CODEWITHSUNDEEP
linux-kernelx86bootloaderu-boot
Amit Singh Tomar
Amit Singh Tomar

Reputation: 8610

What all necessary argument required to boot Linux kernel

I am new to linux kernel and Try to understand booting of Linux kernel from the point it loaded into RAM,I would like to know after Linux image loaded into RAM ,How control is passed to this image ,what all are necessary parameter needs to pass to kernel and can we pass control to linux image without passing any parameter,

I am looking into the UBOOT code with "bootm.c" but unable to understand where control is passed to Linux image,which function is responsible for it.

Is load_zimage() is responsible for passing the control/

Can anybody lead me to right direction or suggest some good tutorials on this particular part of linux booting from x86 archetectiure.

Upvotes: 2

Views: 463

Answers (1)

tian_yufeng
tian_yufeng

Reputation: 1826

I think it depends. Different kinds of CPU architecture, they use different ways to pass information to Linux Kernel. Of course, the Linux Kernel can boot up successfully without bootloader pass information to it, but it need to statically set up correctly in the Linux Kernel, such as root device name, console device, mem size, and also some parameters to enable/disable some features in Linux Kernel.

Why bootloader need to pass various information(parameters) to Linux Kernel, I think it's flexible consideration. Think about this case that it's possible to share one Linux Kernel on two board with same CPU but different peripheral modules.

Let me show some examples that UBoot passes information to Linux Kernel:

(1) For PowerPC cpu, nowadays they use DTB(Device Tree Blob) file to pass more information from UBoot to Linux Kernel. They consider UBoot and DTB as firmware, and in Linux Kernel, they adopt one open firmware(OF) infrastructure. You may know "bootm" command in UBoot, bootm can have three parameters, the first is uImage address, the secondary one is initrd address, and the third one is the dtb address.

(2) Earlier days, they use bootargs to pass information to Linux Kernel. Also you may know there is gd/bd structure in the UBoot, they also can pass information to Linux Kernel. But the information passed in this way is limited, not like DTB.

Hope the above information help you to understand your question.

Upvotes: 2

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