From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753141AbeDQPl1 (ORCPT ); Tue, 17 Apr 2018 11:41:27 -0400 Received: from 9pmail.ess.barracuda.com ([64.235.150.225]:42663 "EHLO 9pmail.ess.barracuda.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753089AbeDQPlZ (ORCPT ); Tue, 17 Apr 2018 11:41:25 -0400 From: Matt Redfearn To: James Hogan , Ralf Baechle CC: , Matt Redfearn , Subject: [PATCH v2 4/4] MIPS: memset.S: Add comments to fault fixup handlers Date: Tue, 17 Apr 2018 16:40:03 +0100 Message-ID: <1523979603-492-4-git-send-email-matt.redfearn@mips.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1523979603-492-1-git-send-email-matt.redfearn@mips.com> References: <1523979603-492-1-git-send-email-matt.redfearn@mips.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [192.168.155.41] X-BESS-ID: 1523979677-637139-30405-48655-1 X-BESS-VER: 2018.4-r1804121647 X-BESS-Apparent-Source-IP: 12.201.5.28 X-BESS-Outbound-Spam-Score: 0.00 X-BESS-Outbound-Spam-Report: Code version 3.2, rules version 3.2.2.192083 Rule breakdown below pts rule name description ---- ---------------------- -------------------------------- 0.00 BSF_BESS_OUTBOUND META: BESS Outbound X-BESS-Outbound-Spam-Status: SCORE=0.00 using account:ESS59374 scores of KILL_LEVEL=7.0 tests=BSF_BESS_OUTBOUND X-BESS-BRTS-Status: 1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It is not immediately obvious what the expected inputs to these fault handlers is and how they calculate the number of unset bytes. Having stared deeply at this in order to fix some corner cases, add some comments to addist those who follow. Signed-off-by: Matt Redfearn --- Changes in v2: - Add comments to fault handlers in new, separate, patch. arch/mips/lib/memset.S | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/arch/mips/lib/memset.S b/arch/mips/lib/memset.S index 1cc306520a55..a06dabe99d4b 100644 --- a/arch/mips/lib/memset.S +++ b/arch/mips/lib/memset.S @@ -231,16 +231,25 @@ #ifdef CONFIG_CPU_MIPSR6 .Lbyte_fixup\@: + /* + * unset_bytes = current_addr + 1 + * a2 = t0 + 1 + */ PTR_SUBU a2, $0, t0 jr ra PTR_ADDIU a2, 1 #endif /* CONFIG_CPU_MIPSR6 */ .Lfirst_fixup\@: + /* unset_bytes already in a2 */ jr ra nop .Lfwd_fixup\@: + /* + * unset_bytes = partial_start_addr + #bytes - fault_addr + * a2 = t1 + (a2 & 3f) - $28->task->BUADDR + */ PTR_L t0, TI_TASK($28) andi a2, 0x3f LONG_L t0, THREAD_BUADDR(t0) @@ -249,6 +258,10 @@ LONG_SUBU a2, t0 .Lpartial_fixup\@: + /* + * unset_bytes = partial_end_addr + #bytes - fault_addr + * a2 = a0 + (a2 & STORMASK) - $28->task->BUADDR + */ PTR_L t0, TI_TASK($28) andi a2, STORMASK LONG_L t0, THREAD_BUADDR(t0) @@ -257,10 +270,15 @@ LONG_SUBU a2, t0 .Llast_fixup\@: + /* unset_bytes already in a2 */ jr ra nop .Lsmall_fixup\@: + /* + * unset_bytes = end_addr - current_addr + 1 + * a2 = t1 - a0 + 1 + */ PTR_SUBU a2, t1, a0 jr ra PTR_ADDIU a2, 1 -- 2.7.4