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BOTOKILLER

Joined: 07 Jan 2011
Posts: 154
Location: Ukraine

BOTOKILLER 27 Jul 2011, 12:08

Hi everyone!
Yeah, I figured out how paging interacts with segments - LDT Very Happy

Where can I find LDT tutorial???

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NSOS

27 Jul 2011, 12:08

DJ Mauretto

Joined: 14 Mar 2007
Posts: 464
Location: Rome,Italy

DJ Mauretto 27 Jul 2011, 12:17

Always Intel Manuals Wink

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Nil Volentibus Arduum Razz

27 Jul 2011, 12:17

BOTOKILLER

Joined: 07 Jan 2011
Posts: 154
Location: Ukraine

BOTOKILLER 27 Jul 2011, 12:25

Which one???

27 Jul 2011, 12:25

f2

Joined: 30 May 2010
Posts: 13
Location: France

f2 27 Jul 2011, 12:31

BOTOKILLER wrote:

Which one???

Intel Architecture Software Developer’s Manual Volume 3: System Programming Guide

Hope you will search by yourself next time...

27 Jul 2011, 12:31

edfed

Joined: 20 Feb 2006
Posts: 4283
Location: Now

edfed 27 Jul 2011, 13:02

BOTOKILLER wrote:

Which one???

the fact that you ask it means you did not read any.

hurry up! download ALL the manuals, don't forget to rename the pdf files with the true title of the volume, because a number is not very easy to remember.

and read all the manuals. you are not forced to read everything, but at least, try to overview the main topics of the manuals, and you will have a lot less question to ask.

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27 Jul 2011, 13:02

BOTOKILLER

Joined: 07 Jan 2011
Posts: 154
Location: Ukraine

BOTOKILLER 27 Jul 2011, 13:12

edfed wrote:

BOTOKILLER wrote:
Which one???

the fact that you ask it means you did not read any.

hurry up! download ALL the manuals, don't forget to rename the pdf files with the true title of the volume, because a number is not very easy to remember.

and read all the manuals. you are not forced to read everything, but at least, try to overview the main topics of the manuals, and you will have a lot less question to ask.

I read them, In fact they are opened in a few tabs of chrome which I never close...

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27 Jul 2011, 13:12

BOTOKILLER

Joined: 07 Jan 2011
Posts: 154
Location: Ukraine

BOTOKILLER 27 Jul 2011, 16:11

I cant find where LDT entry format is mentioned...

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NSOS

27 Jul 2011, 16:11

f2

Joined: 30 May 2010
Posts: 13
Location: France

f2 27 Jul 2011, 17:02

it's probably wiritten somewhere in Intel manuals (but I don't know where, I'm not interested about implementing such obsolete things like LDTs).

I have searched the Internet and I found an interesting page about segmentation on x86:
http://book.opensourceproject.org.cn/kernel/kernel3rd/opensource/0596005652/understandlk-chp-2-sect-2.html

27 Jul 2011, 17:02

BOTOKILLER

Joined: 07 Jan 2011
Posts: 154
Location: Ukraine

BOTOKILLER 28 Jul 2011, 11:53

f2 wrote:

it's probably wiritten somewhere in Intel manuals (but I don't know where, I'm not interested about implementing such obsolete things like LDTs).

I have searched the Internet and I found an interesting page about segmentation on x86:
http://book.opensourceproject.org.cn/kernel/kernel3rd/opensource/0596005652/understandlk-chp-2-sect-2.html

but LDT must somehow point to Page tables...

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NSOS

28 Jul 2011, 11:53

qandrew

Joined: 21 Jan 2010
Posts: 3

qandrew 28 Jul 2011, 12:23

BOTOKILLER wrote:

but LDT must somehow point to Page tables...

The LDT isn't related to Paging!

Why? It just isn't. As Wikipedia mentions, "On x86 processors not having paging features, like the Intel 80286, the LDT is essential to implementing separate address spaces for multiple processes.".

You should choose what you want to use: it is either Paging or LDT. Not both at the same time.

28 Jul 2011, 12:23

BOTOKILLER

Joined: 07 Jan 2011
Posts: 154
Location: Ukraine

BOTOKILLER 28 Jul 2011, 12:37

Then what do I put into CS, DS, SS, etc when paging enabled???

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NSOS

28 Jul 2011, 12:37

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19076
Location: In your JS exploiting you and your system

revolution 28 Jul 2011, 12:44

LDT/GDT defines segments and thus affects CS, DS, etc.

Paging defines access to memory pages and is independent of segments. Most modern OSes effectively disable segmentation by defining all segments to be 4GB (or run in 64 bit mode where there are no segments of consequence (except that pesky GS thing)).

28 Jul 2011, 12:44

BOTOKILLER

Joined: 07 Jan 2011
Posts: 154
Location: Ukraine

BOTOKILLER 28 Jul 2011, 12:59

So, I just have to put all segments to point to whole address space???
That simple Smile

Thanks guys!!!

Last edited by BOTOKILLER on 28 Jul 2011, 13:01; edited 1 time in total

28 Jul 2011, 12:59

f2

Joined: 30 May 2010
Posts: 13
Location: France

f2 28 Jul 2011, 13:00

Hmm... Well.

I fully agree that you ask lot of questions about something you can't understand. But mostly, you can easily answer these questions:
- by reading carefully the Intel manuals,
- or by following all existing tutorials about OS development.
- and, of course, if you have a question, search on theOSDev Wiki, the FASM board, or on Google. Post here ONLY if you can't find an answer that question.

28 Jul 2011, 13:00

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