Middle Ages: The setup( ) Function

The code of the setup( ) assembly language function is placed by the linker immediately after the integrated boot loader of the kernel, that is, at offset 0x200 of the kernel image file. The boot loader can thus easily locate the code and copy it into RAM starting from physical address 0x00090200.

The setup( ) function must initialize the hardware devices in the computer and set up the environment for the execution of the kernel program. Although the BIOS already initialized most hardware devices, Linux does not rely on it but reinitializes the devices in its own manner to enhance portability and robustness. setup( ) essentially performs the following operations: