From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753373AbcFOQgb (ORCPT ); Wed, 15 Jun 2016 12:36:31 -0400 Received: from mail-lf0-f54.google.com ([209.85.215.54]:35092 "EHLO mail-lf0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752096AbcFOQga (ORCPT ); Wed, 15 Jun 2016 12:36:30 -0400 MIME-Version: 1.0 In-Reply-To: <20160615163449.GA15332@leverpostej> References: <1466005756-15626-1-git-send-email-mark.rutland@arm.com> <5761806F.5020103@suse.com> <20160615163449.GA15332@leverpostej> From: Dmitry Vyukov Date: Wed, 15 Jun 2016 18:36:09 +0200 Message-ID: Subject: Re: [PATCH] kcov: reject open when kernel not instrumented To: Mark Rutland Cc: Michal Marek , LKML , Alexander Potapenko , Andrew Morton , James Morse , Kees Cook Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 15, 2016 at 6:34 PM, Mark Rutland wrote: > On Wed, Jun 15, 2016 at 06:21:03PM +0200, Michal Marek wrote: >> Dne 15.6.2016 v 17:49 Mark Rutland napsal(a): >> > If the toolchain does not support -fsanitize-coverage=trace-pc, we blat >> > this option from CFLAGS_KCOV, and build the kernel without >> > instrumentation, even if CONFIG_KCOV was selected. However, we still >> > build the rest of the kcov infrastructure, and expose a kcov file under >> > debugfs. This can be confusing, as the kernel will appear to support >> > kcov, yet will never manage to sample any trace PC values. While we do >> > note this fact at build time, this may be missed, and a user may not >> > have access to build logs. >> > >> > This patch adds an artificial CONFIG symbol, CONFIG_KCOV_CC, that is >> > only set when the toolchain supports -fsanitize-coverage=trace-pc, and >> > hence the kernel is built with instrumentation. When this is not the >> > case, the kernel will return -ENOTSUPP if userspace attempts to open the >> > kcov debugfs file, indicating that kcov functionality is unavailable. >> >> Hi Mark, >> >> please use a define outside the CONFIG_ namespace, because it is not a >> config option that one can find in .config or a Kconfig file. We already >> have CC_HAVE_ASM_GOTO, CC_USING_FENTRY and similar in the kernel. > > Sure thing. I guess I should also not use IS_ENABLED, and will fall back > to the usual ifdefferty. > > Dmitry, Alexander, any preference for the name? Is > CC_HAVE_SANCOV_TRACE_PC ok? Fine with me. > I guess we should also clean up arm64's current use of CONFIG_AS_LSE > (which I guess should be something like AS_HAVE_LSE per the > CC_HAVE_ASM_GOTO example). I can cook up a patch for that too. > > Thanks, > Mark.