From patchwork Wed Apr 27 17:12:40 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ard Biesheuvel X-Patchwork-Id: 12829262 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 A76C2C433F5 for ; Wed, 27 Apr 2022 17:28:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=HRe9zaDs1crEh1Z0uQjCznqh2ZknurR3SEeekfqjFqs=; b=L5opjKhdrjC8Xu +DosY4K9Obab1CCHSC+nEhMPfPEZSki3WCUts7BgdaV0jrXtttVJNWFB6x4bVlfptNpO5J7fh5Ln8 s7UxqeAvZ1HnKaC3LMAJkmvw+aroN+N+cIKAztRUh4lvdZ7wpIvsGOWaW8RhQ0VunVouO+LgjmziQ FRlpp5SHK5MSgF89wZ+sQfEyoSXretH//e/q/x/pw4qx43ZI0XHj3asQPKXUEqN9NjyiNf75WFLxe 5MdI0T3H0mRz7zIK1mfeR/9ElfveUubBldvAwJy6vThQkBRXZUochANsJBe3H4WATc2et3haTeVD0 YhcIxd6HzR/4a86vIexw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1njlRZ-002epF-6M; Wed, 27 Apr 2022 17:27:13 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1njlDs-002ZFh-JY for linux-arm-kernel@lists.infradead.org; Wed, 27 Apr 2022 17:13:08 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 93BB061E18; Wed, 27 Apr 2022 17:13:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE246C385B0; Wed, 27 Apr 2022 17:13:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1651079583; bh=bQZstQBwyA5UayDt39rQFQoQ6xyTaxuR5gluVAnpbCo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mI404qdyQVYXiaRbn6/6ZPVC2ntIlSl21vTAydS/n9ncaoCJbrAi6XBF8ip35OMWJ TizpRxIsSZx0MaVroD9Ogi7Lb40W8BUC7cCdEwldLoX9TvZiDoH6pvNi3DK/++jZpO foWGK2/L6PaHVyPUMjT2tIKIwjeRVgK6ACbFjYKzk1wkgcEjLeRVp0oVv26TI7XuQ9 eRdNpvQXdy5cEmCjozQ+SU7StaHEWZbTOwjWDFw2pAZx6UhH4YN8xBwzWchaP/H69j EMxGtAKM3oO+eEA2/X3HhpylUXSizfbP3R0Fb9R0b3wB1ysmrVKnDmnexQmdlQLkLZ q/Piad9h99K6g== From: Ard Biesheuvel To: linux-arm-kernel@lists.infradead.org Cc: clang-built-linux@googlegroups.com, will@kernel.org, catalin.marinas@arm.com, keescook@chromium.org, mark.rutland@arm.com, nathan@kernel.org, Ard Biesheuvel , Sami Tolvanen , Nick Desaulniers Subject: [RFC PATCH 1/2] arm64: jump_label: use more precise asm constraints Date: Wed, 27 Apr 2022 19:12:40 +0200 Message-Id: <20220427171241.2426592-2-ardb@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220427171241.2426592-1-ardb@kernel.org> References: <20220427171241.2426592-1-ardb@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1925; h=from:subject; bh=bQZstQBwyA5UayDt39rQFQoQ6xyTaxuR5gluVAnpbCo=; b=owEB7QES/pANAwAKAcNPIjmS2Y8kAcsmYgBiaXmGCSeZrap2M2MThRtu4fDOfDoPj5aMO6bi5gQ1 eQuq2PWJAbMEAAEKAB0WIQT72WJ8QGnJQhU3VynDTyI5ktmPJAUCYml5hgAKCRDDTyI5ktmPJNofC/ 0VZ5MoKi4s9Y+GZ5c8YFJO+jHPce5blHGGtcHMZS9q+d67GFIRnul6D3Walmuh81behJNGEtGZHC7M Y7/lhDbH7uQ4bnOWezIVYDR0WhpgvMHvdVdbrB/Lwa9ov7Jrd6HWubST9cn8PSnI2muUbWRkOkMVCO n63UPa0S+f5KXgY1VWUkeGZHp5DucgdYNqx76C4WrBz9ExgmNiRxCw2ZToRxtV34RywpdFEoeYm5Dh gRc81k6i8db9zmxTgKlvUrPfXL8iqs4jwUepd9+NQt7Yz/i0xdxt5XIs2KExN0yhbcroxJWbMAEESM a3lGizpea2DK3p7Cb1Z6+NiuYN0N8N3Av9fG/dClYe7QZikg+unIu486eoLHxK0claKGNRlqZ9MDUn mLcPSHM8abPdY8TKtTIGhcAXPTgNAp7j2iQ5kSRGPqGXjA4jFUd6f5FNmljiYjGfDKocVf3xYAXNMK 7Kr3rwk3ePpwmKjh+xpYMLv8bwU1Gv0jJUozhmSohVa+w= X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220427_101304_779088_752DDE19 X-CRM114-Status: GOOD ( 11.54 ) 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 In order to set bit #0 of the struct static_key pointer in the the jump label struct, we currently cast the pointer to char[], and take the address of either the 0th or 1st array member, depending on the value of 'branch'. This works but creates problems with -fpie code generation: GCC complains about the constraint being unsatisfiable, and Clang miscompiles the code in a way that causes stability issues (immediate panic on 'attempt to kill init') So instead, pass the struct static_key reference and the 'branch' immediate individually, in a way that satisfies both GCC and Clang (GCC wants the 'S' constraint, whereas Clang wants the 'i' constraint for argument %0) Signed-off-by: Ard Biesheuvel --- arch/arm64/include/asm/jump_label.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/arm64/include/asm/jump_label.h b/arch/arm64/include/asm/jump_label.h index cea441b6aa5d..f741bbacf175 100644 --- a/arch/arm64/include/asm/jump_label.h +++ b/arch/arm64/include/asm/jump_label.h @@ -23,9 +23,9 @@ static __always_inline bool arch_static_branch(struct static_key *key, " .pushsection __jump_table, \"aw\" \n\t" " .align 3 \n\t" " .long 1b - ., %l[l_yes] - . \n\t" - " .quad %c0 - . \n\t" + " .quad %c0 - . + %1 \n\t" " .popsection \n\t" - : : "i"(&((char *)key)[branch]) : : l_yes); + : : "Si"(key), "i"(branch) : : l_yes); return false; l_yes: @@ -40,9 +40,9 @@ static __always_inline bool arch_static_branch_jump(struct static_key *key, " .pushsection __jump_table, \"aw\" \n\t" " .align 3 \n\t" " .long 1b - ., %l[l_yes] - . \n\t" - " .quad %c0 - . \n\t" + " .quad %c0 - . + %1 \n\t" " .popsection \n\t" - : : "i"(&((char *)key)[branch]) : : l_yes); + : : "Si"(key), "i"(branch) : : l_yes); return false; l_yes: