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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8D52FC433F5 for ; Mon, 2 May 2022 13:01:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1385150AbiEBNFD (ORCPT ); Mon, 2 May 2022 09:05:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35406 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234379AbiEBNE7 (ORCPT ); Mon, 2 May 2022 09:04:59 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A0B05186CD for ; Mon, 2 May 2022 06:01:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=ZOpFXMvH6fVGm0NN978db6GomlYBIrV4k0UI7h49GGQ=; b=lGrjzTgKcz6Wno4DrkeqUYgsCs roZ/YyERXa8i5ToMVM6XWZ/La5QG3K7PizMeBD7DHrAaw0gx8mu2yLgkmBXlNbNfWd6BJmjPAThJF oSzAjiE2bvtqTkmZ+R3ht0Cfl1RdQxoCGUV0/wONgHtjSUIq52GX3PoFhjwrWXkWgTyzezfxpwGBW Ig1LcrSGPYYCMgVeXmKQNHjTqfiEDykgAewYcN9JI1/P36hM9OuoKYc/1mLqbQIzVG4WJzbVCVLUK rc0NSMNng0B9QOKkAsvheN2lBpQWzgyOzrkpk+T1vArvzfsNTaBub+mx5XXgPcrxGPYQDqobPseW5 cf9TPKbQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1nlVfs-00Ep7O-9f; Mon, 02 May 2022 13:01:12 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id E9424300091; Mon, 2 May 2022 15:01:09 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id B9B3E20288CF0; Mon, 2 May 2022 15:01:09 +0200 (CEST) Date: Mon, 2 May 2022 15:01:09 +0200 From: Peter Zijlstra To: Marco Elver Cc: x86@kernel.org, jpoimboe@redhat.com, linux-kernel@vger.kernel.org, jbaron@akamai.com, rostedt@goodmis.org, ardb@kernel.org, kernel test robot Subject: Re: [PATCH 3/3] jump_label,noinstr: Avoid instrumentation for JUMP_LABEL=n builds Message-ID: References: <20220502110741.951055904@infradead.org> <20220502111216.350926848@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 02, 2022 at 01:23:49PM +0200, Marco Elver wrote: > On Mon, 2 May 2022 at 13:12, Peter Zijlstra wrote: > > > > When building x86_64 with JUMP_LABEL=n it's possible for > > instrumentation to sneak into noinstr: > > > > vmlinux.o: warning: objtool: exit_to_user_mode+0x14: call to static_key_count.constprop.0() leaves .noinstr.text section > > vmlinux.o: warning: objtool: syscall_exit_to_user_mode+0x2d: call to static_key_count.constprop.0() leaves .noinstr.text section > > vmlinux.o: warning: objtool: irqentry_exit_to_user_mode+0x1b: call to static_key_count.constprop.0() leaves .noinstr.text section > > > > Reported-by: kernel test robot > > Signed-off-by: Peter Zijlstra (Intel) > > --- > > include/linux/jump_label.h | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > --- a/include/linux/jump_label.h > > +++ b/include/linux/jump_label.h > > @@ -256,9 +256,9 @@ extern void static_key_disable_cpuslocke > > #include > > #include > > > > -static inline int static_key_count(struct static_key *key) > > +static __always_inline int static_key_count(struct static_key *key) > > { > > - return atomic_read(&key->enabled); > > + return READ_ONCE_NOCHECK(&key->enabled.count); > > } > > Did arch_atomic_read() not work? Or should this also be unchecked in > instrumented functions? Urgh, also I think the above is broken for me forgetting to remove the &. I think arch_atomic_read() should work, lemme try.