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(multiboot.info)Example OS code

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Example OS code
===============

   In this distribution, the example Multiboot kernel `kernel' is
included. The kernel just prints out the Multiboot information structure
on the screen, so you can make use of the kernel to test a
Multiboot-compliant boot loader and for reference to how to implement a
Multiboot kernel. The source files can be found under the directory
`docs' in the GRUB distribution.

   The kernel `kernel' consists of only three files: `boot.S',
`kernel.c' and `multiboot.h'. The assembly source `boot.S' is written
in GAS (Note: GNU assembler.), and contains the Multiboot
information structure to comply with the specification. When a
Multiboot-compliant boot loader loads and execute it, it initialize the
stack pointer and `EFLAGS', and then call the function `cmain' defined
in `kernel.c'. If `cmain' returns to the callee, then it shows a
message to inform the user of the halt state and stops forever until
you push the reset key. The file `kernel.c' contains the function
`cmain', which checks if the magic number passed by the boot loader is
valid and so on, and some functions to print messages on the screen.
The file `multiboot.h' defines some macros, such as the magic number
for the Multiboot header, the Multiboot header structure and the
Multiboot information structure.

multiboot.h

boot.S

kernel.c

Other Multiboot kernels