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From: Marco Elver <elver@google.com>
To: Sven Schnelle <svens@linux.ibm.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	kasan-dev <kasan-dev@googlegroups.com>,
	Alexander Potapenko <glider@google.com>
Subject: Re: [PATCH 1/2] kfence: add function to mask address bits
Date: Fri, 14 May 2021 13:23:33 +0200	[thread overview]
Message-ID: <CANpmjNPAS5kDsADb-DwvdFR9nRnX47-mFuEG2vmMPn5U3i3sGQ@mail.gmail.com> (raw)
In-Reply-To: <yt9dfsypinlk.fsf@linux.ibm.com>

On Fri, 14 May 2021 at 13:03, Sven Schnelle <svens@linux.ibm.com> wrote:
>
> Marco Elver <elver@google.com> writes:
>
> >> diff --git a/mm/kfence/core.c b/mm/kfence/core.c
> >> index e18fbbd5d9b4..bc15e3cb71d5 100644
> >> --- a/mm/kfence/core.c
> >> +++ b/mm/kfence/core.c
> >> @@ -50,6 +50,11 @@ static unsigned long kfence_sample_interval __read_mostly = CONFIG_KFENCE_SAMPLE
> >>  #endif
> >>  #define MODULE_PARAM_PREFIX "kfence."
> >>
> >> +unsigned long __weak kfence_arch_mask_addr(unsigned long addr)
> >> +{
> >> +       return addr;
> >> +}
> >
> > I don't think this belongs here, because it's test-specific,
> > furthermore if possible we'd like to put all arch-specific code into
> > <asm/kfence.h> (whether or not your arch will have 'static inline'
> > functions only, like x86 and arm64, or not is up to you).
> >
> > Because I don't see this function being terribly complex, also let's
> > just make it a macro.
> >
> > Then in kfence_test.c, we can have:
> >
> > #ifndef kfence_test_mask_address
> > #define kfence_test_mask_address(addr) (addr)
> > #endif
> >
> > and then have it include <asm/kfence.h>. And in your <asm/kfence.h>
> > you can simply say:
> >
> > #define kfence_test_mask_address(addr) (.........)
> >
> > It also avoids having to export kfence_test_mask_address, because
> > kfence_test can be built as a module.
>
> Ok, i'll change my patch accordingly. Thanks!

Sounds good. Also please add a brief comment on top of the
"kfence_test_mask_address" part in kfence_test, like "/* May be
overridden by <asm/kfence.h>. */" -- we have something similar in
mm/kfence/report.c. Also, I think we want to call the macro
"arch_kfence_test_address" -- the "mask" part is very much
arch-dependent, and might not even be a mask on some other weird
hypothetical architecture.

Thanks,
-- Marco

  reply	other threads:[~2021-05-14 11:23 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-14  9:21 [RFC] minor kfence patches Sven Schnelle
2021-05-14  9:21 ` [PATCH 1/2] kfence: add function to mask address bits Sven Schnelle
2021-05-14 10:54   ` Marco Elver
2021-05-14 11:03     ` Sven Schnelle
2021-05-14 11:23       ` Marco Elver [this message]
2021-05-14  9:21 ` [PATCH 2/2] kfence: only handle kernel mode faults Sven Schnelle
2021-05-14 10:52   ` Marco Elver
2021-05-14 10:55     ` Sven Schnelle
2021-05-14 10:59       ` Marco Elver
2021-05-14 10:56 ` [RFC] minor kfence patches Marco Elver

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