The hand-written bitfield offsets in is_link_up(), is_autoneg_enabled() and is_autoneg_completed() were correct when the abstraction was merged: at that time autoneg, link, and autoneg_complete were at bits 13, 14, and 15 of struct phy_device's first bitfield unit. Commit 2796ff1e3dca ("net: phy: add flag is_genphy_driven to struct phy_device") later inserted is_genphy_driven just before autoneg, shifting the three fields up by one, so the accessors now read: is_link_up() reads bit 14 = autoneg is_autoneg_enabled() reads bit 13 = is_genphy_driven is_autoneg_completed() reads bit 15 = link The official ax88796b Rust driver uses all three accessors in its link-change handling, so it inherits the bug. On genphy-driven devices is_genphy_driven is always 1, which masks the broken is_autoneg_enabled() check. The ordinary bindgen accessors take &self. Calling them through (*phydev).link() would create a shared reference to the complete bindings::phy_device, which is not appropriate for an object wrapped in Opaque. Use the bindgen-generated raw accessors (link_raw(), autoneg_raw(), and autoneg_complete_raw()) instead. They retain the bit positions and endianness handling generated from the C layout without creating a Rust reference to the complete phy_device. Drop the hand-written numbers together with the TODO comment that marked them as a stopgap. The raw accessors are only emitted by bindgen 0.71 and later, and were added at the Rust-for-Linux project's request, so this fix can only be backported to stable branches whose minimum bindgen version is at least that, hence the scope on the Cc: stable line below. Found by a static equivalence audit (C2RustDrv, a C-to-Rust driver migration tool) that compares hand-written bitfield offsets against the bindgen layout of struct phy_device. Verified by building the bindings and checking the generated accessors; no runtime testing was possible without PHY hardware. Fixes: 2796ff1e3dca ("net: phy: add flag is_genphy_driven to struct phy_device") Cc: stable@vger.kernel.org # Only 7.1.y and later (requires bindgen's raw pointer accessors). Link: https://github.com/rust-lang/rust-bindgen/issues/2674 Signed-off-by: Chunfeng Song --- --- v5: - Move the comparison out of the `unsafe` block so that only the raw accessor call stays inside (Gary Guo, Miguel Ojeda). - Scope the `Cc: stable` backport to 7.1.y and later, since the raw accessors require bindgen 0.71 (Miguel Ojeda). - Mention the bindgen 0.71 dependency in the commit message. v4: https://lore.kernel.org/r/20260901031824.1377498-1-springbreeze@stu.pku.edu.cn/ - Use the bindgen-generated raw accessors to avoid creating a shared reference to the complete C `phy_device`, as suggested by Jakub Kicinski. - Update the SAFETY comments to describe pointer validity and the callback-context preconditions. - Add `#[inline]` to the three small forwarding methods. v3: https://lore.kernel.org/r/20260825111334.795732-1-springbreeze@stu.pku.edu.cn/ - Use the bindgen-generated accessors instead of hard-coded bit numbers. - Update the Fixes tag and add the net tree subject prefix. v2: https://lore.kernel.org/r/20260824111227.742645-1-springbreeze@stu.pku.edu.cn/ - Use bindgen-generated accessors as suggested by Andrew Lunn. - Explain that the offsets drifted after `is_genphy_driven` was added. v1: https://lore.kernel.org/r/20260823103644.342849-1-springbreeze@stu.pku.edu.cn/ rust/kernel/net/phy.rs | 44 +++++++++++++++++++++++------------------- 1 file changed, 24 insertions(+), 20 deletions(-) diff --git a/rust/kernel/net/phy.rs b/rust/kernel/net/phy.rs index 956cda573ddb..256f939c5098 100644 --- a/rust/kernel/net/phy.rs +++ b/rust/kernel/net/phy.rs @@ -123,39 +123,43 @@ pub fn state(&self) -> DeviceState { /// Gets the current link state. /// /// It returns true if the link is up. + #[inline] pub fn is_link_up(&self) -> bool { - const LINK_IS_UP: u64 = 1; - // TODO: the code to access to the bit field will be replaced with automatically - // generated code by bindgen when it becomes possible. - // SAFETY: The struct invariant ensures that we may access - // this field without additional synchronization. - let bit_field = unsafe { &(*self.0.get())._bitfield_1 }; - bit_field.get(14, 1) == LINK_IS_UP + let phydev = self.0.get().cast_const(); + // SAFETY: By the type invariant of `Device`, `phydev` points to a valid + // `struct phy_device`, and the caller is in a context where this access + // is safe. The bindgen raw accessor does not create a Rust reference to + // the C struct. + let link = unsafe { bindings::phy_device::link_raw(phydev) }; + link == 1 } /// Gets the current auto-negotiation configuration. /// /// It returns true if auto-negotiation is enabled. + #[inline] pub fn is_autoneg_enabled(&self) -> bool { - // TODO: the code to access to the bit field will be replaced with automatically - // generated code by bindgen when it becomes possible. - // SAFETY: The struct invariant ensures that we may access - // this field without additional synchronization. - let bit_field = unsafe { &(*self.0.get())._bitfield_1 }; - bit_field.get(13, 1) == u64::from(bindings::AUTONEG_ENABLE) + let phydev = self.0.get().cast_const(); + // SAFETY: By the type invariant of `Device`, `phydev` points to a valid + // `struct phy_device`, and the caller is in a context where this access + // is safe. The bindgen raw accessor does not create a Rust reference to + // the C struct. + let autoneg = unsafe { bindings::phy_device::autoneg_raw(phydev) }; + autoneg == bindings::AUTONEG_ENABLE } /// Gets the current auto-negotiation state. /// /// It returns true if auto-negotiation is completed. + #[inline] pub fn is_autoneg_completed(&self) -> bool { - const AUTONEG_COMPLETED: u64 = 1; - // TODO: the code to access to the bit field will be replaced with automatically - // generated code by bindgen when it becomes possible. - // SAFETY: The struct invariant ensures that we may access - // this field without additional synchronization. - let bit_field = unsafe { &(*self.0.get())._bitfield_1 }; - bit_field.get(15, 1) == AUTONEG_COMPLETED + let phydev = self.0.get().cast_const(); + // SAFETY: By the type invariant of `Device`, `phydev` points to a valid + // `struct phy_device`, and the caller is in a context where this access + // is safe. The bindgen raw accessor does not create a Rust reference to + // the C struct. + let completed = unsafe { bindings::phy_device::autoneg_complete_raw(phydev) }; + completed == 1 } /// Sets the speed of the PHY. base-commit: 2709dd5ae32f0828f386327c76bba9f39f63a1c6 -- 2.43.0