From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ED46BC10F11 for ; Wed, 24 Apr 2019 16:40:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BF650218B0 for ; Wed, 24 Apr 2019 16:40:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732700AbfDXQkm (ORCPT ); Wed, 24 Apr 2019 12:40:42 -0400 Received: from foss.arm.com ([217.140.101.70]:48670 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731234AbfDXQkk (ORCPT ); Wed, 24 Apr 2019 12:40:40 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id F2D55374; Wed, 24 Apr 2019 09:40:39 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A7E0C3F557; Wed, 24 Apr 2019 09:40:35 -0700 (PDT) Date: Wed, 24 Apr 2019 17:40:33 +0100 From: Mark Rutland To: Mathieu Desnoyers Cc: Peter Zijlstra , "Paul E . McKenney" , Boqun Feng , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Thomas Gleixner , Andy Lutomirski , Dave Watson , Paul Turner , Andrew Morton , Russell King , Ingo Molnar , "H . Peter Anvin" , Andi Kleen , Chris Lameter , Ben Maurer , Steven Rostedt , Josh Triplett , Linus Torvalds , Catalin Marinas , Will Deacon , Michael Kerrisk , Joel Fernandes , Shuah Khan , linux-kselftest@vger.kernel.org Subject: Re: [RFC PATCH for 5.2 08/10] rseq/selftests: aarch64 code signature: handle big-endian environment Message-ID: <20190424164032.GD21101@lakrids.cambridge.arm.com> References: <20190424152502.14246-1-mathieu.desnoyers@efficios.com> <20190424152502.14246-9-mathieu.desnoyers@efficios.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190424152502.14246-9-mathieu.desnoyers@efficios.com> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 24, 2019 at 11:25:00AM -0400, Mathieu Desnoyers wrote: > Handle compiling with -mbig-endian on aarch64, which generates binaries > with mixed code vs data endianness (little endian code, big endian > data). > > Else mismatch between code endianness for the generated signatures and > data endianness for the RSEQ_SIG parameter passed to the rseq > registration will trigger application segmentation faults when the > kernel try to abort rseq critical sections. > > Signed-off-by: Mathieu Desnoyers > CC: Peter Zijlstra > CC: Thomas Gleixner > CC: Joel Fernandes > CC: Catalin Marinas > CC: Dave Watson > CC: Will Deacon > CC: Shuah Khan > CC: Andi Kleen > CC: linux-kselftest@vger.kernel.org > CC: "H . Peter Anvin" > CC: Chris Lameter > CC: Russell King > CC: Michael Kerrisk > CC: "Paul E . McKenney" > CC: Paul Turner > CC: Boqun Feng > CC: Josh Triplett > CC: Steven Rostedt > CC: Ben Maurer > CC: linux-api@vger.kernel.org > CC: Andy Lutomirski > CC: Andrew Morton > CC: Linus Torvalds > --- > tools/testing/selftests/rseq/rseq-arm64.h | 17 +++++++++++++++-- > 1 file changed, 15 insertions(+), 2 deletions(-) > > diff --git a/tools/testing/selftests/rseq/rseq-arm64.h b/tools/testing/selftests/rseq/rseq-arm64.h > index b41a2a48e965..200dae9e4208 100644 > --- a/tools/testing/selftests/rseq/rseq-arm64.h > +++ b/tools/testing/selftests/rseq/rseq-arm64.h > @@ -6,7 +6,20 @@ > * (C) Copyright 2018 - Will Deacon > */ > > -#define RSEQ_SIG 0xd428bc00 /* BRK #0x45E0 */ > +/* > + * aarch64 -mbig-endian generates mixed endianness code vs data: > + * little-endian code and big-endian data. Ensure the RSEQ_SIG signature > + * matches code endianness. > + */ > +#define RSEQ_SIG_CODE 0xd428bc00 /* BRK #0x45E0. */ > + > +#ifdef __AARCH64EB__ > +#define RSEQ_SIG_DATA 0x00bc28d4 /* BRK #0x45E0. */ > +#else > +#define RSEQ_SIG_DATA RSEQ_SIG_CODE > +#endif > + > +#define RSEQ_SIG RSEQ_SIG_DATA > > #define rseq_smp_mb() __asm__ __volatile__ ("dmb ish" ::: "memory") > #define rseq_smp_rmb() __asm__ __volatile__ ("dmb ishld" ::: "memory") > @@ -121,7 +134,7 @@ do { \ > > #define RSEQ_ASM_DEFINE_ABORT(label, abort_label) \ > " b 222f\n" \ > - " .inst " __rseq_str(RSEQ_SIG) "\n" \ > + " .inst " __rseq_str(RSEQ_SIG_CODE) "\n" \ I don't think this is right; the .inst directive _should_ emit the value in the instruction stream endianness (i.e. LE, regardless of the data endianness). That's certainly the case with the kernel.org crosstool GCC: [mark@lakrids:/mnt/data/tests/inst-test]% cat test.c void func(void) { asm volatile(".inst 0xd4000001"); } [mark@lakrids:/mnt/data/tests/inst-test]% usekorg 8.1.0 aarch64-linux-gcc -c test.c [mark@lakrids:/mnt/data/tests/inst-test]% usekorg 8.1.0 aarch64-linux-objdump -d test.o test.o: file format elf64-littleaarch64 Disassembly of section .text: 0000000000000000 : 0: d4000001 svc #0x0 4: d503201f nop 8: d65f03c0 ret [mark@lakrids:/mnt/data/tests/inst-test]% usekorg 8.1.0 aarch64-linux-gcc -mbig-endian -c test.c [mark@lakrids:/mnt/data/tests/inst-test]% usekorg 8.1.0 aarch64-linux-objdump -d test.o test.o: file format elf64-bigaarch64 Disassembly of section .text: 0000000000000000 : 0: d4000001 svc #0x0 4: d503201f nop 8: d65f03c0 ret Have you tested this? Is there some toolchain that doesn't get this right? Thanks, Mark.