From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965991AbaLLTMx (ORCPT ); Fri, 12 Dec 2014 14:12:53 -0500 Received: from mga11.intel.com ([192.55.52.93]:11727 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965713AbaLLTMd (ORCPT ); Fri, 12 Dec 2014 14:12:33 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,862,1389772800"; d="scan'208";a="428315362" Subject: [RFC][PATCH 5/8] x86, mpx: Add temporary variable to reduce masking To: linux-kernel@vger.kernel.org Cc: tglx@linutronix.de, x86@kernel.org, Dave Hansen , dave.hansen@linux.intel.com From: Dave Hansen Date: Fri, 12 Dec 2014 11:12:20 -0800 References: <20141212191213.579887D2@viggo.jf.intel.com> In-Reply-To: <20141212191213.579887D2@viggo.jf.intel.com> Message-Id: <20141212191220.B8944E5D@viggo.jf.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dave Hansen When we allocate a bounds table, we call mmap(), then add a "valid" bit to the value before storing it in to the bounds directory. If we fail along the way, we go and mask that valid bit _back_ out. That seems a little silly, and this makes it much more clear when we have a plain address versus an actual table _entry_. Signed-off-by: Dave Hansen --- b/arch/x86/mm/mpx.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff -puN arch/x86/mm/mpx.c~mpx-remove-unnecessary-masking arch/x86/mm/mpx.c --- a/arch/x86/mm/mpx.c~mpx-remove-unnecessary-masking 2014-12-12 11:11:40.599015745 -0800 +++ b/arch/x86/mm/mpx.c 2014-12-12 11:11:40.602015880 -0800 @@ -421,6 +421,7 @@ static int allocate_bt(long __user *bd_e unsigned long expected_old_val = 0; unsigned long actual_old_val = 0; unsigned long bt_addr; + unsigned long bd_new_entry; int ret = 0; /* @@ -433,7 +434,7 @@ static int allocate_bt(long __user *bd_e /* * Set the valid flag (kinda like _PAGE_PRESENT in a pte) */ - bt_addr = bt_addr | MPX_BD_ENTRY_VALID_FLAG; + bd_new_entry = bt_addr | MPX_BD_ENTRY_VALID_FLAG; /* * Go poke the address of the new bounds table in to the @@ -447,7 +448,7 @@ static int allocate_bt(long __user *bd_e * of the MPX code that have to pagefault_disable(). */ ret = user_atomic_cmpxchg_inatomic(&actual_old_val, bd_entry, - expected_old_val, bt_addr); + expected_old_val, bd_new_entry); if (ret) goto out_unmap; @@ -477,7 +478,7 @@ static int allocate_bt(long __user *bd_e } return 0; out_unmap: - vm_munmap(bt_addr & MPX_BT_ADDR_MASK, MPX_BT_SIZE_BYTES); + vm_munmap(bt_addr, MPX_BT_SIZE_BYTES); return ret; } _