Re: [PATCH v15 00/17] arm64: untag user pointers passed to the kernel

[Catalin Marinas]

On Tue, May 28, 2019 at 04:14:45PM +0200, Andrey Konovalov wrote:
> Thanks for a lot of valuable input! I've read through all the replies
> and got somewhat lost. What are the changes I need to do to this
> series?
> 
> 1. Should I move untagging for memory syscalls back to the generic
> code so other arches would make use of it as well, or should I keep
> the arm64 specific memory syscalls wrappers and address the comments
> on that patch?

Keep them generic again but make sure we get agreement with Khalid on
the actual ABI implications for sparc.

> 2. Should I make untagging opt-in and controlled by a command line argument?

Opt-in, yes, but per task rather than kernel command line option.
prctl() is a possibility of opting in.

> 3. Should I "add Documentation/core-api/user-addresses.rst to describe
> proper care and handling of user space pointers with untagged_addr(),
> with examples based on all the cases seen so far in this series"?
> Which examples specifically should it cover?

I think we can leave 3 for now as not too urgent. What I'd like is for
Vincenzo's TBI user ABI document to go into a more common place since we
can expand it to cover both sparc and arm64. We'd need an arm64-specific
doc as well for things like prctl() and later MTE that sparc may support
differently.

-- 
Catalin