Re: Linus's include file strategy redux

[miquels@traveler.cistron-office.nl (Miquel van Smoorenburg)]

In article <NBBBJGOOMDFADJDGDCPHAENMCJAA.law@sgi.com>,
LA Walsh <law@sgi.com> wrote:
>It was at that
>point, the externally compiled module "barfed", because like many modules,
>it expected, like many externally compiled modules, that it could simply
>access all of it's needed files through /usr/include/linux which it gets
>by putting /usr/include in it's path.  I've seen commercial modules like
>vmware's kernel modules use a similar system where they expect
>/usr/include/linux to contain or point to headers for the currently running
>kernel.

vmware asks you nicely

where are the running kernels include files [/usr/src/linux/include" >

And then compiles the modules with -I/path/to/include/files

In fact, the 2.2.18 kernel already puts a 'build' symlink in
/lib/modules/`uname -r` that points to the kernel source,
which should be sufficient to solve this problem.. almost.

It doesn't tell you the specific flags used to compile the kernel,
such as -m486 -DCPU=686

>	So at that point it becomes what we should name it under
>/usr/include/linux.  Should it be:
>1) "/usr/include/linux/sys" (my preference)

/usr should be static. It could be a read-only NFS mount.
Putting system dependant configuration info here (which a
/usr/include/linux/sys symlink *is*) is wrong.

I think /lib/modules/`uname -r`/ should contain a script that
reproduces the CFLAGS used to compile the kernel. That way,
you not only get the correct -I/path/to/kernel/include but
the other compile-time flags (like -m486 etc) as well.

# sh /lib/modules/`uname -r`/kconfig --cflags
-D__KERNEL__ -I/usr/src/linux-2.2.18pre24/include -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer -fno-strict-aliasing -pipe -fno-strength-reduce -m486 -malign-loops=2 -malign-jumps=2 -malign-functions=2 -DCPU=686

Standard module Makefile that will _always_ work:

#! /usr/bin/make -f

CC = $(shell /lib/modules/`uname -r`/kconfig --cc)
CFLAGS = $(shell /lib/modules/`uname -r`/kconfig --cflags)

module.o:
	$(CC) $(CFLAGS) -c module.c

Flags could be:

--check		Consistency check - are the header files there and
		does include/linux/version.h match
--cc		Outputs the CC variable used to compile the kernel
		(important now that we have gcc, kgcc, gcc272)
--arch		Outputs the ARCH variable
--cflags	Outputs the CFLAGS
--include-path	Outputs just the path to the include files

Generating and installing this 'kconfig' script as part of
"make modules_install" is trivial, and would solve all problems.
Well as far as I can see, ofcourse, I might have missed something..

Mike.
-- 
RAND USR 16514
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