From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx4+KsAFP4QRnNeaLvjksS6Gdj494yYPpnSf/QiSdHEPfw3Pmz/uFm01wGCpgBwpyjGyrz9OP ARC-Seal: i=1; a=rsa-sha256; t=1524008063; cv=none; d=google.com; s=arc-20160816; b=p24sfgnfjk3NyQnnnUccqN91vc/0NR4PFe9L4EupWAPOvo5teGPHDVLkHHqcZ+C9DA oxnxJlSEhdL+X88J5q41kDnhwsVa/2MHU3VS3eezefPW8htNOHMJUDAWKYkqFlaGjB5Y uTvaDTeT03hAIwnDDuyYKIAgt/TMwf5tN5a3ae7AJhBoNcG9dvql7egNrdOk2AF+wf1s wQwrDJw2UJDv8/e950juXHrLVBw5Cv/IReWivUu0ZF8qWWxXZpB/14TmieRgf05PvaLp ry0wRqH7FnfDC/kbD8mEgr+sqYaxokG74pdO+1V5721sDPfL/17rdLXcEZV/4k/UozjA 0WgA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:content-language:in-reply-to:mime-version :user-agent:date:message-id:from:references:cc:to:subject :delivered-to:list-id:list-subscribe:list-unsubscribe:list-help :list-post:precedence:mailing-list:arc-authentication-results; bh=2qU/UnvG2sElhgauqaVlQO0u0Bf2BaSoFePP/V30NS8=; b=HMKH+FNocRDYZYAu7hAApRE+ro2Te/6YWG+MGQyu6ymjah4V2rGU2eno1RbFcKszb5 2U1QHG1bFvGHPJT0jRSaS1vLZQT4c0ugdtf2tsIF/GeQWT51Ny1ROz2nmwVx+xPoBmSM 3M2/sQjIdgsOfM33t9DOTWSNVmMIeC478TM4uLXIm6Cm45BS8RM7tMDP96JMN3RO21rp ld2TxBv6e1MD93eujsvGq77TqfWACG+cKYW1iD+A5tfTmmGTx2bfrqETmYz85kNYnDEw MFtJoEgma1Y2GI9u8ANzWkhUdyv3grJ2jFpNkQxO9nsiTqCyXH7ItCtmPreI45Rfc0HX hLSw== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of kernel-hardening-return-13034-gregkh=linuxfoundation.org@lists.openwall.com designates 195.42.179.200 as permitted sender) smtp.mailfrom=kernel-hardening-return-13034-gregkh=linuxfoundation.org@lists.openwall.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=redhat.com Authentication-Results: mx.google.com; spf=pass (google.com: domain of kernel-hardening-return-13034-gregkh=linuxfoundation.org@lists.openwall.com designates 195.42.179.200 as permitted sender) smtp.mailfrom=kernel-hardening-return-13034-gregkh=linuxfoundation.org@lists.openwall.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=redhat.com Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm List-Post: List-Help: List-Unsubscribe: List-Subscribe: Subject: Re: [PATCH] x86/xen: Remove use of VLAs To: Juergen Gross , Boris Ostrovsky Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com References: <20180413221146.28476-1-labbott@redhat.com> <7cf66c00-74c2-62bb-81f5-4332313a5a6e@oracle.com> From: Laura Abbott Message-ID: <9fe26cf5-01dc-1fb0-25fd-29bf8615047f@redhat.com> Date: Tue, 17 Apr 2018 16:33:57 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1597670729617678421?= X-GMAIL-MSGID: =?utf-8?q?1598038278768539046?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 04/17/2018 12:16 AM, Juergen Gross wrote: > On 16/04/18 15:27, Boris Ostrovsky wrote: >> On 04/13/2018 06:11 PM, Laura Abbott wrote: >>> There's an ongoing effort to remove VLAs[1] from the kernel to eventually >>> turn on -Wvla. The few VLAs in use have an upper bound based on a size >>> of 64K. This doesn't produce an excessively large stack so just switch >>> the upper bound. >>> >>> [1] https://lkml.org/lkml/2018/3/7/621 >>> >>> Signed-off-by: Laura Abbott >>> --- >>> arch/x86/xen/enlighten_pv.c | 6 ++---- >>> 1 file changed, 2 insertions(+), 4 deletions(-) >>> >>> diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c >>> index c36d23aa6c35..d96a5a535cbb 100644 >>> --- a/arch/x86/xen/enlighten_pv.c >>> +++ b/arch/x86/xen/enlighten_pv.c >>> @@ -421,8 +421,7 @@ static void xen_load_gdt(const struct desc_ptr *dtr) >>> { >>> unsigned long va = dtr->address; >>> unsigned int size = dtr->size + 1; >>> - unsigned pages = DIV_ROUND_UP(size, PAGE_SIZE); >> >> >> >> Isn't dtr->size always either GDT_SIZE or 0? > > GDT_SIZE - 1 :-) > >>> - unsigned long frames[pages]; >>> + unsigned long frames[DIV_ROUND_UP(SZ_64K, PAGE_SIZE)]; > > So we could just go with one frame and modify the BUG_ON() further below > accordingly. > Do you want to just remove the loop as well since we're never going to do more than one frame? We end up with net code deletion. Thanks, Laura > > Juergen >