Kernel: Make file description lookup return KResultOr

Instead of checking it at every call site (to generate EBADF), we make
file_description(fd) return a KResultOr<NonnullRefPtr<FileDescription>>.

This allows us to wrap all the calls in TRY(). :^)

The only place that got a little bit messier from this is sys$mount(),
and there's a whole bunch of things there in need of cleanup.

1 files changed, 2 insertions, 6 deletions

diff --git a/Kernel/Syscalls/ttyname.cpp b/Kernel/Syscalls/ttyname.cpp
index 5e795d9ff6..1b0cb09309 100644
--- a/Kernel/Syscalls/ttyname.cpp
+++ b/Kernel/Syscalls/ttyname.cpp
@@ -15,9 +15,7 @@ KResultOr<FlatPtr> Process::sys$ttyname(int fd, Userspace<char*> buffer, size_t
 {
     VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this)
     REQUIRE_PROMISE(tty);
-    auto description = fds().file_description(fd);
-    if (!description)
-        return EBADF;
+    auto description = TRY(fds().file_description(fd));
     if (!description->is_tty())
         return ENOTTY;
     auto tty_name = description->tty()->tty_name();
@@ -30,9 +28,7 @@ KResultOr<FlatPtr> Process::sys$ptsname(int fd, Userspace<char*> buffer, size_t
 {
     VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this)
     REQUIRE_PROMISE(tty);
-    auto description = fds().file_description(fd);
-    if (!description)
-        return EBADF;
+    auto description = TRY(fds().file_description(fd));
     auto* master_pty = description->master_pty();
     if (!master_pty)
         return ENOTTY;