From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Nicholas Piggin <npiggin@gmail.com>,
"alex@ghiti.fr" <alex@ghiti.fr>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Paul Mackerras <paulus@samba.org>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 09/10] powerpc/mm: Convert to default topdown mmap layout
Date: Thu, 16 Dec 2021 14:27:53 +0000 [thread overview]
Message-ID: <442b2b4c-7d6b-65be-0f0a-e72f76369547@csgroup.eu> (raw)
In-Reply-To: <1639044621.jeow25j0pr.astroid@bobo.none>
Le 09/12/2021 à 11:15, Nicholas Piggin a écrit :
> Excerpts from Christophe Leroy's message of December 9, 2021 3:18 am:
>> Select CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT and
>> remove arch/powerpc/mm/mmap.c
>>
>> This change provides standard randomisation of mmaps.
>>
>> See commit 8b8addf891de ("x86/mm/32: Enable full randomization on i386
>> and X86_32") for all the benefits of mmap randomisation.
>
> The justification seems pretty reasonable.
>
>>
>> Comparison between powerpc implementation and the generic one:
>> - mmap_is_legacy() is identical.
>> - arch_mmap_rnd() does exactly the same allthough it's written
>> slightly differently.
>> - MIN_GAP and MAX_GAP are identical.
>> - mmap_base() does the same but uses STACK_RND_MASK which provides
>> the same values as stack_maxrandom_size().
>> - arch_pick_mmap_layout() is almost identical. The only difference
>> is that it also adds the random factor to mm->mmap_base in legacy mode.
>>
>> That last point is what provides the standard randomisation of mmaps.
>
> Thanks for describing it. Could you add random_factor to mmap_base for
> the legacy path for powerpc as a 2-line change that adds the legacy
> randomisation. And then this bigger patch would be closer to a no-op.
>
Ok, in v5 I added that change in patch 10 then switched this patch with
that patch.
Christophe
next prev parent reply other threads:[~2021-12-16 14:28 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-08 17:18 [PATCH v4 00/10] Convert powerpc to default topdown mmap layout Christophe Leroy
2021-12-08 17:18 ` [PATCH v4 01/10] mm: Allow arch specific arch_randomize_brk() with CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT Christophe Leroy
2021-12-08 17:18 ` [PATCH v4 02/10] mm, hugetlbfs: Allow an arch to always use generic versions of get_unmapped_area functions Christophe Leroy
2021-12-09 9:40 ` Nicholas Piggin
2021-12-08 17:18 ` [PATCH v4 03/10] powerpc/mm: Move vma_mmu_pagesize() Christophe Leroy
2021-12-09 9:36 ` Nicholas Piggin
2021-12-08 17:18 ` [PATCH v4 05/10] powerpc/mm: Remove CONFIG_PPC_MM_SLICES Christophe Leroy
2021-12-08 17:18 ` [PATCH v4 04/10] powerpc/mm: Make slice specific to book3s/64 Christophe Leroy
2021-12-08 17:18 ` [PATCH v4 06/10] powerpc/mm: Use generic_get_unmapped_area() and call it from arch_get_unmapped_area() Christophe Leroy
2021-12-09 9:50 ` Nicholas Piggin
2021-12-10 17:47 ` Christophe Leroy
2021-12-16 14:25 ` Christophe Leroy
2021-12-13 13:02 ` Michael Ellerman
2021-12-08 17:18 ` [PATCH v4 08/10] powerpc/mm: Move get_unmapped_area functions to slice.c Christophe Leroy
2021-12-08 17:18 ` [PATCH v4 07/10] powerpc/mm: Use generic_hugetlb_get_unmapped_area() Christophe Leroy
2021-12-09 10:02 ` Nicholas Piggin
2021-12-16 17:13 ` Christophe Leroy
2021-12-16 18:55 ` Catalin Marinas
2021-12-08 17:18 ` [PATCH v4 09/10] powerpc/mm: Convert to default topdown mmap layout Christophe Leroy
2021-12-09 10:15 ` Nicholas Piggin
2021-12-09 10:22 ` Christophe Leroy
2021-12-09 10:43 ` Nicholas Piggin
2021-12-09 11:22 ` Michael Ellerman
2021-12-09 11:32 ` Christophe Leroy
2021-12-09 23:56 ` Michael Ellerman
2021-12-16 14:27 ` Christophe Leroy [this message]
2021-12-08 17:18 ` [PATCH v4 10/10] powerpc/mm: Properly randomise mmap with slices Christophe Leroy
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