From 68aabb29a5469e4b7358e70e64a7fac433e27f06 Mon Sep 17 00:00:00 2001 From: Alice Ryhl Date: Mon, 5 Jan 2026 14:25:03 +0000 Subject: [PATCH] rust: redefine `bindings::compat_ptr_ioctl` in Rust There is currently an inconsistency between C and Rust, which is that when Rust requires cfg(CONFIG_COMPAT) on compat_ioctl when using the compat_ptr_ioctl symbol because '#define compat_ptr_ioctl NULL' does not get translated to anything by bindgen. But it's not *just* a matter of translating the '#define' into Rust when CONFIG_COMPAT=n. This is because when CONFIG_COMPAT=y, the type of compat_ptr_ioctl is a non-nullable function pointer, and to seamlessly use it regardless of the config, we need a nullable function pointer. I think it's important to do something about this; I've seen the mistake of accidentally forgetting '#[cfg(CONFIG_COMPAT)]' when compat_ptr_ioctl is used multiple times now. This explicitly declares 'bindings::compat_ptr_ioctl' as an Option that is always defined but might be None. This matches C, but isn't ideal: it modifies the bindings crate. But I'm not sure if there's a better way to do it. If we just redefine in kernel/, then people may still use the one in bindings::, since that is where you would normally find it. I am open to suggestions. Signed-off-by: Alice Ryhl Reviewed-by: Gary Guo Link: https://patch.msgid.link/20260105-redefine-compat_ptr_ioctl-v1-1-25edb3d91acc@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder/rust_binder_main.rs | 3 +-- rust/bindings/lib.rs | 13 +++++++++++++ rust/kernel/miscdevice.rs | 2 +- 3 files changed, 15 insertions(+), 3 deletions(-) diff --git a/drivers/android/binder/rust_binder_main.rs b/drivers/android/binder/rust_binder_main.rs index d84c3c360be0e..30e4517f90a3c 100644 --- a/drivers/android/binder/rust_binder_main.rs +++ b/drivers/android/binder/rust_binder_main.rs @@ -322,8 +322,7 @@ pub static rust_binder_fops: AssertSync = { owner: THIS_MODULE.as_ptr(), poll: Some(rust_binder_poll), unlocked_ioctl: Some(rust_binder_ioctl), - #[cfg(CONFIG_COMPAT)] - compat_ioctl: Some(bindings::compat_ptr_ioctl), + compat_ioctl: bindings::compat_ptr_ioctl, mmap: Some(rust_binder_mmap), open: Some(rust_binder_open), release: Some(rust_binder_release), diff --git a/rust/bindings/lib.rs b/rust/bindings/lib.rs index 0c57cf9b4004f..19f57c5b2fa2a 100644 --- a/rust/bindings/lib.rs +++ b/rust/bindings/lib.rs @@ -67,3 +67,16 @@ mod bindings_helper { } pub use bindings_raw::*; + +pub const compat_ptr_ioctl: Option< + unsafe extern "C" fn(*mut file, ffi::c_uint, ffi::c_ulong) -> ffi::c_long, +> = { + #[cfg(CONFIG_COMPAT)] + { + Some(bindings_raw::compat_ptr_ioctl) + } + #[cfg(not(CONFIG_COMPAT))] + { + None + } +}; diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs index ba64c8a858f0d..c3c2052c92069 100644 --- a/rust/kernel/miscdevice.rs +++ b/rust/kernel/miscdevice.rs @@ -410,7 +410,7 @@ impl MiscdeviceVTable { compat_ioctl: if T::HAS_COMPAT_IOCTL { Some(Self::compat_ioctl) } else if T::HAS_IOCTL { - Some(bindings::compat_ptr_ioctl) + bindings::compat_ptr_ioctl } else { None }, -- 2.47.3