Merge pull request #957 from wasmerio/feature/add-support-for-new-wasi

Add support for new WASI snapshot, backwards compat too

CHANGELOG.md

@@ -6,6 +6,7 @@
 - [#992](https://github.com/wasmerio/wasmer/pull/992) Updates WAPM version to 0.4.1, fix arguments issue introduced in #990
 - [#990](https://github.com/wasmerio/wasmer/pull/990) Default wasmer CLI to `run`.  Wasmer will now attempt to parse unrecognized command line options as if they were applied to the run command: `wasmer mywasm.wasm --dir=.` now works!
 - [#987](https://github.com/wasmerio/wasmer/pull/987) Fix `runtime-c-api` header files when compiled by gnuc.
+- [#957](https://github.com/wasmerio/wasmer/pull/957) Change the meaning of `wasmer_wasi::is_wasi_module` to detect any type of WASI module, add support for new wasi snapshot_preview1
 
 ## 0.10.2 - 2019-11-18
 

Cargo.toml

@@ -58,8 +58,8 @@ members = [
     "lib/wasi-tests",
     "lib/emscripten-tests",
     "lib/middleware-common-tests",
-    "examples/plugin-for-example",
     "examples/parallel",
+    "examples/plugin-for-example",
     "examples/parallel-guest",
 ]
 

lib/wasi-tests/src/lib.rs

@@ -16,7 +16,13 @@ fn serializing_works() {
         b"GOROOT=$HOME/.cargo/bin".into_iter().cloned().collect(),
     ];
     let wasm_binary = include_bytes!("../wasitests/fd_read.wasm");
-    let import_object = generate_import_object(
+    let module = compile(&wasm_binary[..])
+        .map_err(|e| format!("Can't compile module: {:?}", e))
+        .unwrap();
+
+    let wasi_version = get_wasi_version(&module).expect("WASI module");
+    let import_object = generate_import_object_for_version(
+        wasi_version,
         args.clone(),
         envs.clone(),
         vec![],
@@ -25,9 +31,6 @@ fn serializing_works() {
             std::path::PathBuf::from("wasitests/test_fs/hamlet"),
         )],
     );
-    let module = compile(&wasm_binary[..])
-        .map_err(|e| format!("Can't compile module: {:?}", e))
-        .unwrap();
 
     let state_bytes = {
         let instance = module.instantiate(&import_object).unwrap();

lib/wasi-tests/tests/wasitests/_common.rs

@@ -2,7 +2,7 @@ macro_rules! assert_wasi_output {
     ($file:expr, $name:expr, $po_dir_args: expr, $mapdir_args:expr, $envvar_args:expr, $expected:expr) => {{
         use wasmer_dev_utils::stdio::StdioCapturer;
         use wasmer_runtime_core::{backend::Compiler, Func};
-        use wasmer_wasi::generate_import_object;
+        use wasmer_wasi::{generate_import_object_for_version, get_wasi_version};
 
         #[cfg(feature = "clif")]
         fn get_compiler() -> impl Compiler {
@@ -33,7 +33,15 @@ 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![], $po_dir_args, $mapdir_args);
+        let wasi_version = get_wasi_version(&module).expect("WASI module");
+
+        let import_object = generate_import_object_for_version(
+            wasi_version,
+            vec![],
+            vec![],
+            $po_dir_args,
+            $mapdir_args,
+        );
 
         let instance = module
             .instantiate(&import_object)

lib/wasi/Cargo.toml

@@ -22,4 +22,4 @@ serde = { version = "1", features = ["derive"] }
 wasmer-runtime-core = { path = "../runtime-core", version = "0.10.2" }
 
 [target.'cfg(windows)'.dependencies]
-winapi = "0.3"
+winapi = "0.3"

lib/wasi/src/lib.rs

@@ -12,7 +12,7 @@
 
 //! Wasmer's WASI implementation
 //!
-//! Use `generate_import_object` to create an `ImportObject`.  This `ImportObject`
+//! Use `generate_import_object` to create an [`ImportObject`].  This [`ImportObject`]
 //! can be combined with a module to create an `Instance` which can execute WASI
 //! Wasm functions.
 //!
@@ -37,7 +37,7 @@ use self::syscalls::*;
 use std::ffi::c_void;
 use std::path::PathBuf;
 
-pub use self::utils::is_wasi_module;
+pub use self::utils::{get_wasi_version, is_wasi_module, WasiVersion};
 
 use wasmer_runtime_core::{func, import::ImportObject, imports};
 
@@ -47,7 +47,8 @@ pub struct ExitCode {
     pub code: syscalls::types::__wasi_exitcode_t,
 }
 
-/// Creates a Wasi [`ImportObject`] with [`WasiState`].
+/// Creates a Wasi [`ImportObject`] with [`WasiState`] with the latest snapshot
+/// of WASI.
 pub fn generate_import_object(
     args: Vec<Vec<u8>>,
     envs: Vec<Vec<u8>>,
@@ -79,7 +80,7 @@ pub fn generate_import_object(
     imports! {
         // This generates the wasi state.
         state_gen,
-        "wasi_unstable" => {
+        "wasi_snapshot_preview1" => {
             "args_get" => func!(args_get),
             "args_sizes_get" => func!(args_sizes_get),
             "clock_res_get" => func!(clock_res_get),
@@ -128,3 +129,101 @@ pub fn generate_import_object(
         },
     }
 }
+
+/// Creates a Wasi [`ImportObject`] with [`WasiState`] for the given [`WasiVersion`].
+pub fn generate_import_object_for_version(
+    version: WasiVersion,
+    args: Vec<Vec<u8>>,
+    envs: Vec<Vec<u8>>,
+    preopened_files: Vec<PathBuf>,
+    mapped_dirs: Vec<(String, PathBuf)>,
+) -> ImportObject {
+    match version {
+        WasiVersion::Snapshot0 => {
+            generate_import_object_snapshot0(args, envs, preopened_files, mapped_dirs)
+        }
+        WasiVersion::Snapshot1 => generate_import_object(args, envs, preopened_files, mapped_dirs),
+    }
+}
+
+/// Creates a legacy Wasi [`ImportObject`] with [`WasiState`].
+fn generate_import_object_snapshot0(
+    args: Vec<Vec<u8>>,
+    envs: Vec<Vec<u8>>,
+    preopened_files: Vec<PathBuf>,
+    mapped_dirs: Vec<(String, PathBuf)>,
+) -> ImportObject {
+    let state_gen = move || {
+        // TODO: look into removing all these unnecessary clones
+        fn state_destructor(data: *mut c_void) {
+            unsafe {
+                drop(Box::from_raw(data as *mut WasiState));
+            }
+        }
+        let preopened_files = preopened_files.clone();
+        let mapped_dirs = mapped_dirs.clone();
+        //let wasi_builder = create_wasi_instance();
+
+        let state = Box::new(WasiState {
+            fs: WasiFs::new(&preopened_files, &mapped_dirs).expect("Could not create WASI FS"),
+            args: args.clone(),
+            envs: envs.clone(),
+        });
+
+        (
+            Box::into_raw(state) as *mut c_void,
+            state_destructor as fn(*mut c_void),
+        )
+    };
+    imports! {
+        // This generates the wasi state.
+        state_gen,
+        "wasi_unstable" => {
+            "args_get" => func!(args_get),
+            "args_sizes_get" => func!(args_sizes_get),
+            "clock_res_get" => func!(clock_res_get),
+            "clock_time_get" => func!(clock_time_get),
+            "environ_get" => func!(environ_get),
+            "environ_sizes_get" => func!(environ_sizes_get),
+            "fd_advise" => func!(fd_advise),
+            "fd_allocate" => func!(fd_allocate),
+            "fd_close" => func!(fd_close),
+            "fd_datasync" => func!(fd_datasync),
+            "fd_fdstat_get" => func!(fd_fdstat_get),
+            "fd_fdstat_set_flags" => func!(fd_fdstat_set_flags),
+            "fd_fdstat_set_rights" => func!(fd_fdstat_set_rights),
+            "fd_filestat_get" => func!(legacy::snapshot0::fd_filestat_get),
+            "fd_filestat_set_size" => func!(fd_filestat_set_size),
+            "fd_filestat_set_times" => func!(fd_filestat_set_times),
+            "fd_pread" => func!(fd_pread),
+            "fd_prestat_get" => func!(fd_prestat_get),
+            "fd_prestat_dir_name" => func!(fd_prestat_dir_name),
+            "fd_pwrite" => func!(fd_pwrite),
+            "fd_read" => func!(fd_read),
+            "fd_readdir" => func!(fd_readdir),
+            "fd_renumber" => func!(fd_renumber),
+            "fd_seek" => func!(legacy::snapshot0::fd_seek),
+            "fd_sync" => func!(fd_sync),
+            "fd_tell" => func!(fd_tell),
+            "fd_write" => func!(fd_write),
+            "path_create_directory" => func!(path_create_directory),
+            "path_filestat_get" => func!(legacy::snapshot0::path_filestat_get),
+            "path_filestat_set_times" => func!(path_filestat_set_times),
+            "path_link" => func!(path_link),
+            "path_open" => func!(path_open),
+            "path_readlink" => func!(path_readlink),
+            "path_remove_directory" => func!(path_remove_directory),
+            "path_rename" => func!(path_rename),
+            "path_symlink" => func!(path_symlink),
+            "path_unlink_file" => func!(path_unlink_file),
+            "poll_oneoff" => func!(legacy::snapshot0::poll_oneoff),
+            "proc_exit" => func!(proc_exit),
+            "proc_raise" => func!(proc_raise),
+            "random_get" => func!(random_get),
+            "sched_yield" => func!(sched_yield),
+            "sock_recv" => func!(sock_recv),
+            "sock_send" => func!(sock_send),
+            "sock_shutdown" => func!(sock_shutdown),
+        },
+    }
+}

lib/wasi/src/syscalls/legacy/mod.rs

@@ -0,0 +1,5 @@
+//! These modules provide wrappers and implementations for older version of WASI.
+//!
+//! If you are relying on legacy WASI, please upgrade for the best experience.
+
+pub mod snapshot0;

lib/wasi/src/syscalls/legacy/snapshot0.rs

@@ -0,0 +1,178 @@
+use crate::ptr::{Array, WasmPtr};
+use crate::syscalls;
+use crate::syscalls::types::{self, snapshot0};
+use wasmer_runtime_core::{debug, vm::Ctx};
+
+/// Wrapper around `syscalls::fd_filestat_get` with extra logic to handle the size
+/// difference of `wasi_filestat_t`
+///
+/// WARNING: this function involves saving, clobbering, and restoring unrelated
+/// Wasm memory.  If the memory clobbered by the current syscall is also used by
+/// that syscall, then it may break.
+pub fn fd_filestat_get(
+    ctx: &mut Ctx,
+    fd: types::__wasi_fd_t,
+    buf: WasmPtr<snapshot0::__wasi_filestat_t>,
+) -> types::__wasi_errno_t {
+    let memory = ctx.memory(0);
+
+    // transmute the WasmPtr<T1> into a WasmPtr<T2> where T2 > T1, this will read extra memory.
+    // The edge case of this causing an OOB is not handled, if the new field is OOB, then the entire
+    // memory access will fail.
+    let new_buf: WasmPtr<types::__wasi_filestat_t> = unsafe { std::mem::transmute(buf) };
+
+    // Copy the data including the extra data
+    let new_filestat_setup: types::__wasi_filestat_t =
+        wasi_try!(new_buf.deref(memory)).get().clone();
+
+    // Set up complete, make the call with the pointer that will write to the
+    // struct and some unrelated memory after the struct.
+    let result = syscalls::fd_filestat_get(ctx, fd, new_buf);
+
+    // reborrow memory
+    let memory = ctx.memory(0);
+
+    // get the values written to memory
+    let new_filestat = wasi_try!(new_buf.deref(memory)).get();
+    // translate the new struct into the old struct in host memory
+    let old_stat = snapshot0::__wasi_filestat_t {
+        st_dev: new_filestat.st_dev,
+        st_ino: new_filestat.st_ino,
+        st_filetype: new_filestat.st_filetype,
+        st_nlink: new_filestat.st_nlink as u32,
+        st_size: new_filestat.st_size,
+        st_atim: new_filestat.st_atim,
+        st_mtim: new_filestat.st_mtim,
+        st_ctim: new_filestat.st_ctim,
+    };
+
+    // write back the original values at the pointer's memory locations
+    // (including the memory unrelated to the pointer)
+    wasi_try!(new_buf.deref(memory)).set(new_filestat_setup);
+
+    // Now that this memory is back as it was, write the translated filestat
+    // into memory leaving it as it should be
+    wasi_try!(buf.deref(memory)).set(old_stat);
+
+    result
+}
+
+/// Wrapper around `syscalls::path_filestat_get` with extra logic to handle the size
+/// difference of `wasi_filestat_t`
+pub fn path_filestat_get(
+    ctx: &mut Ctx,
+    fd: types::__wasi_fd_t,
+    flags: types::__wasi_lookupflags_t,
+    path: WasmPtr<u8, Array>,
+    path_len: u32,
+    buf: WasmPtr<snapshot0::__wasi_filestat_t>,
+) -> types::__wasi_errno_t {
+    // see `fd_filestat_get` in this file for an explanation of this strange behavior
+    let memory = ctx.memory(0);
+
+    let new_buf: WasmPtr<types::__wasi_filestat_t> = unsafe { std::mem::transmute(buf) };
+    let new_filestat_setup: types::__wasi_filestat_t =
+        wasi_try!(new_buf.deref(memory)).get().clone();
+
+    let result = syscalls::path_filestat_get(ctx, fd, flags, path, path_len, new_buf);
+
+    let memory = ctx.memory(0);
+    let new_filestat = wasi_try!(new_buf.deref(memory)).get();
+    let old_stat = snapshot0::__wasi_filestat_t {
+        st_dev: new_filestat.st_dev,
+        st_ino: new_filestat.st_ino,
+        st_filetype: new_filestat.st_filetype,
+        st_nlink: new_filestat.st_nlink as u32,
+        st_size: new_filestat.st_size,
+        st_atim: new_filestat.st_atim,
+        st_mtim: new_filestat.st_mtim,
+        st_ctim: new_filestat.st_ctim,
+    };
+
+    wasi_try!(new_buf.deref(memory)).set(new_filestat_setup);
+    wasi_try!(buf.deref(memory)).set(old_stat);
+
+    result
+}
+
+/// Wrapper around `syscalls::fd_seek` with extra logic to remap the values
+/// of `__wasi_whence_t`
+pub fn fd_seek(
+    ctx: &mut Ctx,
+    fd: types::__wasi_fd_t,
+    offset: types::__wasi_filedelta_t,
+    whence: snapshot0::__wasi_whence_t,
+    newoffset: WasmPtr<types::__wasi_filesize_t>,
+) -> types::__wasi_errno_t {
+    let new_whence = match whence {
+        snapshot0::__WASI_WHENCE_CUR => types::__WASI_WHENCE_CUR,
+        snapshot0::__WASI_WHENCE_END => types::__WASI_WHENCE_END,
+        snapshot0::__WASI_WHENCE_SET => types::__WASI_WHENCE_SET,
+        // if it's invalid, let the new fd_seek handle it
+        _ => whence,
+    };
+    syscalls::fd_seek(ctx, fd, offset, new_whence, newoffset)
+}
+
+/// Wrapper around `syscalls::poll_oneoff` with extra logic to add the removed
+/// userdata field back
+pub fn poll_oneoff(
+    ctx: &mut Ctx,
+    in_: WasmPtr<snapshot0::__wasi_subscription_t, Array>,
+    out_: WasmPtr<types::__wasi_event_t, Array>,
+    nsubscriptions: u32,
+    nevents: WasmPtr<u32>,
+) -> types::__wasi_errno_t {
+    // in this case the new type is smaller than the old type, so it all fits into memory,
+    // we just need to readjust and copy it
+
+    // we start by adjusting `in_` into a format that the new code can understand
+    let memory = ctx.memory(0);
+    let mut in_origs: Vec<snapshot0::__wasi_subscription_t> = vec![];
+    for in_sub in wasi_try!(in_.deref(memory, 0, nsubscriptions)) {
+        in_origs.push(in_sub.get().clone());
+    }
+
+    // get a pointer to the smaller new type
+    let in_new_type_ptr: WasmPtr<types::__wasi_subscription_t, Array> =
+        unsafe { std::mem::transmute(in_) };
+
+    for (in_sub_new, orig) in wasi_try!(in_new_type_ptr.deref(memory, 0, nsubscriptions))
+        .iter()
+        .zip(in_origs.iter())
+    {
+        in_sub_new.set(types::__wasi_subscription_t {
+            userdata: orig.userdata,
+            type_: orig.type_,
+            u: if orig.type_ == types::__WASI_EVENTTYPE_CLOCK {
+                types::__wasi_subscription_u {
+                    clock: types::__wasi_subscription_clock_t {
+                        clock_id: unsafe { orig.u.clock.clock_id },
+                        timeout: unsafe { orig.u.clock.timeout },
+                        precision: unsafe { orig.u.clock.precision },
+                        flags: unsafe { orig.u.clock.flags },
+                    },
+                }
+            } else {
+                types::__wasi_subscription_u {
+                    fd_readwrite: unsafe { orig.u.fd_readwrite },
+                }
+            },
+        });
+    }
+
+    // make the call
+    let result = syscalls::poll_oneoff(ctx, in_new_type_ptr, out_, nsubscriptions, nevents);
+
+    // replace the old values of in, in case the calling code reuses the memory
+    let memory = ctx.memory(0);
+
+    for (in_sub, orig) in wasi_try!(in_.deref(memory, 0, nsubscriptions))
+        .iter()
+        .zip(in_origs.into_iter())
+    {
+        in_sub.set(orig);
+    }
+
+    result
+}

lib/wasi/src/syscalls/mod.rs

@@ -5,6 +5,8 @@ pub mod unix;
 #[cfg(any(target_os = "windows"))]
 pub mod windows;
 
+pub mod legacy;
+
 use self::types::*;
 use crate::{
     ptr::{Array, WasmPtr},

lib/wasi/src/syscalls/types.rs

@@ -416,7 +416,7 @@ pub struct __wasi_iovec_t {
 
 unsafe impl ValueType for __wasi_iovec_t {}
 
-pub type __wasi_linkcount_t = u32;
+pub type __wasi_linkcount_t = u64;
 
 pub type __wasi_lookupflags_t = u32;
 pub const __WASI_LOOKUP_SYMLINK_FOLLOW: u32 = 1 << 0;
@@ -559,7 +559,6 @@ pub const __WASI_SUBSCRIPTION_CLOCK_ABSTIME: u16 = 1 << 0;
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 #[repr(C)]
 pub struct __wasi_subscription_clock_t {
-    pub userdata: __wasi_userdata_t,
     pub clock_id: __wasi_clockid_t,
     pub timeout: __wasi_timestamp_t,
     pub precision: __wasi_timestamp_t,
@@ -575,8 +574,8 @@ pub struct __wasi_subscription_fs_readwrite_t {
 #[derive(Copy, Clone)]
 #[repr(C)]
 pub union __wasi_subscription_u {
-    clock: __wasi_subscription_clock_t,
-    fd_readwrite: __wasi_subscription_fs_readwrite_t,
+    pub clock: __wasi_subscription_clock_t,
+    pub fd_readwrite: __wasi_subscription_fs_readwrite_t,
 }
 
 #[derive(Copy, Clone)]
@@ -698,6 +697,107 @@ pub type __wasi_timestamp_t = u64;
 pub type __wasi_userdata_t = u64;
 
 pub type __wasi_whence_t = u8;
-pub const __WASI_WHENCE_CUR: u8 = 0;
-pub const __WASI_WHENCE_END: u8 = 1;
-pub const __WASI_WHENCE_SET: u8 = 2;
+pub const __WASI_WHENCE_SET: u8 = 0;
+pub const __WASI_WHENCE_CUR: u8 = 1;
+pub const __WASI_WHENCE_END: u8 = 2;
+
+pub mod snapshot0 {
+    use serde::{Deserialize, Serialize};
+    pub type __wasi_linkcount_t = u32;
+    use wasmer_runtime_core::types::ValueType;
+
+    #[derive(Debug, Copy, Clone, PartialEq, Eq)]
+    #[repr(C)]
+    pub struct __wasi_subscription_clock_t {
+        pub userdata: super::__wasi_userdata_t,
+        pub clock_id: super::__wasi_clockid_t,
+        pub timeout: super::__wasi_timestamp_t,
+        pub precision: super::__wasi_timestamp_t,
+        pub flags: super::__wasi_subclockflags_t,
+    }
+
+    #[derive(Copy, Clone)]
+    #[repr(C)]
+    pub union __wasi_subscription_u {
+        pub clock: __wasi_subscription_clock_t,
+        pub fd_readwrite: super::__wasi_subscription_fs_readwrite_t,
+    }
+
+    #[derive(Copy, Clone)]
+    #[repr(C)]
+    pub struct __wasi_subscription_t {
+        pub userdata: super::__wasi_userdata_t,
+        pub type_: super::__wasi_eventtype_t,
+        pub u: __wasi_subscription_u,
+    }
+
+    unsafe impl ValueType for __wasi_subscription_t {}
+
+    pub type __wasi_whence_t = u8;
+    pub const __WASI_WHENCE_CUR: u8 = 0;
+    pub const __WASI_WHENCE_END: u8 = 1;
+    pub const __WASI_WHENCE_SET: u8 = 2;
+
+    #[derive(Copy, Clone, PartialEq, Eq, Serialize, Deserialize)]
+    #[repr(C)]
+    pub struct __wasi_filestat_t {
+        pub st_dev: super::__wasi_device_t,
+        pub st_ino: super::__wasi_inode_t,
+        pub st_filetype: super::__wasi_filetype_t,
+        pub st_nlink: __wasi_linkcount_t,
+        pub st_size: super::__wasi_filesize_t,
+        pub st_atim: super::__wasi_timestamp_t,
+        pub st_mtim: super::__wasi_timestamp_t,
+        pub st_ctim: super::__wasi_timestamp_t,
+    }
+
+    unsafe impl ValueType for __wasi_filestat_t {}
+
+    impl std::fmt::Debug for __wasi_filestat_t {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            let convert_ts_into_time_string = |ts| {
+                let tspec =
+                    time::Timespec::new(ts as i64 / 1_000_000_000, (ts % 1_000_000_000) as i32);
+                let tm = time::at(tspec);
+                let out_time = tm.rfc822();
+                format!("{} ({})", out_time, ts)
+            };
+            f.debug_struct("__wasi_filestat_t")
+                .field("st_dev", &self.st_dev)
+                .field("st_ino", &self.st_ino)
+                .field(
+                    "st_filetype",
+                    &format!(
+                        "{} ({})",
+                        super::wasi_filetype_to_name(self.st_filetype),
+                        self.st_filetype,
+                    ),
+                )
+                .field("st_nlink", &self.st_nlink)
+                .field("st_size", &self.st_size)
+                .field("st_atim", &convert_ts_into_time_string(self.st_atim))
+                .field("st_mtim", &convert_ts_into_time_string(self.st_mtim))
+                .field("st_ctim", &convert_ts_into_time_string(self.st_ctim))
+                .finish()
+        }
+    }
+
+    impl std::fmt::Debug for __wasi_subscription_t {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            f.debug_struct("__wasi_subscription_t")
+                .field("userdata", &self.userdata)
+                .field("type", &super::eventtype_to_str(self.type_))
+                .field(
+                    "u",
+                    match self.type_ {
+                        super::__WASI_EVENTTYPE_CLOCK => unsafe { &self.u.clock },
+                        super::__WASI_EVENTTYPE_FD_READ | super::__WASI_EVENTTYPE_FD_WRITE => unsafe {
+                            &self.u.fd_readwrite
+                        },
+                        _ => &"INVALID EVENTTYPE",
+                    },
+                )
+                .finish()
+        }
+    }
+}

lib/wasi/src/utils.rs

@@ -1,18 +1,41 @@
 use wasmer_runtime_core::module::Module;
 
-/// Check if a provided module is compiled with WASI support
+#[allow(dead_code)]
+/// Check if a provided module is compiled for some version of WASI.
+/// Use [`get_wasi_version`] to find out which version of WASI the module is.
 pub fn is_wasi_module(module: &Module) -> bool {
-    if module.info().imported_functions.is_empty() {
-        return false;
-    }
-    for (_, import_name) in &module.info().imported_functions {
-        let namespace = module
-            .info()
-            .namespace_table
-            .get(import_name.namespace_index);
-        if namespace != "wasi_unstable" {
-            return false;
-        }
-    }
-    true
+    get_wasi_version(module).is_some()
+}
+
+/// The version of WASI.  This is determined by the namespace string
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum WasiVersion {
+    /// "wasi_unstable"
+    Snapshot0,
+    /// "wasi_snapshot_preview1"
+    Snapshot1,
+}
+
+/// Detect the version of WASI being used from the namespace
+pub fn get_wasi_version(module: &Module) -> Option<WasiVersion> {
+    let mut import_iter = module
+        .info()
+        .imported_functions
+        .iter()
+        .map(|(_, import_name)| import_name.namespace_index);
+
+    // returns None if empty
+    let first = import_iter.next()?;
+    if import_iter.all(|idx| idx == first) {
+        // once we know that all the namespaces are the same, we can use it to
+        // detect which version of WASI this is
+        match module.info().namespace_table.get(first) {
+            "wasi_unstable" => Some(WasiVersion::Snapshot0),
+            "wasi_snapshot_preview1" => Some(WasiVersion::Snapshot1),
+            _ => None,
+        }
+    } else {
+        // not all funcs have the same namespace, therefore it's not WASI
+        None
+    }
 }

src/bin/wasmer.rs

@@ -26,7 +26,7 @@ use wasmer_clif_backend::CraneliftCompiler;
 use wasmer_llvm_backend::{LLVMCompiler, LLVMOptions};
 use wasmer_runtime::{
     cache::{Cache as BaseCache, FileSystemCache, WasmHash},
-    Func, Value, VERSION,
+    Value, VERSION,
 };
 #[cfg(feature = "managed")]
 use wasmer_runtime_core::tiering::{run_tiering, InteractiveShellContext, ShellExitOperation};
@@ -41,25 +41,6 @@ use wasmer_singlepass_backend::SinglePassCompiler;
 #[cfg(feature = "wasi")]
 use wasmer_wasi;
 
-// stub module to make conditional compilation happy
-#[cfg(not(feature = "wasi"))]
-mod wasmer_wasi {
-    use wasmer_runtime_core::{import::ImportObject, module::Module};
-
-    pub fn is_wasi_module(_module: &Module) -> bool {
-        false
-    }
-
-    pub fn generate_import_object(
-        _args: Vec<Vec<u8>>,
-        _envs: Vec<Vec<u8>>,
-        _preopened_files: Vec<std::path::PathBuf>,
-        _mapped_dirs: Vec<(String, std::path::PathBuf)>,
-    ) -> ImportObject {
-        unimplemented!()
-    }
-}
-
 #[derive(Debug, StructOpt)]
 #[structopt(name = "wasmer", about = "Wasm execution runtime.", author)]
 /// The options for the wasmer Command Line Interface
@@ -335,6 +316,7 @@ fn get_mapped_dirs(input: &[String]) -> Result<Vec<(String, PathBuf)>, String> {
     Ok(md)
 }
 
+#[cfg(feature = "wasi")]
 fn get_env_var_args(input: &[String]) -> Result<Vec<(&str, &str)>, String> {
     let mut ev = vec![];
     for entry in input.iter() {
@@ -350,11 +332,111 @@ fn get_env_var_args(input: &[String]) -> Result<Vec<(&str, &str)>, String> {
     Ok(ev)
 }
 
+/// Helper function for `execute_wasm` (the `Run` command)
+#[cfg(feature = "wasi")]
+fn execute_wasi(
+    wasi_version: wasmer_wasi::WasiVersion,
+    options: &Run,
+    env_vars: Vec<(&str, &str)>,
+    module: wasmer_runtime_core::Module,
+    mapped_dirs: Vec<(String, PathBuf)>,
+) -> Result<(), String> {
+    let args = if let Some(cn) = &options.command_name {
+        [cn.clone()]
+    } else {
+        [options.path.to_str().unwrap().to_owned()]
+    }
+    .iter()
+    .chain(options.args.iter())
+    .cloned()
+    .map(|arg| arg.into_bytes())
+    .collect();
+    let envs = env_vars
+        .into_iter()
+        .map(|(k, v)| format!("{}={}", k, v).into_bytes())
+        .collect();
+    let preopened_files = options.pre_opened_directories.clone();
+
+    let import_object = wasmer_wasi::generate_import_object_for_version(
+        wasi_version,
+        args,
+        envs,
+        preopened_files,
+        mapped_dirs,
+    );
+
+    #[allow(unused_mut)] // mut used in feature
+    let mut instance = module
+        .instantiate(&import_object)
+        .map_err(|e| format!("Can't instantiate WASI module: {:?}", e))?;
+
+    let start: wasmer_runtime::Func<(), ()> =
+        instance.func("_start").map_err(|e| format!("{:?}", e))?;
+
+    #[cfg(feature = "managed")]
+    {
+        let start_raw: extern "C" fn(&mut wasmer_runtime_core::vm::Ctx) =
+            unsafe { ::std::mem::transmute(start.get_vm_func()) };
+
+        unsafe {
+            run_tiering(
+                module.info(),
+                &wasm_binary,
+                if let Some(ref path) = options.resume {
+                    let mut f = File::open(path).unwrap();
+                    let mut out: Vec<u8> = vec![];
+                    f.read_to_end(&mut out).unwrap();
+                    Some(
+                        wasmer_runtime_core::state::InstanceImage::from_bytes(&out)
+                            .expect("failed to decode image"),
+                    )
+                } else {
+                    None
+                },
+                &import_object,
+                start_raw,
+                &mut instance,
+                options
+                    .optimized_backends
+                    .iter()
+                    .map(|&backend| -> Box<dyn Fn() -> Box<dyn Compiler> + Send> {
+                        Box::new(move || get_compiler_by_backend(backend).unwrap())
+                    })
+                    .collect(),
+                interactive_shell,
+            )?
+        };
+    }
+
+    #[cfg(not(feature = "managed"))]
+    {
+        use wasmer_runtime::error::RuntimeError;
+        let result = start.call();
+
+        if let Err(ref err) = result {
+            match err {
+                RuntimeError::Trap { msg } => return Err(format!("wasm trap occured: {}", msg)),
+                #[cfg(feature = "wasi")]
+                RuntimeError::Error { data } => {
+                    if let Some(error_code) = data.downcast_ref::<wasmer_wasi::ExitCode>() {
+                        std::process::exit(error_code.code as i32)
+                    }
+                }
+                #[cfg(not(feature = "wasi"))]
+                RuntimeError::Error { .. } => (),
+            }
+            return Err(format!("error: {:?}", err));
+        }
+    }
+    Ok(())
+}
+
 /// Execute a wasm/wat file
 fn execute_wasm(options: &Run) -> Result<(), String> {
     let disable_cache = options.disable_cache;
 
     let mapped_dirs = get_mapped_dirs(&options.mapped_dirs[..])?;
+    #[cfg(feature = "wasi")]
     let env_vars = get_env_var_args(&options.env_vars[..])?;
     let wasm_path = &options.path;
 
@@ -595,90 +677,22 @@ fn execute_wasm(options: &Run) -> Result<(), String> {
         )
         .map_err(|e| format!("{:?}", e))?;
     } else {
-        if cfg!(feature = "wasi") && wasmer_wasi::is_wasi_module(&module) {
-            let import_object = wasmer_wasi::generate_import_object(
-                if let Some(cn) = &options.command_name {
-                    [cn.clone()]
-                } else {
-                    [options.path.to_str().unwrap().to_owned()]
-                }
-                .iter()
-                .chain(options.args.iter())
-                .cloned()
-                .map(|arg| arg.into_bytes())
-                .collect(),
-                env_vars
-                    .into_iter()
-                    .map(|(k, v)| format!("{}={}", k, v).into_bytes())
-                    .collect(),
-                options.pre_opened_directories.clone(),
+        #[cfg(feature = "wasi")]
+        let wasi_version = wasmer_wasi::get_wasi_version(&module);
+        #[cfg(feature = "wasi")]
+        let is_wasi = wasi_version.is_some();
+        #[cfg(not(feature = "wasi"))]
+        let is_wasi = false;
+
+        if is_wasi {
+            #[cfg(feature = "wasi")]
+            execute_wasi(
+                wasi_version.unwrap(),
+                options,
+                env_vars,
+                module,
                 mapped_dirs,
-            );
-
-            #[allow(unused_mut)] // mut used in feature
-            let mut instance = module
-                .instantiate(&import_object)
-                .map_err(|e| format!("Can't instantiate WASI module: {:?}", e))?;
-
-            let start: Func<(), ()> = instance.func("_start").map_err(|e| format!("{:?}", e))?;
-
-            #[cfg(feature = "managed")]
-            {
-                let start_raw: extern "C" fn(&mut wasmer_runtime_core::vm::Ctx) =
-                    unsafe { ::std::mem::transmute(start.get_vm_func()) };
-
-                unsafe {
-                    run_tiering(
-                        module.info(),
-                        &wasm_binary,
-                        if let Some(ref path) = options.resume {
-                            let mut f = File::open(path).unwrap();
-                            let mut out: Vec<u8> = vec![];
-                            f.read_to_end(&mut out).unwrap();
-                            Some(
-                                wasmer_runtime_core::state::InstanceImage::from_bytes(&out)
-                                    .expect("failed to decode image"),
-                            )
-                        } else {
-                            None
-                        },
-                        &import_object,
-                        start_raw,
-                        &mut instance,
-                        options
-                            .optimized_backends
-                            .iter()
-                            .map(|&backend| -> Box<dyn Fn() -> Box<dyn Compiler> + Send> {
-                                Box::new(move || get_compiler_by_backend(backend).unwrap())
-                            })
-                            .collect(),
-                        interactive_shell,
-                    )?
-                };
-            }
-
-            #[cfg(not(feature = "managed"))]
-            {
-                use wasmer_runtime::error::RuntimeError;
-                let result = start.call();
-
-                if let Err(ref err) = result {
-                    match err {
-                        RuntimeError::Trap { msg } => {
-                            return Err(format!("wasm trap occured: {}", msg))
-                        }
-                        #[cfg(feature = "wasi")]
-                        RuntimeError::Error { data } => {
-                            if let Some(error_code) = data.downcast_ref::<wasmer_wasi::ExitCode>() {
-                                std::process::exit(error_code.code as i32)
-                            }
-                        }
-                        #[cfg(not(feature = "wasi"))]
-                        RuntimeError::Error { .. } => (),
-                    }
-                    return Err(format!("error: {:?}", err));
-                }
-            }
+            )?;
         } else {
             let import_object = wasmer_runtime_core::import::ImportObject::new();
             let instance = module