diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs index 7320d8715bcc..642c42a520a8 100644 --- a/rust/kernel/time.rs +++ b/rust/kernel/time.rs @@ -25,6 +25,7 @@ //! C header: [`include/linux/ktime.h`](srctree/include/linux/ktime.h). use core::marker::PhantomData; +use core::ops; pub mod delay; pub mod hrtimer; @@ -224,7 +225,7 @@ pub(crate) unsafe fn from_ktime(ktime: bindings::ktime_t) -> Self { } } -impl core::ops::Sub for Instant { +impl ops::Sub for Instant { type Output = Delta; // By the type invariant, it never overflows. @@ -236,6 +237,46 @@ fn sub(self, other: Instant) -> Delta { } } +impl ops::Add for Instant { + type Output = Self; + + #[inline] + fn add(self, rhs: Delta) -> Self::Output { + // INVARIANT: With arithmetic over/underflow checks enabled, this will panic if we overflow + // (e.g. go above `KTIME_MAX`) + let res = self.inner + rhs.nanos; + + // INVARIANT: With overflow checks enabled, we verify here that the value is >= 0 + #[cfg(CONFIG_RUST_OVERFLOW_CHECKS)] + assert!(res >= 0); + + Self { + inner: res, + _c: PhantomData, + } + } +} + +impl ops::Sub for Instant { + type Output = Self; + + #[inline] + fn sub(self, rhs: Delta) -> Self::Output { + // INVARIANT: With arithmetic over/underflow checks enabled, this will panic if we overflow + // (e.g. go above `KTIME_MAX`) + let res = self.inner - rhs.nanos; + + // INVARIANT: With overflow checks enabled, we verify here that the value is >= 0 + #[cfg(CONFIG_RUST_OVERFLOW_CHECKS)] + assert!(res >= 0); + + Self { + inner: res, + _c: PhantomData, + } + } +} + /// A span of time. /// /// This struct represents a span of time, with its value stored as nanoseconds.