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x-vs=clean score=-100 state=0 X-ME-VSCategory: clean X-CM-Envelope: MS4wfLtRK/SlQCAWPnxn3TfntSV0vuAqEEoRmf0G5a0GyBlzt+La312oeDHucuzvUlSYd+I+cTza/qZtNkyJmM9GNA7mUVXepkozkaEa0tOfwAd1mOBeyna+ N9UdMOwP24DnHZ6Re5FUO6b3ca1NJluBo7gRGt9y0qh0TEVuoMgDda7k2kF2NNX4IJgp7PrOHZRXNZ9b6hJIRA8j8igpSopAv6YWnGeHjTHrupGVK/GctEF+ X-CM-Analysis: v=2.3 cv=Tq3Iegfh c=1 sm=1 tr=0 a=UK1r566ZdBxH71SXbqIOeA==:117 a=UK1r566ZdBxH71SXbqIOeA==:17 a=IkcTkHD0fZMA:10 a=Kd1tUaAdevIA:10 a=yPCof4ZbAAAA:8 a=VwQbUJbxAAAA:8 a=PA8RhHZH_tBapMXY7tUA:9 a=QEXdDO2ut3YA:10 a=AjGcO6oz07-iQ99wixmX:22 X-ME-CMScore: 0 X-ME-CMCategory: none Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754548AbeD3SF3 (ORCPT ); Mon, 30 Apr 2018 14:05:29 -0400 Received: from aserp2130.oracle.com ([141.146.126.79]:51386 "EHLO aserp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753480AbeD3SFF (ORCPT ); Mon, 30 Apr 2018 14:05:05 -0400 Subject: Re: [Xen-devel] [PATCH 1/4] xen/PVH: Replace GDT_ENTRY with explicit constant To: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Cc: linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, jgross@suse.com, stable@vger.kernel.org References: <20180430162339.17143-1-boris.ostrovsky@oracle.com> <20180430162339.17143-2-boris.ostrovsky@oracle.com> <20180430165704.bkce56nzx3giodbd@MacBook-Pro-de-Roger.local> From: Boris Ostrovsky Openpgp: preference=signencrypt Autocrypt: addr=boris.ostrovsky@oracle.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180430165704.bkce56nzx3giodbd@MacBook-Pro-de-Roger.local> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8879 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=781 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1804300174 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 04/30/2018 12:57 PM, Roger Pau Monné wrote: > On Mon, Apr 30, 2018 at 12:23:36PM -0400, Boris Ostrovsky wrote: >> Latest binutils release (2.29.1) will no longer allow proper computation >> of GDT entries on 32-bits, with warning: >> >> arch/x86/xen/xen-pvh.S: Assembler messages: >> arch/x86/xen/xen-pvh.S:150: Warning: shift count out of range (32 is not between 0 and 31) >> arch/x86/xen/xen-pvh.S:150: Warning: shift count out of range (40 is not between 0 and 31) >> arch/x86/xen/xen-pvh.S:150: Warning: shift count out of range (32 is not between 0 and 31) >> arch/x86/xen/xen-pvh.S:152: Warning: shift count out of range (32 is not between 0 and 31) >> arch/x86/xen/xen-pvh.S:152: Warning: shift count out of range (40 is not between 0 and 31) >> arch/x86/xen/xen-pvh.S:152: Warning: shift count out of range (32 is not between 0 and 31) >> >> Use explicit value of the entry instead of using GDT_ENTRY() macro. >> >> Signed-off-by: Boris Ostrovsky >> Cc: stable@vger.kernel.org >> --- >> arch/x86/xen/xen-pvh.S | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/arch/x86/xen/xen-pvh.S b/arch/x86/xen/xen-pvh.S >> index e1a5fbe..934f7d4 100644 >> --- a/arch/x86/xen/xen-pvh.S >> +++ b/arch/x86/xen/xen-pvh.S >> @@ -145,11 +145,11 @@ gdt_start: >> .quad 0x0000000000000000 /* NULL descriptor */ >> .quad 0x0000000000000000 /* reserved */ >> #ifdef CONFIG_X86_64 >> - .quad GDT_ENTRY(0xa09a, 0, 0xfffff) /* __KERNEL_CS */ >> + .quad 0x00af9a000000ffff /* __BOOT_CS */ >> #else >> - .quad GDT_ENTRY(0xc09a, 0, 0xfffff) /* __KERNEL_CS */ >> + .quad 0x00cf9a000000ffff /* __BOOT_CS */ > Maybe it would be cleaner to use something like: I actually considered all of these and ended up with a raw number because it seems to be a convention in kernel (and Xen too, apparently)  to use raw values in .S files. Kernel is using now GDT_ENTRY_INIT() which is a C macro. There is one other location where GDT_INIT() is used (arch/x86/boot/pm.c) and, incidentally, it also generates this warning IIRC. I really don't want to move definition to C code just to use a macro --- I don't think C code needs to be exposed to this GDT. > > .word 0xffff /* limit */ > .word 0 /* base */ > .byte 0 /* base */ > .byte 0x9a /* access */ > #ifdef CONFIG_X86_64 > .byte 0xaf /* flags plus limit */ > #else > .byte 0xcf /* flags plus limit */ > #endif > .byte 0 /* base */ I, in fact, started with something like this. But if you repeat this 4 times you will probably see why I decided against it ;-) -boris > > Or try to fix the GDT_ENTRY macro, maybe if you prepend extra 0's to > make the values 64bit that would prevent the warnings? > > Or declare the GDT in enlighten_pvh in C and use it here? > > Also, IIRC the base/limit values are ignored in long mode. > > Thanks, Roger.