linux-kernel - Re: [PATCH 0/4] arm64: ARMv8.5-A: MTE: Add async mode support

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Date:   Wed, 6 Jan 2021 16:42:26 +0000
From:   Will Deacon <will@...nel.org>
To:     Vincenzo Frascino <vincenzo.frascino@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [PATCH 0/4] arm64: ARMv8.5-A: MTE: Add async mode support

On Wed, Jan 06, 2021 at 04:35:29PM +0000, Vincenzo Frascino wrote:
> 
> On 1/6/21 11:55 AM, Vincenzo Frascino wrote:
> > This patchset implements the asynchronous mode support for ARMv8.5-A
> > Memory Tagging Extension (MTE), which is a debugging feature that allows
> > to detect with the help of the architecture the C and C++ programmatic
> > memory errors like buffer overflow, use-after-free, use-after-return, etc.
> > 
> > MTE is built on top of the AArch64 v8.0 virtual address tagging TBI
> > (Top Byte Ignore) feature and allows a task to set a 4 bit tag on any
> > subset of its address space that is multiple of a 16 bytes granule. MTE
> > is based on a lock-key mechanism where the lock is the tag associated to
> > the physical memory and the key is the tag associated to the virtual
> > address.
> > When MTE is enabled and tags are set for ranges of address space of a task,
> > the PE will compare the tag related to the physical memory with the tag
> > related to the virtual address (tag check operation). Access to the memory
> > is granted only if the two tags match. In case of mismatch the PE will raise
> > an exception.
> > 
> > The exception can be handled synchronously or asynchronously. When the
> > asynchronous mode is enabled:
> >   - Upon fault the PE updates the TFSR_EL1 register.
> >   - The kernel detects the change during one of the following:
> >     - Context switching
> >     - Return to user/EL0
> >     - Kernel entry from EL1
> >     - Kernel exit to EL1
> >   - If the register has been updated by the PE the kernel clears it and
> >     reports the error.
> > 
> > The series contains as well an optimization to mte_assign_mem_tag_range().
> > 
> > The series is based on linux 5.11-rc2.
> > 
> > To simplify the testing a tree with the new patches on top has been made
> > available at [1].
> > 
> > [1] https://git.gitlab.arm.com/linux-arm/linux-vf.git mte/v10.async
> > 
> > Cc: Catalin Marinas <catalin.marinas@....com>
> > Cc: Will Deacon <will.deacon@....com>
> 
> Will is not in arm anymore :( Sorry Will... I will fix this in v2.

If only you worked for payroll ;)

Will