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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 0A9C5E9A047 for ; Wed, 18 Feb 2026 15:21:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To: Subject:MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=bskqCuK8HJnFoRmwgPXR0Ld07qYYJOsH3AwU9jR4jMU=; b=S55yQ/ZI1chAuw 4EgM9jL2Mcq6pFvboGTq8NqBvikobSkOUHpR/QwLr213EnOaWDi56O9vQ6nN6t5ROwcT0UMe9NCHs 8fmt5lcPQu/GwrveXR5hVWAqWgb78vSb7bAwUIbQcFqWTgKuvdH4ig+N/tBhxkeA2VLEH67JJKNrZ Gx22yXuBuQBAVDMW3LBnSCbK02+7l41grli+/T6zbFB2TDkdI4KGHj0Ww+ikeS6Rcenj9Jm1L51sh ItPwEF4kgpGyHCy88Q5Q775JO3z4p8GlBIY6EEfcS4LAH6JmnxnHv/e2HLr35mc8XXxULXBQN8Xib iN9eDuWYs/GquCu+8IIQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vsjM7-0000000A0xd-1gxL; Wed, 18 Feb 2026 15:20:47 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vsjM4-0000000A0x2-2qkz; Wed, 18 Feb 2026 15:20:46 +0000 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 B9997339; Wed, 18 Feb 2026 07:20:33 -0800 (PST) Received: from [10.57.81.199] (unknown [10.57.81.199]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 990193F7F5; Wed, 18 Feb 2026 07:20:34 -0800 (PST) Message-ID: <8531da33-a4dc-48ac-abf3-c831d4493afb@arm.com> Date: Wed, 18 Feb 2026 15:20:32 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 3/3] randomize_kstack: Unify random source across arches Content-Language: en-GB To: Mark Rutland Cc: kernel test robot , 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 , Kees Cook , "Gustavo A. R. Silva" , Arnd Bergmann , "Jason A. Donenfeld" , Ard Biesheuvel , Jeremy Linton , David Laight , llvm@lists.linux.dev, oe-kbuild-all@lists.linux.dev, 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 References: <20260119130122.1283821-4-ryan.roberts@arm.com> <202601210752.6Nsv9et9-lkp@intel.com> <46c7d109-b076-4bb3-9e6e-36c34c546c20@arm.com> From: Ryan Roberts In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260218_072044_818256_85F66006 X-CRM114-Status: GOOD ( 24.40 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On 21/01/2026 12:32, Mark Rutland wrote: > On Wed, Jan 21, 2026 at 10:52:21AM +0000, Ryan Roberts wrote: >> On 20/01/2026 23:50, kernel test robot wrote: >>> Hi Ryan, >>> >>> kernel test robot noticed the following build warnings: >>> >>> [auto build test WARNING on akpm-mm/mm-everything] >>> [also build test WARNING on linus/master v6.19-rc6 next-20260119] >>> [cannot apply to tip/sched/core kees/for-next/hardening kees/for-next/execve] >>> [If your patch is applied to the wrong git tree, kindly drop us a note. >>> And when submitting patch, we suggest to use '--base' as documented in >>> https://git-scm.com/docs/git-format-patch#_base_tree_information] >>> >>> url: https://github.com/intel-lab-lkp/linux/commits/Ryan-Roberts/randomize_kstack-Maintain-kstack_offset-per-task/20260119-210329 >>> base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything >>> patch link: https://lore.kernel.org/r/20260119130122.1283821-4-ryan.roberts%40arm.com >>> patch subject: [PATCH v4 3/3] randomize_kstack: Unify random source across arches >>> config: x86_64-allmodconfig (https://download.01.org/0day-ci/archive/20260121/202601210752.6Nsv9et9-lkp@intel.com/config) >>> compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261) >>> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260121/202601210752.6Nsv9et9-lkp@intel.com/reproduce) >>> >>> If you fix the issue in a separate patch/commit (i.e. not just a new version of >>> the same patch/commit), kindly add following tags >>> | Reported-by: kernel test robot >>> | Closes: https://lore.kernel.org/oe-kbuild-all/202601210752.6Nsv9et9-lkp@intel.com/ >>> >>> All warnings (new ones prefixed by >>): >>> >>>>> vmlinux.o: warning: objtool: do_syscall_64+0x2c: call to preempt_count_add() leaves .noinstr.text section >>>>> vmlinux.o: warning: objtool: __do_fast_syscall_32+0x3d: call to preempt_count_add() leaves .noinstr.text section >> >> Hmm, clearly Dave was correct not to rush this through... yuck. I'll take a >> look, but I guess there is no rush if this won't go into -next until shortly >> after -rc1. > > Sorry, I should have checked the entry sequencing more thoroughly when I > reviewed this,. > > From a quick look, I suspect the right thing to do is to pull the call > to add_random_kstack_offset() a bit later in a few cases; after the > entry logic has run, and after instrumentation_begin() (if the arch code > uses that), such that it doesn't matter if this gets instrumented. > > Considering the callers of add_random_kstack_offset(), if we did that: > > * arm64 is fine as-is. > > * loongarch is fine as-is. > > * powerpc's system_call_exception() would need this moved after the > user_exit_irqoff(). Given that function is notrace rather than > noinstr, it looks like there are bigger extant issues here. > > * riscv is fine as-is. > > * s390's __do_syscall() would need this moved after > enter_from_user_mode(). > > * On x86: > - do_int80_emulation() is fine as-is. > - int80_emulation() is fine as-is. > - do_int80_syscall_32() would need this moved after > instrumentation_begin(). > - __do_fast_syscall_32() would need this moved after > instrumentation_begin(). > - do_syscall_64() would need this moved after instrumentation_begin(). Thanks for the detailed suggestions, Mark. I've taken this approach, and assuming perf testing doesn't throw up any issue, I'm going to revert back to using the out-of-line version of prandom_u32_state() and will drop patch 2. Thanks, Ryan > > Mark. _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv