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 63162C44521 for ; Wed, 21 Jan 2026 12:32:56 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4dx3WB6tVmz2yFg; Wed, 21 Jan 2026 23:32:54 +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=1768998774; cv=none; b=McREWI6YX9igt9AZmuAORyP/XI3QkyN5u0C99R5pmIGidQ06anTxm05dFUB4hn+j7qQYWgspwy58oHi/1uOV07P3AdvWVv0yG9FMlc7swUWG119igjCfS2SYGOejLYjACxrK+43FqBTDax7lLzZQsfhucfdWYCerQstiTsg6biVZg5EqG9GhOVofy/iupBDsRmOyJ7YPoXCDmkEt/+/R/rsGbptbZHeawCHw91a6475TXXvJJxEXxuMfht/8H6WBam5aWugE2zEooJ39FpgR8fQGvrbsnKUsnHKZWz+o1wQaimwYwhMirJCtsA033UAxTsv0umxjUtxtR4KOYxDPDg== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1768998774; c=relaxed/relaxed; bh=qqEAV4XNbENaQF1wnfbJbCZQX0jG6pyPPVu7PJw5gtY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=gfLT58vG4gR64IP040x6W8OVkvXYq5L6vzHxXFv9JYQXIe62TcdAZRMU7drE8xnEVAAeHItWtTrAsptABd5V8ub33Hg74qtf+MqPnmCUeVFThsQN69q/54SfwI2JpCmJ8m6GUaVPB9pZvfqw1b7sQTLkHFfK4pSeFGC2dLqjbew6IZN6Bkqo7YsGkklLriWullcxWVF4NRUDe2FD3MhQfZPOhuUbljIpBIMdB7qJctybqa+4bX/jBmDd4sGzg5ETz5ZAZtkY8D+A2f5VbN9PSptfSGhp8JE7Ehxo4qZJ++Z9JQcvzi0IUvVi6Viamf8feJTRIt4RDrVXjVWPF4vuBg== 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=mark.rutland@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=mark.rutland@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 4dx3W92bJhz2xqD for ; Wed, 21 Jan 2026 23:32:51 +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 D87A81476; Wed, 21 Jan 2026 04:32:12 -0800 (PST) Received: from J2N7QTR9R3 (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 16A163F740; Wed, 21 Jan 2026 04:32:13 -0800 (PST) Date: Wed, 21 Jan 2026 12:32:08 +0000 From: Mark Rutland To: Ryan Roberts 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 Subject: Re: [PATCH v4 3/3] randomize_kstack: Unify random source across arches Message-ID: References: <20260119130122.1283821-4-ryan.roberts@arm.com> <202601210752.6Nsv9et9-lkp@intel.com> <46c7d109-b076-4bb3-9e6e-36c34c546c20@arm.com> 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 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <46c7d109-b076-4bb3-9e6e-36c34c546c20@arm.com> 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(). Mark.