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 0A8A1C4332F for ; Thu, 6 Oct 2022 11:15:17 +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:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=mSG3Y5FOloiWfp6MWadJGbjD6sffP7gi2K2nrsI9n7s=; b=nMJ+XwiqSnWjqq +2EnwpKoVxGNwRa0PSBTj6xOyrTkMdhoh1AZAXd1YHNjEHgvTKqjsN17LbzJYAcCFpaaC4uuEFaVo 7kcyj/6p/azhzPh2DJ1EVK2JXDgDWNIsf1PnMaXl/xqp7z1PGFUuChtO+LaEXgFHs/RfPEsEnHozr Y8NGHFEsh9Y90hq1Bz1XL/AxWn7u4/wXbIU5ElD0tXrFA/C1saAbYbVqqdmhQTMddXLKVpCMMrP+n ELYtTH6L6h4yaOUvXNc72dFGt8/hr0ilOCIQDnhDgqC0B/LdUhf3RmBqiGan+CBVuuqZBlECdzFyd 4jjURHMIyFqsyZKltK8A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ogOpO-001moE-24; Thu, 06 Oct 2022 11:14:10 +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 1ogOpG-001mjK-RO for linux-arm-kernel@lists.infradead.org; Thu, 06 Oct 2022 11:14:04 +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 CF2B961913; Thu, 6 Oct 2022 11:13:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3AC5CC433D7; Thu, 6 Oct 2022 11:13:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1665054839; bh=VTJaSrvMCWUH+N0JSZ2qm6FMkJt92jHhy1j8tHwRJX0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=qDfnFRl4UbgOWgtEwlzEsPz3USenXbNL+BtASjhG3+pPyB9JrCysUg7fULliky8NJ hGkfz6UZ5nDY4hQZy+ij6DDeZRo5Kbd39r2MUxcg+H0QtFXifetUnGl2oC0VsQ0iHc YnL7VQBXhQxK33gJdhEguk20EfBUIrypjCAhG5EtTTD4JoGAAXdXqV/rEdNLrq8bNa 94JXQb+yZ2r3Wmv6NkW9fL737YIBahYMxWjxLPVdpmFSz0Ax7iXfmV8ZLztPczjgGs F6fNX2kU1B16+vVZo/50CkZZRidpRX/PxEFtRSOg0s/XAHTBDPkiGzdr8I+q6oG26m S06I2mpU7dbnA== Date: Thu, 6 Oct 2022 19:04:25 +0800 From: Jisheng Zhang To: Ard Biesheuvel Cc: Catalin Marinas , Will Deacon , Peter Zijlstra , Josh Poimboeuf , Jason Baron , Steven Rostedt , Mark Rutland , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] arm64: jump_label: mark arguments as const to satisfy asm constraints Message-ID: References: <20221006075542.2658-1-jszhang@kernel.org> <20221006075542.2658-2-jszhang@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221006_041402_987407_828061FF X-CRM114-Status: GOOD ( 26.65 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Oct 06, 2022 at 11:08:32AM +0200, Ard Biesheuvel wrote: > On Thu, 6 Oct 2022 at 10:55, Jisheng Zhang wrote: > > > > On Thu, Oct 06, 2022 at 10:17:44AM +0200, Ard Biesheuvel wrote: > > > On Thu, 6 Oct 2022 at 10:05, Jisheng Zhang wrote: > > > > > > > > Inspired by x86 commit 864b435514b2("x86/jump_label: Mark arguments as > > > > const to satisfy asm constraints"), mark arch_static_branch()'s and > > > > arch_static_branch_jump()'s arguments as const to satisfy asm > > > > constraints. And Steven in [1] also pointed out that "The "i" > > > > constraint needs to be a constant." > > > > > > > > Tested with building a simple external kernel module with "O0". > > > > > > > > [1]https://lore.kernel.org/all/20210212094059.5f8d05e8@gandalf.local.home/ > > > > > > > > Signed-off-by: Jisheng Zhang > > > > --- > > > > 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..48ddc0f45d22 100644 > > > > --- a/arch/arm64/include/asm/jump_label.h > > > > +++ b/arch/arm64/include/asm/jump_label.h > > > > @@ -15,8 +15,8 @@ > > > > > > > > #define JUMP_LABEL_NOP_SIZE AARCH64_INSN_SIZE > > > > > > > > -static __always_inline bool arch_static_branch(struct static_key *key, > > > > - bool branch) > > > > +static __always_inline bool arch_static_branch(struct static_key * const key, > > > > + const bool branch) > > > > { > > > > asm_volatile_goto( > > > > "1: nop \n\t" > > > > > > Is this still necessary if we specify the constraints in a more > > > reasonable manner: > > > > > > " .quad %c0 - . + %1 \n\t" > > > : : "i"(key), "i"(branch) : : l_yes); > > > > Just tried this locally with the simple external kernel module, the > > asm operand 0 probably does not match constraints can still be > > reproduced with "O0". > > > > OK so the key pointer needs to be pointer-to-const, which makes sense. > How about when using "Si" as the constraint for operand 0? "Si" constraint doesn't help either. > > > > > > > > > > instead of the horrid hack with the char* cast and using a bool as an > > > array index? > > > > > > > > > > > > > > > > @@ -32,8 +32,8 @@ static __always_inline bool arch_static_branch(struct static_key *key, > > > > return true; > > > > } > > > > > > > > -static __always_inline bool arch_static_branch_jump(struct static_key *key, > > > > - bool branch) > > > > +static __always_inline bool arch_static_branch_jump(struct static_key * const key, > > > > + const bool branch) > > > > { > > > > asm_volatile_goto( > > > > "1: b %l[l_yes] \n\t" > > > > -- > > > > 2.37.2 > > > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel