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

On Fri, Mar 9, 2018 at 3:15 PM, Robin Murphy [off-list ref] wrote:

Hi Andrey,

On 09/03/18 14:01, Andrey Konovalov wrote:

quoted

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.

Thanks!