HelenOS sources

KM_AMD64_NON_IDENTITY_SIZE   47 kernel/arch/amd64/include/arch/mm/km.h #define KM_AMD64_NON_IDENTITY_SIZE   UINT64_C(0x00007fff80000000)
KM_AMD64_NON_IDENTITY_SIZE   57 kernel/arch/amd64/include/arch/mm/km.h #define KM_AMD64_NON_IDENTITY_SIZE   UINT64_C(0x0000400000000000)
HelenOS homepage, sources at GitHub