Re: [uml-devel] do_uml_initcalls

[Blaisorblade <blaisorblade@yahoo.it>]

On Sunday 07 May 2006 14:54, user-mode-linux-devel-admin@lists.sourceforge.net 
wrote:
> Hi all,
>
> I was looking at the initialization code of UML and I found the function
> do_uml_initcalls :
>
> 1: static __init void do_uml_initcalls(void)
> 2: {
> 3: 	initcall_t *call;
> 4:
> 5: 	call = &__uml_initcall_start;
> 6:	 while (call < &__uml_initcall_end){;
> 7:	(*call)();
> 8:         call++;
> 9:  }
>
> First, there's a ';' at the end of line 6 : typo error I guess.

Apart from this one, everything is like the general Linux kernel. See below.

> But my point is : this function is unreadable !

> It does simply call all the functions in the ".initcall"
> section.

Not exactly, that's .uml.initcall.init; see include/asm-um/common.lds.S:

  __uml_initcall_start = .;
  .uml.initcall.init : { *(.uml.initcall.init) }
  __uml_initcall_end = .;

Also, in the section there is a list of pointers, not the functions 
themselves.

> Wouldn't it be better to call all the functions explicitely ?
>
> Because I was thinking of another problem : the modules. If some modules
> are compiled and that the init_modules functions are put in the initcall
> section, then all the modules will be loaded.

Nothing from modules is linked inside the kernel.
The function set as module_init() function is put into the above section only 
if the code is linked statically, not as module. When it's a module it's put 
somewhere so when the module is loaded that function is called.

> That was just some thoughts :p

This idea is not new for UML - the linux kernel uses the same idea 
for .initcall.init section (we do that separately because some functions must 
be called at different moments). And that works.
-- 
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade

	

	
		
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