BTFIXUP
  -------
  
  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