Re: [PATCH v4 3/3] csu: Implement and use _dl_early_allocate during static startup

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 05/05/2022 15:03, Florian Weimer wrote:
> * Adhemerval Zanella:
> 
>> I still think there will be way simpler to just use mmap here, it will allow
>> to use a generic version without the need to fiddle with a Linux specific 
>> (it will be required just a wrapper to MMAP_CALL_INTERNAL, instead of an
>> implementation that need to know both sbrk and mmap internals).
> 
> We need to wrap the difference in error checking as well.
> 
>> I think you even clean up all the dl-brk.c and similar files required to
>> make brk/sbrk work on the loader with an allocator that only uses mmap.
> 
> At the cost of additional VMAs, sure.  We won't be able to reuse the
> unused tail of the allocation easily because we do not know the page
> size yet.  __minimal_malloc does not yet work at this point.  We also
> lose some ASLR.  I'm not convinced it's worth it.

It is another code that does something similar to __minimal_malloc to
a specific usage, so now we have another allocation scheme that is used
solely for static initialization.  And it does something different than
__minimal_malloc, so has different semantic.

I am not really against it, but initialization code is already 
quite complex with a lot of different paths for dynamic/static case,
so I think it would be good to have single loader/static allocation 
code.