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From: Konstantin Andreev <andreev@swemel.ru>
To: CRISTIAN ANDRES VARGAS GONZALEZ <vargascristian@americana.edu.co>,
	 kernelnewbies@kernelnewbies.org
Subject: Re: Are there global constructors in the Linux kernel?
Date: Wed, 09 Oct 2019 11:54:26 +0300
Message-ID: <5D9DA042.2090205@swemel.ru> (raw)
In-Reply-To: <CABfRCzhQkSgZaMX8PrZ2a0qSd=ezG3uxv8EC5TO21K0r9gv_jA@mail.gmail.com>

Hi, Cristian. There are, a kinda of ...

kernel/taskstats.c:
| late_initcall(taskstats_init);

kernel/rcu/update.c:
| early_initcall(check_cpu_stall_init);

There is a whole set of macros STAGE_initcall() in include/linux/init.h

Arguments to these macros invokations are accounted and called by kernel initialization code at strictly defined stages of initialization. See https://0xax.gitbooks.io/linux-insides/content/Concepts/linux-cpu-3.html

The only thing that is run before kernel is <a series of> platform-specific boot loaders, maybe under hypervisor control. Compiler has no power to insert something in between.

Regards, Konstantin.

CRISTIAN ANDRES VARGAS GONZALEZ, 09 Oct 2019 06:44 MSK:
>
> Good day
>
>   I have been doing a little kernel following some repositories of GitHub, videos and wikis, and I have found a topic that leaves me with doubts, the theme is the global constructors.
>
> Suppose I write a program in c, for the user space, for my code to run I must have the main function
> int main() { /*Code*/}
>
> The gcc compiler searches for this function to run my program, but before that happens, I can use the global constructors and write a code that runs before the main function, but in the case of writing a kernel, why do I need to run lines of code before the kernel is executed ?, I understand that when writing a kernel there is no main function and that it is disabled to indicate it to the compiler. In the Linux kernel are there global constructors? If so, what things are executed before starting the kernel?
> att: cristian vargas.

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Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-09  3:44 CRISTIAN ANDRES VARGAS GONZALEZ
2019-10-09  6:54 ` Giovanni Mascellani
2019-10-09  8:54 ` Konstantin Andreev [this message]

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