From: sashiko-bot@kernel.org
To: "Andi Kleen" <ak@kernel.org>
Cc: linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org
Subject: Re: [RFC PATCH v2 09/11] ptwrite uprobes: Use atomic patching for multinop sites
Date: Thu, 17 Sep 2026 23:32:58 +0000 [thread overview]
Message-ID: <20260917233258.87C731F000FF@smtp.kernel.org> (raw)
In-Reply-To: <20260917230127.924985-10-ak@kernel.org>
> The earlier multinop patching is not quite safe because the cross
> modified CPU could be already executing on a later nop when the
> cross patching occurs. The Intel SDM allows cross modification
> by larger stores as long as they are aligned. AMD has a similar
> guarantee.
>
> Support GCC function-entry patch sites is the main motivation for
> multinop, and these sites are always aligned.
>
> So enforce 8 bytes alignment of the multinop and use a safe RMW 8 byte store
> to overwrite the 5 byte sequence. This assumes that the code is not
> changing in parallel, but if that happens cross modification safety
> is probably the smallest of the issues.
>
> Assisted-by: omp:gpt-5.6-luna
> Signed-off-by: Andi Kleen <ak@kernel.org>
Sashiko has reviewed this patch and found no issues. It looks great!
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260917230127.924985-2-ak@kernel.org?part=9
next prev parent reply other threads:[~2026-09-17 23:32 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-17 23:00 ptwrite uprobes v2 Andi Kleen
2026-09-17 23:00 ` [RFC PATCH v2 01/11] ptwrite uprobes: Add infrastructure for ptwrite uprobes Andi Kleen
2026-09-17 23:19 ` sashiko-bot
2026-09-17 23:00 ` [RFC PATCH v2 02/11] ptwrite uprobes: Add minimal low level support for x86 Andi Kleen
2026-09-17 23:25 ` sashiko-bot
2026-09-17 23:00 ` [RFC PATCH v2 03/11] ptwrite uprobes: Add a sample module to exercise interface Andi Kleen
2026-09-17 23:20 ` sashiko-bot
2026-09-17 23:00 ` [RFC PATCH v2 04/11] ptwrite uprobes: Add support to tracing infrastructure Andi Kleen
2026-09-17 23:23 ` sashiko-bot
2026-09-17 23:00 ` [RFC PATCH v2 05/11] ptwrite uprobes: Factor file-backed instruction reads Andi Kleen
2026-09-17 23:14 ` sashiko-bot
2026-09-17 23:00 ` [RFC PATCH v2 06/11] ptwrite uprobes: Add basic memory references Andi Kleen
2026-09-17 23:17 ` sashiko-bot
2026-09-17 23:00 ` [RFC PATCH v2 07/11] ptwrite uprobes: Add multinop support Andi Kleen
2026-09-17 23:22 ` sashiko-bot
2026-09-17 23:00 ` [RFC PATCH v2 08/11] ptwrite uprobes: Support instruction punning Andi Kleen
2026-09-17 23:27 ` sashiko-bot
2026-09-17 23:00 ` [RFC PATCH v2 09/11] ptwrite uprobes: Use atomic patching for multinop sites Andi Kleen
2026-09-17 23:32 ` sashiko-bot [this message]
2026-09-17 23:00 ` [RFC PATCH v2 10/11] ptwrite uprobes: Add a tutorial and overview documentation Andi Kleen
2026-09-17 23:21 ` sashiko-bot
2026-09-17 23:00 ` [RFC PATCH v2 11/11] ptwrite uprobes: Add kernel self tests Andi Kleen
2026-09-17 23:28 ` sashiko-bot
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