file: /proc/sys/vm/mmap_rnd_compat_bits
variable: vm.mmap_rnd_compat_bits
Official reference

This value can be used to select the number of bits to use to determine the random offset to the base address of vma regions resulting from mmap allocations for applications run in compatibility mode on architectures which support tuning address space randomization. This value will be bounded by the architecture’s minimum and maximum supported values.

This value can be changed after boot using the /proc/sys/vm/mmap_rnd_compat_bits tunable