Merge #1213

1213: Fixed WASI isatty r=syrusakbary a=syrusakbary

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# Description

Current WASI implementation returns a wrong response when libc `isatty` is used for `stdin`, `stdout` or `stderr`.

This PR fixes it.

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# Review

- [x] Add a short description of the the change to the CHANGELOG.md file


Co-authored-by: Syrus <me@syrusakbary.com>
Co-authored-by: Syrus Akbary <me@syrusakbary.com>

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## **[Unreleased]**
 
+- [#1213](https://github.com/wasmerio/wasmer/pull/1213) Fixed WASI `fdstat` to detect `isatty` properly.
 - [#1192](https://github.com/wasmerio/wasmer/pull/1192) Use `ExceptionCode` for error representation.
 - [#1191](https://github.com/wasmerio/wasmer/pull/1191) Fix singlepass miscompilation on `Operator::CallIndirect`.
 - [#1180](https://github.com/wasmerio/wasmer/pull/1180) Fix compilation for target `x86_64-unknown-linux-musl`.

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

@@ -0,0 +1,15 @@
+// !!! THIS IS A GENERATED FILE !!!
+// ANY MANUAL EDITS MAY BE OVERWRITTEN AT ANY TIME
+// Files autogenerated with cargo build (build/wasitests.rs).
+
+#[test]
+fn test_isatty() {
+    assert_wasi_output!(
+        "../../wasitests/isatty.wasm",
+        "isatty",
+        vec![],
+        vec![],
+        vec![],
+        "../../wasitests/isatty.out"
+    );
+}

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

@@ -18,6 +18,7 @@ mod file_metadata;
 mod fs_sandbox_test;
 mod fseek;
 mod hello;
+mod isatty;
 mod mapdir;
 mod path_link;
 mod path_rename;

lib/wasi-tests/wasitests/isatty.out

@@ -0,0 +1,3 @@
+stdin: 1
+stdout: 1
+stderr: 1

lib/wasi-tests/wasitests/isatty.rs

@@ -0,0 +1,20 @@
+// We don't have access to libc, so we just use isatty
+// as an external function
+// use libc::isatty;
+
+extern "C" {
+    pub fn isatty(fd: i32) -> i32;
+}
+
+fn main() {
+    #[cfg(target = "wasi")] {
+        println!("stdin: {}", unsafe { isatty(0) });
+        println!("stdout: {}", unsafe { isatty(1) });
+        println!("stderr: {}", unsafe { isatty(2) });
+    }
+    #[cfg(not(target = "wasi"))] {
+        println!("stdin: 1");
+        println!("stdout: 1");
+        println!("stderr: 1");
+    }
+}

lib/wasi/src/state/mod.rs

@@ -1045,12 +1045,28 @@ impl WasiFs {
 
     pub fn fdstat(&self, fd: __wasi_fd_t) -> Result<__wasi_fdstat_t, __wasi_errno_t> {
         match fd {
-            __WASI_STDOUT_FILENO => {
+            __WASI_STDIN_FILENO => {
                 return Ok(__wasi_fdstat_t {
                     fs_filetype: __WASI_FILETYPE_CHARACTER_DEVICE,
                     fs_flags: 0,
-                    fs_rights_base: ALL_RIGHTS,
-                    fs_rights_inheriting: ALL_RIGHTS,
+                    fs_rights_base: STDIN_DEFAULT_RIGHTS,
+                    fs_rights_inheriting: 0,
+                })
+            }
+            __WASI_STDOUT_FILENO => {
+                return Ok(__wasi_fdstat_t {
+                    fs_filetype: __WASI_FILETYPE_CHARACTER_DEVICE,
+                    fs_flags: __WASI_FDFLAG_APPEND,
+                    fs_rights_base: STDOUT_DEFAULT_RIGHTS,
+                    fs_rights_inheriting: 0,
+                })
+            }
+            __WASI_STDERR_FILENO => {
+                return Ok(__wasi_fdstat_t {
+                    fs_filetype: __WASI_FILETYPE_CHARACTER_DEVICE,
+                    fs_flags: __WASI_FDFLAG_APPEND,
+                    fs_rights_base: STDERR_DEFAULT_RIGHTS,
+                    fs_rights_inheriting: 0,
                 })
             }
             _ => (),

lib/wasi/src/syscalls/mod.rs

@@ -1221,7 +1221,14 @@ pub fn fd_write(
     iovs_len: u32,
     nwritten: WasmPtr<u32>,
 ) -> __wasi_errno_t {
-    debug!("wasi::fd_write: fd={}", fd);
+    // If we are writing to stdout or stderr
+    // we skip debug to not pollute the stdout/err
+    // and do debugging happily after :)
+    if fd != __WASI_STDOUT_FILENO && fd != __WASI_STDERR_FILENO {
+        debug!("wasi::fd_write: fd={}", fd);
+    } else {
+        trace!("wasi::fd_write: fd={}", fd);
+    }
     let (memory, state) = get_memory_and_wasi_state(ctx, 0);
     let iovs_arr_cell = wasi_try!(iovs.deref(memory, 0, iovs_len));
     let nwritten_cell = wasi_try!(nwritten.deref(memory));