Messages in this thread | | | Date | Mon, 14 Sep 2009 17:10:33 -0400 | From | Masami Hiramatsu <> | Subject | Re: [PATCH tracing/kprobes 0/7] tracing/kprobes: kprobe-based event tracer update and perf support |
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Frederic Weisbecker wrote: > On Mon, Sep 14, 2009 at 01:16:13PM -0400, Masami Hiramatsu wrote: >> Frederic Weisbecker wrote: >>> On Fri, Sep 11, 2009 at 12:03:30PM -0400, Masami Hiramatsu wrote: >>>> Frederic Weisbecker wrote: >>>>> May be another step in the todo-list that would be nice: define the format >>>>> for a type. Like it's done from ftrace events. >>>> >>>> Thanks! >>>> >>>> BTW, I'm not sure what the type means. Each event already has its own >>>> event ID and event_call. Could you tell me which part of ftrace I should >>>> refer to ? >>>> >>> >>> >>> Actually I meant the format for a field. >>> Say you define filename=arg1, it would be nice to have >>> >>> print "%s", filename >>> >>> in the format file. >> >> Ah, indeed. It is better to support 'type' casting for each argument. >> I think type casting can be done as below syntax. >> >> NAME=ARG:TYPE >> e.g. >> jiffies64=@jiffies64:u64 >> message=%ax:str >> > > > Yeah looks good! > > > >>> Hmm, now that I think about it, we can't dereference an array...for now :-) >> >> :-) >> BTW, currently, an entry of the array can be shown, e.g. +10(sa). >> Hmm, for more complex dereference(e.g. accessing a->b[a->c]), it might need >> another dereferencing syntax(e.g. "sa[16][sa[8]]"), or >> just allow to use braces(e.g. "+(+8(sa))(+16(sa))"). > > > Well, that may be too much complexity. > I guess if we want multi level dereference, say you want a->b->c > it should be sufficient to probe the point where b->c gets it's > value (if any). > > But it would be nice to fetch a range: sa[begin:end] > Or at least just giving the length of the range.
Hmm, I think it is better to treat the range as a type, because we don't know how to express each entry without the type.
NAME=ARG:TYPE[LEN] e.g. regs=sa:u64[16]
Thank you,
-- Masami Hiramatsu
Software Engineer Hitachi Computer Products (America), Inc. Software Solutions Division
e-mail: mhiramat@redhat.com
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