75 lines
2.1 KiB
Rust
75 lines
2.1 KiB
Rust
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//! Utility for helping miri understand our exposed pointers.
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//!
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//! During normal execution, this module is equivalent to pointer casts. However, when running
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//! under miri, pointer casts are replaced with lookups in a hash map. This makes Tokio compatible
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//! with strict provenance when running under miri (which comes with a performance cost).
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use std::marker::PhantomData;
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#[cfg(miri)]
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use {crate::loom::sync::Mutex, std::collections::BTreeMap};
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pub(crate) struct PtrExposeDomain<T> {
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#[cfg(miri)]
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map: Mutex<BTreeMap<usize, *const T>>,
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_phantom: PhantomData<T>,
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}
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// SAFETY: Actually using the pointers is unsafe, so it's sound to transfer them across threads.
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unsafe impl<T> Sync for PtrExposeDomain<T> {}
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impl<T> PtrExposeDomain<T> {
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pub(crate) const fn new() -> Self {
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Self {
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#[cfg(miri)]
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map: Mutex::const_new(BTreeMap::new()),
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_phantom: PhantomData,
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}
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}
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#[inline]
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pub(crate) fn expose_provenance(&self, ptr: *const T) -> usize {
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#[cfg(miri)]
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{
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let addr: usize = ptr.addr();
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self.map.lock().insert(addr, ptr);
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addr
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}
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#[cfg(not(miri))]
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{
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ptr as usize
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}
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}
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#[inline]
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#[allow(clippy::wrong_self_convention)] // mirrors std name
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pub(crate) fn from_exposed_addr(&self, addr: usize) -> *const T {
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#[cfg(miri)]
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{
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let maybe_ptr = self.map.lock().get(&addr).copied();
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// SAFETY: Intentionally trigger a miri failure if the provenance we want is not
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// exposed.
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unsafe { maybe_ptr.unwrap_unchecked() }
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}
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#[cfg(not(miri))]
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{
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addr as *const T
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}
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}
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#[inline]
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pub(crate) fn unexpose_provenance(&self, _ptr: *const T) {
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#[cfg(miri)]
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{
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let addr: usize = _ptr.addr();
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let maybe_ptr = self.map.lock().remove(&addr);
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// SAFETY: Intentionally trigger a miri failure if the provenance we want is not
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// exposed.
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unsafe { maybe_ptr.unwrap_unchecked() };
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}
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}
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}
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