linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Mark Rutland <mark.rutland@arm.com>
To: Michal Marek <mmarek@suse.com>
Cc: linux-kernel@vger.kernel.org,
	Alexander Potapenko <glider@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Dmitry Vyukov <dvyukov@google.com>,
	James Morse <james.morse@arm.com>,
	Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH] kcov: reject open when kernel not instrumented
Date: Wed, 15 Jun 2016 17:34:50 +0100	[thread overview]
Message-ID: <20160615163449.GA15332@leverpostej> (raw)
In-Reply-To: <5761806F.5020103@suse.com>

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?

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.

  reply	other threads:[~2016-06-15 16:35 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-15 15:49 [PATCH] kcov: reject open when kernel not instrumented Mark Rutland
2016-06-15 15:52 ` Dmitry Vyukov
2016-06-15 16:21 ` Michal Marek
2016-06-15 16:34   ` Mark Rutland [this message]
2016-06-15 16:36     ` Dmitry Vyukov

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20160615163449.GA15332@leverpostej \
    --to=mark.rutland@arm.com \
    --cc=akpm@linux-foundation.org \
    --cc=dvyukov@google.com \
    --cc=glider@google.com \
    --cc=james.morse@arm.com \
    --cc=keescook@chromium.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mmarek@suse.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).