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 X-Spam-Level: X-Spam-Status: No, score=-15.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 77350C433E9 for ; Thu, 21 Jan 2021 15:59:52 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3983623A24 for ; Thu, 21 Jan 2021 15:59:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3983623A24 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=gywgln8bQ58pl6fU4PV5f6NeN26pwOb1kujpciMd7bs=; b=QUcIYmVOCZVZeUeLpXiPr06Es Lz7YtSJQkgjHOtZ6Yu+PBbkpZ9r39DhsepMFpd2X9FD1dSOyNevS07JmhCHpIxHP+C3cu1kkv7Lf6 /EfOdyyjr3ouabYOlGDDeAo/mdoLbUgl2v4lAYiTWmZyXio98InfTTZA7WIPsCV+C9BJLiMs7nbw/ N2eeZw3IuPeNa8uQP0kv9sERTClAKicLBnjzNH9Grs+VYpxlP5Row2SKjQwQPqaDXgCKYNq3VCWBC IlkkhHON68wURFQEdZAUA5lbSUrt/6aTuJ5CKca1KnUNuoONvqCOD3oaU87St3meU9g633CFL/GIC wPpww9Y4g==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l2cLw-0004m0-E1; Thu, 21 Jan 2021 15:58:32 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l2cLt-0004l5-Rk for linux-arm-kernel@lists.infradead.org; Thu, 21 Jan 2021 15:58:30 +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 66F7A139F; Thu, 21 Jan 2021 07:58:25 -0800 (PST) Received: from [10.37.8.32] (unknown [10.37.8.32]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 740DD3F68F; Thu, 21 Jan 2021 07:58:23 -0800 (PST) Subject: Re: [PATCH v2 1/2] arm64: Fix kernel address detection of __is_lm_address() To: Mark Rutland References: <20210121131956.23246-1-vincenzo.frascino@arm.com> <20210121131956.23246-2-vincenzo.frascino@arm.com> <20210121151206.GI48431@C02TD0UTHF1T.local> <95727b4c-4578-6eb5-b518-208482e8ba62@arm.com> <20210121154938.GJ48431@C02TD0UTHF1T.local> From: Vincenzo Frascino Message-ID: <5a389787-4f6a-7577-22fc-f5594409e1ae@arm.com> Date: Thu, 21 Jan 2021 16:02:14 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210121154938.GJ48431@C02TD0UTHF1T.local> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210121_105829_996834_7F9F19BE X-CRM114-Status: GOOD ( 30.91 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Andrey Konovalov , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, Leon Romanovsky , Alexander Potapenko , Dmitry Vyukov , Catalin Marinas , Andrey Ryabinin , Will Deacon , Ard Biesheuvel , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 1/21/21 3:49 PM, Mark Rutland wrote: > On Thu, Jan 21, 2021 at 03:30:51PM +0000, Vincenzo Frascino wrote: >> On 1/21/21 3:12 PM, Mark Rutland wrote: >>> On Thu, Jan 21, 2021 at 01:19:55PM +0000, Vincenzo Frascino wrote: >>>> Currently, the __is_lm_address() check just masks out the top 12 bits >>>> of the address, but if they are 0, it still yields a true result. >>>> This has as a side effect that virt_addr_valid() returns true even for >>>> invalid virtual addresses (e.g. 0x0). >>> >>> When it was added, __is_lm_address() was intended to distinguish valid >>> kernel virtual addresses (i.e. those in the TTBR1 address range), and >>> wasn't intended to do anything for addresses outside of this range. See >>> commit: >>> >>> ec6d06efb0bac6cd ("arm64: Add support for CONFIG_DEBUG_VIRTUAL") >>> >>> ... where it simply tests a bit. >>> >>> So I believe that it's working as intended (though this is poorly >>> documented), but I think you're saying that usage isn't aligned with >>> that intent. Given that, I'm not sure the fixes tag is right; I think it >>> has never had the semantic you're after. >>> >> I did not do much thinking on the intended semantics. I based my interpretation >> on what you are saying (the usage is not aligned with the intent). Based on what >> you are are saying, I will change the patch description removing the "Fix" term. > > Thanks! I assume that also means removing the fixes tag. > Obviously ;) >>> I had thought the same was true for virt_addr_valid(), and that wasn't >>> expected to be called for VAs outside of the kernel VA range. Is it >>> actually safe to call that with NULL on other architectures? >> >> I am not sure on this, did not do any testing outside of arm64. > > I think it'd be worth checking, if we're going to use this in common > code. > Ok, I will run some tests and let you know. >>> I wonder if it's worth virt_addr_valid() having an explicit check for >>> the kernel VA range, instead. >> >> I have no strong opinion either way even if personally I feel that modifying >> __is_lm_address() is more clear. Feel free to propose something. > > Sure; I'm happy for it to live within __is_lm_address() if that's > simpler overall, given it doesn't look like it's making that more > complex or expensive. > >>>> Fix the detection checking that it's actually a kernel address starting >>>> at PAGE_OFFSET. >>>> >>>> Fixes: f4693c2716b35 ("arm64: mm: extend linear region for 52-bit VA configurations") >>>> Cc: Catalin Marinas >>>> Cc: Will Deacon >>>> Suggested-by: Catalin Marinas >>>> Signed-off-by: Vincenzo Frascino >>>> --- >>>> arch/arm64/include/asm/memory.h | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h >>>> index 18fce223b67b..e04ac898ffe4 100644 >>>> --- a/arch/arm64/include/asm/memory.h >>>> +++ b/arch/arm64/include/asm/memory.h >>>> @@ -249,7 +249,7 @@ static inline const void *__tag_set(const void *addr, u8 tag) >>>> /* >>>> * The linear kernel range starts at the bottom of the virtual address space. >>>> */ >>>> -#define __is_lm_address(addr) (((u64)(addr) & ~PAGE_OFFSET) < (PAGE_END - PAGE_OFFSET)) >>>> +#define __is_lm_address(addr) (((u64)(addr) ^ PAGE_OFFSET) < (PAGE_END - PAGE_OFFSET)) >>> >>> If we're going to make this stronger, can we please expand the comment >>> with the intended semantic? Otherwise we're liable to break this in >>> future. >> >> Based on your reply on the above matter, if you agree, I am happy to extend the >> comment. > > Works for me; how about: > > /* > * Check whether an arbitrary address is within the linear map, which > * lives in the [PAGE_OFFSET, PAGE_END) interval at the bottom of the > * kernel's TTBR1 address range. > */ > > ... with "arbitrary" being the key word. > Sounds good to me! I will post the new version after confirming the behavior of virt_addr_valid() on the other architectures. > Thanks, > Mark. > -- Regards, Vincenzo _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel