Re: [RFC][PATCH 2/2] tracing/x86: basic implementation of syscalltracing for x86-64

[Ingo Molnar]

* Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx> wrote:

> * Ingo Molnar (mingo@xxxxxxx) wrote:
> > 
> > * Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx> wrote:
> > 
> > > * Frederic Weisbecker (fweisbec@xxxxxxxxx) wrote:
> > >
> > > > Provide the ptrace hooks and arch specific syscall numbers 
> > > > to ftrace arch indepedant syscall numbers. For now it only 
> > > > supports 4 syscalls to provide an example.
> > > > 
> > > 
> > > Hi Frederic,
> > > 
> > > I already have the equivalent TIF_KERNEL_TRACE flag in my 
> > > LTTng tree added to every Linux architecture. You might want 
> > > to re-use this work rather than re-doing this. I don't mind 
> > > changing the flag name.
> > 
> > Yeah. Note that the TIF bits are just one part - there are other 
> > bits needed for HAVE_FTRACE_SYSCALLS arch support.
> > 
> > Also, i'd eventually expect the TIF bits to be converted to a 
> > tracehook callback, not spread it to other architectures.
> > 
> 
> The nice part about the TIF bit is that it permits adding this 
> syscall tracing feature without increasing the size of the 
> thread_info struct nor adding any extra tests in entry.S. Does 
> the tracehook callback have these features ?

yes. Tracehook just factors out common interfacing points - with 
one specific implementation for now: ptrace. For syscall tracing 
that means it wraps TIF_SYSCALL_TRACE in essence.

	Ingo
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