On Oct 25, 2021, at 10:45 AM, Dave Hansen [off-list ref] wrote:

On 10/25/21 9:19 AM, Nadav Amit wrote:

quoted

That was my first version, but I was concerned that perhaps there is
some strange scenario in which both X86_PF_WRITE and X86_PF_INSN can
be set. That is the reason that Peter asked you whether this is
something that might happen.

If you confirm they cannot be both set, I would the version you just
mentioned.

I'm pretty sure they can't be set together on any sane hardware.  A
bonkers hypervisor or CPU could do it of course, but they'd be crazy.

BTW, feel free to add a WARN_ON_ONCE() if WRITE and INSN are both set.
That would be a nice place to talk about the assumption.

I can do that. But be aware that if the assumption is broken, it might
lead to the application getting stuck in an infinite loop of
page-faults instead of receiving SIGSEGV.