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    SubjectRe: ptrace single-stepping change breaks Wine
    Mike Hearn <mh@codeweavers.com> wrote:
    >
    > Also a precise description of what flex-mmap does would be good. Google
    > wasn't too informative, best I could get was that it means mmap
    > allocates from the "top" of the address space down. But where is the top
    > exactly?

    Ingo has described it thus:


    before:

    0x08000000 ... binary code
    0x08xxxxxx ... brk area
    0x40000000 ... start of mmap, new mmaps go after old ones
    0xbfxxxxxx ... stack

    after:

    0x08000000 ... binary code
    0x08xxxxxx ... brk area
    0xbfxxxxxx ... _end_ of all mmaps, new mmaps go below old ones
    0xbfyyyyyy ... stack

    the 'after' layout guarantees that brk area (malloc()) can grow
    unlimited and mmap() can grow unlimited - they will meet somewhere
    inbetween when almost all of the VM is used up. [the 'top' of the mmaps
    in the 'after' layout is constrained by the stack ulimit - the stack
    must still fit and we never allocate into the stack's yet unallocated
    and growable hole.]

    with the 'before' layout we've got 900 MB for brk() and 1.9GB for
    mmaps() - a rigid limit.
    -
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