Re: [PATCH v10 06/10] powerpc/mm/ptdump: debugfs handler for W+X checks at runtime

Jordan Niethe [off-list ref] writes:

From: Russell Currey <redacted>

Optionally run W+X checks when dumping pagetable information to
debugfs' kernel_page_tables.

To use:
    $ echo 1 > /sys/kernel/debug/check_wx_pages
    $ cat /sys/kernel/debug/kernel_page_tables

and check the kernel log.  Useful for testing strict module RWX.

To disable W+X checks:
	$ echo 0 > /sys/kernel/debug/check_wx_pages

Update the Kconfig entry to reflect this.

Also fix a typo.

Reviewed-by: Kees Cook <redacted>
Signed-off-by: Russell Currey <redacted>
[jpn: Change check_wx_pages to act as mode bit affecting
      kernel_page_tables instead of triggering action on its own]
Signed-off-by: Jordan Niethe <redacted>
---
v10: check_wx_pages now affects kernel_page_tables rather then triggers
     its own action.

Hmm. I liked the old version better :)

I think you changed it based on Christophe's comment:

  Why not just perform the test everytime someone dumps kernel_page_tables ?


But I think he meant *always* do the check when someone dumps
kernel_page_tables, not have another file to enable checking and then
require someone to dump kernel_page_tables to do the actual check.

Still I like the previous version where you can do the checks
separately, without having to dump the page tables, because dumping can
sometimes take quite a while.

What would be even better is if ptdump_check_wx() returned an error when
wx pages were found, and that was plumbed out to the debugs file. That
way you can script around it.

cheers