Date: Wed, 12 Mar 2014 07:54:22 +1030 From: "Daniel O'Connor" <doconnor@gsoft.com.au> To: Robert Mustacchi <rm@joyent.com> Cc: freebsd-dtrace@freebsd.org Subject: Re: dtracing static symbols Message-ID: <4DCD0848-F635-4CAE-B109-9941395B6AB8@gsoft.com.au> In-Reply-To: <531F3302.8010106@joyent.com> References: <1394514256.45492.YahooMailBasic@web192604.mail.sg3.yahoo.com> <7C202659-0BD9-4F93-8886-24DD7AEB495F@gsoft.com.au> <531F3302.8010106@joyent.com>
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[-- Attachment #1 --] On 12 Mar 2014, at 2:30, Robert Mustacchi <rm@joyent.com> wrote: > On 03/10/2014 10:34 PM, Daniel O'Connor wrote: >> >> On 11 Mar 2014, at 15:34, Prashanth Kumar <pra_udupi@yahoo.co.in> wrote: >>> If the binary being traced has static symbols in its symbol table, DTrace should >>> be able to trace the function. Can you describe the example where you found this >>> difference in FreeBSD and OSX? >> >> Unfortunately the static symbols don't show up in the symbol table (as shown by nm). >> >> Is there a compile or link flag which will change that? > > Because it's a static function the compiler may inline it, which may be > why you don't actually see an entry in nm nor that it can be found by > DTrace. You'll want to look at the disassembled output of your program > to see if it was inlined. Different compilers can and will do different > things. There generally are flags you can pass to the compiler to tell > it not to inline it, but that's compiler specific. I just realised that my test contradicted the statement I made earlier.. However I checked my test program (static.c) and it the functions definitely appear in the symbol table. [mdtest 21:13] ~ >nm static|egrep '(foo|bar)' 0000000000400600 T bar 0000000000400620 t foo I also added the noinline attribute for good measure. It seems that _nothing_ shows up for executables, only shared libraries, this is OK for me since my code resides in a library but it is a bit surprised nonetheless.. >> (I'm not sure what the various numbers mean) > > The pid provider can instrument any instruction in a function, those are > the instruction offsets. Ahh, thanks. -- Daniel O'Connor software and network engineer for Genesis Software - http://www.gsoft.com.au "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Comment: GPGTools - http://gpgtools.org iD8DBQFTH38G5ZPcIHs/zowRAvGvAKCBvfjbhb/YiYMzlXOXmGaMI4K0MQCeOdSB qQv3Ka8ftX2+ddVfeE+qZpQ= =tKS3 -----END PGP SIGNATURE-----help
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