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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7DE02CA5FA7 for ; Tue, 20 Jan 2026 16:33:00 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4dwXtg0SY7z2xQB; Wed, 21 Jan 2026 03:32:59 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1768926779; cv=none; b=ZiL6dDu+oS0XkF/wOQ4hrqM7Cw6IBdjZAA8B8fwO2m/mkgg2kAwCKXEB95n2z65K3WH/BfPNa4p2f+wvqT3lXMV+Qrapz93F8Z+8DCYdUZayLEcZoFAUr+9icWDpTb+DVvSx3S9m861aXeWv5U09a4mMPY1HMfxFj9+b2wXQy/gOkqruIwu5xmUDb5pDsqMFCdSCRS2DMXCaWqkWz3C1BByZPr1kbpkNAknoktj+eV3BqMk3hSprm7L78lpH2a+kwKmD8bWoi3RRDhRZgI+LQMI0RxNWm744au2n+ghhlE/QRM4WgWAZh3Ih9PQZUstwe3sHWypuEENLXhOB/34ozQ== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1768926779; c=relaxed/relaxed; bh=pzCqaWRw4l8YZiXRlEaKsY2UZqzEryF7b+9WjJwCLVI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=V/ELUvUGMKXJDhRla5qie3U6yzo/XLAO3Q4eaJmJjpyoOaZuLS+pdTq50ZC/5RW2B3mdMiN4WYG5RVBCbqXBnSiM/MS/4yo/MohQDK6mQU1h/XtE5Co3sG1SHnYrmU49/wMgd0WWj71V5D1fAWQFEc/jIaZtsc98TW1fHpGUN1KDV+MP/9rFzJABfxr8hrjOgsT6Ku4hC8kasM+i4fKM34SxNvSGfPe1rf9EAIRKIrl3ciVPCyxNM7CR88n/Yc5Rf8YcVtYaBCj9+1BCjmoPY4Q1rZCfIQa5AhlbzcDs0Qn5IVpSXHuI4Rs26p+lzEhEUrvtB8N4gzbh6wXZzVa4IQ== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass (client-ip=217.140.110.172; helo=foss.arm.com; envelope-from=ryan.roberts@arm.com; receiver=lists.ozlabs.org) smtp.mailfrom=arm.com Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=arm.com (client-ip=217.140.110.172; helo=foss.arm.com; envelope-from=ryan.roberts@arm.com; receiver=lists.ozlabs.org) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lists.ozlabs.org (Postfix) with ESMTP id 4dwXtd73pvz2x9M for ; Wed, 21 Jan 2026 03:32:56 +1100 (AEDT) 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 6B3771476; Tue, 20 Jan 2026 08:32:16 -0800 (PST) Received: from [10.1.39.200] (XHFQ2J9959.cambridge.arm.com [10.1.39.200]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BFE823F694; Tue, 20 Jan 2026 08:32:18 -0800 (PST) Message-ID: <785a7d90-babe-43af-93a6-c220c1877bcf@arm.com> Date: Tue, 20 Jan 2026 16:32:17 +0000 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 0/3] Fix bugs and performance of kstack offset randomisation Content-Language: en-GB To: Kees Cook , Dave Hansen , Catalin Marinas , Will Deacon , Huacai Chen , Madhavan Srinivasan , Michael Ellerman , Paul Walmsley , Palmer Dabbelt , Albert Ou , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "Gustavo A. R. Silva" , Arnd Bergmann , Mark Rutland , "Jason A. Donenfeld" , Ard Biesheuvel , Jeremy Linton , David Laight Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-hardening@vger.kernel.org References: <20260119130122.1283821-1-ryan.roberts@arm.com> <20fb97f1-7e50-485a-bdfd-a2901d20ec84@intel.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 19/01/2026 16:44, Kees Cook wrote: > > > On January 19, 2026 8:00:00 AM PST, Dave Hansen wrote: >> On 1/19/26 05:01, Ryan Roberts wrote: >>> x86 (AWS Sapphire Rapids): >>> +-----------------+--------------+-------------+---------------+ >>> | Benchmark | Result Class | v6.18-rc5 | per-task-prng | >>> | | | rndstack-on | | >>> | | | | | >>> +=================+==============+=============+===============+ >>> | syscall/getpid | mean (ns) | (R) 13.32% | (R) 4.60% | >>> | | p99 (ns) | (R) 13.38% | (R) 18.08% | >>> | | p99.9 (ns) | 16.26% | (R) 19.38% | >> >> Like you noted, this is surprising. This would be a good thing to make >> sure it goes in very early after -rc1 and gets plenty of wide testing. > > Right, we are pretty late in the dev cycle (rc6). It would be prudent to get this into -next after the coming rc1 (1 month from now). > > On the other hand, the changes are pretty "binary" in the sense that mistakes should be VERY visible right away. Would it be better to take this into -next immediately instead? I don't think this question was really addressed to me, but I'll give my opinion anyway; I agree it's pretty binary - it will either work or it will explode. I've tested on arm64 and x86_64 so I have high confidence that it works. If you get it into -next ASAP it has 3 weeks to soak before the merge window opens right? (Linus said he would do an -rc8 this cycle). That feels like enough time to me. But it's your tree ;-) Thanks, Ryan > >> But I don't see any problems with the approach, and the move to common >> code looks like a big win as well: > > Agreed; I think it's looking great. >