wasmer_wasix/syscalls/wasi/fd_read.rs
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use std::{collections::VecDeque, task::Waker};
use virtual_fs::{AsyncReadExt, DeviceFile, ReadBuf};
use super::*;
use crate::{
fs::NotificationInner,
journal::SnapshotTrigger,
net::socket::TimeType,
os::task::process::{MaybeCheckpointResult, WasiProcessCheckpoint, WasiProcessInner},
syscalls::*,
};
/// ### `fd_read()`
/// Read data from file descriptor
/// Inputs:
/// - `Fd fd`
/// File descriptor from which data will be read
/// - `const __wasi_iovec_t *iovs`
/// Vectors where data will be stored
/// - `u32 iovs_len`
/// Length of data in `iovs`
/// Output:
/// - `u32 *nread`
/// Number of bytes read
///
#[instrument(level = "trace", skip_all, fields(%fd, nread = field::Empty), ret)]
pub fn fd_read<M: MemorySize>(
mut ctx: FunctionEnvMut<'_, WasiEnv>,
fd: WasiFd,
iovs: WasmPtr<__wasi_iovec_t<M>, M>,
iovs_len: M::Offset,
nread: WasmPtr<M::Offset, M>,
) -> Result<Errno, WasiError> {
WasiEnv::do_pending_operations(&mut ctx)?;
let pid = ctx.data().pid();
let tid = ctx.data().tid();
let offset = {
let mut env = ctx.data();
let state = env.state.clone();
let inodes = state.inodes.clone();
let fd_entry = wasi_try_ok!(state.fs.get_fd(fd));
fd_entry.inner.offset.load(Ordering::Acquire) as usize
};
ctx = wasi_try_ok!(maybe_backoff::<M>(ctx)?);
if fd == DeviceFile::STDIN {
ctx = wasi_try_ok!(maybe_snapshot_once::<M>(ctx, SnapshotTrigger::FirstStdin)?);
}
let res = fd_read_internal::<M>(&mut ctx, fd, iovs, iovs_len, offset, nread, true)?;
fd_read_internal_handler(ctx, res, nread)
}
/// ### `fd_pread()`
/// Read from the file at the given offset without updating the file cursor.
/// This acts like a stateless version of Seek + Read
/// Inputs:
/// - `Fd fd`
/// The file descriptor to read the data with
/// - `const __wasi_iovec_t* iovs'
/// Vectors where the data will be stored
/// - `size_t iovs_len`
/// The number of vectors to store the data into
/// - `Filesize offset`
/// The file cursor to use: the starting position from which data will be read
/// Output:
/// - `size_t nread`
/// The number of bytes read
#[instrument(level = "trace", skip_all, fields(%fd, %offset, ?nread), ret)]
pub fn fd_pread<M: MemorySize>(
mut ctx: FunctionEnvMut<'_, WasiEnv>,
fd: WasiFd,
iovs: WasmPtr<__wasi_iovec_t<M>, M>,
iovs_len: M::Offset,
offset: Filesize,
nread: WasmPtr<M::Offset, M>,
) -> Result<Errno, WasiError> {
let pid = ctx.data().pid();
let tid = ctx.data().tid();
ctx = wasi_try_ok!(maybe_backoff::<M>(ctx)?);
if fd == DeviceFile::STDIN {
ctx = wasi_try_ok!(maybe_snapshot_once::<M>(ctx, SnapshotTrigger::FirstStdin)?);
}
let res = fd_read_internal::<M>(&mut ctx, fd, iovs, iovs_len, offset as usize, nread, false)?;
fd_read_internal_handler::<M>(ctx, res, nread)
}
pub(crate) fn fd_read_internal_handler<M: MemorySize>(
mut ctx: FunctionEnvMut<'_, WasiEnv>,
res: Result<usize, Errno>,
nread: WasmPtr<M::Offset, M>,
) -> Result<Errno, WasiError> {
let mut ret = Errno::Success;
let bytes_read = match res {
Ok(bytes_read) => bytes_read,
Err(err) => {
ret = err;
0
}
};
Span::current().record("nread", bytes_read);
let bytes_read: M::Offset = wasi_try_ok!(bytes_read.try_into().map_err(|_| Errno::Overflow));
let env = ctx.data();
let memory = unsafe { env.memory_view(&ctx) };
let env = ctx.data();
let memory = unsafe { env.memory_view(&ctx) };
let nread_ref = nread.deref(&memory);
wasi_try_mem_ok!(nread_ref.write(bytes_read));
Ok(ret)
}
#[allow(clippy::await_holding_lock)]
pub(crate) fn fd_read_internal<M: MemorySize>(
ctx: &mut FunctionEnvMut<'_, WasiEnv>,
fd: WasiFd,
iovs: WasmPtr<__wasi_iovec_t<M>, M>,
iovs_len: M::Offset,
offset: usize,
nread: WasmPtr<M::Offset, M>,
should_update_cursor: bool,
) -> WasiResult<usize> {
let env = ctx.data();
let memory = unsafe { env.memory_view(&ctx) };
let state = env.state();
let fd_entry = wasi_try_ok_ok!(state.fs.get_fd(fd));
let is_stdio = fd_entry.is_stdio;
let bytes_read = {
if !is_stdio && !fd_entry.inner.rights.contains(Rights::FD_READ) {
// TODO: figure out the error to return when lacking rights
return Ok(Err(Errno::Access));
}
let inode = fd_entry.inode;
let fd_flags = fd_entry.inner.flags;
let (bytes_read, can_update_cursor) = {
let mut guard = inode.write();
match guard.deref_mut() {
Kind::File { handle, .. } => {
if let Some(handle) = handle {
let handle = handle.clone();
drop(guard);
let res = __asyncify_light(
env,
if fd_flags.contains(Fdflags::NONBLOCK) {
Some(Duration::ZERO)
} else {
None
},
async move {
let mut handle = match handle.write() {
Ok(a) => a,
Err(_) => return Err(Errno::Fault),
};
if !is_stdio {
handle
.seek(std::io::SeekFrom::Start(offset as u64))
.await
.map_err(map_io_err)?;
}
let mut total_read = 0usize;
let iovs_arr =
iovs.slice(&memory, iovs_len).map_err(mem_error_to_wasi)?;
let iovs_arr = iovs_arr.access().map_err(mem_error_to_wasi)?;
for iovs in iovs_arr.iter() {
let mut buf = WasmPtr::<u8, M>::new(iovs.buf)
.slice(&memory, iovs.buf_len)
.map_err(mem_error_to_wasi)?
.access()
.map_err(mem_error_to_wasi)?;
let r = handle.read(buf.as_mut()).await.map_err(|err| {
let err = From::<std::io::Error>::from(err);
match err {
Errno::Again => {
if is_stdio {
Errno::Badf
} else {
Errno::Again
}
}
a => a,
}
});
let local_read = match r {
Ok(s) => s,
Err(_) if total_read > 0 => break,
Err(err) => return Err(err),
};
total_read += local_read;
if local_read != buf.len() {
break;
}
}
Ok(total_read)
},
);
let read = wasi_try_ok_ok!(res?.map_err(|err| match err {
Errno::Timedout => Errno::Again,
a => a,
}));
(read, true)
} else {
return Ok(Err(Errno::Badf));
}
}
Kind::Socket { socket } => {
let socket = socket.clone();
drop(guard);
let nonblocking = fd_flags.contains(Fdflags::NONBLOCK);
let timeout = socket
.opt_time(TimeType::ReadTimeout)
.ok()
.flatten()
.unwrap_or(Duration::from_secs(30));
let tasks = env.tasks().clone();
let res = __asyncify_light(
env,
if fd_flags.contains(Fdflags::NONBLOCK) {
Some(Duration::ZERO)
} else {
None
},
async move {
let mut total_read = 0usize;
let iovs_arr =
iovs.slice(&memory, iovs_len).map_err(mem_error_to_wasi)?;
let iovs_arr = iovs_arr.access().map_err(mem_error_to_wasi)?;
for iovs in iovs_arr.iter() {
let mut buf = WasmPtr::<u8, M>::new(iovs.buf)
.slice(&memory, iovs.buf_len)
.map_err(mem_error_to_wasi)?
.access()
.map_err(mem_error_to_wasi)?;
let local_read = socket
.recv(
tasks.deref(),
buf.as_mut_uninit(),
Some(timeout),
nonblocking,
false,
)
.await?;
total_read += local_read;
if total_read != buf.len() {
break;
}
}
Ok(total_read)
},
);
let res = res?.map_err(|err| match err {
Errno::Timedout => Errno::Again,
a => a,
});
match res {
Err(Errno::Connaborted) | Err(Errno::Connreset) => (0, false),
res => {
let bytes_read = wasi_try_ok_ok!(res);
(bytes_read, false)
}
}
}
Kind::PipeTx { .. } => return Ok(Err(Errno::Badf)),
Kind::PipeRx { rx } => {
let mut rx = rx.clone();
drop(guard);
let nonblocking = fd_flags.contains(Fdflags::NONBLOCK);
let res = __asyncify_light(
env,
if fd_flags.contains(Fdflags::NONBLOCK) {
Some(Duration::ZERO)
} else {
None
},
async move {
let mut total_read = 0usize;
let iovs_arr =
iovs.slice(&memory, iovs_len).map_err(mem_error_to_wasi)?;
let iovs_arr = iovs_arr.access().map_err(mem_error_to_wasi)?;
for iovs in iovs_arr.iter() {
let mut buf = WasmPtr::<u8, M>::new(iovs.buf)
.slice(&memory, iovs.buf_len)
.map_err(mem_error_to_wasi)?
.access()
.map_err(mem_error_to_wasi)?;
let local_read = match nonblocking {
true => match rx.try_read(buf.as_mut()) {
Some(amt) => amt,
None => {
return Err(Errno::Again);
}
},
false => {
virtual_fs::AsyncReadExt::read(&mut rx, buf.as_mut())
.await?
}
};
total_read += local_read;
if local_read != buf.len() {
break;
}
}
Ok(total_read)
},
);
let bytes_read = wasi_try_ok_ok!(res?.map_err(|err| match err {
Errno::Timedout => Errno::Again,
a => a,
}));
(bytes_read, false)
}
Kind::DuplexPipe { pipe } => {
let mut pipe = pipe.clone();
drop(guard);
let nonblocking = fd_flags.contains(Fdflags::NONBLOCK);
let res = __asyncify_light(
env,
if fd_flags.contains(Fdflags::NONBLOCK) {
Some(Duration::ZERO)
} else {
None
},
async move {
let mut total_read = 0usize;
let iovs_arr =
iovs.slice(&memory, iovs_len).map_err(mem_error_to_wasi)?;
let iovs_arr = iovs_arr.access().map_err(mem_error_to_wasi)?;
for iovs in iovs_arr.iter() {
let mut buf = WasmPtr::<u8, M>::new(iovs.buf)
.slice(&memory, iovs.buf_len)
.map_err(mem_error_to_wasi)?
.access()
.map_err(mem_error_to_wasi)?;
let local_read = match nonblocking {
true => match pipe.try_read(buf.as_mut()) {
Some(amt) => amt,
None => {
return Err(Errno::Again);
}
},
false => {
virtual_fs::AsyncReadExt::read(&mut pipe, buf.as_mut())
.await?
}
};
total_read += local_read;
if local_read != buf.len() {
break;
}
}
Ok(total_read)
},
);
let bytes_read = wasi_try_ok_ok!(res?.map_err(|err| match err {
Errno::Timedout => Errno::Again,
a => a,
}));
(bytes_read, false)
}
Kind::Dir { .. } | Kind::Root { .. } => {
// TODO: verify
return Ok(Err(Errno::Isdir));
}
Kind::EventNotifications { inner } => {
// Create a poller
struct NotifyPoller {
inner: Arc<NotificationInner>,
non_blocking: bool,
}
let poller = NotifyPoller {
inner: inner.clone(),
non_blocking: fd_flags.contains(Fdflags::NONBLOCK),
};
drop(guard);
// The poller will register itself for notifications and wait for the
// counter to drop
impl Future for NotifyPoller {
type Output = Result<u64, Errno>;
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
if self.non_blocking {
Poll::Ready(self.inner.try_read().ok_or(Errno::Again))
} else {
self.inner.read(cx.waker()).map(Ok)
}
}
}
// Yield until the notifications are triggered
let tasks_inner = env.tasks().clone();
let res = __asyncify_light(env, None, poller)?.map_err(|err| match err {
Errno::Timedout => Errno::Again,
a => a,
});
let val = wasi_try_ok_ok!(res);
let mut memory = unsafe { env.memory_view(ctx) };
let reader = val.to_ne_bytes();
let iovs_arr = wasi_try_mem_ok_ok!(iovs.slice(&memory, iovs_len));
let ret = wasi_try_ok_ok!(read_bytes(&reader[..], &memory, iovs_arr));
(ret, false)
}
Kind::Symlink { .. } | Kind::Epoll { .. } => {
return Ok(Err(Errno::Notsup));
}
Kind::Buffer { buffer } => {
let memory = unsafe { env.memory_view(ctx) };
let iovs_arr = wasi_try_mem_ok_ok!(iovs.slice(&memory, iovs_len));
let read = wasi_try_ok_ok!(read_bytes(&buffer[offset..], &memory, iovs_arr));
(read, true)
}
}
};
if !is_stdio && should_update_cursor && can_update_cursor {
// reborrow
let mut fd_map = state.fs.fd_map.write().unwrap();
let fd_entry = wasi_try_ok_ok!(fd_map.get_mut(fd).ok_or(Errno::Badf));
let old = fd_entry
.offset
.fetch_add(bytes_read as u64, Ordering::AcqRel);
}
bytes_read
};
Ok(Ok(bytes_read))
}