From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752952AbbCZSg4 (ORCPT ); Thu, 26 Mar 2015 14:36:56 -0400 Received: from mga09.intel.com ([134.134.136.24]:57640 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752776AbbCZSdj (ORCPT ); Thu, 26 Mar 2015 14:33:39 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.11,474,1422950400"; d="scan'208";a="671116942" Subject: [PATCH 13/17] x86, mpx: Add temporary variable to reduce masking To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, tglx@linutronix.de, Dave Hansen , dave.hansen@linux.intel.com From: Dave Hansen Date: Thu, 26 Mar 2015 11:33:50 -0700 References: <20150326183327.64807530@viggo.jf.intel.com> In-Reply-To: <20150326183327.64807530@viggo.jf.intel.com> Message-Id: <20150326183350.FE5F2E47@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 2015-03-26 11:27:33.173486813 -0700 +++ b/arch/x86/mm/mpx.c 2015-03-26 11:27:33.176486948 -0700 @@ -431,6 +431,7 @@ 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; /* @@ -443,7 +444,7 @@ 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 @@ -457,7 +458,7 @@ 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; @@ -488,7 +489,7 @@ static int allocate_bt(long __user *bd_e trace_mpx_new_bounds_table(bt_addr); 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; } _