mikros/rust
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

clean up internals of pointer checks; make get_size_and_align also check for fn allocations

Browse Source
This commit is contained in:
Ralf Jung 2019-06-23 16:42:51 +02:00
parent dcc8371d4e
commit c12c8a78ea
5 changed files with 69 additions and 104 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
src/librustc/mir/interpret/allocation.rs
View File

@ -6,22 +6,13 @@
use crate::ty::layout::{Size, Align};
use syntax::ast::Mutability;
use std::{iter, fmt::{self, Display}};
use std::iter;
use crate::mir;
use std::ops::{Range, Deref, DerefMut};
use rustc_data_structures::sorted_map::SortedMap;
use rustc_macros::HashStable;
use rustc_target::abi::HasDataLayout;
use std::borrow::Cow;
/// Used by `check_bounds` to indicate whether the pointer needs to be just inbounds
/// or also inbounds of a *live* allocation.
#[derive(Debug, Copy, Clone, RustcEncodable, RustcDecodable, HashStable)]
pub enum InboundsCheck {
Live,
MaybeDead,
}
#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
pub struct Allocation<Tag=(),Extra=()> {
/// The actual bytes of the allocation.

5
src/librustc/mir/interpret/mod.rs
View File

@ -17,10 +17,7 @@ macro_rules! err {
pub use self::value::{Scalar, ScalarMaybeUndef, RawConst, ConstValue};
pub use self::allocation::{
InboundsCheck, Allocation, AllocationExtra,
Relocations, UndefMask,
};
pub use self::allocation::{Allocation, AllocationExtra, Relocations, UndefMask};
pub use self::pointer::{Pointer, PointerArithmetic, CheckInAllocMsg};

2
src/librustc/mir/interpret/pointer.rs
View File

@ -1,4 +1,4 @@
use std::fmt;
use std::fmt::{self, Display};
use crate::mir;
use crate::ty::layout::{self, HasDataLayout, Size};

139
src/librustc_mir/interpret/memory.rs
View File

@ -19,7 +19,7 @@
use super::{
Pointer, AllocId, Allocation, GlobalId, AllocationExtra,
InterpResult, Scalar, InterpError, GlobalAlloc, PointerArithmetic,
Machine, AllocMap, MayLeak, ErrorHandled, CheckInAllocMsg, InboundsCheck,
Machine, AllocMap, MayLeak, ErrorHandled, CheckInAllocMsg,
InterpError::ValidationFailure,
};
@ -44,6 +44,17 @@ fn may_leak(self) -> bool {
}
}
/// Used by `get_size_and_align` to indicate whether the allocation needs to be live.
#[derive(Debug, Copy, Clone)]
pub enum AllocCheck {
/// Allocation must be live and not a function pointer.
Dereferencable,
/// Allocations needs to be live, but may be a function pointer.
Live,
/// Allocation may be dead.
MaybeDead,
}
// `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>> {
@ -248,66 +259,6 @@ pub fn deallocate(
Ok(())
}
/// Checks that the pointer is aligned AND non-NULL. This supports ZSTs in two ways:
/// You can pass a scalar, and a `Pointer` does not have to actually still be allocated.
fn check_align(
&self,
ptr: Scalar<M::PointerTag>,
required_align: Align
) -> InterpResult<'tcx> {
// Check non-NULL/Undef, extract offset
let (offset, alloc_align) = match ptr.to_bits_or_ptr(self.pointer_size(), self) {
Err(ptr) => {
// check this is not NULL -- which we can ensure only if this is in-bounds
// of some (potentially dead) allocation.
let align = self.check_ptr_bounds(ptr, InboundsCheck::MaybeDead,
CheckInAllocMsg::NullPointerTest)?;
(ptr.offset.bytes(), align)
}
Ok(data) => {
// check this is not NULL
if data == 0 {
return err!(InvalidNullPointerUsage);
}
// the "base address" is 0 and hence always aligned
(data as u64, required_align)
}
};
// Check alignment
if alloc_align.bytes() < required_align.bytes() {
return err!(AlignmentCheckFailed {
has: alloc_align,
required: required_align,
});
}
if offset % required_align.bytes() == 0 {
Ok(())
} else {
let has = offset % required_align.bytes();
err!(AlignmentCheckFailed {
has: Align::from_bytes(has).unwrap(),
required: required_align,
})
}
}
/// Checks if the pointer is "in-bounds" of *some* (live or dead) allocation. Notice that
/// a pointer pointing at the end of an allocation (i.e., at the first *inaccessible* location)
/// *is* considered in-bounds! This follows C's/LLVM's rules.
/// `liveness` can be used to rule out dead allocations. Testing in-bounds with a dead
/// allocation is useful e.g. to exclude the possibility of this pointer being NULL.
/// If you want to check bounds before doing a memory access, call `check_ptr_access`.
fn check_ptr_bounds(
&self,
ptr: Pointer<M::PointerTag>,
liveness: InboundsCheck,
msg: CheckInAllocMsg,
) -> InterpResult<'tcx, Align> {
let (allocation_size, align) = self.get_size_and_align(ptr.alloc_id, liveness)?;
ptr.check_in_alloc(allocation_size, msg)?;
Ok(align)
}
/// Check if the given scalar is allowed to do a memory access of given `size`
/// and `align`. On success, returns `None` for zero-sized accesses (where
/// nothing else is left to do) and a `Pointer` to use for the actual access otherwise.
@ -350,18 +301,35 @@ pub fn check_ptr_access(
None
}
Err(ptr) => {
// Test bounds.
self.check_ptr_bounds(
ptr.offset(size, self)?,
InboundsCheck::Live,
CheckInAllocMsg::MemoryAccessTest,
)?;
// Test align and non-NULL.
self.check_align(ptr.into(), align)?;
let (allocation_size, alloc_align) =
self.get_size_and_align(ptr.alloc_id, AllocCheck::Dereferencable)?;
// Test bounds. This also ensures non-NULL.
// It is sufficient to check this for the end pointer. The addition
// checks for overflow.
let end_ptr = ptr.offset(size, self)?;
end_ptr.check_in_alloc(allocation_size, CheckInAllocMsg::MemoryAccessTest)?;
// Test align. Check this last; if both bounds and alignment are violated
// we want the error to be about the bounds.
if alloc_align.bytes() < align.bytes() {
// The allocation itself is not aligned enough.
// FIXME: Alignment check is too strict, depending on the base address that
// got picked we might be aligned even if this check fails.
// We instead have to fall back to converting to an integer and checking
// the "real" alignment.
return err!(AlignmentCheckFailed {
has: alloc_align,
required: align,
});
}
let offset = ptr.offset.bytes();
if offset % align.bytes() != 0 {
// The offset os not aligned enough.
let has = offset % align.bytes();
return err!(AlignmentCheckFailed {
has: Align::from_bytes(has).unwrap(),
required: align,
})
}
// We can still be zero-sized in this branch, in which case we have to
// return `None`.
@ -375,8 +343,9 @@ pub fn ptr_may_be_null(
&self,
ptr: Pointer<M::PointerTag>,
) -> bool {
self.check_ptr_bounds(ptr, InboundsCheck::MaybeDead, CheckInAllocMsg::NullPointerTest)
.is_err()
let (size, _align) = self.get_size_and_align(ptr.alloc_id, AllocCheck::MaybeDead)
.expect("alloc info with MaybeDead cannot fail");
ptr.check_in_alloc(size, CheckInAllocMsg::NullPointerTest).is_err()
}
}
@ -515,13 +484,14 @@ pub fn get_mut(
}
}
/// Obtain the size and alignment of an allocation, even if that allocation has been deallocated
/// Obtain the size and alignment of an allocation, even if that allocation has
/// been deallocated.
///
/// If `liveness` is `InboundsCheck::MaybeDead`, this function always returns `Ok`
/// If `liveness` is `AllocCheck::MaybeDead`, this function always returns `Ok`.
pub fn get_size_and_align(
&self,
id: AllocId,
liveness: InboundsCheck,
liveness: AllocCheck,
) -> InterpResult<'static, (Size, Align)> {
if let Ok(alloc) = self.get(id) {
return Ok((Size::from_bytes(alloc.bytes.len() as u64), alloc.align));
@ -531,7 +501,14 @@ pub fn get_size_and_align(
let alloc = self.tcx.alloc_map.lock().get(id);
// Could also be a fn ptr or extern static
match alloc {
Some(GlobalAlloc::Function(..)) => Ok((Size::ZERO, Align::from_bytes(1).unwrap())),
Some(GlobalAlloc::Function(..)) => {
if let AllocCheck::Dereferencable = liveness {
// The caller requested no function pointers.
err!(DerefFunctionPointer)
} else {
Ok((Size::ZERO, Align::from_bytes(1).unwrap()))
}
}
// `self.get` would also work, but can cause cycles if a static refers to itself
Some(GlobalAlloc::Static(did)) => {
// The only way `get` couldn't have worked here is if this is an extern static
@ -545,15 +522,15 @@ pub fn get_size_and_align(
if let Ok(alloc) = self.get(id) {
return Ok((Size::from_bytes(alloc.bytes.len() as u64), alloc.align));
}
match liveness {
InboundsCheck::MaybeDead => {
// Must be a deallocated pointer
self.dead_alloc_map.get(&id).cloned().ok_or_else(||
if let AllocCheck::MaybeDead = liveness {
// Deallocated pointers are allowed, we should be able to find
// them in the map.
self.dead_alloc_map.get(&id).copied().ok_or_else(||
ValidationFailure("allocation missing in dead_alloc_map".to_string())
.into()
)
},
InboundsCheck::Live => err!(DanglingPointerDeref),
} else {
err!(DanglingPointerDeref)
}
},
}

2
src/librustc_mir/interpret/mod.rs
View File

@ -24,7 +24,7 @@
pub use self::place::{Place, PlaceTy, MemPlace, MPlaceTy};
pub use self::memory::{Memory, MemoryKind};
pub use self::memory::{Memory, MemoryKind, AllocCheck};
pub use self::machine::{Machine, AllocMap, MayLeak};