In include/x86_64-linux-gnu/asm/unistd_64.h, I see a system call named tuxcall,
#define __NR_tuxcall 184
There is nothing about it in man tuxcall except to say that it's an unimplemented system calls. What did it do? Was it never implemented, or did it do something in antiquity?
tuxcall is the place-holder for the tux system call which was used by user-space tools to communicate with the TUX kernel module, which implemented the TUX web server. This was a web server running entirely in the kernel; it was maintained by Ingo Molnar until improvements in other parts of Linux, notably thread support with NPTL, brought user-space web server performance up to the level attained by TUX.
You can still find the TUX 3 patches for Linux 2.6.18 among Ingo’s patches, including the implementation of sys_tux (the system call in question). The user-space portion, which includes the documentation, can be found on the Wayback Machine (thanks hvd!).
I've found something from non-standard-syscalls:
tuxcall() - This call comes from a TUX module and is sent to the kernel. The call asks the kernel to perform some task for the module. A TUX module is basically a server application/daemon in the form of a Linux module. Imagine an Apache server being a kernel module; that is essentially how TUX works.
