fche changed the topic of #systemtap to: http://sourceware.org/systemtap; email systemtap@sourceware.org if answers here not timely, conversations may be logged
<bendlas> mhh, process.insn tells me `semantic error: process probes not available without kernel CONFIG_UTRACE`, even though process.function works and CONFIG_UTRACE seems to be gone from kernel 4.7
<bendlas> is there a UPROBE based variant for process.insn
<bendlas> ?
<fche> bendlas, sorry, no. that facility was not ported into the new uprobes.
<fche> such probes work only on rhel6 era kernels
<bendlas> pity
<bendlas> is somebody working on this?
<bendlas> or can I use uprobes directly, somehow?
<fche> uprobes are for probes placed at particular addresses
<fche> the .insn probes were for single-stepping
<bendlas> so I'll have to run binaries without debug info in my own debugger?
<bendlas> what about this dyninst business?
<fche> ok hold on, you said process.insn last
<fche> process probes (CONFIG_UPROBES) are indeed in 4.7 era kernels for most architectures
<fche> that's non-process.insn - just process.function / .statement / that sort of thing
<fche> ah yes, and that's working for you
<fche> sorry, it's late here, I keep misreading you :)
<fche> ok so for .insn single stepping, for real, yeah there seem to be no kernel facilities for that at the moment
<fche> dyninst - that can -probably- do the job, though I don't think we have a systemtap front-end for that
<fche> gdb / gdbserver can definitely do the job, but it's a whole different feel/infrastructure
<bendlas> is dyninst similar to valgrind?
<fche> kind of sort of - dyninst is a library with an api, whereas valgrind is a full tool
<fche> you can think of valgrind's internal tools operating against an api that's sort of similar to dyninst's
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<bendlas> so, systemtap can use dyninst as a backend if there is no kernel support, but there are no probe types?
<fche> there are certainly probe types for stap --runtime=dyninst; specifically function/statement probes
<fche> just no equivalent for old-school rhel5/5 utrace process.insn single-stepping.
<fche> chances are systemtap-dyninst could support a process.insn probe point. you could more formally register your interest in that by opening a bug/rfe against systemtap for thsi
<bendlas> ok, thanks for the info
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<irker110> systemtap: mcermak systemtap.git:refs/heads/master * release-3.0-251-ga10bdce / staptree.cxx: Let the @variance pretty printer show the bit_shift if specified. http://tinyurl.com/gpkgws2
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<jistone> dyninst process.insn -- just musing that should be *technically* possible, but I shudder to think how that would actually work
<fche> there may be a ProcessControl API for that
<jistone> PTRACE_SINGLE_STEP, notifies mutator, mutator rewrite regs to run a callback in the mutatee, PTRACE_CONT, notifies that callback finished, GOTO 10
<fche> it'd be slow as heck
<jistone> thus I shudder
<fche> but ... the only game in town in modern kernel land
<fche> (and probably still faster than gdb)
<jistone> OR we could do a massive process rewrite, literally instrumenting our calls after EVERY instruction
<jistone> that would at least stay in process
<fche> and take apprx. a year to insert it all? :)
<fche> well, easy enough to try
<jistone> I think you'd be much better off with valgrind/pin/etc
<fche> imagine someone was fond of the systemtap ecosystem
<fche> don't laugh now, such people exist :-)
<jistone> we are a hammer, and that's not a nail
<fche> how much dyninst performance sloth might they be willing to accept to do insn-by-insn tracing of (say) a function?
<fche> or a module?
<fche> it'd be nice to have at least a little bit of data to offer the analysis
<jistone> well, it doesn't hurt to have an RFE
<fche> yeah. can't promise prompt action.
<jistone> btw, what is this .insn.block? how does that work?
<fche> it set another processor status bit to break on branches
<fche> not on insns
<fche> dunno if ptrace(2) has an equialent
<jistone> huh, I didn't know that existed
<jistone> I don't think that's in ptrace
<fche> (but anyway it'd be nice to teach stap to interface to branch-record type tracing in the kernel)
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<irker747> systemtap: dsmith systemtap.git:refs/heads/dsmith/python * release-3.0-247-gd7f07c2 / Makefile.in config.in configure configure.ac doc/Makefile.in doc/SystemTap_Tapset_Reference/Makefile.in doc/beginners/Makefile.in java/Makefile.in man/Makefile.in man/cs/Makefile.in python/Makefile.am python/Makefile.in stapdyn/Makefile.in staprun/Makefile.in tapset-python.cxx: Renamed/added '--with-python2-probes' and '--with-python3-probes'
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