segmentation question

segmentation question

[Sri Ram Vemulpali]

Hi All,

      I am developing segmentation for my kernel. In that process I
choose to divide whole memory in to fixed size segments. So a 4GB
memory can be divided in to 8192 segments. So I initialize segment
descriptors in to the GTD withs segments base address and limit. Here
base address are 0,0x10000,0x20000,..... and limit is 64kb always for
every segment. For a task if I choose a segment to assign, I will
place the index of that segment descriptor in to CS, DS. Now when
process generates address to put on address bus, then it will do
computation from logical address to linear address.
After processor picks logical address, it chooses segment descriptor
and adds this 32-bit logical address to segment base address to
generate linear address. Now my question is, if my segment size is
64kb, how is that 32-bit offset is added to segment base address,
which is not right. It should only consider 16-bit offset to add to
base to generate linear address. How can I tell to my processor to
choose only 16-bit offset. Does processor drives offset bit width
automatically based on limit defined in segment descriptor.

Any insight in to this will help me. please clarify my doubt. Waiting
for you reply.

Regards,
Sri.

-- 
Regards,
Sri.

Re: segmentation question

[Bond]

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Sorry for interrupting in between.

On Sat, Oct 2, 2010 at 3:08 AM, Sri Ram Vemulpali
<sri.ram.gmu06@gmail.com>wrote:

> Hi All,
>
>      I am developing segmentation for my kernel. In that process I
> choose to divide whole memory in to fixed size segments. So a 4GB
> memory can be divided in to 8192 segments. So I initialize segment
> descriptors in to the GTD

What is GTD
Where are you reading all this can you give some link I also want to try.

>
>

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Re: segmentation question

[Daniel Baluta]

Hi,

On Sat, Oct 2, 2010 at 12:38 AM, Sri Ram Vemulpali
<sri.ram.gmu06@gmail.com> wrote:
> Hi All,
>
>      I am developing segmentation for my kernel. In that process I
> choose to divide whole memory in to fixed size segments. So a 4GB
> memory can be divided in to 8192 segments. So I initialize segment
> descriptors in to the GTD withs segments base address and limit. Here
> base address are 0,0x10000,0x20000,..... and limit is 64kb always for
> every segment. For a task if I choose a segment to assign, I will
> place the index of that segment descriptor in to CS, DS. Now when
> process generates address to put on address bus, then it will do
> computation from logical address to linear address.
> After processor picks logical address, it chooses segment descriptor
> and adds this 32-bit logical address to segment base address to
> generate linear address. Now my question is, if my segment size is
> 64kb, how is that 32-bit offset is added to segment base address,
> which is not right. It should only consider 16-bit offset to add to
> base to generate linear address. How can I tell to my processor to
> choose only 16-bit offset. Does processor drives offset bit width
> automatically based on limit defined in segment descriptor.

You don't have to "tell" your processor to choose only 16-bit offset.
If the offset is greater than segment limit an exception will occur.


>
> Any insight in to this will help me. please clarify my doubt. Waiting
> for you reply.

> To unsubscribe from this list: send an email with
> "unsubscribe kernelnewbies" to ecartis@nl.linux.org
> Please read the FAQ at http://kernelnewbies.org/FAQ
>
>
@Bond: GTD should be GDT.Also please have a look inside x86 reference manual.

thanks,
Daniel.
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Re: segmentation question

[Raz]

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Can you share the code?

On 02/10/2010 12:10, "Daniel Baluta" <daniel.baluta@gmail.com> wrote:

Hi,

On Sat, Oct 2, 2010 at 12:38 AM, Sri Ram Vemulpali

<sri.ram.gmu06@gmail.com> wrote:

> Hi All,
>
>      I am developing segmentation for my kernel. In that process I
> choose to divide ...
You don't have to "tell" your processor to choose only 16-bit offset.
If the offset is greater than segment limit an exception will occur.



>
> Any insight in to this will help me. please clarify my doubt. Waiting
> for you reply.

> To unsubscribe from this list: send an email with
> "unsubscribe kernelnewbies" to ecartis@nl.linu...
@Bond: GTD should be GDT.Also please have a look inside x86 reference
manual.

thanks,
Daniel.


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To unsubscribe from this list: send an email with
"unsubscribe kernelnewbies" to ecartis@nl.linu...

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Re: segmentation question

[Sri Ram Vemulpali]

Also, can I modify GDT when I am managing memory allocation to tasks.
I mean a task need 120kb, but my segments are divided in to 64kb each.
So, I have to merge two segments to allocate requested memory for
task. In that case I think I need to modify GDT for a descriptor
setting limit.
Usually GDT's are initialized at boot time. But how about at the time
of memory allocation.

NOTE: I am not using any paging at all.

Here GDT means global descriptor table.

Please let me know. Thanks.
Sri.


Here are the links to how to develop kernel.
Also, read intel system programming guide, which gives very good
guidance to architecture
and OS development.

http://www.osdever.net/tutorials/view/brans-kernel-development-tutorial






On Sat, Oct 2, 2010 at 6:15 AM, Raz <raziebe@gmail.com> wrote:
> Can you share the code?
>
> On 02/10/2010 12:10, "Daniel Baluta" <daniel.baluta@gmail.com> wrote:
>
> Hi,
>
> On Sat, Oct 2, 2010 at 12:38 AM, Sri Ram Vemulpali
>
> <sri.ram.gmu06@gmail.com> wrote:
>
>> Hi All,
>>
>>      I am developing segmentation for my kernel. In that process I
>> choose to divide ...
>
> You don't have to "tell" your processor to choose only 16-bit offset.
> If the offset is greater than segment limit an exception will occur.
>
>
>>
>> Any insight in to this will help me. please clarify my doubt. Waiting
>> for you reply.
>
>> To unsubscribe from this list: send an email with
>> "unsubscribe kernelnewbies" to ecartis@nl.linu...
>
> @Bond: GTD should be GDT.Also please have a look inside x86 reference
> manual.
>
> thanks,
> Daniel.
>
> --
>
> To unsubscribe from this list: send an email with
> "unsubscribe kernelnewbies" to ecartis@nl.linu...



-- 
Regards,
Sri.
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