From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx49bGe7ALPvqPeGSU36roli2BpjrSmnXSPWG2YeAj3hKMuQS61DiKreRmTKn23q7oWhHqeVH ARC-Seal: i=1; a=rsa-sha256; t=1524089750; cv=none; d=google.com; s=arc-20160816; b=bPgkIYHGtGohrhrV0SLPK6efX/1SDjTAZzmMpA54cXpn9w+EIqRJGApCpqa0m5Kme7 CZJf2v13faWuIjsfnobhs1wNs4ZVYnbFPeyw8OD22mocBRGu9S4FS8vqZ4F2Kw1YDZXt 9SUH/2bj3vC9qoKB34M08DacoGcoP9Jeg0Hgud3xi/SjRoNeZGv2USIPLexQszphq7I3 tZkZr2roYnBqJlJZzkq94Apzsll9oP35c/CJpCY96wJbaH08rSu5kjkQ5HRj+r8w3tO2 8JPi8uG2gx4xB/2+cssywaoZg7tWpSl6zmi2n6sH3plIZhVSipq5hDcd/+DKouhbJx4E LAYw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-language:content-transfer-encoding:in-reply-to:mime-version :user-agent:date:message-id:autocrypt:openpgp:from:references:cc:to :subject:dkim-signature:delivered-to:list-id:list-subscribe :list-unsubscribe:list-help:list-post:precedence:mailing-list :arc-authentication-results; bh=uvxD4iSbQH9WJVabfMLQNudXlUsd3hnIcA5SSWtqJIE=; b=AYzTUbEkP6Iy4/UHK/qP0mGrHkoCZnr4eiMJRZnJT4qOX4IccdEbYPSPVIXXNqhS86 EneryGqJPyUESICPv6VC01YsYVfDk8t96KntdYUN9HvVcyw+kRzQFHKab2KSRDRxPRli QpAHo3Roh2rh0iHWqb50z/hPZMQGnmEc9sbN0IAb0gnY7a3MQhR108B1kXdGlf5VC99n o54G8vcFRk5wr8tuHIlarCla2KeH+iBY3IjN4eaIZ+sNbm9IBQ3KSOhohijtEJlkxVVz XvXFomoMOzuHtKEgEq2sunooTmlS6dUYZUp2Db+MyaTcbC1ILNF8wq16Pjz4dBinUSTC zuQQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@oracle.com header.s=corp-2017-10-26 header.b=PbKwra8t; spf=pass (google.com: domain of kernel-hardening-return-13047-gregkh=linuxfoundation.org@lists.openwall.com designates 195.42.179.200 as permitted sender) smtp.mailfrom=kernel-hardening-return-13047-gregkh=linuxfoundation.org@lists.openwall.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=oracle.com Authentication-Results: mx.google.com; dkim=pass header.i=@oracle.com header.s=corp-2017-10-26 header.b=PbKwra8t; spf=pass (google.com: domain of kernel-hardening-return-13047-gregkh=linuxfoundation.org@lists.openwall.com designates 195.42.179.200 as permitted sender) smtp.mailfrom=kernel-hardening-return-13047-gregkh=linuxfoundation.org@lists.openwall.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=oracle.com Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm List-Post: List-Help: List-Unsubscribe: List-Subscribe: Subject: Re: [PATCHv2] x86/xen: Remove use of VLAs To: Laura Abbott , Juergen Gross 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: <20180418170832.8798-1-labbott@redhat.com> From: Boris Ostrovsky Openpgp: preference=signencrypt Autocrypt: addr=boris.ostrovsky@oracle.com; prefer-encrypt=mutual; keydata= xsFNBFH8CgsBEAC0KiOi9siOvlXatK2xX99e/J3OvApoYWjieVQ9232Eb7GzCWrItCzP8FUV PQg8rMsSd0OzIvvjbEAvaWLlbs8wa3MtVLysHY/DfqRK9Zvr/RgrsYC6ukOB7igy2PGqZd+M MDnSmVzik0sPvB6xPV7QyFsykEgpnHbvdZAUy/vyys8xgT0PVYR5hyvhyf6VIfGuvqIsvJw5 C8+P71CHI+U/IhsKrLrsiYHpAhQkw+Zvyeml6XSi5w4LXDbF+3oholKYCkPwxmGdK8MUIdkM d7iYdKqiP4W6FKQou/lC3jvOceGupEoDV9botSWEIIlKdtm6C4GfL45RD8V4B9iy24JHPlom woVWc0xBZboQguhauQqrBFooHO3roEeM1pxXjLUbDtH4t3SAI3gt4dpSyT3EvzhyNQVVIxj2 FXnIChrYxR6S0ijSqUKO0cAduenhBrpYbz9qFcB/GyxD+ZWY7OgQKHUZMWapx5bHGQ8bUZz2 SfjZwK+GETGhfkvNMf6zXbZkDq4kKB/ywaKvVPodS1Poa44+B9sxbUp1jMfFtlOJ3AYB0WDS Op3d7F2ry20CIf1Ifh0nIxkQPkTX7aX5rI92oZeu5u038dHUu/dO2EcuCjl1eDMGm5PLHDSP 0QUw5xzk1Y8MG1JQ56PtqReO33inBXG63yTIikJmUXFTw6lLJwARAQABzTNCb3JpcyBPc3Ry b3Zza3kgKFdvcmspIDxib3Jpcy5vc3Ryb3Zza3lAb3JhY2xlLmNvbT7CwXgEEwECACIFAlH8 CgsCGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEIredpCGysGyasEP/j5xApopUf4g 9Fl3UxZuBx+oduuw3JHqgbGZ2siA3EA4bKwtKq8eT7ekpApn4c0HA8TWTDtgZtLSV5IdH+9z JimBDrhLkDI3Zsx2CafL4pMJvpUavhc5mEU8myp4dWCuIylHiWG65agvUeFZYK4P33fGqoaS VGx3tsQIAr7MsQxilMfRiTEoYH0WWthhE0YVQzV6kx4wj4yLGYPPBtFqnrapKKC8yFTpgjaK jImqWhU9CSUAXdNEs/oKVR1XlkDpMCFDl88vKAuJwugnixjbPFTVPyoC7+4Bm/FnL3iwlJVE qIGQRspt09r+datFzPqSbp5Fo/9m4JSvgtPp2X2+gIGgLPWp2ft1NXHHVWP19sPgEsEJXSr9 tskM8ScxEkqAUuDs6+x/ISX8wa5Pvmo65drN+JWA8EqKOHQG6LUsUdJolFM2i4Z0k40BnFU/ kjTARjrXW94LwokVy4x+ZYgImrnKWeKac6fMfMwH2aKpCQLlVxdO4qvJkv92SzZz4538az1T m+3ekJAimou89cXwXHCFb5WqJcyjDfdQF857vTn1z4qu7udYCuuV/4xDEhslUq1+GcNDjAhB nNYPzD+SvhWEsrjuXv+fDONdJtmLUpKs4Jtak3smGGhZsqpcNv8nQzUGDQZjuCSmDqW8vn2o hWwveNeRTkxh+2x1Qb3GT46uzsFNBFH8CgsBEADGC/yx5ctcLQlB9hbq7KNqCDyZNoYu1HAB Hal3MuxPfoGKObEktawQPQaSTB5vNlDxKihezLnlT/PKjcXC2R1OjSDinlu5XNGc6mnky03q yymUPyiMtWhBBftezTRxWRslPaFWlg/h/Y1iDuOcklhpr7K1h1jRPCrf1yIoxbIpDbffnuyz kuto4AahRvBU4Js4sU7f/btU+h+e0AcLVzIhTVPIz7PM+Gk2LNzZ3/on4dnEc/qd+ZZFlOQ4 KDN/hPqlwA/YJsKzAPX51L6Vv344pqTm6Z0f9M7YALB/11FO2nBB7zw7HAUYqJeHutCwxm7i BDNt0g9fhviNcJzagqJ1R7aPjtjBoYvKkbwNu5sWDpQ4idnsnck4YT6ctzN4I+6lfkU8zMzC gM2R4qqUXmxFIS4Bee+gnJi0Pc3KcBYBZsDK44FtM//5Cp9DrxRQOh19kNHBlxkmEb8kL/pw XIDcEq8MXzPBbxwHKJ3QRWRe5jPNpf8HCjnZz0XyJV0/4M1JvOua7IZftOttQ6KnM4m6WNIZ 2ydg7dBhDa6iv1oKdL7wdp/rCulVWn8R7+3cRK95SnWiJ0qKDlMbIN8oGMhHdin8cSRYdmHK kTnvSGJNlkis5a+048o0C6jI3LozQYD/W9wq7MvgChgVQw1iEOB4u/3FXDEGulRVko6xCBU4 SQARAQABwsFfBBgBAgAJBQJR/AoLAhsMAAoJEIredpCGysGyfvMQAIywR6jTqix6/fL0Ip8G jpt3uk//QNxGJE3ZkUNLX6N786vnEJvc1beCu6EwqD1ezG9fJKMl7F3SEgpYaiKEcHfoKGdh 30B3Hsq44vOoxR6zxw2B/giADjhmWTP5tWQ9548N4VhIZMYQMQCkdqaueSL+8asp8tBNP+TJ PAIIANYvJaD8xA7sYUXGTzOXDh2THWSvmEWWmzok8er/u6ZKdS1YmZkUy8cfzrll/9hiGCTj u3qcaOM6i/m4hqtvsI1cOORMVwjJF4+IkC5ZBoeRs/xW5zIBdSUoC8L+OCyj5JETWTt40+lu qoqAF/AEGsNZTrwHJYu9rbHH260C0KYCNqmxDdcROUqIzJdzDKOrDmebkEVnxVeLJBIhYZUd t3Iq9hdjpU50TA6sQ3mZxzBdfRgg+vaj2DsJqI5Xla9QGKD+xNT6v14cZuIMZzO7w0DoojM4 ByrabFsOQxGvE0w9Dch2BDSI2Xyk1zjPKxG1VNBQVx3flH37QDWpL2zlJikW29Ws86PHdthh Fm5PY8YtX576DchSP6qJC57/eAAe/9ztZdVAdesQwGb9hZHJc75B+VNm4xrh/PJO6c1THqdQ 19WVJ+7rDx3PhVncGlbAOiiiE3NOFPJ1OQYxPKtpBUukAlOTnkKE6QcA4zckFepUkfmBV1wM Jg6OxFYd01z+a+oL Message-ID: Date: Wed, 18 Apr 2018 18:17:04 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180418170832.8798-1-labbott@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8867 signatures=668698 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1804180201 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1598104627872343121?= X-GMAIL-MSGID: =?utf-8?q?1598123934455317964?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 04/18/2018 01:08 PM, Laura Abbott wrote: > There's an ongoing effort to remove VLAs[1] from the kernel to eventually > turn on -Wvla. It turns out, the few VLAs in use in Xen produce only a > single entry array that is always bounded by GDT_SIZE. Clean up the code to > get rid of the VLA and the loop. > > [1] https://lkml.org/lkml/2018/3/7/621 > > Signed-off-by: Laura Abbott > --- > v2: Updated the code to reflect that we know size is always bounded by > GDT_SIZE. This gets rid of the array and the loop. I can throw a few > more comments in there if someone thinks they need to be updated. > --- > arch/x86/xen/enlighten_pv.c | 84 ++++++++++++++++----------------------------- > 1 file changed, 29 insertions(+), 55 deletions(-) > > diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c > index c36d23aa6c35..1254f2fa3a89 100644 > --- a/arch/x86/xen/enlighten_pv.c > +++ b/arch/x86/xen/enlighten_pv.c > @@ -421,45 +421,32 @@ 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); > - unsigned long frames[pages]; > - int f; > - > - /* > - * A GDT can be up to 64k in size, which corresponds to 8192 > - * 8-byte entries, or 16 4k pages.. > - */ > + unsigned long pfn, mfn; > + int level; > + pte_t *ptep; > + void *virt; > > - BUG_ON(size > 65536); > + BUG_ON(size > GDT_SIZE); I'd probably BUG_ON(size>PAGE_SIZE) because that's what we are really trying to avoid. Maybe with a comment that we expect GDT_SIZE at most, and it is less than PAGE_SIZE. I can fix it while committing if you don't object. Reviewed-by: Boris Ostrovsky