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    SubjectRe: ptrace single-stepping change breaks Wine
    Mike Hearn <> 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:


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


    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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