Improve support for preopened directories in WASI syscalls

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## **[Unreleased]**
 
+- [#1263](https://github.com/wasmerio/wasmer/pull/1263) Changed the behavior of some WASI syscalls to now handle preopened directories more properly. Changed default `--debug` logging to only show Wasmer-related messages.
 - [#1217](https://github.com/wasmerio/wasmer/pull/1217) Polymorphic host functions based on dynamic trampoline generation.
 - [#1252](https://github.com/wasmerio/wasmer/pull/1252) Allow `/` in wasi `--mapdir` wasm path.
 - [#1212](https://github.com/wasmerio/wasmer/pull/1212) Add support for GDB JIT debugging:

lib/wasi/src/state/mod.rs

@@ -1077,6 +1077,15 @@ impl WasiFs {
                     fs_rights_inheriting: 0,
                 })
             }
+            VIRTUAL_ROOT_FD => {
+                return Ok(__wasi_fdstat_t {
+                    fs_filetype: __WASI_FILETYPE_DIRECTORY,
+                    fs_flags: 0,
+                    // TODO: fix this
+                    fs_rights_base: ALL_RIGHTS,
+                    fs_rights_inheriting: ALL_RIGHTS,
+                });
+            }
             _ => (),
         }
         let fd = self.get_fd(fd)?;

lib/wasi/src/syscalls/mod.rs

@@ -370,8 +370,7 @@ pub fn fd_allocate(
 /// - `__WASI_EBADF`
 ///     If `fd` is invalid or not open
 pub fn fd_close(ctx: &mut Ctx, fd: __wasi_fd_t) -> __wasi_errno_t {
-    debug!("wasi::fd_close");
-    debug!("=> fd={}", fd);
+    debug!("wasi::fd_close: fd={}", fd);
     let (memory, state) = get_memory_and_wasi_state(ctx, 0);
 
     let fd_entry = wasi_try!(state.fs.get_fd(fd));
@@ -649,7 +648,7 @@ pub fn fd_pread(
     offset: __wasi_filesize_t,
     nread: WasmPtr<u32>,
 ) -> __wasi_errno_t {
-    debug!("wasi::fd_pread");
+    debug!("wasi::fd_pread: fd={}, offset={}", fd, offset);
     let (memory, state) = get_memory_and_wasi_state(ctx, 0);
 
     let iov_cells = wasi_try!(iovs.deref(memory, 0, iovs_len));
@@ -674,6 +673,10 @@ pub fn fd_pread(
             if !(has_rights(fd_entry.rights, __WASI_RIGHT_FD_READ)
                 && has_rights(fd_entry.rights, __WASI_RIGHT_FD_SEEK))
             {
+                debug!(
+                    "Invalid rights on {:X}: expected READ and SEEK",
+                    fd_entry.rights
+                );
                 return __WASI_EACCES;
             }
             match &mut state.fs.inodes[inode].kind {
@@ -699,6 +702,7 @@ pub fn fd_pread(
     };
 
     nread_cell.set(bytes_read);
+    debug!("Success: {} bytes read", bytes_read);
     __WASI_ESUCCESS
 }
 
@@ -971,24 +975,38 @@ pub fn fd_readdir(
     let mut cur_cookie = cookie;
     let mut buf_idx = 0;
 
-    let entries = match &state.fs.inodes[working_dir.inode].kind {
-        Kind::Dir { path, .. } => {
+    let entries: Vec<(String, u8, u64)> = match &state.fs.inodes[working_dir.inode].kind {
+        Kind::Dir { path, entries, .. } => {
             // TODO: refactor this code
             // we need to support multiple calls,
             // simple and obviously correct implementation for now:
             // maintain consistent order via lexacographic sorting
-            let mut entries = wasi_try!(wasi_try!(std::fs::read_dir(path).map_err(|_| __WASI_EIO))
-                .collect::<Result<Vec<std::fs::DirEntry>, _>>()
+            let fs_info = wasi_try!(wasi_try!(std::fs::read_dir(path).map_err(|_| __WASI_EIO))
+                .collect::<Result<Vec<_>, _>>()
                 .map_err(|_| __WASI_EIO));
-            entries.sort_by(|a, b| a.file_name().cmp(&b.file_name()));
-            wasi_try!(entries
+            let mut entry_vec = wasi_try!(fs_info
                 .into_iter()
                 .map(|entry| Ok((
                     entry.file_name().to_string_lossy().to_string(),
                     host_file_type_to_wasi_file_type(entry.file_type().map_err(|_| __WASI_EIO)?),
                     0, // TODO: inode
                 )))
-                .collect::<Result<Vec<(String, u8, u64)>, __wasi_errno_t>>())
+                .collect::<Result<Vec<(String, u8, u64)>, _>>());
+            entry_vec.extend(
+                entries
+                    .iter()
+                    .filter(|(_, inode)| state.fs.inodes[**inode].is_preopened)
+                    .map(|(name, inode)| {
+                        let entry = &state.fs.inodes[*inode];
+                        (
+                            format!("{}", entry.name),
+                            entry.stat.st_filetype,
+                            entry.stat.st_ino,
+                        )
+                    }),
+            );
+            entry_vec.sort_by(|a, b| a.0.cmp(&b.0));
+            entry_vec
         }
         Kind::Root { entries } => {
             let sorted_entries = {
@@ -1435,10 +1453,14 @@ pub fn path_filestat_get(
         path_string,
         flags & __WASI_LOOKUP_SYMLINK_FOLLOW != 0,
     ));
-    let stat = wasi_try!(state
-        .fs
-        .get_stat_for_kind(&state.fs.inodes[file_inode].kind)
-        .ok_or(__WASI_EIO));
+    let stat = if state.fs.inodes[file_inode].is_preopened {
+        state.fs.inodes[file_inode].stat.clone()
+    } else {
+        wasi_try!(state
+            .fs
+            .get_stat_for_kind(&state.fs.inodes[file_inode].kind)
+            .ok_or(__WASI_EIO))
+    };
 
     let buf_cell = wasi_try!(buf.deref(memory));
     buf_cell.set(stat);

src/logging.rs

@@ -46,7 +46,11 @@ pub fn set_up_logging() -> Result<(), String> {
                 })
             };
 
-            base.chain(std::io::stdout())
+            base
+                .filter(|metadata| {
+                    metadata.target().starts_with("wasmer")
+                })
+                .chain(std::io::stdout())
         });
 
     dispatch.apply().map_err(|e| format!("{}", e))?;