[RFC PATCH 0/6] arm64: untag user pointers passed to the kernel

Andrey Konovalov andreyknvl at google.com
Sat Mar 10 04:58:00 AEDT 2018

On Fri, Mar 9, 2018 at 3:15 PM, Robin Murphy <robin.murphy at arm.com> wrote:
> Hi Andrey,
> On 09/03/18 14:01, Andrey Konovalov wrote:
>> 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.
> If you propose changing the ABI, then
> Documentation/arm64/tagged-pointers.txt needs to reflect the new one, since
> passing nonzero tags via syscalls is currently explicitly forbidden.
> Robin.

Hi Robin!

I will include changes to Documentation/arm64/tagged-pointers.txt in
the next version.


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