Middle Ages: the setup( ) Function
The code of the setup(
) assembly language function has been placed by the linker 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
essentially the following operations:
In ACPI -compliant systems, it invokes a BIOS routine that builds a table in RAM describing the layout of the system’s physical memory (the table can be seen in the boot kernel messages by looking for the “BIOS-e820” label). In older systems, it invokes a BIOS routine that just returns 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 BIOS supports the Enhanced Disk Drive Services (EDD ), it invokes the proper ...
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