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 EA924C4828F for ; Fri, 9 Feb 2024 11:11:36 +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=DREJ5pky83N69p6nP06XTTX3LmwEV/tPaZlI03luTTo=; b=qLlqfGBpdVQyXi hAkrMg0tSO4rR65xUoPvhVtUSQO4u+DhID7tJGrIISpuWVBJmw/ITgSpCQh0EchEZAqP02IdWF7dG PcVPPXD24THTU5sHgWKMtzOLpCMFNhS/QJw10PyKUIsSPB2T8B/u0W1RR8HIEExuoKyqMLybE7whL pimTg80uddBDjdHoxflTfN9+NfySVer4v6JoGJANJT+OXtMyu7+8EXdU50CWSkgu2itfosvrEzh5k v0puK8ZGPqzfjYKCKrdt0iifViDNbG+YW5qUZd1sOXjvQG/WCLdicQ+Bht6hN1fyozlievWN3Wc4y C6WqVDBwNu66WArwXSgA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rYOmz-0000000GoUR-1rZ9; Fri, 09 Feb 2024 11:11:25 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rYOmw-0000000GoU0-06eb for linux-arm-kernel@lists.infradead.org; Fri, 09 Feb 2024 11:11:23 +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 0A393DA7; Fri, 9 Feb 2024 03:12:01 -0800 (PST) Received: from FVFF77S0Q05N.cambridge.arm.com (FVFF77S0Q05N.cambridge.arm.com [10.1.31.163]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8332B3F762; Fri, 9 Feb 2024 03:11:17 -0800 (PST) Date: Fri, 9 Feb 2024 11:11:05 +0000 From: Mark Rutland To: Fangrui Song Cc: Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, Jisheng Zhang , Dave Martin , Ard Biesheuvel , Peter Smith , llvm@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] arm64: jump_label: use constraints "Si" instead of "i" Message-ID: References: <20240206074552.541154-1-maskray@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240206074552.541154-1-maskray@google.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240209_031122_381266_ED80143E X-CRM114-Status: GOOD ( 22.41 ) 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 Mon, Feb 05, 2024 at 11:45:52PM -0800, Fangrui Song wrote: > The generic constraint "i" seems to be copied from x86 or arm (and with > a redundant generic operand modifier "c"). It works with -fno-PIE but > not with -fPIE/-fPIC in GCC's aarch64 port. > > The machine constraint "S", which denotes a symbol or label reference > with a constant offset, supports PIC and has been available in GCC since > 2012 and in Clang since 7.0. However, Clang before 19 does not support > "S" on a symbol with a constant offset [1] (e.g. > `static_key_false(&nf_hooks_needed[pf][hook])` in > include/linux/netfilter.h), so we use "i" as a fallback. > > Suggested-by: Ard Biesheuvel > Signed-off-by: Fangrui Song > Link: https://github.com/llvm/llvm-project/pull/80255 [1] This looks reasonable to me, and works with the toolchains I've tried, so: Acked-by: Mark Rutland Mark. > --- > Changes from > arm64: jump_label: use constraint "S" instead of "i" (https://lore.kernel.org/all/20240131065322.1126831-1-maskray@google.com/) > > * Use "Si" as Ard suggested to support Clang<19 > * Make branch a separate operand > > Changes from v1: > > * Use asmSymbolicName for readability > --- > arch/arm64/include/asm/jump_label.h | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/include/asm/jump_label.h b/arch/arm64/include/asm/jump_label.h > index 48ddc0f45d22..b7716b215f91 100644 > --- a/arch/arm64/include/asm/jump_label.h > +++ b/arch/arm64/include/asm/jump_label.h > @@ -15,6 +15,10 @@ > > #define JUMP_LABEL_NOP_SIZE AARCH64_INSN_SIZE > > +/* > + * Prefer the constraint "S" to support PIC with GCC. Clang before 19 does not > + * support "S" on a symbol with a constant offset, so we use "i" as a fallback. > + */ > static __always_inline bool arch_static_branch(struct static_key * const key, > const bool branch) > { > @@ -23,9 +27,9 @@ static __always_inline bool arch_static_branch(struct static_key * const key, > " .pushsection __jump_table, \"aw\" \n\t" > " .align 3 \n\t" > " .long 1b - ., %l[l_yes] - . \n\t" > - " .quad %c0 - . \n\t" > + " .quad (%[key] - .) + %[bit0] \n\t" > " .popsection \n\t" > - : : "i"(&((char *)key)[branch]) : : l_yes); > + : : [key]"Si"(key), [bit0]"i"(branch) : : l_yes); > > return false; > l_yes: > @@ -40,9 +44,9 @@ static __always_inline bool arch_static_branch_jump(struct static_key * const ke > " .pushsection __jump_table, \"aw\" \n\t" > " .align 3 \n\t" > " .long 1b - ., %l[l_yes] - . \n\t" > - " .quad %c0 - . \n\t" > + " .quad (%[key] - .) + %[bit0] \n\t" > " .popsection \n\t" > - : : "i"(&((char *)key)[branch]) : : l_yes); > + : : [key]"Si"(key), [bit0]"i"(branch) : : l_yes); > > return false; > l_yes: > -- > 2.43.0.594.gd9cf4e227d-goog > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 6A68B25618 for ; Fri, 9 Feb 2024 11:11:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707477082; cv=none; b=ZGMglFvhzU1o5ki3EKgqec4LZQ8UET3NavMIWL8WY9H1Q6SmbQKu5vrdWQ9lkT4v4meG6fhNWBEkq4v3eXL2mpbwgu/lehN29yzptL0b9RSIdaKoJqCjxCbBuJjBlesvmml0kVx2HskADZaSSdn2W5v0wdoc+waPWU8uYk2uvTI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707477082; c=relaxed/simple; bh=YOqOwkuAEGeXh3W/ozSHwWeZ88PIMKCEKNwcOky05P0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZU4eieMxajPbZR9t9MV/axFCSb1aZqkO0ih2R1yr6GhN105fEA+QiY+zw5Qv+6D9qS3WTSFP3Agys2gRrFLBc186Htqr260KBPfQn0Hbdx8zDUe8lbQGGEhr/vY9GCbvfIpWqe1x2mGvFkS2vMZP6Y+AJY9VFh62NIW5LpXNyTg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 0A393DA7; Fri, 9 Feb 2024 03:12:01 -0800 (PST) Received: from FVFF77S0Q05N.cambridge.arm.com (FVFF77S0Q05N.cambridge.arm.com [10.1.31.163]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8332B3F762; Fri, 9 Feb 2024 03:11:17 -0800 (PST) Date: Fri, 9 Feb 2024 11:11:05 +0000 From: Mark Rutland To: Fangrui Song Cc: Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, Jisheng Zhang , Dave Martin , Ard Biesheuvel , Peter Smith , llvm@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] arm64: jump_label: use constraints "Si" instead of "i" Message-ID: References: <20240206074552.541154-1-maskray@google.com> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240206074552.541154-1-maskray@google.com> On Mon, Feb 05, 2024 at 11:45:52PM -0800, Fangrui Song wrote: > The generic constraint "i" seems to be copied from x86 or arm (and with > a redundant generic operand modifier "c"). It works with -fno-PIE but > not with -fPIE/-fPIC in GCC's aarch64 port. > > The machine constraint "S", which denotes a symbol or label reference > with a constant offset, supports PIC and has been available in GCC since > 2012 and in Clang since 7.0. However, Clang before 19 does not support > "S" on a symbol with a constant offset [1] (e.g. > `static_key_false(&nf_hooks_needed[pf][hook])` in > include/linux/netfilter.h), so we use "i" as a fallback. > > Suggested-by: Ard Biesheuvel > Signed-off-by: Fangrui Song > Link: https://github.com/llvm/llvm-project/pull/80255 [1] This looks reasonable to me, and works with the toolchains I've tried, so: Acked-by: Mark Rutland Mark. > --- > Changes from > arm64: jump_label: use constraint "S" instead of "i" (https://lore.kernel.org/all/20240131065322.1126831-1-maskray@google.com/) > > * Use "Si" as Ard suggested to support Clang<19 > * Make branch a separate operand > > Changes from v1: > > * Use asmSymbolicName for readability > --- > arch/arm64/include/asm/jump_label.h | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/include/asm/jump_label.h b/arch/arm64/include/asm/jump_label.h > index 48ddc0f45d22..b7716b215f91 100644 > --- a/arch/arm64/include/asm/jump_label.h > +++ b/arch/arm64/include/asm/jump_label.h > @@ -15,6 +15,10 @@ > > #define JUMP_LABEL_NOP_SIZE AARCH64_INSN_SIZE > > +/* > + * Prefer the constraint "S" to support PIC with GCC. Clang before 19 does not > + * support "S" on a symbol with a constant offset, so we use "i" as a fallback. > + */ > static __always_inline bool arch_static_branch(struct static_key * const key, > const bool branch) > { > @@ -23,9 +27,9 @@ static __always_inline bool arch_static_branch(struct static_key * const key, > " .pushsection __jump_table, \"aw\" \n\t" > " .align 3 \n\t" > " .long 1b - ., %l[l_yes] - . \n\t" > - " .quad %c0 - . \n\t" > + " .quad (%[key] - .) + %[bit0] \n\t" > " .popsection \n\t" > - : : "i"(&((char *)key)[branch]) : : l_yes); > + : : [key]"Si"(key), [bit0]"i"(branch) : : l_yes); > > return false; > l_yes: > @@ -40,9 +44,9 @@ static __always_inline bool arch_static_branch_jump(struct static_key * const ke > " .pushsection __jump_table, \"aw\" \n\t" > " .align 3 \n\t" > " .long 1b - ., %l[l_yes] - . \n\t" > - " .quad %c0 - . \n\t" > + " .quad (%[key] - .) + %[bit0] \n\t" > " .popsection \n\t" > - : : "i"(&((char *)key)[branch]) : : l_yes); > + : : [key]"Si"(key), [bit0]"i"(branch) : : l_yes); > > return false; > l_yes: > -- > 2.43.0.594.gd9cf4e227d-goog > >