[PATCH 0/3] rust: Fix CFI type mismatches

[PATCH 0/3] rust: Fix CFI type mismatches

[Sami Tolvanen]

This series fixes a few CONFIG_CFI indirect call type mismatches that
I've run into while working on Tyr. If we're going to run into a lot
of these in future, perhaps we need a better solution than addressing
them one at a time?

Sami

---
base-commit: c03c1a14507dfaf8b856c2608f9ac216021fc222
change-id: 20261019-rust-cfi-fixes-bd898391df1d

[PATCH 1/3] rust: irq: declare cfi_encoding for irqreturn

[Sami Tolvanen]

The IRQ callbacks return c_uint. C calls them through irq_handler_t,
which returns enum irqreturn. kCFI encodes enum types by name even with
integer normalization, so the type ids never match and every call fails
the CFI check.

Generate irqreturn as a newtype with a cfi_encoding, as is done for
lru_status, and return bindings::irqreturn_t from the callbacks.

Fixes: 0851d34a8cc3 ("rust: irq: add support for non-threaded IRQs and handlers")
Fixes: 135d40523244 ("rust: irq: add support for threaded IRQs and handlers")
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 rust/bindgen_parameters    |  2 ++
 rust/kernel/irq/request.rs | 28 +++++++++++++++++-----------
 2 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/rust/bindgen_parameters b/rust/bindgen_parameters
index 8402b0c93545..5059cc74cb3c 100644
--- a/rust/bindgen_parameters
+++ b/rust/bindgen_parameters
@@ -27,6 +27,8 @@
 --opaque-type spinlock
 
 # enums that appear in indirect function calls should specify a cfi type
+--newtype-enum irqreturn
+--with-attribute-custom-enum=irqreturn='#[cfi_encoding="9irqreturn"]'
 --newtype-enum lru_status
 --with-attribute-custom-enum=lru_status='#[cfi_encoding="10lru_status"]'
 
diff --git a/rust/kernel/irq/request.rs b/rust/kernel/irq/request.rs
index c1c6525a676a..1afa9fcaad1f 100644
--- a/rust/kernel/irq/request.rs
+++ b/rust/kernel/irq/request.rs
@@ -25,10 +25,10 @@
 #[repr(u32)]
 pub enum IrqReturn {
     /// The interrupt was not from this device or was not handled.
-    None = bindings::irqreturn_IRQ_NONE,
+    None = bindings::irqreturn::IRQ_NONE.0,
 
     /// The interrupt was handled by this device.
-    Handled = bindings::irqreturn_IRQ_HANDLED,
+    Handled = bindings::irqreturn::IRQ_HANDLED.0,
 }
 
 /// Callbacks for an IRQ handler.
@@ -240,25 +240,28 @@ fn drop(self: Pin<&mut Self>) {
 /// # Safety
 ///
 /// This function should be only used as the callback in `request_irq`.
-unsafe extern "C" fn handle_irq_callback<T: Handler>(_irq: i32, ptr: *mut c_void) -> c_uint {
+unsafe extern "C" fn handle_irq_callback<T: Handler>(
+    _irq: i32,
+    ptr: *mut c_void,
+) -> bindings::irqreturn_t {
     let ptr = ptr.cast_const().cast::<Registration<'_, T>>();
     // SAFETY: `ptr` is a pointer to `Registration<'_, T>` set in `Registration::new()`.
     let registration = unsafe { &*ptr };
 
-    T::handle(&registration.handler) as c_uint
+    bindings::irqreturn_t(T::handle(&registration.handler) as c_uint)
 }
 
 /// The value that can be returned from [`ThreadedHandler::handle`].
 #[repr(u32)]
 pub enum ThreadedIrqReturn {
     /// The interrupt was not from this device or was not handled.
-    None = bindings::irqreturn_IRQ_NONE,
+    None = bindings::irqreturn::IRQ_NONE.0,
 
     /// The interrupt was handled by this device.
-    Handled = bindings::irqreturn_IRQ_HANDLED,
+    Handled = bindings::irqreturn::IRQ_HANDLED.0,
 
     /// The handler wants the handler thread to wake up.
-    WakeThread = bindings::irqreturn_IRQ_WAKE_THREAD,
+    WakeThread = bindings::irqreturn::IRQ_WAKE_THREAD.0,
 }
 
 /// Callbacks for a threaded IRQ handler.
@@ -461,23 +464,26 @@ fn drop(self: Pin<&mut Self>) {
 unsafe extern "C" fn handle_threaded_irq_callback<T: ThreadedHandler>(
     _irq: i32,
     ptr: *mut c_void,
-) -> c_uint {
+) -> bindings::irqreturn_t {
     let ptr = ptr.cast_const().cast::<ThreadedRegistration<'_, T>>();
     // SAFETY: `ptr` is a pointer to `ThreadedRegistration<'_, T>` set in
     // `ThreadedRegistration::new()`.
     let registration = unsafe { &*ptr };
 
-    T::handle(&registration.handler) as c_uint
+    bindings::irqreturn_t(T::handle(&registration.handler) as c_uint)
 }
 
 /// # Safety
 ///
 /// This function should be only used as the callback in `request_threaded_irq`.
-unsafe extern "C" fn thread_fn_callback<T: ThreadedHandler>(_irq: i32, ptr: *mut c_void) -> c_uint {
+unsafe extern "C" fn thread_fn_callback<T: ThreadedHandler>(
+    _irq: i32,
+    ptr: *mut c_void,
+) -> bindings::irqreturn_t {
     let ptr = ptr.cast_const().cast::<ThreadedRegistration<'_, T>>();
     // SAFETY: `ptr` is a pointer to `ThreadedRegistration<'_, T>` set in
     // `ThreadedRegistration::new()`.
     let registration = unsafe { &*ptr };
 
-    T::handle_threaded(&registration.handler) as c_uint
+    bindings::irqreturn_t(T::handle_threaded(&registration.handler) as c_uint)
 }

-- 
2.56.0.212.g129ede20d9-goog

[PATCH 2/3] rust: hrtimer: declare cfi_encoding for hrtimer_restart

[Sami Tolvanen]

The hrtimer callbacks return bindings::hrtimer_restart, which bindgen
generates as c_uint. C calls them through hrtimer->function, which
returns enum hrtimer_restart. kCFI encodes enum types by name even with
integer normalization, so the type ids never match and every call fails
the CFI check.

Generate hrtimer_restart as a newtype with a cfi_encoding, as is done
for lru_status, and adapt HrTimerRestart to the newtype.

Fixes: 8a8afe9349fb ("rust: hrtimer: introduce hrtimer support")
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 rust/bindgen_parameters     | 2 ++
 rust/kernel/time/hrtimer.rs | 6 +++---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/rust/bindgen_parameters b/rust/bindgen_parameters
index 5059cc74cb3c..6003d5127676 100644
--- a/rust/bindgen_parameters
+++ b/rust/bindgen_parameters
@@ -27,6 +27,8 @@
 --opaque-type spinlock
 
 # enums that appear in indirect function calls should specify a cfi type
+--newtype-enum hrtimer_restart
+--with-attribute-custom-enum=hrtimer_restart='#[cfi_encoding="15hrtimer_restart"]'
 --newtype-enum irqreturn
 --with-attribute-custom-enum=irqreturn='#[cfi_encoding="9irqreturn"]'
 --newtype-enum lru_status
diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
index 2d7f1131a813..07344ed5fbd5 100644
--- a/rust/kernel/time/hrtimer.rs
+++ b/rust/kernel/time/hrtimer.rs
@@ -834,14 +834,14 @@ unsafe fn start(this: *const Self, expires: <Self::TimerMode as HrTimerMode>::Ex
 #[repr(u32)]
 pub enum HrTimerRestart {
     /// Timer should not be restarted.
-    NoRestart = bindings::hrtimer_restart_HRTIMER_NORESTART,
+    NoRestart = bindings::hrtimer_restart::HRTIMER_NORESTART.0,
     /// Timer should be restarted.
-    Restart = bindings::hrtimer_restart_HRTIMER_RESTART,
+    Restart = bindings::hrtimer_restart::HRTIMER_RESTART.0,
 }
 
 impl HrTimerRestart {
     fn into_c(self) -> bindings::hrtimer_restart {
-        self as bindings::hrtimer_restart
+        bindings::hrtimer_restart(self as c_uint)
     }
 }
 

-- 
2.56.0.212.g129ede20d9-goog

[PATCH 3/3] rust: dma: declare cfi_encoding for dma_data_direction

[Sami Tolvanen]

bindgen generates bindings::dma_data_direction as an integer by default,
while C callback tables such as dma_buf_ops declare the parameter as
enum dma_data_direction. kCFI encodes enum types by name even with
integer normalization, so the type ids would not match when C calls into
a Rust callback taking bindings::dma_data_direction.

Generate dma_data_direction as a newtype with a cfi_encoding, as is done
for lru_status, and convert DataDirection through the newtype's
constants.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 rust/bindgen_parameters |  2 ++
 rust/kernel/dma.rs      | 21 +++++++++++----------
 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/rust/bindgen_parameters b/rust/bindgen_parameters
index 6003d5127676..8577e7663e02 100644
--- a/rust/bindgen_parameters
+++ b/rust/bindgen_parameters
@@ -27,6 +27,8 @@
 --opaque-type spinlock
 
 # enums that appear in indirect function calls should specify a cfi type
+--newtype-enum dma_data_direction
+--with-attribute-custom-enum=dma_data_direction='#[cfi_encoding="18dma_data_direction"]'
 --newtype-enum hrtimer_restart
 --with-attribute-custom-enum=hrtimer_restart='#[cfi_encoding="15hrtimer_restart"]'
 --newtype-enum irqreturn
diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs
index 2ce09f8e90c6..2ec5fe7d56bc 100644
--- a/rust/kernel/dma.rs
+++ b/rust/kernel/dma.rs
@@ -310,25 +310,25 @@ pub enum DataDirection {
     ///
     /// This is used when the buffer can be both read from and written to by the device.
     /// The cache for the corresponding memory region is both flushed and invalidated.
-    Bidirectional = Self::const_cast(bindings::dma_data_direction_DMA_BIDIRECTIONAL),
+    Bidirectional = Self::const_cast(bindings::dma_data_direction::DMA_BIDIRECTIONAL),
 
     /// The DMA mapping is for data transfer from memory to the device (write).
     ///
     /// The CPU has prepared data in the buffer, and the device will read it.
     /// The cache for the corresponding memory region is flushed before device access.
-    ToDevice = Self::const_cast(bindings::dma_data_direction_DMA_TO_DEVICE),
+    ToDevice = Self::const_cast(bindings::dma_data_direction::DMA_TO_DEVICE),
 
     /// The DMA mapping is for data transfer from the device to memory (read).
     ///
     /// The device will write data into the buffer for the CPU to read.
     /// The cache for the corresponding memory region is invalidated before CPU access.
-    FromDevice = Self::const_cast(bindings::dma_data_direction_DMA_FROM_DEVICE),
+    FromDevice = Self::const_cast(bindings::dma_data_direction::DMA_FROM_DEVICE),
 
     /// The DMA mapping is not for data transfer.
     ///
     /// This is primarily for debugging purposes. With this direction, the DMA mapping API
     /// will not perform any cache coherency operations.
-    None = Self::const_cast(bindings::dma_data_direction_DMA_NONE),
+    None = Self::const_cast(bindings::dma_data_direction::DMA_NONE),
 }
 
 impl DataDirection {
@@ -340,7 +340,7 @@ const fn const_cast(val: bindings::dma_data_direction) -> u32 {
         // CAST: The C standard allows compilers to choose different integer types for enums.
         // To safely check the value, we cast it to a wide signed integer type (`i128`)
         // which can hold any standard C integer enum type without truncation.
-        let wide_val = val as i128;
+        let wide_val = val.0 as i128;
 
         // Check if the value is outside the valid range for the target type `u32`.
         // CAST: `u32::MAX` is cast to `i128` to match the type of `wide_val` for the comparison.
@@ -358,11 +358,12 @@ const fn const_cast(val: bindings::dma_data_direction) -> u32 {
 impl From<DataDirection> for bindings::dma_data_direction {
     /// Returns the raw representation of [`enum dma_data_direction`].
     fn from(direction: DataDirection) -> Self {
-        // CAST: `direction as u32` gets the underlying representation of our `#[repr(u32)]` enum.
-        // The subsequent cast to `Self` (the bindgen type) assumes the C enum is compatible
-        // with the enum variants of `DataDirection`, which is a valid assumption given our
-        // compile-time checks.
-        direction as u32 as Self
+        match direction {
+            DataDirection::Bidirectional => Self::DMA_BIDIRECTIONAL,
+            DataDirection::ToDevice => Self::DMA_TO_DEVICE,
+            DataDirection::FromDevice => Self::DMA_FROM_DEVICE,
+            DataDirection::None => Self::DMA_NONE,
+        }
     }
 }
 

-- 
2.56.0.212.g129ede20d9-goog