miri/helpers.rs
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use std::collections::BTreeSet;
use std::num::NonZero;
use std::sync::Mutex;
use std::time::Duration;
use std::{cmp, iter};
use rand::RngCore;
use rustc_abi::{Align, ExternAbi, FieldIdx, FieldsShape, Size, Variants};
use rustc_apfloat::Float;
use rustc_apfloat::ieee::{Double, Half, Quad, Single};
use rustc_hir::Safety;
use rustc_hir::def::{DefKind, Namespace};
use rustc_hir::def_id::{CRATE_DEF_INDEX, CrateNum, DefId, LOCAL_CRATE};
use rustc_index::IndexVec;
use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
use rustc_middle::middle::dependency_format::Linkage;
use rustc_middle::middle::exported_symbols::ExportedSymbol;
use rustc_middle::ty::layout::{FnAbiOf, LayoutOf, MaybeResult, TyAndLayout};
use rustc_middle::ty::{self, FloatTy, IntTy, Ty, TyCtxt, UintTy};
use rustc_session::config::CrateType;
use rustc_span::{Span, Symbol};
use crate::*;
/// Indicates which kind of access is being performed.
#[derive(Copy, Clone, Hash, PartialEq, Eq, Debug)]
pub enum AccessKind {
Read,
Write,
}
/// Gets an instance for a path.
///
/// A `None` namespace indicates we are looking for a module.
fn try_resolve_did(tcx: TyCtxt<'_>, path: &[&str], namespace: Option<Namespace>) -> Option<DefId> {
/// Yield all children of the given item, that have the given name.
fn find_children<'tcx: 'a, 'a>(
tcx: TyCtxt<'tcx>,
item: DefId,
name: &'a str,
) -> impl Iterator<Item = DefId> + 'a {
tcx.module_children(item)
.iter()
.filter(move |item| item.ident.name.as_str() == name)
.map(move |item| item.res.def_id())
}
// Take apart the path: leading crate, a sequence of modules, and potentially a final item.
let (&crate_name, path) = path.split_first().expect("paths must have at least one segment");
let (modules, item) = if let Some(namespace) = namespace {
let (&item_name, modules) =
path.split_last().expect("non-module paths must have at least 2 segments");
(modules, Some((item_name, namespace)))
} else {
(path, None)
};
// There may be more than one crate with this name. We try them all.
// (This is particularly relevant when running `std` tests as then there are two `std` crates:
// the one in the sysroot and the one locally built by `cargo test`.)
// FIXME: can we prefer the one from the sysroot?
'crates: for krate in
tcx.crates(()).iter().filter(|&&krate| tcx.crate_name(krate).as_str() == crate_name)
{
let mut cur_item = DefId { krate: *krate, index: CRATE_DEF_INDEX };
// Go over the modules.
for &segment in modules {
let Some(next_item) = find_children(tcx, cur_item, segment)
.find(|item| tcx.def_kind(item) == DefKind::Mod)
else {
continue 'crates;
};
cur_item = next_item;
}
// Finally, look up the desired item in this module, if any.
match item {
Some((item_name, namespace)) => {
let Some(item) = find_children(tcx, cur_item, item_name)
.find(|item| tcx.def_kind(item).ns() == Some(namespace))
else {
continue 'crates;
};
return Some(item);
}
None => {
// Just return the module.
return Some(cur_item);
}
}
}
// Item not found in any of the crates with the right name.
None
}
/// Gets an instance for a path; fails gracefully if the path does not exist.
pub fn try_resolve_path<'tcx>(
tcx: TyCtxt<'tcx>,
path: &[&str],
namespace: Namespace,
) -> Option<ty::Instance<'tcx>> {
let did = try_resolve_did(tcx, path, Some(namespace))?;
Some(ty::Instance::mono(tcx, did))
}
/// Gets an instance for a path.
#[track_caller]
pub fn resolve_path<'tcx>(
tcx: TyCtxt<'tcx>,
path: &[&str],
namespace: Namespace,
) -> ty::Instance<'tcx> {
try_resolve_path(tcx, path, namespace)
.unwrap_or_else(|| panic!("failed to find required Rust item: {path:?}"))
}
/// Gets the layout of a type at a path.
#[track_caller]
pub fn path_ty_layout<'tcx>(cx: &impl LayoutOf<'tcx>, path: &[&str]) -> TyAndLayout<'tcx> {
let ty = resolve_path(cx.tcx(), path, Namespace::TypeNS).ty(cx.tcx(), cx.typing_env());
cx.layout_of(ty).to_result().ok().unwrap()
}
/// Call `f` for each exported symbol.
pub fn iter_exported_symbols<'tcx>(
tcx: TyCtxt<'tcx>,
mut f: impl FnMut(CrateNum, DefId) -> InterpResult<'tcx>,
) -> InterpResult<'tcx> {
// First, the symbols in the local crate. We can't use `exported_symbols` here as that
// skips `#[used]` statics (since `reachable_set` skips them in binary crates).
// So we walk all HIR items ourselves instead.
let crate_items = tcx.hir_crate_items(());
for def_id in crate_items.definitions() {
let exported = tcx.def_kind(def_id).has_codegen_attrs() && {
let codegen_attrs = tcx.codegen_fn_attrs(def_id);
codegen_attrs.contains_extern_indicator()
|| codegen_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL)
|| codegen_attrs.flags.contains(CodegenFnAttrFlags::USED)
|| codegen_attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER)
};
if exported {
f(LOCAL_CRATE, def_id.into())?;
}
}
// Next, all our dependencies.
// `dependency_formats` includes all the transitive informations needed to link a crate,
// which is what we need here since we need to dig out `exported_symbols` from all transitive
// dependencies.
let dependency_formats = tcx.dependency_formats(());
// Find the dependencies of the executable we are running.
let dependency_format = dependency_formats
.iter()
.find(|(crate_type, _)| *crate_type == CrateType::Executable)
.expect("interpreting a non-executable crate");
for cnum in dependency_format.1.iter().enumerate().filter_map(|(num, &linkage)| {
// We add 1 to the number because that's what rustc also does everywhere it
// calls `CrateNum::new`...
#[expect(clippy::arithmetic_side_effects)]
(linkage != Linkage::NotLinked).then_some(CrateNum::new(num + 1))
}) {
// We can ignore `_export_info` here: we are a Rust crate, and everything is exported
// from a Rust crate.
for &(symbol, _export_info) in tcx.exported_symbols(cnum) {
if let ExportedSymbol::NonGeneric(def_id) = symbol {
f(cnum, def_id)?;
}
}
}
interp_ok(())
}
/// Convert a softfloat type to its corresponding hostfloat type.
pub trait ToHost {
type HostFloat;
fn to_host(self) -> Self::HostFloat;
}
/// Convert a hostfloat type to its corresponding softfloat type.
pub trait ToSoft {
type SoftFloat;
fn to_soft(self) -> Self::SoftFloat;
}
impl ToHost for rustc_apfloat::ieee::Double {
type HostFloat = f64;
fn to_host(self) -> Self::HostFloat {
f64::from_bits(self.to_bits().try_into().unwrap())
}
}
impl ToSoft for f64 {
type SoftFloat = rustc_apfloat::ieee::Double;
fn to_soft(self) -> Self::SoftFloat {
Float::from_bits(self.to_bits().into())
}
}
impl ToHost for rustc_apfloat::ieee::Single {
type HostFloat = f32;
fn to_host(self) -> Self::HostFloat {
f32::from_bits(self.to_bits().try_into().unwrap())
}
}
impl ToSoft for f32 {
type SoftFloat = rustc_apfloat::ieee::Single;
fn to_soft(self) -> Self::SoftFloat {
Float::from_bits(self.to_bits().into())
}
}
impl<'tcx> EvalContextExt<'tcx> for crate::MiriInterpCx<'tcx> {}
pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
/// Checks if the given crate/module exists.
fn have_module(&self, path: &[&str]) -> bool {
try_resolve_did(*self.eval_context_ref().tcx, path, None).is_some()
}
/// Evaluates the scalar at the specified path.
fn eval_path(&self, path: &[&str]) -> MPlaceTy<'tcx> {
let this = self.eval_context_ref();
let instance = resolve_path(*this.tcx, path, Namespace::ValueNS);
// We don't give a span -- this isn't actually used directly by the program anyway.
this.eval_global(instance).unwrap_or_else(|err| {
panic!("failed to evaluate required Rust item: {path:?}\n{err:?}")
})
}
fn eval_path_scalar(&self, path: &[&str]) -> Scalar {
let this = self.eval_context_ref();
let val = this.eval_path(path);
this.read_scalar(&val)
.unwrap_or_else(|err| panic!("failed to read required Rust item: {path:?}\n{err:?}"))
}
/// Helper function to get a `libc` constant as a `Scalar`.
fn eval_libc(&self, name: &str) -> Scalar {
if self.eval_context_ref().tcx.sess.target.os == "windows" {
panic!(
"`libc` crate is not reliably available on Windows targets; Miri should not use it there"
);
}
self.eval_path_scalar(&["libc", name])
}
/// Helper function to get a `libc` constant as an `i32`.
fn eval_libc_i32(&self, name: &str) -> i32 {
// TODO: Cache the result.
self.eval_libc(name).to_i32().unwrap_or_else(|_err| {
panic!("required libc item has unexpected type (not `i32`): {name}")
})
}
/// Helper function to get a `libc` constant as an `u32`.
fn eval_libc_u32(&self, name: &str) -> u32 {
// TODO: Cache the result.
self.eval_libc(name).to_u32().unwrap_or_else(|_err| {
panic!("required libc item has unexpected type (not `u32`): {name}")
})
}
/// Helper function to get a `windows` constant as a `Scalar`.
fn eval_windows(&self, module: &str, name: &str) -> Scalar {
self.eval_context_ref().eval_path_scalar(&["std", "sys", "pal", "windows", module, name])
}
/// Helper function to get a `windows` constant as a `u32`.
fn eval_windows_u32(&self, module: &str, name: &str) -> u32 {
// TODO: Cache the result.
self.eval_windows(module, name).to_u32().unwrap_or_else(|_err| {
panic!("required Windows item has unexpected type (not `u32`): {module}::{name}")
})
}
/// Helper function to get a `windows` constant as a `u64`.
fn eval_windows_u64(&self, module: &str, name: &str) -> u64 {
// TODO: Cache the result.
self.eval_windows(module, name).to_u64().unwrap_or_else(|_err| {
panic!("required Windows item has unexpected type (not `u64`): {module}::{name}")
})
}
/// Helper function to get the `TyAndLayout` of a `libc` type
fn libc_ty_layout(&self, name: &str) -> TyAndLayout<'tcx> {
let this = self.eval_context_ref();
if this.tcx.sess.target.os == "windows" {
panic!(
"`libc` crate is not reliably available on Windows targets; Miri should not use it there"
);
}
path_ty_layout(this, &["libc", name])
}
/// Helper function to get the `TyAndLayout` of a `windows` type
fn windows_ty_layout(&self, name: &str) -> TyAndLayout<'tcx> {
let this = self.eval_context_ref();
path_ty_layout(this, &["std", "sys", "pal", "windows", "c", name])
}
/// Helper function to get `TyAndLayout` of an array that consists of `libc` type.
fn libc_array_ty_layout(&self, name: &str, size: u64) -> TyAndLayout<'tcx> {
let this = self.eval_context_ref();
let elem_ty_layout = this.libc_ty_layout(name);
let array_ty = Ty::new_array(*this.tcx, elem_ty_layout.ty, size);
this.layout_of(array_ty).unwrap()
}
/// Project to the given *named* field (which must be a struct or union type).
fn project_field_named<P: Projectable<'tcx, Provenance>>(
&self,
base: &P,
name: &str,
) -> InterpResult<'tcx, P> {
let this = self.eval_context_ref();
let adt = base.layout().ty.ty_adt_def().unwrap();
for (idx, field) in adt.non_enum_variant().fields.iter().enumerate() {
if field.name.as_str() == name {
return this.project_field(base, idx);
}
}
bug!("No field named {} in type {}", name, base.layout().ty);
}
/// Search if `base` (which must be a struct or union type) contains the `name` field.
fn projectable_has_field<P: Projectable<'tcx, Provenance>>(
&self,
base: &P,
name: &str,
) -> bool {
let adt = base.layout().ty.ty_adt_def().unwrap();
for field in adt.non_enum_variant().fields.iter() {
if field.name.as_str() == name {
return true;
}
}
false
}
/// Write an int of the appropriate size to `dest`. The target type may be signed or unsigned,
/// we try to do the right thing anyway. `i128` can fit all integer types except for `u128` so
/// this method is fine for almost all integer types.
fn write_int(
&mut self,
i: impl Into<i128>,
dest: &impl Writeable<'tcx, Provenance>,
) -> InterpResult<'tcx> {
assert!(
dest.layout().backend_repr.is_scalar(),
"write_int on non-scalar type {}",
dest.layout().ty
);
let val = if dest.layout().backend_repr.is_signed() {
Scalar::from_int(i, dest.layout().size)
} else {
// `unwrap` can only fail here if `i` is negative
Scalar::from_uint(u128::try_from(i.into()).unwrap(), dest.layout().size)
};
self.eval_context_mut().write_scalar(val, dest)
}
/// Write the first N fields of the given place.
fn write_int_fields(
&mut self,
values: &[i128],
dest: &impl Writeable<'tcx, Provenance>,
) -> InterpResult<'tcx> {
let this = self.eval_context_mut();
for (idx, &val) in values.iter().enumerate() {
let field = this.project_field(dest, idx)?;
this.write_int(val, &field)?;
}
interp_ok(())
}
/// Write the given fields of the given place.
fn write_int_fields_named(
&mut self,
values: &[(&str, i128)],
dest: &impl Writeable<'tcx, Provenance>,
) -> InterpResult<'tcx> {
let this = self.eval_context_mut();
for &(name, val) in values.iter() {
let field = this.project_field_named(dest, name)?;
this.write_int(val, &field)?;
}
interp_ok(())
}
/// Write a 0 of the appropriate size to `dest`.
fn write_null(&mut self, dest: &impl Writeable<'tcx, Provenance>) -> InterpResult<'tcx> {
self.write_int(0, dest)
}
/// Test if this pointer equals 0.
fn ptr_is_null(&self, ptr: Pointer) -> InterpResult<'tcx, bool> {
interp_ok(ptr.addr().bytes() == 0)
}
/// Generate some random bytes, and write them to `dest`.
fn gen_random(&mut self, ptr: Pointer, 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 interp_ok(());
}
let this = self.eval_context_mut();
let mut data = vec![0; usize::try_from(len).unwrap()];
if this.machine.communicate() {
// Fill the buffer using the host's rng.
getrandom::getrandom(&mut data)
.map_err(|err| err_unsup_format!("host getrandom failed: {}", err))?;
} else {
let rng = this.machine.rng.get_mut();
rng.fill_bytes(&mut data);
}
this.write_bytes_ptr(ptr, data.iter().copied())
}
/// 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).
///
/// If you do not provide a return place, a dangling zero-sized place will be created
/// for your convenience.
fn call_function(
&mut self,
f: ty::Instance<'tcx>,
caller_abi: ExternAbi,
args: &[ImmTy<'tcx>],
dest: Option<&MPlaceTy<'tcx>>,
stack_pop: StackPopCleanup,
) -> InterpResult<'tcx> {
let this = self.eval_context_mut();
// Get MIR.
let mir = this.load_mir(f.def, None)?;
let dest = match dest {
Some(dest) => dest.clone(),
None => MPlaceTy::fake_alloc_zst(this.layout_of(mir.return_ty())?),
};
// Construct a function pointer type representing the caller perspective.
let sig = this.tcx.mk_fn_sig(
args.iter().map(|a| a.layout.ty),
dest.layout.ty,
/*c_variadic*/ false,
Safety::Safe,
caller_abi,
);
let caller_fn_abi = this.fn_abi_of_fn_ptr(ty::Binder::dummy(sig), ty::List::empty())?;
this.init_stack_frame(
f,
mir,
caller_fn_abi,
&args.iter().map(|a| FnArg::Copy(a.clone().into())).collect::<Vec<_>>(),
/*with_caller_location*/ false,
&dest,
stack_pop,
)
}
/// Visits the memory covered by `place`, sensitive to freezing: the 2nd parameter
/// of `action` will be true if this is frozen, false if this is in an `UnsafeCell`.
/// The range is relative to `place`.
fn visit_freeze_sensitive(
&self,
place: &MPlaceTy<'tcx>,
size: Size,
mut action: impl FnMut(AllocRange, bool) -> InterpResult<'tcx>,
) -> InterpResult<'tcx> {
let this = self.eval_context_ref();
trace!("visit_frozen(place={:?}, size={:?})", *place, size);
debug_assert_eq!(
size,
this.size_and_align_of_mplace(place)?
.map(|(size, _)| size)
.unwrap_or_else(|| place.layout.size)
);
// 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 start_addr = place.ptr().addr();
let mut cur_addr = start_addr;
// Called when we detected an `UnsafeCell` at the given offset and size.
// Calls `action` and advances `cur_ptr`.
let mut unsafe_cell_action = |unsafe_cell_ptr: &Pointer, unsafe_cell_size: Size| {
// We assume that we are given the fields in increasing offset order,
// and nothing else changes.
let unsafe_cell_addr = unsafe_cell_ptr.addr();
assert!(unsafe_cell_addr >= cur_addr);
let frozen_size = unsafe_cell_addr - cur_addr;
// Everything between the cur_ptr and this `UnsafeCell` is frozen.
if frozen_size != Size::ZERO {
action(alloc_range(cur_addr - start_addr, frozen_size), /*frozen*/ true)?;
}
cur_addr += frozen_size;
// This `UnsafeCell` is NOT frozen.
if unsafe_cell_size != Size::ZERO {
action(
alloc_range(cur_addr - start_addr, unsafe_cell_size),
/*frozen*/ false,
)?;
}
cur_addr += unsafe_cell_size;
// Done
interp_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.
let unsafe_cell_size = this
.size_and_align_of_mplace(place)?
.map(|(size, _)| size)
// for extern types, just cover what we can
.unwrap_or_else(|| place.layout.size);
// Now handle this `UnsafeCell`, unless it is empty.
if unsafe_cell_size != Size::ZERO {
unsafe_cell_action(&place.ptr(), unsafe_cell_size)
} else {
interp_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().wrapping_offset(size, this), Size::ZERO)?;
// Done!
return interp_ok(());
/// Visiting the memory covered by a `MemPlace`, being aware of
/// whether we are inside an `UnsafeCell` or not.
struct UnsafeCellVisitor<'ecx, 'tcx, F>
where
F: FnMut(&MPlaceTy<'tcx>) -> InterpResult<'tcx>,
{
ecx: &'ecx MiriInterpCx<'tcx>,
unsafe_cell_action: F,
}
impl<'ecx, 'tcx, F> ValueVisitor<'tcx, MiriMachine<'tcx>> for UnsafeCellVisitor<'ecx, 'tcx, F>
where
F: FnMut(&MPlaceTy<'tcx>) -> InterpResult<'tcx>,
{
type V = MPlaceTy<'tcx>;
#[inline(always)]
fn ecx(&self) -> &MiriInterpCx<'tcx> {
self.ecx
}
fn aggregate_field_iter(
memory_index: &IndexVec<FieldIdx, u32>,
) -> impl Iterator<Item = FieldIdx> + 'static {
let inverse_memory_index = memory_index.invert_bijective_mapping();
inverse_memory_index.into_iter()
}
// Hook to detect `UnsafeCell`.
fn visit_value(&mut self, v: &MPlaceTy<'tcx>) -> InterpResult<'tcx> {
trace!("UnsafeCellVisitor: {:?} {:?}", *v, v.layout.ty);
let is_unsafe_cell = match v.layout.ty.kind() {
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`
interp_ok(())
} else if matches!(v.layout.fields, FieldsShape::Union(..)) {
// A (non-frozen) union. We fall back to whatever the type says.
(self.unsafe_cell_action)(v)
} else if matches!(v.layout.ty.kind(), ty::Dynamic(_, _, ty::DynStar)) {
// This needs to read the vtable pointer to proceed type-driven, but we don't
// want to reentrantly read from memory here.
(self.unsafe_cell_action)(v)
} 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 {
Variants::Multiple { .. } => {
// A multi-variant enum, or coroutine, 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.
// We only end up here if the type is *not* freeze, so we just call the
// `UnsafeCell` action.
(self.unsafe_cell_action)(v)
}
Variants::Single { .. } => {
// Proceed further, try to find where exactly that `UnsafeCell`
// is hiding.
self.walk_value(v)
}
}
}
}
fn visit_union(
&mut self,
_v: &MPlaceTy<'tcx>,
_fields: NonZero<usize>,
) -> InterpResult<'tcx> {
bug!("we should have already handled unions in `visit_value`")
}
}
}
/// 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.
fn check_no_isolation(&self, name: &str) -> InterpResult<'tcx> {
if !self.eval_context_ref().machine.communicate() {
self.reject_in_isolation(name, RejectOpWith::Abort)?;
}
interp_ok(())
}
/// Helper function used inside the shims of foreign functions which reject the op
/// when isolation is enabled. It is used to print a warning/backtrace about the rejection.
fn reject_in_isolation(&self, op_name: &str, reject_with: RejectOpWith) -> InterpResult<'tcx> {
let this = self.eval_context_ref();
match reject_with {
RejectOpWith::Abort => isolation_abort_error(op_name),
RejectOpWith::WarningWithoutBacktrace => {
// This exists to reduce verbosity; make sure we emit the warning at most once per
// operation.
static EMITTED_WARNINGS: Mutex<BTreeSet<String>> = Mutex::new(BTreeSet::new());
let mut emitted_warnings = EMITTED_WARNINGS.lock().unwrap();
if !emitted_warnings.contains(op_name) {
// First time we are seeing this.
emitted_warnings.insert(op_name.to_owned());
this.tcx
.dcx()
.warn(format!("{op_name} was made to return an error due to isolation"));
}
interp_ok(())
}
RejectOpWith::Warning => {
this.emit_diagnostic(NonHaltingDiagnostic::RejectedIsolatedOp(op_name.to_string()));
interp_ok(())
}
RejectOpWith::NoWarning => interp_ok(()), // no warning
}
}
/// 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.
fn assert_target_os(&self, target_os: &str, name: &str) {
assert_eq!(
self.eval_context_ref().tcx.sess.target.os,
target_os,
"`{name}` is only available on the `{target_os}` target OS",
)
}
/// Helper function used inside the shims of foreign functions to assert that the target OS
/// is part of the UNIX family. It panics showing a message with the `name` of the foreign function
/// if this is not the case.
fn assert_target_os_is_unix(&self, name: &str) {
assert!(self.target_os_is_unix(), "`{name}` is only available for unix targets",);
}
fn target_os_is_unix(&self) -> bool {
self.eval_context_ref().tcx.sess.target.families.iter().any(|f| f == "unix")
}
/// Dereference a pointer operand to a place using `layout` instead of the pointer's declared type
fn deref_pointer_as(
&self,
op: &impl Projectable<'tcx, Provenance>,
layout: TyAndLayout<'tcx>,
) -> InterpResult<'tcx, MPlaceTy<'tcx>> {
let this = self.eval_context_ref();
let ptr = this.read_pointer(op)?;
interp_ok(this.ptr_to_mplace(ptr, layout))
}
/// Calculates the MPlaceTy given the offset and layout of an access on an operand
fn deref_pointer_and_offset(
&self,
op: &impl Projectable<'tcx, Provenance>,
offset: u64,
base_layout: TyAndLayout<'tcx>,
value_layout: TyAndLayout<'tcx>,
) -> InterpResult<'tcx, MPlaceTy<'tcx>> {
let this = self.eval_context_ref();
let op_place = this.deref_pointer_as(op, base_layout)?;
let offset = Size::from_bytes(offset);
// Ensure that the access is within bounds.
assert!(base_layout.size >= offset + value_layout.size);
let value_place = op_place.offset(offset, value_layout, this)?;
interp_ok(value_place)
}
fn deref_pointer_and_read(
&self,
op: &impl Projectable<'tcx, Provenance>,
offset: u64,
base_layout: TyAndLayout<'tcx>,
value_layout: TyAndLayout<'tcx>,
) -> InterpResult<'tcx, Scalar> {
let this = self.eval_context_ref();
let value_place = this.deref_pointer_and_offset(op, offset, base_layout, value_layout)?;
this.read_scalar(&value_place)
}
fn deref_pointer_and_write(
&mut self,
op: &impl Projectable<'tcx, Provenance>,
offset: u64,
value: impl Into<Scalar>,
base_layout: TyAndLayout<'tcx>,
value_layout: TyAndLayout<'tcx>,
) -> InterpResult<'tcx, ()> {
let this = self.eval_context_mut();
let value_place = this.deref_pointer_and_offset(op, offset, base_layout, value_layout)?;
this.write_scalar(value, &value_place)
}
/// Parse a `timespec` struct and return it as a `std::time::Duration`. It returns `None`
/// if the value in the `timespec` struct is invalid. Some libc functions will return
/// `EINVAL` in this case.
fn read_timespec(&mut self, tp: &MPlaceTy<'tcx>) -> InterpResult<'tcx, Option<Duration>> {
let this = self.eval_context_mut();
let seconds_place = this.project_field(tp, 0)?;
let seconds_scalar = this.read_scalar(&seconds_place)?;
let seconds = seconds_scalar.to_target_isize(this)?;
let nanoseconds_place = this.project_field(tp, 1)?;
let nanoseconds_scalar = this.read_scalar(&nanoseconds_place)?;
let nanoseconds = nanoseconds_scalar.to_target_isize(this)?;
interp_ok(
try {
// tv_sec must be non-negative.
let seconds: u64 = seconds.try_into().ok()?;
// tv_nsec must be non-negative.
let nanoseconds: u32 = nanoseconds.try_into().ok()?;
if nanoseconds >= 1_000_000_000 {
// tv_nsec must not be greater than 999,999,999.
None?
}
Duration::new(seconds, nanoseconds)
},
)
}
/// Read bytes from a byte slice.
fn read_byte_slice<'a>(&'a self, slice: &ImmTy<'tcx>) -> InterpResult<'tcx, &'a [u8]>
where
'tcx: 'a,
{
let this = self.eval_context_ref();
let (ptr, len) = slice.to_scalar_pair();
let ptr = ptr.to_pointer(this)?;
let len = len.to_target_usize(this)?;
let bytes = this.read_bytes_ptr_strip_provenance(ptr, Size::from_bytes(len))?;
interp_ok(bytes)
}
/// Read a sequence of bytes until the first null terminator.
fn read_c_str<'a>(&'a self, ptr: Pointer) -> InterpResult<'tcx, &'a [u8]>
where
'tcx: 'a,
{
let this = self.eval_context_ref();
let size1 = Size::from_bytes(1);
// Step 1: determine the length.
let mut len = Size::ZERO;
loop {
// FIXME: We are re-getting the allocation each time around the loop.
// Would be nice if we could somehow "extend" an existing AllocRange.
let alloc = this.get_ptr_alloc(ptr.wrapping_offset(len, this), size1)?.unwrap(); // not a ZST, so we will get a result
let byte = alloc.read_integer(alloc_range(Size::ZERO, size1))?.to_u8()?;
if byte == 0 {
break;
} else {
len += size1;
}
}
// Step 2: get the bytes.
this.read_bytes_ptr_strip_provenance(ptr, len)
}
/// Helper function to write a sequence of bytes with an added null-terminator, which is what
/// the Unix APIs usually handle. This function returns `Ok((false, length))` without trying
/// to write if `size` is not large enough to fit the contents of `c_str` plus a null
/// terminator. It returns `Ok((true, length))` if the writing process was successful. The
/// string length returned does include the null terminator.
fn write_c_str(
&mut self,
c_str: &[u8],
ptr: Pointer,
size: u64,
) -> InterpResult<'tcx, (bool, u64)> {
// If `size` is smaller or equal than `bytes.len()`, writing `bytes` plus the required null
// terminator to memory using the `ptr` pointer would cause an out-of-bounds access.
let string_length = u64::try_from(c_str.len()).unwrap();
let string_length = string_length.strict_add(1);
if size < string_length {
return interp_ok((false, string_length));
}
self.eval_context_mut()
.write_bytes_ptr(ptr, c_str.iter().copied().chain(iter::once(0u8)))?;
interp_ok((true, string_length))
}
/// Helper function to read a sequence of unsigned integers of the given size and alignment
/// until the first null terminator.
fn read_c_str_with_char_size<T>(
&self,
mut ptr: Pointer,
size: Size,
align: Align,
) -> InterpResult<'tcx, Vec<T>>
where
T: TryFrom<u128>,
<T as TryFrom<u128>>::Error: std::fmt::Debug,
{
assert_ne!(size, Size::ZERO);
let this = self.eval_context_ref();
this.check_ptr_align(ptr, align)?;
let mut wchars = Vec::new();
loop {
// FIXME: We are re-getting the allocation each time around the loop.
// Would be nice if we could somehow "extend" an existing AllocRange.
let alloc = this.get_ptr_alloc(ptr, size)?.unwrap(); // not a ZST, so we will get a result
let wchar_int = alloc.read_integer(alloc_range(Size::ZERO, size))?.to_bits(size)?;
if wchar_int == 0 {
break;
} else {
wchars.push(wchar_int.try_into().unwrap());
ptr = ptr.wrapping_offset(size, this);
}
}
interp_ok(wchars)
}
/// Read a sequence of u16 until the first null terminator.
fn read_wide_str(&self, ptr: Pointer) -> InterpResult<'tcx, Vec<u16>> {
self.read_c_str_with_char_size(ptr, Size::from_bytes(2), Align::from_bytes(2).unwrap())
}
/// Helper function to write a sequence of u16 with an added 0x0000-terminator, which is what
/// the Windows APIs usually handle. This function returns `Ok((false, length))` without trying
/// to write if `size` is not large enough to fit the contents of `os_string` plus a null
/// terminator. It returns `Ok((true, length))` if the writing process was successful. The
/// string length returned does include the null terminator. Length is measured in units of
/// `u16.`
fn write_wide_str(
&mut self,
wide_str: &[u16],
ptr: Pointer,
size: u64,
) -> InterpResult<'tcx, (bool, u64)> {
// If `size` is smaller or equal than `bytes.len()`, writing `bytes` plus the required
// 0x0000 terminator to memory would cause an out-of-bounds access.
let string_length = u64::try_from(wide_str.len()).unwrap();
let string_length = string_length.strict_add(1);
if size < string_length {
return interp_ok((false, string_length));
}
// Store the UTF-16 string.
let size2 = Size::from_bytes(2);
let this = self.eval_context_mut();
this.check_ptr_align(ptr, Align::from_bytes(2).unwrap())?;
let mut alloc = this.get_ptr_alloc_mut(ptr, size2 * string_length)?.unwrap(); // not a ZST, so we will get a result
for (offset, wchar) in wide_str.iter().copied().chain(iter::once(0x0000)).enumerate() {
let offset = u64::try_from(offset).unwrap();
alloc.write_scalar(alloc_range(size2 * offset, size2), Scalar::from_u16(wchar))?;
}
interp_ok((true, string_length))
}
/// Read a sequence of wchar_t until the first null terminator.
/// Always returns a `Vec<u32>` no matter the size of `wchar_t`.
fn read_wchar_t_str(&self, ptr: Pointer) -> InterpResult<'tcx, Vec<u32>> {
let this = self.eval_context_ref();
let wchar_t = if this.tcx.sess.target.os == "windows" {
// We don't have libc on Windows so we have to hard-code the type ourselves.
this.machine.layouts.u16
} else {
this.libc_ty_layout("wchar_t")
};
self.read_c_str_with_char_size(ptr, wchar_t.size, wchar_t.align.abi)
}
/// Check that the ABI is what we expect.
fn check_abi<'a>(&self, abi: ExternAbi, exp_abi: ExternAbi) -> InterpResult<'a, ()> {
if abi != exp_abi {
throw_ub_format!(
"calling a function with ABI {} using caller ABI {}",
exp_abi.name(),
abi.name()
)
}
interp_ok(())
}
fn frame_in_std(&self) -> bool {
let this = self.eval_context_ref();
let frame = this.frame();
// Make an attempt to get at the instance of the function this is inlined from.
let instance: Option<_> = try {
let scope = frame.current_source_info()?.scope;
let inlined_parent = frame.body().source_scopes[scope].inlined_parent_scope?;
let source = &frame.body().source_scopes[inlined_parent];
source.inlined.expect("inlined_parent_scope points to scope without inline info").0
};
// Fall back to the instance of the function itself.
let instance = instance.unwrap_or(frame.instance());
// Now check the crate it is in. We could try to be clever here and e.g. check if this is
// the same crate as `start_fn`, but that would not work for running std tests in Miri, so
// we'd need some more hacks anyway. So we just check the name of the crate. If someone
// calls their crate `std` then we'll just let them keep the pieces.
let frame_crate = this.tcx.def_path(instance.def_id()).krate;
let crate_name = this.tcx.crate_name(frame_crate);
let crate_name = crate_name.as_str();
// On miri-test-libstd, the name of the crate is different.
crate_name == "std" || crate_name == "std_miri_test"
}
fn check_abi_and_shim_symbol_clash(
&mut self,
abi: ExternAbi,
exp_abi: ExternAbi,
link_name: Symbol,
) -> InterpResult<'tcx, ()> {
self.check_abi(abi, exp_abi)?;
if let Some((body, instance)) = self.eval_context_mut().lookup_exported_symbol(link_name)? {
// If compiler-builtins is providing the symbol, then don't treat it as a clash.
// We'll use our built-in implementation in `emulate_foreign_item_inner` for increased
// performance. Note that this means we won't catch any undefined behavior in
// compiler-builtins when running other crates, but Miri can still be run on
// compiler-builtins itself (or any crate that uses it as a normal dependency)
if self.eval_context_ref().tcx.is_compiler_builtins(instance.def_id().krate) {
return interp_ok(());
}
throw_machine_stop!(TerminationInfo::SymbolShimClashing {
link_name,
span: body.span.data(),
})
}
interp_ok(())
}
fn check_shim<'a, const N: usize>(
&mut self,
abi: ExternAbi,
exp_abi: ExternAbi,
link_name: Symbol,
args: &'a [OpTy<'tcx>],
) -> InterpResult<'tcx, &'a [OpTy<'tcx>; N]>
where
&'a [OpTy<'tcx>; N]: TryFrom<&'a [OpTy<'tcx>]>,
{
self.check_abi_and_shim_symbol_clash(abi, exp_abi, link_name)?;
check_arg_count(args)
}
/// Mark a machine allocation that was just created as immutable.
fn mark_immutable(&mut self, mplace: &MPlaceTy<'tcx>) {
let this = self.eval_context_mut();
// This got just allocated, so there definitely is a pointer here.
let provenance = mplace.ptr().into_pointer_or_addr().unwrap().provenance;
this.alloc_mark_immutable(provenance.get_alloc_id().unwrap()).unwrap();
}
/// Converts `src` from floating point to integer type `dest_ty`
/// after rounding with mode `round`.
/// Returns `None` if `f` is NaN or out of range.
fn float_to_int_checked(
&self,
src: &ImmTy<'tcx>,
cast_to: TyAndLayout<'tcx>,
round: rustc_apfloat::Round,
) -> InterpResult<'tcx, Option<ImmTy<'tcx>>> {
let this = self.eval_context_ref();
fn float_to_int_inner<'tcx, F: rustc_apfloat::Float>(
ecx: &MiriInterpCx<'tcx>,
src: F,
cast_to: TyAndLayout<'tcx>,
round: rustc_apfloat::Round,
) -> (Scalar, rustc_apfloat::Status) {
let int_size = cast_to.layout.size;
match cast_to.ty.kind() {
// Unsigned
ty::Uint(_) => {
let res = src.to_u128_r(int_size.bits_usize(), round, &mut false);
(Scalar::from_uint(res.value, int_size), res.status)
}
// Signed
ty::Int(_) => {
let res = src.to_i128_r(int_size.bits_usize(), round, &mut false);
(Scalar::from_int(res.value, int_size), res.status)
}
// Nothing else
_ =>
span_bug!(
ecx.cur_span(),
"attempted float-to-int conversion with non-int output type {}",
cast_to.ty,
),
}
}
let ty::Float(fty) = src.layout.ty.kind() else {
bug!("float_to_int_checked: non-float input type {}", src.layout.ty)
};
let (val, status) = match fty {
FloatTy::F16 =>
float_to_int_inner::<Half>(this, src.to_scalar().to_f16()?, cast_to, round),
FloatTy::F32 =>
float_to_int_inner::<Single>(this, src.to_scalar().to_f32()?, cast_to, round),
FloatTy::F64 =>
float_to_int_inner::<Double>(this, src.to_scalar().to_f64()?, cast_to, round),
FloatTy::F128 =>
float_to_int_inner::<Quad>(this, src.to_scalar().to_f128()?, cast_to, round),
};
if status.intersects(
rustc_apfloat::Status::INVALID_OP
| rustc_apfloat::Status::OVERFLOW
| rustc_apfloat::Status::UNDERFLOW,
) {
// Floating point value is NaN (flagged with INVALID_OP) or outside the range
// of values of the integer type (flagged with OVERFLOW or UNDERFLOW).
interp_ok(None)
} else {
// Floating point value can be represented by the integer type after rounding.
// The INEXACT flag is ignored on purpose to allow rounding.
interp_ok(Some(ImmTy::from_scalar(val, cast_to)))
}
}
/// Returns an integer type that is twice wide as `ty`
fn get_twice_wide_int_ty(&self, ty: Ty<'tcx>) -> Ty<'tcx> {
let this = self.eval_context_ref();
match ty.kind() {
// Unsigned
ty::Uint(UintTy::U8) => this.tcx.types.u16,
ty::Uint(UintTy::U16) => this.tcx.types.u32,
ty::Uint(UintTy::U32) => this.tcx.types.u64,
ty::Uint(UintTy::U64) => this.tcx.types.u128,
// Signed
ty::Int(IntTy::I8) => this.tcx.types.i16,
ty::Int(IntTy::I16) => this.tcx.types.i32,
ty::Int(IntTy::I32) => this.tcx.types.i64,
ty::Int(IntTy::I64) => this.tcx.types.i128,
_ => span_bug!(this.cur_span(), "unexpected type: {ty:?}"),
}
}
/// Checks that target feature `target_feature` is enabled.
///
/// If not enabled, emits an UB error that states that the feature is
/// required by `intrinsic`.
fn expect_target_feature_for_intrinsic(
&self,
intrinsic: Symbol,
target_feature: &str,
) -> InterpResult<'tcx, ()> {
let this = self.eval_context_ref();
if !this.tcx.sess.unstable_target_features.contains(&Symbol::intern(target_feature)) {
throw_ub_format!(
"attempted to call intrinsic `{intrinsic}` that requires missing target feature {target_feature}"
);
}
interp_ok(())
}
/// Lookup an array of immediates stored as a linker section of name `name`.
fn lookup_link_section(&mut self, name: &str) -> InterpResult<'tcx, Vec<ImmTy<'tcx>>> {
let this = self.eval_context_mut();
let tcx = this.tcx.tcx;
let mut array = vec![];
iter_exported_symbols(tcx, |_cnum, def_id| {
let attrs = tcx.codegen_fn_attrs(def_id);
let Some(link_section) = attrs.link_section else {
return interp_ok(());
};
if link_section.as_str() == name {
let instance = ty::Instance::mono(tcx, def_id);
let const_val = this.eval_global(instance).unwrap_or_else(|err| {
panic!(
"failed to evaluate static in required link_section: {def_id:?}\n{err:?}"
)
});
let val = this.read_immediate(&const_val)?;
array.push(val);
}
interp_ok(())
})?;
interp_ok(array)
}
}
impl<'tcx> MiriMachine<'tcx> {
/// Get the current span in the topmost function which is workspace-local and not
/// `#[track_caller]`.
/// This function is backed by a cache, and can be assumed to be very fast.
/// It will work even when the stack is empty.
pub fn current_span(&self) -> Span {
self.threads.active_thread_ref().current_span()
}
/// Returns the span of the *caller* of the current operation, again
/// walking down the stack to find the closest frame in a local crate, if the caller of the
/// current operation is not in a local crate.
/// This is useful when we are processing something which occurs on function-entry and we want
/// to point at the call to the function, not the function definition generally.
pub fn caller_span(&self) -> Span {
// We need to go down at least to the caller (len - 2), or however
// far we have to go to find a frame in a local crate which is also not #[track_caller].
let frame_idx = self.top_user_relevant_frame().unwrap();
let frame_idx = cmp::min(frame_idx, self.stack().len().saturating_sub(2));
self.stack()[frame_idx].current_span()
}
fn stack(&self) -> &[Frame<'tcx, Provenance, machine::FrameExtra<'tcx>>] {
self.threads.active_thread_stack()
}
fn top_user_relevant_frame(&self) -> Option<usize> {
self.threads.active_thread_ref().top_user_relevant_frame()
}
/// This is the source of truth for the `is_user_relevant` flag in our `FrameExtra`.
pub fn is_user_relevant(&self, frame: &Frame<'tcx, Provenance>) -> bool {
let def_id = frame.instance().def_id();
(def_id.is_local() || self.local_crates.contains(&def_id.krate))
&& !frame.instance().def.requires_caller_location(self.tcx)
}
}
/// Check that the number of args is what we expect.
pub fn check_arg_count<'a, 'tcx, const N: usize>(
args: &'a [OpTy<'tcx>],
) -> InterpResult<'tcx, &'a [OpTy<'tcx>; N]>
where
&'a [OpTy<'tcx>; N]: TryFrom<&'a [OpTy<'tcx>]>,
{
if let Ok(ops) = args.try_into() {
return interp_ok(ops);
}
throw_ub_format!("incorrect number of arguments: got {}, expected {}", args.len(), N)
}
/// Check that the number of args is at least the minumim what we expect.
pub fn check_min_arg_count<'a, 'tcx, const N: usize>(
name: &'a str,
args: &'a [OpTy<'tcx>],
) -> InterpResult<'tcx, &'a [OpTy<'tcx>; N]> {
if let Some((ops, _)) = args.split_first_chunk() {
return interp_ok(ops);
}
throw_ub_format!(
"incorrect number of arguments for `{name}`: got {}, expected at least {}",
args.len(),
N
)
}
pub fn isolation_abort_error<'tcx>(name: &str) -> InterpResult<'tcx> {
throw_machine_stop!(TerminationInfo::UnsupportedInIsolation(format!(
"{name} not available when isolation is enabled",
)))
}
/// Retrieve the list of local crates that should have been passed by cargo-miri in
/// MIRI_LOCAL_CRATES and turn them into `CrateNum`s.
pub fn get_local_crates(tcx: TyCtxt<'_>) -> Vec<CrateNum> {
// Convert the local crate names from the passed-in config into CrateNums so that they can
// be looked up quickly during execution
let local_crate_names = std::env::var("MIRI_LOCAL_CRATES")
.map(|crates| crates.split(',').map(|krate| krate.to_string()).collect::<Vec<_>>())
.unwrap_or_default();
let mut local_crates = Vec::new();
for &crate_num in tcx.crates(()) {
let name = tcx.crate_name(crate_num);
let name = name.as_str();
if local_crate_names.iter().any(|local_name| local_name == name) {
local_crates.push(crate_num);
}
}
local_crates
}
pub(crate) fn bool_to_simd_element(b: bool, size: Size) -> Scalar {
// SIMD uses all-1 as pattern for "true". In two's complement,
// -1 has all its bits set to one and `from_int` will truncate or
// sign-extend it to `size` as required.
let val = if b { -1 } else { 0 };
Scalar::from_int(val, size)
}
pub(crate) fn simd_element_to_bool(elem: ImmTy<'_>) -> InterpResult<'_, bool> {
let val = elem.to_scalar().to_int(elem.layout.size)?;
interp_ok(match val {
0 => false,
-1 => true,
_ => throw_ub_format!("each element of a SIMD mask must be all-0-bits or all-1-bits"),
})
}
/// Check whether an operation that writes to a target buffer was successful.
/// Accordingly select return value.
/// Local helper function to be used in Windows shims.
pub(crate) fn windows_check_buffer_size((success, len): (bool, u64)) -> u32 {
if success {
// If the function succeeds, the return value is the number of characters stored in the target buffer,
// not including the terminating null character.
u32::try_from(len.strict_sub(1)).unwrap()
} else {
// If the target buffer was not large enough to hold the data, the return value is the buffer size, in characters,
// required to hold the string and its terminating null character.
u32::try_from(len).unwrap()
}
}