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 X-Spam-Level: X-Spam-Status: No, score=-3.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0486DC433E0 for ; Tue, 19 May 2020 09:02:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CD77A2088E for ; Tue, 19 May 2020 09:02:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="GvILhhcI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727123AbgESJCt (ORCPT ); Tue, 19 May 2020 05:02:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33946 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726333AbgESJCs (ORCPT ); Tue, 19 May 2020 05:02:48 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A1ECBC061A0C for ; Tue, 19 May 2020 02:02:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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=QVvLau/9rnCPsCtt46lwjQQtMKtK/oxJF//68Ttv+kc=; b=GvILhhcIZtJOf8m0a2HgOo2CTD 4y13cf35CqBx7M4Wk5ISf0byOEUzHU3ihh3Tr1yPD1F4Lye9HtppxWVr2F0Uf7PbXq6MFEcqhaVyP THqXaMJa6ODe6RTRH98GNbagiBN8yFYSz9Px2NAHzIL9Yw69vvj6VCXfOAZAqJ+keN7IL3kZQKXsL qLg9Mae1MOV+b2JJ/OfKg3ILTLF7SuvCBo83wZgqPNy9jX7RXws7m6UwkE/uZDX6TjE3pPIdfXF63 HqPfMou0yV6xotCYd1i30tKPQ4rjuVNuPhuOBChcGud/LAH2lNZsLYEPXu4p+inUH23CmX6WOp55E tN6pmksw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jay8r-0002i1-Fo; Tue, 19 May 2020 09:02:29 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 6EEC130067C; Tue, 19 May 2020 11:02:26 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 37A9D2105F3AF; Tue, 19 May 2020 11:02:26 +0200 (CEST) Date: Tue, 19 May 2020 11:02:26 +0200 From: Peter Zijlstra To: Thomas Gleixner Cc: LKML , x86@kernel.org, "Paul E. McKenney" , Andy Lutomirski , Alexandre Chartre , Frederic Weisbecker , Paolo Bonzini , Sean Christopherson , Masami Hiramatsu , Petr Mladek , Steven Rostedt , Joel Fernandes , Boris Ostrovsky , Juergen Gross , Brian Gerst , Mathieu Desnoyers , Josh Poimboeuf , Will Deacon , Tom Lendacky , Wei Liu , Michael Kelley , Jason Chen CJ , Zhao Yakui Subject: Re: [patch V6 00/37] x86/entry: Rework leftovers and merge plan Message-ID: <20200519090226.GD279861@hirez.programming.kicks-ass.net> References: <20200518160750.GA279861@hirez.programming.kicks-ass.net> <87367xvvmy.fsf@nanos.tec.linutronix.de> <20200519083826.GC279861@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200519083826.GC279861@hirez.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 19, 2020 at 10:38:26AM +0200, Peter Zijlstra wrote: > $ make CC=gcc-9 O=defconfig-build/ vmlinux -j40 -s > vmlinux.o: warning: objtool: exc_debug()+0x158: call to trace_hwlat_timestamp() leaves .noinstr.text section > vmlinux.o: warning: objtool: exc_nmi()+0x190: call to trace_hwlat_timestamp() leaves .noinstr.text section > vmlinux.o: warning: objtool: do_machine_check()+0x46: call to mce_rdmsrl() leaves .noinstr.text section > $ > > (it really isn't defconfig, but your config-fail + DEBUG_ENTRY) > With comment on, as requested. --- diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h index f128e5c2ed42..fb34ff641e0a 100644 --- a/arch/x86/include/asm/bug.h +++ b/arch/x86/include/asm/bug.h @@ -79,8 +79,8 @@ do { \ do { \ instrumentation_begin(); \ _BUG_FLAGS(ASM_UD2, BUGFLAG_WARNING|(flags)); \ - instrumentation_end(); \ annotate_reachable(); \ + instrumentation_end(); \ } while (0) #include diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 7db5902f8f6e..4b8fabed46ae 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -120,25 +120,61 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, /* Annotate a C jump table to allow objtool to follow the code flow */ #define __annotate_jump_table __section(.rodata..c_jump_table) +#ifdef CONFIG_DEBUG_ENTRY /* Begin/end of an instrumentation safe region */ -#define instrumentation_begin() ({ \ +#define instrumentation_begin() ({ \ asm volatile("%c0:\n\t" \ ".pushsection .discard.instr_begin\n\t" \ ".long %c0b - .\n\t" \ ".popsection\n\t" : : "i" (__COUNTER__)); \ }) -#define instrumentation_end() ({ \ - asm volatile("%c0:\n\t" \ +/* + * Because instrumentation_{begin,end}() can nest, objtool validation considers + * _begin() a +1 and _end() a -1 and computes a sum over the instructions. + * When the value is greater than 0, we consider instrumentation allowed. + * + * There is a problem with code like: + * + * noinstr void foo() + * { + * instrumentation_begin(); + * ... + * if (cond) { + * instrumentation_begin(); + * ... + * instrumentation_end(); + * } + * bar(); + * instrumentation_end(); + * } + * + * If instrumentation_end() would be an empty label, like all the other + * annotations, the inner _end(), which is at the end of a conditional block, + * would land on the instruction after the block. + * + * If we then consider the sum of the !cond path, we'll see that the call to + * bar() is with a 0-value, even though, we meant it to happen with a positive + * value. + * + * To avoid this, have _end() be a NOP instruction, this ensures it will be + * part of the condition block and does not escape. + */ +#define instrumentation_end() ({ \ + asm volatile("%c0: nop\n\t" \ ".pushsection .discard.instr_end\n\t" \ ".long %c0b - .\n\t" \ ".popsection\n\t" : : "i" (__COUNTER__)); \ }) +#endif /* CONFIG_DEBUG_ENTRY */ #else #define annotate_reachable() #define annotate_unreachable() #define __annotate_jump_table +#endif + +#ifndef instrumentation_begin #define instrumentation_begin() do { } while(0) #define instrumentation_end() do { } while(0) #endif