| 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 |
