Date: Wed, 12 Mar 2014 12:45:42 +0800 (SGT) From: Prashanth Kumar <pra_udupi@yahoo.co.in> To: Robert Mustacchi <rm@joyent.com>, Daniel O'Connor <doconnor@gsoft.com.au> Cc: freebsd-dtrace@freebsd.org Subject: Re: dtracing static symbols Message-ID: <1394599542.80116.YahooMailBasic@web192602.mail.sg3.yahoo.com> In-Reply-To: <4DCD0848-F635-4CAE-B109-9941395B6AB8@gsoft.com.au>
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If you run=20
# env DTRACE_DEBUG=3D1 dtrace -Ppid\$target -l -c ./static
you will notice that lot of probe creation will fail, also no probes are cr=
eated for instruction offsets.
you will have to update the libproc library and fasttrap code to trace =
all the=20
functions.=20
--------------------------------------------
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
=20
=20
On 12 Mar 2014, at 2:30, Robert Mustacchi <rm@joyent.com>
wrote:
> On 03/10/2014 10:34 PM, Daniel O'Connor wrote:
>>=20
>> 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?
>>=20
>> Unfortunately the static symbols don't show up in
the symbol table (as shown by nm).
>>=20
>> Is there a compile or link flag which will change
that?
>=20
> 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.
=20
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
=20
I also added the noinline attribute for good measure.
=20
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..
=20
>> (I'm not sure what the various numbers mean)
>=20
> The pid provider can instrument any instruction in a
function, those are
> the instruction offsets.
=20
Ahh, thanks.
=20
--
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."
=A0 -- Andrew Tanenbaum
GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20
7B3F CE8C
=20
=20
=20
=20
=20
=20
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