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 8BAFFC43215 for ; Sat, 16 Nov 2019 15:43:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 60C2D2073B for ; Sat, 16 Nov 2019 15:43:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573919035; bh=zWF5U4xg7nt3/h5P3T6bRnH5eZb0im/xahs52GP8njM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=RM018kVKc90FiMz5Nc4TZqUrjmC2MXcpTEuvBS1Skk7z/2SMaLh9onjFCx3rbT6Nd iy5e2LGOYEY7N7Ccxx04eRmUns6xt/I8dO6SEBuyZY7vEM28TPmMsv8PAOb8s/d8Y9 6GO8rew1gNGny5SoutyujIJactJckkT3XI/XVCQk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728898AbfKPPny (ORCPT ); Sat, 16 Nov 2019 10:43:54 -0500 Received: from mail.kernel.org ([198.145.29.99]:48106 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727870AbfKPPnt (ORCPT ); Sat, 16 Nov 2019 10:43:49 -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 A843A20729; Sat, 16 Nov 2019 15:43:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573919028; bh=zWF5U4xg7nt3/h5P3T6bRnH5eZb0im/xahs52GP8njM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fhvBtnvFY4od+uheu6kih3XaR6W7n/Go86Vsz12TR2GNvABTY9gldAsbPimX4yH/X VSmdA2afmJ2D15IxbPhL/kxpOCwOHxVwNlyut0+RnekLlzXSY3gG4gqjDcrN2B2lbO jnV/Y+XtUJKQU9xdP42t5d6uKfl/D/ifORnzuhtY= 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 4.19 126/237] powerpc/process: Fix flush_all_to_thread for SPE Date: Sat, 16 Nov 2019 10:39:21 -0500 Message-Id: <20191116154113.7417-126-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191116154113.7417-1-sashal@kernel.org> References: <20191116154113.7417-1-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 909c9407e392a..02b69a68139cc 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -575,12 +575,11 @@ 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