linux-kernel - Re: [PATCH -tip v3 1/2] kcov: Make runtime functions noinstr-compatible

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Message-ID: <20200615145448.GV2531@hirez.programming.kicks-ass.net>
Date:   Mon, 15 Jun 2020 16:54:48 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Marco Elver <elver@...gle.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Alexander Potapenko <glider@...gle.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        LKML <linux-kernel@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH -tip v3 1/2] kcov: Make runtime functions
 noinstr-compatible

On Mon, Jun 15, 2020 at 09:53:06AM +0200, Marco Elver wrote:

> For KCSAN the crash still happens in check_preemption_disabled, in the
> inlined native_save_fl function (apparently on its 'pushf'). If I turn
> fixup_bad_iret's __this_cpu_read into a raw_cpu_read (to bypass
> check_preemption_disabled), no more crash with KCSAN.

Yeah, I can't see anything weird there with KCSAN + KCOV + NOP :-(