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 65C19C48BF6 for ; Thu, 29 Feb 2024 15:57:03 +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=BGd1b+YDFMkg/bi05PhtYnAWmOnzzQlPoSb1ILRpQQY=; b=q8hI+HG5BuB3L8 FrPXcS/z4UHR8eV59aCYefuaHLVp3AryoP/Yml1aJwAOsG/7/9bNzIwD+D8ueY07H/Ng2Tu7RVVIn x2RJQ6CqCHNDVql3prozTR3lPBXt8AgaF3bnxExa9HXrVxuX4t6QYcZiK7yjqFHG8k5pL44B2At+C V9VGXNu6zhwJtehtv3AUtn2WJ2LxX/V9+1FWxMX9VA5oPPrOnjh1J/SrtdTZBaCia9nMQs5pqHqQ1 jxfv0Lg0Kcd1pCTkk2kxxogK/nT7ovSViF6KaXpoMVjdKb0jPbPQeiw/xdMX+Q9NrknYiAwOrW7Jv U37ej2V7NQiK/MeBd9BA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rfimD-0000000EA3L-1JRL; Thu, 29 Feb 2024 15:56:53 +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 1rfim9-0000000EA1p-39tc for linux-arm-kernel@lists.infradead.org; Thu, 29 Feb 2024 15:56:51 +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 D93441FB; Thu, 29 Feb 2024 07:57:26 -0800 (PST) Received: from FVFF77S0Q05N (unknown [10.57.68.196]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D02F33F6C4; Thu, 29 Feb 2024 07:56:45 -0800 (PST) Date: Thu, 29 Feb 2024 15:56:40 +0000 From: Mark Rutland To: Sasha Levin Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Fangrui Song , Ard Biesheuvel , Will Deacon , peterz@infradead.org, jpoimboe@kernel.org, jbaron@akamai.com, catalin.marinas@arm.com, nathan@kernel.org, linux-arm-kernel@lists.infradead.org, llvm@lists.linux.dev Subject: Re: [PATCH AUTOSEL 6.7 07/26] arm64: jump_label: use constraints "Si" instead of "i" Message-ID: References: <20240229154851.2849367-1-sashal@kernel.org> <20240229154851.2849367-7-sashal@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240229154851.2849367-7-sashal@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240229_075649_924785_0DD4EAE0 X-CRM114-Status: GOOD ( 22.03 ) 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, Feb 29, 2024 at 10:48:26AM -0500, Sasha Levin wrote: > From: Fangrui Song > > [ Upstream commit f9daab0ad01cf9d165dbbbf106ca4e61d06e7fe8 ] That upstream patch caused issues and was subsequently reverted in commit: a6b3eb304a82c29665a0ab947cfe276f6d29f523 ("Revert "arm64: jump_label: use constraints "Si" instead of "i""") Please drop this; it'll break stable in the same way, and it wasn't necessary to backport in the first place. As an aside, that revert has been upstream since v6.8-rc4, ~2.5 weeks ago; it's unfortunate for the broken patch to be AUTOSEL'd now! It'd be good if something could automatically check for reverts in mainline... Mark. > 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] > Acked-by: Mark Rutland > Link: https://lore.kernel.org/r/20240206074552.541154-1-maskray@google.com > Signed-off-by: Will Deacon > Signed-off-by: Sasha Levin > --- > 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 48ddc0f45d228..b7716b215f91a 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 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel