# Re: \[PATCH v3 2/4\] mm: Make generic arch\_is\_kernel\_initmem\_freed() do what it says

- From: Christophe Leroy \<hidden\>
- Date: 2021-11-05 17:23:59 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2021/11/1564096
- Thread: https://ratatoskr.run/linux-arch/2021/09/1526921/t.md

```text


Le 04/11/2021 à 22:44, Andrew Morton a écrit :
> On Fri, 01 Oct 2021 17:14:41 +1000 Daniel Axtens [ref] wrote:
>
>>>   #ifdef __KERNEL__
>>> +/*
>>> + * Check if an address is part of freed initmem. After initmem is freed,
>>> + * memory can be allocated from it, and such allocations would then have
>>> + * addresses within the range [_stext, _end].
>>> + */
>>> +#ifndef arch_is_kernel_initmem_freed
>>> +static int arch_is_kernel_initmem_freed(unsigned long addr)
>>> +{
>>> +	if (system_state < SYSTEM_FREEING_INITMEM)
>>> +		return 0;
>>> +
>>> +	return init_section_contains((void *)addr, 1);
>>
>> Is init_section_contains sufficient here?
>>
>> include/asm-generic/sections.h says:
>>   * [__init_begin, __init_end]: contains .init.* sections, but .init.text.*
>>   *                   may be out of this range on some architectures.
>>   * [_sinittext, _einittext]: contains .init.text.* sections
>>
>> init_section_contains only checks __init_*:
>> static inline bool init_section_contains(void *virt, size_t size)
>> {
>> 	return memory_contains(__init_begin, __init_end, virt, size);
>> }
>>
>> Do we need to check against _sinittext and _einittext?
>>
>> Your proposed generic code will work for powerpc and s390 because those
>> archs only test against __init_* anyway. I don't know if any platform
>> actually does place .init.text outside of __init_begin=>__init_end, but
>> the comment seems to suggest that they could.
>>
>
> Christophe?
>

Sorry for answering late.

I've been thorugh free_initmem() in each architecture. The only sections involved in the freeing actions are [__init_begin, __init_end], so I think checking against __init_being, __init_end is enough.

If some architecture has init text outside of this section, then it is not freed hence not necessary to check.

Christophe
```