[kernel-hardening] Re: [RFC] x86, mm: start mmap allocation for libs from low addresses

["H. Peter Anvin" <hpa@zytor.com>]

On 08/22/2011 01:14 PM, Vasiliy Kulikov wrote:
> 
>> Code-wise:
>>
>> The code is horrific; it is full of open-coded magic numbers;
> 
> Agreed, the magic needs macro definition and comments.
> 
>> it also
>> puts a function called arch_get_unmapped_exec_area() in a generic file,
>> which could best be described as "WTF" -- the arch_ prefix we use
>> specifically to denote a per-architecture hook function.
> 
> Agreed.  But I'd want to leave it in mm/mmap.c as it's likely be used by
> other archs - the changes are bitness specific, not arch specific.  Is
> it OK if I do this?
> 
> #ifndef HAVE_ARCH_UNMAPPED_EXEC_AREA
> void *arch_get_unmapped_exec_area(...)
> {
>     ...
> }
> #endif
> 

Only if this is really an architecture-specific function overridden in
specific architectures.  I'm not so sure that applies here.
Furthermore, I'm not even all that sure what this function *does*.

	-hpa