Re: [PATCH v10 0/4] arm64: ARMv8.5-A: MTE: Add async mode support

[Andrey Konovalov]

On Fri, Jan 29, 2021 at 7:49 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 is based on linux-next/akpm.
>
> 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.akpm
>
> Changes:
> --------
> v10:
>   - Rebase on the latest linux-next/akpm
>   - Address review comments.

Thinking again about this: properly fixing that tracing issue is
similar to fixing the issue with the tests. Let's do both as a part of
this series.

Here's a tree with the fixes. I've marked the ones that need to be
squashed with "fix!". PTAL, and if the additions look good, please
send v11 with them included.

https://github.com/xairy/linux/commits/vf-v10.async.akpm-fixes