From patchwork Wed Jan 9 11:47:38 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 10753917 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D4B9313BF for ; Wed, 9 Jan 2019 11:49:29 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C249528DF8 for ; Wed, 9 Jan 2019 11:49:29 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B6A2328E0C; Wed, 9 Jan 2019 11:49:29 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 38B7828DF8 for ; Wed, 9 Jan 2019 11:49:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731104AbfAILss (ORCPT ); Wed, 9 Jan 2019 06:48:48 -0500 Received: from Galois.linutronix.de ([146.0.238.70]:56225 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731079AbfAILsq (ORCPT ); Wed, 9 Jan 2019 06:48:46 -0500 Received: from localhost ([127.0.0.1] helo=bazinga.breakpoint.cc) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1ghCLg-0007Al-9q; Wed, 09 Jan 2019 12:48:40 +0100 From: Sebastian Andrzej Siewior To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, Andy Lutomirski , Paolo Bonzini , =?utf-8?b?UmFkaW0gS3LEjW3DocWZ?= , kvm@vger.kernel.org, "Jason A. Donenfeld" , Rik van Riel , Dave Hansen , Sebastian Andrzej Siewior Subject: [PATCH 16/22] x86/fpu: Always store the registers in copy_fpstate_to_sigframe() Date: Wed, 9 Jan 2019 12:47:38 +0100 Message-Id: <20190109114744.10936-17-bigeasy@linutronix.de> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190109114744.10936-1-bigeasy@linutronix.de> References: <20190109114744.10936-1-bigeasy@linutronix.de> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Rik van Riel copy_fpstate_to_sigframe() stores the registers directly to user space. This is okay because the FPU register are valid and saving it directly avoids saving it into kernel memory and making a copy. However… We can't keep doing this if we are going to restore the FPU registers on the return to userland. It is possible that the FPU registers will be invalidated in the middle of the save operation and this should be done with disabled preemption / BH. Save the FPU registers to task's FPU struct and copy them to the user memory later on. This code is extracted from an earlier version of the patchset while there still was lazy-FPU on x86. Signed-off-by: Rik van Riel Signed-off-by: Sebastian Andrzej Siewior --- arch/x86/include/asm/fpu/internal.h | 45 ----------------------------- arch/x86/kernel/fpu/signal.c | 29 +++++++------------ 2 files changed, 10 insertions(+), 64 deletions(-) diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index 7191eb9686827..16ea30235b025 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -126,22 +126,6 @@ extern void fpstate_sanitize_xstate(struct fpu *fpu); _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_fprestore) \ : output : input) -static inline int copy_fregs_to_user(struct fregs_state __user *fx) -{ - return user_insn(fnsave %[fx]; fwait, [fx] "=m" (*fx), "m" (*fx)); -} - -static inline int copy_fxregs_to_user(struct fxregs_state __user *fx) -{ - if (IS_ENABLED(CONFIG_X86_32)) - return user_insn(fxsave %[fx], [fx] "=m" (*fx), "m" (*fx)); - else if (IS_ENABLED(CONFIG_AS_FXSAVEQ)) - return user_insn(fxsaveq %[fx], [fx] "=m" (*fx), "m" (*fx)); - - /* See comment in copy_fxregs_to_kernel() below. */ - return user_insn(rex64/fxsave (%[fx]), "=m" (*fx), [fx] "R" (fx)); -} - static inline void copy_kernel_to_fxregs(struct fxregs_state *fx) { if (IS_ENABLED(CONFIG_X86_32)) { @@ -352,35 +336,6 @@ static inline void copy_kernel_to_xregs(struct xregs_state *xstate, u64 mask) XSTATE_XRESTORE(xstate, lmask, hmask); } -/* - * Save xstate to user space xsave area. - * - * We don't use modified optimization because xrstor/xrstors might track - * a different application. - * - * We don't use compacted format xsave area for - * backward compatibility for old applications which don't understand - * compacted format of xsave area. - */ -static inline int copy_xregs_to_user(struct xregs_state __user *buf) -{ - int err; - - /* - * Clear the xsave header first, so that reserved fields are - * initialized to zero. - */ - err = __clear_user(&buf->header, sizeof(buf->header)); - if (unlikely(err)) - return -EFAULT; - - stac(); - XSTATE_OP(XSAVE, buf, -1, -1, err); - clac(); - - return err; -} - /* * Restore xstate from user space xsave area. */ diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c index 555c469878874..bf4e6caad305e 100644 --- a/arch/x86/kernel/fpu/signal.c +++ b/arch/x86/kernel/fpu/signal.c @@ -118,22 +118,6 @@ static inline int save_xstate_epilog(void __user *buf, int ia32_frame) return err; } -static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf) -{ - int err; - - if (use_xsave()) - err = copy_xregs_to_user(buf); - else if (use_fxsr()) - err = copy_fxregs_to_user((struct fxregs_state __user *) buf); - else - err = copy_fregs_to_user((struct fregs_state __user *) buf); - - if (unlikely(err) && __clear_user(buf, fpu_user_xstate_size)) - err = -EFAULT; - return err; -} - /* * Save the fpu, extended register state to the user signal frame. * @@ -157,6 +141,7 @@ static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf) int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size) { struct fpu *fpu = ¤t->thread.fpu; + struct xregs_state *xsave = &fpu->state.xsave; struct task_struct *tsk = current; int ia32_fxstate = (buf != buf_fx); @@ -171,9 +156,15 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size) sizeof(struct user_i387_ia32_struct), NULL, (struct _fpstate_32 __user *) buf) ? -1 : 1; - /* Save the live register state to the user directly. */ - if (copy_fpregs_to_sigframe(buf_fx)) - return -1; + copy_fpregs_to_fpstate(fpu); + + if (using_compacted_format()) { + copy_xstate_to_user(buf_fx, xsave, 0, size); + } else { + fpstate_sanitize_xstate(fpu); + if (__copy_to_user(buf_fx, xsave, fpu_user_xstate_size)) + return -1; + } /* Save the fsave header for the 32-bit frames. */ if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))