rust/src/helpers.rs

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use std::convert::TryFrom;
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use std::mem;
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use rustc::mir;
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use rustc::ty::{
self,
layout::{self, LayoutOf, Size, TyLayout},
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List, TyCtxt,
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};
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use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX};
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use rustc_span::source_map::DUMMY_SP;
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use rand::RngCore;
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use crate::*;
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impl<'mir, 'tcx> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
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/// Gets an instance for a path.
fn try_resolve_did<'mir, 'tcx>(tcx: TyCtxt<'tcx>, path: &[&str]) -> Option<DefId> {
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tcx.crates()
.iter()
.find(|&&krate| tcx.original_crate_name(krate).as_str() == path[0])
.and_then(|krate| {
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let krate = DefId { krate: *krate, index: CRATE_DEF_INDEX };
let mut items = tcx.item_children(krate);
let mut path_it = path.iter().skip(1).peekable();
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while let Some(segment) = path_it.next() {
for item in mem::replace(&mut items, Default::default()).iter() {
if item.ident.name.as_str() == *segment {
if path_it.peek().is_none() {
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return Some(item.res.def_id());
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}
items = tcx.item_children(item.res.def_id());
break;
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}
}
}
None
})
}
pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
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/// Gets an instance for a path.
fn resolve_path(&self, path: &[&str]) -> ty::Instance<'tcx> {
let did = try_resolve_did(self.eval_context_ref().tcx.tcx, path)
.unwrap_or_else(|| panic!("failed to find required Rust item: {:?}", path));
ty::Instance::mono(self.eval_context_ref().tcx.tcx, did)
}
/// Evaluates the scalar at the specified path. Returns Some(val)
/// if the path could be resolved, and None otherwise
fn eval_path_scalar(
&mut self,
path: &[&str],
) -> InterpResult<'tcx, ScalarMaybeUndef<Tag>> {
let this = self.eval_context_mut();
let instance = this.resolve_path(path);
let cid = GlobalId { instance, promoted: None };
let const_val = this.const_eval_raw(cid)?;
let const_val = this.read_scalar(const_val.into())?;
return Ok(const_val);
}
/// Helper function to get a `libc` constant as a `Scalar`.
fn eval_libc(&mut self, name: &str) -> InterpResult<'tcx, Scalar<Tag>> {
self.eval_context_mut()
.eval_path_scalar(&["libc", name])?
.not_undef()
}
/// Helper function to get a `libc` constant as an `i32`.
fn eval_libc_i32(&mut self, name: &str) -> InterpResult<'tcx, i32> {
// TODO: Cache the result.
self.eval_libc(name)?.to_i32()
}
/// Helper function to get the `TyLayout` of a `libc` type
fn libc_ty_layout(&mut self, name: &str) -> InterpResult<'tcx, TyLayout<'tcx>> {
let this = self.eval_context_mut();
let ty = this.resolve_path(&["libc", name]).monomorphic_ty(*this.tcx);
this.layout_of(ty)
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}
/// Write a 0 of the appropriate size to `dest`.
fn write_null(&mut self, dest: PlaceTy<'tcx, Tag>) -> InterpResult<'tcx> {
self.eval_context_mut().write_scalar(Scalar::from_int(0, dest.layout.size), dest)
}
/// Test if this immediate equals 0.
fn is_null(&self, val: Scalar<Tag>) -> InterpResult<'tcx, bool> {
let this = self.eval_context_ref();
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let null = Scalar::null_ptr(this);
this.ptr_eq(val, null)
}
/// Turn a Scalar into an Option<NonNullScalar>
fn test_null(&self, val: Scalar<Tag>) -> InterpResult<'tcx, Option<Scalar<Tag>>> {
let this = self.eval_context_ref();
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Ok(if this.is_null(val)? { None } else { Some(val) })
}
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/// Get the `Place` for a local
fn local_place(&mut self, local: mir::Local) -> InterpResult<'tcx, PlaceTy<'tcx, Tag>> {
let this = self.eval_context_mut();
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let place = mir::Place { local: local, projection: List::empty() };
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this.eval_place(&place)
}
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/// Generate some random bytes, and write them to `dest`.
fn gen_random(&mut self, ptr: Scalar<Tag>, len: u64) -> InterpResult<'tcx> {
// Some programs pass in a null pointer and a length of 0
// to their platform's random-generation function (e.g. getrandom())
// on Linux. For compatibility with these programs, we don't perform
// any additional checks - it's okay if the pointer is invalid,
// since we wouldn't actually be writing to it.
if len == 0 {
return Ok(());
}
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let this = self.eval_context_mut();
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let mut data = vec![0; usize::try_from(len).unwrap()];
if this.machine.communicate {
// Fill the buffer using the host's rng.
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getrandom::getrandom(&mut data)
.map_err(|err| err_unsup_format!("host getrandom failed: {}", err))?;
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} else {
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let rng = this.memory.extra.rng.get_mut();
rng.fill_bytes(&mut data);
}
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this.memory.write_bytes(ptr, data.iter().copied())
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}
/// Call a function: Push the stack frame and pass the arguments.
/// For now, arguments must be scalars (so that the caller does not have to know the layout).
fn call_function(
&mut self,
f: ty::Instance<'tcx>,
args: &[Immediate<Tag>],
dest: Option<PlaceTy<'tcx, Tag>>,
stack_pop: StackPopCleanup,
) -> InterpResult<'tcx> {
let this = self.eval_context_mut();
// Push frame.
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let mir = &*this.load_mir(f.def, None)?;
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let span = this
.stack()
.last()
.and_then(Frame::current_source_info)
.map(|si| si.span)
.unwrap_or(DUMMY_SP);
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this.push_stack_frame(f, span, mir, dest, stack_pop)?;
// Initialize arguments.
let mut callee_args = this.frame().body.args_iter();
for arg in args {
let callee_arg = this.local_place(
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callee_args.next().expect("callee has fewer arguments than expected"),
)?;
this.write_immediate(*arg, callee_arg)?;
}
callee_args.next().expect_none("callee has more arguments than expected");
Ok(())
}
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/// Visits the memory covered by `place`, sensitive to freezing: the 3rd parameter
/// will be true if this is frozen, false if this is in an `UnsafeCell`.
fn visit_freeze_sensitive(
&self,
place: MPlaceTy<'tcx, Tag>,
size: Size,
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mut action: impl FnMut(Pointer<Tag>, Size, bool) -> InterpResult<'tcx>,
) -> InterpResult<'tcx> {
let this = self.eval_context_ref();
trace!("visit_frozen(place={:?}, size={:?})", *place, size);
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debug_assert_eq!(
size,
this.size_and_align_of_mplace(place)?
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.map(|(size, _)| size)
.unwrap_or_else(|| place.layout.size)
);
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// Store how far we proceeded into the place so far. Everything to the left of
// this offset has already been handled, in the sense that the frozen parts
// have had `action` called on them.
let mut end_ptr = place.ptr.assert_ptr();
// Called when we detected an `UnsafeCell` at the given offset and size.
// Calls `action` and advances `end_ptr`.
let mut unsafe_cell_action = |unsafe_cell_ptr: Scalar<Tag>, unsafe_cell_size: Size| {
let unsafe_cell_ptr = unsafe_cell_ptr.assert_ptr();
debug_assert_eq!(unsafe_cell_ptr.alloc_id, end_ptr.alloc_id);
debug_assert_eq!(unsafe_cell_ptr.tag, end_ptr.tag);
// We assume that we are given the fields in increasing offset order,
// and nothing else changes.
let unsafe_cell_offset = unsafe_cell_ptr.offset;
let end_offset = end_ptr.offset;
assert!(unsafe_cell_offset >= end_offset);
let frozen_size = unsafe_cell_offset - end_offset;
// Everything between the end_ptr and this `UnsafeCell` is frozen.
if frozen_size != Size::ZERO {
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action(end_ptr, frozen_size, /*frozen*/ true)?;
}
// This `UnsafeCell` is NOT frozen.
if unsafe_cell_size != Size::ZERO {
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action(unsafe_cell_ptr, unsafe_cell_size, /*frozen*/ false)?;
}
// Update end end_ptr.
end_ptr = unsafe_cell_ptr.wrapping_offset(unsafe_cell_size, this);
// Done
Ok(())
};
// Run a visitor
{
let mut visitor = UnsafeCellVisitor {
ecx: this,
unsafe_cell_action: |place| {
trace!("unsafe_cell_action on {:?}", place.ptr);
// We need a size to go on.
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let unsafe_cell_size = this
.size_and_align_of_mplace(place)?
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.map(|(size, _)| size)
// for extern types, just cover what we can
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.unwrap_or_else(|| place.layout.size);
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// Now handle this `UnsafeCell`, unless it is empty.
if unsafe_cell_size != Size::ZERO {
unsafe_cell_action(place.ptr, unsafe_cell_size)
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} else {
Ok(())
}
},
};
visitor.visit_value(place)?;
}
// The part between the end_ptr and the end of the place is also frozen.
// So pretend there is a 0-sized `UnsafeCell` at the end.
unsafe_cell_action(place.ptr.ptr_wrapping_offset(size, this), Size::ZERO)?;
// Done!
return Ok(());
/// Visiting the memory covered by a `MemPlace`, being aware of
/// whether we are inside an `UnsafeCell` or not.
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struct UnsafeCellVisitor<'ecx, 'mir, 'tcx, F>
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where
F: FnMut(MPlaceTy<'tcx, Tag>) -> InterpResult<'tcx>,
{
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ecx: &'ecx MiriEvalContext<'mir, 'tcx>,
unsafe_cell_action: F,
}
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impl<'ecx, 'mir, 'tcx, F> ValueVisitor<'mir, 'tcx, Evaluator<'tcx>>
for UnsafeCellVisitor<'ecx, 'mir, 'tcx, F>
where
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F: FnMut(MPlaceTy<'tcx, Tag>) -> InterpResult<'tcx>,
{
type V = MPlaceTy<'tcx, Tag>;
#[inline(always)]
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fn ecx(&self) -> &MiriEvalContext<'mir, 'tcx> {
&self.ecx
}
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// Hook to detect `UnsafeCell`.
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fn visit_value(&mut self, v: MPlaceTy<'tcx, Tag>) -> InterpResult<'tcx> {
trace!("UnsafeCellVisitor: {:?} {:?}", *v, v.layout.ty);
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let is_unsafe_cell = match v.layout.ty.kind {
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ty::Adt(adt, _) =>
Some(adt.did) == self.ecx.tcx.lang_items().unsafe_cell_type(),
_ => false,
};
if is_unsafe_cell {
// We do not have to recurse further, this is an `UnsafeCell`.
(self.unsafe_cell_action)(v)
} else if self.ecx.type_is_freeze(v.layout.ty) {
// This is `Freeze`, there cannot be an `UnsafeCell`
Ok(())
} else {
// We want to not actually read from memory for this visit. So, before
// walking this value, we have to make sure it is not a
// `Variants::Multiple`.
match v.layout.variants {
layout::Variants::Multiple { .. } => {
// A multi-variant enum, or generator, or so.
// Treat this like a union: without reading from memory,
// we cannot determine the variant we are in. Reading from
// memory would be subject to Stacked Borrows rules, leading
// to all sorts of "funny" recursion.
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// We only end up here if the type is *not* freeze, so we just call the
// `UnsafeCell` action.
(self.unsafe_cell_action)(v)
}
layout::Variants::Single { .. } => {
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// Proceed further, try to find where exactly that `UnsafeCell`
// is hiding.
self.walk_value(v)
}
}
}
}
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// Make sure we visit aggregrates in increasing offset order.
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fn visit_aggregate(
&mut self,
place: MPlaceTy<'tcx, Tag>,
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fields: impl Iterator<Item = InterpResult<'tcx, MPlaceTy<'tcx, Tag>>>,
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) -> InterpResult<'tcx> {
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match place.layout.fields {
layout::FieldPlacement::Array { .. } => {
// For the array layout, we know the iterator will yield sorted elements so
// we can avoid the allocation.
self.walk_aggregate(place, fields)
}
layout::FieldPlacement::Arbitrary { .. } => {
// Gather the subplaces and sort them before visiting.
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let mut places =
fields.collect::<InterpResult<'tcx, Vec<MPlaceTy<'tcx, Tag>>>>()?;
places.sort_by_key(|place| place.ptr.assert_ptr().offset);
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self.walk_aggregate(place, places.into_iter().map(Ok))
}
layout::FieldPlacement::Union { .. } => {
// Uh, what?
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bug!("a union is not an aggregate we should ever visit")
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}
}
}
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// We have to do *something* for unions.
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fn visit_union(&mut self, v: MPlaceTy<'tcx, Tag>, fields: usize) -> InterpResult<'tcx> {
assert!(fields > 0); // we should never reach "pseudo-unions" with 0 fields, like primitives
// With unions, we fall back to whatever the type says, to hopefully be consistent
// with LLVM IR.
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// FIXME: are we consistent, and is this really the behavior we want?
let frozen = self.ecx.type_is_freeze(v.layout.ty);
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if frozen { Ok(()) } else { (self.unsafe_cell_action)(v) }
}
}
}
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// Writes several `ImmTy`s contiguosly into memory. This is useful when you have to pack
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// different values into a struct.
fn write_packed_immediates(
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&mut self,
place: MPlaceTy<'tcx, Tag>,
imms: &[ImmTy<'tcx, Tag>],
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) -> InterpResult<'tcx> {
let this = self.eval_context_mut();
let mut offset = Size::from_bytes(0);
for &imm in imms {
this.write_immediate_to_mplace(
*imm,
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place.offset(offset, MemPlaceMeta::None, imm.layout, &*this.tcx)?,
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)?;
offset += imm.layout.size;
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}
Ok(())
}
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/// Helper function used inside the shims of foreign functions to check that isolation is
/// disabled. It returns an error using the `name` of the foreign function if this is not the
/// case.
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fn check_no_isolation(&self, name: &str) -> InterpResult<'tcx> {
if !self.eval_context_ref().machine.communicate {
throw_machine_stop!(TerminationInfo::UnsupportedInIsolation(format!(
"`{}` not available when isolation is enabled",
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name,
)))
}
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Ok(())
}
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/// Helper function used inside the shims of foreign functions to assert that the target OS
/// is `target_os`. It panics showing a message with the `name` of the foreign function
/// if this is not the case.
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fn assert_target_os(&self, target_os: &str, name: &str) {
assert_eq!(
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self.eval_context_ref().tcx.sess.target.target.target_os,
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target_os,
"`{}` is only available on the `{}` target OS",
name,
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target_os,
)
}
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/// Sets the last error variable.
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fn set_last_error(&mut self, scalar: Scalar<Tag>) -> InterpResult<'tcx> {
let this = self.eval_context_mut();
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let errno_place = this.machine.last_error.unwrap();
this.write_scalar(scalar, errno_place.into())
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}
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/// Gets the last error variable.
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fn get_last_error(&self) -> InterpResult<'tcx, Scalar<Tag>> {
let this = self.eval_context_ref();
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let errno_place = this.machine.last_error.unwrap();
this.read_scalar(errno_place.into())?.not_undef()
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}
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/// Sets the last OS error using a `std::io::Error`. This function tries to produce the most
/// similar OS error from the `std::io::ErrorKind` and sets it as the last OS error.
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fn set_last_error_from_io_error(&mut self, e: std::io::Error) -> InterpResult<'tcx> {
use std::io::ErrorKind::*;
let this = self.eval_context_mut();
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let target = &this.tcx.sess.target.target;
let last_error = if target.options.target_family == Some("unix".to_owned()) {
this.eval_libc(match e.kind() {
ConnectionRefused => "ECONNREFUSED",
ConnectionReset => "ECONNRESET",
PermissionDenied => "EPERM",
BrokenPipe => "EPIPE",
NotConnected => "ENOTCONN",
ConnectionAborted => "ECONNABORTED",
AddrNotAvailable => "EADDRNOTAVAIL",
AddrInUse => "EADDRINUSE",
NotFound => "ENOENT",
Interrupted => "EINTR",
InvalidInput => "EINVAL",
TimedOut => "ETIMEDOUT",
AlreadyExists => "EEXIST",
WouldBlock => "EWOULDBLOCK",
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_ => {
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throw_unsup_format!("io error {} cannot be transformed into a raw os error", e)
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}
})?
} else {
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// FIXME: we have to implement the Windows equivalent of this.
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throw_unsup_format!(
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"setting the last OS error from an io::Error is unsupported for {}.",
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target.target_os
)
};
this.set_last_error(last_error)
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}
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/// Helper function that consumes an `std::io::Result<T>` and returns an
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/// `InterpResult<'tcx,T>::Ok` instead. In case the result is an error, this function returns
/// `Ok(-1)` and sets the last OS error accordingly.
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///
/// This function uses `T: From<i32>` instead of `i32` directly because some IO related
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/// functions return different integer types (like `read`, that returns an `i64`).
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fn try_unwrap_io_result<T: From<i32>>(
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&mut self,
result: std::io::Result<T>,
) -> InterpResult<'tcx, T> {
match result {
Ok(ok) => Ok(ok),
Err(e) => {
self.eval_context_mut().set_last_error_from_io_error(e)?;
Ok((-1).into())
}
}
}
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}
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pub fn immty_from_int_checked<'tcx>(
int: impl Into<i128>,
layout: TyLayout<'tcx>,
) -> InterpResult<'tcx, ImmTy<'tcx, Tag>> {
let int = int.into();
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Ok(ImmTy::try_from_int(int, layout).ok_or_else(|| {
err_unsup_format!("signed value {:#x} does not fit in {} bits", int, layout.size.bits())
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})?)
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}
pub fn immty_from_uint_checked<'tcx>(
int: impl Into<u128>,
layout: TyLayout<'tcx>,
) -> InterpResult<'tcx, ImmTy<'tcx, Tag>> {
let int = int.into();
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Ok(ImmTy::try_from_uint(int, layout).ok_or_else(|| {
err_unsup_format!("unsigned value {:#x} does not fit in {} bits", int, layout.size.bits())
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})?)
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}