From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753220AbdKVXBy (ORCPT ); Wed, 22 Nov 2017 18:01:54 -0500 Received: from fldsmtpe03.verizon.com ([140.108.26.142]:24552 "EHLO fldsmtpe03.verizon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752655AbdKVW0Y (ORCPT ); Wed, 22 Nov 2017 17:26:24 -0500 From: alexander.levin@verizon.com Cc: Andy Lutomirski , Borislav Petkov , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , alexander.levin@verizon.com X-Host: surveyor.tdc.vzwcorp.com To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" Subject: [PATCH AUTOSEL for 4.14 06/51] selftests/x86/ldt_gdt: Robustify against set_thread_area() and LAR oddities Thread-Topic: [PATCH AUTOSEL for 4.14 06/51] selftests/x86/ldt_gdt: Robustify against set_thread_area() and LAR oddities Thread-Index: AQHTY+DSW5MtLBftzUqO1fp9gKScgA== Date: Wed, 22 Nov 2017 22:25:37 +0000 Message-ID: <20171122222526.20021-6-alexander.levin@verizon.com> References: <20171122222526.20021-1-alexander.levin@verizon.com> In-Reply-To: <20171122222526.20021-1-alexander.levin@verizon.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-messagesentrepresentingtype: 1 x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.144.60.250] Content-Type: text/plain; charset="iso-8859-1" MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id vAMN25NS032495 From: Andy Lutomirski [ Upstream commit d60ad744c9741586010d4bea286f09a063a90fbd ] 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. Signed-off-by: Andy Lutomirski Cc: Borislav Petkov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: 5b781c7e317f ("x86/tls: Forcibly set the accessed bit in TLS segments") Link: http://lkml.kernel.org/r/b82f3f89c034b53580970ac865139fd8863f44e2.1509794321.git.luto@kernel.org Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin --- 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 b1779da72428..2afc41a3730f 100644 --- a/tools/testing/selftests/x86/ldt_gdt.c +++ b/tools/testing/selftests/x86/ldt_gdt.c @@ -115,7 +115,15 @@ 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++; -- 2.11.0