Re: [q] how is ELF binfmt registered?

Tigran Aivazian (tigran@sco.COM)
Tue, 14 Sep 1999 07:47:41 +0100 (BST)


Hello brethren,

Thank you for all the replies I received. However, since all of them were
incorrect, I feel it is my duty to clarify the situation and answer my own
question as I have figured it out at home where I examined the source more
closely.

The trick here is done via module_init()/module_exit() macros which for a
module (if MODULE defined) evaluates to the
init_module()/cleanup_module(), i.e. init_elf_binfmt()/exit_elf_binfmt()
become init_module()/cleanup_module().

If the module (i.e. compilation unit) is compiled into the kernel
statically, then module_init() generates some static variable which is
initialized with the return value of the function. And module_exit(), of
course, generates /* Nothing */ :)

Very impressive but not immediately obvious.

Regards,
------
Tigran A. Aivazian | http://www.sco.com
Escalations Research Group | tel: +44-(0)1923-813796
Santa Cruz Operation Ltd | http://www.ocston.org/~tigran

On Mon, 13 Sep 1999, Tigran Aivazian wrote:

> Hi,
>
> If binfmt_elf is a module then register_binfmt() called from
> init_elf_binfmt does the job. But if it is not a module how is elf_format
> linked to formats?
>
> I grepped for it and couldn't find it. The formats is initialized to NULL
> so it can't be done the way it is done for default_exec_domain (i.e.
> initializaing a variable instead of calling register_exec_domain()). And
> elf_formats is static to binfmt_elf.c so I am a bit lost...
>
> Regards,
> Tigran.
>
>
>

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