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=-16.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 49B74C433DB for ; Thu, 11 Feb 2021 13:51:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0CC0B64DD8 for ; Thu, 11 Feb 2021 13:51:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231327AbhBKNub (ORCPT ); Thu, 11 Feb 2021 08:50:31 -0500 Received: from mail.kernel.org ([198.145.29.99]:35568 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231912AbhBKNgD (ORCPT ); Thu, 11 Feb 2021 08:36:03 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3B29164E95 for ; Thu, 11 Feb 2021 13:35:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1613050520; bh=rTiqbGm61u+Ivnr3xRKwut6NNnHVY3C/fRPscsmypyY=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=Su/T1oN8vczZIJGjXYaGJFiOFZMBkeXo2R6SLYQYX8MD9hCMwPzNwjmGnz3DlYCyE USM9Nnm1lAXeEeidW1efu1P6RLhNVUo71IdOf5opk0MCnlKFkTOTaa4WNniNMRBcHO HU2Eq2q79zFQ2KRJBKPVhWL440CA9/tV4vqFJ7GO591O48bPfsiF2MfTaKGXnhgt16 WhN7ucWnBs93kHFRrWqFv6CCf1jmBuwpFoscBUayOLnuJVqNPoJ/tBabyyaLsDJJZF R2lAXcPpm0DmjdjWBoQgGI9SNe/fUQDN4fwFA/OWdzqkJAOh6dgRzDf5gSDeWmTqkP 99dYtZiBJT13A== Received: by mail-ot1-f42.google.com with SMTP id o12so5083786ote.12 for ; Thu, 11 Feb 2021 05:35:20 -0800 (PST) X-Gm-Message-State: AOAM533mznIKNPrenwfTq6Bwkz3c9eFGBcEgxBiVMCdwzLir9vSQmjJo 9JIkOye9Wgs0aXAAjI7rg1r5NQ8SCBoZWZpcBek= X-Google-Smtp-Source: ABdhPJxeVig17JlRjMwO/9Ofoer9NvF2kKtNDK0T936SvJbFKJ05bIvbrM7pJkWWw8tXsWhluEon/UXYhgR+n2ISi8o= X-Received: by 2002:a05:6830:1285:: with SMTP id z5mr5686918otp.90.1613050519509; Thu, 11 Feb 2021 05:35:19 -0800 (PST) MIME-Version: 1.0 References: <20210211125602.44248-1-vincenzo.frascino@arm.com> In-Reply-To: <20210211125602.44248-1-vincenzo.frascino@arm.com> From: Ard Biesheuvel Date: Thu, 11 Feb 2021 14:35:08 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] arm64: Fix warning in mte_get_random_tag() To: Vincenzo Frascino Cc: Linux ARM , Linux Kernel Mailing List , kasan-dev , Catalin Marinas , Andrew Morton , Will Deacon , Andrey Konovalov Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 11 Feb 2021 at 13:57, Vincenzo Frascino wrote: > > The simplification of mte_get_random_tag() caused the introduction of the > warning below: > > In file included from arch/arm64/include/asm/kasan.h:9, > from include/linux/kasan.h:16, > from mm/kasan/common.c:14: > mm/kasan/common.c: In function =E2=80=98mte_get_random_tag=E2=80=99: > arch/arm64/include/asm/mte-kasan.h:45:9: warning: =E2=80=98addr=E2=80=99 = is used > uninitialized [-Wuninitialized] > 45 | asm(__MTE_PREAMBLE "irg %0, %0" > | > > Fix the warning initializing the address to NULL. > > Note: mte_get_random_tag() returns a tag and it never dereferences the ad= dress, > hence 'addr' can be safely initialized to NULL. > > Fixes: c8f8de4c0887 ("arm64: kasan: simplify and inline MTE functions") > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Andrey Konovalov > Cc: Andrew Morton > Signed-off-by: Vincenzo Frascino > --- > > This patch is based on linux-next/akpm > > arch/arm64/include/asm/mte-kasan.h | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/mte-kasan.h b/arch/arm64/include/asm/= mte-kasan.h > index 3d58489228c0..b2850b750726 100644 > --- a/arch/arm64/include/asm/mte-kasan.h > +++ b/arch/arm64/include/asm/mte-kasan.h > @@ -40,7 +40,12 @@ static inline u8 mte_get_mem_tag(void *addr) > /* Generate a random tag. */ > static inline u8 mte_get_random_tag(void) > { > - void *addr; > + /* > + * mte_get_random_tag() returns a tag and it > + * never dereferences the address, hence addr > + * can be safely initialized to NULL. > + */ > + void *addr =3D NULL; > > asm(__MTE_PREAMBLE "irg %0, %0" > : "+r" (addr)); > -- > 2.30.0 > Might it be better to simply change the asm constraint to "=3Dr" ? 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Thu, 11 Feb 2021 05:35:19 -0800 (PST) MIME-Version: 1.0 References: <20210211125602.44248-1-vincenzo.frascino@arm.com> In-Reply-To: <20210211125602.44248-1-vincenzo.frascino@arm.com> From: Ard Biesheuvel Date: Thu, 11 Feb 2021 14:35:08 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] arm64: Fix warning in mte_get_random_tag() To: Vincenzo Frascino X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210211_083521_710517_71AB0685 X-CRM114-Status: GOOD ( 22.85 ) 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: Catalin Marinas , Linux Kernel Mailing List , kasan-dev , Andrey Konovalov , Andrew Morton , Will Deacon , Linux ARM Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org T24gVGh1LCAxMSBGZWIgMjAyMSBhdCAxMzo1NywgVmluY2Vuem8gRnJhc2Npbm8KPHZpbmNlbnpv LmZyYXNjaW5vQGFybS5jb20+IHdyb3RlOgo+Cj4gVGhlIHNpbXBsaWZpY2F0aW9uIG9mIG10ZV9n ZXRfcmFuZG9tX3RhZygpIGNhdXNlZCB0aGUgaW50cm9kdWN0aW9uIG9mIHRoZQo+IHdhcm5pbmcg YmVsb3c6Cj4KPiBJbiBmaWxlIGluY2x1ZGVkIGZyb20gYXJjaC9hcm02NC9pbmNsdWRlL2FzbS9r YXNhbi5oOjksCj4gICAgICAgICAgICAgICAgICBmcm9tIGluY2x1ZGUvbGludXgva2FzYW4uaDox NiwKPiAgICAgICAgICAgICAgICAgIGZyb20gbW0va2FzYW4vY29tbW9uLmM6MTQ6Cj4gbW0va2Fz YW4vY29tbW9uLmM6IEluIGZ1bmN0aW9uIOKAmG10ZV9nZXRfcmFuZG9tX3RhZ+KAmToKPiBhcmNo L2FybTY0L2luY2x1ZGUvYXNtL210ZS1rYXNhbi5oOjQ1Ojk6IHdhcm5pbmc6IOKAmGFkZHLigJkg aXMgdXNlZAo+ICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgdW5pbml0 aWFsaXplZCBbLVd1bmluaXRpYWxpemVkXQo+ICAgIDQ1IHwgICAgICAgICBhc20oX19NVEVfUFJF QU1CTEUgImlyZyAlMCwgJTAiCj4gICAgICAgfAo+Cj4gRml4IHRoZSB3YXJuaW5nIGluaXRpYWxp emluZyB0aGUgYWRkcmVzcyB0byBOVUxMLgo+Cj4gTm90ZTogbXRlX2dldF9yYW5kb21fdGFnKCkg cmV0dXJucyBhIHRhZyBhbmQgaXQgbmV2ZXIgZGVyZWZlcmVuY2VzIHRoZSBhZGRyZXNzLAo+IGhl bmNlICdhZGRyJyBjYW4gYmUgc2FmZWx5IGluaXRpYWxpemVkIHRvIE5VTEwuCj4KPiBGaXhlczog YzhmOGRlNGMwODg3ICgiYXJtNjQ6IGthc2FuOiBzaW1wbGlmeSBhbmQgaW5saW5lIE1URSBmdW5j dGlvbnMiKQo+IENjOiBDYXRhbGluIE1hcmluYXMgPGNhdGFsaW4ubWFyaW5hc0Bhcm0uY29tPgo+ IENjOiBXaWxsIERlYWNvbiA8d2lsbEBrZXJuZWwub3JnPgo+IENjOiBBbmRyZXkgS29ub3ZhbG92 IDxhbmRyZXlrbnZsQGdvb2dsZS5jb20+Cj4gQ2M6IEFuZHJldyBNb3J0b24gPGFrcG1AbGludXgt Zm91bmRhdGlvbi5vcmc+Cj4gU2lnbmVkLW9mZi1ieTogVmluY2Vuem8gRnJhc2Npbm8gPHZpbmNl bnpvLmZyYXNjaW5vQGFybS5jb20+Cj4gLS0tCj4KPiBUaGlzIHBhdGNoIGlzIGJhc2VkIG9uIGxp bnV4LW5leHQvYWtwbQo+Cj4gIGFyY2gvYXJtNjQvaW5jbHVkZS9hc20vbXRlLWthc2FuLmggfCA3 ICsrKysrKy0KPiAgMSBmaWxlIGNoYW5nZWQsIDYgaW5zZXJ0aW9ucygrKSwgMSBkZWxldGlvbigt KQo+Cj4gZGlmZiAtLWdpdCBhL2FyY2gvYXJtNjQvaW5jbHVkZS9hc20vbXRlLWthc2FuLmggYi9h cmNoL2FybTY0L2luY2x1ZGUvYXNtL210ZS1rYXNhbi5oCj4gaW5kZXggM2Q1ODQ4OTIyOGMwLi5i Mjg1MGI3NTA3MjYgMTAwNjQ0Cj4gLS0tIGEvYXJjaC9hcm02NC9pbmNsdWRlL2FzbS9tdGUta2Fz YW4uaAo+ICsrKyBiL2FyY2gvYXJtNjQvaW5jbHVkZS9hc20vbXRlLWthc2FuLmgKPiBAQCAtNDAs NyArNDAsMTIgQEAgc3RhdGljIGlubGluZSB1OCBtdGVfZ2V0X21lbV90YWcodm9pZCAqYWRkcikK PiAgLyogR2VuZXJhdGUgYSByYW5kb20gdGFnLiAqLwo+ICBzdGF0aWMgaW5saW5lIHU4IG10ZV9n ZXRfcmFuZG9tX3RhZyh2b2lkKQo+ICB7Cj4gLSAgICAgICB2b2lkICphZGRyOwo+ICsgICAgICAg LyoKPiArICAgICAgICAqIG10ZV9nZXRfcmFuZG9tX3RhZygpIHJldHVybnMgYSB0YWcgYW5kIGl0 Cj4gKyAgICAgICAgKiBuZXZlciBkZXJlZmVyZW5jZXMgdGhlIGFkZHJlc3MsIGhlbmNlIGFkZHIK PiArICAgICAgICAqIGNhbiBiZSBzYWZlbHkgaW5pdGlhbGl6ZWQgdG8gTlVMTC4KPiArICAgICAg ICAqLwo+ICsgICAgICAgdm9pZCAqYWRkciA9IE5VTEw7Cj4KPiAgICAgICAgIGFzbShfX01URV9Q UkVBTUJMRSAiaXJnICUwLCAlMCIKPiAgICAgICAgICAgICAgICAgOiAiK3IiIChhZGRyKSk7Cj4g LS0KPiAyLjMwLjAKPgoKTWlnaHQgaXQgYmUgYmV0dGVyIHRvIHNpbXBseSBjaGFuZ2UgdGhlIGFz bSBjb25zdHJhaW50IHRvICI9ciIgPwoKX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fX19fX18KbGludXgtYXJtLWtlcm5lbCBtYWlsaW5nIGxpc3QKbGludXgtYXJtLWtl cm5lbEBsaXN0cy5pbmZyYWRlYWQub3JnCmh0dHA6Ly9saXN0cy5pbmZyYWRlYWQub3JnL21haWxt YW4vbGlzdGluZm8vbGludXgtYXJtLWtlcm5lbAo=