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 D6EBF70AD7 for ; Thu, 29 Feb 2024 15:56:48 +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=1709222210; cv=none; b=XK46t64yDjZrBaE823AqliVeg5Kba//QrizNNnzRCoysWuRLrvT7DKYs/tSz8YVvA1VtuZAX7bIJRikz4uk6ruwnhdJqwGA1NS+cHD+oHfk70tLxP/7PT2FzOnlbe/dXmS+gr9ufq63VAUNGuTJcSs5hTya1Uzihmio1AaELi9k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709222210; c=relaxed/simple; bh=NSsjwYacVaMu1w7Lnxw+r+og5NN001gTRxc21cDBn5Q=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ASTZXkp8Uft2kF1w9RY3giqKR1kseQU8wjGnobydA4Ghd0oqG5XzQibJitQZR+TE0yX+WBfw81Z+H2c4WY4OunbU39kPwMAiP/7GD7U2jI40Dfrd+F6+O3eqbKkwq7EyOdqltXI1JCOtCoWunaS2Ldlr2UnuGxmnlMJYQ7MovNU= 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 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> 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: <20240229154851.2849367-7-sashal@kernel.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 >