Re: corrected: tapset/script information template

["Frank Ch. Eigler" <fche at redhat dot com>]

Hi -

wcohen wrote:

> [...]  I was thinking there are very specific places that one would
> want to start tracing and that it would be controlled by some
> probes, for example turning on the dynamic call graph when entering
> a "function of interest" and turning it off when exiting the same
> function.

By "turning it on/off" do you mean causing kernel- or hardware-level
configuration changes to occur during the execution of probe handlers?
That is, do you imagine the assignment of such variable to expand to
kernel API calls that turn on and off debug/counter hardware?


> I was thinking that instrumentation would be assisted by the debug
> hardware rather than the performance monitoring hardware. [...]  The
> debug also looks a bit easier to use: fewer bits to twiddle and
> easier to find the from/to address. [...]

Is there a standard kernel API for management/abstraction of x86 debug
hardware?  Can you outline the additional logic required to extract
this raw data and turn it into actual call/return trace events?


- FChE

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