[Devel] Re: [PATCH] user-cr: Extract headers from kernel source tree.

[Matt Helsley]

On Sat, Oct 03, 2009 at 04:40:41PM -0500, Nathan Lynch wrote:
> On Sat, 2009-10-03 at 00:20 -0700, Matt Helsley wrote:
> > Sanitize kernel headers for userspace by extracting non-__KERNEL__
> > portions of the various checkpoint headers and placing them in a
> > similar organization of userspace headers.
> > 
> > The script is run from the top level of the user-cr source tree like:
> > 
> > 	./scripts/extract-headers.sh -s <path-to-kern-source> -o ./include
> > 
> > The patch includes a copy of the auto-generated headers and adjusts
> > the user-cr programs to use them.
> 
> I appreciate the effort put into this, but why isn't the
> "headers_install" target of the kernel Makefile sufficient to produce
> headers that are usable by userspace?  So far as I know, other projects
> with complex kernel/user interfaces (e.g. kvm) haven't had to resort to
> special-purpose programs like this.

This script trims down the kernel headers from 4MB to 62k and places them
in the user-cr source tree. That means it's reasonable to just copy user-cr
anywhere and rebuild -- no need to copy your kernel headers seperately
and then fuss with KERNELSRC etc.

At one point this patch also moved all arch-detection out of the Makefile
and left it to cpp. That's no longer true now that we have the bits
necessary for clone_with_pids. A seperate patch could finish that though.
Removing arch-detection in the Makefile might make cross-compiling easier.

That said, it's not meant to replace /usr/include headers. When the
syscall numbers make it into /usr/include, for instance, the part of this
script that gathers them will be obsolete.

Lastly, it may be useful for anyone who wants to compare c/r headers to
build checkpoint image translation tools. It should be alot easier to
see the relevant changes...

So it's useful for me. Perhaps I should make it optional and toss it into
contrib/ instead.

Cheers,
	-Matt Helsley

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