fche changed the topic of #systemtap to: http://sourceware.org/systemtap; email systemtap@sourceware.org if answers here not timely, conversations may be logged
<fche>
see [man stapprobes] CONTEXT VARIABLES
<yunhuali>
fche, thanks, let me try
<yunhuali>
fche, I tried to print global variable, jiffies, it works, but print the global variable in module, it is not work
<yunhuali>
probe oneshot { println(@var("kvm_x86_ops"));}, kvm_x86_ops exported by module "KVM"
<fche>
modules are separately linked creatures, it's not so simple there
<fche>
try probe module("kvm").function("... some function ...") { println (@var(...) ) }
<fche>
i.e., to put that variable into scope
<fche>
then you have to arrange to get that function called at some point
<fche>
if you just want the address, you can also #grep /proc/kallsyms fwiw.
<yunhuali>
Yes, if use probe moudle("kvm").function, I need trigger that function
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<fche>
yup
<fche>
at least once. :) it could be anything; the stap module could exit at that point if this is all the info you were after
<fche>
or the probe could be disabled after that info is found (use an global found_p; probe kvm.foo if (!found_p) { found_p = 1 } kind of thing
<fche>
(see "arming condition" in [man stap] PROBES)
<yunhuali>
thanks fche,
<yunhuali>
using @var("kvm_x86_ops"), I can print the value, Do you know how to print each member?
<yunhuali>
something like $$parms$
<yunhuali>
it will print each member of a structure
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<fche>
@var("kvm_x86_ops")$
<fche>
or probably even $kvm_x86_ops$ or $$
<fche>
i.e., $ composes with @var() or @cast()
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<sean_>
Hi all experts, I encountered an error when using whythefail.stp