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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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On 12 Mar 2014, at 15:15, Prashanth Kumar <pra_udupi@yahoo.co.in> wrote:
> 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 created for instruction offsets.
>    you will have to update the libproc library and fasttrap code to =
trace all the=20
> functions.=20

I don't really care about the function offsets, just static functions.=20=


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:
>=20
> 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."
>   -- Andrew Tanenbaum
> GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20
> 7B3F CE8C
>=20
>=20
>=20
>=20
>=20
>=20
>=20
>=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."
  -- Andrew Tanenbaum
GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C







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