Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1167670AbdDXJMN (ORCPT ); Mon, 24 Apr 2017 05:12:13 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:42855 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1167660AbdDXJME (ORCPT ); Mon, 24 Apr 2017 05:12:04 -0400 From: "Aneesh Kumar K.V" To: Christophe Leroy , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Scott Wood Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH 2/5] powerpc/mm: split store_updates_sp() in two parts in do_page_fault() In-Reply-To: <58f17a04cee5726467ef4e283dfbd7da68fa6ab4.1492606298.git.christophe.leroy@c-s.fr> References: <58f17a04cee5726467ef4e283dfbd7da68fa6ab4.1492606298.git.christophe.leroy@c-s.fr> Date: Mon, 24 Apr 2017 14:41:01 +0530 MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-MML: disable x-cbid: 17042409-0052-0000-0000-000002330362 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17042409-0053-0000-0000-0000080DA963 Message-Id: <87wpaa187u.fsf@skywalker.in.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-04-24_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=1 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1703280000 definitions=main-1704240159 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2351 Lines: 66 Christophe Leroy writes: > Only the get_user() in store_updates_sp() has to be done outside > the mm semaphore. All the comparison can be done within the semaphore, > so only when really needed. > > As we got a DSI exception, the address pointed by regs->nip is > obviously valid, otherwise we would have had a instruction exception. > So __get_user() can be used instead of get_user() > Reviewed-by: Aneesh Kumar K.V > Signed-off-by: Christophe Leroy > --- > arch/powerpc/mm/fault.c | 13 +++++-------- > 1 file changed, 5 insertions(+), 8 deletions(-) > > diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c > index 67fefb59d40e..9d21e5fd383d 100644 > --- a/arch/powerpc/mm/fault.c > +++ b/arch/powerpc/mm/fault.c > @@ -73,12 +73,8 @@ static inline int notify_page_fault(struct pt_regs *regs) > * Check whether the instruction at regs->nip is a store using > * an update addressing form which will update r1. > */ > -static int store_updates_sp(struct pt_regs *regs) > +static int store_updates_sp(unsigned int inst) > { > - unsigned int inst; > - > - if (get_user(inst, (unsigned int __user *)regs->nip)) > - return 0; > /* check for 1 in the rA field */ > if (((inst >> 16) & 0x1f) != 1) > return 0; > @@ -207,7 +203,8 @@ int do_page_fault(struct pt_regs *regs, unsigned long address, > int trap = TRAP(regs); > int is_exec = trap == 0x400; > int fault; > - int rc = 0, store_update_sp = 0; > + int rc = 0; > + unsigned int inst = 0; > > #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) > /* > @@ -288,7 +285,7 @@ int do_page_fault(struct pt_regs *regs, unsigned long address, > * mmap_sem held > */ > if (is_write && user_mode(regs)) > - store_update_sp = store_updates_sp(regs); > + __get_user(inst, (unsigned int __user *)regs->nip); > > if (user_mode(regs)) > flags |= FAULT_FLAG_USER; > @@ -358,7 +355,7 @@ int do_page_fault(struct pt_regs *regs, unsigned long address, > * between the last mapped region and the stack will > * expand the stack rather than segfaulting. > */ > - if (address + 2048 < uregs->gpr[1] && !store_update_sp) > + if (address + 2048 < uregs->gpr[1] && !store_updates_sp(inst)) > goto bad_area; > } > if (expand_stack(vma, address)) > -- > 2.12.0