Re: [PATCH v19 00/15] arm64: untag user pointers passed to the kernel

From: Vincenzo Frascino
Date: Wed Jul 24 2019 - 13:12:30 EST

Hi Will and Andrey,

On 24/07/2019 15:20, Will Deacon wrote:
> On Wed, Jul 24, 2019 at 04:16:49PM +0200, Andrey Konovalov wrote:
>> On Wed, Jul 24, 2019 at 4:02 PM Will Deacon <will@xxxxxxxxxx> wrote:
>>> On Tue, Jul 23, 2019 at 08:03:29PM +0200, Andrey Konovalov wrote:
>>>> On Tue, Jul 23, 2019 at 7:59 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
>>>>> === Overview
>>>>> arm64 has a feature called Top Byte Ignore, which allows to embed pointer
>>>>> tags into the top byte of each pointer. Userspace programs (such as
>>>>> HWASan, a memory debugging tool [1]) might use this feature and pass
>>>>> tagged user pointers to the kernel through syscalls or other interfaces.
>>>>> Right now the kernel is already able to handle user faults with tagged
>>>>> pointers, due to these patches:
>>>>> 1. 81cddd65 ("arm64: traps: fix userspace cache maintenance emulation on a
>>>>> tagged pointer")
>>>>> 2. 7dcd9dd8 ("arm64: hw_breakpoint: fix watchpoint matching for tagged
>>>>> pointers")
>>>>> 3. 276e9327 ("arm64: entry: improve data abort handling of tagged
>>>>> pointers")
>>>>> This patchset extends tagged pointer support to syscall arguments.
>>> [...]
>>>> Do you think this is ready to be merged?
>>>> Should this go through the mm or the arm tree?
>>> I would certainly prefer to take at least the arm64 bits via the arm64 tree
>>> (i.e. patches 1, 2 and 15). We also need a Documentation patch describing
>>> the new ABI.
>> Sounds good! Should I post those patches together with the
>> Documentation patches from Vincenzo as a separate patchset?
> Yes, please (although as you say below, we need a new version of those
> patches from Vincenzo to address the feedback on v5). The other thing I
> should say is that I'd be happy to queue the other patches in the series
> too, but some of them are missing acks from the relevant maintainers (e.g.
> the mm/ and fs/ changes).

I am actively working on the document and will share v6 with the requested
changes in the next few days.

> Will