1 //! Implement thread-local storage.
3 use std::collections::BTreeMap;
4 use std::collections::btree_map::Entry;
5 use std::collections::HashSet;
10 use rustc_target::abi::{Size, HasDataLayout};
13 HelpersEvalContextExt, InterpResult, MPlaceTy, Scalar, StackPopCleanup, Tag, ThreadId,
14 ThreadsEvalContextExt,
17 pub type TlsKey = u128;
19 #[derive(Clone, Debug)]
20 pub struct TlsEntry<'tcx> {
21 /// The data for this key. None is used to represent NULL.
22 /// (We normalize this early to avoid having to do a NULL-ptr-test each time we access the data.)
23 /// Will eventually become a map from thread IDs to `Scalar`s, if we ever support more than one thread.
24 data: BTreeMap<ThreadId, Scalar<Tag>>,
25 dtor: Option<ty::Instance<'tcx>>,
29 pub struct TlsData<'tcx> {
30 /// The Key to use for the next thread-local allocation.
33 /// pthreads-style thread-local storage.
34 keys: BTreeMap<TlsKey, TlsEntry<'tcx>>,
36 /// A single global per thread dtor (that's how things work on macOS) with a data argument.
37 global_dtors: BTreeMap<ThreadId, (ty::Instance<'tcx>, Scalar<Tag>)>,
39 /// Whether we are in the "destruct" phase, during which some operations are UB.
40 dtors_running: HashSet<ThreadId>,
43 impl<'tcx> Default for TlsData<'tcx> {
44 fn default() -> Self {
46 next_key: 1, // start with 1 as we must not use 0 on Windows
47 keys: Default::default(),
48 global_dtors: Default::default(),
49 dtors_running: Default::default(),
54 impl<'tcx> TlsData<'tcx> {
55 /// Generate a new TLS key with the given destructor.
56 /// `max_size` determines the integer size the key has to fit in.
57 pub fn create_tls_key(&mut self, dtor: Option<ty::Instance<'tcx>>, max_size: Size) -> InterpResult<'tcx, TlsKey> {
58 let new_key = self.next_key;
60 self.keys.insert(new_key, TlsEntry { data: Default::default(), dtor }).unwrap_none();
61 trace!("New TLS key allocated: {} with dtor {:?}", new_key, dtor);
63 if max_size.bits() < 128 && new_key >= (1u128 << max_size.bits() as u128) {
64 throw_unsup_format!("we ran out of TLS key space");
69 pub fn delete_tls_key(&mut self, key: TlsKey) -> InterpResult<'tcx> {
70 match self.keys.remove(&key) {
72 trace!("TLS key {} removed", key);
75 None => throw_ub_format!("removing a non-existig TLS key: {}", key),
83 cx: &impl HasDataLayout,
84 ) -> InterpResult<'tcx, Scalar<Tag>> {
85 match self.keys.get(&key) {
86 Some(TlsEntry { data, .. }) => {
87 let value = data.get(&thread_id).cloned();
88 trace!("TLS key {} for thread {:?} loaded: {:?}", key, thread_id, value);
89 Ok(value.unwrap_or_else(|| Scalar::null_ptr(cx).into()))
91 None => throw_ub_format!("loading from a non-existing TLS key: {}", key),
97 key: TlsKey, thread_id: ThreadId, new_data: Option<Scalar<Tag>>) -> InterpResult<'tcx> {
98 match self.keys.get_mut(&key) {
99 Some(TlsEntry { data, .. }) => {
102 trace!("TLS key {} for thread {:?} stored: {:?}", key, thread_id, ptr);
103 data.insert(thread_id, ptr);
106 trace!("TLS key {} for thread {:?} removed", key, thread_id);
107 data.remove(&thread_id);
112 None => throw_ub_format!("storing to a non-existing TLS key: {}", key),
116 /// Set global dtor for the given thread. This function is used to implement
117 /// `_tlv_atexit` shim on MacOS.
119 /// Global destructors are available only on MacOS and (potentially
120 /// confusingly) they seem to be still per thread as can be guessed from the
121 /// following comment in the [`_tlv_atexit`
122 /// implementation](https://github.com/opensource-apple/dyld/blob/195030646877261f0c8c7ad8b001f52d6a26f514/src/threadLocalVariables.c#L389):
124 /// // NOTE: this does not need locks because it only operates on current thread data
125 pub fn set_thread_global_dtor(
128 dtor: ty::Instance<'tcx>,
130 ) -> InterpResult<'tcx> {
131 if self.dtors_running.contains(&thread) {
132 // UB, according to libstd docs.
133 throw_ub_format!("setting global destructor while destructors are already running");
135 if self.global_dtors.insert(thread, (dtor, data)).is_some() {
136 throw_unsup_format!("setting more than one global destructor for the same thread is not supported");
141 /// Returns a dtor, its argument and its index, if one is supposed to run.
142 /// `key` is the last dtors that was run; we return the *next* one after that.
144 /// An optional destructor function may be associated with each key value.
145 /// At thread exit, if a key value has a non-NULL destructor pointer,
146 /// and the thread has a non-NULL value associated with that key,
147 /// the value of the key is set to NULL, and then the function pointed
148 /// to is called with the previously associated value as its sole argument.
149 /// The order of destructor calls is unspecified if more than one destructor
150 /// exists for a thread when it exits.
152 /// If, after all the destructors have been called for all non-NULL values
153 /// with associated destructors, there are still some non-NULL values with
154 /// associated destructors, then the process is repeated.
155 /// If, after at least {PTHREAD_DESTRUCTOR_ITERATIONS} iterations of destructor
156 /// calls for outstanding non-NULL values, there are still some non-NULL values
157 /// with associated destructors, implementations may stop calling destructors,
158 /// or they may continue calling destructors until no non-NULL values with
159 /// associated destructors exist, even though this might result in an infinite loop.
164 ) -> Option<(ty::Instance<'tcx>, Scalar<Tag>, TlsKey)> {
165 use std::collections::Bound::*;
167 let thread_local = &mut self.keys;
168 let start = match key {
169 Some(key) => Excluded(key),
172 for (&key, TlsEntry { data, dtor }) in
173 thread_local.range_mut((start, Unbounded))
175 match data.entry(thread_id) {
176 Entry::Occupied(entry) => {
177 let data_scalar = entry.remove();
178 if let Some(dtor) = dtor {
179 let ret = Some((*dtor, data_scalar, key));
183 Entry::Vacant(_) => {}
190 impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
191 pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
193 /// Run TLS destructors for the main thread on Windows. The implementation
194 /// assumes that we do not support concurrency on Windows yet.
196 /// Note: on non-Windows OS this function is a no-op.
197 fn run_windows_tls_dtors(&mut self) -> InterpResult<'tcx> {
198 let this = self.eval_context_mut();
199 if this.tcx.sess.target.target.target_os != "windows" {
202 let active_thread = this.get_active_thread()?;
203 assert_eq!(this.get_total_thread_count()?, 1, "concurrency on Windows not supported");
204 assert!(!this.machine.tls.dtors_running.contains(&active_thread), "running TLS dtors twice");
205 this.machine.tls.dtors_running.insert(active_thread);
206 // Windows has a special magic linker section that is run on certain events.
207 // Instead of searching for that section and supporting arbitrary hooks in there
208 // (that would be basically https://github.com/rust-lang/miri/issues/450),
209 // we specifically look up the static in libstd that we know is placed
211 let thread_callback = this.eval_path_scalar(&["std", "sys", "windows", "thread_local", "p_thread_callback"])?;
212 let thread_callback = this.memory.get_fn(thread_callback.not_undef()?)?.as_instance()?;
214 // The signature of this function is `unsafe extern "system" fn(h: c::LPVOID, dwReason: c::DWORD, pv: c::LPVOID)`.
215 let reason = this.eval_path_scalar(&["std", "sys", "windows", "c", "DLL_PROCESS_DETACH"])?;
216 let ret_place = MPlaceTy::dangling(this.machine.layouts.unit, this).into();
219 &[Scalar::null_ptr(this).into(), reason.into(), Scalar::null_ptr(this).into()],
221 StackPopCleanup::None { cleanup: true },
224 // step until out of stackframes
227 // Windows doesn't have other destructors.
231 /// Run TLS destructors for the active thread.
233 /// Note: on Windows OS this function is a no-op because we do not support
234 /// concurrency on Windows yet.
236 /// FIXME: we do not support yet deallocation of thread local statics.
237 fn run_tls_dtors_for_active_thread(&mut self) -> InterpResult<'tcx> {
238 let this = self.eval_context_mut();
239 if this.tcx.sess.target.target.target_os == "windows" {
242 let thread_id = this.get_active_thread()?;
243 assert!(!this.machine.tls.dtors_running.contains(&thread_id), "running TLS dtors twice");
244 this.machine.tls.dtors_running.insert(thread_id);
246 // The macOS global dtor runs "before any TLS slots get freed", so do that first.
247 if let Some(&(instance, data)) = this.machine.tls.global_dtors.get(&thread_id) {
248 trace!("Running global dtor {:?} on {:?} at {:?}", instance, data, thread_id);
250 let ret_place = MPlaceTy::dangling(this.machine.layouts.unit, this).into();
255 StackPopCleanup::None { cleanup: true },
258 // step until out of stackframes
262 assert!(this.has_terminated(thread_id)?, "running TLS dtors for non-terminated thread");
263 let mut dtor = this.machine.tls.fetch_tls_dtor(None, thread_id);
264 while let Some((instance, ptr, key)) = dtor {
265 trace!("Running TLS dtor {:?} on {:?} at {:?}", instance, ptr, thread_id);
266 assert!(!this.is_null(ptr).unwrap(), "Data can't be NULL when dtor is called!");
268 let ret_place = MPlaceTy::dangling(this.machine.layouts.unit, this).into();
273 StackPopCleanup::None { cleanup: true },
276 // step until out of stackframes
279 // Fetch next dtor after `key`.
280 dtor = match this.machine.tls.fetch_tls_dtor(Some(key), thread_id) {
281 dtor @ Some(_) => dtor,
282 // We ran each dtor once, start over from the beginning.
283 None => this.machine.tls.fetch_tls_dtor(None, thread_id),