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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4C614C433EF for ; Tue, 22 Feb 2022 19:58:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235347AbiBVT7A (ORCPT ); Tue, 22 Feb 2022 14:59:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36174 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230522AbiBVT65 (ORCPT ); Tue, 22 Feb 2022 14:58:57 -0500 Received: from elvis.franken.de (elvis.franken.de [193.175.24.41]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id D6781DE2D8; Tue, 22 Feb 2022 11:58:30 -0800 (PST) Received: from uucp (helo=alpha) by elvis.franken.de with local-bsmtp (Exim 3.36 #1) id 1nMbIs-0006bB-00; Tue, 22 Feb 2022 20:58:30 +0100 Received: by alpha.franken.de (Postfix, from userid 1000) id 9ABD8C26B8; Tue, 22 Feb 2022 20:58:06 +0100 (CET) Date: Tue, 22 Feb 2022 20:58:06 +0100 From: Thomas Bogendoerfer To: Arnd Bergmann Cc: linux-mips , Linux Kernel Mailing List Subject: Re: [PATCH] MIPS: Handle address errors for accesses above CPU max virtual user address Message-ID: <20220222195806.GA17107@alpha.franken.de> References: <20220222155345.138861-1-tsbogend@alpha.franken.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 22, 2022 at 06:04:07PM +0100, Arnd Bergmann wrote: > On Tue, Feb 22, 2022 at 4:53 PM Thomas Bogendoerfer > wrote: > > > > Address errors have always been treated as unaliged accesses and handled > > as such. But address errors are also issued for illegal accesses like > > user to kernel space or accesses outside of implemented spaces. This > > change implements Linux exception handling for accesses to the illegal > > space above the CPU implemented maximum virtual user address and the > > MIPS 64bit architecture maximum. With this we can now use a fixed value > > for the maximum task size on every MIPS CPU and get a more optimized > > access_ok(). > > > > Signed-off-by: Thomas Bogendoerfer > > Thank you for addressing this. Should I add this patch to my series > ahead of "mips: use simpler access_ok()"? That way I can keep it all > in my asm-generic tree as a series for 5.18. yes please add it to your series. > > arch/mips/kernel/unaligned.c | 17 +++++++++++++++++ > > 1 file changed, 17 insertions(+) > > > > diff --git a/arch/mips/kernel/unaligned.c b/arch/mips/kernel/unaligned.c > > index df4b708c04a9..7b5aba5df02e 100644 > > --- a/arch/mips/kernel/unaligned.c > > +++ b/arch/mips/kernel/unaligned.c > > @@ -1480,6 +1480,23 @@ asmlinkage void do_ade(struct pt_regs *regs) > > prev_state = exception_enter(); > > perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, > > 1, regs, regs->cp0_badvaddr); > > + > > +#ifdef CONFIG_64BIT > > + /* > > + * check, if we are hitting space between CPU implemented maximum > > + * virtual user address and 64bit maximum virtual user address > > + * and do exception handling to get EFAULTs for get_user/put_user > > + */ > > + if ((regs->cp0_badvaddr >= (1UL << cpu_vmbits)) && > > + (regs->cp0_badvaddr < XKSSEG)) { > > It might be clearer to use TASK_SIZE_MAX here instead of XKSSEG, > to match the check in access_ok(). If you like, I can change that while > applying. I had TASK_SIZE_MAX in an intermediate version, but decided to go with XKSSEG, because it's what this check is about. It's about checking what the MIPS architecture defined. Thomas. -- Crap can work. Given enough thrust pigs will fly, but it's not necessarily a good idea. [ RFC1925, 2.3 ]