Date: Wed, 12 Mar 2014 15:20:17 +1030 From: "Daniel O'Connor" <doconnor@gsoft.com.au> To: Prashanth Kumar <pra_udupi@yahoo.co.in> Cc: Robert Mustacchi <rm@joyent.com>, freebsd-dtrace@freebsd.org Subject: Re: dtracing static symbols Message-ID: <DAFA24CE-0318-4455-9EE3-C8617BBE7D0B@gsoft.com.au> In-Reply-To: <1394599542.80116.YahooMailBasic@web192602.mail.sg3.yahoo.com> References: <1394599542.80116.YahooMailBasic@web192602.mail.sg3.yahoo.com>
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[-- Attachment #1 --] On 12 Mar 2014, at 15:15, Prashanth Kumar <pra_udupi@yahoo.co.in> wrote: > If you run > # env DTRACE_DEBUG=1 dtrace -Ppid\$target -l -c ./static > you will notice that lot of probe creation will fail, also no probes are created for instruction offsets. > you will have to update the libproc library and fasttrap code to trace all the > functions. I don't really care about the function offsets, just static functions. Or are you suggesting updating libproc and the fasttrap code will allow that (as well as instruction offsets)? THanks. > -------------------------------------------- > On Wed, 12/3/14, Daniel O'Connor <doconnor@gsoft.com.au> wrote: > > Subject: Re: dtracing static symbols > To: "Robert Mustacchi" <rm@joyent.com> > Cc: freebsd-dtrace@freebsd.org > Date: Wednesday, 12 March, 2014, 2:54 AM > > > 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 > > > > > > > > -- 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 iD8DBQFTH+eJ5ZPcIHs/zowRAgd5AJ9uSBR0jNitu1oozlz3ibCi6FQ5awCfe/Hy 1Y7etC62aJM3DRnZD9uHkW4= =xdSy -----END PGP SIGNATURE-----
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