Rust Binder will need to read CLOCK_MONOTONIC to compute how many
milliseconds a transaction has been active for when dumping the current
state of the Binder driver. This replicates the logic in C Binder [1].

For a usage example in Rust Binder, see [2].

Hence add the support for CLOCK_MONOTONIC read.

The `ktime_get` method cannot be safely called in NMI context. This
requirement is not checked by these abstractions, but it is intended
that klint [3] or a similar tool will be used to check it in the future.

Link: https://lore.kernel.org/lkml/5ac8c0d09392290be789423f0dd78a520b830fab.1682333709.git.zhangchuang3@xiaomi.com/ [1]
Link: https://r.android.com/3004103 [2]
Link: https://rust-for-linux.com/klint [3]
Co-developed-by: Heghedus Razvan <heghedus.razvan@protonmail.com>
Signed-off-by: Heghedus Razvan <heghedus.razvan@protonmail.com>
Co-developed-by: Asahi Lina <lina@asahilina.net>
Signed-off-by: Asahi Lina <lina@asahilina.net>
Co-developed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---
@Alice, I still put the link to the usage of Android binder here, if you
want to remove that, please let me know.

 rust/kernel/time.rs | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs
index 0f9f5605ed48..5cd669cbea01 100644
--- a/rust/kernel/time.rs
+++ b/rust/kernel/time.rs
@@ -113,3 +113,22 @@ fn sub(self, other: Self) -> Self::Output {
         Duration::new(self.inner.wrapping_sub(other.inner))
     }
 }
+
+/// Contains the various clock source types available to the kernel.
+pub mod clock {
+    use super::*;
+
+    /// A clock representing the default kernel time source (`CLOCK_MONOTONIC`).
+    pub struct KernelTime;
+
+    /// `CLOCK_MONOTONIC` is monotonic.
+    impl Monotonic for KernelTime {}
+
+    impl Clock for KernelTime {
+        #[inline]
+        fn now() -> Instant<Self> {
+            // SAFETY: It is always safe to call `ktime_get` outside of NMI context.
+            Instant::<Self>::new(unsafe { bindings::ktime_get() })
+        }
+    }
+}
-- 
2.44.0

On 24.03.24 23:33, Boqun Feng wrote:
> Rust Binder will need to read CLOCK_MONOTONIC to compute how many
> milliseconds a transaction has been active for when dumping the current
> state of the Binder driver. This replicates the logic in C Binder [1].
> 
> For a usage example in Rust Binder, see [2].
> 
> Hence add the support for CLOCK_MONOTONIC read.
> 
> The `ktime_get` method cannot be safely called in NMI context. This
> requirement is not checked by these abstractions, but it is intended
> that klint [3] or a similar tool will be used to check it in the future.
> 
> Link: https://lore.kernel.org/lkml/5ac8c0d09392290be789423f0dd78a520b830fab.1682333709.git.zhangchuang3@xiaomi.com/ [1]
> Link: https://r.android.com/3004103 [2]
> Link: https://rust-for-linux.com/klint [3]
> Co-developed-by: Heghedus Razvan <heghedus.razvan@protonmail.com>
> Signed-off-by: Heghedus Razvan <heghedus.razvan@protonmail.com>
> Co-developed-by: Asahi Lina <lina@asahilina.net>
> Signed-off-by: Asahi Lina <lina@asahilina.net>
> Co-developed-by: Alice Ryhl <aliceryhl@google.com>
> Signed-off-by: Alice Ryhl <aliceryhl@google.com>
> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

With the nit fixed:

Reviewed-by: Benno Lossin <benno.lossin@proton.me>

> ---
> @Alice, I still put the link to the usage of Android binder here, if you
> want to remove that, please let me know.
> 
>  rust/kernel/time.rs | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs
> index 0f9f5605ed48..5cd669cbea01 100644
> --- a/rust/kernel/time.rs
> +++ b/rust/kernel/time.rs
> @@ -113,3 +113,22 @@ fn sub(self, other: Self) -> Self::Output {
>          Duration::new(self.inner.wrapping_sub(other.inner))
>      }
>  }
> +
> +/// Contains the various clock source types available to the kernel.
> +pub mod clock {
> +    use super::*;
> +
> +    /// A clock representing the default kernel time source (`CLOCK_MONOTONIC`).
> +    pub struct KernelTime;
> +
> +    /// `CLOCK_MONOTONIC` is monotonic.
> +    impl Monotonic for KernelTime {}
> +
> +    impl Clock for KernelTime {
> +        #[inline]
> +        fn now() -> Instant<Self> {
> +            // SAFETY: It is always safe to call `ktime_get` outside of NMI context.
> +            Instant::<Self>::new(unsafe { bindings::ktime_get() })

I don't think the turbofish syntax (the `::<Self>` part) is needed here.

-- 
Cheers,
Benno

> +        }
> +    }
> +}
> --
> 2.44.0
>

On Tue, Mar 26, 2024 at 05:03:41PM +0000, Benno Lossin wrote:
> On 24.03.24 23:33, Boqun Feng wrote:
> > Rust Binder will need to read CLOCK_MONOTONIC to compute how many
> > milliseconds a transaction has been active for when dumping the current
> > state of the Binder driver. This replicates the logic in C Binder [1].
> > 
> > For a usage example in Rust Binder, see [2].
> > 
> > Hence add the support for CLOCK_MONOTONIC read.
> > 
> > The `ktime_get` method cannot be safely called in NMI context. This
> > requirement is not checked by these abstractions, but it is intended
> > that klint [3] or a similar tool will be used to check it in the future.
> > 
> > Link: https://lore.kernel.org/lkml/5ac8c0d09392290be789423f0dd78a520b830fab.1682333709.git.zhangchuang3@xiaomi.com/ [1]
> > Link: https://r.android.com/3004103 [2]
> > Link: https://rust-for-linux.com/klint [3]
> > Co-developed-by: Heghedus Razvan <heghedus.razvan@protonmail.com>
> > Signed-off-by: Heghedus Razvan <heghedus.razvan@protonmail.com>
> > Co-developed-by: Asahi Lina <lina@asahilina.net>
> > Signed-off-by: Asahi Lina <lina@asahilina.net>
> > Co-developed-by: Alice Ryhl <aliceryhl@google.com>
> > Signed-off-by: Alice Ryhl <aliceryhl@google.com>
> > Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
> 
> With the nit fixed:
> 
> Reviewed-by: Benno Lossin <benno.lossin@proton.me>
> 

Thanks!

> > ---
> > @Alice, I still put the link to the usage of Android binder here, if you
> > want to remove that, please let me know.
> > 
> >  rust/kernel/time.rs | 19 +++++++++++++++++++
> >  1 file changed, 19 insertions(+)
> > 
> > diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs
> > index 0f9f5605ed48..5cd669cbea01 100644
> > --- a/rust/kernel/time.rs
> > +++ b/rust/kernel/time.rs
> > @@ -113,3 +113,22 @@ fn sub(self, other: Self) -> Self::Output {
> >          Duration::new(self.inner.wrapping_sub(other.inner))
> >      }
> >  }
> > +
> > +/// Contains the various clock source types available to the kernel.
> > +pub mod clock {
> > +    use super::*;
> > +
> > +    /// A clock representing the default kernel time source (`CLOCK_MONOTONIC`).
> > +    pub struct KernelTime;
> > +
> > +    /// `CLOCK_MONOTONIC` is monotonic.
> > +    impl Monotonic for KernelTime {}
> > +
> > +    impl Clock for KernelTime {
> > +        #[inline]
> > +        fn now() -> Instant<Self> {
> > +            // SAFETY: It is always safe to call `ktime_get` outside of NMI context.
> > +            Instant::<Self>::new(unsafe { bindings::ktime_get() })
> 
> I don't think the turbofish syntax (the `::<Self>` part) is needed here.
> 

Fixed locally.

Regards,
Boqun

> -- 
> Cheers,
> Benno
> 
> > +        }
> > +    }
> > +}
> > --
> > 2.44.0
> >