Kernel+LibC: Remove ENOTSUP fallback for file actions

All posix_spawn file actions are now implemented in the kernel:
- dup2, close, open, chdir, fchdir

The ENOTSUP fallback path in LibC is no longer needed. Errors from
file actions are now returned directly from the syscall.

The fork() path is still used when spawnattr is present (FIXME).

Author: firatkizilboga

Kernel/API/Syscall.h

@@ -495,7 +495,6 @@ struct SC_posix_spawn_params {
     size_t attr_data_size;
     Userspace<void const*> serialized_file_actions_data;
     size_t serialized_file_actions_data_size;
-    u8 file_action_types_present;
 };
 
 struct SC_futimens_params {

Kernel/Syscalls/posix_spawn.cpp

@@ -47,6 +47,7 @@ ErrorOr<void> Process::execute_file_actions(ReadonlyBytes file_actions_data)
 
                 auto description = TRY(fds.open_file_description(action->old_fd));
                 if (action->old_fd != action->new_fd) {
+
                     if (fds.m_fds_metadatas[action->new_fd].is_allocated()) {
                         if (auto* old_description = fds[action->new_fd].description())
                             (void)old_description->close();
@@ -109,6 +110,7 @@ ErrorOr<void> Process::execute_file_actions(ReadonlyBytes file_actions_data)
             }));
             break;
         }
+
         case SpawnFileActionType::Chdir: {
             if (header->record_length < sizeof(SpawnFileActionChdir))
                 return EINVAL;
@@ -134,7 +136,7 @@ ErrorOr<void> Process::execute_file_actions(ReadonlyBytes file_actions_data)
             if (!description->is_directory())
                 return ENOTDIR;
 
-            // Check for search (+x) permission on the directory
+            // Check for search (+x) permission on the directory.
             if (!description->metadata().may_execute(credentials()))
                 return EACCES;
 
@@ -174,10 +176,6 @@ ErrorOr<FlatPtr> Process::sys$posix_spawn(Userspace<Syscall::SC_posix_spawn_para
     // Copy file actions buffer from userspace
     OwnPtr<KBuffer> file_actions_buffer;
     if (params.serialized_file_actions_data.ptr() != 0 && params.serialized_file_actions_data_size != 0) {
-        // Check for unsupported file actions
-        constexpr u8 SUPPORTED_SPAWN_ACTIONS = (1 << static_cast<u8>(SpawnFileActionType::Dup2)) | (1 << static_cast<u8>(SpawnFileActionType::Close)) | (1 << static_cast<u8>(SpawnFileActionType::Open)) | (1 << static_cast<u8>(SpawnFileActionType::Chdir)) | (1 << static_cast<u8>(SpawnFileActionType::Fchdir));
-        if (params.file_action_types_present & ~SUPPORTED_SPAWN_ACTIONS)
-            return ENOTSUP;
 
         if (params.serialized_file_actions_data_size > 1 * MiB)
             return E2BIG;

Userland/Libraries/LibC/spawn.cpp

@@ -28,7 +28,6 @@
 
 struct posix_spawn_file_actions_state {
     ByteBuffer buffer;
-    u8 action_types_present { 0 };
 };
 
 extern "C" {
@@ -196,11 +195,9 @@ static ErrorOr<pid_t> posix_spawn_syscall(char const* path, posix_spawn_file_act
     if (file_actions && !file_actions->state->buffer.is_empty()) {
         posix_spawn_params.serialized_file_actions_data = file_actions->state->buffer.data();
         posix_spawn_params.serialized_file_actions_data_size = file_actions->state->buffer.size();
-        posix_spawn_params.file_action_types_present = file_actions->state->action_types_present;
     } else {
         posix_spawn_params.serialized_file_actions_data = nullptr;
         posix_spawn_params.serialized_file_actions_data_size = 0;
-        posix_spawn_params.file_action_types_present = 0;
     }
 
     pid_t rc = syscall(SC_posix_spawn, &posix_spawn_params);
@@ -229,23 +226,8 @@ int posix_spawn(pid_t* out_pid, char const* path, posix_spawn_file_actions_t con
     }
 
     auto child_pid_or_error = posix_spawn_syscall(path, file_actions, argv, envp);
-    if (child_pid_or_error.is_error()) {
-        // ENOTSUP means kernel doesn't support these file actions yet, fall back to fork()
-        if (child_pid_or_error.error().code() == ENOTSUP) {
-            pid_t child_pid = fork();
-            if (child_pid < 0)
-                return errno;
-
-            if (child_pid != 0) {
-                if (out_pid)
-                    *out_pid = child_pid;
-                return 0;
-            }
-
-            posix_spawn_child(path, file_actions, attr, argv, envp, execve);
-        }
+    if (child_pid_or_error.is_error())
         return child_pid_or_error.error().code();
-    }
 
     if (out_pid)
         *out_pid = child_pid_or_error.value();
@@ -315,7 +297,6 @@ int posix_spawn_file_actions_addchdir(posix_spawn_file_actions_t* actions, char
 
     if (actions->state->buffer.try_append(record_buffer.data(), record_size).is_error())
         return ENOMEM;
-    actions->state->action_types_present |= (1 << static_cast<u8>(SpawnFileActionType::Chdir));
     return 0;
 }
 
@@ -328,7 +309,6 @@ int posix_spawn_file_actions_addfchdir(posix_spawn_file_actions_t* actions, int
     action.fd = fd;
     if (actions->state->buffer.try_append(&action, sizeof(action)).is_error())
         return ENOMEM;
-    actions->state->action_types_present |= (1 << static_cast<u8>(SpawnFileActionType::Fchdir));
     return 0;
 }
 
@@ -342,7 +322,6 @@ int posix_spawn_file_actions_addclose(posix_spawn_file_actions_t* actions, int f
     action.fd = fd;
     if (actions->state->buffer.try_append(&action, sizeof(action)).is_error())
         return ENOMEM;
-    actions->state->action_types_present |= (1 << static_cast<u8>(SpawnFileActionType::Close));
     return 0;
 }
 
@@ -357,7 +336,6 @@ int posix_spawn_file_actions_adddup2(posix_spawn_file_actions_t* actions, int ol
     action.new_fd = new_fd;
     if (actions->state->buffer.try_append(&action, sizeof(action)).is_error())
         return ENOMEM;
-    actions->state->action_types_present |= (1 << static_cast<u8>(SpawnFileActionType::Dup2));
     return 0;
 }
 
@@ -386,7 +364,6 @@ int posix_spawn_file_actions_addopen(posix_spawn_file_actions_t* actions, int wa
 
     if (actions->state->buffer.try_append(record_buffer.data(), record_size).is_error())
         return ENOMEM;
-    actions->state->action_types_present |= (1 << static_cast<u8>(SpawnFileActionType::Open));
     return 0;
 }