From: Catalin Marinas <catalin.marinas@arm.com>
To: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: linux-arch@vger.kernel.org, Szabolcs Nagy <szabolcs.nagy@arm.com>,
Andrey Konovalov <andreyknvl@google.com>,
Peter Collingbourne <pcc@google.com>,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Will Deacon <will@kernel.org>,
Dave P Martin <Dave.Martin@arm.com>,
linux-arm-kernel@lists.infradead.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)
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 The last sentence is outdated, it should probably say that uaccess is only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
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next prev parent reply other threads:[~2020-08-05 9:25 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200715170844.30064-1-catalin.marinas@arm.com>
[not found] ` <20200715170844.30064-19-catalin.marinas@arm.com>
2020-07-20 15:30 ` [PATCH v7 18/29] arm64: mte: Allow user control of the tag check mode via prctl() 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]
[not found] ` <20200715170844.30064-30-catalin.marinas@arm.com>
2020-07-27 16:36 ` [PATCH v7 29/29] arm64: mte: Add Memory Tagging Extension documentation 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
2020-08-07 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
[not found] ` <20200715170844.30064-23-catalin.marinas@arm.com>
2020-08-13 14:01 ` [PATCH v7 22/29] arm64: mte: ptrace: Add PTRACE_{PEEK,POKE}MTETAGS support Luis Machado
2020-08-22 10:56 ` Catalin Marinas
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