Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 522C3C38142 for ; Tue, 24 Jan 2023 06:41:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232947AbjAXGle (ORCPT ); Tue, 24 Jan 2023 01:41:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57668 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231703AbjAXGlb (ORCPT ); Tue, 24 Jan 2023 01:41:31 -0500 Received: from gnuweeb.org (gnuweeb.org [51.81.211.47]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D2F1416ADA; Mon, 23 Jan 2023 22:41:30 -0800 (PST) Received: from biznet-home.integral.gnuweeb.org (unknown [182.253.88.152]) by gnuweeb.org (Postfix) with ESMTPSA id 4EDF082EF1; Tue, 24 Jan 2023 06:41:24 +0000 (UTC) X-GW-Data: lPqxHiMPbJw1wb7CM9QUryAGzr0yq5atzVDdxTR0iA== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gnuweeb.org; s=default; t=1674542490; bh=FQnxWh95uCNGyT0gTIyVUSAFILOzF/Wnxr5sBHSX71E=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=gnB2UTWr1Qlq6HPz7vX6i0ynWcgIAr0LoxBViAnZhAzqWDPlLgaybkPzl64GDr5E7 QqGj37b6c9ffXumlYMjMGxgxk1U5Q9LBfmWd6Z7izSrCf3vw4RVRoTQFSys1kJzKT0 0HpRFsrQb/jVQ5qRrrfCCzQPG3aAqln0TJKspK11Y/aKlYMfMtt6t7vgDzuLU1AztF ihMZRCy9mz9JLG1prV2QWAGtvlj5KSRsQqWdguz72ZhuukuyKq552qowfY9n9wk1LN x3Mkheq7AT4Ye3UwIpU8nkCSRB6p+KN9vuVQTI6BqehrTNGaDP73j4wRaS4uxqcVw2 9t+k7F0TmH4Eg== Date: Tue, 24 Jan 2023 13:41:20 +0700 From: Ammar Faizi To: "H. Peter Anvin" Cc: x86 Mailing List , Dave Hansen , Dave Hansen , Xin Li , Thomas Gleixner , Andrew Cooper , Brian Gerst , Ingo Molnar , Borislav Petkov , Peter Zijlstra , Shuah Khan , Ingo Molnar , Andy Lutomirski , "Kirill A. Shutemov" , Linux Kselftest Mailing List , Linux Kernel Mailing List Subject: Re: [RFC PATCH v2 2/2] selftests/x86: sysret_rip: Add more syscall tests with respect to `%rcx` and `%r11` Message-ID: References: <18B5DB6D-AEBD-4A67-A7B3-CE64940819B7@zytor.com> <25b96960-a07e-a952-5c23-786b55054126@zytor.com> <6cd0db14-c9e2-3598-fd10-4b473d78c373@citrix.com> <5ecc383c-621b-57d9-7f6d-d63496fca3b3@zytor.com> <20230124022729.596997-1-ammarfaizi2@gnuweeb.org> <20230124022729.596997-3-ammarfaizi2@gnuweeb.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 23, 2023 at 10:16:01PM -0800, H. Peter Anvin wrote: > On 1/23/23 18:27, Ammar Faizi wrote: > > Test that: > > > > - "syscall" in a FRED system doesn't clobber %rcx and %r11. > > - "syscall" in a non-FRED system sets %rcx=%rip and %r11=%rflags. > > > > Test them out with a trivial system call like __NR_getppid and friends > > which are extremely likely to return with SYSRET on an IDT system; check > > that it returns a nonnegative value and then save the result. > > > > "Nonnegative" here should be "valid"; it is an implementation detail that > the error value is -1. Copy-paste error, will fix that! > However, you are not checking that you don't get a mix of REGS_SAVED and > REGS_SYSRET, which is a major part of the point. Good point! What do you think of adding this on top of patch #1? diff --git a/tools/testing/selftests/x86/sysret_rip.c b/tools/testing/selftests/x86/sysret_rip.c index 75c72d34dbc5840c..3da827713831acbc 100644 --- a/tools/testing/selftests/x86/sysret_rip.c +++ b/tools/testing/selftests/x86/sysret_rip.c @@ -47,11 +47,14 @@ static const unsigned long rcx_sentinel = 0x5ca1ab1e0b57ac1e; static const unsigned long rflags_sentinel = 0x200a93; enum regs_ok { - REGS_ERROR = -1, /* Invalid register contents */ - REGS_SAVED = 0, /* Registers properly preserved */ - REGS_SYSRET = 1 /* Registers match syscall/sysret */ + REGS_INIT_VAL = -2, /* For init value checker, never returned */ + REGS_ERROR = -1, /* Invalid register contents */ + REGS_SAVED = 0, /* Registers properly preserved */ + REGS_SYSRET = 1 /* Registers match syscall/sysret */ }; +static enum regs_ok regs_ok_state = REGS_INIT_VAL; + /* * Returns: * 0 = %rcx and %r11 preserved. @@ -86,6 +89,7 @@ static long do_syscall(long nr_syscall, unsigned long arg1, unsigned long arg2, register unsigned long r9 asm("%r9"); register void *rsp asm("%rsp"); unsigned long rcx, rbx; + enum regs_ok ret; r11 = r11_sentinel; rcx = rcx_sentinel; @@ -124,7 +128,14 @@ static long do_syscall(long nr_syscall, unsigned long arg1, unsigned long arg2, * - "syscall" in a non-FRED system sets %rcx=%rip and %r11=%rflags. * */ - assert(check_regs_result(r11, rcx, rbx) != REGS_ERROR); + ret = check_regs_result(r11, rcx, rbx); + assert(ret != REGS_ERROR); + + if (regs_ok_state == REGS_INIT_VAL) + regs_ok_state = ret; + else + assert(ret == regs_ok_state); + return nr_syscall; } -- Ammar Faizi