a->_a_stackaddr = (uintptr_t)p;
while (mremap(p-l-PAGE_SIZE, PAGE_SIZE, 2*PAGE_SIZE, 0)==MAP_FAILED && errno==ENOMEM)
l += PAGE_SIZE;
a->_a_stackaddr = (uintptr_t)p;
while (mremap(p-l-PAGE_SIZE, PAGE_SIZE, 2*PAGE_SIZE, 0)==MAP_FAILED && errno==ENOMEM)
l += PAGE_SIZE;