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=-5.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 ABB6AC54E4B for ; Tue, 12 May 2020 07:36:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8255B207FF for ; Tue, 12 May 2020 07:36:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589268962; bh=mwdUCDRsQcd4tBUSrGY2SY7Tr80S7IIqcEq7gM+QFyo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=DjW6KJBXNuFEN9R1Hl1xDw6fIO162KF9D73yD2tUpzKLf+/7Xuhbui4m2epzc0YeD Znih3lzOUdsz6pBrzRq8lvXBmY0Su17FeYOxIlY31C/4tp0EgOILRkU1U/jfrw2tui /XykK3+ARiMLJAhNVdpQGTi2JjH2eyoNiYgzvTog= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728990AbgELHgB (ORCPT ); Tue, 12 May 2020 03:36:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:42314 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728949AbgELHgB (ORCPT ); Tue, 12 May 2020 03:36:01 -0400 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B5F32206B7; Tue, 12 May 2020 07:35:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589268960; bh=mwdUCDRsQcd4tBUSrGY2SY7Tr80S7IIqcEq7gM+QFyo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=t5R7cSJlDsOP/Rq15vISPrYY6nRgt0EcIH9XTuDyRC2GPJ6DWnRnmhKdfTiy4a30Y VJDL7O2w+OjJd6KbOlyAT9++Kn8lwIjNjkC+57eIGAzvYLg5+3SymfzalRlvTKRmLj Akz/XtkhIvyCU63jhozKZ3BdSOgowTXCmGBDg64I= Date: Tue, 12 May 2020 08:35:53 +0100 From: Will Deacon To: Doug Anderson Cc: Jason Wessel , Daniel Thompson , Greg Kroah-Hartman , Andy Gross , kgdb-bugreport@lists.sourceforge.net, Catalin Marinas , linux-serial@vger.kernel.org, Sumit Garg , Jonathan Corbet , Ingo Molnar , "H. Peter Anvin" , Thomas Gleixner , Frank Rowand , bp@alien8.de, Bjorn Andersson , Jiri Slaby , Alexios Zavras , Allison Randal , Dave Martin , "Eric W. Biederman" , James Morse , Mark Rutland , Masami Hiramatsu , jinho lim , Linux ARM , LKML Subject: Re: [PATCH v3 05/11] arm64: Add call_break_hook() to early_brk64() for early kgdb Message-ID: <20200512073552.GA1538@willie-the-truck> References: <20200428211351.85055-1-dianders@chromium.org> <20200428141218.v3.5.I22067ad43e77ddfd4b64c2d49030628480f9e8d9@changeid> <20200511145908.GA22040@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org On Mon, May 11, 2020 at 03:45:02PM -0700, Doug Anderson wrote: > On Mon, May 11, 2020 at 7:59 AM Will Deacon wrote: > > On Tue, Apr 28, 2020 at 02:13:45PM -0700, Douglas Anderson wrote: > > > diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c > > > index 48222a4760c2..59c353dfc8e9 100644 > > > --- a/arch/arm64/kernel/debug-monitors.c > > > +++ b/arch/arm64/kernel/debug-monitors.c > > > @@ -297,7 +297,7 @@ void unregister_kernel_break_hook(struct break_hook *hook) > > > unregister_debug_hook(&hook->node); > > > } > > > > > > -static int call_break_hook(struct pt_regs *regs, unsigned int esr) > > > +int call_break_hook(struct pt_regs *regs, unsigned int esr) > > > { > > > struct break_hook *hook; > > > struct list_head *list; > > > diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c > > > index cf402be5c573..a8173f0c1774 100644 > > > --- a/arch/arm64/kernel/traps.c > > > +++ b/arch/arm64/kernel/traps.c > > > @@ -1044,6 +1044,9 @@ int __init early_brk64(unsigned long addr, unsigned int esr, > > > if ((comment & ~KASAN_BRK_MASK) == KASAN_BRK_IMM) > > > return kasan_handler(regs, esr) != DBG_HOOK_HANDLED; > > > #endif > > > + if (call_break_hook(regs, esr) == DBG_HOOK_HANDLED) > > > + return 0; > > > > I think this just means we're not running debug_traps_init() early enough, > > and actually the KASAN early handler is unnecessary too. > > > > If we call debug_traps_init() directly from setup_arch() and drop the > > arch_initcall(), can we then drop early_brk64 entirely? > > It seems to work in my testing. ...but the worry I have is the > comment right before trap_init(). It says: > > /* This registration must happen early, before debug_traps_init(). */ I /think/ the reason for this is because debug_traps_init() replaces the BRK vector, so if that runs before the break hooks have been registered for e.g. BUG() then BUG() won't work during that window. Hmm, so dropping early_brk64 is problematic after all. Damn. Is trap_init() early enough for you? If so, we could call debug_traps_init() from traps_init() after registering the break hooks. Will