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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 49915C433E1 for ; Thu, 28 May 2020 20:16:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2A1B8207D3 for ; Thu, 28 May 2020 20:16:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590696975; bh=mlq9mjd9i3OvLkIbEfKiuimRPI+OO5yjsoj+PUunLx8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=rTc7ryTgQ4+4rsIs2mk6fUCYqPcMdfOCYnZmw7FfRGj3I2QZXefE7Yu/Y1ZVJbMSL a2BZm4o6osfRaF/7vQd0EyEHPRrmmGnGWh/IoHG5NC/PAY1lrsFWu93qBK2Y2EtQD6 zihT6VW+Fnp7Z6Wsrki/d6X8sXD0GLndcXHrN5QU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2407188AbgE1UQO (ORCPT ); Thu, 28 May 2020 16:16:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:42336 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2407054AbgE1UOm (ORCPT ); Thu, 28 May 2020 16:14:42 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2E00921508; Thu, 28 May 2020 20:14:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590696881; bh=mlq9mjd9i3OvLkIbEfKiuimRPI+OO5yjsoj+PUunLx8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wrXPba83pJySxfbiDQeF+GuTvltVY4Sw/vu76ACO4otbqNYUDlBmpwx0naWiiEtZ2 tp1qaCow5XueglVssIqY+3NxougoIaFCXn341IvDTcNxR1dgc+9fL1ACOS3Aj3ybgo 2J9CsiyEIwVct0nSVtqz3TPXIPEsnP7aH1eGASxA= From: Sasha Levin To: tglx@linutronix.de, luto@kernel.org, ak@linux.intel.com Cc: corbet@lwn.net, mingo@redhat.com, bp@alien8.de, x86@kernel.org, shuah@kernel.org, gregkh@linuxfoundation.org, tony.luck@intel.com, chang.seok.bae@intel.com, dave.hansen@linux.intel.com, peterz@infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, jarkko.sakkinen@linux.intel.com, "H . Peter Anvin" , Dave Hansen , Sasha Levin Subject: [PATCH v13 15/16] selftests/x86/fsgsbase: Test GS selector on ptracer-induced GS base write Date: Thu, 28 May 2020 16:14:01 -0400 Message-Id: <20200528201402.1708239-16-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200528201402.1708239-1-sashal@kernel.org> References: <20200528201402.1708239-1-sashal@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Chang S. Bae" The test validates that the selector is not changed when a ptracer writes the ptracee's GS base. Originally-by: Andy Lutomirski Signed-off-by: Chang S. Bae Reviewed-by: Tony Luck Cc: Thomas Gleixner Cc: Borislav Petkov Cc: Andy Lutomirski Cc: H. Peter Anvin Cc: Dave Hansen Cc: Tony Luck Cc: Andi Kleen Signed-off-by: Sasha Levin --- tools/testing/selftests/x86/fsgsbase.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) diff --git a/tools/testing/selftests/x86/fsgsbase.c b/tools/testing/selftests/x86/fsgsbase.c index 15a329da59fa..950a48b2e366 100644 --- a/tools/testing/selftests/x86/fsgsbase.c +++ b/tools/testing/selftests/x86/fsgsbase.c @@ -465,7 +465,7 @@ static void test_ptrace_write_gsbase(void) wait(&status); if (WSTOPSIG(status) == SIGTRAP) { - unsigned long gs, base; + unsigned long gs; unsigned long gs_offset = USER_REGS_OFFSET(gs); unsigned long base_offset = USER_REGS_OFFSET(gs_base); @@ -481,7 +481,6 @@ static void test_ptrace_write_gsbase(void) err(1, "PTRACE_POKEUSER"); gs = ptrace(PTRACE_PEEKUSER, child, gs_offset, NULL); - base = ptrace(PTRACE_PEEKUSER, child, base_offset, NULL); /* * In a non-FSGSBASE system, the nonzero selector will load @@ -489,11 +488,21 @@ static void test_ptrace_write_gsbase(void) * selector value is changed or not by the GSBASE write in * a ptracer. */ - if (gs == 0 && base == 0xFF) { - printf("[OK]\tGS was reset as expected\n"); - } else { + if (gs != *shared_scratch) { nerrs++; - printf("[FAIL]\tGS=0x%lx, GSBASE=0x%lx (should be 0, 0xFF)\n", gs, base); + printf("[FAIL]\tGS changed to %lx\n", gs); + + /* + * On older kernels, poking a nonzero value into the + * base would zero the selector. On newer kernels, + * this behavior has changed -- poking the base + * changes only the base and, if FSGSBASE is not + * available, this may not effect. + */ + if (gs == 0) + printf("\tNote: this is expected behavior on older kernels.\n"); + } else { + printf("[OK]\tGS remained 0x%hx\n", *shared_scratch); } } -- 2.25.1