Messages in this thread | | | From | (H. Peter Anvin) | Subject | Re: iopl | Date | 21 Sep 1998 16:49:04 GMT |
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Followup to: <199809052027.WAA01372@manjak.knm.org.pl> By author: Guest <guest@manjak.knm.org.pl> In newsgroup: linux.dev.kernel > > Hello, > > I've got a question concerning iopl() syscall. What are > the parameters of the function... I mean which level > give me what priviledges ?! I've looked at the > kernel sources, but those bitmasks doesn't say me anything. > ... so what gives me: > > iopl(1) > iopl(2) > iopl(3) > > Thanks, > Martin >
iopl(1) or iopl(2) don't buy you anything; iopl(3) lets you do any I/O.
Background: the x86 considers a process "I/O privileged" if IOPL >= CPL. Since a user-space process in Linux has CPL=3 and a kernel-space process has CPL=0, only IOPL=0 and IOPL=3 really matter.
-hpa
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