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=-20.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 A3412C07E95 for ; Mon, 19 Jul 2021 17:12:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7B1BE6023F for ; Mon, 19 Jul 2021 17:12:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351225AbhGSQcP (ORCPT ); Mon, 19 Jul 2021 12:32:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:57794 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345844AbhGSPQx (ORCPT ); Mon, 19 Jul 2021 11:16:53 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 96567610D0; Mon, 19 Jul 2021 15:57:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626710226; bh=iM1K6mqKlaFRjb/3+kOuMfyvud8VMFcfwJgch6Mi2cM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=K4R9VUy+aKkzQ6t18d48clRjSxiE2DG3ixomS+cZLEUdDsCXObPG3+IJ7MjfTsNEt i83hkSfsjPEDz3mv2kRDHRvD/qQr8koMqL5Lzs5OexGI7/nfo4n/yVIFO1XMdhRUjZ 2V6DjMGFPx4PxhdUy6RNWbdD51Gr3NGb26JNbr8Q= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Thomas Gleixner , Borislav Petkov , Sasha Levin Subject: [PATCH 5.10 128/243] x86/fpu: Return proper error codes from user access functions Date: Mon, 19 Jul 2021 16:52:37 +0200 Message-Id: <20210719144945.042322427@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210719144940.904087935@linuxfoundation.org> References: <20210719144940.904087935@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Thomas Gleixner [ Upstream commit aee8c67a4faa40a8df4e79316dbfc92d123989c1 ] When *RSTOR from user memory raises an exception, there is no way to differentiate them. That's bad because it forces the slow path even when the failure was not a fault. If the operation raised eg. #GP then going through the slow path is pointless. Use _ASM_EXTABLE_FAULT() which stores the trap number and let the exception fixup return the negated trap number as error. This allows to separate the fast path and let it handle faults directly and avoid the slow path for all other exceptions. Signed-off-by: Thomas Gleixner Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/20210623121457.601480369@linutronix.de Signed-off-by: Sasha Levin --- arch/x86/include/asm/fpu/internal.h | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index 16bf4d4a8159..4e5af2b00d89 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -103,6 +103,7 @@ static inline void fpstate_init_fxstate(struct fxregs_state *fx) } extern void fpstate_sanitize_xstate(struct fpu *fpu); +/* Returns 0 or the negated trap number, which results in -EFAULT for #PF */ #define user_insn(insn, output, input...) \ ({ \ int err; \ @@ -110,14 +111,14 @@ extern void fpstate_sanitize_xstate(struct fpu *fpu); might_fault(); \ \ asm volatile(ASM_STAC "\n" \ - "1:" #insn "\n\t" \ + "1: " #insn "\n" \ "2: " ASM_CLAC "\n" \ ".section .fixup,\"ax\"\n" \ - "3: movl $-1,%[err]\n" \ + "3: negl %%eax\n" \ " jmp 2b\n" \ ".previous\n" \ - _ASM_EXTABLE(1b, 3b) \ - : [err] "=r" (err), output \ + _ASM_EXTABLE_FAULT(1b, 3b) \ + : [err] "=a" (err), output \ : "0"(0), input); \ err; \ }) @@ -219,16 +220,20 @@ static inline void fxsave(struct fxregs_state *fx) #define XRSTOR ".byte " REX_PREFIX "0x0f,0xae,0x2f" #define XRSTORS ".byte " REX_PREFIX "0x0f,0xc7,0x1f" +/* + * After this @err contains 0 on success or the negated trap number when + * the operation raises an exception. For faults this results in -EFAULT. + */ #define XSTATE_OP(op, st, lmask, hmask, err) \ asm volatile("1:" op "\n\t" \ "xor %[err], %[err]\n" \ "2:\n\t" \ ".pushsection .fixup,\"ax\"\n\t" \ - "3: movl $-2,%[err]\n\t" \ + "3: negl %%eax\n\t" \ "jmp 2b\n\t" \ ".popsection\n\t" \ - _ASM_EXTABLE(1b, 3b) \ - : [err] "=r" (err) \ + _ASM_EXTABLE_FAULT(1b, 3b) \ + : [err] "=a" (err) \ : "D" (st), "m" (*st), "a" (lmask), "d" (hmask) \ : "memory") -- 2.30.2