fix(fspy): unify shared memory on a sparse temp file across all platforms

CHANGELOG.md

@@ -1,5 +1,6 @@
 # Changelog
 
+- **Fixed** Automatic file-access tracking now backs its shared memory with a sparse temporary file on every platform, so tasks are still tracked inside coding-agent sandboxes that deny POSIX shared memory and Unix domain sockets ([#563](https://github.com/voidzero-dev/vite-task/issues/563), [#576](https://github.com/voidzero-dev/vite-task/pull/576)).
 - **Added** Tasks now run with `VP_RUN=1` set, so tools can tell they are running under `vp run` instead of being invoked directly ([#570](https://github.com/voidzero-dev/vite-task/pull/570)).
 - **Fixed** The task cache now supports much larger automatically tracked input sets without hitting wincode's default 4 MiB sequence preallocation limit ([#554](https://github.com/voidzero-dev/vite-task/pull/554)).
 - **Fixed** npm workspace patterns beginning with `./` now discover matching packages correctly ([vite-plus#2201](https://github.com/voidzero-dev/vite-plus/issues/2201), [#547](https://github.com/voidzero-dev/vite-task/pull/547)).

Cargo.toml

@@ -89,7 +89,6 @@ jsonc-parser = { version = "0.32.0", features = ["serde"] }
 libc = "0.2.185"
 libtest-mimic = "0.8.2"
 memmap2 = "0.9.11"
-memfd = "0.6.5"
 monostate = "1.0.2"
 napi = "3"
 napi-build = "2"

crates/fspy_shared/src/ipc/channel/mod.rs

@@ -2,55 +2,22 @@
 
 mod shm_io;
 
-use std::{env::temp_dir, fs::File, io, mem::MaybeUninit, ops::Deref, path::PathBuf, sync::Arc};
+use std::{env::temp_dir, fs::File, io, ops::Deref, path::PathBuf};
 
-use fspy_shm::Shm;
+use fspy_shm::{Mapping, ShmKeeper};
 pub use shm_io::FrameMut;
 use shm_io::{ShmReader, ShmWriter};
 use tracing::debug;
 use uuid::Uuid;
-use wincode::{
-    SchemaRead, SchemaWrite,
-    config::Config,
-    error::{ReadResult, WriteResult},
-    io::{Reader, Writer},
-};
+use wincode::{SchemaRead, SchemaWrite};
 
 use super::NativeStr;
 
-/// wincode schema adapter for `Arc<str>`, which is a foreign type with unsized inner.
-pub(crate) struct ArcStrSchema;
-
-// SAFETY: Delegates to `str`'s SchemaWrite impl, preserving its size/write invariants.
-unsafe impl<C: Config> SchemaWrite<C> for ArcStrSchema {
-    type Src = Arc<str>;
-
-    fn size_of(src: &Self::Src) -> WriteResult<usize> {
-        <str as SchemaWrite<C>>::size_of(src)
-    }
-
-    fn write(writer: impl Writer, src: &Self::Src) -> WriteResult<()> {
-        <str as SchemaWrite<C>>::write(writer, src)
-    }
-}
-
-// SAFETY: Delegates to `&str`'s SchemaRead impl; dst is initialized on Ok.
-unsafe impl<'de, C: Config> SchemaRead<'de, C> for ArcStrSchema {
-    type Dst = Arc<str>;
-
-    fn read(mut reader: impl Reader<'de>, dst: &mut MaybeUninit<Self::Dst>) -> ReadResult<()> {
-        let s: &str = <&str as SchemaRead<'de, C>>::get(&mut reader)?;
-        dst.write(Arc::from(s));
-        Ok(())
-    }
-}
-
 /// Serializable configuration to create channel senders.
 #[derive(SchemaWrite, SchemaRead, Clone, Debug)]
 pub struct ChannelConf {
     lock_file_path: Box<NativeStr>,
-    #[wincode(with = "ArcStrSchema")]
-    shm_id: Arc<str>,
+    shm_id: Box<NativeStr>,
 }
 
 /// Creates a mpsc IPC channel with one receiver and a `ChannelConf` that can be passed around processes and used to create multiple senders
@@ -62,12 +29,16 @@ pub fn channel(capacity: usize) -> io::Result<(ChannelConf, Receiver)> {
     // Initialize the lock file with a unique name.
     let lock_file_path = temp_dir().join(format!("fspy_ipc_{}.lock", Uuid::new_v4()));
 
-    let shm = fspy_shm::create(capacity)?;
+    let keeper = fspy_shm::create(capacity)?;
+    // The creating process has no privileged view; it opens one like any other.
+    let mapping = fspy_shm::open(keeper.id())?;
 
-    let conf =
-        ChannelConf { lock_file_path: lock_file_path.as_os_str().into(), shm_id: shm.id().into() };
+    let conf = ChannelConf {
+        lock_file_path: lock_file_path.as_os_str().into(),
+        shm_id: keeper.id().into(),
+    };
 
-    let receiver = Receiver::new(lock_file_path, shm)?;
+    let receiver = Receiver::new(lock_file_path, keeper, mapping)?;
     Ok((conf, receiver))
 }
 
@@ -83,7 +54,7 @@ impl ChannelConf {
         let lock_file = File::open(self.lock_file_path.to_cow_os_str())?;
         lock_file.try_lock_shared()?;
 
-        let shm = fspy_shm::open(&self.shm_id)?;
+        let shm = fspy_shm::open(&self.shm_id.to_cow_os_str())?;
         // SAFETY: `shm` is a freshly opened shared memory region with valid pointer and size.
         // Exclusive write access is ensured by the shared file lock held by this sender.
         let writer = unsafe { ShmWriter::new(shm) };
@@ -92,7 +63,7 @@ impl ChannelConf {
 }
 
 pub struct Sender {
-    writer: ShmWriter<Shm>,
+    writer: ShmWriter<Mapping>,
     lock_file_path: Box<NativeStr>,
     lock_file: File,
 }
@@ -106,20 +77,13 @@ impl Drop for Sender {
 }
 
 impl Deref for Sender {
-    type Target = ShmWriter<Shm>;
+    type Target = ShmWriter<Mapping>;
 
     fn deref(&self) -> &Self::Target {
         &self.writer
     }
 }
 
-#[cfg_attr(
-    target_os = "windows",
-    expect(
-        clippy::non_send_fields_in_send_ty,
-        reason = "`Sender` holds a shared file lock that ensures there's no reader, so `shm` can be safely written to"
-    )
-)]
 /// SAFETY: `Sender` holds a shared file lock that ensures there's no reader, so `shm` can be safely written to.
 unsafe impl Send for Sender {}
 
@@ -131,16 +95,11 @@ unsafe impl Sync for Sender {}
 pub struct Receiver {
     lock_file_path: PathBuf,
     lock_file: File,
-    shm: Shm,
+    /// Keeps the backing file's name alive for as long as senders may attach.
+    _keeper: ShmKeeper,
+    mapping: Mapping,
 }
 
-#[cfg_attr(
-    target_os = "windows",
-    expect(
-        clippy::non_send_fields_in_send_ty,
-        reason = "Receiver doesn't read or write `shm`. It only passes it to `ReceiverLockGuard` under the lock"
-    )
-)]
 /// SAFETY: `Receiver` doesn't read or write `shm`. It only passes it to `ReceiverLockGuard` under the lock.
 unsafe impl Send for Receiver {}
 
@@ -156,9 +115,9 @@ impl Drop for Receiver {
 }
 
 impl Receiver {
-    fn new(lock_file_path: PathBuf, shm: Shm) -> io::Result<Self> {
+    fn new(lock_file_path: PathBuf, keeper: ShmKeeper, mapping: Mapping) -> io::Result<Self> {
         let lock_file = File::create(&lock_file_path)?;
-        Ok(Self { lock_file_path, lock_file, shm })
+        Ok(Self { lock_file_path, lock_file, _keeper: keeper, mapping })
     }
 
     /// Lock the shared memory for unique read access.
@@ -172,7 +131,7 @@ impl Receiver {
         self.lock_file.lock()?;
         // SAFETY: The exclusive file lock is held, so no writers can access the shared memory.
         // The lock ensures all prior writes are visible to this thread.
-        let reader = ShmReader::new(unsafe { self.shm.as_slice() });
+        let reader = ShmReader::new(unsafe { self.mapping.as_slice() });
         Ok(ReceiverLockGuard { reader, lock_file: &self.lock_file })
     }
 }

crates/fspy_shared/src/ipc/channel/shm_io.rs

@@ -9,7 +9,7 @@ use std::{
 };
 
 use bytemuck::must_cast;
-use fspy_shm::Shm;
+use fspy_shm::Mapping;
 use wincode::{SchemaWrite, Serialize as _, config::DefaultConfig};
 
 // `ShmWriter` writes headers using atomic operations to prevent partial writes due to crashes,
@@ -28,7 +28,7 @@ pub trait AsRawSlice {
     fn as_raw_slice(&self) -> *mut [u8];
 }
 
-impl AsRawSlice for Shm {
+impl AsRawSlice for Mapping {
     fn as_raw_slice(&self) -> *mut [u8] {
         slice_from_raw_parts_mut(self.as_ptr(), self.len())
     }
@@ -672,27 +672,15 @@ mod tests {
 
         const SHM_SIZE: usize = 1024 * 1024;
 
-        // On Linux, `fspy_shm::create` spawns the mapping's broker onto the
-        // ambient tokio runtime, which serves the child processes' opens.
-        #[cfg(target_os = "linux")]
-        let runtime = tokio::runtime::Builder::new_multi_thread()
-            .worker_threads(1)
-            .enable_io()
-            .enable_time()
-            .build()
-            .unwrap();
-        #[cfg(target_os = "linux")]
-        let _guard = runtime.enter();
-
-        let shm = fspy_shm::create(SHM_SIZE).unwrap();
-        let shm_name = shm.id().to_owned();
+        let keeper = fspy_shm::create(SHM_SIZE).unwrap();
+        let shm_name = keeper.id().to_str().expect("test temp dir is UTF-8").to_owned();
 
         let children: Vec<Child> = (0..CHILD_COUNT)
             .map(|child_index| {
                 let cmd = command_for_fn!(
                     (shm_name.clone(), child_index),
                     |(shm_name, child_index): (String, usize)| {
-                        let shm = fspy_shm::open(&shm_name).unwrap();
+                        let shm = fspy_shm::open(std::ffi::OsStr::new(&shm_name)).unwrap();
                         // SAFETY: `shm` is a freshly opened shared memory region with a valid
                         // pointer and size. Concurrent write access is safe because `ShmWriter`
                         // uses atomic operations.
@@ -712,9 +700,10 @@ mod tests {
             assert!(status.success());
         }
 
+        let mapping = fspy_shm::open(keeper.id()).unwrap();
         // SAFETY: All child processes have exited (waited above), so no concurrent writers exist.
         // The shared memory is valid and fully written.
-        let shm = unsafe { shm.as_slice() };
+        let shm = unsafe { mapping.as_slice() };
         let reader = ShmReader::new(shm);
         let frames = reader.iter_frames().map(BStr::new).collect::<FxHashSet<&BStr>>();
         assert_eq!(frames.len(), CHILD_COUNT * FRAME_COUNT_EACH_CHILD);

crates/fspy_shm/Cargo.toml

@@ -7,24 +7,13 @@ license.workspace = true
 publish = false
 rust-version.workspace = true
 
-[target.'cfg(target_os = "linux")'.dependencies]
-memmap2 = { workspace = true }
-memfd = { workspace = true }
-passfd = { workspace = true, features = ["async"] }
-nix = { workspace = true, features = ["fs", "socket", "user"] }
-tokio = { workspace = true, features = ["macros", "net", "rt", "time"] }
-tokio-util = { workspace = true }
-tracing = { workspace = true }
+[dependencies]
 uuid = { workspace = true, features = ["v4"] }
 
-[target.'cfg(target_os = "macos")'.dependencies]
-base64 = { workspace = true }
+[target.'cfg(unix)'.dependencies]
 memmap2 = { workspace = true }
-nix = { workspace = true, features = ["fs", "mman"] }
-uuid = { workspace = true, features = ["v4"] }
 
 [target.'cfg(target_os = "windows")'.dependencies]
-uuid = { workspace = true, features = ["v4"] }
 windows-sys = { workspace = true, features = [
   "Win32_Foundation",
   "Win32_Security",
@@ -37,7 +26,6 @@ windows-sys = { workspace = true, features = [
 [dev-dependencies]
 ctor = { workspace = true }
 subprocess_test = { workspace = true }
-tokio = { workspace = true, features = ["macros", "rt-multi-thread"] }
 
 [lints]
 workspace = true