From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 34D46C433EF for ; Thu, 18 Nov 2021 11:08:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1D15861A3D for ; Thu, 18 Nov 2021 11:08:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343689AbhKRLLv (ORCPT ); Thu, 18 Nov 2021 06:11:51 -0500 Received: from foss.arm.com ([217.140.110.172]:39486 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343604AbhKRLLW (ORCPT ); Thu, 18 Nov 2021 06:11:22 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id ACE881FB; Thu, 18 Nov 2021 03:08:21 -0800 (PST) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 26D7E3F5A1; Thu, 18 Nov 2021 03:08:19 -0800 (PST) Date: Thu, 18 Nov 2021 11:08:14 +0000 From: Mark Rutland To: Marco Elver Cc: "Paul E. McKenney" , Alexander Potapenko , Boqun Feng , Borislav Petkov , Dmitry Vyukov , Ingo Molnar , Josh Poimboeuf , Peter Zijlstra , Thomas Gleixner , Waiman Long , Will Deacon , kasan-dev@googlegroups.com, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org Subject: Re: [PATCH v2 01/23] kcsan: Refactor reading of instrumented memory Message-ID: <20211118110813.GA5233@lakrids.cambridge.arm.com> References: <20211118081027.3175699-1-elver@google.com> <20211118081027.3175699-2-elver@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211118081027.3175699-2-elver@google.com> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 18, 2021 at 09:10:05AM +0100, Marco Elver wrote: > Factor out the switch statement reading instrumented memory into a > helper read_instrumented_memory(). > > No functional change. > > Signed-off-by: Marco Elver Nice cleanup! Acked-by: Mark Rutland Mark. > --- > kernel/kcsan/core.c | 51 +++++++++++++++------------------------------ > 1 file changed, 17 insertions(+), 34 deletions(-) > > diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c > index 4b84c8e7884b..6bfd3040f46b 100644 > --- a/kernel/kcsan/core.c > +++ b/kernel/kcsan/core.c > @@ -325,6 +325,21 @@ static void delay_access(int type) > udelay(delay); > } > > +/* > + * Reads the instrumented memory for value change detection; value change > + * detection is currently done for accesses up to a size of 8 bytes. > + */ > +static __always_inline u64 read_instrumented_memory(const volatile void *ptr, size_t size) > +{ > + switch (size) { > + case 1: return READ_ONCE(*(const u8 *)ptr); > + case 2: return READ_ONCE(*(const u16 *)ptr); > + case 4: return READ_ONCE(*(const u32 *)ptr); > + case 8: return READ_ONCE(*(const u64 *)ptr); > + default: return 0; /* Ignore; we do not diff the values. */ > + } > +} > + > void kcsan_save_irqtrace(struct task_struct *task) > { > #ifdef CONFIG_TRACE_IRQFLAGS > @@ -482,23 +497,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned > * Read the current value, to later check and infer a race if the data > * was modified via a non-instrumented access, e.g. from a device. > */ > - old = 0; > - switch (size) { > - case 1: > - old = READ_ONCE(*(const u8 *)ptr); > - break; > - case 2: > - old = READ_ONCE(*(const u16 *)ptr); > - break; > - case 4: > - old = READ_ONCE(*(const u32 *)ptr); > - break; > - case 8: > - old = READ_ONCE(*(const u64 *)ptr); > - break; > - default: > - break; /* ignore; we do not diff the values */ > - } > + old = read_instrumented_memory(ptr, size); > > /* > * Delay this thread, to increase probability of observing a racy > @@ -511,23 +510,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned > * racy access. > */ > access_mask = ctx->access_mask; > - new = 0; > - switch (size) { > - case 1: > - new = READ_ONCE(*(const u8 *)ptr); > - break; > - case 2: > - new = READ_ONCE(*(const u16 *)ptr); > - break; > - case 4: > - new = READ_ONCE(*(const u32 *)ptr); > - break; > - case 8: > - new = READ_ONCE(*(const u64 *)ptr); > - break; > - default: > - break; /* ignore; we do not diff the values */ > - } > + new = read_instrumented_memory(ptr, size); > > diff = old ^ new; > if (access_mask) > -- > 2.34.0.rc2.393.gf8c9666880-goog >