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SubjectRe: [GIT PULL] tracing/kprobes: Add dynamic tracepoints + instruction decoder
Frederic Weisbecker wrote:
> On Thu, Aug 27, 2009 at 11:00:38AM -0400, Masami Hiramatsu wrote:
>> Frederic Weisbecker wrote:
>>> Ingo,
>>> This is the kprobes tracing pile of patches. I've tested it
>>> successfully by setting some kprobes through debugfs by hand.
>>> It brings no known regressions.
>>> However, the stress test provided by Masami have revealed some
>>> unstable points. Some symbols are unsafe to probe and raise
>>> probing recursion.
>>> I've added a tiny patch in the series that helps identifying the
>>> kprobe that has raised such situation.
>>> For example it has learned me today that it's unsafe to trace
>>> ret_from_exception() (obviously: it's on the int 3 handler path).
>> Thank you, Frederic.
>> I'm currently fixing those problems on x86-64 (on kvm).
>> I'll also check it on x86-32, and fix it.
>> Thanks
> Cool.
> Don't hesitate to interate through small patches that fix these
> sites.
> So that I can continue to test it over time and report you what I find,
> may be I can try to fix some of them too.
> I haven't fixed ret_from_exception because I wasn't sure about the
> right thing to do: putting it in the kprobes section or blacklist its
> name. It's a bit more delicate to put assembly code into sections so... :)

It depends on implementation, but I think blacklist is the last resort. :)
AFAIK, some assembly codes are already pushed into kprobes section.

Thank you,

Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division


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