Regd head.S

Hi,

Eager to know the use of head.S file. As far i understand by looking into the head.S file, it does the following -

- head.S contains the 32-bit startup code.

- Clear BSS

- Do the decompression, and jump to the new kernel

But, how head.S file is related with the bootloader and where does it lie in the memory ? It looks like head.S does the decompression and gives the control to the new kernel. It looks like it does the functionality of the bootloader. Further, what is the use of the startup code in head.S file ? Any ideas ?

Thx in advans, Karthik Balaguru

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karthikbalaguru
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I got some interesting links that clarified me of the above queries.

It seems that head.S is part of the kernel and acts as one of the initial part of the kernel. From the linux HOW-TO html's name 'Kernel_head.html', i think that it can also be termed as Kernel Head. The head.S is used along with the 'main C routine' after decompression to initialize all parts of the kernel which inturn will show lot of messages and finally the 'init' process or the first 'linuxrc' variant on an initial RAM disk will be started.

Bootloaders do not give the control to the head.S in first hand. It seems that the control is given directly to setup.S in first hand. Bootloaders should load bzImage into memory and setup "real-mode kernel header", esp. type_of_loader, then pass control to bsetup/setup.S directly. setup.S is responsible for getting the system data from the BIOS and putting them into appropriate places in system memory.

bootsect.S comes into picture only if it has to be done via diskette.

The below link clearly states the parts of bootloader and the parts of the linux kernel.

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Other references -

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Lemme know if you have some other thoughts.

Karthik Balaguru

Reply to
karthikbalaguru

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