
{
let ptr_and_alloc = self.check_and_deref_ptr(
ptr,
size,
align,
M::enforce_alignment(self),
CheckInAllocMsg::MemoryAccessTest,
|alloc_id, offset, prov| {
let alloc = self.get_alloc_raw(alloc_id)?;
Ok((alloc.size(), alloc.align, (alloc_id, offset, prov, alloc)))
},
)?;
if let Some((alloc_id, offset, prov, alloc)) = ptr_and_alloc {
let range = alloc_range(offset, size);
M::before_memory_read(*self.tcx, &self.machine, &alloc.extra, (alloc_id, prov), range)?;
Ok(Some(AllocRef { alloc, range, tcx: *self.tcx, alloc_id }))
} else {
// Even in this branch we have to be sure that we actually access the allocation, in
// order to ensure that `static FOO: Type = FOO;` causes a cycle error instead of
// magically pulling *any* ZST value from the ether. However, the `get_raw` above is
// always called when `ptr` has an `AllocId`.
Ok(None)
}
}
/// Return the `extra` field of the given allocation.
pub fn get_alloc_extra<'a>(&'a self, id: AllocId) -> InterpResult<'tcx, &'a M::AllocExtra> {
Ok(&self.get_alloc_raw(id)?.extra)
}
/// Return the `mutability` field of the given allocation.
pub fn get_alloc_mutability<'a>(&'a self, id: AllocId) -> InterpResult<'tcx, Mutability> {
Ok(self.get_alloc_raw(id)?.mutability)
}
/// Gives raw mutable access to the `Allocation`, without bounds or alignment checks.
/// The caller is responsible for calling the access hooks!
///
/// Also returns a ptr to `self.extra` so that the caller can use it in parallel with the
/// allocation.
fn get_alloc_raw_mut(
&mut self,
id: AllocId,
) -> InterpResult<'tcx, (&mut Allocation<M::Provenance, M::AllocExtra, M::Bytes>, &mut M)> {
// We have "NLL problem case #3" here, which cannot be worked around without loss of
// efficiency even for the common case where the key is in the map.
// <https://rust-lang.github.io/rfcs/2094-nll.html#problem-case-3-conditional-control-flow-across-functions>
// (Cannot use `get_mut_or` since `get_global_alloc` needs `&self`.)
if self.memory.alloc_map.get_mut(id).is_none() {
// Slow path.
// Allocation not found locally, go look global.
let alloc = self.get_global_alloc(id, /*is_write*/ true)?;
let kind = M::GLOBAL_KIND.expect(
"I got a global allocation that I have to copy but the machine does \
not expect that to happen",
);
self.memory.alloc_map.insert(id, (MemoryKind::Machine(kind), alloc.into_owned()));
}
let (_kind, alloc) = self.memory.alloc_map.get_mut(id).unwrap();
if alloc.mutability.is_not() {
throw_ub!(WriteToReadOnly(id))
}
Ok((alloc, &mut self.machine))
}
/// "Safe" (bounds and align-checked) allocation access.
pub fn get_ptr_alloc_mut<'a>(
&'a mut self,
ptr: Pointer<Option<M::Provenance>>,
size: Size,
align: Align,
) -> InterpResult<'tcx, Option<AllocRefMut<'a, 'tcx, M::Provenance, M::AllocExtra, M::Bytes>>>
{
let parts = self.get_ptr_access(ptr, size, align)?;
if let Some((alloc_id, offset, prov)) = parts {
let tcx = *self.tcx;
// FIXME: can we somehow avoid looking up the allocation twice here?
// We cannot call `get_raw_mut` inside `check_and_deref_ptr` as that would duplicate `&mut self`.
let (alloc, machine) = self.get_alloc_raw_mut(alloc_id)?;
let range = alloc_range(offset, size);
M::before_memory_write(tcx, machine, &mut alloc.extra, (alloc_id, prov), range)?;
Ok(Some(AllocRefMut { alloc, range, tcx, alloc_id }))
} else {
Ok(None)
}
}
/// Return the `extra` field of the given allocation.
pub fn get_alloc_extra_mut<'a>(
&'a mut self,
id: AllocId,
) -> InterpResult<'tcx, (&'a mut M::AllocExtra, &'a mut M)> {
let (alloc, machine) = self.get_alloc_raw_mut(id)?;
Ok((&mut alloc.extra, machine))
}
/// Obtain the size and alignment of an allocation, even if that allocation has
/// been deallocated.
pub fn get_alloc_info(&self, id: AllocId) -> (Size, Align, AllocKind) {
// # Regular allocations
// Don't use `self.get_raw` here as that will
// a) cause cycles in case `id` refers to a static
// b) duplicate a global's allocation in miri
if let Some((_, alloc)) = self.memory.alloc_map.get(id) {
return (alloc.size(), alloc.align, AllocKind::LiveData);
}
// # Function pointers
// (both global from `alloc_map` and local from `extra_fn_ptr_map`)
if self.get_fn_alloc(id).is_some() {
return (Size::ZERO, Align::ONE, AllocKind::Function);
}
// # Statics
// Can't do this in the match argument, we may get cycle errors since the lock would
// be held throughout the match.
match self.tcx.try_get_global_alloc(id) {
Some(GlobalAlloc::Static(def_id)) => {
assert!(self.tcx.is_static(def_id));
assert!(!self.tcx.is_thread_local_static(def_id));
// Use size and align of the type.
let ty = self
.tcx
.type_of(def_id)
.no_bound_vars()
.expect("statics should not have generic parameters");
let layout = self.tcx.layout_of(ParamEnv::empty().and(ty)).unwrap();
assert!(layout.is_sized());
(layout.size, layout.align.abi, AllocKind::LiveData)
}
Some(GlobalAlloc::Memory(alloc)) => {
// Need to duplicate the logic here, because the global allocations have
// different associated types than the interpreter-local ones.
let alloc = alloc.inner();
(alloc.size(), alloc.align, AllocKind::LiveData)
}
Some(GlobalAlloc::Function(_)) => bug!("We already checked function pointers above"),
Some(GlobalAlloc::VTable(..)) => {
// No data to be accessed here. But vtables are pointer-aligned.
return (Size::ZERO, self.tcx.data_layout.pointer_align.abi, AllocKind::VTable);
}
// The rest must be dead.
None => {
// Deallocated pointers are allowed, we should be able to find
// them in the map.
let (size, align) = *self
.memory
.dead_alloc_map
.get(&id)
.expect("deallocated pointers should all be recorded in `dead_alloc_map`");
(size, align, AllocKind::Dead)
}
}
}
/// Obtain the size and alignment of a live allocation.
pub fn get_live_alloc_size_and_align(&self, id: AllocId) -> InterpResult<'tcx, (Size, Align)> {
let (size, align, kind) = self.get_alloc_info(id);
if matches!(kind, AllocKind::Dead) {
throw_ub!(PointerUseAfterFree(id))
}
Ok((size, align))
}
fn get_fn_alloc(&self, id: AllocId) -> Option<FnVal<'tcx, M::ExtraFnVal>> {
if let Some(extra) = self.memory.extra_fn_ptr_map.get(&id) {
Some(FnVal::Other(*extra))
} else {
match self.tcx.try_get_global_alloc(id) {
Some(GlobalAlloc::Function(instance)) => Some(FnVal::Instance(instance)),
_ => None,
}
}
}
pub fn get_ptr_fn(
&self,
ptr: Pointer<Option<M::Provenance>>,
) -> InterpResult<'tcx, FnVal<'tcx, M::ExtraFnVal>> {
trace!("get_ptr_fn({:?})", ptr);
let (alloc_id, offset, _prov) = self.ptr_get_alloc_id(ptr)?;
if offset.bytes() != 0 {
throw_ub!(InvalidFunctionPointer(Pointer::new(alloc_id, offset)))
}
self.get_fn_alloc(alloc_id)
.ok_or_else(|| err_ub!(InvalidFunctionPointer(Pointer::new(alloc_id, offset))).into())
}
pub fn get_ptr_vtable(
&self,
ptr: Pointer<Option<M::Provenance>>,
) -> InterpResult<'tcx, (Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>)> {
trace!("get_ptr_vtable({:?})", ptr);
let (alloc_id, offset, _tag) = self.ptr_get_alloc_id(ptr)?;
if offset.bytes() != 0 {
throw_ub!(InvalidVTablePointer(Pointer::new(alloc_id, offset)))
}
match self.tcx.try_get_global_alloc(alloc_id) {
Some(GlobalAlloc::VTable(ty, trait_ref)) => Ok((ty, trait_ref)),
_ => throw_ub!(InvalidVTablePointer(Pointer::new(alloc_id, offset))),
}
}
pub fn alloc_mark_immutable(&mut self, id: AllocId) -> InterpResult<'tcx> {
self.get_alloc_raw_mut(id)?.0.mutability = Mutability::Not;
Ok(())
}
/// Create a lazy debug printer that prints the given allocation and all allocations it points
/// to, recursively.
#[must_use]
pub fn dump_alloc<'a>(&'a self, id: AllocId) -> DumpAllocs<'a, 'mir, 'tcx, M> {
self.dump_allocs(vec![id])
}
/// Create a lazy debug printer for a list of allocations and all allocations they point to,
/// recursively.
#[must_use]
pub fn dump_allocs<'a>(&'a self, mut allocs: Vec<AllocId>) -> DumpAllocs<'a, 'mir, 'tcx, M> {
allocs.sort();
allocs.dedup();
DumpAllocs { ecx: self, allocs }
}
/// Find leaked allocations. Allocations reachable from `static_roots` or a `Global` allocation
/// are not considered leaked, as well as leaks whose kind's `may_leak()` returns true.
pub fn find_leaked_allocations(
&self,
static_roots: &[AllocId],
) -> Vec<(AllocId, MemoryKind<M::MemoryKind>, Allocation<M::Provenance, M::AllocExtra, M::Bytes>)>
{
// Collect the set of allocations that are *reachable* from `Global` allocations.
let reachable = {
let mut reachable = FxHashSet::default();
let global_kind = M::GLOBAL_KIND.map(MemoryKind::Machine);
let mut todo: Vec<_> =
self.memory.alloc_map.filter_map_collect(move |&id, &(kind, _)| {
if Some(kind) == global_kind { Some(id) } else { None }
});
todo.extend(static_roots);
while let Some(id) = todo.pop() {
if reachable.insert(id) {
// 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().provenances().filter_map(|prov| prov.get_alloc_id()),
);
}
}
}
reachable
};
// All allocations that are *not* `reachable` and *not* `may_leak` are considered leaking.
self.memory.alloc_map.filter_map_collect(|id, (kind, alloc)| {
if kind.may_leak() || reachable.contains(id) {
None
} else {
Some((*id, *kind, alloc.clone()))
}
})
}
}
#[doc(hidden)]
/// There's no way to use this directly, it's just a helper struct for the `dump_alloc(s)` methods.
pub struct DumpAllocs<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> {
ecx: &'a InterpCx<'mir, 'tcx, M>,
allocs: Vec<AllocId>,
}
impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> std::fmt::Debug for DumpAllocs<'a, 'mir, 'tcx, M> {
fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
// Cannot be a closure because it is generic in `Prov`, `Extra`.
fn write_allocation_track_relocs<'tcx, Prov: Provenance, Extra, Bytes: AllocBytes>(
fmt: &mut std::fmt::Formatter<'_>,
tcx: TyCtxt<'tcx>,
allocs_to_print: &mut VecDeque<AllocId>,
alloc: &Allocation<Prov, Extra, Bytes>,
) -> std::fmt::Result {
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))
}
let mut allocs_to_print: VecDeque<_> = self.allocs.iter().copied().collect();
// `allocs_printed` contains all allocations that we have already printed.
let mut allocs_printed = FxHashSet::default();
while let Some(id) = allocs_to_print.pop_front() {
if !allocs_printed.insert(id) {
// Already printed, so skip this.
continue;
}
write!(fmt, "{id:?}")?;
match self.ecx.memory.alloc_map.get(id) {
Some((kind, alloc)) => {
// normal alloc
write!(fmt, " ({}, ", kind)?;
write_allocation_track_relocs(
&mut *fmt,
*self.ecx.tcx,
&mut allocs_to_print,
alloc,
)?;
}
None => {
// global alloc
match self.ecx.tcx.try_get_global_alloc(id) {
Some(GlobalAlloc::Memory(alloc)) => {
write!(fmt, " (unchanged global, ")?;
write_allocation_track_relocs(
&mut *fmt,
*self.ecx.tcx,
&mut allocs_to_print,
alloc.inner(),
)?;
}
Some(GlobalAlloc::Function(func)) => {
write!(fmt, " (fn: {func})")?;
}
Some(GlobalAlloc::VTable(ty, Some(trait_ref))) => {
write!(fmt, " (vtable: impl {trait_ref} for {ty})")?;
}
Some(GlobalAlloc::VTable(ty, None)) => {
write!(fmt, " (vtable: impl <auto trait> for {ty})")?;
}
Some(GlobalAlloc::Static(did)) => {
write!(fmt, " (static: {})", self.ecx.tcx.def_path_str(did))?;
}
None => {
write!(fmt, " (deallocated)")?;
}
}
}
}
writeln!(fmt)?;
}
Ok(())
}
}
/// Reading and writing.
impl<'tcx, 'a, Prov: Provenance, Extra, Bytes: AllocBytes>
AllocRefMut<'a, 'tcx, Prov, Extra, Bytes>
{
/// `range` is relative to this allocation reference, not the base of the allocation.
pub fn write_scalar(&mut self, range: AllocRange, val: Scalar<Prov>) -> InterpResult<'tcx> {
let range = self.range.subrange(range);
debug!("write_scalar at {:?}{range:?}: {val:?}", self.alloc_id);
Ok(self
.alloc
.write_scalar(&self.tcx, range, val)
.map_err(|e| e.to_interp_error(self.alloc_id))?)
}
/// `offset` is relative to this allocation reference, not the base of the allocation.
pub fn write_ptr_sized(&mut self, offset: Size, val: Scalar<Prov>) -> InterpResult<'tcx> {
self.write_scalar(alloc_range(offset, self.tcx.data_layout().pointer_size), val)
}
/// Mark the entire referenced range as uninitialized
pub fn write_uninit(&mut self) -> InterpResult<'tcx> {
Ok(self
.alloc
.write_uninit(&self.tcx, self.range)
.map_err(|e| e.to_interp_error(self.alloc_id))?)
}
}
impl<'tcx, 'a, Prov: Provenance, Extra, Bytes: AllocBytes> AllocRef<'a, 'tcx, Prov, Extra, Bytes> {
/// `range` is relative to this allocation reference, not the base of the allocation.
pub fn read_scalar(
&self,
range: AllocRange,
read_provenance: bool,
) -> InterpResult<'tcx, Scalar<Prov>> {
let range = self.range.subrange(range);
let res = self
.alloc
.read_scalar(&self.tcx, range, read_provenance)
.map_err(|e| e.to_interp_error(self.alloc_id))?;
debug!("read_scalar at {:?}{range:?}: {res:?}", self.alloc_id);
Ok(res)
}
/// `range` is relative to this allocation reference, not the base of the allocation.
pub fn read_integer(&self, range: AllocRange) -> InterpResult<'tcx, Scalar<Prov>> {
self.read_scalar(range, /*read_provenance*/ false)
}
/// `offset` is relative to this allocation reference, not the base of the allocation.
pub fn read_pointer(&self, offset: Size) -> InterpResult<'tcx, Scalar<Prov>> {
self.read_scalar(
alloc_range(offset, self.tcx.data_layout().pointer_size),
/*read_provenance*/ true,
)
}
/// `range` is relative to this allocation reference, not the base of the allocation.
pub fn get_bytes_strip_provenance<'b>(&'b self) -> InterpResult<'tcx, &'a [u8]> {
Ok(self
.alloc
.get_bytes_strip_provenance(&self.tcx, self.range)
.map_err(|e| e.to_interp_error(self.alloc_id))?)
}
/// Returns whether the allocation has provenance anywhere in the range of the `AllocRef`.
pub(crate) fn has_provenance(&self) -> bool {
!self.alloc.provenance().range_empty(self.range, &self.tcx)
}
}
impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
/// Reads the given number of bytes from memory, and strips their provenance if possible.
/// Returns them as a slice.
///
/// Performs appropriate bounds checks.
pub fn read_bytes_ptr_strip_provenance(
&self,
ptr: Pointer<Option<M::Provenance>>,
size: Size,
) -> InterpResult<'tcx, &[u8]> {
let Some(alloc_ref) = self.get_ptr_alloc(ptr, size, Align::ONE)? else {
// zero-sized access
return Ok(&[]);
};
// Side-step AllocRef and directly access the underlying bytes more efficiently.
// (We are staying inside the bounds here so all is good.)
Ok(alloc_ref
.alloc
.get_bytes_strip_provenance(&alloc_ref.tcx, alloc_ref.range)
.map_err(|e| e.to_interp_error(alloc_ref.alloc_id))?)
}
/// Writes the given stream of bytes into memory.
///
/// Performs appropriate bounds checks.
pub fn write_bytes_ptr(
&mut self,
ptr: Pointer<Option<M::Provenance>>,
src: impl IntoIterator<Item = u8>,
) -> InterpResult<'tcx> {
let mut src = src.into_iter();
let (lower, upper) = src.size_hint();
let len = upper.expect("can only write bounded iterators");
assert_eq!(lower, len, "can only write iterators with a precise length");
let size = Size::from_bytes(len);
let Some(alloc_ref) = self.get_ptr_alloc_mut(ptr, size, Align::ONE)? else {
// zero-sized access
assert_matches!(
src.next(),
None,
"iterator said it was empty but returned an element"
);
return Ok(());
};
// Side-step AllocRef and directly access the underlying bytes more efficiently.
// (We are staying inside the bounds here so all is good.)
let alloc_id = alloc_ref.alloc_id;
let bytes = alloc_ref
.alloc
.get_bytes_mut(&alloc_ref.tcx, alloc_ref.range)
.map_err(move |e| e.to_interp_error(alloc_id))?;
// `zip` would stop when the first iterator ends; we want to definitely
// cover all of `bytes`.
for dest in bytes {
*dest = src.next().expect("iterator was shorter than it said it would be");
}
assert_matches!(src.next(), None, "iterator was longer than it said it would be");
Ok(())
}
pub fn mem_copy(
&mut self,
src: Pointer<Option<M::Provenance>>,
src_align: Align,
dest: Pointer<Option<M::Provenance>>,
dest_align: Align,
size: Size,
nonoverlapping: bool,
) -> InterpResult<'tcx> {
self.mem_copy_repeatedly(src, src_align, dest, dest_align, size, 1, nonoverlapping)
}
pub fn mem_copy_repeatedly(
&mut self,
src: Pointer<Option<M::Provenance>>,
src_align: Align,
dest: Pointer<Option<M::Provenance>>,
dest_align: Align,
size: Size,
num_copies: u64,
nonoverlapping: bool,
) -> InterpResult<'tcx> {
let tcx = self.tcx;
// We need to do our own bounds-checks.
let src_parts = self.get_ptr_access(src, size, src_align)?;
let dest_parts = self.get_ptr_access(dest, size * num_copies, dest_align)?; // `Size` multiplication
// FIXME: we look up both allocations twice here, once before for the `check_ptr_access`
// and once below to get the underlying `&[mut] Allocation`.
// Source alloc preparations and access hooks.
let Some((src_alloc_id, src_offset, src_prov)) = src_parts else {
// 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)?;
let src_range = alloc_range(src_offset, size);
M::before_memory_read(
*tcx,
&self.machine,
&src_alloc.extra,
(src_alloc_id, src_prov),
src_range,
)?;
// We need the `dest` ptr for the next operation, so we get it now.
// We already did the source checks and called the hooks so we are good to return early.
let Some((dest_alloc_id, dest_offset, dest_prov)) = dest_parts else {
// Zero-sized *destination*.
return Ok(());
};
// 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.
// 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 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)?;
let dest_range = alloc_range(dest_offset, size * num_copies);
M::before_memory_write(
*tcx,
extra,
&mut dest_alloc.extra,
(dest_alloc_id, dest_prov),
dest_range,
)?;
let dest_bytes = dest_alloc
.get_bytes_mut_ptr(&tcx, dest_range)
.map_err(|e| e.to_interp_error(dest_alloc_id))?
.as_mut_ptr();
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.
// This also avoids writing to the target bytes so that the backing allocation is never
// touched if the bytes stay uninitialized for the whole interpreter execution. On contemporary
// operating system this can avoid physically allocating the page.
dest_alloc
.write_uninit(&tcx, dest_range)
.map_err(|e| e.to_interp_error(dest_alloc_id))?;
// We can forget about the provenance, this is all not initialized anyway.
return Ok(());
}
// SAFE: The above indexing would have panicked if there weren't at least `size` bytes
// behind `src` and `dest`. Also, we use the overlapping-safe `ptr::copy` if `src` and
// `dest` could possibly overlap.
// The pointers above remain valid even if the `HashMap` table is moved around because they
// point into the `Vec` storing the bytes.
unsafe {
if src_alloc_id == dest_alloc_id {
if nonoverlapping {
// `Size` additions
if (src_offset <= dest_offset && src_offset + size > dest_offset)
|| (dest_offset <= src_offset && dest_offset + size > src_offset)
{
throw_ub_format!("copy_nonoverlapping called on overlapping ranges")
}
}
for i in 0..num_copies {
ptr::copy(
src_bytes,
dest_bytes.add((size * i).bytes_usize()), // `Size` multiplication
size.bytes_usize(),
);
}
} else {
for i in 0..num_copies {
ptr::copy_nonoverlapping(
src_bytes,
dest_bytes.add((size * i).bytes_usize()), // `Size` multiplication
size.bytes_usize(),
);
}
}
}
// now fill in all the "init" data
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.provenance_apply_copy(provenance);
Ok(())
}
}
/// Machine pointer introspection.
impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
/// Test if this value might be null.
/// If the machine does not support ptr-to-int casts, this is conservative.
pub fn scalar_may_be_null(&self, scalar: Scalar<M::Provenance>) -> InterpResult<'tcx, bool> {
Ok(match scalar.try_to_int() {
Ok(int) => int.is_null(),
Err(_) => {
// Can only happen during CTFE.
let ptr = scalar.to_pointer(self)?;
match self.ptr_try_get_alloc_id(ptr) {
Ok((alloc_id, offset, _)) => {
let (size, _align, _kind) = self.get_alloc_info(alloc_id);
// If the pointer is out-of-bounds, it may be null.
// Note that one-past-the-end (offset == size) is still inbounds, and never null.
offset > size
}
Err(_offset) => bug!("a non-int scalar is always a pointer"),
}
}
})
}
/// Turning a "maybe pointer" into a proper pointer (and some information
/// about where it points), or an absolute address.
pub fn ptr_try_get_alloc_id(
&self,
ptr: Pointer<Option<M::Provenance>>,
) -> Result<(AllocId, Size, M::ProvenanceExtra), u64> {
match ptr.into_pointer_or_addr() {
Ok(ptr) => match M::ptr_get_alloc(self, ptr) {
Some((alloc_id, offset, extra)) => Ok((alloc_id, offset, extra)),
None => {
assert!(M::Provenance::OFFSET_IS_ADDR);
let (_, addr) = ptr.into_parts();
Err(addr.bytes())
}
},
Err(addr) => Err(addr.bytes()),
}
}
/// Turning a "maybe pointer" into a proper pointer (and some information about where it points).
#[inline(always)]
pub fn ptr_get_alloc_id(
&self,
ptr: Pointer<Option<M::Provenance>>,
) -> InterpResult<'tcx, (AllocId, Size, M::ProvenanceExtra)> {
self.ptr_try_get_alloc_id(ptr).map_err(|offset| {
err_ub!(DanglingIntPointer(offset, CheckInAllocMsg::InboundsTest)).into()
})
}
}
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