user processes that are given direct access to I/O ports ??

sulekha · 10-05-2010, 01:58 AM

Hi all,

normally all I/O goes through the kernel so that it can schedule the operations and prevent processes from stepping on each other. A few special user processes are allowed to slide around the kernel, usually by being given direct access to I/O ports. X servers are the most common example of this isn't it ?.

can any one give examples for any other processes that are allowed to slide around the kernel ?

mf93 · 10-05-2010, 08:16 PM

any program that runs as root may use direct i/o access, although they may need suid bit set to 1 for other reasons. Generally most shouldnt need it, but some may, im sure a google search will return a list someone has put together. why do you need it?

sulekha · 10-06-2010, 01:13 AM

Quote:

Originally Posted by mf93

any program that runs as root may use direct i/o access, although they may need suid bit set to 1 for other reasons. Generally most shouldnt need it, but some may, im sure a google search will return a list someone has put together. why do you need it?

well I just going trough this article:- http://tldp.org/HOWTO/Unix-and-Inter...-programs.html

just wanted to get a better understanding

mf93 · 10-06-2010, 09:17 PM

I doubt there are very many and i dont think the fact they use direct i/o is significant in any case. the most important thing to remember is the i/o ports are protected by the kernel and one must query the kernel through system calls (also known as 'interrupts', which while similar to hardware interrupts are not the exact same)