Add support for WASI opening Unix special files

CHANGELOG.md

@@ -1,6 +1,12 @@
 # Changelog
 
 ## **[Unreleased]**
+- [#1566](https://github.com/wasmerio/wasmer/pull/1566) Add support for opening special Unix files to the WASI FS
+
+## TODO: 1.0.0-alpha1.0
+- Wasmer refactor lands
+
+## TODO: 17...
 
 - [#1554](https://github.com/wasmerio/wasmer/pull/1554) Update supported stable Rust version to 1.45.2.
 - [#1552](https://github.com/wasmerio/wasmer/pull/1552) Disable `sigint` handler by default.

lib/wasi/src/state/mod.rs

@@ -819,6 +819,56 @@ impl WasiFs {
                                     relative_path: link_value,
                                 }
                             } else {
+                                #[cfg(unix)]
+                                {
+                                    use std::os::unix::fs::FileTypeExt;
+                                    let file_type: __wasi_filetype_t = if file_type.is_char_device()
+                                    {
+                                        __WASI_FILETYPE_CHARACTER_DEVICE
+                                    } else if file_type.is_block_device() {
+                                        __WASI_FILETYPE_BLOCK_DEVICE
+                                    } else if file_type.is_fifo() {
+                                        // FIFO doesn't seem to fit any other type, so unknown
+                                        __WASI_FILETYPE_UNKNOWN
+                                    } else if file_type.is_socket() {
+                                        // TODO: how do we know if it's a `__WASI_FILETYPE_SOCKET_STREAM` or
+                                        // a `__WASI_FILETYPE_SOCKET_DGRAM`?
+                                        __WASI_FILETYPE_SOCKET_STREAM
+                                    } else {
+                                        unimplemented!("state::get_inode_at_path unknown file type: not file, directory, symlink, char device, block device, fifo, or socket");
+                                    };
+
+                                    let kind = Kind::File {
+                                        handle: None,
+                                        path: file.clone(),
+                                        fd: None,
+                                    };
+                                    let new_inode = self.create_inode_with_stat(
+                                        kind,
+                                        false,
+                                        file.to_string_lossy().to_string(),
+                                        __wasi_filestat_t {
+                                            st_filetype: file_type,
+                                            ..__wasi_filestat_t::default()
+                                        },
+                                    );
+                                    if let Kind::Dir {
+                                        ref mut entries, ..
+                                    } = &mut self.inodes[cur_inode].kind
+                                    {
+                                        entries.insert(
+                                            component.as_os_str().to_string_lossy().to_string(),
+                                            new_inode,
+                                        );
+                                    } else {
+                                        unreachable!(
+                                            "Attempted to insert special device into non-directory"
+                                        );
+                                    }
+                                    // perhaps just continue with symlink resolution and return at the end
+                                    return Ok(new_inode);
+                                }
+                                #[cfg(not(unix))]
                                 unimplemented!("state::get_inode_at_path unknown file type: not file, directory, or symlink");
                             };
 
@@ -1178,25 +1228,29 @@ impl WasiFs {
         is_preopened: bool,
         name: String,
     ) -> Result<Inode, __wasi_errno_t> {
-        let mut stat = self.get_stat_for_kind(&kind).ok_or(__WASI_EIO)?;
-        stat.st_ino = self.get_next_inode_index();
-
-        Ok(self.inodes.insert(InodeVal {
-            stat,
-            is_preopened,
-            name,
-            kind,
-        }))
+        let stat = self.get_stat_for_kind(&kind).ok_or(__WASI_EIO)?;
+        Ok(self.create_inode_with_stat(kind, is_preopened, name, stat))
     }
 
-    /// creates an inode and inserts it given a Kind, does not assume the file exists to
+    /// Creates an inode and inserts it given a Kind, does not assume the file exists.
     pub(crate) fn create_inode_with_default_stat(
         &mut self,
         kind: Kind,
         is_preopened: bool,
         name: String,
     ) -> Inode {
-        let mut stat = __wasi_filestat_t::default();
+        let stat = __wasi_filestat_t::default();
+        self.create_inode_with_stat(kind, is_preopened, name, stat)
+    }
+
+    /// Creates an inode with the given filestat and inserts it.
+    pub(crate) fn create_inode_with_stat(
+        &mut self,
+        kind: Kind,
+        is_preopened: bool,
+        name: String,
+        mut stat: __wasi_filestat_t,
+    ) -> Inode {
         stat.st_ino = self.get_next_inode_index();
 
         self.inodes.insert(InodeVal {

tests/ignores.txt

@@ -67,3 +67,7 @@ wasitests::unstable::file_metadata on windows
 wasitests::unstable::fseek on windows
 wasitests::unstable::path_link on windows
 wasitests::unstable::path_symlink on windows
+
+# This test is meant to only run on Unix
+wasitests::unstable::unix_open_special_files on windows
+wasitests::snapshot1::unix_open_special_files on windows

tests/wasi-wast/README.md

@@ -25,3 +25,8 @@ And here's an example of how to generate these tests:
 cargo run -- -as # set up the toolchains for all targets
 cargo run -- -ag # generate the WASI tests for all targets
 ```
+
+## Updating in Wasmer
+
+Run
+`git subtree pull --prefix tests/wasi-wast git@github.com:wasmerio/wasi-tests master --squash`

tests/wasi-wast/wasi/snapshot1/unix_open_special_files.wast

@@ -0,0 +1,5 @@
+(wasi_test "unix_open_special_files.wasm"
+  (map_dirs "/dev:/dev")
+  (assert_return (i64.const 0))
+  (assert_stdout "13\n")
+)

tests/wasi-wast/wasi/tests/unix_open_special_files.rs

@@ -0,0 +1,14 @@
+// WASI:
+// mapdir: /dev:/dev
+
+use std::fs;
+use std::io::Write;
+
+fn main() {
+    let mut f = fs::OpenOptions::new()
+        .write(true)
+        .open("/dev/null")
+        .unwrap();
+    let result = f.write(b"hello, world!").unwrap();
+    println!("{}", result);
+}

tests/wasi-wast/wasi/unstable/unix_open_special_files.wast

@@ -0,0 +1,5 @@
+(wasi_test "unix_open_special_files.wasm"
+  (map_dirs "/dev:/dev")
+  (assert_return (i64.const 0))
+  (assert_stdout "13\n")
+)