Date and Version
The original version of this paper was started on the 26th of August 2003; the kernel code quoted refered to version 2.4.22 and the binutils utility came from binutils-1.4. This document was rechecked on the 11th of October, 2006. At that time small modifications were made to the text, all code was re-checked, and all output re-generated from the new code. The kernel being used was 2.6.18, binutils 18.104.22.168.2.2, and gcc 4.0.0.
All kernel files that are referenced in this paper are specifed by a path name relative to the kernel's root directory. For example the setup.c file for the PowerPC architecture would be given as: arch/ppc/kernel/setup.c. A specific function (e.g. early_init) within a given file is expressed as arch/ppc/kernel/setup.c:early_init() regardless of what parameters it accepts (if any) and what it returns (if anything).
As far as I know, this mechanism is not architecture-dependent. I actually found it while tracing through the boot process of the PowerPC architecture, but my code tests were performed on an x86-based machine. The code that makes this work is in the kernel's init/ directory, which (as is my understanding), contains initialization code which is used by all architectures. The ability to use this mechanism depends more on specific support given by the GNU tools and the ELF executable format rather than architecture-specific support.
"objdump -t" output format
I often dump the symbols of a file using objdump -t. I can't seem to easily locate any documentation on the output format so I've included some quick notes here. A typical use of this tool would look something like the following:
[trevor]$ objdump -t add.o add.o: file format elf32-i386 SYMBOL TABLE: 00000000 l df *ABS* 00000000 add.c 00000000 l d .text 00000000 00000000 l d .data 00000000 00000000 l d .bss 00000000 00000000 l d .comment 00000000 00000000 g F .text 0000000b add
The flags which are described above are part of a larger set of symbols and attributes which are defined in bfd/bfd.h. The entire set of flags (or attributes) and their meanings are given below. NOTE: objdump -t doesn't try to display the values of all the possible flags, just the ones mentioned above.