[dtrace-discuss] USDT probes in Mozilla - can we run dtrace -G against a shared library

[Bart Smaalders]

John Rice wrote:
> Hi - we are looking into adding dtrace probes into mozilla.
> 
> One of the problems is that this is a large project with lots of shared 
> libraries. It would simplify integration of probes if we could just 
> build the shared libs with the embedded probes [using appropriate header 
> from dtrace -h] and then before we do the final link to create the 
> binary, do the dtrace -G to convert all our undef probe symbols into the 
> appropriate ignore ones.
> 
> Simple test seems to say that we cannot. As a test we took Bart's 
> example USDT, split it into two files and generated a shared library for 
> it, but could not get dtrace -G to swallow it:
> 
> $ make simple_probes.o
> dtrace -G -s simple_probes.d simple1.so
> dtrace: failed to link script simple_probes: an error was encountered 
> while processing simple1.so
> make: *** [simple_probes.o] Error 1
> 
> Anyone any ideas? Of course may have screwed up on my shared lib 
> creation ...
> 
> JR
> 
> http://blogs.sun.com/barts/entry/putting_user_defined_dtrace_probe
> 


The easiest thing to do here is to place each library's
probes in each library separately.  Collect all the .o files
that belong in a library into a single .o w/ ld -r and then
use dtrace on it.

I modified the example to put the probes into the shared library;
since there was only a single .o file I use it w/o the ld -r.

- Bart

-- 
Bart Smaalders			Solaris Kernel Performance
barts at cyber.eng.sun.com		http://blogs.sun.com/barts
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CFLAGS=-Kpic
CC=cc

DTRACE=dtrace

default: simple

simple_probes.o: simple_probes.d simple1.o
	$(DTRACE) -G -s simple_probes.d simple1.o

simple1.so: simple1.o simple_probes.o
	$(CC) -o simple1.so  -G simple1.o simple_probes.o -ztext -lc

simple: simple.o simple1.so
	$(CC) -o simple  simple.o -R`pwd` simple1.so
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