On Thu, Jun 21, 2012 at 2:57 PM, Rik van Riel [off-list ref] wrote:

For topdown allocations, we need to keep track of the highest
mapped VMA address, because it might be below mm->mmap_base,
and we only keep track of free space to the left of each VMA
in the VMA tree.  It is tempting to try and keep track of
the free space to the right of each VMA when running in
topdown mode, but that gets us into trouble when running on
x86, where a process can switch direction in the middle of
execve.

Just a random thought - one way to handle this could be to always have
some sentinel VMA at the end of the address space. Some architectures
might already have it in the form of the vsyscall page, or we could
always have some other sentinel right above the last usable user page
?

-- 
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.

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