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

[Serge E. Hallyn]

Quoting Matt Helsley (matthltc at us.ibm.com):
> 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.

Perhaps we need more discussion on how we all compile this stuff...

On my one system, I don't have kernel sources on my target machine at
all.  Every time there is a meaningful change of headers I do
	scp include/linux/checkpoint* root at target:/usr/include/linux
	scp arch/s390/include/asm/checkpoint_hdr.h root at target:/usr/include/asm/

On my kvm partition, I can't recall whether make headers_install worked,
or whether I manually copied the checkpoint headers in.  I basically never
compile ckptinfo precisely because it requires finagling with KERNELSRC
and then doesn't compile anyway...

-serge
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