Re: [PATCH 0/2] Support for set_memory_* outside of module space

From: Laura Abbott
Date: Wed Nov 04 2015 - 13:52:04 EST

On 11/03/2015 03:42 PM, Kees Cook wrote:
On Tue, Nov 3, 2015 at 1:48 PM, Laura Abbott <labbott@xxxxxxxxxxxxxxxxx> wrote:


Based on a recent discussion[1] there is interest in having set_memory_* work
on kernel memory for security and other use cases. This patch adds the
ability for that to happen behind a kernel option. If this is welcome enough,
the Kconfig can be dropped. This has been briefly tested but not stress tested.



Laura Abbott (2):
arm64: Get existing page protections in split_pmd
arm64: Allow changing of attributes outside of modules

arch/arm64/Kconfig.debug | 11 +++++++
arch/arm64/mm/mm.h | 3 ++
arch/arm64/mm/mmu.c | 11 ++++---
arch/arm64/mm/pageattr.c | 74 ++++++++++++++++++++++++++++++++++++++++++++----
4 files changed, 88 insertions(+), 11 deletions(-)

This seems like the right thing to have. What's arm64 doing for the
equivalent of x86 and arm's set_kernel_text_* functions? x86 and arm
call their set_memory_* functions, for example. A quick examination
shows mm/mmu.c is just doing it "by hand" in fixup_executable and
mark_rodata_ro? Could those functions use the new set_memory_* ones?

It looks like mark_rodata_ro could probably use the set_memory_ro. I'll
have to test it out. Longer term, the page table setup code should
probably just be pulled out into a common file.

Do you know the code path in ftrace which would trigger the set_kernel_text_*
If not, I'll go see if I can figure out if it's implemented yet on arm64.


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