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 8BD5AC433F5 for ; Thu, 6 Oct 2022 09:09:53 +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:Cc:To:Subject:Message-ID:Date:From: In-Reply-To:References:MIME-Version:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=+UAtyuy6d568k1aay8W0GH4hBin9tlFPgfT3u1bU96U=; b=ldNqZyzUcB+zRj ZGm2B9/4Qo7chAAgd+irUrH0/43OsbNtZ3UP3p+eUpaP1vbtAY/TDbAmLV3sAcFm31lIjDbf3EP5s RYEQlR9OPiCr1IsNJWLp0fzyy7VlT/1hbsggL6Wsrp+6NcTS8emWtwNkj83A0ztrmEj5VK0jaYPIo G97G6qUAAqGv/3tNoh7nmhEGwXRk5tk6c7Z9Wh4Z9KTA64CeMMQK4MvwbWY6lWMvSdrcAfEq2AwHG 9fHiUAHVOyFSToy5haU5RNb3z8SNCYGcwCG1MhWA/66X7za0cbt5/VD410GG5Wv3gC0wfCNJLVQ8q XfOoyH5VVLe1RGKSfGtg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ogMs7-000yNu-Si; Thu, 06 Oct 2022 09:08:52 +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 1ogMs3-000yKb-CE for linux-arm-kernel@lists.infradead.org; Thu, 06 Oct 2022 09:08:49 +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 A3E66618D1 for ; Thu, 6 Oct 2022 09:08:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1B36EC4347C for ; Thu, 6 Oct 2022 09:08:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1665047326; bh=SCoqS5eS6YE/AaM9otUbiginKmtjmNFJKRyykjM1IOk=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=pZlEAjPoF6mpa8RZIq9TvZU6BNMFdfAcfzP/xBAZ+70Lv2I6huG3ZHilhbrOCkfxE 3KQP7w5rzKhymlPH1b5xInc671ZME9OCHZuPKB4R+UB0r46YbZdzXw0D2VsoiVJ/se 7WkoUAA/+xpzQvtkuhShubzQjkKiRBhwSqPIX1jsj1V6d5y7afVdc0XchQ0fsBzi7p wjxQoid2VuQK/RS/R7+HgA8KDZFF8zt5DHp8O3t2QdKbP/jSoPQER8wWhfL44JXg7Z I7ouXUf3usci3/aVN4QcnJ7VUGF/5z+L0TKaVEfnK0DQe8qMF8PTwVNOjbooYlDSw/ 8A+YoC8oMMXtQ== Received: by mail-lf1-f46.google.com with SMTP id bp15so1726338lfb.13 for ; Thu, 06 Oct 2022 02:08:45 -0700 (PDT) X-Gm-Message-State: ACrzQf1SmkNazzpmVMBlyebyH/sS3NArlMs9hnSjtW9pc+eKJ81v2FmE oTxRnMuXh70NV/FeEaI1mKyu2yCICs/Vqo4cmDE= X-Google-Smtp-Source: AMsMyM7AOb9QrCzFf8WgjJca1KrbMRTJ/avD7fs3zNtgZo48Pud5Adz8r24Rw6EopBNDjaFjfwZSNIWssfbNUd3LH6Y= X-Received: by 2002:ac2:4d1c:0:b0:4a2:4119:f647 with SMTP id r28-20020ac24d1c000000b004a24119f647mr1355428lfi.426.1665047324034; Thu, 06 Oct 2022 02:08:44 -0700 (PDT) MIME-Version: 1.0 References: <20221006075542.2658-1-jszhang@kernel.org> <20221006075542.2658-2-jszhang@kernel.org> In-Reply-To: From: Ard Biesheuvel Date: Thu, 6 Oct 2022 11:08:32 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 1/2] arm64: jump_label: mark arguments as const to satisfy asm constraints To: Jisheng Zhang 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221006_020847_543632_60EC6E90 X-CRM114-Status: GOOD ( 26.89 ) 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, 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? > > > > > 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