# Re: modules: add ro\_after\_init support

- From: Jessica Yu \<hidden\>
- Date: 2016-07-21 23:11:43 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2016/07/4799792
- Thread: https://ratatoskr.run/linux-api/2016/06/4772577/t.md

```text
+++ Kees Cook [21/07/16 16:03 -0700]:
>On Wed, Jun 29, 2016 at 9:56 PM, Rusty Russell [ref] wrote:
>> Jessica Yu [ref] writes:
>>> +++ Rusty Russell [29/06/16 10:38 +0930]:
>>>>Jessica Yu [ref] writes:
>>>>> Add ro_after_init support for modules by adding a new page-aligned section
>>>>> in the module layout (after rodata) for ro_after_init data and enabling RO
>>>>> protection for that section after module init runs.
>>>>>
>>>>> Signed-off-by: Jessica Yu <redacted>
>>>>
>>>>I would prefer a "bool after_init" flag to module_enable_ro().  It's
>>>>more explicit.
>>>
>>> Sure thing, I was just initially worried about the
>>> module_{enable,disable}_ro() asymmetry. :)
>>
>> Yes, but I think compile-time-analyzable behaviour beats
>> runtime-analyzable behaviour for clarity.
>>
>>>>Exposing the flags via uapi looks like a wart, but it's kind of a
>>>>feature, since we don't *unset* it in any section; userspace may want to
>>>>know about it.
>>>
>>> Hm, I'm still unsure about this. I'm starting to think it might be a
>>> bit overkill to expose SHF_RO_AFTER_INIT through uapi (although that
>>> is where all the other SHF_* flags are defined) SHF_RO_AFTER_INIT
>>> would technically be used only internally in the kernel (i.e. module
>>> loader), and it'd also be considered a non-standard flag, using a bit
>>> from SHF_MASKOS (OS-specific range). What do you think?
>>
>> Some arch *could* use it by setting the flag in a section in their
>> module I think; we don't stop them.  Since the other flags are there,
>> I'd leave it.
>>
>> We don't expose the flags via sysfs, though, so that's the only
>> exposure.
>
>What's the state of this series? I'd love it if the functionality
>could land for v4.8...
>

Hi Kees,

Sorry for the delay! Have been busier than usual lately. I'll be able
to get v2 out tomorrow.

Thanks!
Jessica
```