Tiller,
In this case, its because dtrace believes there is a jump table:
ghopper:/# dtrace -xdebug -l -n 'pid$target::memcpy:' -c /usr/bin/true
[ ... ]
libdtrace DEBUG: grabbed pid 76537 (cached)
libdtrace DEBUG: creating probe pid76537:libSystem.B.dylib:memcpy:*
libdtrace DEBUG: found a suspected jump table at memcpy:5
libdtrace DEBUG: found a suspected jump table at memcpy:5
libdtrace DEBUG: creating probe pid76537:dyld:memcpy:*
libdtrace DEBUG: found a suspected jump table at memcpy:5
libdtrace DEBUG: found a suspected jump table at memcpy:5
However, even if that wasn't an issue, there isn't really
a "return" from memcpy. Here is libSystem's memcpy stub:
_memcpy:
00006960 movl $0xffff07a0,%eax
00006965 jmp *%eax
00006967 nop
I too have had pretty bad results from flowindent. It may be
that gcc just generates different enough code that more functions
are uninstrumentable on OS X.
I've used something like this as a workaround:
BEGIN
{
spaces = "
";
}
fbt:::entry
/ pid == $1 /
{
printf("%s-> %s\n", stringof(&spaces[60 - (stackdepth * 2)]),
probefunc);
}
fbt:::return
/ pid == $1 /
{
printf("%s<- %s (%d)\n", stringof(&spaces[60 - ((stackdepth-1) *
2)]), probefunc, arg1 );
}
There is probably a better & smarter way to do that, but it was a
quick hack
that got the job done :-).
James M
On Jan 22, 2008, at 12:41 PM, Tiller Beauchamp wrote:
> Hi All,
>
> I have been doing some application tracing on OS X using the pid
> provider to
> trace function entry and returns. I have noticed that some function
> have
> entry probes, but no return probes. In fact, there are not even any
> instruction offset probes, only the entry probe. This is unbalancing
> the
> indent flow graphs (-F). Any idea why this is happening?
>
> Example:
>
> # dtrace -l -p 243 -n 'pid$target::memcpy:'
> Password:
> ID PROVIDER MODULE FUNCTION
> NAME
> 57175 pid243 libSystem.B.dylib memcpy
> entry
> 225226 pid243 dyld
> memcpy entry
> #
>
>
> # dtrace -l -p 1617 -n 'pid$target::RTSPSession_CheckState:'
> ID PROVIDER MODULE FUNCTION
> NAME
> 437436 pid1617 QuickTimeStreaming
> RTSPSession_CheckState entry
> #
>
>
> _______________________________________________
> dtrace-discuss mailing list
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