Misc yanix fixes (#715)

* Correctly handle possibly misaligned pointers in readdir

This reapplies #615, which was inadvertently reverted.

* Tidy up unneeded `self::` qualifiers.

* Make Dir's contents private.

Also remove the `unsafe` from `impl_iter`. With `Dir`'s field being
private, we can rely on the pointer being only what we've assigned to
it.

* Make `poll`'s timeout argument a `libc::c_int`.

This clarifies that there are no subsequent conversions before calling the
underlying libc API.

* Use clock_gettime instead of clock_getres to get the time.

* Mark FileType::from_raw as safe.

It handles unknown values, so it can be marked safe.

crates/wasi-common/src/host.rs

@@ -63,12 +63,12 @@ impl Dirent {
 
         let sys_dirent = raw.as_mut_ptr() as *mut __wasi_dirent_t;
         unsafe {
-            *sys_dirent = __wasi_dirent_t {
+            sys_dirent.write_unaligned(__wasi_dirent_t {
                 d_namlen: namlen.try_into()?,
                 d_ino: self.ino,
                 d_next: self.cookie,
                 d_type: self.ftype.to_wasi(),
-            };
+            });
         }
 
         let sys_name = unsafe { sys_dirent.offset(1) as *mut u8 };

crates/wasi-common/src/old/snapshot_0/host.rs

@@ -63,12 +63,12 @@ impl Dirent {
 
         let sys_dirent = raw.as_mut_ptr() as *mut __wasi_dirent_t;
         unsafe {
-            *sys_dirent = __wasi_dirent_t {
+            sys_dirent.write_unaligned(__wasi_dirent_t {
                 d_namlen: namlen.try_into()?,
                 d_ino: self.ino,
                 d_next: self.cookie,
                 d_type: self.ftype.to_wasi(),
-            };
+            });
         }
 
         let sys_name = unsafe { sys_dirent.offset(1) as *mut u8 };

crates/wasi-common/src/old/snapshot_0/sys/unix/hostcalls_impl/misc.rs

@@ -3,7 +3,7 @@
 use crate::old::snapshot_0::hostcalls_impl::{ClockEventData, FdEventData};
 use crate::old::snapshot_0::sys::host_impl;
 use crate::old::snapshot_0::{wasi, Error, Result};
-use yanix::clock::{clock_getres, ClockId};
+use yanix::clock::{clock_getres, clock_gettime, ClockId};
 
 fn wasi_clock_id_to_unix(clock_id: wasi::__wasi_clockid_t) -> Result<ClockId> {
     // convert the supported clocks to libc types, or return EINVAL
@@ -39,7 +39,7 @@ pub(crate) fn clock_res_get(clock_id: wasi::__wasi_clockid_t) -> Result<wasi::__
 
 pub(crate) fn clock_time_get(clock_id: wasi::__wasi_clockid_t) -> Result<wasi::__wasi_timestamp_t> {
     let clock_id = wasi_clock_id_to_unix(clock_id)?;
-    let timespec = clock_getres(clock_id)?;
+    let timespec = clock_gettime(clock_id)?;
 
     // convert to nanoseconds, returning EOVERFLOW in case of overflow; this is freelancing a bit
     // from the spec but seems like it'll be an unusual situation to hit

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

@@ -4,16 +4,16 @@ use cfg_if::cfg_if;
 cfg_if! {
     if #[cfg(unix)] {
         mod unix;
-        pub(crate) use self::unix::*;
-        pub use self::unix::preopen_dir;
+        pub(crate) use unix::*;
+        pub use unix::preopen_dir;
 
         pub(crate) fn errno_from_host(err: i32) -> wasi::__wasi_errno_t {
             host_impl::errno_from_nix(yanix::Errno::from_i32(err)).as_wasi_errno()
         }
     } else if #[cfg(windows)] {
         mod windows;
-        pub(crate) use self::windows::*;
-        pub use self::windows::preopen_dir;
+        pub(crate) use windows::*;
+        pub use windows::preopen_dir;
 
         pub(crate) fn errno_from_host(err: i32) -> wasi::__wasi_errno_t {
             host_impl::errno_from_win(winx::winerror::WinError::from_u32(err as u32))

crates/wasi-common/src/sys/unix/hostcalls_impl/misc.rs

@@ -3,7 +3,7 @@
 use crate::hostcalls_impl::{ClockEventData, FdEventData};
 use crate::sys::host_impl;
 use crate::{wasi, Error, Result};
-use yanix::clock::{clock_getres, ClockId};
+use yanix::clock::{clock_getres, clock_gettime, ClockId};
 
 fn wasi_clock_id_to_unix(clock_id: wasi::__wasi_clockid_t) -> Result<ClockId> {
     // convert the supported clocks to libc types, or return EINVAL
@@ -39,7 +39,7 @@ pub(crate) fn clock_res_get(clock_id: wasi::__wasi_clockid_t) -> Result<wasi::__
 
 pub(crate) fn clock_time_get(clock_id: wasi::__wasi_clockid_t) -> Result<wasi::__wasi_timestamp_t> {
     let clock_id = wasi_clock_id_to_unix(clock_id)?;
-    let timespec = clock_getres(clock_id)?;
+    let timespec = clock_gettime(clock_id)?;
 
     // convert to nanoseconds, returning EOVERFLOW in case of overflow; this is freelancing a bit
     // from the spec but seems like it'll be an unusual situation to hit

crates/wasi-common/yanix/src/clock.rs

@@ -27,3 +27,11 @@ pub fn clock_getres(clock_id: ClockId) -> Result<libc::timespec> {
     })?;
     Ok(unsafe { timespec.assume_init() })
 }
+
+pub fn clock_gettime(clock_id: ClockId) -> Result<libc::timespec> {
+    let mut timespec = MaybeUninit::<libc::timespec>::uninit();
+    Errno::from_success_code(unsafe {
+        libc::clock_gettime(clock_id.as_raw(), timespec.as_mut_ptr())
+    })?;
+    Ok(unsafe { timespec.assume_init() })
+}

crates/wasi-common/yanix/src/dir.rs

@@ -8,7 +8,7 @@ use std::{ffi::CStr, ops::Deref, ptr};
 pub use crate::sys::EntryExt;
 
 #[derive(Clone, Debug, Eq, Hash, PartialEq)]
-pub struct Dir(pub(crate) ptr::NonNull<libc::DIR>);
+pub struct Dir(ptr::NonNull<libc::DIR>);
 
 impl Dir {
     /// Takes the ownership of the passed-in descriptor-based object,
@@ -51,6 +51,12 @@ impl Dir {
         let loc = unsafe { libc::telldir(self.0.as_ptr()) };
         SeekLoc(loc)
     }
+
+    /// For use by platform-specific implementation code. Returns the raw
+    /// underlying state.
+    pub(crate) fn as_raw(&self) -> ptr::NonNull<libc::DIR> {
+        self.0
+    }
 }
 
 unsafe impl Send for Dir {}
@@ -78,7 +84,7 @@ impl Entry {
 
     /// Returns the type of this directory entry.
     pub fn file_type(&self) -> FileType {
-        unsafe { FileType::from_raw(self.0.d_type) }
+        FileType::from_raw(self.0.d_type)
     }
 }
 
@@ -107,7 +113,7 @@ pub enum FileType {
 }
 
 impl FileType {
-    pub unsafe fn from_raw(file_type: u8) -> Self {
+    pub fn from_raw(file_type: u8) -> Self {
         match file_type {
             libc::DT_CHR => Self::CharacterDevice,
             libc::DT_DIR => Self::Directory,
@@ -153,6 +159,6 @@ where
     type Item = Result<Entry>;
 
     fn next(&mut self) -> Option<Self::Item> {
-        unsafe { iter_impl(&self.0).map(|x| x.map(Entry)) }
+        iter_impl(&self.0).map(|x| x.map(Entry))
     }
 }

crates/wasi-common/yanix/src/poll.rs

@@ -35,7 +35,7 @@ impl PollFd {
     }
 }
 
-pub fn poll(fds: &mut [PollFd], timeout: i32) -> Result<usize> {
+pub fn poll(fds: &mut [PollFd], timeout: libc::c_int) -> Result<usize> {
     Errno::from_result(unsafe {
         libc::poll(
             fds.as_mut_ptr() as *mut libc::pollfd,

crates/wasi-common/yanix/src/sys/bsd/dir.rs

@@ -18,9 +18,9 @@ impl Deref for EntryImpl {
     }
 }
 
-pub(crate) unsafe fn iter_impl(dir: &Dir) -> Option<Result<EntryImpl>> {
+pub(crate) fn iter_impl(dir: &Dir) -> Option<Result<EntryImpl>> {
     let errno = Errno::last();
-    let dirent = libc::readdir(dir.0.as_ptr());
+    let dirent = unsafe { libc::readdir(dir.as_raw().as_ptr()) };
     if dirent.is_null() {
         if errno != Errno::last() {
             // TODO This should be verified on different BSD-flavours.
@@ -35,7 +35,7 @@ pub(crate) unsafe fn iter_impl(dir: &Dir) -> Option<Result<EntryImpl>> {
         }
     } else {
         Some(Ok(EntryImpl {
-            dirent: *dirent,
+            dirent: unsafe { *dirent },
             loc: dir.tell(),
         }))
     }

crates/wasi-common/yanix/src/sys/linux/dir.rs

@@ -25,9 +25,9 @@ impl EntryExt for Entry {
     }
 }
 
-pub(crate) unsafe fn iter_impl(dir: &Dir) -> Option<Result<EntryImpl>> {
+pub(crate) fn iter_impl(dir: &Dir) -> Option<Result<EntryImpl>> {
     let errno = Errno::last();
-    let dirent = libc::readdir64(dir.0.as_ptr());
+    let dirent = unsafe { libc::readdir64(dir.as_raw().as_ptr()) };
     if dirent.is_null() {
         if errno != Errno::last() {
             // TODO This should be verified on different BSD-flavours.
@@ -41,6 +41,6 @@ pub(crate) unsafe fn iter_impl(dir: &Dir) -> Option<Result<EntryImpl>> {
             None
         }
     } else {
-        Some(Ok(EntryImpl(*dirent)))
+        Some(Ok(EntryImpl(unsafe { *dirent })))
     }
 }

crates/wasi-common/yanix/src/sys/mod.rs

@@ -5,10 +5,10 @@ cfg_if! {
     if #[cfg(any(target_os = "linux",
                  target_os = "android"))] {
         mod linux;
-        pub(crate) use self::linux::*;
+        pub(crate) use linux::*;
     } else if #[cfg(target_os = "emscripten")] {
         mod emscripten;
-        pub(crate) use self::emscripten::*;
+        pub(crate) use emscripten::*;
     } else if #[cfg(any(target_os = "macos",
                         target_os = "ios",
                         target_os = "freebsd",
@@ -16,7 +16,7 @@ cfg_if! {
                         target_os = "openbsd",
                         target_os = "dragonfly"))] {
         mod bsd;
-        pub(crate) use self::bsd::*;
+        pub(crate) use bsd::*;
     } else {
         compile_error!("yanix doesn't compile for this platform yet");
     }