linux-kernel - [PATCH v2] rust_binder: use compat_ptr

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Message-ID: <20251031-binder-compatptrioctl-v2-1-3d05b5cc058e@google.com>
Date: Fri, 31 Oct 2025 08:48:18 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Carlos Llamas <cmllamas@...gle.com>
Cc: "Arve Hjønnevåg" <arve@...roid.com>, Todd Kjos <tkjos@...roid.com>, 
	Martijn Coenen <maco@...roid.com>, Joel Fernandes <joelagnelf@...dia.com>, 
	Christian Brauner <brauner@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>, linux-kernel@...r.kernel.org, 
	rust-for-linux@...r.kernel.org, Alice Ryhl <aliceryhl@...gle.com>
Subject: [PATCH v2] 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@...gle.com>
---
Changes in v2:
- Reword commit message.
- Link to v1: https://lore.kernel.org/r/20251030-binder-compatptrioctl-v1-1-64875010279e@google.com
---
 drivers/android/binder/process.rs          |  9 ---------
 drivers/android/binder/rust_binder_main.rs | 22 +++-------------------
 2 files changed, 3 insertions(+), 28 deletions(-)

diff --git a/drivers/android/binder/process.rs b/drivers/android/binder/process.rs
index f13a747e784c84a0fb09cbf47442712106eba07c..7df144d07b20d238a127299cd208f6280ba1bb7a 100644
--- a/drivers/android/binder/process.rs
+++ b/drivers/android/binder/process.rs
@@ -1599,15 +1599,6 @@ pub(crate) fn ioctl(this: ArcBorrow<'_, Process>, file: &File, cmd: u32, arg: us
         }
     }
 
-    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,
diff --git a/drivers/android/binder/rust_binder_main.rs b/drivers/android/binder/rust_binder_main.rs
index 6773b7c273ec9634057300954d67b51ca9b54f6f..c79a9e7422401fd50078c1902774573b8ba0076c 100644
--- a/drivers/android/binder/rust_binder_main.rs
+++ b/drivers/android/binder/rust_binder_main.rs
@@ -313,8 +313,8 @@ unsafe impl<T> Sync for AssertSync<T> {}
     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 impl<T> Sync for AssertSync<T> {}
 
 /// # 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,

---
base-commit: 211ddde0823f1442e4ad052a2f30f050145ccada
change-id: 20251030-binder-compatptrioctl-ecc9e2131edb

Best regards,
-- 
Alice Ryhl <aliceryhl@...gle.com>