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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A99D0C3ABC0 for ; Thu, 8 May 2025 13:37:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=TAJOfxqME/wGtmL0ltejd33aSpgxllbYRKYEu+7OKXA=; b=SyKUnBQKEnJj+XuSI1OMq2q56i Jg01D4b6RH+W6L9LKRE/OSWGU9l/z/4YWDlpZ93wn47yEkro0Hnt77SjDpX/5A5ZRqKR14sTTYx88 F44yTu/eMLJskDW0b+9r0vR43VJUgLD1mj1AnvqSsSiiL9we5ZEO8L2+UUWq1AOE6SzXL1to/Gq9Z HzIhzlj+T9AMy2oZGMsgB6EXTCcpwJ1R/lW7Fix9AasYVV12vWH5vrbij1n1HDNrYFqaFC6uaXtDI 4dn/pNQOYEkHOQDv6h2lLt6pbHo2lBvtN+IZRgiEGYEi+q7JOjTbk+IW+lhgLKMTnLqCWQ2T6/r5A OvjjxQlw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uD1RF-00000000m25-1Lkn; Thu, 08 May 2025 13:37:25 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uD1Ha-00000000kN4-0KfL for linux-arm-kernel@lists.infradead.org; Thu, 08 May 2025 13:27:27 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4EDE7106F; Thu, 8 May 2025 06:27:15 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 4E3CF3F58B; Thu, 8 May 2025 06:27:23 -0700 (PDT) From: Mark Rutland To: linux-arm-kernel@lists.infradead.org Cc: broonie@kernel.org, catalin.marinas@arm.com, daniel.kiss@arm.com, david.spickett@arm.com, luis.machado@arm.com, mark.rutland@arm.com, maz@kernel.org, richard.sandiford@arm.com, sander.desmalen@arm.com, tabba@google.com, tamas.petz@arm.com, tkjos@google.com, will@kernel.org, yury.khrustalev@arm.com Subject: [PATCH v2 04/24] arm64/fpsimd: signal: Consistently read FPSIMD context Date: Thu, 8 May 2025 14:26:24 +0100 Message-Id: <20250508132644.1395904-5-mark.rutland@arm.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20250508132644.1395904-1-mark.rutland@arm.com> References: <20250508132644.1395904-1-mark.rutland@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250508_062726_200263_5FF562D0 X-CRM114-Status: GOOD ( 17.80 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org For historical reasons, restore_sve_fpsimd_context() has an open-coded copy of the logic from read_fpsimd_context(), which is used to either restore an FPSIMD-only context, or to merge FPSIMD state into an SVE state when restoring an SVE+FPSIMD context. The logic is *almost* identical. Refactor the logic to avoid duplication and make this clearer. This comes with two functional changes that I do not believe will be problematic in practice: * The user_fpsimd_state::size field will be checked in all restore paths that consume it user_fpsimd_state. The kernel always populates this field when delivering a signal, and so this should contain the expected value unless it has been corrupted. * If a read of user_fpsimd_state fails, we will return early without modifying TIF_SVE, the saved SVCR, or the save fp_type. This will leave the task in a consistent state, without potentially resurrecting stale FPSIMD state. A read of user_fpsimd_state should never fail unless the structure has been corrupted or the stack has been unmapped. Suggested-by: Will Deacon Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: Marc Zyngier Cc: Mark Brown Cc: Will Deacon --- arch/arm64/kernel/signal.c | 57 +++++++++++++++++++------------------- 1 file changed, 29 insertions(+), 28 deletions(-) diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c index e898948a31b65..87890d7be8de3 100644 --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c @@ -264,30 +264,40 @@ static int preserve_fpsimd_context(struct fpsimd_context __user *ctx) return err ? -EFAULT : 0; } -static int restore_fpsimd_context(struct user_ctxs *user) +static int read_fpsimd_context(struct user_fpsimd_state *fpsimd, + struct user_ctxs *user) { - struct user_fpsimd_state fpsimd; - int err = 0; + int err; /* check the size information */ if (user->fpsimd_size != sizeof(struct fpsimd_context)) return -EINVAL; /* copy the FP and status/control registers */ - err = __copy_from_user(fpsimd.vregs, &(user->fpsimd->vregs), - sizeof(fpsimd.vregs)); - __get_user_error(fpsimd.fpsr, &(user->fpsimd->fpsr), err); - __get_user_error(fpsimd.fpcr, &(user->fpsimd->fpcr), err); + err = __copy_from_user(fpsimd->vregs, &(user->fpsimd->vregs), + sizeof(fpsimd->vregs)); + __get_user_error(fpsimd->fpsr, &(user->fpsimd->fpsr), err); + __get_user_error(fpsimd->fpcr, &(user->fpsimd->fpcr), err); + + return err; +} + +static int restore_fpsimd_context(struct user_ctxs *user) +{ + struct user_fpsimd_state fpsimd; + int err; + + err = read_fpsimd_context(&fpsimd, user); + if (err) + return err; clear_thread_flag(TIF_SVE); current->thread.svcr &= ~SVCR_SM_MASK; current->thread.fp_type = FP_STATE_FPSIMD; /* load the hardware registers from the fpsimd_state structure */ - if (!err) - fpsimd_update_current_state(&fpsimd); - - return err ? -EFAULT : 0; + fpsimd_update_current_state(&fpsimd); + return 0; } static int preserve_fpmr_context(struct fpmr_context __user *ctx) @@ -427,12 +437,8 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user) * consistency and robustness, reject restoring streaming SVE state * without an SVE payload. */ - if (!sm && user->sve_size == sizeof(*user->sve)) { - clear_thread_flag(TIF_SVE); - current->thread.svcr &= ~SVCR_SM_MASK; - current->thread.fp_type = FP_STATE_FPSIMD; - goto fpsimd_only; - } + if (!sm && user->sve_size == sizeof(*user->sve)) + return restore_fpsimd_context(user); vq = sve_vq_from_vl(vl); @@ -458,19 +464,14 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user) set_thread_flag(TIF_SVE); current->thread.fp_type = FP_STATE_SVE; -fpsimd_only: - /* copy the FP and status/control registers */ - /* restore_sigframe() already checked that user->fpsimd != NULL. */ - err = __copy_from_user(fpsimd.vregs, user->fpsimd->vregs, - sizeof(fpsimd.vregs)); - __get_user_error(fpsimd.fpsr, &user->fpsimd->fpsr, err); - __get_user_error(fpsimd.fpcr, &user->fpsimd->fpcr, err); + err = read_fpsimd_context(&fpsimd, user); + if (err) + return -EFAULT; - /* load the hardware registers from the fpsimd_state structure */ - if (!err) - fpsimd_update_current_state(&fpsimd); + /* Merge the FPSIMD registers into the SVE state */ + fpsimd_update_current_state(&fpsimd); - return err ? -EFAULT : 0; + return 0; } #else /* ! CONFIG_ARM64_SVE */ -- 2.30.2