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Date: Wed, 10 Mar 2021 13:03:50 -0800
From: Kees Cook <keescook@...omium.org>
To: Andrey Konovalov <andreyknvl@...gle.com>
Cc: Alexander Potapenko <glider@...gle.com>,
Thomas Gleixner <tglx@...utronix.de>,
Elena Reshetova <elena.reshetova@...el.com>,
the arch/x86 maintainers <x86@...nel.org>,
Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>,
Alexander Popov <alex.popov@...ux.com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Jann Horn <jannh@...gle.com>, kernel-hardening@...ts.openwall.com,
linux-hardening@...r.kernel.org,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
Linux Memory Management List <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>,
Vlastimil Babka <vbabka@...e.cz>,
David Hildenbrand <david@...hat.com>,
Mike Rapoport <rppt@...ux.ibm.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Jonathan Corbet <corbet@....net>,
Randy Dunlap <rdunlap@...radead.org>
Subject: Re: [PATCH v5 3/7] init_on_alloc: Unpessimize default-on builds
On Wed, Mar 10, 2021 at 01:52:04PM +0100, Andrey Konovalov wrote:
> On Tue, Mar 9, 2021 at 10:43 PM Kees Cook <keescook@...omium.org> wrote:
> >
> > Right now, the state of CONFIG_INIT_ON_ALLOC_DEFAULT_ON (and
> > ...ON_FREE...) did not change the assembly ordering of the static branch
> > tests. Use the new jump_label macro to check CONFIG settings to default
> > to the "expected" state, unpessimizes the resulting assembly code.
> >
> > Reviewed-by: Alexander Potapenko <glider@...gle.com>
> > Link: https://lore.kernel.org/lkml/CAG_fn=X0DVwqLaHJTO6Jw7TGcMSm77GKHinrd0m_6y0SzWOrFA@mail.gmail.com/
> > Signed-off-by: Kees Cook <keescook@...omium.org>
> > ---
> > include/linux/mm.h | 6 ++++--
> > 1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index bf341a9bfe46..2ccd856ac0d1 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -2874,7 +2874,8 @@ static inline void kernel_unpoison_pages(struct page *page, int numpages) { }
> > DECLARE_STATIC_KEY_MAYBE(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, init_on_alloc);
> > static inline bool want_init_on_alloc(gfp_t flags)
> > {
> > - if (static_branch_unlikely(&init_on_alloc))
> > + if (static_branch_maybe(CONFIG_INIT_ON_ALLOC_DEFAULT_ON,
> > + &init_on_alloc))
> > return true;
> > return flags & __GFP_ZERO;
> > }
> > @@ -2882,7 +2883,8 @@ static inline bool want_init_on_alloc(gfp_t flags)
> > DECLARE_STATIC_KEY_MAYBE(CONFIG_INIT_ON_FREE_DEFAULT_ON, init_on_free);
> > static inline bool want_init_on_free(void)
> > {
> > - return static_branch_unlikely(&init_on_free);
> > + return static_branch_maybe(CONFIG_INIT_ON_FREE_DEFAULT_ON,
> > + &init_on_free);
> > }
> >
> > extern bool _debug_pagealloc_enabled_early;
>
> Should we also update slab_want_init_on_alloc() and slab_want_init_on_free()?
Whoops! Thank you; I will update and resend. :)
--
Kees Cook
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