Re: [PATCH v3 2/4] mm: Make generic arch_is_kernel_initmem_freed() do what it says

[Andrew Morton <akpm@linux-foundation.org>]

On Fri, 01 Oct 2021 17:14:41 +1000 Daniel Axtens <dja@axtens.net> 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?