Is arch/x86/boot/main.c main obsolete?

[Aruna Hewapathirane]

On Sat, Jun 25, 2022 at 7:35 PM ebashinskii <ebashinskii at proton.me> wrote:

> CPU: Intel x86 KabyLake. I'm using 5.17 Kernel built from upstream and
> GRUB 2.04
>
> When debugging the kernel initialization process I found out that there is
> a function *void main(void)* in the source file *arch/x86/boot/main.c* (source
> link:
> https://elixir.bootlin.com/linux/v5.17/source/arch/x86/boot/main.c#L134) which
> seems to be the entry point which the boot loader is supposed to jump into.
>
> But *objdump*-ing the Kernel image shows that there is no such symbol as
> *main*. GDB attached to QEMU does not know about this symbol either.
>
> The earliest stage of Kernel Initialization I could manage to catch with
> GDB is *x86_64_start_kernel* (source link:
> https://elixir.bootlin.com/linux/v5.17/source/arch/x86/kernel/head64.c#L467
> )
>
> The question is what function GRUB actually jump into passing control to
> the Kernel code and what is the purpose of *arch/x86/boot/main.c::main*?
>

This should answer most of the questions you may have about the kernel boot
process:
https://0xax.gitbooks.io/linux-insides/content/Booting/

:-)



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