Re: [PATCH v4 0/5] arm64: ARMv8.5-A: MTE: Add async mode support

From: Andrey Konovalov
Date: Tue Jan 19 2021 - 13:56:47 EST

On Mon, Jan 18, 2021 at 7:30 PM Vincenzo Frascino
<vincenzo.frascino@xxxxxxx> 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-rc3.
> To simplify the testing a tree with the new patches on top has been made
> available at [1].
> [1] mte/v10.async

Hi Vincenzo,

This change has multiple conflicts with the KASAN testing patches that
are currently in the mm tree. If Andrew decides to send all of them
during RC, then this should be good to go through arm64. Otherwise, I
guess this will need to go through mm as well. So you probably need to
rebase this on top of those patches in any case.