Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | BTFIXUP |
2 | ------- | |
3 | ||
4 | To build new kernels you have to issue "make image". The ready kernel | |
5 | in ELF format is placed in arch/sparc/boot/image. Explanation is below. | |
6 | ||
7 | BTFIXUP is a unique feature of Linux/sparc among other architectures, | |
8 | developed by Jakub Jelinek (I think... Obviously David S. Miller took | |
9 | part, too). It allows to boot the same kernel at different | |
10 | sub-architectures, such as sun4c, sun4m, sun4d, where SunOS uses | |
11 | different kernels. This feature is convinient for people who you move | |
12 | disks between boxes and for distrution builders. | |
13 | ||
14 | To function, BTFIXUP must link the kernel "in the draft" first, | |
15 | analyze the result, write a special stub code based on that, and | |
16 | build the final kernel with the stub (btfix.o). | |
17 | ||
18 | Kai Germaschewski improved the build system of the kernel in the 2.5 series | |
19 | significantly. Unfortunately, the traditional way of running the draft | |
20 | linking from architecture specific Makefile before the actual linking | |
21 | by generic Makefile is nearly impossible to support properly in the | |
22 | new build system. Therefore, the way we integrate BTFIXUP with the | |
23 | build system was changed in 2.5.40. Now, generic Makefile performs | |
24 | the draft linking and stores the result in file vmlinux. Architecture | |
25 | specific post-processing invokes BTFIXUP machinery and final linking | |
26 | in the same way as other architectures do bootstraps. | |
27 | ||
28 | Implications of that change are as follows. | |
29 | ||
30 | 1. Hackers must type "make image" now, instead of just "make", in the same | |
31 | way as s390 people do now. It is analogous to "make bzImage" on i386. | |
32 | This does NOT affect sparc64, you continue to use "make" to build sparc64 | |
33 | kernels. | |
34 | ||
35 | 2. vmlinux is not the final kernel, so RPM builders have to adjust | |
36 | their spec files (if they delivered vmlinux for debugging). | |
37 | System.map generated for vmlinux is still valid. | |
38 | ||
39 | 3. Scripts that produce a.out images have to be changed. First, if they | |
40 | invoke make, they have to use "make image". Second, they have to pick up | |
41 | the new kernel in arch/sparc/boot/image instead of vmlinux. | |
42 | ||
43 | 4. Since we are compliant with Kai's build system now, make -j is permitted. | |
44 | ||
45 | -- Pete Zaitcev | |
46 | zaitcev@yahoo.com |