From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753077AbbDAAqb (ORCPT ); Tue, 31 Mar 2015 20:46:31 -0400 Received: from mga01.intel.com ([192.55.52.88]:44789 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752994AbbDAAq1 (ORCPT ); Tue, 31 Mar 2015 20:46:27 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.11,503,1422950400"; d="scan'208";a="701158953" Subject: [PATCH 12/16] 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: Tue, 31 Mar 2015 17:46:39 -0700 References: <20150401004623.894DF37A@viggo.jf.intel.com> In-Reply-To: <20150401004623.894DF37A@viggo.jf.intel.com> Message-Id: <20150401004639.23D74681@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 2015-03-31 16:41:59.992449159 -0700 +++ b/arch/x86/mm/mpx.c 2015-03-31 16:41:59.996449339 -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; } _