linux-kernel - Re: [PATCH 28/31] kasan: add kasan.vmalloc command line flag

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Message-ID: <CA+fCnZfE-6zwuPySgMH6r4A=j151uBZvFP3wzOKvAD6JNLgLkQ@mail.gmail.com>
Date:   Mon, 6 Dec 2021 22:09:55 +0100
From:   Andrey Konovalov <andreyknvl@...il.com>
To:     Marco Elver <elver@...gle.com>
Cc:     andrey.konovalov@...ux.dev,
        Alexander Potapenko <glider@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Peter Collingbourne <pcc@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Will Deacon <will@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Evgenii Stepanov <eugenis@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [PATCH 28/31] kasan: add kasan.vmalloc command line flag

On Fri, Dec 3, 2021 at 1:09 PM Marco Elver <elver@...gle.com> wrote:
>
> On Tue, Nov 30, 2021 at 11:08PM +0100, andrey.konovalov@...ux.dev wrote:
> [...]
> >  enum kasan_arg_stacktrace {
> >       KASAN_ARG_STACKTRACE_DEFAULT,
> >       KASAN_ARG_STACKTRACE_OFF,
> > @@ -40,6 +46,7 @@ enum kasan_arg_stacktrace {
> >
> >  static enum kasan_arg kasan_arg __ro_after_init;
> >  static enum kasan_arg_mode kasan_arg_mode __ro_after_init;
> > +static enum kasan_arg_vmalloc kasan_arg_vmalloc __ro_after_init;
> >  static enum kasan_arg_stacktrace kasan_arg_stacktrace __ro_after_init;
>
> It just occurred to me that all of these (except kasan_arg_mode) are
> only used by __init functions, so they could actually be marked
> __initdata instead of __ro_after_init to free up some bytes after init.

*Except kasan_arg_mode and kasan_arg. Both are accessed by
kasan_init_hw_tags_cpu(), which is not __init to support hot-plugged
CPUs.

However, kasan_arg_stacktrace and kasan_arg_vmalloc can indeed be
marked as __initdata, will do in v2.

> [...]
> > +     switch (kasan_arg_vmalloc) {
> > +     case KASAN_ARG_VMALLOC_DEFAULT:
> > +             /* Default to enabling vmalloc tagging. */
> > +             static_branch_enable(&kasan_flag_vmalloc);
> > +             break;
> > +     case KASAN_ARG_VMALLOC_OFF:
> > +             /* Do nothing, kasan_flag_vmalloc keeps its default value. */
> > +             break;
> > +     case KASAN_ARG_VMALLOC_ON:
> > +             static_branch_enable(&kasan_flag_vmalloc);
> > +             break;
> > +     }
>
> The KASAN_ARG_STACKTRACE_DEFAULT and KASAN_ARG_VMALLOC_ON cases can be
> combined.

Will do in v2.

Thanks!