mirror of
https://github.com/rust-lang/rust.git
synced 2025-11-13 18:13:54 +00:00
645c0fddd2
Previously, it was only put on scalars with range validity invariants like bool, was uninit was obviously invalid for those. Since then, we have normatively declared all uninit primitives to be undefined behavior and can therefore put `noundef` on them. The remaining concern was the `mem::uninitialized` function, which cause quite a lot of UB in the older parts of the ecosystem. This function now doesn't return uninit values anymore, making users of it safe from this change. The only real sources of UB where people could encounter uninit primitives are `MaybeUninit::uninit().assume_init()`, which has always be clear in the docs about being UB and from heap allocations (like reading from the spare capacity of a vec. This is hopefully rare enough to not break anything.
561 lines
23 KiB
Rust
561 lines
23 KiB
Rust
use rustc_hir as hir;
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use rustc_hir::lang_items::LangItem;
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use rustc_middle::ty::layout::{
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fn_can_unwind, FnAbiError, HasParamEnv, HasTyCtxt, LayoutCx, LayoutOf, TyAndLayout,
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};
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use rustc_middle::ty::{self, Ty, TyCtxt};
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use rustc_session::config::OptLevel;
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use rustc_span::def_id::DefId;
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use rustc_target::abi::call::{
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ArgAbi, ArgAttribute, ArgAttributes, ArgExtension, Conv, FnAbi, PassMode, Reg, RegKind,
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};
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use rustc_target::abi::*;
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use rustc_target::spec::abi::Abi as SpecAbi;
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use std::iter;
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pub fn provide(providers: &mut ty::query::Providers) {
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*providers = ty::query::Providers { fn_abi_of_fn_ptr, fn_abi_of_instance, ..*providers };
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}
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// NOTE(eddyb) this is private to avoid using it from outside of
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// `fn_abi_of_instance` - any other uses are either too high-level
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// for `Instance` (e.g. typeck would use `Ty::fn_sig` instead),
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// or should go through `FnAbi` instead, to avoid losing any
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// adjustments `fn_abi_of_instance` might be performing.
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#[tracing::instrument(level = "debug", skip(tcx, param_env))]
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fn fn_sig_for_fn_abi<'tcx>(
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tcx: TyCtxt<'tcx>,
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instance: ty::Instance<'tcx>,
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param_env: ty::ParamEnv<'tcx>,
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) -> ty::PolyFnSig<'tcx> {
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let ty = instance.ty(tcx, param_env);
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match *ty.kind() {
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ty::FnDef(..) => {
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// HACK(davidtwco,eddyb): This is a workaround for polymorphization considering
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// parameters unused if they show up in the signature, but not in the `mir::Body`
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// (i.e. due to being inside a projection that got normalized, see
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// `tests/ui/polymorphization/normalized_sig_types.rs`), and codegen not keeping
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// track of a polymorphization `ParamEnv` to allow normalizing later.
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//
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// We normalize the `fn_sig` again after substituting at a later point.
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let mut sig = match *ty.kind() {
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ty::FnDef(def_id, substs) => tcx
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.bound_fn_sig(def_id)
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.map_bound(|fn_sig| {
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tcx.normalize_erasing_regions(tcx.param_env(def_id), fn_sig)
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})
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.subst(tcx, substs),
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_ => unreachable!(),
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};
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if let ty::InstanceDef::VTableShim(..) = instance.def {
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// Modify `fn(self, ...)` to `fn(self: *mut Self, ...)`.
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sig = sig.map_bound(|mut sig| {
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let mut inputs_and_output = sig.inputs_and_output.to_vec();
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inputs_and_output[0] = tcx.mk_mut_ptr(inputs_and_output[0]);
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sig.inputs_and_output = tcx.intern_type_list(&inputs_and_output);
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sig
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});
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}
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sig
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}
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ty::Closure(def_id, substs) => {
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let sig = substs.as_closure().sig();
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let bound_vars = tcx.mk_bound_variable_kinds(
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sig.bound_vars().iter().chain(iter::once(ty::BoundVariableKind::Region(ty::BrEnv))),
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);
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let br = ty::BoundRegion {
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var: ty::BoundVar::from_usize(bound_vars.len() - 1),
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kind: ty::BoundRegionKind::BrEnv,
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};
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let env_region = ty::ReLateBound(ty::INNERMOST, br);
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let env_ty = tcx.closure_env_ty(def_id, substs, env_region).unwrap();
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let sig = sig.skip_binder();
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ty::Binder::bind_with_vars(
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tcx.mk_fn_sig(
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iter::once(env_ty).chain(sig.inputs().iter().cloned()),
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sig.output(),
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sig.c_variadic,
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sig.unsafety,
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sig.abi,
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),
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bound_vars,
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)
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}
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ty::Generator(did, substs, _) => {
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let sig = substs.as_generator().poly_sig();
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let bound_vars = tcx.mk_bound_variable_kinds(
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sig.bound_vars().iter().chain(iter::once(ty::BoundVariableKind::Region(ty::BrEnv))),
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);
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let br = ty::BoundRegion {
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var: ty::BoundVar::from_usize(bound_vars.len() - 1),
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kind: ty::BoundRegionKind::BrEnv,
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};
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let env_region = ty::ReLateBound(ty::INNERMOST, br);
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let env_ty = tcx.mk_mut_ref(tcx.mk_region(env_region), ty);
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let pin_did = tcx.require_lang_item(LangItem::Pin, None);
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let pin_adt_ref = tcx.adt_def(pin_did);
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let pin_substs = tcx.intern_substs(&[env_ty.into()]);
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let env_ty = tcx.mk_adt(pin_adt_ref, pin_substs);
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let sig = sig.skip_binder();
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// The `FnSig` and the `ret_ty` here is for a generators main
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// `Generator::resume(...) -> GeneratorState` function in case we
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// have an ordinary generator, or the `Future::poll(...) -> Poll`
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// function in case this is a special generator backing an async construct.
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let ret_ty = if tcx.generator_is_async(did) {
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let state_did = tcx.require_lang_item(LangItem::Poll, None);
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let state_adt_ref = tcx.adt_def(state_did);
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let state_substs = tcx.intern_substs(&[sig.return_ty.into()]);
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tcx.mk_adt(state_adt_ref, state_substs)
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} else {
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let state_did = tcx.require_lang_item(LangItem::GeneratorState, None);
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let state_adt_ref = tcx.adt_def(state_did);
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let state_substs = tcx.intern_substs(&[sig.yield_ty.into(), sig.return_ty.into()]);
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tcx.mk_adt(state_adt_ref, state_substs)
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};
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ty::Binder::bind_with_vars(
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tcx.mk_fn_sig(
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[env_ty, sig.resume_ty].iter(),
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&ret_ty,
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false,
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hir::Unsafety::Normal,
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rustc_target::spec::abi::Abi::Rust,
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),
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bound_vars,
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)
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}
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_ => bug!("unexpected type {:?} in Instance::fn_sig", ty),
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}
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}
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#[inline]
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fn conv_from_spec_abi(tcx: TyCtxt<'_>, abi: SpecAbi) -> Conv {
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use rustc_target::spec::abi::Abi::*;
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match tcx.sess.target.adjust_abi(abi) {
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RustIntrinsic | PlatformIntrinsic | Rust | RustCall => Conv::Rust,
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RustCold => Conv::RustCold,
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// It's the ABI's job to select this, not ours.
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System { .. } => bug!("system abi should be selected elsewhere"),
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EfiApi => bug!("eficall abi should be selected elsewhere"),
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Stdcall { .. } => Conv::X86Stdcall,
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Fastcall { .. } => Conv::X86Fastcall,
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Vectorcall { .. } => Conv::X86VectorCall,
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Thiscall { .. } => Conv::X86ThisCall,
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C { .. } => Conv::C,
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Unadjusted => Conv::C,
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Win64 { .. } => Conv::X86_64Win64,
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SysV64 { .. } => Conv::X86_64SysV,
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Aapcs { .. } => Conv::ArmAapcs,
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CCmseNonSecureCall => Conv::CCmseNonSecureCall,
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PtxKernel => Conv::PtxKernel,
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Msp430Interrupt => Conv::Msp430Intr,
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X86Interrupt => Conv::X86Intr,
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AmdGpuKernel => Conv::AmdGpuKernel,
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AvrInterrupt => Conv::AvrInterrupt,
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AvrNonBlockingInterrupt => Conv::AvrNonBlockingInterrupt,
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Wasm => Conv::C,
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// These API constants ought to be more specific...
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Cdecl { .. } => Conv::C,
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}
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}
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fn fn_abi_of_fn_ptr<'tcx>(
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tcx: TyCtxt<'tcx>,
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query: ty::ParamEnvAnd<'tcx, (ty::PolyFnSig<'tcx>, &'tcx ty::List<Ty<'tcx>>)>,
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) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, FnAbiError<'tcx>> {
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let (param_env, (sig, extra_args)) = query.into_parts();
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let cx = LayoutCx { tcx, param_env };
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fn_abi_new_uncached(&cx, sig, extra_args, None, None, false)
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}
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fn fn_abi_of_instance<'tcx>(
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tcx: TyCtxt<'tcx>,
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query: ty::ParamEnvAnd<'tcx, (ty::Instance<'tcx>, &'tcx ty::List<Ty<'tcx>>)>,
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) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, FnAbiError<'tcx>> {
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let (param_env, (instance, extra_args)) = query.into_parts();
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let sig = fn_sig_for_fn_abi(tcx, instance, param_env);
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let caller_location = if instance.def.requires_caller_location(tcx) {
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Some(tcx.caller_location_ty())
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} else {
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None
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};
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fn_abi_new_uncached(
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&LayoutCx { tcx, param_env },
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sig,
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extra_args,
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caller_location,
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Some(instance.def_id()),
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matches!(instance.def, ty::InstanceDef::Virtual(..)),
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)
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}
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// Handle safe Rust thin and fat pointers.
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fn adjust_for_rust_scalar<'tcx>(
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cx: LayoutCx<'tcx, TyCtxt<'tcx>>,
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attrs: &mut ArgAttributes,
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scalar: Scalar,
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layout: TyAndLayout<'tcx>,
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offset: Size,
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is_return: bool,
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) {
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// Booleans are always a noundef i1 that needs to be zero-extended.
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if scalar.is_bool() {
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attrs.ext(ArgExtension::Zext);
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attrs.set(ArgAttribute::NoUndef);
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return;
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}
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// Scalars which have invalid values cannot be undef.
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if !scalar.is_uninit_valid() {
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attrs.set(ArgAttribute::NoUndef);
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}
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// Only pointer types handled below.
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let Scalar::Initialized { value: Pointer, valid_range} = scalar else { return };
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if !valid_range.contains(0) {
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attrs.set(ArgAttribute::NonNull);
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}
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if let Some(pointee) = layout.pointee_info_at(&cx, offset) {
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if let Some(kind) = pointee.safe {
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attrs.pointee_align = Some(pointee.align);
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// `Box` (`UniqueBorrowed`) are not necessarily dereferenceable
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// for the entire duration of the function as they can be deallocated
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// at any time. Same for shared mutable references. If LLVM had a
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// way to say "dereferenceable on entry" we could use it here.
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attrs.pointee_size = match kind {
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PointerKind::UniqueBorrowed
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| PointerKind::UniqueBorrowedPinned
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| PointerKind::Frozen => pointee.size,
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PointerKind::SharedMutable | PointerKind::UniqueOwned => Size::ZERO,
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};
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// `Box`, `&T`, and `&mut T` cannot be undef.
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// Note that this only applies to the value of the pointer itself;
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// this attribute doesn't make it UB for the pointed-to data to be undef.
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attrs.set(ArgAttribute::NoUndef);
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// The aliasing rules for `Box<T>` are still not decided, but currently we emit
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// `noalias` for it. This can be turned off using an unstable flag.
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// See https://github.com/rust-lang/unsafe-code-guidelines/issues/326
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let noalias_for_box = cx.tcx.sess.opts.unstable_opts.box_noalias;
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// LLVM prior to version 12 had known miscompiles in the presence of noalias attributes
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// (see #54878), so it was conditionally disabled, but we don't support earlier
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// versions at all anymore. We still support turning it off using -Zmutable-noalias.
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let noalias_mut_ref = cx.tcx.sess.opts.unstable_opts.mutable_noalias;
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// `&mut` pointer parameters never alias other parameters,
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// or mutable global data
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//
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// `&T` where `T` contains no `UnsafeCell<U>` is immutable,
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// and can be marked as both `readonly` and `noalias`, as
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// LLVM's definition of `noalias` is based solely on memory
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// dependencies rather than pointer equality
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let no_alias = match kind {
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PointerKind::SharedMutable | PointerKind::UniqueBorrowedPinned => false,
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PointerKind::UniqueBorrowed => noalias_mut_ref,
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PointerKind::UniqueOwned => noalias_for_box,
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PointerKind::Frozen => true,
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};
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// We can never add `noalias` in return position; that LLVM attribute has some very surprising semantics
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// (see <https://github.com/rust-lang/unsafe-code-guidelines/issues/385#issuecomment-1368055745>).
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if no_alias && !is_return {
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attrs.set(ArgAttribute::NoAlias);
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}
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if kind == PointerKind::Frozen && !is_return {
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attrs.set(ArgAttribute::ReadOnly);
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}
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}
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}
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}
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// FIXME(eddyb) perhaps group the signature/type-containing (or all of them?)
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// arguments of this method, into a separate `struct`.
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#[tracing::instrument(level = "debug", skip(cx, caller_location, fn_def_id, force_thin_self_ptr))]
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fn fn_abi_new_uncached<'tcx>(
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cx: &LayoutCx<'tcx, TyCtxt<'tcx>>,
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sig: ty::PolyFnSig<'tcx>,
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extra_args: &[Ty<'tcx>],
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caller_location: Option<Ty<'tcx>>,
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fn_def_id: Option<DefId>,
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// FIXME(eddyb) replace this with something typed, like an `enum`.
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force_thin_self_ptr: bool,
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) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, FnAbiError<'tcx>> {
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let sig = cx.tcx.normalize_erasing_late_bound_regions(cx.param_env, sig);
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let conv = conv_from_spec_abi(cx.tcx(), sig.abi);
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let mut inputs = sig.inputs();
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let extra_args = if sig.abi == RustCall {
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assert!(!sig.c_variadic && extra_args.is_empty());
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if let Some(input) = sig.inputs().last() {
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if let ty::Tuple(tupled_arguments) = input.kind() {
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inputs = &sig.inputs()[0..sig.inputs().len() - 1];
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tupled_arguments
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} else {
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bug!(
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"argument to function with \"rust-call\" ABI \
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is not a tuple"
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);
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}
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} else {
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bug!(
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"argument to function with \"rust-call\" ABI \
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is not a tuple"
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);
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}
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} else {
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assert!(sig.c_variadic || extra_args.is_empty());
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extra_args
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};
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let target = &cx.tcx.sess.target;
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let target_env_gnu_like = matches!(&target.env[..], "gnu" | "musl" | "uclibc");
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let win_x64_gnu = target.os == "windows" && target.arch == "x86_64" && target.env == "gnu";
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let linux_s390x_gnu_like =
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target.os == "linux" && target.arch == "s390x" && target_env_gnu_like;
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let linux_sparc64_gnu_like =
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target.os == "linux" && target.arch == "sparc64" && target_env_gnu_like;
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let linux_powerpc_gnu_like =
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target.os == "linux" && target.arch == "powerpc" && target_env_gnu_like;
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use SpecAbi::*;
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let rust_abi = matches!(sig.abi, RustIntrinsic | PlatformIntrinsic | Rust | RustCall);
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let arg_of = |ty: Ty<'tcx>, arg_idx: Option<usize>| -> Result<_, FnAbiError<'tcx>> {
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let span = tracing::debug_span!("arg_of");
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let _entered = span.enter();
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let is_return = arg_idx.is_none();
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let layout = cx.layout_of(ty)?;
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let layout = if force_thin_self_ptr && arg_idx == Some(0) {
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// Don't pass the vtable, it's not an argument of the virtual fn.
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// Instead, pass just the data pointer, but give it the type `*const/mut dyn Trait`
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// or `&/&mut dyn Trait` because this is special-cased elsewhere in codegen
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make_thin_self_ptr(cx, layout)
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} else {
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layout
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};
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let mut arg = ArgAbi::new(cx, layout, |layout, scalar, offset| {
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let mut attrs = ArgAttributes::new();
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adjust_for_rust_scalar(*cx, &mut attrs, scalar, *layout, offset, is_return);
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attrs
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});
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if arg.layout.is_zst() {
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// For some forsaken reason, x86_64-pc-windows-gnu
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// doesn't ignore zero-sized struct arguments.
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// The same is true for {s390x,sparc64,powerpc}-unknown-linux-{gnu,musl,uclibc}.
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if is_return
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|| rust_abi
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|| (!win_x64_gnu
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&& !linux_s390x_gnu_like
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&& !linux_sparc64_gnu_like
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&& !linux_powerpc_gnu_like)
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{
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arg.mode = PassMode::Ignore;
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}
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}
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Ok(arg)
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};
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let mut fn_abi = FnAbi {
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ret: arg_of(sig.output(), None)?,
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args: inputs
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.iter()
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.copied()
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.chain(extra_args.iter().copied())
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.chain(caller_location)
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.enumerate()
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.map(|(i, ty)| arg_of(ty, Some(i)))
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.collect::<Result<_, _>>()?,
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c_variadic: sig.c_variadic,
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fixed_count: inputs.len() as u32,
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conv,
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can_unwind: fn_can_unwind(cx.tcx(), fn_def_id, sig.abi),
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};
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fn_abi_adjust_for_abi(cx, &mut fn_abi, sig.abi, fn_def_id)?;
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debug!("fn_abi_new_uncached = {:?}", fn_abi);
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Ok(cx.tcx.arena.alloc(fn_abi))
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}
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#[tracing::instrument(level = "trace", skip(cx))]
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fn fn_abi_adjust_for_abi<'tcx>(
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cx: &LayoutCx<'tcx, TyCtxt<'tcx>>,
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fn_abi: &mut FnAbi<'tcx, Ty<'tcx>>,
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abi: SpecAbi,
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fn_def_id: Option<DefId>,
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) -> Result<(), FnAbiError<'tcx>> {
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if abi == SpecAbi::Unadjusted {
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return Ok(());
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}
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if abi == SpecAbi::Rust
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|| abi == SpecAbi::RustCall
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|| abi == SpecAbi::RustIntrinsic
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|| abi == SpecAbi::PlatformIntrinsic
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{
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|
// Look up the deduced parameter attributes for this function, if we have its def ID and
|
|
// we're optimizing in non-incremental mode. We'll tag its parameters with those attributes
|
|
// as appropriate.
|
|
let deduced_param_attrs = if cx.tcx.sess.opts.optimize != OptLevel::No
|
|
&& cx.tcx.sess.opts.incremental.is_none()
|
|
{
|
|
fn_def_id.map(|fn_def_id| cx.tcx.deduced_param_attrs(fn_def_id)).unwrap_or_default()
|
|
} else {
|
|
&[]
|
|
};
|
|
|
|
let fixup = |arg: &mut ArgAbi<'tcx, Ty<'tcx>>, arg_idx: Option<usize>| {
|
|
if arg.is_ignore() {
|
|
return;
|
|
}
|
|
|
|
match arg.layout.abi {
|
|
Abi::Aggregate { .. } => {}
|
|
|
|
// This is a fun case! The gist of what this is doing is
|
|
// that we want callers and callees to always agree on the
|
|
// ABI of how they pass SIMD arguments. If we were to *not*
|
|
// make these arguments indirect then they'd be immediates
|
|
// in LLVM, which means that they'd used whatever the
|
|
// appropriate ABI is for the callee and the caller. That
|
|
// means, for example, if the caller doesn't have AVX
|
|
// enabled but the callee does, then passing an AVX argument
|
|
// across this boundary would cause corrupt data to show up.
|
|
//
|
|
// This problem is fixed by unconditionally passing SIMD
|
|
// arguments through memory between callers and callees
|
|
// which should get them all to agree on ABI regardless of
|
|
// target feature sets. Some more information about this
|
|
// issue can be found in #44367.
|
|
//
|
|
// Note that the platform intrinsic ABI is exempt here as
|
|
// that's how we connect up to LLVM and it's unstable
|
|
// anyway, we control all calls to it in libstd.
|
|
Abi::Vector { .. }
|
|
if abi != SpecAbi::PlatformIntrinsic
|
|
&& cx.tcx.sess.target.simd_types_indirect =>
|
|
{
|
|
arg.make_indirect();
|
|
return;
|
|
}
|
|
|
|
_ => return,
|
|
}
|
|
|
|
let size = arg.layout.size;
|
|
if arg.layout.is_unsized() || size > Pointer.size(cx) {
|
|
arg.make_indirect();
|
|
} else {
|
|
// We want to pass small aggregates as immediates, but using
|
|
// a LLVM aggregate type for this leads to bad optimizations,
|
|
// so we pick an appropriately sized integer type instead.
|
|
arg.cast_to(Reg { kind: RegKind::Integer, size });
|
|
}
|
|
|
|
// If we deduced that this parameter was read-only, add that to the attribute list now.
|
|
//
|
|
// The `readonly` parameter only applies to pointers, so we can only do this if the
|
|
// argument was passed indirectly. (If the argument is passed directly, it's an SSA
|
|
// value, so it's implicitly immutable.)
|
|
if let (Some(arg_idx), &mut PassMode::Indirect { ref mut attrs, .. }) =
|
|
(arg_idx, &mut arg.mode)
|
|
{
|
|
// The `deduced_param_attrs` list could be empty if this is a type of function
|
|
// we can't deduce any parameters for, so make sure the argument index is in
|
|
// bounds.
|
|
if let Some(deduced_param_attrs) = deduced_param_attrs.get(arg_idx) {
|
|
if deduced_param_attrs.read_only {
|
|
attrs.regular.insert(ArgAttribute::ReadOnly);
|
|
debug!("added deduced read-only attribute");
|
|
}
|
|
}
|
|
}
|
|
};
|
|
|
|
fixup(&mut fn_abi.ret, None);
|
|
for (arg_idx, arg) in fn_abi.args.iter_mut().enumerate() {
|
|
fixup(arg, Some(arg_idx));
|
|
}
|
|
} else {
|
|
fn_abi.adjust_for_foreign_abi(cx, abi)?;
|
|
}
|
|
|
|
Ok(())
|
|
}
|
|
|
|
#[tracing::instrument(level = "debug", skip(cx))]
|
|
fn make_thin_self_ptr<'tcx>(
|
|
cx: &(impl HasTyCtxt<'tcx> + HasParamEnv<'tcx>),
|
|
layout: TyAndLayout<'tcx>,
|
|
) -> TyAndLayout<'tcx> {
|
|
let tcx = cx.tcx();
|
|
let fat_pointer_ty = if layout.is_unsized() {
|
|
// unsized `self` is passed as a pointer to `self`
|
|
// FIXME (mikeyhew) change this to use &own if it is ever added to the language
|
|
tcx.mk_mut_ptr(layout.ty)
|
|
} else {
|
|
match layout.abi {
|
|
Abi::ScalarPair(..) | Abi::Scalar(..) => (),
|
|
_ => bug!("receiver type has unsupported layout: {:?}", layout),
|
|
}
|
|
|
|
// In the case of Rc<Self>, we need to explicitly pass a *mut RcBox<Self>
|
|
// with a Scalar (not ScalarPair) ABI. This is a hack that is understood
|
|
// elsewhere in the compiler as a method on a `dyn Trait`.
|
|
// To get the type `*mut RcBox<Self>`, we just keep unwrapping newtypes until we
|
|
// get a built-in pointer type
|
|
let mut fat_pointer_layout = layout;
|
|
'descend_newtypes: while !fat_pointer_layout.ty.is_unsafe_ptr()
|
|
&& !fat_pointer_layout.ty.is_region_ptr()
|
|
{
|
|
for i in 0..fat_pointer_layout.fields.count() {
|
|
let field_layout = fat_pointer_layout.field(cx, i);
|
|
|
|
if !field_layout.is_zst() {
|
|
fat_pointer_layout = field_layout;
|
|
continue 'descend_newtypes;
|
|
}
|
|
}
|
|
|
|
bug!("receiver has no non-zero-sized fields {:?}", fat_pointer_layout);
|
|
}
|
|
|
|
fat_pointer_layout.ty
|
|
};
|
|
|
|
// we now have a type like `*mut RcBox<dyn Trait>`
|
|
// change its layout to that of `*mut ()`, a thin pointer, but keep the same type
|
|
// this is understood as a special case elsewhere in the compiler
|
|
let unit_ptr_ty = tcx.mk_mut_ptr(tcx.mk_unit());
|
|
|
|
TyAndLayout {
|
|
ty: fat_pointer_ty,
|
|
|
|
// NOTE(eddyb) using an empty `ParamEnv`, and `unwrap`-ing the `Result`
|
|
// should always work because the type is always `*mut ()`.
|
|
..tcx.layout_of(ty::ParamEnv::reveal_all().and(unit_ptr_ty)).unwrap()
|
|
}
|
|
}
|