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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Linux kernel module - memory allocation
Date: Mon, 18 May 2015 19:02:44 +0300
Organization: Tidorum Ltd
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Date: 2015-05-18T19:02:44+03:00
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On 15-05-18 12:19 , q.kontinuum wrote:
> Hi, thanks a lot for the fast reply.
>
> In comp.lang.ada, you wrote:
>> On 15-05-18 11:27 , q.kontinuum wrote:
>> Do you mean a real "driver", either kernel-linked or a loadable module?
>
> Yes, I'm aiming for a loadable kernel module.

Ok. I don't think many people have tried this with GNAT or Ada -- I 
don't know of any others. Do you know anyone who has done it?

I you haven't already done so, you should find out what "elaboration" 
means in Ada (= initializations before the main subprogram starts), and 
either ensure that your driver somehow does it, although it has no main 
subprogram -- perhaps some part of the driver should call "adainit" 
explicitly -- or perhaps by ensuring that your Ada code needs no 
elaboration. Look into the pragmas Preelaborate and No_Elaboration_Code 
(the latter is GNAT-specific).

The Gnat User Guide section 
http://docs.adacore.com/gnat_ugn-docs/html/gnat_ugn/gnat_ugn/building_executable_programs_with_gnat.html#binding-with-non-ada-main-programs 
may be useful.

>> Which Ada compiler are you using? Do you use some specific compiler
>> switches to adapt it to the driver environment?
>
> I'm using gnat. Command line to compile a
> gnatmake -a -s -mcmodel=kernel ...

I couldn't find any AdaCore documentation about -mcmodel=kernel with 
GNAT. Hmm...

>> You could try with a constrained string subtype, say String(1 .. 10),
>
> I assume if I use that within a function, I'd run into the same problem
> because the function might be called more often, thus still requiring
> dynamic allocation.

I don't follow. if you say

    subtype String10 is String(1 .. 10);

then every object of type String10 has a static size. Local variables of 
that type will be allocated on the (primary, standard) stack, but that 
does not count as dynamic allocation.

Perhaps you are thinking of some part of your real application, not 
strings at all?

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
       .      @       .