Merge pull request #1855 from ueno/wip/dueno/null

wasi-common: don't rely on platform dependent "NUL" device

crates/wasi-common/src/ctx.rs

@@ -2,7 +2,7 @@ use crate::entry::{Entry, EntryHandle};
 use crate::fdpool::FdPool;
 use crate::handle::Handle;
 use crate::sys::osdir::OsDir;
-use crate::sys::osother::{OsOther, OsOtherExt};
+use crate::sys::stdio::NullDevice;
 use crate::sys::stdio::{Stderr, StderrExt, Stdin, StdinExt, Stdout, StdoutExt};
 use crate::virtfs::{VirtualDir, VirtualDirEntry};
 use crate::wasi::types;
@@ -136,9 +136,9 @@ pub struct WasiCtxBuilder {
 impl WasiCtxBuilder {
     /// Builder for a new `WasiCtx`.
     pub fn new() -> Self {
-        let stdin = Some(PendingEntry::Thunk(OsOther::from_null));
-        let stdout = Some(PendingEntry::Thunk(OsOther::from_null));
-        let stderr = Some(PendingEntry::Thunk(OsOther::from_null));
+        let stdin = Some(PendingEntry::Handle(Box::new(NullDevice::new())));
+        let stdout = Some(PendingEntry::Handle(Box::new(NullDevice::new())));
+        let stderr = Some(PendingEntry::Handle(Box::new(NullDevice::new())));
 
         Self {
             stdin,

crates/wasi-common/src/lib.rs

@@ -39,6 +39,6 @@ pub use ctx::{WasiCtx, WasiCtxBuilder, WasiCtxBuilderError};
 pub use handle::{Handle, HandleRights};
 pub use sys::osdir::OsDir;
 pub use sys::osfile::OsFile;
-pub use sys::osother::{OsOther, OsOtherExt};
+pub use sys::osother::OsOther;
 pub use sys::preopen_dir;
 pub use virtfs::{FileContents, VirtualDirEntry};

crates/wasi-common/src/sys/osother.rs

@@ -10,13 +10,6 @@ use std::fs::File;
 use std::io::{self, Read, Write};
 use std::ops::Deref;
 
-/// Extra methods for `OsOther` that are only available when configured for
-/// some operating systems.
-pub trait OsOtherExt {
-    /// Create `OsOther` as `dyn Handle` from null device.
-    fn from_null() -> io::Result<Box<dyn Handle>>;
-}
-
 /// `OsOther` is something of a catch-all for everything not covered with the specific handle
 /// types (`OsFile`, `OsDir`, `Stdio`). It currently encapsulates handles such as OS pipes,
 /// sockets, streams, etc. As such, when redirecting stdio within `WasiCtxBuilder`, the redirected

crates/wasi-common/src/sys/stdio.rs

@@ -20,9 +20,10 @@ use super::{fd, AsFile};
 use crate::handle::{Handle, HandleRights};
 use crate::sandboxed_tty_writer::SandboxedTTYWriter;
 use crate::wasi::types::{self, Filetype};
-use crate::wasi::Result;
+use crate::wasi::{Errno, Result, RightsExt};
 use std::any::Any;
 use std::cell::Cell;
+use std::convert::TryInto;
 use std::io::{self, Read, Write};
 
 pub(crate) trait StdinExt: Sized {
@@ -174,3 +175,59 @@ impl Handle for Stderr {
         Ok(nwritten)
     }
 }
+
+#[derive(Debug, Clone)]
+pub(crate) struct NullDevice {
+    pub(crate) rights: Cell<HandleRights>,
+    pub(crate) fd_flags: Cell<types::Fdflags>,
+}
+
+impl NullDevice {
+    pub(crate) fn new() -> Self {
+        let rights = HandleRights::new(
+            types::Rights::character_device_base(),
+            types::Rights::character_device_inheriting(),
+        );
+        let rights = Cell::new(rights);
+        let fd_flags = types::Fdflags::empty();
+        let fd_flags = Cell::new(fd_flags);
+        Self { rights, fd_flags }
+    }
+}
+
+impl Handle for NullDevice {
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+    fn try_clone(&self) -> io::Result<Box<dyn Handle>> {
+        Ok(Box::new(self.clone()))
+    }
+    fn get_file_type(&self) -> types::Filetype {
+        types::Filetype::CharacterDevice
+    }
+    fn get_rights(&self) -> HandleRights {
+        self.rights.get()
+    }
+    fn set_rights(&self, rights: HandleRights) {
+        self.rights.set(rights)
+    }
+    // FdOps
+    fn fdstat_get(&self) -> Result<types::Fdflags> {
+        Ok(self.fd_flags.get())
+    }
+    fn fdstat_set_flags(&self, fdflags: types::Fdflags) -> Result<()> {
+        self.fd_flags.set(fdflags);
+        Ok(())
+    }
+    fn read_vectored(&self, _iovs: &mut [io::IoSliceMut]) -> Result<usize> {
+        Ok(0)
+    }
+    fn write_vectored(&self, iovs: &[io::IoSlice]) -> Result<usize> {
+        let mut total_len = 0u32;
+        for iov in iovs {
+            let len: types::Size = iov.len().try_into()?;
+            total_len = total_len.checked_add(len).ok_or(Errno::Overflow)?;
+        }
+        Ok(total_len as usize)
+    }
+}

crates/wasi-common/src/sys/unix/osother.rs

@@ -1,10 +1,9 @@
 use super::oshandle::RawOsHandle;
 use super::{get_file_type, get_rights};
-use crate::handle::Handle;
-use crate::sys::osother::{OsOther, OsOtherExt};
+use crate::sys::osother::OsOther;
 use crate::wasi::types;
 use std::convert::TryFrom;
-use std::fs::{File, OpenOptions};
+use std::fs::File;
 use std::io;
 use std::os::unix::prelude::{FromRawFd, IntoRawFd};
 
@@ -21,14 +20,3 @@ impl TryFrom<File> for OsOther {
         Ok(Self::new(file_type, rights, handle))
     }
 }
-
-impl OsOtherExt for OsOther {
-    fn from_null() -> io::Result<Box<dyn Handle>> {
-        let file = OpenOptions::new()
-            .read(true)
-            .write(true)
-            .open("/dev/null")?;
-        let file = Self::try_from(file)?;
-        Ok(Box::new(file))
-    }
-}

crates/wasi-common/src/sys/windows/osother.rs

@@ -1,10 +1,9 @@
 use super::oshandle::RawOsHandle;
 use super::{get_file_type, get_rights};
-use crate::handle::Handle;
-use crate::sys::osother::{OsOther, OsOtherExt};
+use crate::sys::osother::OsOther;
 use crate::wasi::types;
 use std::convert::TryFrom;
-use std::fs::{File, OpenOptions};
+use std::fs::File;
 use std::io;
 use std::os::windows::prelude::{FromRawHandle, IntoRawHandle};
 
@@ -21,11 +20,3 @@ impl TryFrom<File> for OsOther {
         Ok(Self::new(file_type, rights, handle))
     }
 }
-
-impl OsOtherExt for OsOther {
-    fn from_null() -> io::Result<Box<dyn Handle>> {
-        let file = OpenOptions::new().read(true).write(true).open("NUL")?;
-        let file = Self::try_from(file)?;
-        Ok(Box::new(file))
-    }
-}