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=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 BD21CC432C3 for ; Sat, 16 Nov 2019 16:10:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 951D121823 for ; Sat, 16 Nov 2019 16:10:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573920629; bh=MdXxU8oNnNxUNykFVPJPxOfa36YJHrJlrvzu5GMEQSU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=aBEVeM7SG6q9TjGDvmWheCfhgP/GGIIpi7IQ3s6W1ll6U+PErG4pPwXBjl/QBz7kf OUTctBrurUoM7/8qVWhpHWn8yejfjdSTQovIrsBiKlC8Xb9Oxijkt0EPmokeoFaKxQ Y5oQyAsXoil24zSp+gwui+kYkK+UlnCGLEqQv0Q8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730685AbfKPQK1 (ORCPT ); Sat, 16 Nov 2019 11:10:27 -0500 Received: from mail.kernel.org ([198.145.29.99]:56290 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730223AbfKPPs4 (ORCPT ); Sat, 16 Nov 2019 10:48:56 -0500 Received: from sasha-vm.mshome.net (unknown [50.234.116.4]) (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 6583120729; Sat, 16 Nov 2019 15:48:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573919335; bh=MdXxU8oNnNxUNykFVPJPxOfa36YJHrJlrvzu5GMEQSU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NucvSvLM16+7ngiVuF/tnsj4keI8e5+XH+IpXnmZKfFh/K0JGs07Wcr8/zH/dzeh+ zD6b+QpI/2DjnNLO5gRNZneeyvfbjw+obpVqF5Am57pp335c81SFufSebjiYD8wQQV X5FacWpuxFi4rjNYHkeXYHBzsEAcdlj/ef6j6uao= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Felipe Rechia , Michael Ellerman , Sasha Levin , linuxppc-dev@lists.ozlabs.org Subject: [PATCH AUTOSEL 4.14 076/150] powerpc/process: Fix flush_all_to_thread for SPE Date: Sat, 16 Nov 2019 10:46:14 -0500 Message-Id: <20191116154729.9573-76-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191116154729.9573-1-sashal@kernel.org> References: <20191116154729.9573-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Felipe Rechia [ Upstream commit e901378578c62202594cba0f6c076f3df365ec91 ] Fix a bug introduced by the creation of flush_all_to_thread() for processors that have SPE (Signal Processing Engine) and use it to compute floating-point operations. >>From userspace perspective, the problem was seen in attempts of computing floating-point operations which should generate exceptions. For example: fork(); float x = 0.0 / 0.0; isnan(x); // forked process returns False (should be True) The operation above also should always cause the SPEFSCR FINV bit to be set. However, the SPE floating-point exceptions were turned off after a fork(). Kernel versions prior to the bug used flush_spe_to_thread(), which first saves SPEFSCR register values in tsk->thread and then calls giveup_spe(tsk). After commit 579e633e764e, the save_all() function was called first to giveup_spe(), and then the SPEFSCR register values were saved in tsk->thread. This would save the SPEFSCR register values after disabling SPE for that thread, causing the bug described above. Fixes 579e633e764e ("powerpc: create flush_all_to_thread()") Signed-off-by: Felipe Rechia Signed-off-by: Michael Ellerman Signed-off-by: Sasha Levin --- arch/powerpc/kernel/process.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 5e5da2073fdff..ba0d4f9a99bac 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -567,12 +567,11 @@ void flush_all_to_thread(struct task_struct *tsk) if (tsk->thread.regs) { preempt_disable(); BUG_ON(tsk != current); - save_all(tsk); - #ifdef CONFIG_SPE if (tsk->thread.regs->msr & MSR_SPE) tsk->thread.spefscr = mfspr(SPRN_SPEFSCR); #endif + save_all(tsk); preempt_enable(); } -- 2.20.1