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Fix fd_readdir on BSD-style nixes (#81)

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* Fix fd_readdir on BSD-style nixes

The fix was tested on Darwin-XNU and FreeBSD. The change introduces
thread-safe cache of (RawFd, *mut libc::DIR) pairs so that
libc::fdopendir syscall is called only once when invoking fd_readdir
for the first time, and then the pointer to the directory stream,
*mut libc::DIR, is reused until the matching raw file descriptor
is closed.

This fix allows then correct use (and matching to the implementation
on Linux kernels) of libc::seekdir and libc::rewinddir to seek through
and rewind the existing directory stream, *mut libc::DIR, which
otherwise seems to be reset/invalidated every time libc::fdopendir
is called (unlike on Linux, where this behaviour is not observed).

* Store dir stream as part of the FdEntry's Descriptor

* Move bsd specifics into separate module

* Add todo comments and fix formatting

* Refactor int conversions

* Emphasise in debug logs that we're looking at fd_readdir entry

* Change visibility of FdEntry and related to public-private

* Rewrite creating DirStream for the first time
This commit is contained in:
Jakub Konka
2019-09-14 21:01:39 +02:00
committed by GitHub
parent 500e32a3b2
commit c98b3d10ec
15 changed files with 484 additions and 219 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
src/hostcalls_impl/fs.rs
View File

@@ -158,7 +158,7 @@ pub(crate) fn fd_read(
.collect();
let maybe_host_nread = match &mut *fe.fd_object.descriptor {
Descriptor::File(f) => f.read_vectored(&mut iovs),
Descriptor::OsFile(file) => file.read_vectored(&mut iovs),
Descriptor::Stdin => io::stdin().lock().read_vectored(&mut iovs),
_ => return Err(Error::EBADF),
};
@@ -203,7 +203,7 @@ pub(crate) fn fd_renumber(
.fd_object
.descriptor
.as_file()
.and_then(FdEntry::duplicate)?;
.and_then(|file| FdEntry::duplicate(file))?;
wasi_ctx.fds.insert(to, fe_from_dup);
wasi_ctx.fds.remove(&from);
@@ -212,7 +212,7 @@ pub(crate) fn fd_renumber(
}
pub(crate) fn fd_seek(
wasi_ctx: &WasiCtx,
wasi_ctx: &mut WasiCtx,
memory: &mut [u8],
fd: wasm32::__wasi_fd_t,
offset: wasm32::__wasi_filedelta_t,
@@ -236,9 +236,9 @@ pub(crate) fn fd_seek(
} else {
host::__WASI_RIGHT_FD_SEEK | host::__WASI_RIGHT_FD_TELL
};
let mut fd = wasi_ctx
.get_fd_entry(fd, rights, 0)
.and_then(|fe| fe.fd_object.descriptor.as_file())?;
let fd = wasi_ctx
.get_fd_entry_mut(fd, rights, 0)
.and_then(|fe| fe.fd_object.descriptor.as_file_mut())?;
let pos = match whence {
host::__WASI_WHENCE_CUR => SeekFrom::Current(offset),
@@ -254,7 +254,7 @@ pub(crate) fn fd_seek(
}
pub(crate) fn fd_tell(
wasi_ctx: &WasiCtx,
wasi_ctx: &mut WasiCtx,
memory: &mut [u8],
fd: wasm32::__wasi_fd_t,
newoffset: wasm32::uintptr_t,
@@ -262,9 +262,9 @@ pub(crate) fn fd_tell(
trace!("fd_tell(fd={:?}, newoffset={:#x?})", fd, newoffset);
let fd = dec_fd(fd);
let mut fd = wasi_ctx
.get_fd_entry(fd, host::__WASI_RIGHT_FD_TELL, 0)
.and_then(|fe| fe.fd_object.descriptor.as_file())?;
let fd = wasi_ctx
.get_fd_entry_mut(fd, host::__WASI_RIGHT_FD_TELL, 0)
.and_then(|fe| fe.fd_object.descriptor.as_file_mut())?;
let host_offset = fd.seek(SeekFrom::Current(0))?;
@@ -377,7 +377,7 @@ pub(crate) fn fd_write(
// perform unbuffered writes
let host_nwritten = match &mut *fe.fd_object.descriptor {
Descriptor::File(f) => f.write_vectored(&iovs)?,
Descriptor::OsFile(file) => file.write_vectored(&iovs)?,
Descriptor::Stdin => return Err(Error::EBADF),
Descriptor::Stdout => {
// lock for the duration of the scope
@@ -595,7 +595,7 @@ pub(crate) fn path_open(
}
pub(crate) fn fd_readdir(
wasi_ctx: &WasiCtx,
wasi_ctx: &mut WasiCtx,
memory: &mut [u8],
fd: wasm32::__wasi_fd_t,
buf: wasm32::uintptr_t,
@@ -615,17 +615,16 @@ pub(crate) fn fd_readdir(
enc_usize_byref(memory, buf_used, 0)?;
let fd = dec_fd(fd);
let fd = wasi_ctx
.get_fd_entry(fd, host::__WASI_RIGHT_FD_READDIR, 0)
.and_then(|fe| fe.fd_object.descriptor.as_file())?;
let file = wasi_ctx
.get_fd_entry_mut(fd, host::__WASI_RIGHT_FD_READDIR, 0)
.and_then(|entry| entry.fd_object.descriptor.as_file_mut())?;
let host_buf = dec_slice_of_mut::<u8>(memory, buf, buf_len)?;
trace!(" | (buf,buf_len)={:?}", host_buf);
let cookie = dec_dircookie(cookie);
let host_bufused = hostcalls_impl::fd_readdir(fd, host_buf, cookie)?;
let host_bufused = hostcalls_impl::fd_readdir(file, host_buf, cookie)?;
trace!(" | *buf_used={:?}", host_bufused);