personality, sigreturn − undocumented system calls Undocumented system calls. As of Linux 1.3.6, there are 144 system calls listed in This man page mentions those calls which are implemented in the kernel but not yet documented in man pages. Some of these calls do not have prototypes in the DLL 4.6.27 include files. If you have information about these system calls, please look in the kernel source code, write a man page (using a style similar to that of the other Linux section 2 man pages), and send it to aeb@cwi.nl for inclusion in the next man page release from the Linux Documentation Project.