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Self managing allocations #55293

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Self managing allocations #55293

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1223a11
Duplicate mod.rs for better diff tracking
oli-obk Oct 23, 2018
8992146
Move `Allocation` into its own module
oli-obk Oct 23, 2018
610e4c4
Copy various functions from `memory.rs` to `allocation.rs`
oli-obk Oct 23, 2018
b667fe0
Fixup various import errors
oli-obk Oct 23, 2018
14aa7d0
Move `ScalarMaybeUndef` back to rustc
oli-obk Oct 23, 2018
3dcd1c6
Move the `memory_accessed` hook onto the `Extra` value
oli-obk Oct 23, 2018
f5a5a71
Fixup all code to work directly on the allocation instead of going th…
oli-obk Oct 23, 2018
9614f34
Forward some function calls of `Memory` to `Allocation`
oli-obk Oct 23, 2018
2d1d014
Update miri submodule
oli-obk Oct 23, 2018
f08b117
Tidy all the way
oli-obk Oct 24, 2018
d593a47
We actually have the allocation available... it can't be dangling
oli-obk Oct 24, 2018
8a6f62b
Move UndefMask and Relocations into `allocation.rs`
oli-obk Oct 25, 2018
df3cabb
Move ScalarMaybeUndef into `value.rs`
oli-obk Oct 25, 2018
de462ba
Move some functions around to keep order in sync with memory.rs
oli-obk Oct 25, 2018
8cc3faa
Add doc comment to `check_bytes`
oli-obk Oct 25, 2018
ed8b17e
Remove leftover comment
oli-obk Oct 25, 2018
5c9b456
Get rid of zst checks, the code works just fine without them
oli-obk Oct 25, 2018
9ce0803
Move `Pointer` to its own module
oli-obk Oct 25, 2018
dd194ef
Revert "Update miri submodule"
oli-obk Oct 25, 2018
0aa2aa8
Rebase fallout
oli-obk Oct 26, 2018
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706 changes: 706 additions & 0 deletions src/librustc/mir/interpret/allocation.rs
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341 changes: 11 additions & 330 deletions src/librustc/mir/interpret/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -17,27 +17,32 @@ macro_rules! err {

mod error;
mod value;
mod allocation;
mod pointer;

pub use self::error::{
EvalError, EvalResult, EvalErrorKind, AssertMessage, ConstEvalErr, struct_error,
FrameInfo, ConstEvalResult, ErrorHandled,
};

pub use self::value::{Scalar, ConstValue};
pub use self::value::{Scalar, ConstValue, ScalarMaybeUndef};

pub use self::allocation::{
Allocation, MemoryAccess, AllocationExtra,
Relocations, UndefMask,
};

pub use self::pointer::{Pointer, PointerArithmetic};

use std::fmt;
use mir;
use hir::def_id::DefId;
use ty::{self, TyCtxt, Instance};
use ty::layout::{self, Align, HasDataLayout, Size};
use ty::layout::{self, Size};
use middle::region;
use std::iter;
use std::io;
use std::ops::{Deref, DerefMut};
use std::hash::Hash;
use syntax::ast::Mutability;
use rustc_serialize::{Encoder, Decodable, Encodable};
use rustc_data_structures::sorted_map::SortedMap;
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::sync::{Lock as Mutex, HashMapExt};
use rustc_data_structures::tiny_list::TinyList;
Expand Down Expand Up @@ -78,145 +83,6 @@ pub struct GlobalId<'tcx> {
pub promoted: Option<mir::Promoted>,
}

////////////////////////////////////////////////////////////////////////////////
// Pointer arithmetic
////////////////////////////////////////////////////////////////////////////////

pub trait PointerArithmetic: layout::HasDataLayout {
// These are not supposed to be overridden.

#[inline(always)]
fn pointer_size(self) -> Size {
self.data_layout().pointer_size
}

//// Trunace the given value to the pointer size; also return whether there was an overflow
fn truncate_to_ptr(self, val: u128) -> (u64, bool) {
let max_ptr_plus_1 = 1u128 << self.pointer_size().bits();
((val % max_ptr_plus_1) as u64, val >= max_ptr_plus_1)
}

// Overflow checking only works properly on the range from -u64 to +u64.
fn overflowing_signed_offset(self, val: u64, i: i128) -> (u64, bool) {
// FIXME: is it possible to over/underflow here?
if i < 0 {
// trickery to ensure that i64::min_value() works fine
// this formula only works for true negative values, it panics for zero!
let n = u64::max_value() - (i as u64) + 1;
val.overflowing_sub(n)
} else {
self.overflowing_offset(val, i as u64)
}
}

fn overflowing_offset(self, val: u64, i: u64) -> (u64, bool) {
let (res, over1) = val.overflowing_add(i);
let (res, over2) = self.truncate_to_ptr(res as u128);
(res, over1 || over2)
}

fn signed_offset<'tcx>(self, val: u64, i: i64) -> EvalResult<'tcx, u64> {
let (res, over) = self.overflowing_signed_offset(val, i as i128);
if over { err!(Overflow(mir::BinOp::Add)) } else { Ok(res) }
}

fn offset<'tcx>(self, val: u64, i: u64) -> EvalResult<'tcx, u64> {
let (res, over) = self.overflowing_offset(val, i);
if over { err!(Overflow(mir::BinOp::Add)) } else { Ok(res) }
}

fn wrapping_signed_offset(self, val: u64, i: i64) -> u64 {
self.overflowing_signed_offset(val, i as i128).0
}
}

impl<T: layout::HasDataLayout> PointerArithmetic for T {}


/// Pointer is generic over the type that represents a reference to Allocations,
/// thus making it possible for the most convenient representation to be used in
/// each context.
///
/// Defaults to the index based and loosely coupled AllocId.
///
/// Pointer is also generic over the `Tag` associated with each pointer,
/// which is used to do provenance tracking during execution.
#[derive(Copy, Clone, Debug, Eq, PartialEq, Ord, PartialOrd, RustcEncodable, RustcDecodable, Hash)]
pub struct Pointer<Tag=(),Id=AllocId> {
pub alloc_id: Id,
pub offset: Size,
pub tag: Tag,
}

/// Produces a `Pointer` which points to the beginning of the Allocation
impl From<AllocId> for Pointer {
#[inline(always)]
fn from(alloc_id: AllocId) -> Self {
Pointer::new(alloc_id, Size::ZERO)
}
}

impl<'tcx> Pointer<()> {
#[inline(always)]
pub fn new(alloc_id: AllocId, offset: Size) -> Self {
Pointer { alloc_id, offset, tag: () }
}

#[inline(always)]
pub fn with_default_tag<Tag>(self) -> Pointer<Tag>
where Tag: Default
{
Pointer::new_with_tag(self.alloc_id, self.offset, Default::default())
}
}

impl<'tcx, Tag> Pointer<Tag> {
#[inline(always)]
pub fn new_with_tag(alloc_id: AllocId, offset: Size, tag: Tag) -> Self {
Pointer { alloc_id, offset, tag }
}

pub fn wrapping_signed_offset(self, i: i64, cx: impl HasDataLayout) -> Self {
Pointer::new_with_tag(
self.alloc_id,
Size::from_bytes(cx.data_layout().wrapping_signed_offset(self.offset.bytes(), i)),
self.tag,
)
}

pub fn overflowing_signed_offset(self, i: i128, cx: impl HasDataLayout) -> (Self, bool) {
let (res, over) = cx.data_layout().overflowing_signed_offset(self.offset.bytes(), i);
(Pointer::new_with_tag(self.alloc_id, Size::from_bytes(res), self.tag), over)
}

pub fn signed_offset(self, i: i64, cx: impl HasDataLayout) -> EvalResult<'tcx, Self> {
Ok(Pointer::new_with_tag(
self.alloc_id,
Size::from_bytes(cx.data_layout().signed_offset(self.offset.bytes(), i)?),
self.tag,
))
}

pub fn overflowing_offset(self, i: Size, cx: impl HasDataLayout) -> (Self, bool) {
let (res, over) = cx.data_layout().overflowing_offset(self.offset.bytes(), i.bytes());
(Pointer::new_with_tag(self.alloc_id, Size::from_bytes(res), self.tag), over)
}

pub fn offset(self, i: Size, cx: impl HasDataLayout) -> EvalResult<'tcx, Self> {
Ok(Pointer::new_with_tag(
self.alloc_id,
Size::from_bytes(cx.data_layout().offset(self.offset.bytes(), i.bytes())?),
self.tag
))
}

#[inline]
pub fn erase_tag(self) -> Pointer {
Pointer { alloc_id: self.alloc_id, offset: self.offset, tag: () }
}
}


#[derive(Copy, Clone, Eq, Hash, Ord, PartialEq, PartialOrd, Debug)]
pub struct AllocId(pub u64);

Expand Down Expand Up @@ -523,91 +389,6 @@ impl<'tcx, M: fmt::Debug + Eq + Hash + Clone> AllocMap<'tcx, M> {
}
}

#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
pub struct Allocation<Tag=(),Extra=()> {
/// The actual bytes of the allocation.
/// Note that the bytes of a pointer represent the offset of the pointer
pub bytes: Vec<u8>,
/// Maps from byte addresses to extra data for each pointer.
/// Only the first byte of a pointer is inserted into the map; i.e.,
/// every entry in this map applies to `pointer_size` consecutive bytes starting
/// at the given offset.
pub relocations: Relocations<Tag>,
/// Denotes undefined memory. Reading from undefined memory is forbidden in miri
pub undef_mask: UndefMask,
/// The alignment of the allocation to detect unaligned reads.
pub align: Align,
/// Whether the allocation is mutable.
/// Also used by codegen to determine if a static should be put into mutable memory,
/// which happens for `static mut` and `static` with interior mutability.
pub mutability: Mutability,
/// Extra state for the machine.
pub extra: Extra,
}

impl<Tag, Extra: Default> Allocation<Tag, Extra> {
/// Creates a read-only allocation initialized by the given bytes
pub fn from_bytes(slice: &[u8], align: Align) -> Self {
let mut undef_mask = UndefMask::new(Size::ZERO);
undef_mask.grow(Size::from_bytes(slice.len() as u64), true);
Self {
bytes: slice.to_owned(),
relocations: Relocations::new(),
undef_mask,
align,
mutability: Mutability::Immutable,
extra: Extra::default(),
}
}

pub fn from_byte_aligned_bytes(slice: &[u8]) -> Self {
Allocation::from_bytes(slice, Align::from_bytes(1, 1).unwrap())
}

pub fn undef(size: Size, align: Align) -> Self {
assert_eq!(size.bytes() as usize as u64, size.bytes());
Allocation {
bytes: vec![0; size.bytes() as usize],
relocations: Relocations::new(),
undef_mask: UndefMask::new(size),
align,
mutability: Mutability::Mutable,
extra: Extra::default(),
}
}
}

impl<'tcx> ::serialize::UseSpecializedDecodable for &'tcx Allocation {}

#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
pub struct Relocations<Tag=(), Id=AllocId>(SortedMap<Size, (Tag, Id)>);

impl<Tag, Id> Relocations<Tag, Id> {
pub fn new() -> Self {
Relocations(SortedMap::new())
}

// The caller must guarantee that the given relocations are already sorted
// by address and contain no duplicates.
pub fn from_presorted(r: Vec<(Size, (Tag, Id))>) -> Self {
Relocations(SortedMap::from_presorted_elements(r))
}
}

impl<Tag> Deref for Relocations<Tag> {
type Target = SortedMap<Size, (Tag, AllocId)>;

fn deref(&self) -> &Self::Target {
&self.0
}
}

impl<Tag> DerefMut for Relocations<Tag> {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.0
}
}

////////////////////////////////////////////////////////////////////////////////
// Methods to access integers in the target endianness
////////////////////////////////////////////////////////////////////////////////
Expand Down Expand Up @@ -650,103 +431,3 @@ pub fn truncate(value: u128, size: Size) -> u128 {
// truncate (shift left to drop out leftover values, shift right to fill with zeroes)
(value << shift) >> shift
}

////////////////////////////////////////////////////////////////////////////////
// Undefined byte tracking
////////////////////////////////////////////////////////////////////////////////

type Block = u64;
const BLOCK_SIZE: u64 = 64;

#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
pub struct UndefMask {
blocks: Vec<Block>,
len: Size,
}

impl_stable_hash_for!(struct mir::interpret::UndefMask{blocks, len});

impl UndefMask {
pub fn new(size: Size) -> Self {
let mut m = UndefMask {
blocks: vec![],
len: Size::ZERO,
};
m.grow(size, false);
m
}

/// Check whether the range `start..end` (end-exclusive) is entirely defined.
///
/// Returns `Ok(())` if it's defined. Otherwise returns the index of the byte
/// at which the first undefined access begins.
#[inline]
pub fn is_range_defined(&self, start: Size, end: Size) -> Result<(), Size> {
if end > self.len {
return Err(self.len);
}

let idx = (start.bytes()..end.bytes())
.map(|i| Size::from_bytes(i))
.find(|&i| !self.get(i));

match idx {
Some(idx) => Err(idx),
None => Ok(())
}
}

pub fn set_range(&mut self, start: Size, end: Size, new_state: bool) {
let len = self.len;
if end > len {
self.grow(end - len, new_state);
}
self.set_range_inbounds(start, end, new_state);
}

pub fn set_range_inbounds(&mut self, start: Size, end: Size, new_state: bool) {
for i in start.bytes()..end.bytes() {
self.set(Size::from_bytes(i), new_state);
}
}

#[inline]
pub fn get(&self, i: Size) -> bool {
let (block, bit) = bit_index(i);
(self.blocks[block] & 1 << bit) != 0
}

#[inline]
pub fn set(&mut self, i: Size, new_state: bool) {
let (block, bit) = bit_index(i);
if new_state {
self.blocks[block] |= 1 << bit;
} else {
self.blocks[block] &= !(1 << bit);
}
}

pub fn grow(&mut self, amount: Size, new_state: bool) {
let unused_trailing_bits = self.blocks.len() as u64 * BLOCK_SIZE - self.len.bytes();
if amount.bytes() > unused_trailing_bits {
let additional_blocks = amount.bytes() / BLOCK_SIZE + 1;
assert_eq!(additional_blocks as usize as u64, additional_blocks);
self.blocks.extend(
iter::repeat(0).take(additional_blocks as usize),
);
}
let start = self.len;
self.len += amount;
self.set_range_inbounds(start, start + amount, new_state);
}
}

#[inline]
fn bit_index(bits: Size) -> (usize, usize) {
let bits = bits.bytes();
let a = bits / BLOCK_SIZE;
let b = bits % BLOCK_SIZE;
assert_eq!(a as usize as u64, a);
assert_eq!(b as usize as u64, b);
(a as usize, b as usize)
}
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