257 lines
10 KiB
Rust
257 lines
10 KiB
Rust
//! Implement thread-local storage.
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use std::collections::BTreeMap;
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use std::collections::btree_map::Entry;
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use log::trace;
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use rustc_middle::ty;
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use rustc_target::abi::{Size, HasDataLayout};
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use crate::{HelpersEvalContextExt, ThreadsEvalContextExt, InterpResult, MPlaceTy, Scalar, StackPopCleanup, Tag};
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use crate::machine::{ThreadId, ThreadState};
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pub type TlsKey = u128;
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#[derive(Clone, Debug)]
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pub struct TlsEntry<'tcx> {
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/// The data for this key. None is used to represent NULL.
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/// (We normalize this early to avoid having to do a NULL-ptr-test each time we access the data.)
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/// Will eventually become a map from thread IDs to `Scalar`s, if we ever support more than one thread.
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data: BTreeMap<ThreadId, Scalar<Tag>>,
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dtor: Option<ty::Instance<'tcx>>,
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}
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#[derive(Debug)]
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pub struct TlsData<'tcx> {
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/// The Key to use for the next thread-local allocation.
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next_key: TlsKey,
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/// pthreads-style thread-local storage.
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keys: BTreeMap<TlsKey, TlsEntry<'tcx>>,
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/// A single global dtor (that's how things work on macOS) with a data argument.
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global_dtor: Option<(ty::Instance<'tcx>, Scalar<Tag>)>,
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/// Whether we are in the "destruct" phase, during which some operations are UB.
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dtors_running: bool,
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}
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impl<'tcx> Default for TlsData<'tcx> {
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fn default() -> Self {
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TlsData {
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next_key: 1, // start with 1 as we must not use 0 on Windows
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keys: Default::default(),
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global_dtor: None,
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dtors_running: false,
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}
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}
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}
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impl<'tcx> TlsData<'tcx> {
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/// Generate a new TLS key with the given destructor.
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/// `max_size` determines the integer size the key has to fit in.
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pub fn create_tls_key(&mut self, dtor: Option<ty::Instance<'tcx>>, max_size: Size) -> InterpResult<'tcx, TlsKey> {
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let new_key = self.next_key;
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self.next_key += 1;
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self.keys.insert(new_key, TlsEntry { data: Default::default(), dtor }).unwrap_none();
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trace!("New TLS key allocated: {} with dtor {:?}", new_key, dtor);
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if max_size.bits() < 128 && new_key >= (1u128 << max_size.bits() as u128) {
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throw_unsup_format!("we ran out of TLS key space");
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}
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Ok(new_key)
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}
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pub fn delete_tls_key(&mut self, key: TlsKey) -> InterpResult<'tcx> {
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match self.keys.remove(&key) {
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Some(_) => {
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trace!("TLS key {} removed", key);
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Ok(())
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}
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None => throw_ub_format!("removing a non-existig TLS key: {}", key),
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}
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}
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pub fn load_tls(
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&self,
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key: TlsKey,
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thread_id: ThreadId,
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cx: &impl HasDataLayout,
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) -> InterpResult<'tcx, Scalar<Tag>> {
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match self.keys.get(&key) {
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Some(TlsEntry { data, .. }) => {
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let value = data.get(&thread_id).cloned();
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trace!("TLS key {} for thread {:?} loaded: {:?}", key, thread_id, value);
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Ok(value.unwrap_or_else(|| Scalar::null_ptr(cx).into()))
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}
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None => throw_ub_format!("loading from a non-existing TLS key: {}", key),
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}
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}
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pub fn store_tls(
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&mut self,
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key: TlsKey, thread_id: ThreadId, new_data: Option<Scalar<Tag>>) -> InterpResult<'tcx> {
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match self.keys.get_mut(&key) {
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Some(TlsEntry { data, .. }) => {
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match new_data {
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Some(ptr) => {
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trace!("TLS key {} for thread {:?} stored: {:?}", key, thread_id, ptr);
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data.insert(thread_id, ptr);
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}
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None => {
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trace!("TLS key {} for thread {:?} removed", key, thread_id);
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data.remove(&thread_id);
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}
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}
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Ok(())
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}
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None => throw_ub_format!("storing to a non-existing TLS key: {}", key),
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}
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}
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pub fn set_global_dtor(&mut self, dtor: ty::Instance<'tcx>, data: Scalar<Tag>) -> InterpResult<'tcx> {
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if self.dtors_running {
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// UB, according to libstd docs.
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throw_ub_format!("setting global destructor while destructors are already running");
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}
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if self.global_dtor.is_some() {
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throw_unsup_format!("setting more than one global destructor is not supported");
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}
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self.global_dtor = Some((dtor, data));
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Ok(())
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}
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/// Returns a dtor, its argument and its index, if one is supposed to run.
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/// `key` is the last dtors that was run; we return the *next* one after that.
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///
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/// An optional destructor function may be associated with each key value.
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/// At thread exit, if a key value has a non-NULL destructor pointer,
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/// and the thread has a non-NULL value associated with that key,
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/// the value of the key is set to NULL, and then the function pointed
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/// to is called with the previously associated value as its sole argument.
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/// The order of destructor calls is unspecified if more than one destructor
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/// exists for a thread when it exits.
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///
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/// If, after all the destructors have been called for all non-NULL values
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/// with associated destructors, there are still some non-NULL values with
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/// associated destructors, then the process is repeated.
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/// If, after at least {PTHREAD_DESTRUCTOR_ITERATIONS} iterations of destructor
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/// calls for outstanding non-NULL values, there are still some non-NULL values
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/// with associated destructors, implementations may stop calling destructors,
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/// or they may continue calling destructors until no non-NULL values with
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/// associated destructors exist, even though this might result in an infinite loop.
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fn fetch_tls_dtor(
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&mut self,
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key: Option<TlsKey>,
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thread_id: ThreadId,
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) -> Option<(ty::Instance<'tcx>, ThreadId, Scalar<Tag>, TlsKey)> {
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use std::collections::Bound::*;
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let thread_local = &mut self.keys;
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let start = match key {
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Some(key) => Excluded(key),
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None => Unbounded,
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};
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for (&key, TlsEntry { data, dtor }) in
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thread_local.range_mut((start, Unbounded))
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{
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match data.entry(thread_id) {
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Entry::Occupied(entry) => {
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let (thread_id, data_scalar) = entry.remove_entry();
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if let Some(dtor) = dtor {
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let ret = Some((*dtor, thread_id, data_scalar, key));
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return ret;
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}
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}
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Entry::Vacant(_) => {}
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}
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}
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None
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}
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}
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impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
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pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
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/// Run TLS destructors for all threads.
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fn run_tls_dtors(&mut self) -> InterpResult<'tcx> {
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let this = self.eval_context_mut();
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assert!(!this.machine.tls.dtors_running, "running TLS dtors twice");
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this.machine.tls.dtors_running = true;
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if this.tcx.sess.target.target.target_os == "windows" {
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// Windows has a special magic linker section that is run on certain events.
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// Instead of searching for that section and supporting arbitrary hooks in there
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// (that would be basically https://github.com/rust-lang/miri/issues/450),
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// we specifically look up the static in libstd that we know is placed
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// in that section.
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let thread_callback = this.eval_path_scalar(&["std", "sys", "windows", "thread_local", "p_thread_callback"])?;
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let thread_callback = this.memory.get_fn(thread_callback.not_undef()?)?.as_instance()?;
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// The signature of this function is `unsafe extern "system" fn(h: c::LPVOID, dwReason: c::DWORD, pv: c::LPVOID)`.
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let reason = this.eval_path_scalar(&["std", "sys", "windows", "c", "DLL_PROCESS_DETACH"])?;
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let ret_place = MPlaceTy::dangling(this.machine.layouts.unit, this).into();
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this.call_function(
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thread_callback,
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&[Scalar::null_ptr(this).into(), reason.into(), Scalar::null_ptr(this).into()],
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Some(ret_place),
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StackPopCleanup::None { cleanup: true },
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)?;
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// step until out of stackframes
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this.run()?;
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// Windows doesn't have other destructors.
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return Ok(());
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}
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// The macOS global dtor runs "before any TLS slots get freed", so do that first.
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if let Some((instance, data)) = this.machine.tls.global_dtor {
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trace!("Running global dtor {:?} on {:?}", instance, data);
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let ret_place = MPlaceTy::dangling(this.machine.layouts.unit, this).into();
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this.call_function(
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instance,
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&[data.into()],
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Some(ret_place),
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StackPopCleanup::None { cleanup: true },
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)?;
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// step until out of stackframes
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this.run()?;
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}
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// Now run the "keyed" destructors.
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for (thread_id, thread_state) in this.get_all_thread_ids_with_states() {
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assert!(thread_state == ThreadState::Terminated,
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"TLS destructors should be executed after all threads terminated.");
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this.set_active_thread(thread_id)?;
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let mut dtor = this.machine.tls.fetch_tls_dtor(None, thread_id);
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while let Some((instance, thread_id, ptr, key)) = dtor {
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trace!("Running TLS dtor {:?} on {:?} at {:?}", instance, ptr, thread_id);
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assert!(!this.is_null(ptr).unwrap(), "Data can't be NULL when dtor is called!");
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let ret_place = MPlaceTy::dangling(this.layout_of(this.tcx.mk_unit())?, this).into();
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this.call_function(
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instance,
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&[ptr.into()],
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Some(ret_place),
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StackPopCleanup::None { cleanup: true },
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)?;
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// step until out of stackframes
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this.run()?;
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// Fetch next dtor after `key`.
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dtor = match this.machine.tls.fetch_tls_dtor(Some(key), thread_id) {
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dtor @ Some(_) => dtor,
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// We ran each dtor once, start over from the beginning.
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None => this.machine.tls.fetch_tls_dtor(None, thread_id),
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};
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}
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}
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Ok(())
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}
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}
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