From nobody Sat Oct 4 04:59:53 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F18882D372A for ; Wed, 20 Aug 2025 20:37:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755722248; cv=none; b=Ly2bWlgXDjVzj8cYYpGLwuRNlHUpim3kPbsgPR5ApFcdlnr+DXGu03Oim1eLdKGhkKd+alw+PMTm1y9bw1LK6LxNRoFIYQ3JvIcFZR3qtD4jncFDji6VyGoO85m5Fy2GSQYnoTpR7oCnIZ95TguaKvAQGjQMKol/aqjIn+UYVJA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755722248; c=relaxed/simple; bh=Y88gS618ooHfwSEeQ/x1FVp6qCHn0OyxAAhi8dccVfI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=S97qSf9MSfD9hlEzY93A7GhpdOeB6rNF4wOGJBknwW3nQyy+t118ZH4AlzUcE7K7OLAYLbBRHqhT/7fSTnlpuExx4BdJT/RgDjEx0KYXvDaOHYT59vHl1bo4HolezYlG18EXuvZnNg+lO0v5GXU4x8myYBWsAUdy3+jWG9At6GI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=BooksOVZ; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="BooksOVZ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1755722245; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=HPGI7YO0+Ykjlr33gJ/vmqFT7fgdrtVLz3J06wkC9Ys=; b=BooksOVZvlauiGvleMrRnk83Jt+3ktCRvPkf5xd06lovccawjr8uCvJXVIYN9bboXN0uBg uWwkYDOVEFpdB0S4m9KpBS2GVlVP4LDA0Yc9joCxNmuz3KFR33fA9hXt82sm/GdbL9IuGl TnLby3u9YEk8aa/EBtMfgCAq8WEX2fM= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-170-1Hv_GtGINrm6MbjSZlx32A-1; Wed, 20 Aug 2025 16:37:22 -0400 X-MC-Unique: 1Hv_GtGINrm6MbjSZlx32A-1 X-Mimecast-MFC-AGG-ID: 1Hv_GtGINrm6MbjSZlx32A_1755722239 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 8BEE91956089; Wed, 20 Aug 2025 20:37:19 +0000 (UTC) Received: from chopper.redhat.com (unknown [10.22.81.238]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id B7F9C19A4C99; Wed, 20 Aug 2025 20:37:15 +0000 (UTC) From: Lyude Paul To: rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Andreas Hindborg , FUJITA Tomonori Cc: Boqun Feng , Frederic Weisbecker , Anna-Maria Behnsen , John Stultz , Stephen Boyd , Miguel Ojeda , Alex Gaynor , Gary Guo , =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= , Benno Lossin , Alice Ryhl , Trevor Gross , Danilo Krummrich Subject: [PATCH v3 1/2] rust: time: Implement Add/Sub for Instant Date: Wed, 20 Aug 2025 16:26:43 -0400 Message-ID: <20250820203704.731588-2-lyude@redhat.com> In-Reply-To: <20250820203704.731588-1-lyude@redhat.com> References: <20250820203704.731588-1-lyude@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Content-Type: text/plain; charset="utf-8" In order to copy the behavior rust currently follows for basic arithmetic operations and panic if the result of an addition or subtraction results in a value that would violate the invariants of Instant, but only if the kernel has overflow checking for rust enabled. Signed-off-by: Lyude Paul Reviewed-by: Alice Ryhl Reviewed-by: Andreas Hindborg Reviewed-by: Daniel Almeida Reviewed-by: FUJITA Tomonori --- V2: * Change behavior in ops::{Add,Sub} so that we panic on overflows under the same conditions that arithmetic operations in rust would panic by default. V3: * Don't forget to update the commit message this time! rust/kernel/time.rs | 43 ++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 42 insertions(+), 1 deletion(-) diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs index 64c8dcf548d63..4bd7a8a009f3e 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). =20 use core::marker::PhantomData; +use core::ops; =20 pub mod delay; pub mod hrtimer; @@ -202,7 +203,7 @@ pub(crate) fn as_nanos(&self) -> i64 { } } =20 -impl core::ops::Sub for Instant { +impl ops::Sub for Instant { type Output =3D Delta; =20 // By the type invariant, it never overflows. @@ -214,6 +215,46 @@ fn sub(self, other: Instant) -> Delta { } } =20 +impl ops::Add for Instant { + type Output =3D 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 =3D self.inner + rhs.nanos; + + // INVARIANT: With overflow checks enabled, we verify here that th= e value is >=3D 0 + #[cfg(CONFIG_RUST_OVERFLOW_CHECKS)] + assert!(res >=3D 0); + + Self { + inner: res, + _c: PhantomData, + } + } +} + +impl ops::Sub for Instant { + type Output =3D 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 =3D self.inner - rhs.nanos; + + // INVARIANT: With overflow checks enabled, we verify here that th= e value is >=3D 0 + #[cfg(CONFIG_RUST_OVERFLOW_CHECKS)] + assert!(res >=3D 0); + + Self { + inner: res, + _c: PhantomData, + } + } +} + /// A span of time. /// /// This struct represents a span of time, with its value stored as nanose= conds. --=20 2.50.0