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BTFIXUP

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To build new kernels you have to issue "make image". The ready kernel

in ELF format is placed in arch/sparc/boot/image. Explanation is below.

BTFIXUP is a unique feature of Linux/sparc among other architectures,

developed by Jakub Jelinek (I think... Obviously David S. Miller took

part, too). It allows to boot the same kernel at different

sub-architectures, such as sun4c, sun4m, sun4d, where SunOS uses

different kernels. This feature is convinient for people who you move

disks between boxes and for distrution builders.

To function, BTFIXUP must link the kernel "in the draft" first,

analyze the result, write a special stub code based on that, and

build the final kernel with the stub (btfix.o).

Kai Germaschewski improved the build system of the kernel in the 2.5 series

significantly. Unfortunately, the traditional way of running the draft

linking from architecture specific Makefile before the actual linking

by generic Makefile is nearly impossible to support properly in the

new build system. Therefore, the way we integrate BTFIXUP with the

build system was changed in 2.5.40. Now, generic Makefile performs

the draft linking and stores the result in file vmlinux. Architecture

specific post-processing invokes BTFIXUP machinery and final linking

in the same way as other architectures do bootstraps.

Implications of that change are as follows.

1. Hackers must type "make image" now, instead of just "make", in the same

   way as s390 people do now. It is analogous to "make bzImage" on i386.

   This does NOT affect sparc64, you continue to use "make" to build sparc64

   kernels.

2. vmlinux is not the final kernel, so RPM builders have to adjust

   their spec files (if they delivered vmlinux for debugging).

   System.map generated for vmlinux is still valid.

3. Scripts that produce a.out images have to be changed. First, if they

   invoke make, they have to use "make image". Second, they have to pick up

   the new kernel in arch/sparc/boot/image instead of vmlinux.

4. Since we are compliant with Kai's build system now, make -j is permitted.

-- Pete Zaitcev

zaitcev@yahoo.com