[PATCH 6.18.y 1/2] rust: hrtimer: declare cfi_encoding for hrtimer_restart

[Miguel Ojeda <ojeda@kernel.org>]

From: Sami Tolvanen <samitolvanen@google.com>

commit 39fe6892fd52faed6325ff7f13a92da01ab35727 upstream.

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>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Tested-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Acked-by: Andreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20261019-rust-cfi-fixes-v1-2-9503472ba738@google.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
[ Replaced bindgen's custom enum attribute option with sed
  post-processing to support older bindgen. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 rust/Makefile               | 1 +
 rust/bindgen_parameters     | 1 +
 rust/kernel/time/hrtimer.rs | 6 +++---
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/rust/Makefile b/rust/Makefile
index 3867ff14fbde..3f1abad648e6 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -368,6 +368,7 @@ $(obj)/bindings/bindings_generated.rs: private bindgen_target_flags = \
     $(shell grep -Ev '^#|^$$' $(src)/bindgen_parameters)
 $(obj)/bindings/bindings_generated.rs: private bindgen_target_extra = ; \
     sed -Ei 's/pub const RUST_CONST_HELPER_([a-zA-Z0-9_]*)/pub const \1/g' $@; \
+    sed -Ei 's/^pub struct hrtimer_restart\(/#[cfi_encoding="15hrtimer_restart"]\n&/' $@; \
     sed -Ei 's/^pub struct irqreturn\(/#[cfi_encoding="9irqreturn"]\n&/' $@
 $(obj)/bindings/bindings_generated.rs: $(src)/bindings/bindings_helper.h \
     $(src)/bindgen_parameters FORCE
diff --git a/rust/bindgen_parameters b/rust/bindgen_parameters
index 9e02500dc979..6f76fdcffd58 100644
--- a/rust/bindgen_parameters
+++ b/rust/bindgen_parameters
@@ -24,6 +24,7 @@
 --opaque-type spinlock
 
 # enums that appear in indirect function calls should specify a cfi type
+--newtype-enum hrtimer_restart
 --newtype-enum irqreturn
 
 # `seccomp`'s comment gets understood as a doctest
diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
index 856d2d929a00..35ff2ef7d944 100644
--- a/rust/kernel/time/hrtimer.rs
+++ b/rust/kernel/time/hrtimer.rs
@@ -498,14 +498,14 @@ 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