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[Bug translator/10454] Raw number statement probes won't work without dwarf info
- From: "jistone at redhat dot com" <sourceware-bugzilla at sourceware dot org>
- To: systemtap at sources dot redhat dot com
- Date: 28 Jul 2009 19:30:39 -0000
- Subject: [Bug translator/10454] Raw number statement probes won't work without dwarf info
- References: <20090728133231.10454.mjw@redhat.com>
- Reply-to: sourceware-bugzilla at sourceware dot org
------- Additional Comments From jistone at redhat dot com 2009-07-28 19:30 -------
(In reply to comment #0)
> We hit this part of tapsets.cxx (query_cu):
>
> // Verify that a raw address matches the beginning of a
> // statement. This is a somewhat lame check that the address
> // is at the start of an assembly instruction. Mark probes are in the
> // middle of a macro and thus not strictly at a statement beginning.
> // Guru mode may override this check.
>
> It might be an idea to allow "misplaced statement expressions" for user space
> probes always since it isn't very "dangerous". Also note that "assembly
> instruction" isn't really what is being tested. It is really whether there is
> dwarf line info that says the statement given starts on a line.
Well, being the beginning of a statement is a sufficient condition for being the
beginning of an assembly instruction, right? Sure, that's not a necessary
condition, but that's probably why this is a "somewhat lame check".
As for danger -- a misplaced probe in a user app won't bring down the system,
but it will likely break or even crash the application, which still violates our
philosophy of harmless probing.
--
http://sourceware.org/bugzilla/show_bug.cgi?id=10454
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