From: Catalin Marinas <catalin.marinas@arm.com>
To: Steven Price <steven.price@arm.com>
Cc: linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org,
Richard Earnshaw <Richard.Earnshaw@arm.com>,
Szabolcs Nagy <szabolcs.nagy@arm.com>,
Andrey Konovalov <andreyknvl@google.com>,
Kevin Brodsky <kevin.brodsky@arm.com>,
Peter Collingbourne <pcc@google.com>,
linux-mm@kvack.org, Vincenzo Frascino <vincenzo.frascino@arm.com>,
Will Deacon <will@kernel.org>
Subject: Re: [PATCH v2 04/19] arm64: mte: Use Normal Tagged attributes for the linear map
Date: Thu, 5 Mar 2020 16:38:10 +0000 [thread overview]
Message-ID: <20200305163810.GC1729062@arrakis.emea.arm.com> (raw)
In-Reply-To: <946fcd05-ba8f-90ec-d30b-458b327df59c@arm.com>
On Thu, Mar 05, 2020 at 04:21:34PM +0000, Steven Price wrote:
> On 26/02/2020 18:05, Catalin Marinas wrote:
> > + if (system_supports_mte()) {
> > + /*
> > + * Changing the memory type between Normal and Normal-Tagged
> > + * is safe since Tagged is considered a permission attribute
> > + * from the mismatched attribute aliases perspective.
> > + */
> > + if ((old & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL) ||
> > + (old & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL_TAGGED) ||
> > + (new & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL) ||
> > + (new & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL_TAGGED))
> > + mask |= PTE_ATTRINDX_MASK;
> > + }
> > +
> > return ((old ^ new) & ~mask) == 0;
> > }
>
> This is much more permissive than I would expect. If either the old or
> new memory type is NORMAL (or NORMAL_TAGGED) then the memory type is
> ignored altogether.
>
> Should this check be:
>
> if (((old & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL) ||
> (old & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL_TAGGED)) &&
> ((new & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL) ||
> (new & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL_TAGGED)))
You are right, I think my patch allows many other memory type
combinations. Thanks.
--
Catalin
next prev parent reply other threads:[~2020-03-05 16:38 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-26 18:05 [PATCH v2 00/19] arm64: Memory Tagging Extension user-space support Catalin Marinas
2020-02-26 18:05 ` [PATCH v2 01/19] arm64: alternative: Allow alternative_insn to always issue the first instruction Catalin Marinas
2020-02-26 18:05 ` [PATCH v2 02/19] arm64: mte: system register definitions Catalin Marinas
2020-02-26 18:05 ` [PATCH v2 03/19] arm64: mte: CPU feature detection and initial sysreg configuration Catalin Marinas
2020-02-26 18:05 ` [PATCH v2 04/19] arm64: mte: Use Normal Tagged attributes for the linear map Catalin Marinas
2020-03-05 16:21 ` Steven Price
2020-03-05 16:38 ` Catalin Marinas [this message]
2020-02-26 18:05 ` [PATCH v2 05/19] arm64: mte: Assembler macros and default architecture for .S files Catalin Marinas
2020-02-26 18:05 ` [PATCH v2 06/19] arm64: mte: Tags-aware clear_page() implementation Catalin Marinas
2020-02-26 18:05 ` [PATCH v2 07/19] arm64: mte: Tags-aware copy_page() implementation Catalin Marinas
2020-02-26 18:05 ` [PATCH v2 08/19] arm64: Tags-aware memcmp_pages() implementation Catalin Marinas
2020-02-26 18:05 ` [PATCH v2 09/19] arm64: mte: Add specific SIGSEGV codes Catalin Marinas
2020-02-26 19:05 ` Eric W. Biederman
2020-02-26 19:26 ` Catalin Marinas
2020-02-26 22:33 ` kbuild test robot
2020-02-27 11:05 ` Catalin Marinas
2020-02-27 15:20 ` Eric W. Biederman
2020-02-26 18:05 ` [PATCH v2 10/19] arm64: mte: Handle synchronous and asynchronous tag check faults Catalin Marinas
2020-02-27 11:50 ` Catalin Marinas
2020-02-26 18:05 ` [PATCH v2 11/19] mm: Introduce arch_calc_vm_flag_bits() Catalin Marinas
2020-02-26 18:05 ` [PATCH v2 12/19] arm64: mte: Add PROT_MTE support to mmap() and mprotect() Catalin Marinas
2020-02-26 18:05 ` [PATCH v2 13/19] mm: Introduce arch_validate_flags() Catalin Marinas
2020-02-26 18:05 ` [PATCH v2 14/19] arm64: mte: Validate the PROT_MTE request via arch_validate_flags() Catalin Marinas
2020-02-26 18:05 ` [PATCH v2 15/19] mm: Allow arm64 mmap(PROT_MTE) on RAM-based files Catalin Marinas
2020-02-26 18:05 ` [PATCH v2 16/19] arm64: mte: Allow user control of the tag check mode via prctl() Catalin Marinas
2020-03-09 13:53 ` Kevin Brodsky
2020-02-26 18:05 ` [PATCH v2 17/19] arm64: mte: Allow user control of the generated random tags " Catalin Marinas
2020-02-26 18:05 ` [PATCH v2 18/19] arm64: mte: Kconfig entry Catalin Marinas
2020-02-26 18:05 ` [PATCH v2 19/19] arm64: mte: Add Memory Tagging Extension documentation Catalin Marinas
2020-03-09 14:30 ` Kevin Brodsky
2020-03-11 22:17 ` Richard Henderson
2020-03-12 9:50 ` Catalin Marinas
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