dtracing static symbols

[Mark Johnston]

On Wed, Mar 12, 2014 at 12:50 AM, Daniel O'Connor <doconnor at gsoft.com.au> wrote:
>
> On 12 Mar 2014, at 15:15, Prashanth Kumar <pra_udupi at 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)?

I'd suggest updating to 9-STABLE. There have been quite a few fixes to
fasttrap and libproc since 9.2.

-Mark

>
> THanks.
>
>> --------------------------------------------
>> On Wed, 12/3/14, Daniel O'Connor <doconnor at gsoft.com.au> wrote:
>>
>> Subject: Re: dtracing static symbols
>> To: "Robert Mustacchi" <rm at joyent.com>
>> Cc: freebsd-dtrace at freebsd.org
>> Date: Wednesday, 12 March, 2014, 2:54 AM
>>
>>
>> On 12 Mar 2014, at 2:30, Robert Mustacchi <rm at 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 at 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
>>
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>
> --
> 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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