NtQuerySystemInformation:
77f67d2c b87c000000       mov     eax,0x7c
77f67d31 8d542404         lea     edx,[esp+0x4]
77f67d35 cd2e             int     2e
77f67d37 c21000           ret     0x10

NtSetSystemInformation:
77f68034 b8ae000000       mov     eax,0xae
77f68039 8d542404         lea     edx,[esp+0x4]
77f6803d cd2e             int     2e
77f6803f c20c00           ret     0xc

Example 4: Sample API gates inside ntdll.dll.