Rollup merge of #139630 - RalfJung:miri-sync, r=RalfJung

Miri subtree update

r? `@ghost`

a sync is needed to fix the miri-test-libstd failures

src/tools/miri/Cargo.lock

@@ -538,6 +538,7 @@ name = "miri"
 version = "0.1.0"
 dependencies = [
  "aes",
+ "bitflags",
  "chrono",
  "chrono-tz",
  "colored",

src/tools/miri/Cargo.toml

@@ -26,6 +26,7 @@ measureme = "12"
 chrono = { version = "0.4.38", default-features = false }
 chrono-tz = "0.10"
 directories = "6"
+bitflags = "2.6"
 
 # Copied from `compiler/rustc/Cargo.toml`.
 # But only for some targets, it fails for others. Rustc configures this in its CI, but we can't

src/tools/miri/ci/ci.sh

@@ -164,7 +164,7 @@ case $HOST_TARGET in
     # Partially supported targets (tier 2)
     BASIC="empty_main integer heap_alloc libc-mem vec string btreemap" # ensures we have the basics: pre-main code, system allocator
     UNIX="hello panic/panic panic/unwind concurrency/simple atomic libc-mem libc-misc libc-random env num_cpus" # the things that are very similar across all Unixes, and hence easily supported there
-    TEST_TARGET=x86_64-unknown-freebsd run_tests_minimal $BASIC $UNIX time hashmap random threadname pthread fs libc-pipe
+    TEST_TARGET=x86_64-unknown-freebsd run_tests_minimal $BASIC $UNIX time hashmap random threadname pthread fs libc-pipe concurrency sync
     TEST_TARGET=i686-unknown-freebsd   run_tests_minimal $BASIC $UNIX time hashmap random threadname pthread fs libc-pipe
     TEST_TARGET=aarch64-linux-android  run_tests_minimal $BASIC $UNIX time hashmap random sync concurrency thread epoll eventfd
     TEST_TARGET=wasm32-wasip2          run_tests_minimal $BASIC wasm

src/tools/miri/rust-version

@@ -1 +1 @@
-25a615bf829b9f6d6f22da537e3851043f92e5f2
+7d7de5bf3c3cbf9c2c5bbc5cbfb9197a8a427d35

src/tools/miri/src/shims/files.rs

@@ -1,6 +1,7 @@
 use std::any::Any;
 use std::collections::BTreeMap;
-use std::io::{IsTerminal, SeekFrom, Write};
+use std::fs::{File, Metadata};
+use std::io::{IsTerminal, Seek, SeekFrom, Write};
 use std::marker::CoercePointee;
 use std::ops::Deref;
 use std::rc::{Rc, Weak};
@@ -192,7 +193,7 @@ pub trait FileDescription: std::fmt::Debug + FileDescriptionExt {
         false
     }
 
-    fn as_unix(&self) -> &dyn UnixFileDescription {
+    fn as_unix<'tcx>(&self, _ecx: &MiriInterpCx<'tcx>) -> &dyn UnixFileDescription {
         panic!("Not a unix file descriptor: {}", self.name());
     }
 }
@@ -278,6 +279,97 @@ impl FileDescription for io::Stderr {
     }
 }
 
+#[derive(Debug)]
+pub struct FileHandle {
+    pub(crate) file: File,
+    pub(crate) writable: bool,
+}
+
+impl FileDescription for FileHandle {
+    fn name(&self) -> &'static str {
+        "file"
+    }
+
+    fn read<'tcx>(
+        self: FileDescriptionRef<Self>,
+        communicate_allowed: bool,
+        ptr: Pointer,
+        len: usize,
+        ecx: &mut MiriInterpCx<'tcx>,
+        finish: DynMachineCallback<'tcx, Result<usize, IoError>>,
+    ) -> InterpResult<'tcx> {
+        assert!(communicate_allowed, "isolation should have prevented even opening a file");
+
+        let result = ecx.read_from_host(&self.file, len, ptr)?;
+        finish.call(ecx, result)
+    }
+
+    fn write<'tcx>(
+        self: FileDescriptionRef<Self>,
+        communicate_allowed: bool,
+        ptr: Pointer,
+        len: usize,
+        ecx: &mut MiriInterpCx<'tcx>,
+        finish: DynMachineCallback<'tcx, Result<usize, IoError>>,
+    ) -> InterpResult<'tcx> {
+        assert!(communicate_allowed, "isolation should have prevented even opening a file");
+
+        let result = ecx.write_to_host(&self.file, len, ptr)?;
+        finish.call(ecx, result)
+    }
+
+    fn seek<'tcx>(
+        &self,
+        communicate_allowed: bool,
+        offset: SeekFrom,
+    ) -> InterpResult<'tcx, io::Result<u64>> {
+        assert!(communicate_allowed, "isolation should have prevented even opening a file");
+        interp_ok((&mut &self.file).seek(offset))
+    }
+
+    fn close<'tcx>(
+        self,
+        communicate_allowed: bool,
+        _ecx: &mut MiriInterpCx<'tcx>,
+    ) -> InterpResult<'tcx, io::Result<()>> {
+        assert!(communicate_allowed, "isolation should have prevented even opening a file");
+        // We sync the file if it was opened in a mode different than read-only.
+        if self.writable {
+            // `File::sync_all` does the checks that are done when closing a file. We do this to
+            // to handle possible errors correctly.
+            let result = self.file.sync_all();
+            // Now we actually close the file and return the result.
+            drop(self.file);
+            interp_ok(result)
+        } else {
+            // We drop the file, this closes it but ignores any errors
+            // produced when closing it. This is done because
+            // `File::sync_all` cannot be done over files like
+            // `/dev/urandom` which are read-only. Check
+            // https://github.com/rust-lang/miri/issues/999#issuecomment-568920439
+            // for a deeper discussion.
+            drop(self.file);
+            interp_ok(Ok(()))
+        }
+    }
+
+    fn metadata<'tcx>(&self) -> InterpResult<'tcx, io::Result<Metadata>> {
+        interp_ok(self.file.metadata())
+    }
+
+    fn is_tty(&self, communicate_allowed: bool) -> bool {
+        communicate_allowed && self.file.is_terminal()
+    }
+
+    fn as_unix<'tcx>(&self, ecx: &MiriInterpCx<'tcx>) -> &dyn UnixFileDescription {
+        assert!(
+            ecx.target_os_is_unix(),
+            "unix file operations are only available for unix targets"
+        );
+        self
+    }
+}
+
 /// Like /dev/null
 #[derive(Debug)]
 pub struct NullOutput;
@@ -300,10 +392,13 @@ impl FileDescription for NullOutput {
     }
 }
 
+/// Internal type of a file-descriptor - this is what [`FdTable`] expects
+pub type FdNum = i32;
+
 /// The file descriptor table
 #[derive(Debug)]
 pub struct FdTable {
-    pub fds: BTreeMap<i32, DynFileDescriptionRef>,
+    pub fds: BTreeMap<FdNum, DynFileDescriptionRef>,
     /// Unique identifier for file description, used to differentiate between various file description.
     next_file_description_id: FdId,
 }
@@ -339,12 +434,12 @@ impl FdTable {
     }
 
     /// Insert a new file description to the FdTable.
-    pub fn insert_new(&mut self, fd: impl FileDescription) -> i32 {
+    pub fn insert_new(&mut self, fd: impl FileDescription) -> FdNum {
         let fd_ref = self.new_ref(fd);
         self.insert(fd_ref)
     }
 
-    pub fn insert(&mut self, fd_ref: DynFileDescriptionRef) -> i32 {
+    pub fn insert(&mut self, fd_ref: DynFileDescriptionRef) -> FdNum {
         self.insert_with_min_num(fd_ref, 0)
     }
 
@@ -352,8 +447,8 @@ impl FdTable {
     pub fn insert_with_min_num(
         &mut self,
         file_handle: DynFileDescriptionRef,
-        min_fd_num: i32,
-    ) -> i32 {
+        min_fd_num: FdNum,
+    ) -> FdNum {
         // Find the lowest unused FD, starting from min_fd. If the first such unused FD is in
         // between used FDs, the find_map combinator will return it. If the first such unused FD
         // is after all other used FDs, the find_map combinator will return None, and we will use
@@ -379,16 +474,16 @@ impl FdTable {
         new_fd_num
     }
 
-    pub fn get(&self, fd_num: i32) -> Option<DynFileDescriptionRef> {
+    pub fn get(&self, fd_num: FdNum) -> Option<DynFileDescriptionRef> {
         let fd = self.fds.get(&fd_num)?;
         Some(fd.clone())
     }
 
-    pub fn remove(&mut self, fd_num: i32) -> Option<DynFileDescriptionRef> {
+    pub fn remove(&mut self, fd_num: FdNum) -> Option<DynFileDescriptionRef> {
         self.fds.remove(&fd_num)
     }
 
-    pub fn is_fd_num(&self, fd_num: i32) -> bool {
+    pub fn is_fd_num(&self, fd_num: FdNum) -> bool {
         self.fds.contains_key(&fd_num)
     }
 }

src/tools/miri/src/shims/time.rs

@@ -219,16 +219,8 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
         let filetime = this.deref_pointer_as(LPFILETIME_op, this.windows_ty_layout("FILETIME"))?;
 
-        let NANOS_PER_SEC = this.eval_windows_u64("time", "NANOS_PER_SEC");
-        let INTERVALS_PER_SEC = this.eval_windows_u64("time", "INTERVALS_PER_SEC");
-        let INTERVALS_TO_UNIX_EPOCH = this.eval_windows_u64("time", "INTERVALS_TO_UNIX_EPOCH");
-        let NANOS_PER_INTERVAL = NANOS_PER_SEC / INTERVALS_PER_SEC;
-        let SECONDS_TO_UNIX_EPOCH = INTERVALS_TO_UNIX_EPOCH / INTERVALS_PER_SEC;
-
-        let duration = system_time_to_duration(&SystemTime::now())?
-            + Duration::from_secs(SECONDS_TO_UNIX_EPOCH);
-        let duration_ticks = u64::try_from(duration.as_nanos() / u128::from(NANOS_PER_INTERVAL))
-            .map_err(|_| err_unsup_format!("programs running more than 2^64 Windows ticks after the Windows epoch are not supported"))?;
+        let duration = this.system_time_since_windows_epoch(&SystemTime::now())?;
+        let duration_ticks = this.windows_ticks_for(duration)?;
 
         let dwLowDateTime = u32::try_from(duration_ticks & 0x00000000FFFFFFFF).unwrap();
         let dwHighDateTime = u32::try_from((duration_ticks & 0xFFFFFFFF00000000) >> 32).unwrap();
@@ -281,6 +273,30 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         interp_ok(Scalar::from_i32(-1)) // Return non-zero on success
     }
 
+    #[allow(non_snake_case, clippy::arithmetic_side_effects)]
+    fn system_time_since_windows_epoch(&self, time: &SystemTime) -> InterpResult<'tcx, Duration> {
+        let this = self.eval_context_ref();
+
+        let INTERVALS_PER_SEC = this.eval_windows_u64("time", "INTERVALS_PER_SEC");
+        let INTERVALS_TO_UNIX_EPOCH = this.eval_windows_u64("time", "INTERVALS_TO_UNIX_EPOCH");
+        let SECONDS_TO_UNIX_EPOCH = INTERVALS_TO_UNIX_EPOCH / INTERVALS_PER_SEC;
+
+        interp_ok(system_time_to_duration(time)? + Duration::from_secs(SECONDS_TO_UNIX_EPOCH))
+    }
+
+    #[allow(non_snake_case, clippy::arithmetic_side_effects)]
+    fn windows_ticks_for(&self, duration: Duration) -> InterpResult<'tcx, u64> {
+        let this = self.eval_context_ref();
+
+        let NANOS_PER_SEC = this.eval_windows_u64("time", "NANOS_PER_SEC");
+        let INTERVALS_PER_SEC = this.eval_windows_u64("time", "INTERVALS_PER_SEC");
+        let NANOS_PER_INTERVAL = NANOS_PER_SEC / INTERVALS_PER_SEC;
+
+        let ticks = u64::try_from(duration.as_nanos() / u128::from(NANOS_PER_INTERVAL))
+            .map_err(|_| err_unsup_format!("programs running more than 2^64 Windows ticks after the Windows epoch are not supported"))?;
+        interp_ok(ticks)
+    }
+
     fn mach_absolute_time(&self) -> InterpResult<'tcx, Scalar> {
         let this = self.eval_context_ref();
 

src/tools/miri/src/shims/unix/fd.rs

@@ -121,7 +121,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             throw_unsup_format!("unsupported flags {:#x}", op);
         };
 
-        let result = fd.as_unix().flock(this.machine.communicate(), parsed_op)?;
+        let result = fd.as_unix(this).flock(this.machine.communicate(), parsed_op)?;
         // return `0` if flock is successful
         let result = result.map(|()| 0i32);
         interp_ok(Scalar::from_i32(this.try_unwrap_io_result(result)?))
@@ -273,7 +273,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 let Ok(offset) = u64::try_from(offset) else {
                     return this.set_last_error_and_return(LibcError("EINVAL"), dest);
                 };
-                fd.as_unix().pread(communicate, offset, buf, count, this, finish)?
+                fd.as_unix(this).pread(communicate, offset, buf, count, this, finish)?
             }
         };
         interp_ok(())
@@ -333,7 +333,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 let Ok(offset) = u64::try_from(offset) else {
                     return this.set_last_error_and_return(LibcError("EINVAL"), dest);
                 };
-                fd.as_unix().pwrite(communicate, buf, count, offset, this, finish)?
+                fd.as_unix(this).pwrite(communicate, buf, count, offset, this, finish)?
             }
         };
         interp_ok(())

src/tools/miri/src/shims/unix/freebsd/foreign_items.rs

@@ -2,6 +2,7 @@ use rustc_middle::ty::Ty;
 use rustc_span::Symbol;
 use rustc_target::callconv::{Conv, FnAbi};
 
+use super::sync::EvalContextExt as _;
 use crate::shims::unix::*;
 use crate::*;
 
@@ -55,6 +56,13 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(res, dest)?;
             }
 
+            // Synchronization primitives
+            "_umtx_op" => {
+                let [obj, op, val, uaddr, uaddr2] =
+                    this.check_shim(abi, Conv::C, link_name, args)?;
+                this._umtx_op(obj, op, val, uaddr, uaddr2, dest)?;
+            }
+
             // File related shims
             // For those, we both intercept `func` and `call@FBSD_1.0` symbols cases
             // since freebsd 12 the former form can be expected.

src/tools/miri/src/shims/unix/freebsd/mod.rs

@@ -1 +1,2 @@
 pub mod foreign_items;
+pub mod sync;

src/tools/miri/src/shims/unix/freebsd/sync.rs

@@ -0,0 +1,251 @@
+//! Contains FreeBSD-specific synchronization functions
+
+use core::time::Duration;
+
+use crate::concurrency::sync::FutexRef;
+use crate::*;
+
+pub struct FreeBsdFutex {
+    futex: FutexRef,
+}
+
+/// Extended variant of the `timespec` struct.
+pub struct UmtxTime {
+    timeout: Duration,
+    abs_time: bool,
+    timeout_clock: TimeoutClock,
+}
+
+impl<'tcx> EvalContextExt<'tcx> for crate::MiriInterpCx<'tcx> {}
+pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
+    /// Implementation of the FreeBSD [`_umtx_op`](https://man.freebsd.org/cgi/man.cgi?query=_umtx_op&sektion=2&manpath=FreeBSD+14.2-RELEASE+and+Ports) syscall.
+    /// This is used for futex operations on FreeBSD.
+    ///
+    /// `obj`: a pointer to the futex object (can be a lot of things, mostly *AtomicU32)
+    /// `op`: the futex operation to run
+    /// `val`: the current value of the object as a `c_long` (for wait/wake)
+    /// `uaddr`: `op`-specific optional parameter, pointer-sized integer or pointer to an `op`-specific struct
+    /// `uaddr2`: `op`-specific optional parameter, pointer-sized integer or pointer to an `op`-specific struct
+    /// `dest`: the place this syscall returns to, 0 for success, -1 for failure
+    ///
+    /// # Note
+    /// Curently only the WAIT and WAKE operations are implemented.
+    fn _umtx_op(
+        &mut self,
+        obj: &OpTy<'tcx>,
+        op: &OpTy<'tcx>,
+        val: &OpTy<'tcx>,
+        uaddr: &OpTy<'tcx>,
+        uaddr2: &OpTy<'tcx>,
+        dest: &MPlaceTy<'tcx>,
+    ) -> InterpResult<'tcx> {
+        let this = self.eval_context_mut();
+
+        let obj = this.read_pointer(obj)?;
+        let op = this.read_scalar(op)?.to_i32()?;
+        let val = this.read_target_usize(val)?;
+        let uaddr = this.read_target_usize(uaddr)?;
+        let uaddr2 = this.read_pointer(uaddr2)?;
+
+        let wait = this.eval_libc_i32("UMTX_OP_WAIT");
+        let wait_uint = this.eval_libc_i32("UMTX_OP_WAIT_UINT");
+        let wait_uint_private = this.eval_libc_i32("UMTX_OP_WAIT_UINT_PRIVATE");
+
+        let wake = this.eval_libc_i32("UMTX_OP_WAKE");
+        let wake_private = this.eval_libc_i32("UMTX_OP_WAKE_PRIVATE");
+
+        let timespec_layout = this.libc_ty_layout("timespec");
+        let umtx_time_layout = this.libc_ty_layout("_umtx_time");
+        assert!(
+            timespec_layout.size != umtx_time_layout.size,
+            "`struct timespec` and `struct _umtx_time` should have different sizes."
+        );
+
+        match op {
+            // UMTX_OP_WAIT_UINT and UMTX_OP_WAIT_UINT_PRIVATE only differ in whether they work across
+            // processes or not. For Miri, we can treat them the same.
+            op if op == wait || op == wait_uint || op == wait_uint_private => {
+                let obj_layout =
+                    if op == wait { this.machine.layouts.isize } else { this.machine.layouts.u32 };
+                let obj = this.ptr_to_mplace(obj, obj_layout);
+
+                // Read the Linux futex wait implementation in Miri to understand why this fence is needed.
+                this.atomic_fence(AtomicFenceOrd::SeqCst)?;
+                let obj_val = this
+                    .read_scalar_atomic(&obj, AtomicReadOrd::Acquire)?
+                    .to_bits(obj_layout.size)?; // isize and u32 can have different sizes
+
+                if obj_val == u128::from(val) {
+                    // This cannot fail since we already did an atomic acquire read on that pointer.
+                    // Acquire reads are only allowed on mutable memory.
+                    let futex_ref = this
+                        .get_sync_or_init(obj.ptr(), |_| FreeBsdFutex { futex: Default::default() })
+                        .unwrap()
+                        .futex
+                        .clone();
+
+                    // From the manual:
+                    // The timeout is specified by passing either the address of `struct timespec`, or its
+                    // extended variant, `struct _umtx_time`, as the `uaddr2` argument of _umtx_op().
+                    // They are distinguished by the `uaddr` value, which must be equal
+                    // to the size of the structure pointed to by `uaddr2`, casted to uintptr_t.
+                    let timeout = if this.ptr_is_null(uaddr2)? {
+                        // no timeout parameter
+                        None
+                    } else {
+                        if uaddr == umtx_time_layout.size.bytes() {
+                            // `uaddr2` points to a `struct _umtx_time`.
+                            let umtx_time_place = this.ptr_to_mplace(uaddr2, umtx_time_layout);
+
+                            let umtx_time = match this.read_umtx_time(&umtx_time_place)? {
+                                Some(ut) => ut,
+                                None => {
+                                    return this
+                                        .set_last_error_and_return(LibcError("EINVAL"), dest);
+                                }
+                            };
+
+                            let anchor = if umtx_time.abs_time {
+                                TimeoutAnchor::Absolute
+                            } else {
+                                TimeoutAnchor::Relative
+                            };
+
+                            Some((umtx_time.timeout_clock, anchor, umtx_time.timeout))
+                        } else if uaddr == timespec_layout.size.bytes() {
+                            // RealTime clock can't be used in isolation mode.
+                            this.check_no_isolation("`_umtx_op` with `timespec` timeout")?;
+
+                            // `uaddr2` points to a `struct timespec`.
+                            let timespec = this.ptr_to_mplace(uaddr2, timespec_layout);
+                            let duration = match this.read_timespec(&timespec)? {
+                                Some(duration) => duration,
+                                None => {
+                                    return this
+                                        .set_last_error_and_return(LibcError("EINVAL"), dest);
+                                }
+                            };
+
+                            // FreeBSD does not seem to document which clock is used when the timeout
+                            // is passed as a `struct timespec*`. Based on discussions online and the source
+                            // code (umtx_copyin_umtx_time() in kern_umtx.c), it seems to default to CLOCK_REALTIME,
+                            // so that's what we also do.
+                            // Discussion in golang: https://github.com/golang/go/issues/17168#issuecomment-250235271
+                            Some((TimeoutClock::RealTime, TimeoutAnchor::Relative, duration))
+                        } else {
+                            return this.set_last_error_and_return(LibcError("EINVAL"), dest);
+                        }
+                    };
+
+                    let dest = dest.clone();
+                    this.futex_wait(
+                        futex_ref,
+                        u32::MAX, // we set the bitset to include all bits
+                        timeout,
+                        callback!(
+                            @capture<'tcx> {
+                                dest: MPlaceTy<'tcx>,
+                            }
+                            |ecx, unblock: UnblockKind| match unblock {
+                                UnblockKind::Ready => {
+                                    // From the manual:
+                                    // If successful, all requests, except UMTX_SHM_CREAT and UMTX_SHM_LOOKUP
+                                    // sub-requests of the UMTX_OP_SHM request, will return zero.
+                                    ecx.write_int(0, &dest)
+                                }
+                                UnblockKind::TimedOut => {
+                                    ecx.set_last_error_and_return(LibcError("ETIMEDOUT"), &dest)
+                                }
+                            }
+                        ),
+                    );
+                    interp_ok(())
+                } else {
+                    // The manual doesn’t specify what should happen if the futex value doesn’t match the expected one.
+                    // On FreeBSD 14.2, testing shows that WAIT operations return 0 even when the value is incorrect.
+                    this.write_int(0, dest)?;
+                    interp_ok(())
+                }
+            }
+            // UMTX_OP_WAKE and UMTX_OP_WAKE_PRIVATE only differ in whether they work across
+            // processes or not. For Miri, we can treat them the same.
+            op if op == wake || op == wake_private => {
+                let Some(futex_ref) =
+                    this.get_sync_or_init(obj, |_| FreeBsdFutex { futex: Default::default() })
+                else {
+                    // From Linux implemenation:
+                    // No AllocId, or no live allocation at that AllocId.
+                    // Return an error code. (That seems nicer than silently doing something non-intuitive.)
+                    // This means that if an address gets reused by a new allocation,
+                    // we'll use an independent futex queue for this... that seems acceptable.
+                    return this.set_last_error_and_return(LibcError("EFAULT"), dest);
+                };
+                let futex_ref = futex_ref.futex.clone();
+
+                // Saturating cast for when usize is smaller than u64.
+                let count = usize::try_from(val).unwrap_or(usize::MAX);
+
+                // Read the Linux futex wake implementation in Miri to understand why this fence is needed.
+                this.atomic_fence(AtomicFenceOrd::SeqCst)?;
+
+                // `_umtx_op` doesn't return the amount of woken threads.
+                let _woken = this.futex_wake(
+                    &futex_ref,
+                    u32::MAX, // we set the bitset to include all bits
+                    count,
+                )?;
+
+                // From the manual:
+                // If successful, all requests, except UMTX_SHM_CREAT and UMTX_SHM_LOOKUP
+                // sub-requests of the UMTX_OP_SHM request, will return zero.
+                this.write_int(0, dest)?;
+                interp_ok(())
+            }
+            op => {
+                throw_unsup_format!("Miri does not support `_umtx_op` syscall with op={}", op)
+            }
+        }
+    }
+
+    /// Parses a `_umtx_time` struct.
+    /// Returns `None` if the underlying `timespec` struct is invalid.
+    fn read_umtx_time(&mut self, ut: &MPlaceTy<'tcx>) -> InterpResult<'tcx, Option<UmtxTime>> {
+        let this = self.eval_context_mut();
+        // Only flag allowed is UMTX_ABSTIME.
+        let abs_time = this.eval_libc_u32("UMTX_ABSTIME");
+
+        let timespec_place = this.project_field(ut, 0)?;
+        // Inner `timespec` must still be valid.
+        let duration = match this.read_timespec(&timespec_place)? {
+            Some(dur) => dur,
+            None => return interp_ok(None),
+        };
+
+        let flags_place = this.project_field(ut, 1)?;
+        let flags = this.read_scalar(&flags_place)?.to_u32()?;
+        let abs_time_flag = flags == abs_time;
+
+        let clock_id_place = this.project_field(ut, 2)?;
+        let clock_id = this.read_scalar(&clock_id_place)?.to_i32()?;
+        let timeout_clock = this.translate_umtx_time_clock_id(clock_id)?;
+
+        interp_ok(Some(UmtxTime { timeout: duration, abs_time: abs_time_flag, timeout_clock }))
+    }
+
+    /// Translate raw FreeBSD clockid to a Miri TimeoutClock.
+    /// FIXME: share this code with the pthread and clock_gettime shims.
+    fn translate_umtx_time_clock_id(&mut self, raw_id: i32) -> InterpResult<'tcx, TimeoutClock> {
+        let this = self.eval_context_mut();
+
+        let timeout = if raw_id == this.eval_libc_i32("CLOCK_REALTIME") {
+            // RealTime clock can't be used in isolation mode.
+            this.check_no_isolation("`_umtx_op` with `CLOCK_REALTIME` timeout")?;
+            TimeoutClock::RealTime
+        } else if raw_id == this.eval_libc_i32("CLOCK_MONOTONIC") {
+            TimeoutClock::Monotonic
+        } else {
+            throw_unsup_format!("unsupported clock id {raw_id}");
+        };
+        interp_ok(timeout)
+    }
+}

src/tools/miri/src/shims/unix/fs.rs

@@ -2,10 +2,9 @@
 
 use std::borrow::Cow;
 use std::fs::{
-    DirBuilder, File, FileType, Metadata, OpenOptions, ReadDir, read_dir, remove_dir, remove_file,
-    rename,
+    DirBuilder, File, FileType, OpenOptions, ReadDir, read_dir, remove_dir, remove_file, rename,
 };
-use std::io::{self, ErrorKind, IsTerminal, Read, Seek, SeekFrom, Write};
+use std::io::{self, ErrorKind, Read, Seek, SeekFrom, Write};
 use std::path::{Path, PathBuf};
 use std::time::SystemTime;
 
@@ -14,98 +13,11 @@ use rustc_data_structures::fx::FxHashMap;
 
 use self::shims::time::system_time_to_duration;
 use crate::helpers::check_min_vararg_count;
-use crate::shims::files::{EvalContextExt as _, FileDescription, FileDescriptionRef};
+use crate::shims::files::FileHandle;
 use crate::shims::os_str::bytes_to_os_str;
 use crate::shims::unix::fd::{FlockOp, UnixFileDescription};
 use crate::*;
 
-#[derive(Debug)]
-struct FileHandle {
-    file: File,
-    writable: bool,
-}
-
-impl FileDescription for FileHandle {
-    fn name(&self) -> &'static str {
-        "file"
-    }
-
-    fn read<'tcx>(
-        self: FileDescriptionRef<Self>,
-        communicate_allowed: bool,
-        ptr: Pointer,
-        len: usize,
-        ecx: &mut MiriInterpCx<'tcx>,
-        finish: DynMachineCallback<'tcx, Result<usize, IoError>>,
-    ) -> InterpResult<'tcx> {
-        assert!(communicate_allowed, "isolation should have prevented even opening a file");
-
-        let result = ecx.read_from_host(&self.file, len, ptr)?;
-        finish.call(ecx, result)
-    }
-
-    fn write<'tcx>(
-        self: FileDescriptionRef<Self>,
-        communicate_allowed: bool,
-        ptr: Pointer,
-        len: usize,
-        ecx: &mut MiriInterpCx<'tcx>,
-        finish: DynMachineCallback<'tcx, Result<usize, IoError>>,
-    ) -> InterpResult<'tcx> {
-        assert!(communicate_allowed, "isolation should have prevented even opening a file");
-
-        let result = ecx.write_to_host(&self.file, len, ptr)?;
-        finish.call(ecx, result)
-    }
-
-    fn seek<'tcx>(
-        &self,
-        communicate_allowed: bool,
-        offset: SeekFrom,
-    ) -> InterpResult<'tcx, io::Result<u64>> {
-        assert!(communicate_allowed, "isolation should have prevented even opening a file");
-        interp_ok((&mut &self.file).seek(offset))
-    }
-
-    fn close<'tcx>(
-        self,
-        communicate_allowed: bool,
-        _ecx: &mut MiriInterpCx<'tcx>,
-    ) -> InterpResult<'tcx, io::Result<()>> {
-        assert!(communicate_allowed, "isolation should have prevented even opening a file");
-        // We sync the file if it was opened in a mode different than read-only.
-        if self.writable {
-            // `File::sync_all` does the checks that are done when closing a file. We do this to
-            // to handle possible errors correctly.
-            let result = self.file.sync_all();
-            // Now we actually close the file and return the result.
-            drop(self.file);
-            interp_ok(result)
-        } else {
-            // We drop the file, this closes it but ignores any errors
-            // produced when closing it. This is done because
-            // `File::sync_all` cannot be done over files like
-            // `/dev/urandom` which are read-only. Check
-            // https://github.com/rust-lang/miri/issues/999#issuecomment-568920439
-            // for a deeper discussion.
-            drop(self.file);
-            interp_ok(Ok(()))
-        }
-    }
-
-    fn metadata<'tcx>(&self) -> InterpResult<'tcx, io::Result<Metadata>> {
-        interp_ok(self.file.metadata())
-    }
-
-    fn is_tty(&self, communicate_allowed: bool) -> bool {
-        communicate_allowed && self.file.is_terminal()
-    }
-
-    fn as_unix(&self) -> &dyn UnixFileDescription {
-        self
-    }
-}
-
 impl UnixFileDescription for FileHandle {
     fn pread<'tcx>(
         &self,

src/tools/miri/src/shims/unix/linux_like/epoll.rs

@@ -153,7 +153,7 @@ impl FileDescription for Epoll {
         interp_ok(Ok(()))
     }
 
-    fn as_unix(&self) -> &dyn UnixFileDescription {
+    fn as_unix<'tcx>(&self, _ecx: &MiriInterpCx<'tcx>) -> &dyn UnixFileDescription {
         self
     }
 }
@@ -590,7 +590,7 @@ fn check_and_update_one_event_interest<'tcx>(
     ecx: &MiriInterpCx<'tcx>,
 ) -> InterpResult<'tcx, bool> {
     // Get the bitmask of ready events for a file description.
-    let ready_events_bitmask = fd_ref.as_unix().get_epoll_ready_events()?.get_event_bitmask(ecx);
+    let ready_events_bitmask = fd_ref.as_unix(ecx).get_epoll_ready_events()?.get_event_bitmask(ecx);
     let epoll_event_interest = interest.borrow();
     let epfd = epoll_event_interest.weak_epfd.upgrade().unwrap();
     // This checks if any of the events specified in epoll_event_interest.events

src/tools/miri/src/shims/unix/linux_like/eventfd.rs

@@ -100,7 +100,7 @@ impl FileDescription for EventFd {
         eventfd_write(buf_place, self, ecx, finish)
     }
 
-    fn as_unix(&self) -> &dyn UnixFileDescription {
+    fn as_unix<'tcx>(&self, _ecx: &MiriInterpCx<'tcx>) -> &dyn UnixFileDescription {
         self
     }
 }

src/tools/miri/src/shims/unix/unnamed_socket.rs

@@ -107,7 +107,7 @@ impl FileDescription for AnonSocket {
         anonsocket_write(self, ptr, len, ecx, finish)
     }
 
-    fn as_unix(&self) -> &dyn UnixFileDescription {
+    fn as_unix<'tcx>(&self, _ecx: &MiriInterpCx<'tcx>) -> &dyn UnixFileDescription {
         self
     }
 }

src/tools/miri/src/shims/windows/foreign_items.rs

@@ -9,14 +9,9 @@ use rustc_target::callconv::{Conv, FnAbi};
 
 use self::shims::windows::handle::{Handle, PseudoHandle};
 use crate::shims::os_str::bytes_to_os_str;
-use crate::shims::windows::handle::HandleError;
 use crate::shims::windows::*;
 use crate::*;
 
-// The NTSTATUS STATUS_INVALID_HANDLE (0xC0000008) encoded as a HRESULT by setting the N bit.
-// (https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-erref/0642cb2f-2075-4469-918c-4441e69c548a)
-const STATUS_INVALID_HANDLE: u32 = 0xD0000008;
-
 pub fn is_dyn_sym(name: &str) -> bool {
     // std does dynamic detection for these symbols
     matches!(
@@ -26,57 +21,107 @@ pub fn is_dyn_sym(name: &str) -> bool {
 }
 
 #[cfg(windows)]
-fn win_absolute<'tcx>(path: &Path) -> InterpResult<'tcx, io::Result<PathBuf>> {
+fn win_get_full_path_name<'tcx>(path: &Path) -> InterpResult<'tcx, io::Result<PathBuf>> {
     // We are on Windows so we can simply let the host do this.
     interp_ok(path::absolute(path))
 }
 
 #[cfg(unix)]
 #[expect(clippy::get_first, clippy::arithmetic_side_effects)]
-fn win_absolute<'tcx>(path: &Path) -> InterpResult<'tcx, io::Result<PathBuf>> {
-    // We are on Unix, so we need to implement parts of the logic ourselves.
+fn win_get_full_path_name<'tcx>(path: &Path) -> InterpResult<'tcx, io::Result<PathBuf>> {
+    use std::sync::LazyLock;
+
+    use rustc_data_structures::fx::FxHashSet;
+
+    // We are on Unix, so we need to implement parts of the logic ourselves. `path` will use `/`
+    // separators, and the result should also use `/`.
+    // See <https://chrisdenton.github.io/omnipath/Overview.html#absolute-win32-paths> for more
+    // information about Windows paths.
+    // This does not handle all corner cases correctly, see
+    // <https://github.com/rust-lang/miri/pull/4262#issuecomment-2792168853> for more cursed
+    // examples.
     let bytes = path.as_os_str().as_encoded_bytes();
-    // If it starts with `//` (these were backslashes but are already converted)
-    // then this is a magic special path, we just leave it unchanged.
-    if bytes.get(0).copied() == Some(b'/') && bytes.get(1).copied() == Some(b'/') {
+    // If it starts with `//./` or `//?/` then this is a magic special path, we just leave it
+    // unchanged.
+    if bytes.get(0).copied() == Some(b'/')
+        && bytes.get(1).copied() == Some(b'/')
+        && matches!(bytes.get(2), Some(b'.' | b'?'))
+        && bytes.get(3).copied() == Some(b'/')
+    {
         return interp_ok(Ok(path.into()));
     };
-    // Special treatment for Windows' magic filenames: they are treated as being relative to `\\.\`.
-    let magic_filenames = &[
-        "CON", "PRN", "AUX", "NUL", "COM1", "COM2", "COM3", "COM4", "COM5", "COM6", "COM7", "COM8",
-        "COM9", "LPT1", "LPT2", "LPT3", "LPT4", "LPT5", "LPT6", "LPT7", "LPT8", "LPT9",
-    ];
-    if magic_filenames.iter().any(|m| m.as_bytes() == bytes) {
-        let mut result: Vec<u8> = br"//./".into();
+    let is_unc = bytes.starts_with(b"//");
+    // Special treatment for Windows' magic filenames: they are treated as being relative to `//./`.
+    static MAGIC_FILENAMES: LazyLock<FxHashSet<&'static str>> = LazyLock::new(|| {
+        FxHashSet::from_iter([
+            "CON", "PRN", "AUX", "NUL", "COM1", "COM2", "COM3", "COM4", "COM5", "COM6", "COM7",
+            "COM8", "COM9", "LPT1", "LPT2", "LPT3", "LPT4", "LPT5", "LPT6", "LPT7", "LPT8", "LPT9",
+        ])
+    });
+    if str::from_utf8(bytes).is_ok_and(|s| MAGIC_FILENAMES.contains(&*s.to_ascii_uppercase())) {
+        let mut result: Vec<u8> = b"//./".into();
         result.extend(bytes);
         return interp_ok(Ok(bytes_to_os_str(&result)?.into()));
     }
     // Otherwise we try to do something kind of close to what Windows does, but this is probably not
-    // right in all cases. We iterate over the components between `/`, and remove trailing `.`,
-    // except that trailing `..` remain unchanged.
-    let mut result = vec![];
+    // right in all cases.
+    let mut result: Vec<&[u8]> = vec![]; // will be a vecot of components, joined by `/`.
     let mut bytes = bytes; // the remaining bytes to process
-    loop {
-        let len = bytes.iter().position(|&b| b == b'/').unwrap_or(bytes.len());
-        let mut component = &bytes[..len];
-        if len >= 2 && component[len - 1] == b'.' && component[len - 2] != b'.' {
-            // Strip trailing `.`
+    let mut stop = false;
+    while !stop {
+        // Find next component, and advance `bytes`.
+        let mut component = match bytes.iter().position(|&b| b == b'/') {
+            Some(pos) => {
+                let (component, tail) = bytes.split_at(pos);
+                bytes = &tail[1..]; // remove the `/`.
+                component
+            }
+            None => {
+                // There's no more `/`.
+                stop = true;
+                let component = bytes;
+                bytes = &[];
+                component
+            }
+        };
+        // `NUL` and only `NUL` also gets changed to be relative to `//./` later in the path.
+        // (This changed with Windows 11; previously, all magic filenames behaved like this.)
+        // Also, this does not apply to UNC paths.
+        if !is_unc && component.eq_ignore_ascii_case(b"NUL") {
+            let mut result: Vec<u8> = b"//./".into();
+            result.extend(component);
+            return interp_ok(Ok(bytes_to_os_str(&result)?.into()));
+        }
+        // Deal with `..` -- Windows handles this entirely syntactically.
+        if component == b".." {
+            // Remove previous component, unless we are at the "root" already, then just ignore the `..`.
+            let is_root = {
+                // Paths like `/C:`.
+                result.len() == 2 && matches!(result[0], []) && matches!(result[1], [_, b':'])
+            } || {
+                // Paths like `//server/share`
+                result.len() == 4 && matches!(result[0], []) && matches!(result[1], [])
+            };
+            if !is_root {
+                result.pop();
+            }
+            continue;
+        }
+        // Preserve this component.
+        // Strip trailing `.`, but preserve trailing `..`. But not for UNC paths!
+        let len = component.len();
+        if !is_unc && len >= 2 && component[len - 1] == b'.' && component[len - 2] != b'.' {
             component = &component[..len - 1];
         }
         // Add this component to output.
-        result.extend(component);
-        // Prepare next iteration.
-        if len < bytes.len() {
-            // There's a component after this; add `/` and process remaining bytes.
-            result.push(b'/');
-            bytes = &bytes[len + 1..];
-            continue;
-        } else {
-            // This was the last component and it did not have a trailing `/`.
-            break;
-        }
+        result.push(component);
     }
-    // Let the host `absolute` function do working-dir handling
+    // Drive letters must be followed by a `/`.
+    if result.len() == 2 && matches!(result[0], []) && matches!(result[1], [_, b':']) {
+        result.push(&[]);
+    }
+    // Let the host `absolute` function do working-dir handling.
+    let result = result.join(&b'/');
     interp_ok(path::absolute(bytes_to_os_str(&result)?))
 }
 
@@ -231,7 +276,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 }
 
                 let filename = this.read_path_from_wide_str(filename)?;
-                let result = match win_absolute(&filename)? {
+                let result = match win_get_full_path_name(&filename)? {
                     Err(err) => {
                         this.set_last_error(err)?;
                         Scalar::from_u32(0) // return zero upon failure
@@ -246,6 +291,32 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 };
                 this.write_scalar(result, dest)?;
             }
+            "CreateFileW" => {
+                let [
+                    file_name,
+                    desired_access,
+                    share_mode,
+                    security_attributes,
+                    creation_disposition,
+                    flags_and_attributes,
+                    template_file,
+                ] = this.check_shim(abi, sys_conv, link_name, args)?;
+                let handle = this.CreateFileW(
+                    file_name,
+                    desired_access,
+                    share_mode,
+                    security_attributes,
+                    creation_disposition,
+                    flags_and_attributes,
+                    template_file,
+                )?;
+                this.write_scalar(handle.to_scalar(this), dest)?;
+            }
+            "GetFileInformationByHandle" => {
+                let [handle, info] = this.check_shim(abi, sys_conv, link_name, args)?;
+                let res = this.GetFileInformationByHandle(handle, info)?;
+                this.write_scalar(res, dest)?;
+            }
 
             // Allocation
             "HeapAlloc" => {
@@ -498,52 +569,37 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             "SetThreadDescription" => {
                 let [handle, name] = this.check_shim(abi, sys_conv, link_name, args)?;
 
-                let handle = this.read_scalar(handle)?;
+                let handle = this.read_handle(handle, "SetThreadDescription")?;
                 let name = this.read_wide_str(this.read_pointer(name)?)?;
 
-                let thread = match Handle::try_from_scalar(handle, this)? {
-                    Ok(Handle::Thread(thread)) => Ok(thread),
-                    Ok(Handle::Pseudo(PseudoHandle::CurrentThread)) => Ok(this.active_thread()),
-                    Ok(_) | Err(HandleError::InvalidHandle) =>
-                        this.invalid_handle("SetThreadDescription")?,
-                    Err(HandleError::ThreadNotFound(e)) => Err(e),
+                let thread = match handle {
+                    Handle::Thread(thread) => thread,
+                    Handle::Pseudo(PseudoHandle::CurrentThread) => this.active_thread(),
+                    _ => this.invalid_handle("SetThreadDescription")?,
                 };
-                let res = match thread {
-                    Ok(thread) => {
-                        // FIXME: use non-lossy conversion
-                        this.set_thread_name(thread, String::from_utf16_lossy(&name).into_bytes());
-                        Scalar::from_u32(0)
-                    }
-                    Err(_) => Scalar::from_u32(STATUS_INVALID_HANDLE),
-                };
-
-                this.write_scalar(res, dest)?;
+                // FIXME: use non-lossy conversion
+                this.set_thread_name(thread, String::from_utf16_lossy(&name).into_bytes());
+                this.write_scalar(Scalar::from_u32(0), dest)?;
             }
             "GetThreadDescription" => {
                 let [handle, name_ptr] = this.check_shim(abi, sys_conv, link_name, args)?;
 
-                let handle = this.read_scalar(handle)?;
+                let handle = this.read_handle(handle, "GetThreadDescription")?;
                 let name_ptr = this.deref_pointer_as(name_ptr, this.machine.layouts.mut_raw_ptr)?; // the pointer where we should store the ptr to the name
 
-                let thread = match Handle::try_from_scalar(handle, this)? {
-                    Ok(Handle::Thread(thread)) => Ok(thread),
-                    Ok(Handle::Pseudo(PseudoHandle::CurrentThread)) => Ok(this.active_thread()),
-                    Ok(_) | Err(HandleError::InvalidHandle) =>
-                        this.invalid_handle("GetThreadDescription")?,
-                    Err(HandleError::ThreadNotFound(e)) => Err(e),
-                };
-                let (name, res) = match thread {
-                    Ok(thread) => {
-                        // Looks like the default thread name is empty.
-                        let name = this.get_thread_name(thread).unwrap_or(b"").to_owned();
-                        let name = this.alloc_os_str_as_wide_str(
-                            bytes_to_os_str(&name)?,
-                            MiriMemoryKind::WinLocal.into(),
-                        )?;
-                        (Scalar::from_maybe_pointer(name, this), Scalar::from_u32(0))
-                    }
-                    Err(_) => (Scalar::null_ptr(this), Scalar::from_u32(STATUS_INVALID_HANDLE)),
+                let thread = match handle {
+                    Handle::Thread(thread) => thread,
+                    Handle::Pseudo(PseudoHandle::CurrentThread) => this.active_thread(),
+                    _ => this.invalid_handle("GetThreadDescription")?,
                 };
+                // Looks like the default thread name is empty.
+                let name = this.get_thread_name(thread).unwrap_or(b"").to_owned();
+                let name = this.alloc_os_str_as_wide_str(
+                    bytes_to_os_str(&name)?,
+                    MiriMemoryKind::WinLocal.into(),
+                )?;
+                let name = Scalar::from_maybe_pointer(name, this);
+                let res = Scalar::from_u32(0);
 
                 this.write_scalar(name, &name_ptr)?;
                 this.write_scalar(res, dest)?;
@@ -638,11 +694,11 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 let [handle, filename, size] = this.check_shim(abi, sys_conv, link_name, args)?;
                 this.check_no_isolation("`GetModuleFileNameW`")?;
 
-                let handle = this.read_target_usize(handle)?;
+                let handle = this.read_handle(handle, "GetModuleFileNameW")?;
                 let filename = this.read_pointer(filename)?;
                 let size = this.read_scalar(size)?.to_u32()?;
 
-                if handle != 0 {
+                if handle != Handle::Null {
                     throw_unsup_format!("`GetModuleFileNameW` only supports the NULL handle");
                 }
 

src/tools/miri/src/shims/windows/fs.rs

@@ -0,0 +1,402 @@
+use std::fs::{Metadata, OpenOptions};
+use std::io;
+use std::path::PathBuf;
+use std::time::SystemTime;
+
+use bitflags::bitflags;
+
+use crate::shims::files::{FileDescription, FileHandle};
+use crate::shims::windows::handle::{EvalContextExt as _, Handle};
+use crate::*;
+
+#[derive(Debug)]
+pub struct DirHandle {
+    pub(crate) path: PathBuf,
+}
+
+impl FileDescription for DirHandle {
+    fn name(&self) -> &'static str {
+        "directory"
+    }
+
+    fn metadata<'tcx>(&self) -> InterpResult<'tcx, io::Result<Metadata>> {
+        interp_ok(self.path.metadata())
+    }
+
+    fn close<'tcx>(
+        self,
+        _communicate_allowed: bool,
+        _ecx: &mut MiriInterpCx<'tcx>,
+    ) -> InterpResult<'tcx, io::Result<()>> {
+        interp_ok(Ok(()))
+    }
+}
+
+/// Windows supports handles without any read/write/delete permissions - these handles can get
+/// metadata, but little else. We represent that by storing the metadata from the time the handle
+/// was opened.
+#[derive(Debug)]
+pub struct MetadataHandle {
+    pub(crate) meta: Metadata,
+}
+
+impl FileDescription for MetadataHandle {
+    fn name(&self) -> &'static str {
+        "metadata-only"
+    }
+
+    fn metadata<'tcx>(&self) -> InterpResult<'tcx, io::Result<Metadata>> {
+        interp_ok(Ok(self.meta.clone()))
+    }
+
+    fn close<'tcx>(
+        self,
+        _communicate_allowed: bool,
+        _ecx: &mut MiriInterpCx<'tcx>,
+    ) -> InterpResult<'tcx, io::Result<()>> {
+        interp_ok(Ok(()))
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq)]
+enum CreationDisposition {
+    CreateAlways,
+    CreateNew,
+    OpenAlways,
+    OpenExisting,
+    TruncateExisting,
+}
+
+impl CreationDisposition {
+    fn new<'tcx>(
+        value: u32,
+        ecx: &mut MiriInterpCx<'tcx>,
+    ) -> InterpResult<'tcx, CreationDisposition> {
+        let create_always = ecx.eval_windows_u32("c", "CREATE_ALWAYS");
+        let create_new = ecx.eval_windows_u32("c", "CREATE_NEW");
+        let open_always = ecx.eval_windows_u32("c", "OPEN_ALWAYS");
+        let open_existing = ecx.eval_windows_u32("c", "OPEN_EXISTING");
+        let truncate_existing = ecx.eval_windows_u32("c", "TRUNCATE_EXISTING");
+
+        let out = if value == create_always {
+            CreationDisposition::CreateAlways
+        } else if value == create_new {
+            CreationDisposition::CreateNew
+        } else if value == open_always {
+            CreationDisposition::OpenAlways
+        } else if value == open_existing {
+            CreationDisposition::OpenExisting
+        } else if value == truncate_existing {
+            CreationDisposition::TruncateExisting
+        } else {
+            throw_unsup_format!("CreateFileW: Unsupported creation disposition: {value}");
+        };
+        interp_ok(out)
+    }
+}
+
+bitflags! {
+    #[derive(PartialEq)]
+    struct FileAttributes: u32 {
+        const ZERO = 0;
+        const NORMAL = 1 << 0;
+        /// This must be passed to allow getting directory handles. If not passed, we error on trying
+        /// to open directories
+        const BACKUP_SEMANTICS = 1 << 1;
+        /// Open a reparse point as a regular file - this is basically similar to 'readlink' in Unix
+        /// terminology. A reparse point is a file with custom logic when navigated to, of which
+        /// a symlink is one specific example.
+        const OPEN_REPARSE = 1 << 2;
+    }
+}
+
+impl FileAttributes {
+    fn new<'tcx>(
+        mut value: u32,
+        ecx: &mut MiriInterpCx<'tcx>,
+    ) -> InterpResult<'tcx, FileAttributes> {
+        let file_attribute_normal = ecx.eval_windows_u32("c", "FILE_ATTRIBUTE_NORMAL");
+        let file_flag_backup_semantics = ecx.eval_windows_u32("c", "FILE_FLAG_BACKUP_SEMANTICS");
+        let file_flag_open_reparse_point =
+            ecx.eval_windows_u32("c", "FILE_FLAG_OPEN_REPARSE_POINT");
+
+        let mut out = FileAttributes::ZERO;
+        if value & file_flag_backup_semantics != 0 {
+            value &= !file_flag_backup_semantics;
+            out |= FileAttributes::BACKUP_SEMANTICS;
+        }
+        if value & file_flag_open_reparse_point != 0 {
+            value &= !file_flag_open_reparse_point;
+            out |= FileAttributes::OPEN_REPARSE;
+        }
+        if value & file_attribute_normal != 0 {
+            value &= !file_attribute_normal;
+            out |= FileAttributes::NORMAL;
+        }
+
+        if value != 0 {
+            throw_unsup_format!("CreateFileW: Unsupported flags_and_attributes: {value}");
+        }
+
+        if out == FileAttributes::ZERO {
+            // NORMAL is equivalent to 0. Avoid needing to check both cases by unifying the two.
+            out = FileAttributes::NORMAL;
+        }
+        interp_ok(out)
+    }
+}
+
+impl<'tcx> EvalContextExt<'tcx> for crate::MiriInterpCx<'tcx> {}
+#[allow(non_snake_case)]
+pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
+    fn CreateFileW(
+        &mut self,
+        file_name: &OpTy<'tcx>,            // LPCWSTR
+        desired_access: &OpTy<'tcx>,       // DWORD
+        share_mode: &OpTy<'tcx>,           // DWORD
+        security_attributes: &OpTy<'tcx>,  // LPSECURITY_ATTRIBUTES
+        creation_disposition: &OpTy<'tcx>, // DWORD
+        flags_and_attributes: &OpTy<'tcx>, // DWORD
+        template_file: &OpTy<'tcx>,        // HANDLE
+    ) -> InterpResult<'tcx, Handle> {
+        // ^ Returns HANDLE
+        use CreationDisposition::*;
+
+        let this = self.eval_context_mut();
+        this.assert_target_os("windows", "CreateFileW");
+        this.check_no_isolation("`CreateFileW`")?;
+
+        // This function appears to always set the error to 0. This is important for some flag
+        // combinations, which may set error code on success.
+        this.set_last_error(IoError::Raw(Scalar::from_i32(0)))?;
+
+        let file_name = this.read_path_from_wide_str(this.read_pointer(file_name)?)?;
+        let mut desired_access = this.read_scalar(desired_access)?.to_u32()?;
+        let share_mode = this.read_scalar(share_mode)?.to_u32()?;
+        let security_attributes = this.read_pointer(security_attributes)?;
+        let creation_disposition = this.read_scalar(creation_disposition)?.to_u32()?;
+        let flags_and_attributes = this.read_scalar(flags_and_attributes)?.to_u32()?;
+        let template_file = this.read_target_usize(template_file)?;
+
+        let generic_read = this.eval_windows_u32("c", "GENERIC_READ");
+        let generic_write = this.eval_windows_u32("c", "GENERIC_WRITE");
+
+        let file_share_delete = this.eval_windows_u32("c", "FILE_SHARE_DELETE");
+        let file_share_read = this.eval_windows_u32("c", "FILE_SHARE_READ");
+        let file_share_write = this.eval_windows_u32("c", "FILE_SHARE_WRITE");
+
+        let creation_disposition = CreationDisposition::new(creation_disposition, this)?;
+        let attributes = FileAttributes::new(flags_and_attributes, this)?;
+
+        if share_mode != (file_share_delete | file_share_read | file_share_write) {
+            throw_unsup_format!("CreateFileW: Unsupported share mode: {share_mode}");
+        }
+        if !this.ptr_is_null(security_attributes)? {
+            throw_unsup_format!("CreateFileW: Security attributes are not supported");
+        }
+
+        if attributes.contains(FileAttributes::OPEN_REPARSE) && creation_disposition == CreateAlways
+        {
+            throw_machine_stop!(TerminationInfo::Abort("Invalid CreateFileW argument combination: FILE_FLAG_OPEN_REPARSE_POINT with CREATE_ALWAYS".to_string()));
+        }
+
+        if template_file != 0 {
+            throw_unsup_format!("CreateFileW: Template files are not supported");
+        }
+
+        // We need to know if the file is a directory to correctly open directory handles.
+        // This is racy, but currently the stdlib doesn't appear to offer a better solution.
+        let is_dir = file_name.is_dir();
+
+        // BACKUP_SEMANTICS is how Windows calls the act of opening a directory handle.
+        if !attributes.contains(FileAttributes::BACKUP_SEMANTICS) && is_dir {
+            this.set_last_error(IoError::WindowsError("ERROR_ACCESS_DENIED"))?;
+            return interp_ok(Handle::Invalid);
+        }
+
+        let desired_read = desired_access & generic_read != 0;
+        let desired_write = desired_access & generic_write != 0;
+
+        let mut options = OpenOptions::new();
+        if desired_read {
+            desired_access &= !generic_read;
+            options.read(true);
+        }
+        if desired_write {
+            desired_access &= !generic_write;
+            options.write(true);
+        }
+
+        if desired_access != 0 {
+            throw_unsup_format!(
+                "CreateFileW: Unsupported bits set for access mode: {desired_access:#x}"
+            );
+        }
+
+        // Per the documentation:
+        // If the specified file exists and is writable, the function truncates the file,
+        // the function succeeds, and last-error code is set to ERROR_ALREADY_EXISTS.
+        // If the specified file does not exist and is a valid path, a new file is created,
+        // the function succeeds, and the last-error code is set to zero.
+        // https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilew
+        //
+        // This is racy, but there doesn't appear to be an std API that both succeeds if a
+        // file exists but tells us it isn't new. Either we accept racing one way or another,
+        // or we use an iffy heuristic like file creation time. This implementation prefers
+        // to fail in the direction of erroring more often.
+        if let CreateAlways | OpenAlways = creation_disposition
+            && file_name.exists()
+        {
+            this.set_last_error(IoError::WindowsError("ERROR_ALREADY_EXISTS"))?;
+        }
+
+        let handle = if is_dir {
+            // Open this as a directory.
+            let fd_num = this.machine.fds.insert_new(DirHandle { path: file_name });
+            Ok(Handle::File(fd_num))
+        } else if creation_disposition == OpenExisting && !(desired_read || desired_write) {
+            // Windows supports handles with no permissions. These allow things such as reading
+            // metadata, but not file content.
+            file_name.metadata().map(|meta| {
+                let fd_num = this.machine.fds.insert_new(MetadataHandle { meta });
+                Handle::File(fd_num)
+            })
+        } else {
+            // Open this as a standard file.
+            match creation_disposition {
+                CreateAlways | OpenAlways => {
+                    options.create(true);
+                    if creation_disposition == CreateAlways {
+                        options.truncate(true);
+                    }
+                }
+                CreateNew => {
+                    options.create_new(true);
+                    // Per `create_new` documentation:
+                    // The file must be opened with write or append access in order to create a new file.
+                    // https://doc.rust-lang.org/std/fs/struct.OpenOptions.html#method.create_new
+                    if !desired_write {
+                        options.append(true);
+                    }
+                }
+                OpenExisting => {} // Default options
+                TruncateExisting => {
+                    options.truncate(true);
+                }
+            }
+
+            options.open(file_name).map(|file| {
+                let fd_num =
+                    this.machine.fds.insert_new(FileHandle { file, writable: desired_write });
+                Handle::File(fd_num)
+            })
+        };
+
+        match handle {
+            Ok(handle) => interp_ok(handle),
+            Err(e) => {
+                this.set_last_error(e)?;
+                interp_ok(Handle::Invalid)
+            }
+        }
+    }
+
+    fn GetFileInformationByHandle(
+        &mut self,
+        file: &OpTy<'tcx>,             // HANDLE
+        file_information: &OpTy<'tcx>, // LPBY_HANDLE_FILE_INFORMATION
+    ) -> InterpResult<'tcx, Scalar> {
+        // ^ Returns BOOL (i32 on Windows)
+        let this = self.eval_context_mut();
+        this.assert_target_os("windows", "GetFileInformationByHandle");
+        this.check_no_isolation("`GetFileInformationByHandle`")?;
+
+        let file = this.read_handle(file, "GetFileInformationByHandle")?;
+        let file_information = this.deref_pointer_as(
+            file_information,
+            this.windows_ty_layout("BY_HANDLE_FILE_INFORMATION"),
+        )?;
+
+        let fd_num = if let Handle::File(fd_num) = file {
+            fd_num
+        } else {
+            this.invalid_handle("GetFileInformationByHandle")?
+        };
+
+        let Some(desc) = this.machine.fds.get(fd_num) else {
+            this.invalid_handle("GetFileInformationByHandle")?
+        };
+
+        let metadata = match desc.metadata()? {
+            Ok(meta) => meta,
+            Err(e) => {
+                this.set_last_error(e)?;
+                return interp_ok(this.eval_windows("c", "FALSE"));
+            }
+        };
+
+        let size = metadata.len();
+
+        let file_type = metadata.file_type();
+        let attributes = if file_type.is_dir() {
+            this.eval_windows_u32("c", "FILE_ATTRIBUTE_DIRECTORY")
+        } else if file_type.is_file() {
+            this.eval_windows_u32("c", "FILE_ATTRIBUTE_NORMAL")
+        } else {
+            this.eval_windows_u32("c", "FILE_ATTRIBUTE_DEVICE")
+        };
+
+        // Per the Windows documentation:
+        // "If the underlying file system does not support the [...] time, this member is zero (0)."
+        // https://learn.microsoft.com/en-us/windows/win32/api/fileapi/ns-fileapi-by_handle_file_information
+        let created = extract_windows_epoch(this, metadata.created())?.unwrap_or((0, 0));
+        let accessed = extract_windows_epoch(this, metadata.accessed())?.unwrap_or((0, 0));
+        let written = extract_windows_epoch(this, metadata.modified())?.unwrap_or((0, 0));
+
+        this.write_int_fields_named(&[("dwFileAttributes", attributes.into())], &file_information)?;
+        write_filetime_field(this, &file_information, "ftCreationTime", created)?;
+        write_filetime_field(this, &file_information, "ftLastAccessTime", accessed)?;
+        write_filetime_field(this, &file_information, "ftLastWriteTime", written)?;
+        this.write_int_fields_named(
+            &[
+                ("dwVolumeSerialNumber", 0),
+                ("nFileSizeHigh", (size >> 32).into()),
+                ("nFileSizeLow", (size & 0xFFFFFFFF).into()),
+                ("nNumberOfLinks", 1),
+                ("nFileIndexHigh", 0),
+                ("nFileIndexLow", 0),
+            ],
+            &file_information,
+        )?;
+
+        interp_ok(this.eval_windows("c", "TRUE"))
+    }
+}
+
+/// Windows FILETIME is measured in 100-nanosecs since 1601
+fn extract_windows_epoch<'tcx>(
+    ecx: &MiriInterpCx<'tcx>,
+    time: io::Result<SystemTime>,
+) -> InterpResult<'tcx, Option<(u32, u32)>> {
+    match time.ok() {
+        Some(time) => {
+            let duration = ecx.system_time_since_windows_epoch(&time)?;
+            let duration_ticks = ecx.windows_ticks_for(duration)?;
+            #[allow(clippy::cast_possible_truncation)]
+            interp_ok(Some((duration_ticks as u32, (duration_ticks >> 32) as u32)))
+        }
+        None => interp_ok(None),
+    }
+}
+
+fn write_filetime_field<'tcx>(
+    cx: &mut MiriInterpCx<'tcx>,
+    val: &MPlaceTy<'tcx>,
+    name: &str,
+    (low, high): (u32, u32),
+) -> InterpResult<'tcx> {
+    cx.write_int_fields_named(
+        &[("dwLowDateTime", low.into()), ("dwHighDateTime", high.into())],
+        &cx.project_field_named(val, name)?,
+    )
+}

src/tools/miri/src/shims/windows/handle.rs

@@ -3,6 +3,7 @@ use std::mem::variant_count;
 use rustc_abi::HasDataLayout;
 
 use crate::concurrency::thread::ThreadNotFound;
+use crate::shims::files::FdNum;
 use crate::*;
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
@@ -16,6 +17,8 @@ pub enum Handle {
     Null,
     Pseudo(PseudoHandle),
     Thread(ThreadId),
+    File(FdNum),
+    Invalid,
 }
 
 impl PseudoHandle {
@@ -47,12 +50,18 @@ impl Handle {
     const NULL_DISCRIMINANT: u32 = 0;
     const PSEUDO_DISCRIMINANT: u32 = 1;
     const THREAD_DISCRIMINANT: u32 = 2;
+    const FILE_DISCRIMINANT: u32 = 3;
+    // Chosen to ensure Handle::Invalid encodes to -1. Update this value if there are ever more than
+    // 8 discriminants.
+    const INVALID_DISCRIMINANT: u32 = 7;
 
     fn discriminant(self) -> u32 {
         match self {
             Self::Null => Self::NULL_DISCRIMINANT,
             Self::Pseudo(_) => Self::PSEUDO_DISCRIMINANT,
             Self::Thread(_) => Self::THREAD_DISCRIMINANT,
+            Self::File(_) => Self::FILE_DISCRIMINANT,
+            Self::Invalid => Self::INVALID_DISCRIMINANT,
         }
     }
 
@@ -61,17 +70,27 @@ impl Handle {
             Self::Null => 0,
             Self::Pseudo(pseudo_handle) => pseudo_handle.value(),
             Self::Thread(thread) => thread.to_u32(),
+            #[expect(clippy::cast_sign_loss)]
+            Self::File(fd) => fd as u32,
+            // INVALID_HANDLE_VALUE is -1. This fact is explicitly declared or implied in several
+            // pages of Windows documentation.
+            // 1: https://learn.microsoft.com/en-us/dotnet/api/microsoft.win32.safehandles.safefilehandle?view=net-9.0
+            // 2: https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/get-osfhandle?view=msvc-170
+            Self::Invalid => 0x1FFFFFFF,
         }
     }
 
     fn packed_disc_size() -> u32 {
-        // ceil(log2(x)) is how many bits it takes to store x numbers
+        // ceil(log2(x)) is how many bits it takes to store x numbers.
+        // We ensure that INVALID_HANDLE_VALUE (0xFFFFFFFF) decodes to Handle::Invalid.
+        // see https://devblogs.microsoft.com/oldnewthing/20230914-00/?p=108766 for more detail on
+        // INVALID_HANDLE_VALUE.
         let variant_count = variant_count::<Self>();
 
-        // however, std's ilog2 is floor(log2(x))
+        // However, std's ilog2 is floor(log2(x)).
         let floor_log2 = variant_count.ilog2();
 
-        // we need to add one for non powers of two to compensate for the difference
+        // We need to add one for non powers of two to compensate for the difference.
         #[expect(clippy::arithmetic_side_effects)] // cannot overflow
         if variant_count.is_power_of_two() { floor_log2 } else { floor_log2 + 1 }
     }
@@ -105,6 +124,13 @@ impl Handle {
             Self::NULL_DISCRIMINANT if data == 0 => Some(Self::Null),
             Self::PSEUDO_DISCRIMINANT => Some(Self::Pseudo(PseudoHandle::from_value(data)?)),
             Self::THREAD_DISCRIMINANT => Some(Self::Thread(ThreadId::new_unchecked(data))),
+            #[expect(clippy::cast_possible_wrap)]
+            Self::FILE_DISCRIMINANT => {
+                // This cast preserves all bits.
+                assert_eq!(size_of_val(&data), size_of::<FdNum>());
+                Some(Self::File(data as FdNum))
+            }
+            Self::INVALID_DISCRIMINANT => Some(Self::Invalid),
             _ => None,
         }
     }
@@ -139,7 +165,7 @@ impl Handle {
     /// Structurally invalid handles return [`HandleError::InvalidHandle`].
     /// If the handle is structurally valid but semantically invalid, e.g. a for non-existent thread
     /// ID, returns [`HandleError::ThreadNotFound`].
-    pub fn try_from_scalar<'tcx>(
+    fn try_from_scalar<'tcx>(
         handle: Scalar,
         cx: &MiriInterpCx<'tcx>,
     ) -> InterpResult<'tcx, Result<Self, HandleError>> {
@@ -171,6 +197,27 @@ impl<'tcx> EvalContextExt<'tcx> for crate::MiriInterpCx<'tcx> {}
 
 #[allow(non_snake_case)]
 pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
+    /// Convert a scalar into a structured `Handle`.
+    /// If the handle is invalid, or references a non-existent item, execution is aborted.
+    #[track_caller]
+    fn read_handle(&self, handle: &OpTy<'tcx>, function_name: &str) -> InterpResult<'tcx, Handle> {
+        let this = self.eval_context_ref();
+        let handle = this.read_scalar(handle)?;
+        match Handle::try_from_scalar(handle, this)? {
+            Ok(handle) => interp_ok(handle),
+            Err(HandleError::InvalidHandle) =>
+                throw_machine_stop!(TerminationInfo::Abort(format!(
+                    "invalid handle {} passed to {function_name}",
+                    handle.to_target_isize(this)?,
+                ))),
+            Err(HandleError::ThreadNotFound(_)) =>
+                throw_machine_stop!(TerminationInfo::Abort(format!(
+                    "invalid thread ID {} passed to {function_name}",
+                    handle.to_target_isize(this)?,
+                ))),
+        }
+    }
+
     fn invalid_handle(&mut self, function_name: &str) -> InterpResult<'tcx, !> {
         throw_machine_stop!(TerminationInfo::Abort(format!(
             "invalid handle passed to `{function_name}`"
@@ -180,15 +227,38 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
     fn CloseHandle(&mut self, handle_op: &OpTy<'tcx>) -> InterpResult<'tcx, Scalar> {
         let this = self.eval_context_mut();
 
-        let handle = this.read_scalar(handle_op)?;
-        let ret = match Handle::try_from_scalar(handle, this)? {
-            Ok(Handle::Thread(thread)) => {
+        let handle = this.read_handle(handle_op, "CloseHandle")?;
+        let ret = match handle {
+            Handle::Thread(thread) => {
                 this.detach_thread(thread, /*allow_terminated_joined*/ true)?;
                 this.eval_windows("c", "TRUE")
             }
+            Handle::File(fd_num) =>
+                if let Some(fd) = this.machine.fds.remove(fd_num) {
+                    let err = fd.close_ref(this.machine.communicate(), this)?;
+                    if let Err(e) = err {
+                        this.set_last_error(e)?;
+                        this.eval_windows("c", "FALSE")
+                    } else {
+                        this.eval_windows("c", "TRUE")
+                    }
+                } else {
+                    this.invalid_handle("CloseHandle")?
+                },
             _ => this.invalid_handle("CloseHandle")?,
         };
 
         interp_ok(ret)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_invalid_encoding() {
+        // Ensure the invalid handle encodes to `u32::MAX`/`INVALID_HANDLE_VALUE`.
+        assert_eq!(Handle::Invalid.to_packed(), u32::MAX)
+    }
+}

src/tools/miri/src/shims/windows/mod.rs

@@ -1,12 +1,14 @@
 pub mod foreign_items;
 
 mod env;
+mod fs;
 mod handle;
 mod sync;
 mod thread;
 
 // All the Windows-specific extension traits
 pub use self::env::{EvalContextExt as _, WindowsEnvVars};
+pub use self::fs::EvalContextExt as _;
 pub use self::handle::EvalContextExt as _;
 pub use self::sync::EvalContextExt as _;
 pub use self::thread::EvalContextExt as _;

src/tools/miri/src/shims/windows/thread.rs

@@ -62,14 +62,14 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
     ) -> InterpResult<'tcx, Scalar> {
         let this = self.eval_context_mut();
 
-        let handle = this.read_scalar(handle_op)?;
+        let handle = this.read_handle(handle_op, "WaitForSingleObject")?;
         let timeout = this.read_scalar(timeout_op)?.to_u32()?;
 
-        let thread = match Handle::try_from_scalar(handle, this)? {
-            Ok(Handle::Thread(thread)) => thread,
+        let thread = match handle {
+            Handle::Thread(thread) => thread,
             // Unlike on posix, the outcome of joining the current thread is not documented.
             // On current Windows, it just deadlocks.
-            Ok(Handle::Pseudo(PseudoHandle::CurrentThread)) => this.active_thread(),
+            Handle::Pseudo(PseudoHandle::CurrentThread) => this.active_thread(),
             _ => this.invalid_handle("WaitForSingleObject")?,
         };
 

src/tools/miri/test_dependencies/Cargo.toml

@@ -25,6 +25,6 @@ page_size = "0.6"
 tokio = { version = "1", features = ["macros", "rt-multi-thread", "time", "net", "fs", "sync", "signal", "io-util"] }
 
 [target.'cfg(windows)'.dependencies]
-windows-sys = { version = "0.59", features = [ "Win32_Foundation", "Win32_System_Threading" ] }
+windows-sys = { version = "0.59", features = ["Win32_Foundation", "Win32_System_Threading", "Win32_Storage_FileSystem", "Win32_Security"] }
 
 [workspace]

src/tools/miri/tests/fail-dep/concurrency/windows_join_main.rs

@@ -13,7 +13,7 @@ use windows_sys::Win32::System::Threading::{INFINITE, WaitForSingleObject};
 // XXX HACK: This is how miri represents the handle for thread 0.
 // This value can be "legitimately" obtained by using `GetCurrentThread` with `DuplicateHandle`
 // but miri does not implement `DuplicateHandle` yet.
-const MAIN_THREAD: HANDLE = (2i32 << 30) as HANDLE;
+const MAIN_THREAD: HANDLE = (2i32 << 29) as HANDLE;
 
 fn main() {
     thread::spawn(|| {

src/tools/miri/tests/pass-dep/concurrency/freebsd-futex.rs

@@ -0,0 +1,260 @@
+//@only-target: freebsd
+//@compile-flags: -Zmiri-preemption-rate=0 -Zmiri-disable-isolation
+
+use std::mem::{self, MaybeUninit};
+use std::ptr::{self, addr_of};
+use std::sync::atomic::AtomicU32;
+use std::time::Instant;
+use std::{io, thread};
+
+fn wait_wake() {
+    fn wake_nobody() {
+        // Current thread waits on futex.
+        // New thread wakes up 0 threads waiting on that futex.
+        // Current thread should time out.
+        static mut FUTEX: u32 = 0;
+
+        let waker = thread::spawn(|| {
+            unsafe {
+                assert_eq!(
+                    libc::_umtx_op(
+                        addr_of!(FUTEX) as *mut _,
+                        libc::UMTX_OP_WAKE_PRIVATE,
+                        0, // wake up 0 waiters
+                        ptr::null_mut::<libc::c_void>(),
+                        ptr::null_mut::<libc::c_void>(),
+                    ),
+                    0
+                );
+            }
+        });
+
+        // 10ms should be enough.
+        let mut timeout = libc::timespec { tv_sec: 0, tv_nsec: 10_000_000 };
+        let timeout_size_arg =
+            ptr::without_provenance_mut::<libc::c_void>(mem::size_of::<libc::timespec>());
+        unsafe {
+            assert_eq!(
+                libc::_umtx_op(
+                    addr_of!(FUTEX) as *mut _,
+                    libc::UMTX_OP_WAIT_UINT_PRIVATE,
+                    0,
+                    timeout_size_arg,
+                    &mut timeout as *mut _ as _,
+                ),
+                -1
+            );
+            // Main thread did not get woken up, so it timed out.
+            assert_eq!(io::Error::last_os_error().raw_os_error().unwrap(), libc::ETIMEDOUT);
+        }
+
+        waker.join().unwrap();
+    }
+
+    fn wake_two_of_three() {
+        // We create 2 threads that wait on a futex with a 100ms timeout.
+        // The main thread wakes up 2 threads waiting on this futex and after this
+        // checks that only those threads woke up and the other one timed out.
+        static mut FUTEX: u32 = 0;
+
+        fn waiter() -> bool {
+            let mut timeout = libc::timespec { tv_sec: 0, tv_nsec: 100_000_000 };
+            let timeout_size_arg =
+                ptr::without_provenance_mut::<libc::c_void>(mem::size_of::<libc::timespec>());
+            unsafe {
+                libc::_umtx_op(
+                    addr_of!(FUTEX) as *mut _,
+                    libc::UMTX_OP_WAIT_UINT_PRIVATE,
+                    0, // FUTEX is 0
+                    timeout_size_arg,
+                    &mut timeout as *mut _ as _,
+                );
+                // Return true if this thread woke up.
+                io::Error::last_os_error().raw_os_error().unwrap() != libc::ETIMEDOUT
+            }
+        }
+
+        let t1 = thread::spawn(waiter);
+        let t2 = thread::spawn(waiter);
+        let t3 = thread::spawn(waiter);
+
+        // Run all the waiters, so they can go to sleep.
+        thread::yield_now();
+
+        // Wake up 2 thread and make sure 1 is still waiting.
+        unsafe {
+            assert_eq!(
+                libc::_umtx_op(
+                    addr_of!(FUTEX) as *mut _,
+                    libc::UMTX_OP_WAKE_PRIVATE,
+                    2,
+                    ptr::null_mut::<libc::c_void>(),
+                    ptr::null_mut::<libc::c_void>(),
+                ),
+                0
+            );
+        }
+
+        // Treat the booleans as numbers to simplify checking how many threads were woken up.
+        let t1 = t1.join().unwrap() as usize;
+        let t2 = t2.join().unwrap() as usize;
+        let t3 = t3.join().unwrap() as usize;
+        let woken_up_count = t1 + t2 + t3;
+        assert!(woken_up_count == 2, "Expected 2 threads to wake up got: {woken_up_count}");
+    }
+
+    wake_nobody();
+    wake_two_of_three();
+}
+
+fn wake_dangling() {
+    let futex = Box::new(0);
+    let ptr: *const u32 = &*futex;
+    drop(futex);
+
+    // Expect error since this is now "unmapped" memory.
+    unsafe {
+        assert_eq!(
+            libc::_umtx_op(
+                ptr as *const AtomicU32 as *mut _,
+                libc::UMTX_OP_WAKE_PRIVATE,
+                0,
+                ptr::null_mut::<libc::c_void>(),
+                ptr::null_mut::<libc::c_void>(),
+            ),
+            -1
+        );
+        assert_eq!(io::Error::last_os_error().raw_os_error().unwrap(), libc::EFAULT);
+    }
+}
+
+fn wait_wrong_val() {
+    let futex: u32 = 123;
+
+    // Wait with a wrong value just returns 0
+    unsafe {
+        assert_eq!(
+            libc::_umtx_op(
+                ptr::from_ref(&futex).cast_mut().cast(),
+                libc::UMTX_OP_WAIT_UINT_PRIVATE,
+                456,
+                ptr::null_mut::<libc::c_void>(),
+                ptr::null_mut::<libc::c_void>(),
+            ),
+            0
+        );
+    }
+}
+
+fn wait_relative_timeout() {
+    fn without_timespec() {
+        let start = Instant::now();
+
+        let futex: u32 = 123;
+
+        let mut timeout = libc::timespec { tv_sec: 0, tv_nsec: 200_000_000 };
+        let timeout_size_arg =
+            ptr::without_provenance_mut::<libc::c_void>(mem::size_of::<libc::timespec>());
+        // Wait for 200ms, with nobody waking us up early
+        unsafe {
+            assert_eq!(
+                libc::_umtx_op(
+                    ptr::from_ref(&futex).cast_mut().cast(),
+                    libc::UMTX_OP_WAIT_UINT_PRIVATE,
+                    123,
+                    timeout_size_arg,
+                    &mut timeout as *mut _ as _,
+                ),
+                -1
+            );
+            assert_eq!(io::Error::last_os_error().raw_os_error().unwrap(), libc::ETIMEDOUT);
+        }
+
+        assert!((200..1000).contains(&start.elapsed().as_millis()));
+    }
+
+    fn with_timespec() {
+        let futex: u32 = 123;
+        let mut timeout = libc::_umtx_time {
+            _timeout: libc::timespec { tv_sec: 0, tv_nsec: 200_000_000 },
+            _flags: 0,
+            _clockid: libc::CLOCK_MONOTONIC as u32,
+        };
+        let timeout_size_arg =
+            ptr::without_provenance_mut::<libc::c_void>(mem::size_of::<libc::_umtx_time>());
+
+        let start = Instant::now();
+
+        // Wait for 200ms, with nobody waking us up early
+        unsafe {
+            assert_eq!(
+                libc::_umtx_op(
+                    ptr::from_ref(&futex).cast_mut().cast(),
+                    libc::UMTX_OP_WAIT_UINT_PRIVATE,
+                    123,
+                    timeout_size_arg,
+                    &mut timeout as *mut _ as _,
+                ),
+                -1
+            );
+            assert_eq!(io::Error::last_os_error().raw_os_error().unwrap(), libc::ETIMEDOUT);
+        }
+        assert!((200..1000).contains(&start.elapsed().as_millis()));
+    }
+
+    without_timespec();
+    with_timespec();
+}
+
+fn wait_absolute_timeout() {
+    let start = Instant::now();
+
+    // Get the current monotonic timestamp as timespec.
+    let mut timeout = unsafe {
+        let mut now: MaybeUninit<libc::timespec> = MaybeUninit::uninit();
+        assert_eq!(libc::clock_gettime(libc::CLOCK_MONOTONIC, now.as_mut_ptr()), 0);
+        now.assume_init()
+    };
+
+    // Add 200ms.
+    timeout.tv_nsec += 200_000_000;
+    if timeout.tv_nsec > 1_000_000_000 {
+        timeout.tv_nsec -= 1_000_000_000;
+        timeout.tv_sec += 1;
+    }
+
+    // Create umtx_timeout struct with that absolute timeout.
+    let umtx_timeout = libc::_umtx_time {
+        _timeout: timeout,
+        _flags: libc::UMTX_ABSTIME,
+        _clockid: libc::CLOCK_MONOTONIC as u32,
+    };
+    let umtx_timeout_ptr = &umtx_timeout as *const _;
+    let umtx_timeout_size = ptr::without_provenance_mut(mem::size_of_val(&umtx_timeout));
+
+    let futex: u32 = 123;
+
+    // Wait for 200ms from now, with nobody waking us up early.
+    unsafe {
+        assert_eq!(
+            libc::_umtx_op(
+                ptr::from_ref(&futex).cast_mut().cast(),
+                libc::UMTX_OP_WAIT_UINT_PRIVATE,
+                123,
+                umtx_timeout_size,
+                umtx_timeout_ptr as *mut _,
+            ),
+            -1
+        );
+        assert_eq!(io::Error::last_os_error().raw_os_error().unwrap(), libc::ETIMEDOUT);
+    }
+    assert!((200..1000).contains(&start.elapsed().as_millis()));
+}
+
+fn main() {
+    wait_wake();
+    wake_dangling();
+    wait_wrong_val();
+    wait_relative_timeout();
+    wait_absolute_timeout();
+}

src/tools/miri/tests/pass-dep/shims/windows-fs.rs

@@ -0,0 +1,198 @@
+//@only-target: windows # this directly tests windows-only functions
+//@compile-flags: -Zmiri-disable-isolation
+#![allow(nonstandard_style)]
+
+use std::os::windows::ffi::OsStrExt;
+use std::path::Path;
+use std::ptr;
+
+#[path = "../../utils/mod.rs"]
+mod utils;
+
+use windows_sys::Win32::Foundation::{
+    CloseHandle, ERROR_ALREADY_EXISTS, GENERIC_READ, GENERIC_WRITE, GetLastError,
+};
+use windows_sys::Win32::Storage::FileSystem::{
+    BY_HANDLE_FILE_INFORMATION, CREATE_ALWAYS, CREATE_NEW, CreateFileW, FILE_ATTRIBUTE_DIRECTORY,
+    FILE_ATTRIBUTE_NORMAL, FILE_FLAG_BACKUP_SEMANTICS, FILE_FLAG_OPEN_REPARSE_POINT,
+    FILE_SHARE_DELETE, FILE_SHARE_READ, FILE_SHARE_WRITE, GetFileInformationByHandle, OPEN_ALWAYS,
+    OPEN_EXISTING,
+};
+
+fn main() {
+    unsafe {
+        test_create_dir_file();
+        test_create_normal_file();
+        test_create_always_twice();
+        test_open_always_twice();
+        test_open_dir_reparse();
+    }
+}
+
+unsafe fn test_create_dir_file() {
+    let temp = utils::tmp();
+    let raw_path = to_wide_cstr(&temp);
+    // Open the `temp` directory.
+    let handle = CreateFileW(
+        raw_path.as_ptr(),
+        GENERIC_READ,
+        FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE,
+        ptr::null_mut(),
+        OPEN_EXISTING,
+        FILE_FLAG_BACKUP_SEMANTICS,
+        ptr::null_mut(),
+    );
+    assert_ne!(handle.addr(), usize::MAX, "CreateFileW Failed: {}", GetLastError());
+    let mut info = std::mem::zeroed::<BY_HANDLE_FILE_INFORMATION>();
+    if GetFileInformationByHandle(handle, &mut info) == 0 {
+        panic!("Failed to get file information")
+    };
+    assert!(info.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY != 0);
+    if CloseHandle(handle) == 0 {
+        panic!("Failed to close file")
+    };
+}
+
+unsafe fn test_create_normal_file() {
+    let temp = utils::tmp().join("test.txt");
+    let raw_path = to_wide_cstr(&temp);
+    let handle = CreateFileW(
+        raw_path.as_ptr(),
+        GENERIC_READ | GENERIC_WRITE,
+        FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE,
+        ptr::null_mut(),
+        CREATE_NEW,
+        0,
+        ptr::null_mut(),
+    );
+    assert_ne!(handle.addr(), usize::MAX, "CreateFileW Failed: {}", GetLastError());
+    let mut info = std::mem::zeroed::<BY_HANDLE_FILE_INFORMATION>();
+    if GetFileInformationByHandle(handle, &mut info) == 0 {
+        panic!("Failed to get file information: {}", GetLastError())
+    };
+    assert!(info.dwFileAttributes & FILE_ATTRIBUTE_NORMAL != 0);
+    if CloseHandle(handle) == 0 {
+        panic!("Failed to close file")
+    };
+
+    // Test metadata-only handle
+    let handle = CreateFileW(
+        raw_path.as_ptr(),
+        0,
+        FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE,
+        ptr::null_mut(),
+        OPEN_EXISTING,
+        0,
+        ptr::null_mut(),
+    );
+    assert_ne!(handle.addr(), usize::MAX, "CreateFileW Failed: {}", GetLastError());
+    let mut info = std::mem::zeroed::<BY_HANDLE_FILE_INFORMATION>();
+    if GetFileInformationByHandle(handle, &mut info) == 0 {
+        panic!("Failed to get file information: {}", GetLastError())
+    };
+    assert!(info.dwFileAttributes & FILE_ATTRIBUTE_NORMAL != 0);
+    if CloseHandle(handle) == 0 {
+        panic!("Failed to close file")
+    };
+}
+
+/// Tests that CREATE_ALWAYS sets the error value correctly based on whether the file already exists
+unsafe fn test_create_always_twice() {
+    let temp = utils::tmp().join("test_create_always.txt");
+    let raw_path = to_wide_cstr(&temp);
+    let handle = CreateFileW(
+        raw_path.as_ptr(),
+        GENERIC_READ | GENERIC_WRITE,
+        FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE,
+        ptr::null_mut(),
+        CREATE_ALWAYS,
+        0,
+        ptr::null_mut(),
+    );
+    assert_ne!(handle.addr(), usize::MAX, "CreateFileW Failed: {}", GetLastError());
+    assert_eq!(GetLastError(), 0);
+    if CloseHandle(handle) == 0 {
+        panic!("Failed to close file")
+    };
+
+    let handle = CreateFileW(
+        raw_path.as_ptr(),
+        GENERIC_READ | GENERIC_WRITE,
+        FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE,
+        ptr::null_mut(),
+        CREATE_ALWAYS,
+        0,
+        ptr::null_mut(),
+    );
+    assert_ne!(handle.addr(), usize::MAX, "CreateFileW Failed: {}", GetLastError());
+    assert_eq!(GetLastError(), ERROR_ALREADY_EXISTS);
+    if CloseHandle(handle) == 0 {
+        panic!("Failed to close file")
+    };
+}
+
+/// Tests that OPEN_ALWAYS sets the error value correctly based on whether the file already exists
+unsafe fn test_open_always_twice() {
+    let temp = utils::tmp().join("test_open_always.txt");
+    let raw_path = to_wide_cstr(&temp);
+    let handle = CreateFileW(
+        raw_path.as_ptr(),
+        GENERIC_READ | GENERIC_WRITE,
+        FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE,
+        ptr::null_mut(),
+        OPEN_ALWAYS,
+        0,
+        ptr::null_mut(),
+    );
+    assert_ne!(handle.addr(), usize::MAX, "CreateFileW Failed: {}", GetLastError());
+    assert_eq!(GetLastError(), 0);
+    if CloseHandle(handle) == 0 {
+        panic!("Failed to close file")
+    };
+
+    let handle = CreateFileW(
+        raw_path.as_ptr(),
+        GENERIC_READ | GENERIC_WRITE,
+        FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE,
+        ptr::null_mut(),
+        OPEN_ALWAYS,
+        0,
+        ptr::null_mut(),
+    );
+    assert_ne!(handle.addr(), usize::MAX, "CreateFileW Failed: {}", GetLastError());
+    assert_eq!(GetLastError(), ERROR_ALREADY_EXISTS);
+    if CloseHandle(handle) == 0 {
+        panic!("Failed to close file")
+    };
+}
+
+// TODO: Once we support more of the std API, it would be nice to test against an actual symlink
+unsafe fn test_open_dir_reparse() {
+    let temp = utils::tmp();
+    let raw_path = to_wide_cstr(&temp);
+    // Open the `temp` directory.
+    let handle = CreateFileW(
+        raw_path.as_ptr(),
+        GENERIC_READ,
+        FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE,
+        ptr::null_mut(),
+        OPEN_EXISTING,
+        FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OPEN_REPARSE_POINT,
+        ptr::null_mut(),
+    );
+    assert_ne!(handle.addr(), usize::MAX, "CreateFileW Failed: {}", GetLastError());
+    let mut info = std::mem::zeroed::<BY_HANDLE_FILE_INFORMATION>();
+    if GetFileInformationByHandle(handle, &mut info) == 0 {
+        panic!("Failed to get file information")
+    };
+    assert!(info.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY != 0);
+    if CloseHandle(handle) == 0 {
+        panic!("Failed to close file")
+    };
+}
+
+fn to_wide_cstr(path: &Path) -> Vec<u16> {
+    let mut raw_path = path.as_os_str().encode_wide().collect::<Vec<_>>();
+    raw_path.extend([0, 0]);
+    raw_path
+}

src/tools/miri/tests/pass/path.rs

@@ -6,7 +6,11 @@ mod utils;
 
 #[track_caller]
 fn assert_absolute_eq(in_: &str, out: &str) {
-    assert_eq!(absolute(in_).unwrap().as_os_str(), Path::new(out).as_os_str());
+    assert_eq!(
+        absolute(in_).unwrap().as_os_str(),
+        Path::new(out).as_os_str(),
+        "incorrect absolute path for {in_:?}"
+    );
 }
 
 fn test_absolute() {
@@ -29,11 +33,28 @@ fn test_absolute() {
         assert_absolute_eq(r"\\?\C:\path\to\file", r"\\?\C:\path\to\file");
         assert_absolute_eq(r"\\?\UNC\server\share\to\file", r"\\?\UNC\server\share\to\file");
         assert_absolute_eq(r"\\?\PIPE\name", r"\\?\PIPE\name");
+        assert_absolute_eq(r"\\server\share\NUL", r"\\server\share\NUL");
+        // This fails on Windows 10 hosts. FIXME: enable this once GHA runners are on Windows 11.
+        //assert_absolute_eq(r"C:\path\to\COM1", r"C:\path\to\COM1");
         // Verbatim paths are always unchanged, no matter what.
         assert_absolute_eq(r"\\?\path.\to/file..", r"\\?\path.\to/file..");
-
+        // Trailing dot is removed here.
         assert_absolute_eq(r"C:\path..\to.\file.", r"C:\path..\to\file");
+        // `..` is resolved here.
+        assert_absolute_eq(r"C:\path\to\..\file", r"C:\path\file");
+        assert_absolute_eq(r"C:\path\to\..\..\file", r"C:\file");
+        assert_absolute_eq(r"C:\path\to\..\..\..\..\..\..\file", r"C:\file");
+        assert_absolute_eq(r"C:\..", r"C:\");
+        assert_absolute_eq(r"\\server\share\to\path\with\..\file", r"\\server\share\to\path\file");
+        assert_absolute_eq(r"\\server\share\to\..\..\..\..\file", r"\\server\share\file");
+        assert_absolute_eq(r"\\server\share\..", r"\\server\share");
+        // Magic filenames.
+        assert_absolute_eq(r"NUL", r"\\.\NUL");
+        assert_absolute_eq(r"nul", r"\\.\nul");
         assert_absolute_eq(r"COM1", r"\\.\COM1");
+        assert_absolute_eq(r"com1", r"\\.\com1");
+        assert_absolute_eq(r"C:\path\to\NUL", r"\\.\NUL");
+        assert_absolute_eq(r"C:\path\to\nul", r"\\.\nul");
     } else {
         panic!("unsupported OS");
     }

src/tools/miri/tests/pass/shims/fs.rs

@@ -1,4 +1,3 @@
-//@ignore-target: windows # File handling is not implemented yet
 //@compile-flags: -Zmiri-disable-isolation
 
 #![feature(io_error_more)]
@@ -18,20 +17,23 @@ mod utils;
 
 fn main() {
     test_path_conversion();
-    test_file();
-    test_file_clone();
-    test_file_create_new();
-    test_seek();
-    test_metadata();
-    test_file_set_len();
-    test_file_sync();
-    test_errors();
-    test_rename();
-    test_directory();
-    test_canonicalize();
-    test_from_raw_os_error();
-    #[cfg(unix)]
-    test_pread_pwrite();
+    // Windows file handling is very incomplete.
+    if cfg!(not(windows)) {
+        test_file();
+        test_file_create_new();
+        test_seek();
+        test_file_clone();
+        test_metadata();
+        test_file_set_len();
+        test_file_sync();
+        test_errors();
+        test_rename();
+        test_directory();
+        test_canonicalize();
+        test_from_raw_os_error();
+        #[cfg(unix)]
+        test_pread_pwrite();
+    }
 }
 
 fn test_path_conversion() {
@@ -144,10 +146,10 @@ fn test_metadata() {
     let path = utils::prepare_with_content("miri_test_fs_metadata.txt", bytes);
 
     // Test that metadata of an absolute path is correct.
-    check_metadata(bytes, &path).unwrap();
+    check_metadata(bytes, &path).expect("absolute path metadata");
     // Test that metadata of a relative path is correct.
     std::env::set_current_dir(path.parent().unwrap()).unwrap();
-    check_metadata(bytes, Path::new(path.file_name().unwrap())).unwrap();
+    check_metadata(bytes, Path::new(path.file_name().unwrap())).expect("relative path metadata");
 
     // Removing file should succeed.
     remove_file(&path).unwrap();

src/tools/miri/triagebot.toml

@@ -40,3 +40,9 @@ unless = ["S-blocked", "S-waiting-on-team", "S-waiting-on-review"]
 
 # Automatically close and reopen PRs made by bots to run CI on them
 [bot-pull-requests]
+
+# Canonicalize issue numbers to avoid closing the wrong issue when upstreaming this subtree
+[canonicalize-issue-links]
+
+# Prevents mentions in commits to avoid users being spammed
+[no-mentions]