[PATCH v2] cred: rust: mark Credential methods inline

[PATCH v2] cred: rust: mark Credential methods inline

[Alice Ryhl]

When you build the kernel using the llvm-19.1.4-rust-1.83.0-x86_64
toolchain provided by kernel.org with ARCH=arm64, the following symbols
are generated:

$ nm out-linux/vmlinux | grep ' _R'.*Credential | rustfilt
ffffffc0808fc540 T <kernel::cred::Credential>::get_secid
ffffffc0808fc588 T <kernel::cred::Credential as kernel::types::AlwaysRefCounted>::dec_ref
ffffffc0808fc570 T <kernel::cred::Credential as kernel::types::AlwaysRefCounted>::inc_ref

However, these Rust symbols are trivial wrappers around the functions
security_cred_getsecid, get_cred, and put_cred respectively. It doesn't
make sense to go through a trivial wrapper for these functions, so mark
them inline. Also mark other trivial methods inline to prevent similar
cases in the future.

After applying this patch, the above command will produce no output.

Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
Changes in v2:
- Reword commit message.
- Link to v1: https://lore.kernel.org/r/20250303-inline-cred-v1-1-b2527beace76@google.com
---
 rust/kernel/cred.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/rust/kernel/cred.rs b/rust/kernel/cred.rs
index 81d67789b16f243e7832ff3b2e5e479a1ab2bf9e..2599f01e8b285f2106aefd27c315ae2aff25293c 100644
--- a/rust/kernel/cred.rs
+++ b/rust/kernel/cred.rs
@@ -47,6 +47,7 @@ impl Credential {
     ///
     /// The caller must ensure that `ptr` is valid and remains valid for the lifetime of the
     /// returned [`Credential`] reference.
+    #[inline]
     pub unsafe fn from_ptr<'a>(ptr: *const bindings::cred) -> &'a Credential {
         // SAFETY: The safety requirements guarantee the validity of the dereference, while the
         // `Credential` type being transparent makes the cast ok.
@@ -54,6 +55,7 @@ pub unsafe fn from_ptr<'a>(ptr: *const bindings::cred) -> &'a Credential {
     }
 
     /// Get the id for this security context.
+    #[inline]
     pub fn get_secid(&self) -> u32 {
         let mut secid = 0;
         // SAFETY: The invariants of this type ensures that the pointer is valid.
@@ -62,6 +64,7 @@ pub fn get_secid(&self) -> u32 {
     }
 
     /// Returns the effective UID of the given credential.
+    #[inline]
     pub fn euid(&self) -> Kuid {
         // SAFETY: By the type invariant, we know that `self.0` is valid. Furthermore, the `euid`
         // field of a credential is never changed after initialization, so there is no potential
@@ -72,11 +75,13 @@ pub fn euid(&self) -> Kuid {
 
 // SAFETY: The type invariants guarantee that `Credential` is always ref-counted.
 unsafe impl AlwaysRefCounted for Credential {
+    #[inline]
     fn inc_ref(&self) {
         // SAFETY: The existence of a shared reference means that the refcount is nonzero.
         unsafe { bindings::get_cred(self.0.get()) };
     }
 
+    #[inline]
     unsafe fn dec_ref(obj: core::ptr::NonNull<Credential>) {
         // SAFETY: The safety requirements guarantee that the refcount is nonzero. The cast is okay
         // because `Credential` has the same representation as `struct cred`.

---
base-commit: a64dcfb451e254085a7daee5fe51bf22959d52d3
change-id: 20250303-inline-cred-1d1050785e5c

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

Re: [PATCH v2] cred: rust: mark Credential methods inline

[Paul Moore]

On Mar  4, 2025 Alice Ryhl <aliceryhl@google.com> wrote:
> 
> When you build the kernel using the llvm-19.1.4-rust-1.83.0-x86_64
> toolchain provided by kernel.org with ARCH=arm64, the following symbols
> are generated:
> 
> $ nm out-linux/vmlinux | grep ' _R'.*Credential | rustfilt
> ffffffc0808fc540 T <kernel::cred::Credential>::get_secid
> ffffffc0808fc588 T <kernel::cred::Credential as kernel::types::AlwaysRefCounted>::dec_ref
> ffffffc0808fc570 T <kernel::cred::Credential as kernel::types::AlwaysRefCounted>::inc_ref
> 
> However, these Rust symbols are trivial wrappers around the functions
> security_cred_getsecid, get_cred, and put_cred respectively. It doesn't
> make sense to go through a trivial wrapper for these functions, so mark
> them inline. Also mark other trivial methods inline to prevent similar
> cases in the future.
> 
> After applying this patch, the above command will produce no output.
> 
> Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
> Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
> Reviewed-by: Christian Brauner <brauner@kernel.org>
> Signed-off-by: Alice Ryhl <aliceryhl@google.com>
> ---
> Changes in v2:
> - Reword commit message.
> - Link to v1: https://lore.kernel.org/r/20250303-inline-cred-v1-1-b2527beace76@google.com
> ---
>  rust/kernel/cred.rs | 5 +++++
>  1 file changed, 5 insertions(+)

Merged into lsm/dev, thanks everyone!

--
paul-moore.com