fche changed the topic of #systemtap to: http://sourceware.org/systemtap; email systemtap@sourceware.org if answers here not timely, conversations may be logged
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<toothe> hi all!
<toothe> JUST learned about systemtap, interested in using it...
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<toothe> I am going through the systemtap documentation.
<toothe> I know what I want to do, but not quite sure how to do it.
<toothe> I want to see every function call done inside of this function: module("rtl_pci").function("rtl_pci_probe@/build/linux-W6HB68/linux-4.4.0/drivers/net/wireless/realtek/rtlwifi/pci.c:2172")
<toothe> by "every" maybe 4 deep
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<toothe> oh, probefunc()
<toothe> okay - second problem. Why are some function calls blacklisted?
<toothe> okay awesome - so I have my stp script begin/end properly. Within the probe I setup, is there a way to monitor what is happening within the function of choice?
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<fche> toothe, use .statement() rather than .function() probes to examine the internals of functions
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<toothe> fche: that's interesting ,thanks!
<toothe> also, why are there blacklisted functions? I don't fully understand that.
<fche> hi toothe
<fche> blacklisted functions (in kernel space) are there because the kernel cannot completely analyze itself well enough to put kprobes at all conceivable spots
<fche> stap blacklists some functions for historical reasons - generally more conservative than the kernel, but for the same kinds of reasons
<toothe> i see
<toothe> can I disable the blacklist for a specific function?
<toothe> so, I am doing a printf("%s\n", probefunc() );. I noticed that a function is called an unusual number of times within the kernel.
<toothe> I initially thought for some reason the function is merely being called multiple times, but now I see that the parameters for the function differ.
<toothe> Maybe I"m using the wrong code, but that strikes me as very odd.
<toothe> am I making a mistake? Is there a reason a probe name is being repeated?
<fche> the kernel blacklist is permanent. the systemtap blacklist can be suppressed with 'stap -g ...'
<fche> re. unusual number of times ... that could be lots of things, like an inlined function
<fche> depends on details
<toothe> ahh...
<toothe> yes, I do think that's being done.
<toothe> I'm still learning the tool.
<toothe> is there a way to suppress that and/or display the inline function names?
<fche> and the tool gives you rather low level view into the system (and it's an imperfect view - we're also subject to the whims of the kernel & the compiler, and the occasonal stap bug)
<fche> kernel.function("...").call <-- excludes .inline
<fche> see [man stapprobes]
<toothe> I am using a module, so module("rtl8188ee").function("*")
<fche> so .call at the end
<toothe> but, the .call likely does the exclusino...reading manual...
<toothe> hm..dont' have that manual
<fche> man stapprobes doesn't give you anything? odd
<toothe> there it goes, thanks! (the .call method)
<toothe> and no, it doesn't
<toothe> I'm on Ubuntu, maybe tey didn't install the manual pages?
<fche> they should be spanked with a wet noodle
<toothe> i thought it was slapped around with a large troute?
<fche> ah yes, the fish-slapping song
<toothe> its from mIRC
<toothe> british humor
<toothe> presentation with an absolutely straight face
<fche> the best
<toothe> so, my target functino is this: pci_bus_write_config_byte
<toothe> but, I'm not certain I can get a trace against it
<toothe> maybe i can trace the inline function?
<toothe> my goal is this:
<toothe> i am trying to figure out what's data is sent to this PCIe card.
<toothe> I only see 4 explicit instances in this particular function.
<toothe> but, I am trying to see the others.
<fche> tracing the inline function is probably one way, but it will be imperfect
<fche> you could try a statement probe at the site(s) you identify where the inline function is -called-
<toothe> I think i found the issue!
<toothe> but...my tset server didn't come back on after a reboot...gotta wai til I get home now :)
<toothe> Thank you for your help!
<fche> np
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