From e6f188286bc593dc9b2e3ee93924fb711b327e44 Mon Sep 17 00:00:00 2001 From: Mark McCaskey Date: Thu, 1 Aug 2019 14:58:17 +0900 Subject: [PATCH] Implement wasi::fd_pread --- lib/wasi/src/syscalls/mod.rs | 105 ++++++++++++++++++++++++++++------- 1 file changed, 84 insertions(+), 21 deletions(-) diff --git a/lib/wasi/src/syscalls/mod.rs b/lib/wasi/src/syscalls/mod.rs index c5435995b..a316a9407 100644 --- a/lib/wasi/src/syscalls/mod.rs +++ b/lib/wasi/src/syscalls/mod.rs @@ -56,6 +56,23 @@ fn write_bytes( Ok(bytes_written) } +fn read_bytes( + mut reader: T, + memory: &Memory, + iovs_arr_cell: &[Cell<__wasi_iovec_t>], +) -> Result { + let mut bytes_read = 0; + + for iov in iovs_arr_cell { + let iov_inner = iov.get(); + let bytes = iov_inner.buf.deref(memory, 0, iov_inner.buf_len)?; + let mut raw_bytes: &mut [u8] = + unsafe { &mut *(bytes as *const [_] as *mut [_] as *mut [u8]) }; + bytes_read += reader.read(raw_bytes).map_err(|_| __WASI_EIO)? as u32; + } + Ok(bytes_read) +} + /// checks that `rights_check_set` is a subset of `rights_set` fn has_rights(rights_set: __wasi_rights_t, rights_check_set: __wasi_rights_t) -> bool { rights_set | rights_check_set == rights_set @@ -607,6 +624,21 @@ pub fn fd_filestat_set_times( __WASI_ESUCCESS } +/// ### `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: +/// - `__wasi_fd_t 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 +/// - `__wasi_filesize_t offset` +/// The file cursor to use: the starting position from which data will be read +/// Output: +/// - `size_t nread` +/// The number of bytes read pub fn fd_pread( ctx: &mut Ctx, fd: __wasi_fd_t, @@ -620,9 +652,56 @@ pub fn fd_pread( let iov_cells = wasi_try!(iovs.deref(memory, 0, iovs_len)); let nread_cell = wasi_try!(nread.deref(memory)); + let state = get_wasi_state(ctx); - unimplemented!("wasi::fd_pread"); + let bytes_read = match fd { + __WASI_STDIN_FILENO => wasi_try!(read_bytes(&mut state.fs.stdin, memory, iov_cells)), + __WASI_STDOUT_FILENO => return __WASI_EINVAL, + __WASI_STDERR_FILENO => return __WASI_EINVAL, + _ => { + let fd_entry = wasi_try!(state.fs.fd_map.get_mut(&fd).ok_or(__WASI_EBADF)); + let inode = fd_entry.inode; + if !(has_rights(fd_entry.rights, __WASI_RIGHT_FD_READ) + && has_rights(fd_entry.rights, __WASI_RIGHT_FD_SEEK)) + { + return __WASI_EACCES; + } + match &mut state.fs.inodes[inode].kind { + Kind::File { handle, .. } => { + if let Some(h) = handle { + let current_pos = + wasi_try!(h.seek(std::io::SeekFrom::Current(0)).ok(), __WASI_EIO); + wasi_try!( + h.seek(std::io::SeekFrom::Start(offset as u64)).ok(), + __WASI_EIO + ); + let bytes_read = wasi_try!(read_bytes(h, memory, iov_cells)); + // reborrow so we can seek it back (the &mut gets moved into `read_bytes` + // and we can't use it after) + // If you're in the future and there's a nicer way to do this, please + // clean up this code + if let Some(h) = handle { + wasi_try!( + h.seek(std::io::SeekFrom::Start(current_pos)).ok(), + __WASI_EIO + ); + } + bytes_read + } else { + return __WASI_EINVAL; + } + } + Kind::Dir { .. } | Kind::Root { .. } => return __WASI_EISDIR, + Kind::Symlink { .. } => unimplemented!("Symlinks in wasi::fd_pread"), + Kind::Buffer { buffer } => { + wasi_try!(read_bytes(&buffer[(offset as usize)..], memory, iov_cells)) + } + } + } + }; + + nread_cell.set(bytes_read); __WASI_ESUCCESS } @@ -733,8 +812,9 @@ pub fn fd_pwrite( _ => { let fd_entry = wasi_try!(state.fs.fd_map.get_mut(&fd).ok_or(__WASI_EBADF)); - if !has_rights(fd_entry.rights, __WASI_RIGHT_FD_WRITE) { - // TODO: figure out the error to return when lacking rights + if !(has_rights(fd_entry.rights, __WASI_RIGHT_FD_WRITE) + && has_rights(fd_entry.rights, __WASI_RIGHT_FD_SEEK)) + { return __WASI_EACCES; } @@ -794,23 +874,6 @@ pub fn fd_read( let iovs_arr_cell = wasi_try!(iovs.deref(memory, 0, iovs_len)); let nread_cell = wasi_try!(nread.deref(memory)); - - fn read_bytes( - mut reader: T, - memory: &Memory, - iovs_arr_cell: &[Cell<__wasi_iovec_t>], - ) -> Result { - let mut bytes_read = 0; - - for iov in iovs_arr_cell { - let iov_inner = iov.get(); - let bytes = iov_inner.buf.deref(memory, 0, iov_inner.buf_len)?; - let mut raw_bytes: &mut [u8] = - unsafe { &mut *(bytes as *const [_] as *mut [_] as *mut [u8]) }; - bytes_read += reader.read(raw_bytes).map_err(|_| __WASI_EIO)? as u32; - } - Ok(bytes_read) - } let state = get_wasi_state(ctx); let bytes_read = match fd { @@ -830,7 +893,7 @@ pub fn fd_read( let bytes_read = match &mut inode.kind { Kind::File { handle, .. } => { if let Some(handle) = handle { - handle.seek(::std::io::SeekFrom::Start(offset as u64)); + handle.seek(std::io::SeekFrom::Start(offset as u64)); wasi_try!(read_bytes(handle, memory, iovs_arr_cell)) } else { return __WASI_EINVAL;