[PATCH resend v3 1/2] ntdll: Try mapping free memory region outside of reserved regions.

[Rémi Bernon]

On 12/24/19 1:27 PM, Alexandre Julliard wrote:
> Rémi Bernon <rbernon at codeweavers.com> writes:
> 
>> We assumed that all mapped regions are known by Wine view tree, which
>> is obviously not the case with external allocations. This could lead to
>> memory corruption when find_free_area returns an expected free region
>> which is already mapped. Using MAP_FIXED forces mmap to succeed and
>> corrupts the mapping.
> 
> I have a feeling that this would be cleaner with a separate function,
> particularly since the algorithm to find free space in the system areas
> could be made smarter.
> 

I'm not sure about what you mean by "smarter".

The original patches this whole zero bits thing is based upon were 
trying semi-random addresses to try to find free system areas, with a 
timeout [1], but I'm not completely convinced that it's better 
especially with the top_down flag to implement.

It could also read /proc/self/maps, making it not portable, I guess. Or 
maybe there's a way to enumerate mapped memory, including non-Wine, that 
I'm missing?

Or you just mean the search within an expected free area could do a 
bisection instead of iterating linearly?

[1] 
https://www.winehq.org/pipermail/wine-devel/attachments/20190302/f96c118f/attachment.obj
-- 
Rémi Bernon <rbernon at codeweavers.com>