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Re: copy faults from user_string* functions
- From: Eric Wong <normalperson at yhbt dot net>
- To: "Frank Ch. Eigler" <fche at redhat dot com>
- Cc: Systemtap List <systemtap at sourceware dot org>
- Date: Fri, 26 Jul 2013 19:42:20 +0000
- Subject: Re: copy faults from user_string* functions
- References: <20130726063634 dot GA32443 at dcvr dot yhbt dot net> <y0miozxmeqe dot fsf at fche dot csb> <20130726175602 dot GA5773 at dcvr dot yhbt dot net>
Eric Wong <normalperson@yhbt.net> wrote:
> "Frank Ch. Eigler" <fche@redhat.com> wrote:
> > normalperson wrote:
> > > Hi all, just to clarify, not all of these faults are user errors, right?
> > > I get these sometimes with some strings (constants, I think):
> > > ERROR: user string copy fault -14 at 000000000042f16c near identifier 'user_string_n' at $prefix/share/systemtap/tapset/uconversions.stp:120:10
> > > [...]
> >
> > It can simply mean having some not-yet-paged-in data, which in the
> > spirit of non-interference, stap will not trigger a page fault for.
> > Please try error-catching constructs such as try{}catch{}, or
> > --skip-badvars to tolerate them.
>
> --skip-badvars seems to work for me.
Oops, I was on the wrong machine and running an older branch with
--skip-badvars. try{}catch{} was needed for the user_string_n issue
I was having, but that seems to work.
> Is there any optional way to get stap to trigger page faults to get
> that data?
I could restructure my code to pass integers instead of strings as
a workaround, but I'm trying my best to be lazy :>