DTrace syscall provider - please test/comment

[Jeff Rizzo <riz%NetBSD.org@localhost>]

I've been looking at our DTrace code in my spare time recently, and I'd 
like to get us closer to the point where generally available D scripts 
"just work" on NetBSD.  One of the big missing pieces right now (by no 
means the *only* missing piece) is the "syscall" provider for tracing 
system calls.

Here's the latest patch, meant to be applied with "patch -p0" in 
/usr/src (or whereever):

http://www.tastylime.net/netbsd/systrace.diff

To test it, make sure you're set up for dtrace:

http://wiki.netbsd.org/how_to_enable_and_run_dtrace/

You'll need to rebuild both the kernel and all the dtrace kmods with 
these patches.  Something like this to rebuild the whole system:

./build.sh -U -O /dtracetest/obj -T /dtracetest/tools -m amd64 -j8 -V 
MKDTRACE=yes release

The kernel config I'm using is:

#
# Kernel with dtrace enabled.

include "arch/amd64/conf/GENERIC"

options         KDTRACE_HOOKS
options         DDB_ONPANIC=1
makeoptions     DEBUG="-g"



Some notes:

- I've only tested this on amd64.  It *should* work on i386 as well.

- Only native syscalls will be traced.  I could use some help figuring 
out the best way to implement tracing of emulated syscalls (netbsd32, 
linux, linux32, etc) given the fact that those are meant to be loadable 
modules

- The name "systrace" was not chosen by me; it's from the original 
Solaris code.  Yes, it conflicts with the removed "systrace" feature.  
No, it doesn't have anything to do with that systrace.  I would like to 
rename all the dtrace providers (fbt, sdt, profile, systrace) to 
"dtrace_*" names at some point, but not until after these changes are in.

- at some point, I would like to make "MKDTRACE=yes" the default on 
systems that support DTrace (amd64 and i386 at the moment), without 
including KDTRACE_HOOKS in the kernel config necessarily.  Thoughts?

Please let me know what you think.  Constructive suggestions welcome.

+j