fix pnpinfo on arch=amd64

[Alexander Best]

On Sat Oct 23 10, Garrett Cooper wrote:
> On Sat, Oct 23, 2010 at 5:22 PM, Alexander Best <arundel at freebsd.org> wrote:
> > this tiny patch will fix pnpinfo so it doesn't core dump (bus error) any
> > longer on arch=amd64.
> 
> 1. I had to modify the Makefile to get it to work.

probably because you built pnpinfo from contrib/pnpinfo and not from
usr.sbin/pnpinfo. i'm not sure your changes to contrib/pnpinfo/Makefile are
according to current practice. maybe the vendor Makefile shouldn't be modified
and every additional stuff should rather go into usr.sbin/pnpinfo/Makefile. but
i don't really know.

also in the in usr.sbin/pnpinfo/makefile there's a check for PC98 that i'm not
sure is really needed.

> 2. FWIW, I don't there's really much point in adding a check for only
> x86 architectures, if the tool is capable of more than that.

yeah you're probably right. to be honest i know nothing about
"archs != i386|amd64". ;) so i just added the amd64 option, because i didn't
want to break pnpinfo on other platforms.

> 3. Might as well close the file descriptor after opening it.

right. expecially, because opening /dev/io (even in ro mode) is a huge security
issue. so better close it asap.

of course on i386/amd64 (maybe pc98 too?) i386_set_ioperm(2) could be used to
work around the security issue. but since pnpinfo's job is to access hardware
directly i think opening /dev/io directly can be consideren ok.

> 
> SIGBUS occurs because it doesn't have permission to write via outb.
> It's a shame that there isn't a more proper way to catch this SIGBUS
> fault minus adding a SIGBUS handler (but that might have other
> undesired side effects).

well on i386/amd (pc98?) you could use i386_get_ioperm(2) to check for proper
io permissions.

> Thanks,
> -Garrett



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