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=-2.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 2B766C433ED for ; Sat, 17 Apr 2021 19:46:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E29AB60FEF for ; Sat, 17 Apr 2021 19:46:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237034AbhDQTq6 (ORCPT ); Sat, 17 Apr 2021 15:46:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59128 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236779AbhDQTq6 (ORCPT ); Sat, 17 Apr 2021 15:46:58 -0400 Received: from mail-ed1-x535.google.com (mail-ed1-x535.google.com [IPv6:2a00:1450:4864:20::535]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 03255C061574; Sat, 17 Apr 2021 12:46:30 -0700 (PDT) Received: by mail-ed1-x535.google.com with SMTP id i3so10465398edt.1; Sat, 17 Apr 2021 12:46:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=eSOJMwvIJkQU2JYaT7cb2vTqKYf6iPw1ySzK9GIZ1mE=; b=sfo1ZL4IgQFU2a/GIYfPYPNoASv/hTC8EXtSdm5D8WaqKRLhRkrGTSIlZ26izkLwi7 w8x8K1vXttMQP13GzODDnpCdBVZuLTzQShERLxCHX6TLEXSIpAd3rAL3lbQ0PADABVsH YA5oOOEDjpHvzT/dP4RT/ZiRiEy034kX0JZxZk4o0Y5UBO6syzwfb+agbs+R2SEAW/+k +OjJ/dxGqwRhv1jXxskU7kAj61la0qlDD05y6GXTjp+TAgYASdkoyH5u01sTyuaRKWoj tEEDftgbbEIZuZs1B9ITJFiDDo60JnR6r8JW3YxgECy43nvTm9y7MT2PKG5r1+fyzNsl yBOg== 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=eSOJMwvIJkQU2JYaT7cb2vTqKYf6iPw1ySzK9GIZ1mE=; b=S3rc71BOQgEA2eFV3JQrfibVYUGyS2EW8a9/HgceCBbIaGMBJDs0A/XiD9cOLnYxMg GTyHCEtuMoKsO7fIDDXTdmB9c/HaGADjyuqOTy4NCLd/v5dCt998Iy6UpuhVK/cOlxqV LrpSSAFjfNTYTFrAEytyc5IqdCBjcC6a+RP2GNzvyhj4JJJ6sjMiAvMusTPZzMkYcN+e KPKIVDJJwXbz23iXn7WSdBrJ966arLu1tPuYg3pCV21egQRfIEHqoFAxPRqVn737DikJ ZDAZwPQ/xN0TglXxRxDkz6cNjP60JYJNv9R+pDxn/kXfHntIpSY8c17Hc8xXzyvk7fko yu1g== X-Gm-Message-State: AOAM531WZhtpFqbrdf8GdJLmTW1/RI7+cZ3QDtqp0d7x9b53aeMSqQzg p8kzRsJaOdWFMc5F7L9qIxO2bL6IwhSlxYKGbSw= X-Google-Smtp-Source: ABdhPJwupn1AHPWkgNX5S4iHwJNtNuew20GI+CF5/KvqzL8rItIj/uzGeoXQIWZUulBDltLD4HWNwDeHrrCts+tPxAQ= X-Received: by 2002:a05:6402:4415:: with SMTP id y21mr16888070eda.70.1618688788715; Sat, 17 Apr 2021 12:46:28 -0700 (PDT) MIME-Version: 1.0 References: <20210326205135.6098-1-info@alexander-lochmann.de> In-Reply-To: From: Andrey Konovalov Date: Sat, 17 Apr 2021 21:46:18 +0200 Message-ID: Subject: Re: [PATCHv3] Introduced new tracing mode KCOV_MODE_UNIQUE. To: Dmitry Vyukov , Alexander Lochmann Cc: Andrey Konovalov , Jonathan Corbet , Randy Dunlap , Andrew Klychkov , Miguel Ojeda , Greg Kroah-Hartman , Andrew Morton , Jakub Kicinski , Aleksandr Nogikh , Wei Yongjun , Maciej Grochowski , kasan-dev , "open list:DOCUMENTATION" , LKML Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Fri, Apr 16, 2021 at 10:42 AM Dmitry Vyukov wrote: > > On Sat, Mar 27, 2021 at 3:56 PM Andrey Konovalov wrote: > > > > On Fri, Mar 26, 2021 at 9:52 PM Alexander Lochmann > > wrote: > > > > > > > Hi Alexander, > > > > > 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. > > > > What about jumps? > > KCOV adds call __sanitizer_cov_trace_pc per coverage point. So besides > the instructions in the original code, we also always have this call. Ah, I see. This should be explained in the changelog. This means that a KCOV user will need the kernel binary to recover the actual PCs that were covered, as the information about the lower two bits is lost, right? This needs to be explained as well. Thanks!