Re: [rtl] runtime image of module

["Calin A. Culianu" <calin@ajvar.org>]

On Sun, 4 Nov 2001, A V wrote:
>
> Hi all,
>
>   I want to know how the runtime image of a will
> be.i.e where the stack will be and bss . Can somebody
> help me.

All modules run in kernel space. This means that the address space of a
running module is the same logical address space that the kernel itself
uses -- this is because a module IS the kernel.  Memory for modules is
cleanly allocated during the module's creation and cleanly free'd during
the module's destruction. (with the exception for memory the module itself
explicitly allocates using kmalloc).

As far as stacks go: Well, that depends... you may have several stacks if
you go and create yourself several threads inside your module.  The other
data and code segments and such all get allocated by the kernel in kernel
space via kmalloc probably during the create_module() system call. For
more info, module.c in the kernel/ subtree of the linux source tree can
answer many of your questions... :)

As for where exactly stacks come from in the linux kernel when tasks run
on behalf of users or during bottom-halves of drivers: that's a good
question. I would imagine that actually there are fewer kernel stacks than
there are kernel tasks.  Most of the time tasks spend their time running
in user mode, where they get their own user stacks.. as for when they run
in kernel mode during system calls, they probably get these temporary
stacks that go away completely as soon as the system call returns to user
mode.

I kind of wish I knew more about the kernel and the relationship between
different threads of execution and dedicated kernel tasks.... Oh well..
maybe someone else can shed more light on this matter...

-Calin




>
> Regards
> Venkat
>
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