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, 8 deletions

diff --git a/Kernel/Syscalls/read.cpp b/Kernel/Syscalls/read.cpp
index 19bb1e1db8..99308cbab5 100644
--- a/Kernel/Syscalls/read.cpp
+++ b/Kernel/Syscalls/read.cpp
@@ -34,13 +34,9 @@ KResultOr<FlatPtr> Process::sys$readv(int fd, Userspace<const struct iovec*> iov
             return EINVAL;
     }
 
-    auto description = fds().file_description(fd);
-    if (!description)
-        return EBADF;
-
+    auto description = TRY(fds().file_description(fd));
     if (!description->is_readable())
         return EBADF;
-
     if (description->is_directory())
         return EISDIR;
 
@@ -75,9 +71,7 @@ KResultOr<FlatPtr> Process::sys$read(int fd, Userspace<u8*> buffer, size_t size)
     if (size > NumericLimits<ssize_t>::max())
         return EINVAL;
     dbgln_if(IO_DEBUG, "sys$read({}, {}, {})", fd, buffer.ptr(), size);
-    auto description = fds().file_description(fd);
-    if (!description)
-        return EBADF;
+    auto description = TRY(fds().file_description(fd));
     if (!description->is_readable())
         return EBADF;
     if (description->is_directory())