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From: Marco Elver <elver@google.com>
To: Daniel Axtens <dja@axtens.net>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Linux Memory Management List <linux-mm@kvack.org>,
	kasan-dev <kasan-dev@googlegroups.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andrey Konovalov <andreyknvl@gmail.com>,
	linuxppc-dev@lists.ozlabs.org,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	aneesh.kumar@linux.ibm.com, Balbir Singh <bsingharora@gmail.com>
Subject: Re: [PATCH v14 3/4] mm: define default MAX_PTRS_PER_* in include/pgtable.h
Date: Thu, 17 Jun 2021 09:08:41 +0200	[thread overview]
Message-ID: <CANpmjNPo1Cn5PNQB0kRWU_481WKUO1WkY-kDYhBTQkT0VXsF0A@mail.gmail.com> (raw)
In-Reply-To: <20210617063956.94061-4-dja@axtens.net>

On Thu, 17 Jun 2021 at 08:40, Daniel Axtens <dja@axtens.net> wrote:
>
> Commit c65e774fb3f6 ("x86/mm: Make PGDIR_SHIFT and PTRS_PER_P4D variable")
> made PTRS_PER_P4D variable on x86 and introduced MAX_PTRS_PER_P4D as a
> constant for cases which need a compile-time constant (e.g. fixed-size
> arrays).
>
> powerpc likewise has boot-time selectable MMU features which can cause
> other mm "constants" to vary. For KASAN, we have some static
> PTE/PMD/PUD/P4D arrays so we need compile-time maximums for all these
> constants. Extend the MAX_PTRS_PER_ idiom, and place default definitions
> in include/pgtable.h. These define MAX_PTRS_PER_x to be PTRS_PER_x unless
> an architecture has defined MAX_PTRS_PER_x in its arch headers.
>
> Clean up pgtable-nop4d.h and s390's MAX_PTRS_PER_P4D definitions while
> we're at it: both can just pick up the default now.
>
> Signed-off-by: Daniel Axtens <dja@axtens.net>

Reviewed-by: Marco Elver <elver@google.com>


> ---
>
> s390 was compile tested only.
> ---
>  arch/s390/include/asm/pgtable.h     |  2 --
>  include/asm-generic/pgtable-nop4d.h |  1 -
>  include/linux/pgtable.h             | 22 ++++++++++++++++++++++
>  3 files changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
> index 7c66ae5d7e32..cf05954ce013 100644
> --- a/arch/s390/include/asm/pgtable.h
> +++ b/arch/s390/include/asm/pgtable.h
> @@ -342,8 +342,6 @@ static inline int is_module_addr(void *addr)
>  #define PTRS_PER_P4D   _CRST_ENTRIES
>  #define PTRS_PER_PGD   _CRST_ENTRIES
>
> -#define MAX_PTRS_PER_P4D       PTRS_PER_P4D
> -
>  /*
>   * Segment table and region3 table entry encoding
>   * (R = read-only, I = invalid, y = young bit):
> diff --git a/include/asm-generic/pgtable-nop4d.h b/include/asm-generic/pgtable-nop4d.h
> index ce2cbb3c380f..2f6b1befb129 100644
> --- a/include/asm-generic/pgtable-nop4d.h
> +++ b/include/asm-generic/pgtable-nop4d.h
> @@ -9,7 +9,6 @@
>  typedef struct { pgd_t pgd; } p4d_t;
>
>  #define P4D_SHIFT              PGDIR_SHIFT
> -#define MAX_PTRS_PER_P4D       1
>  #define PTRS_PER_P4D           1
>  #define P4D_SIZE               (1UL << P4D_SHIFT)
>  #define P4D_MASK               (~(P4D_SIZE-1))
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index 9e6f71265f72..69700e3e615f 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -1625,4 +1625,26 @@ typedef unsigned int pgtbl_mod_mask;
>  #define pte_leaf_size(x) PAGE_SIZE
>  #endif
>
> +/*
> + * Some architectures have MMUs that are configurable or selectable at boot
> + * time. These lead to variable PTRS_PER_x. For statically allocated arrays it
> + * helps to have a static maximum value.
> + */
> +
> +#ifndef MAX_PTRS_PER_PTE
> +#define MAX_PTRS_PER_PTE PTRS_PER_PTE
> +#endif
> +
> +#ifndef MAX_PTRS_PER_PMD
> +#define MAX_PTRS_PER_PMD PTRS_PER_PMD
> +#endif
> +
> +#ifndef MAX_PTRS_PER_PUD
> +#define MAX_PTRS_PER_PUD PTRS_PER_PUD
> +#endif
> +
> +#ifndef MAX_PTRS_PER_P4D
> +#define MAX_PTRS_PER_P4D PTRS_PER_P4D
> +#endif
> +
>  #endif /* _LINUX_PGTABLE_H */
> --
> 2.30.2
>
> --
> You received this message because you are subscribed to the Google Groups "kasan-dev" group.
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> To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20210617063956.94061-4-dja%40axtens.net.

  parent reply	other threads:[~2021-06-17  7:08 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-17  6:39 [PATCH v14 0/4] KASAN core changes for ppc64 radix KASAN Daniel Axtens
2021-06-17  6:39 ` [PATCH v14 1/4] kasan: allow an architecture to disable inline instrumentation Daniel Axtens
2021-06-17  7:06   ` Marco Elver
2021-06-17  6:39 ` [PATCH v14 2/4] kasan: allow architectures to provide an outline readiness check Daniel Axtens
2021-06-17  6:55   ` Christophe Leroy
2021-06-17  6:59   ` Christophe Leroy
2021-06-17  7:06   ` Marco Elver
2021-06-17  6:39 ` [PATCH v14 3/4] mm: define default MAX_PTRS_PER_* in include/pgtable.h Daniel Axtens
2021-06-17  7:00   ` Christophe Leroy
2021-06-17  7:08   ` Marco Elver [this message]
2021-06-17  6:39 ` [PATCH v14 4/4] kasan: use MAX_PTRS_PER_* for early shadow tables Daniel Axtens
2021-06-17  7:09   ` Marco Elver

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