From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932833AbdKDLU5 (ORCPT ); Sat, 4 Nov 2017 07:20:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:36956 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756627AbdKDLUF (ORCPT ); Sat, 4 Nov 2017 07:20:05 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3791E21911 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=luto@kernel.org From: Andy Lutomirski To: X86 ML Cc: Borislav Petkov , "linux-kernel@vger.kernel.org" , Andy Lutomirski Subject: [PATCH 2/5] selftests/x86/ldt_gdt: Robustify against set_thread_area() and LAR oddities Date: Sat, 4 Nov 2017 04:19:49 -0700 Message-Id: X-Mailer: git-send-email 2.13.6 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Bits 19:16 of LAR's result are undefined, and some upcoming improvements to the test case seem to trigger this. Mask off those bits to avoid spurious failures. commit 5b781c7e317f ("x86/tls: Forcibly set the accessed bit in TLS segments") adds a valid case in which LAR's output doesn't quite agree with set_thread_area()'s input. This isn't triggered in the test as is, but it will be if we start calling set_thread_area() with the accessed bit clear. Work around this discrepency. I've added a Fixes tag so that -stable can pick this up if neccesary. Fixes: 5b781c7e317f ("x86/tls: Forcibly set the accessed bit in TLS segments") Signed-off-by: Andy Lutomirski --- tools/testing/selftests/x86/ldt_gdt.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/x86/ldt_gdt.c b/tools/testing/selftests/x86/ldt_gdt.c index b9a22f18566a..b2c54f4673f2 100644 --- a/tools/testing/selftests/x86/ldt_gdt.c +++ b/tools/testing/selftests/x86/ldt_gdt.c @@ -114,7 +114,15 @@ static void check_valid_segment(uint16_t index, int ldt, return; } - if (ar != expected_ar) { + /* The SDM says "bits 19:16 are undefined". Thanks. */ + ar &= ~0xF0000; + + /* + * NB: Different Linux versions do different things with the + * accessed bit in set_thread_area(). + */ + if (ar != expected_ar && + (ldt || ar != (expected_ar | AR_ACCESSED))) { printf("[FAIL]\t%s entry %hu has AR 0x%08X but expected 0x%08X\n", (ldt ? "LDT" : "GDT"), index, ar, expected_ar); nerrs++; -- 2.13.6