wasi: export stubs for preopened files and directories.

include/proxy-wasm/exports.h

@@ -172,6 +172,11 @@ void wasi_unstable_proc_exit(Word);
 Word wasi_unstable_clock_time_get(Word, uint64_t, Word);
 Word wasi_unstable_random_get(Word, Word);
 Word pthread_equal(Word left, Word right);
+Word wasi_unstable_path_open(Word fd, Word dir_flags, Word path, Word path_len, Word oflags,
+                             int64_t fs_rights_base, int64_t fg_rights_inheriting, Word fd_flags,
+                             Word nwritten_ptr);
+Word wasi_unstable_fd_prestat_get(Word fd, Word buf_ptr);
+Word wasi_unstable_fd_prestat_dir_name(Word fd, Word path_ptr, Word path_len);
 
 // Support for embedders, not exported to Wasm.
 
@@ -196,7 +201,7 @@ Word pthread_equal(Word left, Word right);
 #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(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)                                                               \

include/proxy-wasm/wasm_vm.h

@@ -110,6 +110,8 @@ using WasmCallback_WWl = Word (*)(Word, int64_t);
 using WasmCallback_WWlWW = Word (*)(Word, int64_t, Word, Word);
 using WasmCallback_WWm = Word (*)(Word, uint64_t);
 using WasmCallback_WWmW = Word (*)(Word, uint64_t, Word);
+using WasmCallback_WWWWWWllWW = Word (*)(Word, Word, Word, Word, Word, int64_t, int64_t, Word,
+                                         Word);
 using WasmCallback_dd = double (*)(double);
 
 #define FOR_ALL_WASM_VM_IMPORTS(_f)                                                                \
@@ -127,7 +129,8 @@ using WasmCallback_dd = double (*)(double);
                                               _f(proxy_wasm::WasmCallback_WWlWW)                   \
                                                   _f(proxy_wasm::WasmCallback_WWm)                 \
                                                       _f(proxy_wasm::WasmCallback_WWmW)            \
-                                                          _f(proxy_wasm::WasmCallback_dd)
+                                                          _f(proxy_wasm::WasmCallback_WWWWWWllWW)  \
+                                                              _f(proxy_wasm::WasmCallback_dd)
 
 enum class Cloneable {
   NotCloneable,      // VMs can not be cloned and should be created from scratch.

src/exports.cc

@@ -715,6 +715,29 @@ Word writevImpl(Word fd, Word iovs, Word iovs_len, Word *nwritten_ptr) {
   return 0; // __WASI_ESUCCESS
 }
 
+// __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)
+Word wasi_unstable_path_open(Word fd, Word dir_flags, Word path, Word path_len, Word oflags,
+                             int64_t fs_rights_base, int64_t fg_rights_inheriting, Word fd_flags,
+                             Word nwritten_ptr) {
+  return 52; // __WASI_ERRNO_ENOSYS
+}
+
+// __wasi_errno_t __wasi_fd_read(__wasi_fd_t fd, __wasi_prestat_t *retptr0)
+Word wasi_unstable_fd_prestat_get(Word fd, Word buf_ptr) {
+  // If we throw other errors, the preopen in WASI ctors immediately exits the program,
+  // so we just return BADF so that ctors exist successfully even if
+  // we don't support any preopens yet.
+  // https://github.com/WebAssembly/wasi-libc/blob/f2e779e5f1ba4a539937cedeeaa762c1e0c162df/libc-bottom-half/sources/preopens.c#L218-L221
+  return 8; // __WASI_ERRNO_BADF
+}
+
+// __wasi_errno_t __wasi_fd_prestat_dir_name(__wasi_fd_t fd, uint8_t * path, __wasi_size_t path_len)
+Word wasi_unstable_fd_prestat_dir_name(Word fd, Word path_ptr, Word path_len) {
+  return 52; // __WASI_ERRNO_ENOSYS
+}
+
 // __wasi_errno_t __wasi_fd_write(_wasi_fd_t fd, const _wasi_ciovec_t *iov,
 // size_t iovs_len, size_t* nwritten);
 Word wasi_unstable_fd_write(Word fd, Word iovs, Word iovs_len, Word nwritten_ptr) {