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=-19.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 00696C07E95 for ; Sat, 10 Jul 2021 23:53:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D8C4B610A2 for ; Sat, 10 Jul 2021 23:53:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233758AbhGJX4k (ORCPT ); Sat, 10 Jul 2021 19:56:40 -0400 Received: from mail.kernel.org ([198.145.29.99]:41376 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233767AbhGJXzn (ORCPT ); Sat, 10 Jul 2021 19:55:43 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8181F613F5; Sat, 10 Jul 2021 23:51:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1625961117; bh=Qov3NdALQaJngH7UvnuSSQKyNioJNZNNRlHpZDfJudE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=m8VXFjcfr1W05zFZ3dPvSkHUyc/i9EiN90WKL7q5gD2Jqta9m5bAVFH3WfA8tp1E7 iixKE9ScwEi3Qqqy6QH97/LG2Ckd6pllvdmIeECloVFib0g9NMwV3IukE74E0p46L4 I+w9oFEsXgg6Jc7MsZesLcC3DDYBlKweMVIQFTNqQgZ/+6dtgWfIX6J9k0OxANhqyd QU9tKLGc6m/IqIErFwxpisLDbm9Nd2X0iDBNCMSWqGpyKDX5UmjbBG6VLYUFXHgXiD 0PpB4QdIKAMSmY6rTcld3jaF6ZRByYZnXTTmX1vnsKaV6xTD5sH6H6ItIlzUR4BArd 6WTFszPFmGjMQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Thomas Gleixner , Borislav Petkov , Sasha Levin Subject: [PATCH AUTOSEL 4.19 10/22] x86/fpu: Return proper error codes from user access functions Date: Sat, 10 Jul 2021 19:51:31 -0400 Message-Id: <20210710235143.3222129-10-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210710235143.3222129-1-sashal@kernel.org> References: <20210710235143.3222129-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@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 fa2c93cb42a2..b8c935033d21 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; \ }) @@ -221,16 +222,20 @@ static inline void copy_fxregs_to_kernel(struct fpu *fpu) #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