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From: Catalin Marinas <catalin.marinas@arm.com>
To: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
	linux-arch@vger.kernel.org, Will Deacon <will@kernel.org>,
	Dave P Martin <Dave.Martin@arm.com>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Szabolcs Nagy <szabolcs.nagy@arm.com>,
	Andrey Konovalov <andreyknvl@google.com>,
	Peter Collingbourne <pcc@google.com>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v7 18/29] arm64: mte: Allow user control of the tag check mode via prctl()
Date: Wed, 5 Aug 2020 10:24:18 +0100	[thread overview]
Message-ID: <20200805092418.GB13391@gaia> (raw)
Message-ID: <20200805092418.lMbP8tmEwT7Kck6WA5LhPaSUHrs_m2Lnyn95jCt-q7Q@z> (raw)
In-Reply-To: <9342a080-9450-c01a-54a0-9ddebfe45613@arm.com>

On Tue, Aug 04, 2020 at 08:34:42PM +0100, Kevin Brodsky wrote:
> On 15/07/2020 18:08, Catalin Marinas wrote:
> > By default, even if PROT_MTE is set on a memory range, there is no tag
> > check fault reporting (SIGSEGV). Introduce a set of option to the
> > exiting prctl(PR_SET_TAGGED_ADDR_CTRL) to allow user control of the tag
> > check fault mode:
> > 
> >    PR_MTE_TCF_NONE  - no reporting (default)
> >    PR_MTE_TCF_SYNC  - synchronous tag check fault reporting
> >    PR_MTE_TCF_ASYNC - asynchronous tag check fault reporting
> > 
> > These options translate into the corresponding SCTLR_EL1.TCF0 bitfield,
> > context-switched by the kernel. Note that uaccess done by the kernel is
> > not checked and cannot be configured by the user.
> 
> The last sentence is outdated, it should probably say that uaccess is only
> checked in in synchronous mode.

Thanks, I forgot about the commit log. The documentation was updated to:

**Note**: Kernel accesses to the user address space (e.g. ``read()``
system call) are not checked if the user thread tag checking mode is
``PR_MTE_TCF_NONE`` or ``PR_MTE_TCF_ASYNC``. If the tag checking mode is
``PR_MTE_TCF_SYNC``, the kernel makes a best effort to check its user
address accesses, however it cannot always guarantee it.

-- 
Catalin

  reply	other threads:[~2020-08-05  9:24 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-15 17:08 [PATCH v7 00/26] arm64: Memory Tagging Extension user-space support Catalin Marinas
2020-07-15 17:08 ` Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 01/29] arm64: mte: system register definitions Catalin Marinas
2020-07-15 17:08   ` Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 02/29] arm64: mte: CPU feature detection and initial sysreg configuration Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 03/29] arm64: mte: Use Normal Tagged attributes for the linear map Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 04/29] arm64: mte: Add specific SIGSEGV codes Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 05/29] arm64: mte: Handle synchronous and asynchronous tag check faults Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 06/29] mm: Add PG_arch_2 page flag Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 07/29] mm: Preserve the PG_arch_2 flag in __split_huge_page_tail() Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 08/29] arm64: mte: Clear the tags when a page is mapped in user-space with PROT_MTE Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 09/29] arm64: mte: Tags-aware copy_{user_,}highpage() implementations Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 10/29] arm64: Avoid unnecessary clear_user_page() indirection Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 11/29] arm64: mte: Tags-aware aware memcmp_pages() implementation Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 12/29] arm64: mte: Handle the MAIR_EL1 changes for late CPU bring-up Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 13/29] mm: Introduce arch_calc_vm_flag_bits() Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 14/29] arm64: mte: Add PROT_MTE support to mmap() and mprotect() Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 15/29] mm: Introduce arch_validate_flags() Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 16/29] arm64: mte: Validate the PROT_MTE request via arch_validate_flags() Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 17/29] mm: Allow arm64 mmap(PROT_MTE) on RAM-based files Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 18/29] arm64: mte: Allow user control of the tag check mode via prctl() Catalin Marinas
2020-07-20 15:30   ` Kevin Brodsky
2020-07-20 17:00     ` Dave Martin
2020-07-22 10:28       ` Catalin Marinas
2020-07-23 19:33       ` Kevin Brodsky
2020-07-22 11:09     ` Catalin Marinas
2020-08-04 19:34   ` Kevin Brodsky
2020-08-05  9:24     ` Catalin Marinas [this message]
2020-08-05  9:24       ` Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 19/29] arm64: mte: Allow user control of the generated random tags " Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 20/29] arm64: mte: Restore the GCR_EL1 register after a suspend Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 21/29] arm64: mte: Allow {set,get}_tagged_addr_ctrl() on non-current tasks Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 22/29] arm64: mte: ptrace: Add PTRACE_{PEEK,POKE}MTETAGS support Catalin Marinas
2020-08-13 14:01   ` Luis Machado
2020-08-22 10:56     ` Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 23/29] arm64: mte: ptrace: Add NT_ARM_TAGGED_ADDR_CTRL regset Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 24/29] fs: Handle intra-page faults in copy_mount_options() Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 25/29] mm: Add arch hooks for saving/restoring tags Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 26/29] arm64: mte: Enable swap of tagged pages Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 27/29] arm64: mte: Save tags when hibernating Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 28/29] arm64: mte: Kconfig entry Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 29/29] arm64: mte: Add Memory Tagging Extension documentation Catalin Marinas
2020-07-27 16:36   ` Szabolcs Nagy
2020-07-28 11:08     ` Dave Martin
2020-07-28 14:53       ` Szabolcs Nagy
2020-07-28 19:59         ` Catalin Marinas
2020-08-03 12:43           ` Szabolcs Nagy
2020-08-03 12:43             ` Szabolcs Nagy
2020-08-07 15:19             ` Catalin Marinas
2020-08-07 15:19               ` Catalin Marinas
2020-08-10 14:13               ` Szabolcs Nagy
2020-08-11 17:20                 ` Catalin Marinas
2020-08-12 12:45                   ` Szabolcs Nagy
2020-08-19  9:54                     ` Catalin Marinas
2020-08-20 16:43                       ` Szabolcs Nagy
2020-08-20 17:27                         ` Paul Eggert
2020-08-22 11:31                           ` Catalin Marinas
2020-08-22 11:28                         ` Catalin Marinas

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