# Re: \[PATCH 3/5\] powerpc64: Add .opd based function descriptor dereference

- From: Michael Ellerman \<mpe@ellerman.id.au\>
- Date: 2017-09-19 10:22:43 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2017/09/5090706
- Thread: https://ratatoskr.run/linuxppc-dev/2017/09/5089064/t.md

```text
"Naveen N. Rao" [ref] writes:

> On 2017/09/16 12:53PM, Sergey Senozhatsky wrote:
>> We are moving towards separate kernel and module function descriptor
>> dereference callbacks. This patch enables it for powerpc64.
>> 
>> For pointers that belong to the kernel
>> -  Added __start_opd and __end_opd pointers, to track the kernel
>>    .opd section address range;
>> 
>> -  Added dereference_kernel_function_descriptor(). Now we
>>    will dereference only function pointers that are within
>>    [__start_opd, __end_opd];
>> 
>> For pointers that belong to a module
>> -  Added dereference_module_function_descriptor() to handle module
>>    function descriptor dereference. Now we will dereference only
>>    pointers that are within [module->opd.start, module->opd.end].
>
> Would it be simpler to just use kernel_text_address() and dereference 
> everything else? See commit 83e840c770f2c5 ("powerpc64/elfv1: Only 
> dereference function descriptor for non-text symbols") for a related 
> patch.

Yeah that would be a lot simpler and probably work perfectly well.

cheers
```