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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, 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 05F3EC433DB for ; Sat, 27 Mar 2021 10:37:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BA518619F2 for ; Sat, 27 Mar 2021 10:37:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229883AbhC0KhV (ORCPT ); Sat, 27 Mar 2021 06:37:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:36826 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229875AbhC0KhV (ORCPT ); Sat, 27 Mar 2021 06:37:21 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id B989C619E8; Sat, 27 Mar 2021 10:37:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1616841429; bh=Mt7kcgav9t3UMu8lOOB6Tru6R5Kg48wvZoEAI9VQWC8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=DSyPj5WsKtNFR6bG0KEoMU8yTTTOjQ9wGQ6ZjMaPAxEkH4K3DwpCFylYrq47HhSMh E5Gdr3RKwmCd6g+pn7sypeylG/54ZovWQyhGcCoCztui8lr25pXoSy7AmpKpNf8Ziq 9DNhHoNhgUorhPhsldmYaypevoKllJisZweqbh2E= Date: Sat, 27 Mar 2021 11:37:06 +0100 From: Greg Kroah-Hartman To: Alexander Lochmann Cc: Dmitry Vyukov , Andrey Konovalov , Jonathan Corbet , Randy Dunlap , Andrew Klychkov , Miguel Ojeda , Andrew Morton , Jakub Kicinski , Aleksandr Nogikh , Wei Yongjun , Maciej Grochowski , kasan-dev@googlegroups.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCHv3] Introduced new tracing mode KCOV_MODE_UNIQUE. Message-ID: References: <20210326205135.6098-1-info@alexander-lochmann.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210326205135.6098-1-info@alexander-lochmann.de> Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Fri, Mar 26, 2021 at 09:51:28PM +0100, Alexander Lochmann wrote: > It simply stores the executed PCs. > The execution order is discarded. > Each bit in the shared buffer represents every fourth > byte of the text segment. > Since a call instruction on every supported > architecture is at least four bytes, it is safe > to just store every fourth byte of the text segment. > In contrast to KCOV_MODE_TRACE_PC, the shared buffer > cannot overflow. Thus, all executed PCs are recorded. Odd line-wrapping :( Anyway, this describes _what_ this does, but I have no idea _why_ we want this at all. What does this do that you can not do today? Why is this needed? Who will use this? What tools have been modified to work with it to prove it works properly? thanks, greg k-h