[PATCH] ARM: Implement copy_to_user_page() for noMMU

[Jamie Lokier]

Catalin Marinas wrote:
> > Other variations such as writing when a mapping is !VM_EXEC and later
> > mapping or mprotecting the same shmem VM_EXEC, but it's even more
> > forbidden semantically to write to a read-only mapping (and just as
> > unchecked on nommu), and conversion of writable to VM_EXEC ought to
> > flush i-cache at mprotect time.
> 
> ARM Linux doesn't do any cache maintenance for mprotect on VIPT or noMMU
> hardware (not sure about VIVT). We discussed this in the past and it
> wasn't clear whether it is required or not.

I still think it ought to happen on mprotect, but maybe that's a
linux-arch discussion.  I saw IRIX actually has two PROT_EXEC flavours
for mprotect so you can choose.

Back to this, just to double check, what about mapping?  E.g. where a
shmem is mapped writable (but not executable), has executable code
written to it by ptrace, and is later mapped in another process and
executed.  Will the act of making the second mapping flush i-cache for
that range?  (No-MMU doesn't need to flush caches on task switch)

-- Jamie