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=-8.6 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=ham 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 1306AC43381 for ; Wed, 6 Mar 2019 14:41:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D3B7C206DD for ; Wed, 6 Mar 2019 14:41:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Fmczhx+1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728952AbfCFOlk (ORCPT ); Wed, 6 Mar 2019 09:41:40 -0500 Received: from mail-io1-f65.google.com ([209.85.166.65]:32988 "EHLO mail-io1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726913AbfCFOlj (ORCPT ); Wed, 6 Mar 2019 09:41:39 -0500 Received: by mail-io1-f65.google.com with SMTP id e186so10398225ioa.0 for ; Wed, 06 Mar 2019 06:41:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=K2WfZ12UmlecEWrugyx7y8Ud5L7Bf4NFhWfw1yQJtMg=; b=Fmczhx+1mVEkvwVBWd64Z2jO5vITtAJw3ya/oju8udASiaj7D8q9x7WI/rcd2YXy8S zry82lL7ncHKeGT4QnU4ClqTpsqxywAy1dN5Q/HhPFQllmMydrvj10HAiDGljJxO4tZj 0OhGdog2DLcjCrF7NDxs9OhbcHg+SJzjIf7Ayu7fFzgT8tmWcUIVOj6YRKTphKfeunLe EPFqadA0OT/+UF7XmpAqld2+Vb48gT03uMQAQ8b/kNJWqSImbt0E+GtBkOKr5Sw6wcPf yeDPdCvIdKUSY0Yy7Llf56z9KRtd4nE9xaiLiJtRk4zm1gs2nX0wGTfmTvC6oAoBn+8E yBKg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=K2WfZ12UmlecEWrugyx7y8Ud5L7Bf4NFhWfw1yQJtMg=; b=socI/VVFvLBFXD7QQy3x/hmq1qUMuenvH/8FP2UBQbDfmYVdU9/MdOg+j6Rd/FBEJK 3CVmyQ3WfDLC5YfYAp3MgwF7HNmrr69m9xmdFBZyQvLNCzD4JIzdONXLz25CU4NlvjVw MxsBSY3umAlXjB/vwaR1emktdwtr7tV1JRIZcmToXfab8HkvutRynBnffyS90ZYF/j3J aoOYoxExsbRq6oQPgyyWc/fBlEdvp4IkeD0C+wIFQEZxPIPXs0FStO82thzOJ7qnabAE Ds5/YQ//sc0yqhN0WyJ7kAKm5KijPINtWvl4XQC3l43DJWHySoLZJuyhgFdJbdENkDm6 yRDg== X-Gm-Message-State: APjAAAXdiFuZ2rE68N2/vUOtODpvEf7p/0h3D8V8PkSdeZtrcohJGg1r CnWfYmUu4amGktFbSbS+LaySLEfUcKZaahHbnE7Twg== X-Google-Smtp-Source: APXvYqzvy4RTi7BFgskAPvx0x90xmhdiCUKqrDuaKSxvT6bjBZ8vG2uC5IkvGDukAJz4i02im6ClUqTBwb2vP97nnTo= X-Received: by 2002:a5d:834a:: with SMTP id q10mr3091863ior.271.1551883298492; Wed, 06 Mar 2019 06:41:38 -0800 (PST) MIME-Version: 1.0 References: <20190228150152.078767622@infradead.org> <20190301144556.GY32477@hirez.programming.kicks-ass.net> <20190301152305.GJ32494@hirez.programming.kicks-ass.net> <20190306131347.GX32534@hirez.programming.kicks-ass.net> <20190306135728.GV32477@hirez.programming.kicks-ass.net> <20190306141237.GW32477@hirez.programming.kicks-ass.net> <20190306143439.GY32534@hirez.programming.kicks-ass.net> In-Reply-To: From: Dmitry Vyukov Date: Wed, 6 Mar 2019 15:41:27 +0100 Message-ID: Subject: Re: [PATCH 1/8] kasan,x86: Frob kasan_report() in an exception To: Peter Zijlstra Cc: Linus Torvalds , Thomas Gleixner , "H. Peter Anvin" , Julien Thierry , Will Deacon , Andy Lutomirski , Ingo Molnar , Catalin Marinas , James Morse , valentin.schneider@arm.com, Brian Gerst , Josh Poimboeuf , Andy Lutomirski , Borislav Petkov , Denys Vlasenko , LKML , Andrey Ryabinin Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 6, 2019 at 3:40 PM Dmitry Vyukov wrote: > > On Wed, Mar 6, 2019 at 3:34 PM Peter Zijlstra wrote: > > > > On Wed, Mar 06, 2019 at 03:12:37PM +0100, Peter Zijlstra wrote: > > > On Wed, Mar 06, 2019 at 03:01:33PM +0100, Dmitry Vyukov wrote: > > > > On Wed, Mar 6, 2019 at 2:57 PM Peter Zijlstra wrote: > > > > > > > > I've not found callers of __asan_report_load* with AC=1 in the kernel > > > > > yet. Under what condtions does GCC emit calls to these functions? > > > > > > > > CONFIG_KASAN_INLINE=y > > > > Then compiler inlines fast path into generated code and only calls > > > > into runtime to report errors (also, faster, this should be a default > > > > for anything other than tiny ROM controllers). > > > > > > *sigh*, clearly I've not build enough kernels yet... Lemme go try that. > > > > mm/kasan/generic_report.o: warning: objtool: __asan_report_load1_noabort()+0x0: call to __fentry__() with UACCESS enabled > > > > You want to do: > > > > CFLAGS_REMOVE_f= -pg > > > > like generic.o has? > > This should not matter for KASAN itself. > KASAN will call into function tracer, and function tracer will call > into KASAN, but unless function tracer is badly broken and causes a > KASAN report on every invocation, the recursion will end (function > tracer will get to the _report_ function). So we only disabled -pg for tracer will _not_ get to the _report_ function > fast paths. > But if it makes things simpler for the objtool, then I think we can > disable function tracer for generic_report.c too.