Re: vn_fullpath question.

Robert Watson wrote:
Nikolay Pavlov wrote:

Hi. I am trying to extend fstat utility, so that it can use name cache to
recreate full path at least for text. I have found vn_fullpath function
usefull in this case. I am newbe in C, so it could be stupid question, but
could someone explaine what is "struct thread *td" in argument list of this
function. Is this the thread which opened the vnode initially or it is the
thread which searches for the vnode? i.e. fstat thread. In any case how i
can get this *td structure?

vn_fullpath(9) is a kernel API, not a user API, so can only be invoked from
kernel space. There are unimplemented, undocumented prototypes in the system
call table for __getpath_fromfd() and __getpath_fromaddr(), which are
presumably intended (with adequate permissions) to allow converting file
descriptor indexes into paths, etc. I think Peter dropped them in, but I'm
not sure if he's posted patches.

Nikolay, you might want to have a look at the source code
of the "lsof" utility (ports/sysutils/lsof). It is able
to display path names for file descriptors. Maybe you can
borrow an idea from it.

It might also be worth mentioning that our friends from the
DragonFly BSD project (derived from FreeBSD 4) have added
the ability to display path names to their version of the
fstat utility. You can look at their cvsweb here:
http://www.dragonflybsd.org/cvsweb/src/usr.bin/fstat/

However, I suspect that they have also made modifications
to the kernel interfaces in order to support the fstat
utility, so their improvements to that utility might not
be applicable to FreeBSD.

Best regards
Oliver

--
Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing
Dienstleistungen mit Schwerpunkt FreeBSD: http://www.secnetix.de/bsd
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