From: Mark Rutland <mark.rutland@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Will Deacon <will@kernel.org>,
"Jose E. Marchesi" <jemarch@gnu.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
Ard Biesheuvel <ardb@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
linux-toolchains@vger.kernel.org
Subject: Re: Linux Plumbers Conf 2021
Date: Wed, 19 May 2021 10:32:40 +0100 [thread overview]
Message-ID: <20210519093240.GA2797@C02TD0UTHF1T.local> (raw)
In-Reply-To: <20210518200306.GE21560@worktop.programming.kicks-ass.net>
On Tue, May 18, 2021 at 10:03:06PM +0200, Peter Zijlstra wrote:
> On Tue, May 18, 2021 at 09:57:26AM -0700, Nick Desaulniers wrote:
> > On Tue, May 18, 2021 at 6:23 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> > > - validates noinstr annotation; *HOWEVER* we rely on objtool to NOP
> > > all __sanitizer_cov_* calls in .noinstr/.entry text sections because
> > > __no_sanitize_cov is 'broken' in all known compilers.
> >
> > ^ Do you have more information on this?
>
> Random link in the middle of a relevant thread:
>
> https://lkml.kernel.org/r/CANpmjNPNa2f=kAF6c199oYVJ0iSyirQRGxeOBLxa9PmakSXRbA@mail.gmail.com
>
> Notable quote:
>
> "It's everywhere. We cannot mark noinstr functions to not be
> instrumented by KCOV/-fsanitize-coverage, because no compiler provides
> an attribute to do so. GCC doesn't have
> __attribute__((no_sanitize_coverage)) and Clang doesn't have
> __attribute__((no_sanitize("coverage")), and therefore we can't have
> __no_sanitize_coverage."
Yuck; I wasn't aware of that.
This means that arm64's entry code is unsound (along with some other
parts) if kcov is enabled.
That *really* needs an attribute, and going forward we shouldn't accept
new compiler instrumentation that we can't opt-out of like this.
Thanks,
Mark.
next prev parent reply other threads:[~2021-05-19 9:32 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAKwvOdm-Vb2BGRCmtYCh5JcGkM+XedzSMdNr8kQLbY4y_85EvA@mail.gmail.com>
[not found] ` <20210518121447.GB7914@willie-the-truck>
[not found] ` <20210518124311.r4fwv6lfz3erkqnb@treble>
2021-05-18 12:48 ` Linux Plumbers Conf 2021 Josh Poimboeuf
2021-05-18 13:21 ` Peter Zijlstra
2021-05-18 16:57 ` Nick Desaulniers
2021-05-18 20:03 ` Peter Zijlstra
2021-05-18 20:15 ` Nick Desaulniers
2021-05-19 9:32 ` Mark Rutland [this message]
2021-05-19 10:19 ` Marco Elver
2021-05-19 11:56 ` Mark Rutland
2021-05-19 14:04 ` Marco Elver
2021-05-19 15:02 ` Martin Liška
2021-05-19 15:05 ` Marco Elver
2021-05-20 8:34 ` Martin Liška
2021-06-16 23:01 ` Nick Desaulniers
2021-06-24 20:35 ` Nick Desaulniers
2021-06-24 20:37 ` Nick Desaulniers
2021-06-28 17:59 ` Will Deacon
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