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From: Julian Elischer <julian@elischer.org>
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To: Aryeh Friedman <aryeh.friedman@gmail.com>
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Cc: Attilio Rao <attilio@freebsd.org>, freebsd-hackers@freebsd.org
Subject: Re: a strange/stupid question
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Aryeh Friedman wrote:
> On 11/24/07, Attilio Rao <attilio@freebsd.org> wrote:
>> 2007/11/24, Aryeh Friedman <aryeh.friedman@gmail.com>:
>>> Where do I find the main() [and/or other entery point] for the
>>> kernel.... I tend to understand stuff better if I follow the flow of
>>> exec from the start
>> It is highly MD.
>> For IA32 it is in i386/i386/locore.s::btext
> 
> For AMD64 I assume something close to that...
> 
> I just relized that I actually want to understand everything from POST
> on (actually from power on but I know that is very mobo dependant) so
> I guess the question is where do I find the first executed statement
> for BTX (I know how to disamble the MBR so that part is not an issue)
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As Attilio said:


for the kernel, execution starts (for the x86) in /usr/src/sys/i386/i386/locore.s
at around line 205.  

look for:

/**********************************************************************
 *
 * This is where the bootblocks start us, set the ball rolling...
 *
 */
NON_GPROF_ENTRY(btext)


it then skips to sys/kern/init_main.c   (mi_startup) (from memory)
and that jumps back to machdep.c (cpu_startup())


I suggest of course that you also read the bootblocks.