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 therefore 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( )
performs the following operations:
Invokes a BIOS procedure to find out the amount of RAM available in the system.
Sets the keyboard repeat delay and rate. (When the user keeps a key pressed past a certain amount of time, the keyboard device sends the corresponding keycode over and over to the CPU.)
Initializes the video adapter card.
Reinitializes the disk controller and determines the hard disk parameters.
Checks for an IBM Micro Channel bus (MCA).
Checks for a PS/2 pointing device (bus mouse).
Checks for Advanced Power Management (APM) BIOS support.
If the kernel image was loaded low in RAM (at physical address
0x00010000
), moves it to physical address0x00001000
. Conversely, if the kernel image was loaded high in RAM, the function does not move it. This step is necessary because to be able to store the kernel image on a floppy ...
Get Understanding the Linux Kernel, Second Edition now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.