rust_binder: use compat_ptr_ioctl

Binder always treats the ioctl argument as a pointer. In this scenario,
the idiomatic way to implement compat_ioctl is to use compat_ptr_ioctl.
Thus update Rust Binder to do that.

Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Carlos Llamas <cmllamas@google.com>
Link: https://patch.msgid.link/20251031-binder-compatptrioctl-v2-1-3d05b5cc058e@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Darksonn

drivers/android/binder/process.rs

@@ -1623,15 +1623,6 @@ impl Process {
         }
     }
 
-    pub(crate) fn compat_ioctl(
-        this: ArcBorrow<'_, Process>,
-        file: &File,
-        cmd: u32,
-        arg: usize,
-    ) -> Result {
-        Self::ioctl(this, file, cmd, arg)
-    }
-
     pub(crate) fn mmap(
         this: ArcBorrow<'_, Process>,
         _file: &File,

drivers/android/binder/rust_binder_main.rs

@@ -313,8 +313,8 @@ pub static rust_binder_fops: AssertSync<kernel::bindings::file_operations> = {
     let ops = kernel::bindings::file_operations {
         owner: THIS_MODULE.as_ptr(),
         poll: Some(rust_binder_poll),
-        unlocked_ioctl: Some(rust_binder_unlocked_ioctl),
-        compat_ioctl: Some(rust_binder_compat_ioctl),
+        unlocked_ioctl: Some(rust_binder_ioctl),
+        compat_ioctl: Some(bindings::compat_ptr_ioctl),
         mmap: Some(rust_binder_mmap),
         open: Some(rust_binder_open),
         release: Some(rust_binder_release),
@@ -402,23 +402,7 @@ unsafe extern "C" fn rust_binder_release(
 
 /// # Safety
 /// Only called by binderfs.
-unsafe extern "C" fn rust_binder_compat_ioctl(
-    file: *mut bindings::file,
-    cmd: kernel::ffi::c_uint,
-    arg: kernel::ffi::c_ulong,
-) -> kernel::ffi::c_long {
-    // SAFETY: We previously set `private_data` in `rust_binder_open`.
-    let f = unsafe { Arc::<Process>::borrow((*file).private_data) };
-    // SAFETY: The caller ensures that the file is valid.
-    match Process::compat_ioctl(f, unsafe { File::from_raw_file(file) }, cmd as _, arg as _) {
-        Ok(()) => 0,
-        Err(err) => err.to_errno() as isize,
-    }
-}
-
-/// # Safety
-/// Only called by binderfs.
-unsafe extern "C" fn rust_binder_unlocked_ioctl(
+unsafe extern "C" fn rust_binder_ioctl(
     file: *mut bindings::file,
     cmd: kernel::ffi::c_uint,
     arg: kernel::ffi::c_ulong,