Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934262AbdDSM4g (ORCPT ); Wed, 19 Apr 2017 08:56:36 -0400 Received: from pegase1.c-s.fr ([93.17.236.30]:5049 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934224AbdDSM4b (ORCPT ); Wed, 19 Apr 2017 08:56:31 -0400 Message-Id: <58f17a04cee5726467ef4e283dfbd7da68fa6ab4.1492606298.git.christophe.leroy@c-s.fr> In-Reply-To: References: From: Christophe Leroy Subject: [PATCH 2/5] powerpc/mm: split store_updates_sp() in two parts in do_page_fault() To: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Scott Wood Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Date: Wed, 19 Apr 2017 14:56:26 +0200 (CEST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2114 Lines: 61 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() 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