From: Catalin Marinas <catalin.marinas@arm.com>
To: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Andrey Konovalov <andreyknvl@google.com>,
Dmitry Vyukov <dvyukov@google.com>,
kasan-dev@googlegroups.com,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Alexander Potapenko <glider@google.com>,
Marco Elver <elver@google.com>,
Evgenii Stepanov <eugenis@google.com>,
Elena Petrova <lenaptr@google.com>,
Branislav Rankov <Branislav.Rankov@arm.com>,
Kevin Brodsky <kevin.brodsky@arm.com>,
Will Deacon <will.deacon@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 29/39] arm64: mte: Switch GCR_EL1 in kernel entry and exit
Date: Fri, 9 Oct 2020 11:16:43 +0100 [thread overview]
Message-ID: <20201009101643.GG23638@gaia> (raw)
In-Reply-To: <106f8670-3dd0-70ad-91ac-4f419585df50@arm.com>
On Fri, Oct 09, 2020 at 10:56:02AM +0100, Vincenzo Frascino wrote:
> On 10/9/20 9:11 AM, Catalin Marinas wrote:
> > On Thu, Oct 08, 2020 at 07:24:12PM +0100, Vincenzo Frascino wrote:
> >> On 10/2/20 3:06 PM, Catalin Marinas wrote:
> >>> On Fri, Oct 02, 2020 at 01:10:30AM +0200, Andrey Konovalov wrote:
> >>>> diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
> >>>> index 7c67ac6f08df..d1847f29f59b 100644
> >>>> --- a/arch/arm64/kernel/mte.c
> >>>> +++ b/arch/arm64/kernel/mte.c
> >>>> @@ -23,6 +23,8 @@
> >>>> #include <asm/ptrace.h>
> >>>> #include <asm/sysreg.h>
> >>>>
> >>>> +u64 gcr_kernel_excl __ro_after_init;
> >>>> +
> >>>> static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap)
> >>>> {
> >>>> pte_t old_pte = READ_ONCE(*ptep);
> >>>> @@ -120,6 +122,13 @@ void *mte_set_mem_tag_range(void *addr, size_t size, u8 tag)
> >>>> return ptr;
> >>>> }
> >>>>
> >>>> +void mte_init_tags(u64 max_tag)
> >>>> +{
> >>>> + u64 incl = GENMASK(max_tag & MTE_TAG_MAX, 0);
> >>>
> >>> Nitpick: it's not obvious that MTE_TAG_MAX is a mask, so better write
> >>> this as GENMASK(min(max_tag, MTE_TAG_MAX), 0).
> >>
> >> The two things do not seem equivalent because the format of the tags in KASAN is
> >> 0xFF and in MTE is 0xF, hence if extract the minimum whatever is the tag passed
> >> by KASAN it will always be MTE_TAG_MAX.
> >>
> >> To make it cleaner I propose: GENMASK(FIELD_GET(MTE_TAG_MAX, max_tag), 0);
> >
> > I don't think that's any clearer since FIELD_GET still assumes that
> > MTE_TAG_MAX is a mask. I think it's better to add a comment on why this
> > is needed, as you explained above that the KASAN tags go to 0xff.
> >
> > If you want to get rid of MTE_TAG_MAX altogether, just do a
> >
> > max_tag &= (1 << MAX_TAG_SIZE) - 1;
> >
> > before setting incl (a comment is still useful).
> >
>
> Agree, but still think we should use FIELD_GET here since it is common language
> in the kernel.
>
> How about we get rid of MTE_TAG_MAX and we do something like:
>
> GENMASK(FIELD_GET(MTE_TAG_MASK >> MTE_TAG_SHIFT, max_tag), 0);
It works for me and you can drop the MTE_TAG_MAX definition (I think
it's only used here).
--
Catalin
WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com>
To: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
Marco Elver <elver@google.com>,
Elena Petrova <lenaptr@google.com>,
Andrey Konovalov <andreyknvl@google.com>,
Kevin Brodsky <kevin.brodsky@arm.com>,
Will Deacon <will.deacon@arm.com>,
Branislav Rankov <Branislav.Rankov@arm.com>,
kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, Alexander Potapenko <glider@google.com>,
Evgenii Stepanov <eugenis@google.com>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Andrew Morton <akpm@linux-foundation.org>,
Dmitry Vyukov <dvyukov@google.com>
Subject: Re: [PATCH v4 29/39] arm64: mte: Switch GCR_EL1 in kernel entry and exit
Date: Fri, 9 Oct 2020 11:16:43 +0100 [thread overview]
Message-ID: <20201009101643.GG23638@gaia> (raw)
In-Reply-To: <106f8670-3dd0-70ad-91ac-4f419585df50@arm.com>
On Fri, Oct 09, 2020 at 10:56:02AM +0100, Vincenzo Frascino wrote:
> On 10/9/20 9:11 AM, Catalin Marinas wrote:
> > On Thu, Oct 08, 2020 at 07:24:12PM +0100, Vincenzo Frascino wrote:
> >> On 10/2/20 3:06 PM, Catalin Marinas wrote:
> >>> On Fri, Oct 02, 2020 at 01:10:30AM +0200, Andrey Konovalov wrote:
> >>>> diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
> >>>> index 7c67ac6f08df..d1847f29f59b 100644
> >>>> --- a/arch/arm64/kernel/mte.c
> >>>> +++ b/arch/arm64/kernel/mte.c
> >>>> @@ -23,6 +23,8 @@
> >>>> #include <asm/ptrace.h>
> >>>> #include <asm/sysreg.h>
> >>>>
> >>>> +u64 gcr_kernel_excl __ro_after_init;
> >>>> +
> >>>> static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap)
> >>>> {
> >>>> pte_t old_pte = READ_ONCE(*ptep);
> >>>> @@ -120,6 +122,13 @@ void *mte_set_mem_tag_range(void *addr, size_t size, u8 tag)
> >>>> return ptr;
> >>>> }
> >>>>
> >>>> +void mte_init_tags(u64 max_tag)
> >>>> +{
> >>>> + u64 incl = GENMASK(max_tag & MTE_TAG_MAX, 0);
> >>>
> >>> Nitpick: it's not obvious that MTE_TAG_MAX is a mask, so better write
> >>> this as GENMASK(min(max_tag, MTE_TAG_MAX), 0).
> >>
> >> The two things do not seem equivalent because the format of the tags in KASAN is
> >> 0xFF and in MTE is 0xF, hence if extract the minimum whatever is the tag passed
> >> by KASAN it will always be MTE_TAG_MAX.
> >>
> >> To make it cleaner I propose: GENMASK(FIELD_GET(MTE_TAG_MAX, max_tag), 0);
> >
> > I don't think that's any clearer since FIELD_GET still assumes that
> > MTE_TAG_MAX is a mask. I think it's better to add a comment on why this
> > is needed, as you explained above that the KASAN tags go to 0xff.
> >
> > If you want to get rid of MTE_TAG_MAX altogether, just do a
> >
> > max_tag &= (1 << MAX_TAG_SIZE) - 1;
> >
> > before setting incl (a comment is still useful).
> >
>
> Agree, but still think we should use FIELD_GET here since it is common language
> in the kernel.
>
> How about we get rid of MTE_TAG_MAX and we do something like:
>
> GENMASK(FIELD_GET(MTE_TAG_MASK >> MTE_TAG_SHIFT, max_tag), 0);
It works for me and you can drop the MTE_TAG_MAX definition (I think
it's only used here).
--
Catalin
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next prev parent reply other threads:[~2020-10-09 10:16 UTC|newest]
Thread overview: 138+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-01 23:10 [PATCH v4 00/39] kasan: add hardware tag-based mode for arm64 Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 01/39] kasan: drop unnecessary GPL text from comment headers Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 02/39] kasan: KASAN_VMALLOC depends on KASAN_GENERIC Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 03/39] kasan: group vmalloc code Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 04/39] kasan: shadow declarations only for software modes Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 05/39] kasan: rename (un)poison_shadow to (un)poison_memory Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 06/39] kasan: rename KASAN_SHADOW_* to KASAN_GRANULE_* Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 07/39] kasan: only build init.c for software modes Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 08/39] kasan: split out shadow.c from common.c Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 09/39] kasan: define KASAN_GRANULE_PAGE Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 10/39] kasan: rename report and tags files Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 11/39] kasan: don't duplicate config dependencies Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 12/39] kasan: hide invalid free check implementation Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 13/39] kasan: decode stack frame only with KASAN_STACK_ENABLE Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 14/39] kasan, arm64: only init shadow for software modes Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 15/39] kasan, arm64: only use kasan_depth " Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 16/39] kasan: rename addr_has_shadow to addr_has_metadata Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 17/39] kasan: rename print_shadow_for_address to print_memory_metadata Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 18/39] kasan: kasan_non_canonical_hook only for software modes Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 19/39] kasan: rename SHADOW layout macros to META Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 20/39] kasan: separate metadata_fetch_row for each mode Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 21/39] kasan, arm64: don't allow SW_TAGS with ARM64_MTE Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 22/39] kasan: introduce CONFIG_KASAN_HW_TAGS Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 23/39] arm64: Enable armv8.5-a asm-arch option Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 24/39] arm64: mte: Add in-kernel MTE helpers Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-02 13:51 ` Catalin Marinas
2020-10-02 13:51 ` Catalin Marinas
2020-10-01 23:10 ` [PATCH v4 25/39] arm64: kasan: Add arch layer for memory tagging helpers Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 26/39] arm64: mte: Add in-kernel tag fault handler Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 27/39] arm64: kasan: Enable in-kernel MTE Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-02 14:00 ` Catalin Marinas
2020-10-02 14:00 ` Catalin Marinas
2020-10-01 23:10 ` [PATCH v4 28/39] arm64: mte: Convert gcr_user into an exclude mask Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 29/39] arm64: mte: Switch GCR_EL1 in kernel entry and exit Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-02 14:06 ` Catalin Marinas
2020-10-02 14:06 ` Catalin Marinas
2020-10-08 18:24 ` Vincenzo Frascino
2020-10-08 18:24 ` Vincenzo Frascino
2020-10-09 8:11 ` Catalin Marinas
2020-10-09 8:11 ` Catalin Marinas
2020-10-09 9:56 ` Vincenzo Frascino
2020-10-09 9:56 ` Vincenzo Frascino
2020-10-09 10:16 ` Catalin Marinas [this message]
2020-10-09 10:16 ` Catalin Marinas
2020-10-09 10:21 ` Vincenzo Frascino
2020-10-09 10:21 ` Vincenzo Frascino
2020-10-01 23:10 ` [PATCH v4 30/39] arm64: kasan: Enable TBI EL1 Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-02 14:10 ` Catalin Marinas
2020-10-02 14:10 ` Catalin Marinas
2020-10-01 23:10 ` [PATCH v4 31/39] arm64: kasan: Align allocations for HW_TAGS Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 32/39] kasan: define KASAN_GRANULE_SIZE " Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 33/39] kasan, x86, s390: update undef CONFIG_KASAN Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 34/39] kasan, arm64: expand CONFIG_KASAN checks Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 35/39] kasan, arm64: implement HW_TAGS runtime Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 36/39] kasan, arm64: print report from tag fault handler Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 37/39] kasan, mm: reset tags when accessing metadata Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 38/39] kasan, arm64: enable CONFIG_KASAN_HW_TAGS Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` [PATCH v4 39/39] kasan: add documentation for hardware tag-based mode Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
2020-10-01 23:10 ` Andrey Konovalov
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