[WasmFS] Stub ioctl()/terminal support (#16677)

We don't have TTY support in emscripten anyhow, so most of this just
does nothing. We also do not yet have a concept of TTYs in wasmfs,
so just recognize stdin/out/err as such. This is enough for basic things,
gets some tests passing, and is almost at parity with the old FS (it had
the ability to create new terminals and mark them as such).

Author: kripken

system/lib/standalone/standalone.c

@@ -90,11 +90,11 @@ long __syscall_openat(int dirfd, const char* path, long flags, ...) {
   return -EPERM;
 }
 
-int __syscall_ioctl(int fd, int op, ...) {
+__attribute__((__weak__)) int __syscall_ioctl(int fd, int op, ...) {
   return -ENOSYS;
 }
 
-long __syscall_fcntl64(long fd, long cmd, ...) {
+__attribute__((__weak__)) long __syscall_fcntl64(long fd, long cmd, ...) {
   return -ENOSYS;
 }
 

system/lib/wasmfs/syscalls.cpp

@@ -14,19 +14,20 @@
 #include <poll.h>
 #include <stdarg.h>
 #include <stdlib.h>
+#include <sys/ioctl.h>
 #include <sys/stat.h>
 #include <syscall_arch.h>
 #include <unistd.h>
 #include <utility>
 #include <vector>
 #include <wasi/api.h>
-#include <syscall_arch.h>
 
 #include "backend.h"
 #include "file.h"
 #include "file_table.h"
 #include "paths.h"
 #include "pipe_backend.h"
+#include "streams.h"
 #include "wasmfs.h"
 
 // File permission macros for wasmfs.
@@ -1118,6 +1119,48 @@ int __syscall_ftruncate64(int fd, uint64_t size) {
   return ret;
 }
 
+static bool isTTY(std::shared_ptr<File>& file) {
+  // TODO: Full TTY support. For now, just see stdin/out/err as terminals and
+  //       nothing else.
+  return file == StdinFile::getSingleton() ||
+         file == StdoutFile::getSingleton() ||
+         file == StderrFile::getSingleton();
+}
+
+int __syscall_ioctl(int fd, int request, ...) {
+  auto openFile = wasmFS.getFileTable().locked().getEntry(fd);
+  if (!openFile) {
+    return -EBADF;
+  }
+  if (!isTTY(openFile->locked().getFile())) {
+    return -ENOTTY;
+  }
+  // TODO: Full TTY support. For now this is limited, and matches the old FS.
+  switch (request) {
+    case TCGETA:
+    case TCGETS:
+    case TCSETA:
+    case TCSETAW:
+    case TCSETAF:
+    case TCSETS:
+    case TCSETSW:
+    case TCSETSF:
+    case TIOCGWINSZ:
+    case TIOCSWINSZ: {
+      // TTY operations that we do nothing for anyhow can just be ignored.
+      return -0;
+    }
+    case TIOCGPGRP:
+    case TIOCSPGRP: {
+      // TODO We should get/set the group number here.
+      return -EINVAL;
+    }
+    default: {
+      abort();
+    }
+  }
+}
+
 int __syscall_pipe(intptr_t fd) {
   auto* fds = (__wasi_fd_t*)fd;
 

tests/test_other.py

@@ -8163,6 +8163,7 @@ def test_autotools_shared_check(self):
     out = self.run_process([EMCC, '--help'], stdout=PIPE).stdout
     assert re.search(expected, out)
 
+  @also_with_wasmfs
   def test_ioctl_window_size(self):
       self.do_other_test('test_ioctl_window_size.cpp')
 
@@ -10283,6 +10284,7 @@ def test_errno_type(self):
 ''')
     self.run_process([EMCC, 'errno_type.c'])
 
+  @also_with_wasmfs
   def test_standalone_syscalls(self):
     self.run_process([EMXX, test_file('other/test_standalone_syscalls.cpp'), '-o', 'test.wasm'])
     expected = read_file(test_file('other/test_standalone_syscalls.out'))