feat(go-sdk): add wasi hostcalls used by the Go SDK

include/proxy-wasm/exports.h

@@ -139,10 +139,13 @@ Word wasi_unstable_fd_read(Word, Word, Word, Word);
 Word wasi_unstable_fd_seek(Word, int64_t, Word, Word);
 Word wasi_unstable_fd_close(Word);
 Word wasi_unstable_fd_fdstat_get(Word fd, Word statOut);
+Word wasi_unstable_fd_fdstat_set_flags(Word fd, Word flags);
 Word wasi_unstable_environ_get(Word, Word);
 Word wasi_unstable_environ_sizes_get(Word count_ptr, Word buf_size_ptr);
 Word wasi_unstable_args_get(Word argc_ptr, Word argv_buf_size_ptr);
 Word wasi_unstable_args_sizes_get(Word argc_ptr, Word argv_buf_size_ptr);
+Word wasi_unstable_sched_yield();
+Word wasi_unstable_poll_oneoff(Word in, Word out, Word nsubscriptions, Word nevents);
 void wasi_unstable_proc_exit(Word);
 Word wasi_unstable_clock_time_get(Word, uint64_t, Word);
 Word wasi_unstable_random_get(Word, Word);
@@ -170,9 +173,10 @@ void emscripten_notify_memory_growth(Word);
       _f(continue_stream) _f(close_stream) _f(get_log_level)
 
 #define FOR_ALL_WASI_FUNCTIONS(_f)                                                                 \
-  _f(fd_write) _f(fd_read) _f(fd_seek) _f(fd_close) _f(fd_fdstat_get) _f(environ_get)              \
-      _f(environ_sizes_get) _f(args_get) _f(args_sizes_get) _f(clock_time_get) _f(random_get)      \
-          _f(proc_exit) _f(path_open) _f(fd_prestat_get) _f(fd_prestat_dir_name)
+  _f(fd_write) _f(fd_read) _f(fd_seek) _f(fd_close) _f(fd_fdstat_get) _f(fd_fdstat_set_flags)      \
+      _f(environ_get) _f(environ_sizes_get) _f(args_get) _f(args_sizes_get) _f(clock_time_get)     \
+          _f(random_get) _f(sched_yield) _f(poll_oneoff) _f(proc_exit) _f(path_open)               \
+              _f(fd_prestat_get) _f(fd_prestat_dir_name)
 
 // Helpers to generate a stub to pass to VM, in place of a restricted proxy-wasm capability.
 #define _CREATE_PROXY_WASM_STUB(_fn)                                                               \

src/exports.cc

@@ -646,6 +646,9 @@ Word grpc_send(Word token, Word message_ptr, Word message_size, Word end_stream)
   return context->grpcSend(token, message.value(), end_stream != 0U);
 }
 
+// WASIp1 typings in comments sourced from
+// https://github.com/WebAssembly/wasi-libc/blob/446cb3f1aa21f9b1a1eab372f82d65d19003e924/libc-bottom-half/headers/public/wasi/api.h
+
 // __wasi_errno_t path_open(__wasi_fd_t fd, __wasi_lookupflags_t dirflags, const char *path,
 // size_t path_len, __wasi_oflags_t oflags, __wasi_rights_t fs_rights_base, __wasi_rights_t
 // fs_rights_inheriting, __wasi_fdflags_t fdflags, __wasi_fd_t *retptr0)
@@ -776,6 +779,13 @@ Word wasi_unstable_fd_fdstat_get(Word fd, Word statOut) {
   return 0; // __WASI_ESUCCESS
 }
 
+// __wasi_errno_t __wasi_fd_fdstat_set_flags(__wasi_fd_t fd, __wasi_fdflags_t flags)
+Word wasi_unstable_fd_fdstat_set_flags(Word /*fd*/, Word /*flags*/) {
+  // Flags that can be specified: append, dsync, nonblock, rsync, and sync. Proxy-wasm only supports
+  // STDOUT and STDERR, but none of these flags have any effect in Proxy-Wasm.
+  return 52; // __WASI_ERRNO_ENOSYS
+}
+
 // __wasi_errno_t __wasi_environ_get(char **environ, char *environ_buf);
 Word wasi_unstable_environ_get(Word environ_array_ptr, Word environ_buf) {
   auto *context = contextOrEffectiveContext();
@@ -879,6 +889,21 @@ Word wasi_unstable_random_get(Word result_buf_ptr, Word buf_len) {
   return 0; // __WASI_ESUCCESS
 }
 
+// __wasi_errno_t __wasi_sched_yield()
+Word wasi_unstable_sched_yield() {
+  // Per POSIX man pages, it is valid to return success if the calling thread is the only thread in
+  // the highest priority list. This is vacuously true for wasm without threads. There are no valid
+  // error cases defined.
+  return 0; // __WASI_ESUCCESS
+}
+
+// __wasi_errno_t __wasi_poll_oneoff(const __wasi_subscription_t *in, __wasi_event_t *out,
+// __wasi_size_t nsubscriptions, __wasi_size_t *nevents)
+Word wasi_unstable_poll_oneoff(Word /*in*/, Word /*out*/, Word /*nsubscriptions*/,
+                               Word /*nevents_ptr*/) {
+  return 52; // __WASI_ERRNO_ENOSYS
+}
+
 // void __wasi_proc_exit(__wasi_exitcode_t rval);
 void wasi_unstable_proc_exit(Word /*exit_code*/) {
   auto *context = contextOrEffectiveContext();

src/wasm.cc

@@ -394,7 +394,10 @@ void WasmBase::startVm(ContextBase *root_context) {
              // time
              "wasi_unstable.clock_time_get", "wasi_snapshot_preview1.clock_time_get",
              // random
-             "wasi_unstable.random_get", "wasi_snapshot_preview1.random_get"});
+             "wasi_unstable.random_get", "wasi_snapshot_preview1.random_get",
+             // Go runtime initialization
+             "wasi_unstable.fd_fdstat_get", "wasi_snapshot_preview1.fd_fdstat_get",
+             "wasi_unstable.fd_fdstat_set_flags", "wasi_snapshot_preview1.fd_fdstat_set_flags"});
   if (_initialize_) {
     // WASI reactor.
     _initialize_(root_context);