Re: State of the new config & build system

[Kai Germaschewski <kai@tp1.ruhr-uni-bochum.de>]

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[CC trimmed]

On Sat, 29 Dec 2001, Keith Owens wrote:

> [...] 
> Auto detection of changed commands/flags
> 
>   That was a decent fix for part of the problem, but it did not address
>   tracking user commands nor host compiles.  It did not allow for
>   separate source and object trees, for read only source trees, nor did
>   it handle the more esoteric cases like modules being built from
>   multiple directories.

Some people asked for what my patch looked like, so I resurrected it. I 
moved it to 2.5.2-pre3. As it caused lots of rejects (maintaining kbuild 
is a non-trivial task, isn't it, Keith?), I only fixed the problems for my 
.config. So the attached patch will break with most .configs. However, 
people who want to take a look can take my .config and play with that - 
it's strictly proof-of-concept only. 
(The breakage is easily fixable, it's just quite a bit of mostly trivial 
work).

And yes, it doesn't fix the separate source / objects tree issue. But IMO
that's not a problem that needs to be fixed, it's an additional feature
which I didn't even try to attack (it may be possible to get there with
VPATH, though).

To try it, patch your kernel,

mv ../config-2.5 .config
make oldconfig
make # builds bzImage and modules

A subsequent make will only rebuild what's needed:

[kai@vaio linux-2.5.2-pre3.kbuild]$ time make
make -f Makefile.build boot
make[1]: Entering directory 
`/home/kai/kernel/v2.5/linux-2.5.2-pre3.kbuild'
Generating include/linux/compile.h ...
Preprocessing arch/i386/boot/bsetup.s ...
Assembling (AS) arch/i386/boot/bsetup.o ...
Linking arch/i386/boot/bsetup ...
Compiling init/version.o ...
Linking vmlinux ...
Generating System.map ...
Building arch/i386/boot/compressed/piggy.o
Linking arch/i386/boot/compressed/bvmlinux
Copying to arch/i386/boot/compressed/bvmlinux.out
Building arch/i386/boot/bzImage
Root device is (3, 2)
Boot sector 512 bytes.
Setup is 4764 bytes.
System is 715 kB
make[1]: Leaving directory `/home/kai/kernel/v2.5/linux-2.5.2-pre3.kbuild'

real    0m10.230s
user    0m8.510s
sys     0m1.050s

For each make, compile.h is updated, thus causing init/version.o to be 
recompiled and vmlinux to be relinked. - I kept the behavior of the 
current kbuild. Not regenerating compile.h will give:

[kai@vaio linux-2.5.2-pre3.kbuild]$ time make
make -f Makefile.build boot
make[1]: Entering directory 
`/home/kai/kernel/v2.5/linux-2.5.2-pre3.kbuild'
make[1]: Nothing to be done for `boot'.
make[1]: Leaving directory `/home/kai/kernel/v2.5/linux-2.5.2-pre3.kbuild'

real    0m7.155s
user    0m6.790s
sys     0m0.290s


As an example, change one file:

[kai@vaio linux-2.5.2-pre3.kbuild]$ touch drivers/isdn/hisax/callc.c
[kai@vaio linux-2.5.2-pre3.kbuild]$ time make
make -f Makefile.build boot
make[1]: Entering directory 
`/home/kai/kernel/v2.5/linux-2.5.2-pre3.kbuild'
Compiling drivers/isdn/hisax/callc.o ...
Linking module drivers/isdn/hisax/hisax.o ...
make[1]: Leaving directory `/home/kai/kernel/v2.5/linux-2.5.2-pre3.kbuild'

real    0m9.433s
user    0m8.780s
sys     0m0.520s


$ diffstat pp-kbuild-2.5.2-pre3

 00_version                               |    5 
 Documentation/DocBook/Makefile           |    3 
 Makefile                                 |  507 +++----------------------
 Makefile.build                           |  460 ++++++++++++++++++++++
 Makefile.config                          |   32 +
 Makefile.end                             |   37 +
 Makefile.vars                            |  130 ++++++
 Rules.make                               |  326 ----------------
 arch/i386/Makefile                       |   70 ---
 [...]
 scripts/Makefile                         |   23 -
 scripts/fix_dep.c                        |  406 ++++++++++++++++++++
 scripts/mkdep.c                          |  628 -------------------------------
 169 files changed, 1849 insertions(+), 3107 deletions(-)


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