| //! Implement thread-local storage. |
| |
| use std::collections::btree_map::Entry as BTreeEntry; |
| use std::collections::BTreeMap; |
| use std::task::Poll; |
| |
| use log::trace; |
| |
| use rustc_middle::ty; |
| use rustc_target::abi::{HasDataLayout, Size}; |
| use rustc_target::spec::abi::Abi; |
| |
| use crate::*; |
| |
| pub type TlsKey = u128; |
| |
| #[derive(Clone, Debug)] |
| pub struct TlsEntry<'tcx> { |
| /// The data for this key. None is used to represent NULL. |
| /// (We normalize this early to avoid having to do a NULL-ptr-test each time we access the data.) |
| data: BTreeMap<ThreadId, Scalar<Provenance>>, |
| dtor: Option<ty::Instance<'tcx>>, |
| } |
| |
| #[derive(Default, Debug)] |
| struct RunningDtorState { |
| /// The last TlsKey used to retrieve a TLS destructor. `None` means that we |
| /// have not tried to retrieve a TLS destructor yet or that we already tried |
| /// all keys. |
| last_key: Option<TlsKey>, |
| } |
| |
| #[derive(Debug)] |
| pub struct TlsData<'tcx> { |
| /// The Key to use for the next thread-local allocation. |
| next_key: TlsKey, |
| |
| /// pthreads-style thread-local storage. |
| keys: BTreeMap<TlsKey, TlsEntry<'tcx>>, |
| |
| /// A single per thread destructor of the thread local storage (that's how |
| /// things work on macOS) with a data argument. |
| macos_thread_dtors: BTreeMap<ThreadId, (ty::Instance<'tcx>, Scalar<Provenance>)>, |
| } |
| |
| impl<'tcx> Default for TlsData<'tcx> { |
| fn default() -> Self { |
| TlsData { |
| next_key: 1, // start with 1 as we must not use 0 on Windows |
| keys: Default::default(), |
| macos_thread_dtors: Default::default(), |
| } |
| } |
| } |
| |
| impl<'tcx> TlsData<'tcx> { |
| /// Generate a new TLS key with the given destructor. |
| /// `max_size` determines the integer size the key has to fit in. |
| #[allow(clippy::integer_arithmetic)] |
| pub fn create_tls_key( |
| &mut self, |
| dtor: Option<ty::Instance<'tcx>>, |
| max_size: Size, |
| ) -> InterpResult<'tcx, TlsKey> { |
| let new_key = self.next_key; |
| self.next_key += 1; |
| self.keys.try_insert(new_key, TlsEntry { data: Default::default(), dtor }).unwrap(); |
| trace!("New TLS key allocated: {} with dtor {:?}", new_key, dtor); |
| |
| if max_size.bits() < 128 && new_key >= (1u128 << max_size.bits()) { |
| throw_unsup_format!("we ran out of TLS key space"); |
| } |
| Ok(new_key) |
| } |
| |
| pub fn delete_tls_key(&mut self, key: TlsKey) -> InterpResult<'tcx> { |
| match self.keys.remove(&key) { |
| Some(_) => { |
| trace!("TLS key {} removed", key); |
| Ok(()) |
| } |
| None => throw_ub_format!("removing a nonexistent TLS key: {}", key), |
| } |
| } |
| |
| pub fn load_tls( |
| &self, |
| key: TlsKey, |
| thread_id: ThreadId, |
| cx: &impl HasDataLayout, |
| ) -> InterpResult<'tcx, Scalar<Provenance>> { |
| match self.keys.get(&key) { |
| Some(TlsEntry { data, .. }) => { |
| let value = data.get(&thread_id).copied(); |
| trace!("TLS key {} for thread {:?} loaded: {:?}", key, thread_id, value); |
| Ok(value.unwrap_or_else(|| Scalar::null_ptr(cx))) |
| } |
| None => throw_ub_format!("loading from a non-existing TLS key: {}", key), |
| } |
| } |
| |
| pub fn store_tls( |
| &mut self, |
| key: TlsKey, |
| thread_id: ThreadId, |
| new_data: Scalar<Provenance>, |
| cx: &impl HasDataLayout, |
| ) -> InterpResult<'tcx> { |
| match self.keys.get_mut(&key) { |
| Some(TlsEntry { data, .. }) => { |
| if new_data.to_target_usize(cx)? != 0 { |
| trace!("TLS key {} for thread {:?} stored: {:?}", key, thread_id, new_data); |
| data.insert(thread_id, new_data); |
| } else { |
| trace!("TLS key {} for thread {:?} removed", key, thread_id); |
| data.remove(&thread_id); |
| } |
| Ok(()) |
| } |
| None => throw_ub_format!("storing to a non-existing TLS key: {}", key), |
| } |
| } |
| |
| /// Set the thread wide destructor of the thread local storage for the given |
| /// thread. This function is used to implement `_tlv_atexit` shim on MacOS. |
| /// |
| /// Thread wide dtors are available only on MacOS. There is one destructor |
| /// per thread as can be guessed from the following comment in the |
| /// [`_tlv_atexit` |
| /// implementation](https://github.com/opensource-apple/dyld/blob/195030646877261f0c8c7ad8b001f52d6a26f514/src/threadLocalVariables.c#L389): |
| /// |
| /// NOTE: this does not need locks because it only operates on current thread data |
| pub fn set_macos_thread_dtor( |
| &mut self, |
| thread: ThreadId, |
| dtor: ty::Instance<'tcx>, |
| data: Scalar<Provenance>, |
| ) -> InterpResult<'tcx> { |
| if self.macos_thread_dtors.insert(thread, (dtor, data)).is_some() { |
| throw_unsup_format!( |
| "setting more than one thread local storage destructor for the same thread is not supported" |
| ); |
| } |
| Ok(()) |
| } |
| |
| /// Returns a dtor, its argument and its index, if one is supposed to run. |
| /// `key` is the last dtors that was run; we return the *next* one after that. |
| /// |
| /// An optional destructor function may be associated with each key value. |
| /// At thread exit, if a key value has a non-NULL destructor pointer, |
| /// and the thread has a non-NULL value associated with that key, |
| /// the value of the key is set to NULL, and then the function pointed |
| /// to is called with the previously associated value as its sole argument. |
| /// **The order of destructor calls is unspecified if more than one destructor |
| /// exists for a thread when it exits.** |
| /// |
| /// If, after all the destructors have been called for all non-NULL values |
| /// with associated destructors, there are still some non-NULL values with |
| /// associated destructors, then the process is repeated. |
| /// If, after at least {PTHREAD_DESTRUCTOR_ITERATIONS} iterations of destructor |
| /// calls for outstanding non-NULL values, there are still some non-NULL values |
| /// with associated destructors, implementations may stop calling destructors, |
| /// or they may continue calling destructors until no non-NULL values with |
| /// associated destructors exist, even though this might result in an infinite loop. |
| fn fetch_tls_dtor( |
| &mut self, |
| key: Option<TlsKey>, |
| thread_id: ThreadId, |
| ) -> Option<(ty::Instance<'tcx>, Scalar<Provenance>, TlsKey)> { |
| use std::ops::Bound::*; |
| |
| let thread_local = &mut self.keys; |
| let start = match key { |
| Some(key) => Excluded(key), |
| None => Unbounded, |
| }; |
| // We interpret the documentation above (taken from POSIX) as saying that we need to iterate |
| // over all keys and run each destructor at least once before running any destructor a 2nd |
| // time. That's why we have `key` to indicate how far we got in the current iteration. If we |
| // return `None`, `schedule_next_pthread_tls_dtor` will re-try with `ket` set to `None` to |
| // start the next round. |
| // TODO: In the future, we might consider randomizing destructor order, but we still have to |
| // uphold this requirement. |
| for (&key, TlsEntry { data, dtor }) in thread_local.range_mut((start, Unbounded)) { |
| match data.entry(thread_id) { |
| BTreeEntry::Occupied(entry) => { |
| if let Some(dtor) = dtor { |
| // Set TLS data to NULL, and call dtor with old value. |
| let data_scalar = entry.remove(); |
| let ret = Some((*dtor, data_scalar, key)); |
| return ret; |
| } |
| } |
| BTreeEntry::Vacant(_) => {} |
| } |
| } |
| None |
| } |
| |
| /// Delete all TLS entries for the given thread. This function should be |
| /// called after all TLS destructors have already finished. |
| fn delete_all_thread_tls(&mut self, thread_id: ThreadId) { |
| for TlsEntry { data, .. } in self.keys.values_mut() { |
| data.remove(&thread_id); |
| } |
| } |
| } |
| |
| impl VisitTags for TlsData<'_> { |
| fn visit_tags(&self, visit: &mut dyn FnMut(BorTag)) { |
| let TlsData { keys, macos_thread_dtors, next_key: _ } = self; |
| |
| for scalar in keys.values().flat_map(|v| v.data.values()) { |
| scalar.visit_tags(visit); |
| } |
| for (_, scalar) in macos_thread_dtors.values() { |
| scalar.visit_tags(visit); |
| } |
| } |
| } |
| |
| #[derive(Debug, Default)] |
| pub struct TlsDtorsState(TlsDtorsStatePriv); |
| |
| #[derive(Debug, Default)] |
| enum TlsDtorsStatePriv { |
| #[default] |
| Init, |
| PthreadDtors(RunningDtorState), |
| Done, |
| } |
| |
| impl TlsDtorsState { |
| pub fn on_stack_empty<'tcx>( |
| &mut self, |
| this: &mut MiriInterpCx<'_, 'tcx>, |
| ) -> InterpResult<'tcx, Poll<()>> { |
| use TlsDtorsStatePriv::*; |
| match &mut self.0 { |
| Init => { |
| match this.tcx.sess.target.os.as_ref() { |
| "linux" | "freebsd" | "android" => { |
| // Run the pthread dtors. |
| self.0 = PthreadDtors(Default::default()); |
| } |
| "macos" => { |
| // The macOS thread wide destructor runs "before any TLS slots get |
| // freed", so do that first. |
| this.schedule_macos_tls_dtor()?; |
| // When the stack is empty again, go on with the pthread dtors. |
| self.0 = PthreadDtors(Default::default()); |
| } |
| "windows" => { |
| // Run the special magic hook. |
| this.schedule_windows_tls_dtors()?; |
| // And move to the final state. |
| self.0 = Done; |
| } |
| _ => { |
| // No TLS dtor support. |
| // FIXME: should we do something on wasi? |
| self.0 = Done; |
| } |
| } |
| } |
| PthreadDtors(state) => { |
| match this.schedule_next_pthread_tls_dtor(state)? { |
| Poll::Pending => {} // just keep going |
| Poll::Ready(()) => self.0 = Done, |
| } |
| } |
| Done => { |
| this.machine.tls.delete_all_thread_tls(this.get_active_thread()); |
| return Ok(Poll::Ready(())); |
| } |
| } |
| |
| Ok(Poll::Pending) |
| } |
| } |
| |
| impl<'mir, 'tcx: 'mir> EvalContextPrivExt<'mir, 'tcx> for crate::MiriInterpCx<'mir, 'tcx> {} |
| trait EvalContextPrivExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> { |
| /// Schedule TLS destructors for Windows. |
| /// On windows, TLS destructors are managed by std. |
| fn schedule_windows_tls_dtors(&mut self) -> InterpResult<'tcx> { |
| let this = self.eval_context_mut(); |
| |
| // Windows has a special magic linker section that is run on certain events. |
| // Instead of searching for that section and supporting arbitrary hooks in there |
| // (that would be basically https://github.com/rust-lang/miri/issues/450), |
| // we specifically look up the static in libstd that we know is placed |
| // in that section. |
| if !this.have_module(&["std"]) { |
| // Looks like we are running in a `no_std` crate. |
| // That also means no TLS dtors callback to call. |
| return Ok(()); |
| } |
| let thread_callback = |
| this.eval_windows("thread_local_key", "p_thread_callback").to_pointer(this)?; |
| let thread_callback = this.get_ptr_fn(thread_callback)?.as_instance()?; |
| |
| // FIXME: Technically, the reason should be `DLL_PROCESS_DETACH` when the main thread exits |
| // but std treats both the same. |
| let reason = this.eval_windows("c", "DLL_THREAD_DETACH"); |
| |
| // The signature of this function is `unsafe extern "system" fn(h: c::LPVOID, dwReason: c::DWORD, pv: c::LPVOID)`. |
| // FIXME: `h` should be a handle to the current module and what `pv` should be is unknown |
| // but both are ignored by std |
| this.call_function( |
| thread_callback, |
| Abi::System { unwind: false }, |
| &[Scalar::null_ptr(this).into(), reason.into(), Scalar::null_ptr(this).into()], |
| None, |
| StackPopCleanup::Root { cleanup: true }, |
| )?; |
| Ok(()) |
| } |
| |
| /// Schedule the MacOS thread destructor of the thread local storage to be |
| /// executed. |
| fn schedule_macos_tls_dtor(&mut self) -> InterpResult<'tcx> { |
| let this = self.eval_context_mut(); |
| let thread_id = this.get_active_thread(); |
| if let Some((instance, data)) = this.machine.tls.macos_thread_dtors.remove(&thread_id) { |
| trace!("Running macos dtor {:?} on {:?} at {:?}", instance, data, thread_id); |
| |
| this.call_function( |
| instance, |
| Abi::C { unwind: false }, |
| &[data.into()], |
| None, |
| StackPopCleanup::Root { cleanup: true }, |
| )?; |
| } |
| Ok(()) |
| } |
| |
| /// Schedule a pthread TLS destructor. Returns `true` if found |
| /// a destructor to schedule, and `false` otherwise. |
| fn schedule_next_pthread_tls_dtor( |
| &mut self, |
| state: &mut RunningDtorState, |
| ) -> InterpResult<'tcx, Poll<()>> { |
| let this = self.eval_context_mut(); |
| let active_thread = this.get_active_thread(); |
| |
| // Fetch next dtor after `key`. |
| let dtor = match this.machine.tls.fetch_tls_dtor(state.last_key, active_thread) { |
| dtor @ Some(_) => dtor, |
| // We ran each dtor once, start over from the beginning. |
| None => this.machine.tls.fetch_tls_dtor(None, active_thread), |
| }; |
| if let Some((instance, ptr, key)) = dtor { |
| state.last_key = Some(key); |
| trace!("Running TLS dtor {:?} on {:?} at {:?}", instance, ptr, active_thread); |
| assert!( |
| !ptr.to_target_usize(this).unwrap() != 0, |
| "data can't be NULL when dtor is called!" |
| ); |
| |
| this.call_function( |
| instance, |
| Abi::C { unwind: false }, |
| &[ptr.into()], |
| None, |
| StackPopCleanup::Root { cleanup: true }, |
| )?; |
| |
| return Ok(Poll::Pending); |
| } |
| |
| Ok(Poll::Ready(())) |
| } |
| } |
