On Sat, Aug 05, 2017 at 12:49:19AM +0300, Yury Norov wrote:

On Fri, Aug 04, 2017 at 06:38:10PM +0100, Catalin Marinas wrote:

quoted

On Wed, Aug 02, 2017 at 08:29:40PM +0300, Yury Norov wrote:

quoted

On Wed, Aug 02, 2017 at 05:39:01PM +0100, Catalin Marinas wrote:

quoted

On Mon, Jul 31, 2017 at 05:48:25PM +0300, Yury Norov wrote:

quoted

In patch 06beb72fbe23e ("arm64: introduce mm context flag to keep 32 bit task
information") you introduce the field flags but use it only for a single flag -
TIF_32BIT. It looks hacky to me for three reasons:
 - The flag is introduced for the case where it's impossible to get the thread
   info structure for the thread associated with mm. So thread_info flags (TIF)
   may also be unavailable at place. This is not the case for the only existing
   user of if - uprobes, but in general this approach requires to include thread
   headers in mm code, which may become unwanted dependency.
 - New flag, if it uses TIF bits, for consistency should for example set/clear
   TIF_32BIT_AARCH64 for ILP32 tasks. And to be completely consistent, with
   current approach we'd mirror thread_info flags to mm_context flags. And keep
   it syncronized.
 - If we start using TIF flags here, we cannot easily add new mm_context
   specific bits because they may mess with TIF ones.

I think that this is not what was intended when you added new field in
mm_context_t.

TIF_32BIT was handy at the time but it indeed denotes AArch32 user
task. For ILP32 we wouldn't need to set this bit since the instruction
set is A64 and uprobe should support it (though not sure anyone tried).
I noticed in your patch introducing binfmt_ilp32.c that SET_PERSONALITY
actually sets this flag in the mm context.

Depending on what will be decided here, I'll change ilp32 patch
accordingly.

Since this was meant to keep track of AArch32 tasks, the ILP32
personality macros need to clear it.

 
I understand it. I meant that the exact fix will depend on what we
will figure out here.

I have also fixed small issue with headers in the patch "arm64: signal:
share lp64 signal structures and routines to ilp32", so I think I will
create rc4-based branch that will incorporate all changes. But if you
need I can also update rc3-based branch. And 4.12 - do you need the
updated version of it?

Not for 4.12, I'll just take it as it is with a fixup for
SET_PERSONALITY. I will hold off with an 4.13 branch until the final
4.13 is actually released, so you can rebase your -rc3/rc4 branch.

-- 
Catalin