implement map-dir for WASI; fix bug in path_open

CHANGELOG.md

@@ -6,11 +6,11 @@ Blocks of changes will separated by version increments.
 
 ## **[Unreleased]**
 
-- *empty*
+- [#451](https://github.com/wasmerio/wasmer/pull/451) Add `--mapdir=src:dest` flag to rename host directories in the guest context
+- [#457](https://github.com/wasmerio/wasmer/pull/457) Implement file metadata for WASI, fix bugs in WASI clock code for Unix platforms
 
 ## 0.4.2 - 2019-05-16
 
-- [#457](https://github.com/wasmerio/wasmer/pull/457) Implement file metadata for WASI, fix bugs in WASI clock code for Unix platforms
 - [#416](https://github.com/wasmerio/wasmer/pull/416) Remote code loading framework
 - [#449](https://github.com/wasmerio/wasmer/pull/449) Fix bugs: opening host files in filestat and opening with write permissions unconditionally in path_open
 - [#442](https://github.com/wasmerio/wasmer/pull/442) Misc. WASI FS fixes and implement readdir

examples/plugin.rs

@@ -17,7 +17,7 @@ fn main() {
     ));
 
     // WASI imports
-    let mut base_imports = generate_import_object(vec![], vec![], vec![]);
+    let mut base_imports = generate_import_object(vec![], vec![], vec![], vec![]);
     // env is the default namespace for extern functions
     let custom_imports = imports! {
         "env" => {

lib/wasi/src/lib.rs

@@ -14,6 +14,7 @@ use self::state::{WasiFs, WasiState};
 use self::syscalls::*;
 
 use std::ffi::c_void;
+use std::path::PathBuf;
 
 pub use self::utils::is_wasi_module;
 
@@ -29,6 +30,7 @@ pub fn generate_import_object(
     args: Vec<Vec<u8>>,
     envs: Vec<Vec<u8>>,
     preopened_files: Vec<String>,
+    mapped_dirs: Vec<(String, PathBuf)>,
 ) -> ImportObject {
     let state_gen = move || {
         fn state_destructor(data: *mut c_void) {
@@ -38,7 +40,7 @@ pub fn generate_import_object(
         }
 
         let state = Box::new(WasiState {
-            fs: WasiFs::new(&preopened_files).unwrap(),
+            fs: WasiFs::new(&preopened_files, &mapped_dirs).unwrap(),
             args: &args[..],
             envs: &envs[..],
         });

lib/wasi/src/state.rs

@@ -175,21 +175,20 @@ pub struct WasiFs {
 }
 
 impl WasiFs {
-    pub fn new(preopened_dirs: &[String]) -> Result<Self, String> {
-        /*let repo = RepoOpener::new()
-        .create(true)
-        .open("mem://wasmer-test-fs", "")
-        .map_err(|e| e.to_string())?;*/
+    pub fn new(
+        preopened_dirs: &[String],
+        mapped_dirs: &[(String, PathBuf)],
+    ) -> Result<Self, String> {
         debug!("wasi::fs::inodes");
         let inodes = Arena::new();
         let mut wasi_fs = Self {
-            //repo: repo,
             name_map: HashMap::new(),
             inodes: inodes,
             fd_map: HashMap::new(),
             next_fd: Cell::new(3),
             inode_counter: Cell::new(1000),
         };
+        debug!("wasi::fs::preopen_dirs");
         for dir in preopened_dirs {
             debug!("Attempting to preopen {}", &dir);
             // TODO: think about this
@@ -218,6 +217,36 @@ impl WasiFs {
                 .create_fd(default_rights, default_rights, 0, inode)
                 .expect("Could not open fd");
         }
+        debug!("wasi::fs::mapped_dirs");
+        for (alias, real_dir) in mapped_dirs {
+            debug!("Attempting to open {:?} at {}", dest_dir, alias);
+            // TODO: think about this
+            let default_rights = 0x1FFFFFFF; // all rights
+            let cur_dir_metadata = real_dir
+                .metadata()
+                .expect("mapped dir not at previously verified location");
+            let kind = if cur_dir_metadata.is_dir() {
+                Kind::Dir {
+                    parent: None,
+                    path: real_dir.clone(),
+                    entries: Default::default(),
+                }
+            } else {
+                return Err(format!(
+                    "WASI only supports pre-opened directories right now; found \"{:?}\"",
+                    &real_dir,
+                ));
+            };
+            // TODO: handle nested pats in `file`
+            let inode_val =
+                InodeVal::from_file_metadata(&cur_dir_metadata, alias.clone(), true, kind);
+
+            let inode = wasi_fs.inodes.insert(inode_val);
+            wasi_fs.inodes[inode].stat.st_ino = wasi_fs.inode_counter.get();
+            wasi_fs
+                .create_fd(default_rights, default_rights, 0, inode)
+                .expect("Could not open fd");
+        }
         debug!("wasi::fs::end");
         Ok(wasi_fs)
     }
@@ -419,29 +448,10 @@ impl WasiFs {
     }
 
     pub fn get_base_path_for_directory(&self, directory: Inode) -> Option<String> {
-        let mut path_segments = vec![];
-        let mut cur_inode = directory;
-        loop {
-            path_segments.push(self.inodes[cur_inode].name.clone());
-
-            if let Kind::Dir { parent, .. } = &self.inodes[cur_inode].kind {
-                if let Some(p_inode) = parent {
-                    cur_inode = *p_inode;
-                } else {
-                    break;
-                }
-            } else {
-                return None;
-            }
+        if let Kind::Dir { path, .. } = &self.inodes[directory].kind {
+            return Some(path.to_string_lossy().to_string());
         }
-
-        path_segments.reverse();
-        Some(
-            path_segments
-                .iter()
-                .skip(1)
-                .fold(path_segments.first()?.clone(), |a, b| a + "/" + b),
-        )
+        None
     }
 }
 

lib/wasi/src/syscalls/mod.rs

@@ -795,6 +795,7 @@ pub fn fd_readdir(
         for entry in entries.iter().skip(cookie as usize) {
             cur_cookie += 1;
             let entry_path = entry.path();
+            let entry_path = wasi_try!(entry_path.file_stem().ok_or(__WASI_EIO));
             let entry_path_str = entry_path.to_string_lossy();
             let namlen = entry_path_str.len();
             debug!("Returning dirent for {}", entry_path_str);
@@ -1486,10 +1487,11 @@ pub fn path_open(
                 .fs
                 .create_fd(fs_rights_base, fs_rights_inheriting, fs_flags, child))
         } else {
-            let file_metadata = wasi_try!(file_path.metadata().map_err(|_| __WASI_ENOENT));
+            debug!("Attempting to load file from host system");
+            let file_metadata = file_path.metadata();
             // if entry does not exist in parent directory, try to lazily
             // load it; possibly creating or truncating it if flags set
-            let kind = if file_metadata.is_dir() {
+            let kind = if file_metadata.is_ok() && file_metadata.unwrap().is_dir() {
                 // special dir logic
                 Kind::Dir {
                     parent: Some(cur_dir_inode),

lib/wasi/tests/wasitests/_common.rs

@@ -32,7 +32,7 @@ macro_rules! assert_wasi_output {
         let module = wasmer_runtime_core::compile_with(&wasm_bytes[..], &get_compiler())
             .expect("WASM can't be compiled");
 
-        let import_object = generate_import_object(vec![], vec![], vec![".".to_string()]);
+        let import_object = generate_import_object(vec![], vec![], vec![".".to_string()], vec![]);
 
         let instance = module
             .instantiate(&import_object)

src/bin/wasmer.rs

@@ -97,7 +97,11 @@ struct Run {
     #[structopt(long = "dir", multiple = true, group = "wasi")]
     pre_opened_directories: Vec<String>,
 
-    // Custom code loader
+    /// Map a host directory to a different location for the wasm module
+    #[structopt(long = "mapdir", multiple = true)]
+    mapped_dirs: Vec<String>,
+
+    /// Custom code loader
     #[structopt(
         long = "loader",
         raw(possible_values = "LoaderName::variants()", case_insensitive = "true")
@@ -227,6 +231,31 @@ fn execute_wasm(options: &Run) -> Result<(), String> {
     #[cfg(not(target_os = "windows"))]
     let disable_cache = options.disable_cache;
 
+    let mapped_dirs = {
+        let mut md = vec![];
+        for entry in options.mapped_dirs.iter() {
+            if let &[alias, real_dir] = &entry.split(':').collect::<Vec<&str>>()[..] {
+                let pb = PathBuf::from(&real_dir);
+                if let Ok(pb_metadata) = pb.metadata() {
+                    if !pb_metadata.is_dir() {
+                        return Err(format!(
+                            "\"{}\" exists, but it is not a directory",
+                            &real_dir
+                        ));
+                    }
+                } else {
+                    return Err(format!("Directory \"{}\" does not exist", &real_dir));
+                }
+                md.push((alias.to_string(), pb));
+                continue;
+            }
+            return Err(format!(
+                "Directory mappings must consist of two paths separate by a colon. Found {}",
+                &entry
+            ));
+        }
+        md
+    };
     let wasm_path = &options.path;
 
     let mut wasm_binary: Vec<u8> = read_file_contents(wasm_path).map_err(|err| {
@@ -416,6 +445,9 @@ fn execute_wasm(options: &Run) -> Result<(), String> {
             .instantiate(&import_object)
             .map_err(|e| format!("Can't instantiate module: {:?}", e))?;
 
+        if !mapped_dirs.is_empty() {
+            eprintln!("WARN: mapdir is not implemented for emscripten targets");
+        }
         wasmer_emscripten::run_emscripten_instance(
             &module,
             &mut instance,
@@ -445,6 +477,7 @@ fn execute_wasm(options: &Run) -> Result<(), String> {
                     .map(|(k, v)| format!("{}={}", k, v).into_bytes())
                     .collect(),
                 options.pre_opened_directories.clone(),
+                mapped_dirs,
             );
 
             let instance = module