diff options
| -rw-r--r-- | compiler/rustc_const_eval/src/interpret/machine.rs | 18 | ||||
| -rw-r--r-- | compiler/rustc_const_eval/src/interpret/memory.rs | 5 | ||||
| -rw-r--r-- | compiler/rustc_const_eval/src/interpret/place.rs | 3 | ||||
| -rw-r--r-- | compiler/rustc_const_eval/src/interpret/traits.rs | 4 | ||||
| -rw-r--r-- | compiler/rustc_middle/src/mir/interpret/mod.rs | 145 | ||||
| -rw-r--r-- | compiler/rustc_middle/src/ty/context.rs | 4 | ||||
| -rw-r--r-- | compiler/rustc_middle/src/ty/vtable.rs | 11 | ||||
| -rw-r--r-- | compiler/rustc_mir_build/src/build/expr/as_constant.rs | 6 | ||||
| -rw-r--r-- | src/tools/miri/src/lib.rs | 1 | ||||
| -rw-r--r-- | src/tools/miri/src/machine.rs | 47 | ||||
| -rw-r--r-- | src/tools/miri/tests/pass/dyn-traits.rs | 10 | ||||
| -rw-r--r-- | src/tools/miri/tests/pass/function_pointers.rs | 3 | ||||
| -rw-r--r-- | src/tools/miri/tests/pass/rc.rs | 3 |
13 files changed, 148 insertions, 112 deletions
diff --git a/compiler/rustc_const_eval/src/interpret/machine.rs b/compiler/rustc_const_eval/src/interpret/machine.rs index bdce8253b2e..1aa0d6af9ec 100644 --- a/compiler/rustc_const_eval/src/interpret/machine.rs +++ b/compiler/rustc_const_eval/src/interpret/machine.rs @@ -19,7 +19,7 @@ use rustc_target::spec::abi::Abi as CallAbi; use super::{ throw_unsup, throw_unsup_format, AllocBytes, AllocId, AllocKind, AllocRange, Allocation, ConstAllocation, CtfeProvenance, FnArg, Frame, ImmTy, InterpCx, InterpResult, MPlaceTy, - MemoryKind, Misalignment, OpTy, PlaceTy, Pointer, Provenance, + MemoryKind, Misalignment, OpTy, PlaceTy, Pointer, Provenance, CTFE_ALLOC_SALT, }; /// Data returned by [`Machine::after_stack_pop`], and consumed by @@ -575,6 +575,14 @@ pub trait Machine<'tcx>: Sized { { eval(ecx, val, span, layout) } + + /// Returns the salt to be used for a deduplicated global alloation. + /// If the allocation is for a function, the instance is provided as well + /// (this lets Miri ensure unique addresses for some functions). + fn get_global_alloc_salt( + ecx: &InterpCx<'tcx, Self>, + instance: Option<ty::Instance<'tcx>>, + ) -> usize; } /// A lot of the flexibility above is just needed for `Miri`, but all "compile-time" machines @@ -677,4 +685,12 @@ pub macro compile_time_machine(<$tcx: lifetime>) { let (prov, offset) = ptr.into_parts(); Some((prov.alloc_id(), offset, prov.immutable())) } + + #[inline(always)] + fn get_global_alloc_salt( + _ecx: &InterpCx<$tcx, Self>, + _instance: Option<ty::Instance<$tcx>>, + ) -> usize { + CTFE_ALLOC_SALT + } } diff --git a/compiler/rustc_const_eval/src/interpret/memory.rs b/compiler/rustc_const_eval/src/interpret/memory.rs index 2e5d0ae7736..910aec9b8e1 100644 --- a/compiler/rustc_const_eval/src/interpret/memory.rs +++ b/compiler/rustc_const_eval/src/interpret/memory.rs @@ -195,7 +195,10 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> { pub fn fn_ptr(&mut self, fn_val: FnVal<'tcx, M::ExtraFnVal>) -> Pointer<M::Provenance> { let id = match fn_val { - FnVal::Instance(instance) => self.tcx.reserve_and_set_fn_alloc(instance), + FnVal::Instance(instance) => { + let salt = M::get_global_alloc_salt(self, Some(instance)); + self.tcx.reserve_and_set_fn_alloc(instance, salt) + } FnVal::Other(extra) => { // FIXME(RalfJung): Should we have a cache here? let id = self.tcx.reserve_alloc_id(); diff --git a/compiler/rustc_const_eval/src/interpret/place.rs b/compiler/rustc_const_eval/src/interpret/place.rs index 470a62026b9..2afdd02c880 100644 --- a/compiler/rustc_const_eval/src/interpret/place.rs +++ b/compiler/rustc_const_eval/src/interpret/place.rs @@ -1008,7 +1008,8 @@ where // Use cache for immutable strings. let ptr = if mutbl.is_not() { // Use dedup'd allocation function. - let id = tcx.allocate_bytes_dedup(str.as_bytes()); + let salt = M::get_global_alloc_salt(self, None); + let id = tcx.allocate_bytes_dedup(str.as_bytes(), salt); // Turn untagged "global" pointers (obtained via `tcx`) into the machine pointer to the allocation. M::adjust_alloc_root_pointer(&self, Pointer::from(id), Some(kind))? diff --git a/compiler/rustc_const_eval/src/interpret/traits.rs b/compiler/rustc_const_eval/src/interpret/traits.rs index fb50661b826..cd4faf06655 100644 --- a/compiler/rustc_const_eval/src/interpret/traits.rs +++ b/compiler/rustc_const_eval/src/interpret/traits.rs @@ -28,7 +28,9 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> { ensure_monomorphic_enough(*self.tcx, ty)?; ensure_monomorphic_enough(*self.tcx, poly_trait_ref)?; - let vtable_symbolic_allocation = self.tcx.reserve_and_set_vtable_alloc(ty, poly_trait_ref); + let salt = M::get_global_alloc_salt(self, None); + let vtable_symbolic_allocation = + self.tcx.reserve_and_set_vtable_alloc(ty, poly_trait_ref, salt); let vtable_ptr = self.global_root_pointer(Pointer::from(vtable_symbolic_allocation))?; Ok(vtable_ptr.into()) } diff --git a/compiler/rustc_middle/src/mir/interpret/mod.rs b/compiler/rustc_middle/src/mir/interpret/mod.rs index 1851a61d753..91e71c12cae 100644 --- a/compiler/rustc_middle/src/mir/interpret/mod.rs +++ b/compiler/rustc_middle/src/mir/interpret/mod.rs @@ -13,7 +13,6 @@ use std::num::NonZero; use std::{fmt, io}; use rustc_ast::LitKind; -use rustc_attr::InlineAttr; use rustc_data_structures::fx::FxHashMap; use rustc_data_structures::sync::Lock; use rustc_errors::ErrorGuaranteed; @@ -46,7 +45,7 @@ pub use self::pointer::{CtfeProvenance, Pointer, PointerArithmetic, Provenance}; pub use self::value::Scalar; use crate::mir; use crate::ty::codec::{TyDecoder, TyEncoder}; -use crate::ty::{self, GenericArgKind, Instance, Ty, TyCtxt}; +use crate::ty::{self, Instance, Ty, TyCtxt}; /// Uniquely identifies one of the following: /// - A constant @@ -126,11 +125,10 @@ pub fn specialized_encode_alloc_id<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>>( AllocDiscriminant::Alloc.encode(encoder); alloc.encode(encoder); } - GlobalAlloc::Function { instance, unique } => { + GlobalAlloc::Function { instance } => { trace!("encoding {:?} with {:#?}", alloc_id, instance); AllocDiscriminant::Fn.encode(encoder); instance.encode(encoder); - unique.encode(encoder); } GlobalAlloc::VTable(ty, poly_trait_ref) => { trace!("encoding {:?} with {ty:#?}, {poly_trait_ref:#?}", alloc_id); @@ -219,38 +217,32 @@ impl<'s> AllocDecodingSession<'s> { } // Now decode the actual data. - let alloc_id = decoder.with_position(pos, |decoder| { - match alloc_kind { - AllocDiscriminant::Alloc => { - trace!("creating memory alloc ID"); - let alloc = <ConstAllocation<'tcx> as Decodable<_>>::decode(decoder); - trace!("decoded alloc {:?}", alloc); - decoder.interner().reserve_and_set_memory_alloc(alloc) - } - AllocDiscriminant::Fn => { - trace!("creating fn alloc ID"); - let instance = ty::Instance::decode(decoder); - trace!("decoded fn alloc instance: {:?}", instance); - let unique = bool::decode(decoder); - // Here we cannot call `reserve_and_set_fn_alloc` as that would use a query, which - // is not possible in this context. That's why the allocation stores - // whether it is unique or not. - decoder.interner().reserve_and_set_fn_alloc_internal(instance, unique) - } - AllocDiscriminant::VTable => { - trace!("creating vtable alloc ID"); - let ty = <Ty<'_> as Decodable<D>>::decode(decoder); - let poly_trait_ref = - <Option<ty::PolyExistentialTraitRef<'_>> as Decodable<D>>::decode(decoder); - trace!("decoded vtable alloc instance: {ty:?}, {poly_trait_ref:?}"); - decoder.interner().reserve_and_set_vtable_alloc(ty, poly_trait_ref) - } - AllocDiscriminant::Static => { - trace!("creating extern static alloc ID"); - let did = <DefId as Decodable<D>>::decode(decoder); - trace!("decoded static def-ID: {:?}", did); - decoder.interner().reserve_and_set_static_alloc(did) - } + let alloc_id = decoder.with_position(pos, |decoder| match alloc_kind { + AllocDiscriminant::Alloc => { + trace!("creating memory alloc ID"); + let alloc = <ConstAllocation<'tcx> as Decodable<_>>::decode(decoder); + trace!("decoded alloc {:?}", alloc); + decoder.interner().reserve_and_set_memory_alloc(alloc) + } + AllocDiscriminant::Fn => { + trace!("creating fn alloc ID"); + let instance = ty::Instance::decode(decoder); + trace!("decoded fn alloc instance: {:?}", instance); + decoder.interner().reserve_and_set_fn_alloc(instance, CTFE_ALLOC_SALT) + } + AllocDiscriminant::VTable => { + trace!("creating vtable alloc ID"); + let ty = <Ty<'_> as Decodable<D>>::decode(decoder); + let poly_trait_ref = + <Option<ty::PolyExistentialTraitRef<'_>> as Decodable<D>>::decode(decoder); + trace!("decoded vtable alloc instance: {ty:?}, {poly_trait_ref:?}"); + decoder.interner().reserve_and_set_vtable_alloc(ty, poly_trait_ref, CTFE_ALLOC_SALT) + } + AllocDiscriminant::Static => { + trace!("creating extern static alloc ID"); + let did = <DefId as Decodable<D>>::decode(decoder); + trace!("decoded static def-ID: {:?}", did); + decoder.interner().reserve_and_set_static_alloc(did) } }); @@ -265,12 +257,7 @@ impl<'s> AllocDecodingSession<'s> { #[derive(Debug, Clone, Eq, PartialEq, Hash, TyDecodable, TyEncodable, HashStable)] pub enum GlobalAlloc<'tcx> { /// The alloc ID is used as a function pointer. - Function { - instance: Instance<'tcx>, - /// Stores whether this instance is unique, i.e. all pointers to this function use the same - /// alloc ID. - unique: bool, - }, + Function { instance: Instance<'tcx> }, /// This alloc ID points to a symbolic (not-reified) vtable. VTable(Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>), /// The alloc ID points to a "lazy" static variable that did not get computed (yet). @@ -323,14 +310,17 @@ impl<'tcx> GlobalAlloc<'tcx> { } } +pub const CTFE_ALLOC_SALT: usize = 0; + pub(crate) struct AllocMap<'tcx> { /// Maps `AllocId`s to their corresponding allocations. alloc_map: FxHashMap<AllocId, GlobalAlloc<'tcx>>, - /// Used to ensure that statics and functions only get one associated `AllocId`. - // - // FIXME: Should we just have two separate dedup maps for statics and functions each? - dedup: FxHashMap<GlobalAlloc<'tcx>, AllocId>, + /// Used to deduplicate global allocations: functions, vtables, string literals, ... + /// + /// The `usize` is a "salt" used by Miri to make deduplication imperfect, thus better emulating + /// the actual guarantees. + dedup: FxHashMap<(GlobalAlloc<'tcx>, usize), AllocId>, /// The `AllocId` to assign to the next requested ID. /// Always incremented; never gets smaller. @@ -368,74 +358,40 @@ impl<'tcx> TyCtxt<'tcx> { /// Reserves a new ID *if* this allocation has not been dedup-reserved before. /// Should not be used for mutable memory. - fn reserve_and_set_dedup(self, alloc: GlobalAlloc<'tcx>) -> AllocId { + fn reserve_and_set_dedup(self, alloc: GlobalAlloc<'tcx>, salt: usize) -> AllocId { let mut alloc_map = self.alloc_map.lock(); if let GlobalAlloc::Memory(mem) = alloc { if mem.inner().mutability.is_mut() { bug!("trying to dedup-reserve mutable memory"); } } - if let Some(&alloc_id) = alloc_map.dedup.get(&alloc) { + let alloc_salt = (alloc, salt); + if let Some(&alloc_id) = alloc_map.dedup.get(&alloc_salt) { return alloc_id; } let id = alloc_map.reserve(); - debug!("creating alloc {alloc:?} with id {id:?}"); - alloc_map.alloc_map.insert(id, alloc.clone()); - alloc_map.dedup.insert(alloc, id); + debug!("creating alloc {:?} with id {id:?}", alloc_salt.0); + alloc_map.alloc_map.insert(id, alloc_salt.0.clone()); + alloc_map.dedup.insert(alloc_salt, id); id } /// Generates an `AllocId` for a memory allocation. If the exact same memory has been /// allocated before, this will return the same `AllocId`. - pub fn reserve_and_set_memory_dedup(self, mem: ConstAllocation<'tcx>) -> AllocId { - self.reserve_and_set_dedup(GlobalAlloc::Memory(mem)) + pub fn reserve_and_set_memory_dedup(self, mem: ConstAllocation<'tcx>, salt: usize) -> AllocId { + self.reserve_and_set_dedup(GlobalAlloc::Memory(mem), salt) } /// Generates an `AllocId` for a static or return a cached one in case this function has been /// called on the same static before. pub fn reserve_and_set_static_alloc(self, static_id: DefId) -> AllocId { - self.reserve_and_set_dedup(GlobalAlloc::Static(static_id)) - } - - /// Generates an `AllocId` for a function. The caller must already have decided whether this - /// function obtains a unique AllocId or gets de-duplicated via the cache. - fn reserve_and_set_fn_alloc_internal(self, instance: Instance<'tcx>, unique: bool) -> AllocId { - let alloc = GlobalAlloc::Function { instance, unique }; - if unique { - // Deduplicate. - self.reserve_and_set_dedup(alloc) - } else { - // Get a fresh ID. - let mut alloc_map = self.alloc_map.lock(); - let id = alloc_map.reserve(); - alloc_map.alloc_map.insert(id, alloc); - id - } + let salt = 0; // Statics have a guaranteed unique address, no salt added. + self.reserve_and_set_dedup(GlobalAlloc::Static(static_id), salt) } - /// Generates an `AllocId` for a function. Depending on the function type, - /// this might get deduplicated or assigned a new ID each time. - pub fn reserve_and_set_fn_alloc(self, instance: Instance<'tcx>) -> AllocId { - // Functions cannot be identified by pointers, as asm-equal functions can get deduplicated - // by the linker (we set the "unnamed_addr" attribute for LLVM) and functions can be - // duplicated across crates. We thus generate a new `AllocId` for every mention of a - // function. This means that `main as fn() == main as fn()` is false, while `let x = main as - // fn(); x == x` is true. However, as a quality-of-life feature it can be useful to identify - // certain functions uniquely, e.g. for backtraces. So we identify whether codegen will - // actually emit duplicate functions. It does that when they have non-lifetime generics, or - // when they can be inlined. All other functions are given a unique address. - // This is not a stable guarantee! The `inline` attribute is a hint and cannot be relied - // upon for anything. But if we don't do this, backtraces look terrible. - let is_generic = instance - .args - .into_iter() - .any(|kind| !matches!(kind.unpack(), GenericArgKind::Lifetime(_))); - let can_be_inlined = match self.codegen_fn_attrs(instance.def_id()).inline { - InlineAttr::Never => false, - _ => true, - }; - let unique = !is_generic && !can_be_inlined; - self.reserve_and_set_fn_alloc_internal(instance, unique) + /// Generates an `AllocId` for a function. Will get deduplicated. + pub fn reserve_and_set_fn_alloc(self, instance: Instance<'tcx>, salt: usize) -> AllocId { + self.reserve_and_set_dedup(GlobalAlloc::Function { instance }, salt) } /// Generates an `AllocId` for a (symbolic, not-reified) vtable. Will get deduplicated. @@ -443,8 +399,9 @@ impl<'tcx> TyCtxt<'tcx> { self, ty: Ty<'tcx>, poly_trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>, + salt: usize, ) -> AllocId { - self.reserve_and_set_dedup(GlobalAlloc::VTable(ty, poly_trait_ref)) + self.reserve_and_set_dedup(GlobalAlloc::VTable(ty, poly_trait_ref), salt) } /// Interns the `Allocation` and return a new `AllocId`, even if there's already an identical diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs index 8f8fd09c9e4..07fed7b17ad 100644 --- a/compiler/rustc_middle/src/ty/context.rs +++ b/compiler/rustc_middle/src/ty/context.rs @@ -1438,11 +1438,11 @@ impl<'tcx> TyCtxt<'tcx> { /// Allocates a read-only byte or string literal for `mir::interpret`. /// Returns the same `AllocId` if called again with the same bytes. - pub fn allocate_bytes_dedup(self, bytes: &[u8]) -> interpret::AllocId { + pub fn allocate_bytes_dedup(self, bytes: &[u8], salt: usize) -> interpret::AllocId { // Create an allocation that just contains these bytes. let alloc = interpret::Allocation::from_bytes_byte_aligned_immutable(bytes); let alloc = self.mk_const_alloc(alloc); - self.reserve_and_set_memory_dedup(alloc) + self.reserve_and_set_memory_dedup(alloc, salt) } /// Returns a range of the start/end indices specified with the diff --git a/compiler/rustc_middle/src/ty/vtable.rs b/compiler/rustc_middle/src/ty/vtable.rs index f38f27b84f0..951112dfe85 100644 --- a/compiler/rustc_middle/src/ty/vtable.rs +++ b/compiler/rustc_middle/src/ty/vtable.rs @@ -3,7 +3,7 @@ use std::fmt; use rustc_ast::Mutability; use rustc_macros::HashStable; -use crate::mir::interpret::{alloc_range, AllocId, Allocation, Pointer, Scalar}; +use crate::mir::interpret::{alloc_range, AllocId, Allocation, Pointer, Scalar, CTFE_ALLOC_SALT}; use crate::ty::{self, Instance, PolyTraitRef, Ty, TyCtxt}; #[derive(Clone, Copy, PartialEq, HashStable)] @@ -73,6 +73,11 @@ pub(crate) fn vtable_min_entries<'tcx>( /// Retrieves an allocation that represents the contents of a vtable. /// Since this is a query, allocations are cached and not duplicated. +/// +/// This is an "internal" `AllocId` that should never be used as a value in the interpreted program. +/// The interpreter should use `AllocId` that refer to a `GlobalAlloc::VTable` instead. +/// (This is similar to statics, which also have a similar "internal" `AllocId` storing their +/// initial contents.) pub(super) fn vtable_allocation_provider<'tcx>( tcx: TyCtxt<'tcx>, key: (Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>), @@ -114,7 +119,7 @@ pub(super) fn vtable_allocation_provider<'tcx>( VtblEntry::MetadataDropInPlace => { if ty.needs_drop(tcx, ty::ParamEnv::reveal_all()) { let instance = ty::Instance::resolve_drop_in_place(tcx, ty); - let fn_alloc_id = tcx.reserve_and_set_fn_alloc(instance); + let fn_alloc_id = tcx.reserve_and_set_fn_alloc(instance, CTFE_ALLOC_SALT); let fn_ptr = Pointer::from(fn_alloc_id); Scalar::from_pointer(fn_ptr, &tcx) } else { @@ -127,7 +132,7 @@ pub(super) fn vtable_allocation_provider<'tcx>( VtblEntry::Method(instance) => { // Prepare the fn ptr we write into the vtable. let instance = instance.polymorphize(tcx); - let fn_alloc_id = tcx.reserve_and_set_fn_alloc(instance); + let fn_alloc_id = tcx.reserve_and_set_fn_alloc(instance, CTFE_ALLOC_SALT); let fn_ptr = Pointer::from(fn_alloc_id); Scalar::from_pointer(fn_ptr, &tcx) } diff --git a/compiler/rustc_mir_build/src/build/expr/as_constant.rs b/compiler/rustc_mir_build/src/build/expr/as_constant.rs index 10cf545f1b7..4430aab73a8 100644 --- a/compiler/rustc_mir_build/src/build/expr/as_constant.rs +++ b/compiler/rustc_mir_build/src/build/expr/as_constant.rs @@ -2,7 +2,9 @@ use rustc_ast as ast; use rustc_hir::LangItem; -use rustc_middle::mir::interpret::{Allocation, LitToConstError, LitToConstInput, Scalar}; +use rustc_middle::mir::interpret::{ + Allocation, LitToConstError, LitToConstInput, Scalar, CTFE_ALLOC_SALT, +}; use rustc_middle::mir::*; use rustc_middle::thir::*; use rustc_middle::ty::{ @@ -140,7 +142,7 @@ fn lit_to_mir_constant<'tcx>( ConstValue::Slice { data: allocation, meta: allocation.inner().size().bytes() } } (ast::LitKind::ByteStr(data, _), ty::Ref(_, inner_ty, _)) if inner_ty.is_array() => { - let id = tcx.allocate_bytes_dedup(data); + let id = tcx.allocate_bytes_dedup(data, CTFE_ALLOC_SALT); ConstValue::Scalar(Scalar::from_pointer(id.into(), &tcx)) } (ast::LitKind::CStr(data, _), ty::Ref(_, inner_ty, _)) if matches!(inner_ty.kind(), ty::Adt(def, _) if tcx.is_lang_item(def.did(), LangItem::CStr)) => diff --git a/src/tools/miri/src/lib.rs b/src/tools/miri/src/lib.rs index 2b3ae6df5de..966d38508f6 100644 --- a/src/tools/miri/src/lib.rs +++ b/src/tools/miri/src/lib.rs @@ -56,6 +56,7 @@ extern crate either; extern crate tracing; // The rustc crates we need +extern crate rustc_attr; extern crate rustc_apfloat; extern crate rustc_ast; extern crate rustc_const_eval; diff --git a/src/tools/miri/src/machine.rs b/src/tools/miri/src/machine.rs index 3e45a3a7e1a..df4154bcb58 100644 --- a/src/tools/miri/src/machine.rs +++ b/src/tools/miri/src/machine.rs @@ -11,6 +11,7 @@ use rand::rngs::StdRng; use rand::Rng; use rand::SeedableRng; +use rustc_attr::InlineAttr; use rustc_data_structures::fx::{FxHashMap, FxHashSet}; #[allow(unused)] use rustc_data_structures::static_assert_size; @@ -47,10 +48,10 @@ pub const SIGRTMIN: i32 = 34; /// `SIGRTMAX` - `SIGRTMIN` >= 8 (which is the value of `_POSIX_RTSIG_MAX`) pub const SIGRTMAX: i32 = 42; -/// Each const has multiple addresses, but only this many. Since const allocations are never -/// deallocated, choosing a new [`AllocId`] and thus base address for each evaluation would -/// produce unbounded memory usage. -const ADDRS_PER_CONST: usize = 16; +/// Each anonymous global (constant, vtable, function pointer, ...) has multiple addresses, but only +/// this many. Since const allocations are never deallocated, choosing a new [`AllocId`] and thus +/// base address for each evaluation would produce unbounded memory usage. +const ADDRS_PER_ANON_GLOBAL: usize = 32; /// Extra data stored with each stack frame pub struct FrameExtra<'tcx> { @@ -1372,7 +1373,7 @@ impl<'tcx> Machine<'tcx> for MiriMachine<'tcx> { catch_unwind: None, timing, is_user_relevant: ecx.machine.is_user_relevant(&frame), - salt: ecx.machine.rng.borrow_mut().gen::<usize>() % ADDRS_PER_CONST, + salt: ecx.machine.rng.borrow_mut().gen::<usize>() % ADDRS_PER_ANON_GLOBAL, }; Ok(frame.with_extra(extra)) @@ -1518,4 +1519,40 @@ impl<'tcx> Machine<'tcx> for MiriMachine<'tcx> { Entry::Occupied(oe) => Ok(oe.get().clone()), } } + + fn get_global_alloc_salt( + ecx: &InterpCx<'tcx, Self>, + instance: Option<ty::Instance<'tcx>>, + ) -> usize { + let unique = if let Some(instance) = instance { + // Functions cannot be identified by pointers, as asm-equal functions can get deduplicated + // by the linker (we set the "unnamed_addr" attribute for LLVM) and functions can be + // duplicated across crates. We thus generate a new `AllocId` for every mention of a + // function. This means that `main as fn() == main as fn()` is false, while `let x = main as + // fn(); x == x` is true. However, as a quality-of-life feature it can be useful to identify + // certain functions uniquely, e.g. for backtraces. So we identify whether codegen will + // actually emit duplicate functions. It does that when they have non-lifetime generics, or + // when they can be inlined. All other functions are given a unique address. + // This is not a stable guarantee! The `inline` attribute is a hint and cannot be relied + // upon for anything. But if we don't do this, backtraces look terrible. + let is_generic = instance + .args + .into_iter() + .any(|kind| !matches!(kind.unpack(), ty::GenericArgKind::Lifetime(_))); + let can_be_inlined = match ecx.tcx.codegen_fn_attrs(instance.def_id()).inline { + InlineAttr::Never => false, + _ => true, + }; + !is_generic && !can_be_inlined + } else { + // Non-functions are never unique. + false + }; + // Always use the same salt if the allocation is unique. + if unique { + CTFE_ALLOC_SALT + } else { + ecx.machine.rng.borrow_mut().gen::<usize>() % ADDRS_PER_ANON_GLOBAL + } + } } diff --git a/src/tools/miri/tests/pass/dyn-traits.rs b/src/tools/miri/tests/pass/dyn-traits.rs index 908d521a0d8..f6220120968 100644 --- a/src/tools/miri/tests/pass/dyn-traits.rs +++ b/src/tools/miri/tests/pass/dyn-traits.rs @@ -141,7 +141,17 @@ fn unsized_dyn_autoderef() { } */ +fn vtable_ptr_eq() { + use std::{fmt, ptr}; + + // We don't always get the same vtable when casting this to a wide pointer. + let x = &2; + let x_wide = x as &dyn fmt::Display; + assert!((0..256).any(|_| !ptr::eq(x as &dyn fmt::Display, x_wide))); +} + fn main() { ref_box_dyn(); box_box_trait(); + vtable_ptr_eq(); } diff --git a/src/tools/miri/tests/pass/function_pointers.rs b/src/tools/miri/tests/pass/function_pointers.rs index 2aa3ebf2dd0..a5c4bc5e0d9 100644 --- a/src/tools/miri/tests/pass/function_pointers.rs +++ b/src/tools/miri/tests/pass/function_pointers.rs @@ -82,7 +82,8 @@ fn main() { assert!(return_fn_ptr(i) == i); assert!(return_fn_ptr(i) as unsafe fn() -> i32 == i as fn() -> i32 as unsafe fn() -> i32); // Miri gives different addresses to different reifications of a generic function. - assert!(return_fn_ptr(f) != f); + // at least if we try often enough. + assert!((0..256).any(|_| return_fn_ptr(f) != f)); // However, if we only turn `f` into a function pointer and use that pointer, // it is equal to itself. let f2 = f as fn() -> i32; diff --git a/src/tools/miri/tests/pass/rc.rs b/src/tools/miri/tests/pass/rc.rs index 6dd1b3aff9e..b1470dabc26 100644 --- a/src/tools/miri/tests/pass/rc.rs +++ b/src/tools/miri/tests/pass/rc.rs @@ -75,7 +75,8 @@ fn rc_fat_ptr_eq() { let p = Rc::new(1) as Rc<dyn Debug>; let a: *const dyn Debug = &*p; let r = Rc::into_raw(p); - assert!(a == r); + // Only compare the pointer parts, as the vtable might differ. + assert!(a as *const () == r as *const ()); drop(unsafe { Rc::from_raw(r) }); } |