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// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use std::fmt::Write;
use std::hash::Hash;
use syntax_pos::symbol::Symbol;
use rustc::ty::layout::{self, Size, Align, TyLayout, LayoutOf};
use rustc::ty;
use rustc_data_structures::fx::FxHashSet;
use rustc::mir::interpret::{
Scalar, AllocType, EvalResult, EvalErrorKind
};
use super::{
OpTy, MPlaceTy, ImmTy, Machine, EvalContext, ValueVisitor
};
macro_rules! validation_failure {
($what:expr, $where:expr, $details:expr) => {{
let where_ = path_format(&$where);
let where_ = if where_.is_empty() {
String::new()
} else {
format!(" at {}", where_)
};
err!(ValidationFailure(format!(
"encountered {}{}, but expected {}",
$what, where_, $details,
)))
}};
($what:expr, $where:expr) => {{
let where_ = path_format(&$where);
let where_ = if where_.is_empty() {
String::new()
} else {
format!(" at {}", where_)
};
err!(ValidationFailure(format!(
"encountered {}{}",
$what, where_,
)))
}};
}
macro_rules! try_validation {
($e:expr, $what:expr, $where:expr, $details:expr) => {{
match $e {
Ok(x) => x,
Err(_) => return validation_failure!($what, $where, $details),
}
}};
($e:expr, $what:expr, $where:expr) => {{
match $e {
Ok(x) => x,
Err(_) => return validation_failure!($what, $where),
}
}}
}
/// We want to show a nice path to the invalid field for diagnotsics,
/// but avoid string operations in the happy case where no error happens.
/// So we track a `Vec<PathElem>` where `PathElem` contains all the data we
/// need to later print something for the user.
#[derive(Copy, Clone, Debug)]
pub enum PathElem {
Field(Symbol),
ClosureVar(Symbol),
ArrayElem(usize),
TupleElem(usize),
Deref,
Tag,
DynDowncast,
}
/// State for tracking recursive validation of references
pub struct RefTracking<'tcx, Tag> {
pub seen: FxHashSet<(OpTy<'tcx, Tag>)>,
pub todo: Vec<(OpTy<'tcx, Tag>, Vec<PathElem>)>,
}
impl<'tcx, Tag: Copy+Eq+Hash> RefTracking<'tcx, Tag> {
pub fn new(op: OpTy<'tcx, Tag>) -> Self {
let mut ref_tracking = RefTracking {
seen: FxHashSet::default(),
todo: vec![(op, Vec::new())],
};
ref_tracking.seen.insert(op);
ref_tracking
}
}
/// Format a path
fn path_format(path: &Vec<PathElem>) -> String {
use self::PathElem::*;
let mut out = String::new();
for elem in path.iter() {
match elem {
Field(name) => write!(out, ".{}", name),
ClosureVar(name) => write!(out, ".<closure-var({})>", name),
TupleElem(idx) => write!(out, ".{}", idx),
ArrayElem(idx) => write!(out, "[{}]", idx),
Deref =>
// This does not match Rust syntax, but it is more readable for long paths -- and
// some of the other items here also are not Rust syntax. Actually we can't
// even use the usual syntax because we are just showing the projections,
// not the root.
write!(out, ".<deref>"),
Tag => write!(out, ".<enum-tag>"),
DynDowncast => write!(out, ".<dyn-downcast>"),
}.unwrap()
}
out
}
struct ValidityVisitor<'rt, 'a: 'rt, 'mir: 'rt, 'tcx: 'a+'rt+'mir, M: Machine<'a, 'mir, 'tcx>+'rt> {
/// The `path` may be pushed to, but the part that is present when a function
/// starts must not be changed! `visit_fields` and `visit_array` rely on
/// this stack discipline.
path: Vec<PathElem>,
ref_tracking: Option<&'rt mut RefTracking<'tcx, M::PointerTag>>,
const_mode: bool,
ecx: &'rt mut EvalContext<'a, 'mir, 'tcx, M>,
}
impl<'rt, 'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> ValidityVisitor<'rt, 'a, 'mir, 'tcx, M> {
fn push_aggregate_field_path_elem(
&mut self,
layout: TyLayout<'tcx>,
field: usize,
) {
let elem = match layout.ty.sty {
// generators and closures.
ty::Closure(def_id, _) | ty::Generator(def_id, _, _) => {
if let Some(upvar) = self.ecx.tcx.optimized_mir(def_id).upvar_decls.get(field) {
PathElem::ClosureVar(upvar.debug_name)
} else {
// Sometimes the index is beyond the number of freevars (seen
// for a generator).
PathElem::ClosureVar(Symbol::intern(&field.to_string()))
}
}
// tuples
ty::Tuple(_) => PathElem::TupleElem(field),
// enums
ty::Adt(def, ..) if def.is_enum() => {
// we might be projecting *to* a variant, or to a field *in*a variant.
match layout.variants {
layout::Variants::Single { index } =>
// Inside a variant
PathElem::Field(def.variants[index].fields[field].ident.name),
_ =>
// To a variant
PathElem::Field(def.variants[field].name)
}
}
// other ADTs
ty::Adt(def, _) => PathElem::Field(def.non_enum_variant().fields[field].ident.name),
// arrays/slices
ty::Array(..) | ty::Slice(..) => PathElem::ArrayElem(field),
// dyn traits
ty::Dynamic(..) => PathElem::DynDowncast,
// nothing else has an aggregate layout
_ => bug!("aggregate_field_path_elem: got non-aggregate type {:?}", layout.ty),
};
self.path.push(elem);
}
}
impl<'rt, 'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>>
ValueVisitor<'a, 'mir, 'tcx, M> for ValidityVisitor<'rt, 'a, 'mir, 'tcx, M>
{
type V = OpTy<'tcx, M::PointerTag>;
#[inline(always)]
fn ecx(&mut self) -> &mut EvalContext<'a, 'mir, 'tcx, M> {
&mut self.ecx
}
#[inline]
fn visit_field(
&mut self,
old_op: OpTy<'tcx, M::PointerTag>,
field: usize,
new_op: OpTy<'tcx, M::PointerTag>
) -> EvalResult<'tcx> {
// Remember the old state
let path_len = self.path.len();
// Perform operation
self.push_aggregate_field_path_elem(old_op.layout, field);
self.visit_value(new_op)?;
// Undo changes
self.path.truncate(path_len);
Ok(())
}
#[inline]
fn visit_value(&mut self, op: OpTy<'tcx, M::PointerTag>) -> EvalResult<'tcx>
{
trace!("visit_value: {:?}, {:?}", *op, op.layout);
// Translate some possible errors to something nicer.
match self.walk_value(op) {
Ok(()) => Ok(()),
Err(err) => match err.kind {
EvalErrorKind::InvalidDiscriminant(val) =>
validation_failure!(
val, self.path, "a valid enum discriminant"
),
EvalErrorKind::ReadPointerAsBytes =>
validation_failure!(
"a pointer", self.path, "plain bytes"
),
_ => Err(err),
}
}
}
fn visit_primitive(&mut self, value: ImmTy<'tcx, M::PointerTag>) -> EvalResult<'tcx>
{
// Go over all the primitive types
let ty = value.layout.ty;
match ty.sty {
ty::Bool => {
let value = value.to_scalar_or_undef();
try_validation!(value.to_bool(),
value, self.path, "a boolean");
},
ty::Char => {
let value = value.to_scalar_or_undef();
try_validation!(value.to_char(),
value, self.path, "a valid unicode codepoint");
},
ty::Float(_) | ty::Int(_) | ty::Uint(_) => {
// NOTE: Keep this in sync with the array optimization for int/float
// types below!
let size = value.layout.size;
let value = value.to_scalar_or_undef();
if self.const_mode {
// Integers/floats in CTFE: Must be scalar bits, pointers are dangerous
try_validation!(value.to_bits(size),
value, self.path, "initialized plain bits");
} else {
// At run-time, for now, we accept *anything* for these types, including
// undef. We should fix that, but let's start low.
}
}
ty::RawPtr(..) => {
// No undef allowed here. Eventually this should be consistent with
// the integer types.
let _ptr = try_validation!(value.to_scalar_ptr(),
"undefined address in pointer", self.path);
let _meta = try_validation!(value.to_meta(),
"uninitialized data in fat pointer metadata", self.path);
}
_ if ty.is_box() || ty.is_region_ptr() => {
// Handle fat pointers.
// Check metadata early, for better diagnostics
let ptr = try_validation!(value.to_scalar_ptr(),
"undefined address in pointer", self.path);
let meta = try_validation!(value.to_meta(),
"uninitialized data in fat pointer metadata", self.path);
let layout = self.ecx.layout_of(value.layout.ty.builtin_deref(true).unwrap().ty)?;
if layout.is_unsized() {
let tail = self.ecx.tcx.struct_tail(layout.ty);
match tail.sty {
ty::Dynamic(..) => {
let vtable = try_validation!(meta.unwrap().to_ptr(),
"non-pointer vtable in fat pointer", self.path);
try_validation!(self.ecx.read_drop_type_from_vtable(vtable),
"invalid drop fn in vtable", self.path);
try_validation!(self.ecx.read_size_and_align_from_vtable(vtable),
"invalid size or align in vtable", self.path);
// FIXME: More checks for the vtable.
}
ty::Slice(..) | ty::Str => {
try_validation!(meta.unwrap().to_usize(self.ecx),
"non-integer slice length in fat pointer", self.path);
}
ty::Foreign(..) => {
// Unsized, but not fat.
}
_ =>
bug!("Unexpected unsized type tail: {:?}", tail),
}
}
// Make sure this is non-NULL and aligned
let (size, align) = self.ecx.size_and_align_of(meta, layout)?
// for the purpose of validity, consider foreign types to have
// alignment and size determined by the layout (size will be 0,
// alignment should take attributes into account).
.unwrap_or_else(|| layout.size_and_align());
match self.ecx.memory.check_align(ptr, align) {
Ok(_) => {},
Err(err) => {
error!("{:?} is not aligned to {:?}", ptr, align);
match err.kind {
EvalErrorKind::InvalidNullPointerUsage =>
return validation_failure!("NULL reference", self.path),
EvalErrorKind::AlignmentCheckFailed { .. } =>
return validation_failure!("unaligned reference", self.path),
_ =>
return validation_failure!(
"dangling (out-of-bounds) reference (might be NULL at \
run-time)",
self.path
),
}
}
}
// Turn ptr into place.
// `ref_to_mplace` also calls the machine hook for (re)activating the tag,
// which in turn will (in full miri) check if the pointer is dereferencable.
let place = self.ecx.ref_to_mplace(value)?;
// Recursive checking
if let Some(ref mut ref_tracking) = self.ref_tracking {
assert!(self.const_mode, "We should only do recursie checking in const mode");
if size != Size::ZERO {
// Non-ZST also have to be dereferencable
let ptr = try_validation!(place.ptr.to_ptr(),
"integer pointer in non-ZST reference", self.path);
// Skip validation entirely for some external statics
let alloc_kind = self.ecx.tcx.alloc_map.lock().get(ptr.alloc_id);
if let Some(AllocType::Static(did)) = alloc_kind {
// `extern static` cannot be validated as they have no body.
// FIXME: Statics from other crates are also skipped.
// They might be checked at a different type, but for now we
// want to avoid recursing too deeply. This is not sound!
if !did.is_local() || self.ecx.tcx.is_foreign_item(did) {
return Ok(());
}
}
// Maintain the invariant that the place we are checking is
// already verified to be in-bounds.
try_validation!(self.ecx.memory.check_bounds(ptr, size, false),
"dangling (not entirely in bounds) reference", self.path);
}
// Check if we have encountered this pointer+layout combination
// before. Proceed recursively even for integer pointers, no
// reason to skip them! They are (recursively) valid for some ZST,
// but not for others (e.g. `!` is a ZST).
let op = place.into();
if ref_tracking.seen.insert(op) {
trace!("Recursing below ptr {:#?}", *op);
// We need to clone the path anyway, make sure it gets created
// with enough space for the additional `Deref`.
let mut new_path = Vec::with_capacity(self.path.len()+1);
new_path.clone_from(&self.path);
new_path.push(PathElem::Deref);
// Remember to come back to this later.
ref_tracking.todo.push((op, new_path));
}
}
}
ty::FnPtr(_sig) => {
let value = value.to_scalar_or_undef();
let ptr = try_validation!(value.to_ptr(),
value, self.path, "a pointer");
let _fn = try_validation!(self.ecx.memory.get_fn(ptr),
value, self.path, "a function pointer");
// FIXME: Check if the signature matches
}
// This should be all the primitive types
_ => bug!("Unexpected primitive type {}", value.layout.ty)
}
Ok(())
}
fn visit_uninhabited(&mut self) -> EvalResult<'tcx>
{
validation_failure!("a value of an uninhabited type", self.path)
}
fn visit_scalar(
&mut self,
op: OpTy<'tcx, M::PointerTag>,
layout: &layout::Scalar,
) -> EvalResult<'tcx> {
let value = self.ecx.read_scalar(op)?;
// Determine the allowed range
let (lo, hi) = layout.valid_range.clone().into_inner();
// `max_hi` is as big as the size fits
let max_hi = u128::max_value() >> (128 - op.layout.size.bits());
assert!(hi <= max_hi);
// We could also write `(hi + 1) % (max_hi + 1) == lo` but `max_hi + 1` overflows for `u128`
if (lo == 0 && hi == max_hi) || (hi + 1 == lo) {
// Nothing to check
return Ok(());
}
// At least one value is excluded. Get the bits.
let value = try_validation!(value.not_undef(),
value, self.path,
format!("something in the range {:?}", layout.valid_range));
let bits = match value {
Scalar::Ptr(ptr) => {
if lo == 1 && hi == max_hi {
// only NULL is not allowed.
// We can call `check_align` to check non-NULL-ness, but have to also look
// for function pointers.
let non_null =
self.ecx.memory.check_align(
Scalar::Ptr(ptr), Align::from_bytes(1, 1).unwrap()
).is_ok() ||
self.ecx.memory.get_fn(ptr).is_ok();
if !non_null {
// could be NULL
return validation_failure!("a potentially NULL pointer", self.path);
}
return Ok(());
} else {
// Conservatively, we reject, because the pointer *could* have this
// value.
return validation_failure!(
"a pointer",
self.path,
format!(
"something that cannot possibly be outside the (wrapping) range {:?}",
layout.valid_range
)
);
}
}
Scalar::Bits { bits, size } => {
assert_eq!(size as u64, op.layout.size.bytes());
bits
}
};
// Now compare. This is slightly subtle because this is a special "wrap-around" range.
use std::ops::RangeInclusive;
let in_range = |bound: RangeInclusive<u128>| bound.contains(&bits);
if lo > hi {
// wrapping around
if in_range(0..=hi) || in_range(lo..=max_hi) {
Ok(())
} else {
validation_failure!(
bits,
self.path,
format!("something in the range {:?} or {:?}", 0..=hi, lo..=max_hi)
)
}
} else {
if in_range(layout.valid_range.clone()) {
Ok(())
} else {
validation_failure!(
bits,
self.path,
if hi == max_hi {
format!("something greater or equal to {}", lo)
} else {
format!("something in the range {:?}", layout.valid_range)
}
)
}
}
}
fn visit_array(&mut self, op: OpTy<'tcx, M::PointerTag>) -> EvalResult<'tcx>
{
match op.layout.ty.sty {
ty::Str => {
let mplace = op.to_mem_place(); // strings are never immediate
try_validation!(self.ecx.read_str(mplace),
"uninitialized or non-UTF-8 data in str", self.path);
}
ty::Array(tys, ..) | ty::Slice(tys) if {
// This optimization applies only for integer and floating point types
// (i.e., types that can hold arbitrary bytes).
match tys.sty {
ty::Int(..) | ty::Uint(..) | ty::Float(..) => true,
_ => false,
}
} => {
let mplace = if op.layout.is_zst() {
// it's a ZST, the memory content cannot matter
MPlaceTy::dangling(op.layout, self.ecx)
} else {
// non-ZST array/slice/str cannot be immediate
op.to_mem_place()
};
// This is the length of the array/slice.
let len = mplace.len(self.ecx)?;
// This is the element type size.
let ty_size = self.ecx.layout_of(tys)?.size;
// This is the size in bytes of the whole array.
let size = ty_size * len;
// NOTE: Keep this in sync with the handling of integer and float
// types above, in `visit_primitive`.
// In run-time mode, we accept pointers in here. This is actually more
// permissive than a per-element check would be, e.g. we accept
// an &[u8] that contains a pointer even though bytewise checking would
// reject it. However, that's good: We don't inherently want
// to reject those pointers, we just do not have the machinery to
// talk about parts of a pointer.
// We also accept undef, for consistency with the type-based checks.
match self.ecx.memory.check_bytes(
mplace.ptr,
size,
/*allow_ptr_and_undef*/!self.const_mode,
) {
// In the happy case, we needn't check anything else.
Ok(()) => {},
// Some error happened, try to provide a more detailed description.
Err(err) => {
// For some errors we might be able to provide extra information
match err.kind {
EvalErrorKind::ReadUndefBytes(offset) => {
// Some byte was undefined, determine which
// element that byte belongs to so we can
// provide an index.
let i = (offset.bytes() / ty_size.bytes()) as usize;
self.path.push(PathElem::ArrayElem(i));
return validation_failure!(
"undefined bytes", self.path
)
},
// Other errors shouldn't be possible
_ => return Err(err),
}
}
}
}
_ => {
self.walk_array(op)? // default handler
}
}
Ok(())
}
}
impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M> {
/// This function checks the data at `op`. `op` is assumed to cover valid memory if it
/// is an indirect operand.
/// It will error if the bits at the destination do not match the ones described by the layout.
///
/// `ref_tracking` can be None to avoid recursive checking below references.
/// This also toggles between "run-time" (no recursion) and "compile-time" (with recursion)
/// validation (e.g., pointer values are fine in integers at runtime).
pub fn validate_operand(
&mut self,
op: OpTy<'tcx, M::PointerTag>,
path: Vec<PathElem>,
ref_tracking: Option<&mut RefTracking<'tcx, M::PointerTag>>,
const_mode: bool,
) -> EvalResult<'tcx> {
trace!("validate_operand: {:?}, {:?}", *op, op.layout.ty);
// Construct a visitor
let mut visitor = ValidityVisitor {
path,
ref_tracking,
const_mode,
ecx: self,
};
// Run it
visitor.visit_value(op)
}
}
|