X32 has it's own (partial) set of syscalls. Similar to how a x86-64 kernel ran run traditional x86-32 code. 32-bit code tells the kernel to allocate in the low

X32 has it's own (partial) set of syscalls. Similar to how a x86-64 kernel ran run traditional x86-32 code. 32-bit code tells the kernel to allocate in the lower 32-bit address space (via MAP_32BIT) precisely so that the 64-bit pointers the kernel works with can be safely truncated to 32-bit user space pointers.