Bug 3280 - missing entrypc dwarf line record for function 'jprobe_return'
Summary: missing entrypc dwarf line record for function 'jprobe_return'
Status: RESOLVED FIXED
Alias: None
Product: systemtap
Classification: Unclassified
Component: translator (show other bugs)
Version: unspecified
: P2 normal
Target Milestone: ---
Assignee: Unassigned
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2006-09-28 21:47 UTC by David Wilder
Modified: 2007-08-17 21:45 UTC (History)
0 users

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Description David Wilder 2006-09-28 21:47:16 UTC
When running the following tap script on s390:
probe kernel.function("*") {}
 
I receive the following error.
[...]
semantic error: missing entrypc dwarf line record for function
'jprobe_return'
semantic error: no match for probe point
while: resolving probe point kernel.function("jprobe_return")

jprobe_return() is tagged __kprobes so it should automatically blacklisted;
However, the error is thrown before the blacklist is consulted.  This results is
that the tap script not building.

Here is the
void __kprobes jprobe_return(void)
{
        asm volatile (".word 0x0002");
}

I discussed this on the systemtap ml.

>The problem here is that while some of these routines are blacklisted
>> in the kernel (kprobe_register will fail), they are not blacklisted in
>> the translator.  We need to teach the translator to look for the
>> kernel-side blacklist info too (the .kprobes section naming methinks),
>> and treat it similarly to the .init/.exit special cases already
>> present in tapsets.cxx.
>> 
>> This way, function("*") will quietly exclude the blacklisted
>> functions. 
>> 
>> - FChE


Indeed this would be nice -- see bug #2639.
http://sources.redhat.com/bugzilla/show_bug.cgi?id=2639

In the mean time, we can add additional functions to the static
blacklist in the translator.  See dwarf_query::build_blacklist().  It's
unfortunate that we have to try to maintain this, but I suppose it's
better than nothing.  And, as you mention, kprobe_register will block
these too, so this is really just a matter of *when* the error is
caught.

Josh
Comment 1 David Smith 2006-10-12 16:05:01 UTC
This issue needs to be retested since BZ2639 has been fixed.  All '__kprobes'
functions should be automatically blacklisted.
Comment 2 Frank Ch. Eigler 2007-08-17 21:45:32 UTC
translator blacklist automatically includes kernel __kprobes functions now.