spec - Local Sector 7 web page

Ena bling I/O Por ts On PC Platfor ms (not linux)The spec distribution includes a program called io_enable for use on systems derivedfrom AT&T System V/386 UNIX. This program enables user programs (such as spec)to write to selected I/O ports on the adapter cards plugged into the motherboard.spec automatically invokes io_enable if the hardware configuration requires it. Portsonly need to be enabled once after booting the computer. The total number of portsthat can be enabled is quite limited, though. The io_enable program must be ownedby root and have set-user-id execute mode.Youcan invoke io_enable from the shell using the following syntax:io_enable [ −d ] port_address [ port_address ... ]The −d option causes the specified ports to be removed from the systems list ofenabled ports. Port addresses must be given as hexadecimal numbers with a 0x prefix.The addresses may be specified either individually, asahyphen-separated range,or as a base address followed by a comma and a count. Usage might be,io_enable 0x300-0x302 0x312,4to add 0x300, 0x301, 0x302, 0x312, 0x313, 0x314 and 0x315 to the enabled-port list.Ena bling I/O Por ts On PC Platfor ms Running linuxOn PC systems running linux, I/O port access is achieved by changing the process’sI/O privilege level using the system call iopl(). For this method to work, the specexecutable must be set-user-id root. Note, though, that the root privilege is onlyenabled for the duration of the system call. The rest of the time, the process only hasthe access privileges of the real user. (Prior to spec release 4.03.01, I/O port accesson linux required a kernel patch.)200 ADMINISTRATOR’S GUIDE INTERIM WORK-IN-PROGRESS (8/16/01) NOT FOR GENERAL DISTRIBUTION