Re: FYSOS: The Graphical User Interface

From	James Harris <james.harris.1@gmail.com>
Newsgroups	alt.os.development
Subject	Re: FYSOS: The Graphical User Interface
Date	2016-08-27 13:56 +0100
Organization	A noiseless patient Spider
Message-ID	<nps2lp$pf2$1@dont-email.me> (permalink)
References	(15 earlier) <npjtl5$v8l$2@gioia.aioe.org> <npmeqp$lfe$1@dont-email.me> <npmi0l$12mr$1@gioia.aioe.org> <npmjmm$58b$1@dont-email.me> <npmp7f$1f9n$1@gioia.aioe.org>

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On 25/08/2016 13:43, wolfgang kern wrote:
>
> James Harris wrote:
> ....
>>> What could have hooked INT10 before your OS boot ?
>
>> If booted just by the BIOS and my own boot sector, only the graphics
>> card ROMs may have hooked the vector.
>
> It's supposed to do so, otherwise we see only dark screens :)
>
>> But it is hard to verify that that's how the OS was booted.
>
> just check on the vector, if the seg-part is in the range of 0xc000..
> then you can be sure that this mean the video ROM.

IIRC some machines allow RAM to be in that space. Others allow ROM to be 
shadowed by RAM. In either case, there could be malicious code there.

>> Think about your own OS. Couldn't someone who understood its boot
>> process provide the initial boot conditions the OS needs or expects?
>
> NO, such attempt would need a very strange modified BIOS.

I cannot say what checks your OS carries out but here is a typical 
example of a boot process:

1. The boot loader places the kernel at the 1Mbyte mark.

2. The boot loader jumps to the kernel.

3. As long as the kernel has been started at the expected address it runs.

In that example, there is nothing to stop a malicious program fiddling 
with the machine, inserting a step 1a, before starting the kernel.

One thing such a malicious program could do is hook BIOS INTs. If it 
did, then a kernel breaking out to RM to issue BIOS calls would be 
compromised.

All that a hacker would need to know is the OS's boot process.

>> If so, then that person could also hook INT 0x10 and others before
>> starting your code.
>
> I cannot think how this could be done, there is nothing between my OS
> and the BIOS.

Please see above.

...

>> In your case the BIOS code was not malicious, just stupid. But still
>> the cause of a problem to our OSes. All the more reason to emulate our
>> way through BIOS calls, if possible. ;-)
>
> emulation with hw-function analysis ?  good luck on that one.

Where would analysis be needed?

>> QED?
>
> I found it on several cards, old S3 and newer ATI too. can you check if
> your INT10 fall back to 18.2Hz PIT setting ?

Sorry, no. I've recently moved a lot of possessions from Aberdeen to 
London and my stuff is currently in boxes. I don't have a usable test 
setup available at the moment.

As an aside, there is a great book on video cards: Programmer's Guide to 
the EGA, VGA, and Super VGA Cards by Richard Ferraro. I have a copy. It 
looks impressively detailed, albeit a little out of date in some respects.

-- 
James Harris

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FYSOS: The Graphical User Interface "Benjamin David Lunt" <zfysz@fysnet.net> - 2016-07-08 11:52 -0700
  Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-16 11:00 +0200
    Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-16 11:14 +0100
      Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-16 19:07 +0200
        Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-16 19:42 +0100
          Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-16 21:32 +0200
            Re: FYSOS: The Graphical User Interface Rod Pemberton <NoHaveNotOne@zxdehrnyya.cam> - 2016-08-16 23:22 -0400
              Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-17 13:50 +0200
                Re: FYSOS: The Graphical User Interface Rod Pemberton <NoHaveNotOne@zxdehrnyya.cam> - 2016-08-18 01:41 -0400
                Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-18 10:47 +0200
            Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-17 08:45 +0100
              Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-17 13:57 +0200
                Re: FYSOS: The Graphical User Interface Rod Pemberton <NoHaveNotOne@zxdehrnyya.cam> - 2016-08-18 01:47 -0400
                Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-18 10:59 +0200
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-18 11:37 +0100
                Re: FYSOS: The Graphical User Interface Rod Pemberton <NoHaveNotOne@zxdehrnyya.cam> - 2016-08-18 17:38 -0400
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-19 10:03 +0100
                Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-19 22:34 +0200
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-22 17:43 +0100
                Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-22 19:04 +0200
    Re: FYSOS: The Graphical User Interface "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-16 04:18 -0700
      Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-16 12:25 +0100
        Re: FYSOS: The Graphical User Interface "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-16 04:41 -0700
        Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-16 19:19 +0200
      Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-16 19:14 +0200
    Re: FYSOS: The Graphical User Interface "Benjamin David Lunt" <zfysz@fysnet.net> - 2016-08-16 19:24 -0700
      Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-17 12:26 +0200
        Re: FYSOS: The Graphical User Interface "Mike Gonta" <mikegonta@gmail.com> - 2016-08-17 10:42 -0400
          Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-18 01:16 +0200
            Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-18 12:17 +0100
              Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-18 19:23 +0200
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-19 17:29 +0100
                Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-19 22:55 +0200
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-22 17:18 +0100
                Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-22 19:23 +0200
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-23 11:46 +0100
                Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-23 23:44 +0200
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-24 08:29 +0100
                Re: FYSOS: The Graphical User Interface "Alexei A. Frounze" <alexfrunews@gmail.com> - 2016-08-24 02:39 -0700
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-24 17:43 +0100
                Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-24 11:25 +0200
                Re: FYSOS: The Graphical User Interface Rod Pemberton <NoHaveNotOne@zxdehrnyya.cam> - 2016-08-23 17:50 -0400
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-24 09:14 +0100
                Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-24 12:39 +0200
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-25 10:46 +0100
                Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-25 12:40 +0200
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-25 12:10 +0100
                Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-25 14:43 +0200
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-27 13:56 +0100
                Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-27 15:59 +0200
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-27 17:03 +0100
                Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-27 22:43 +0200
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-28 09:22 +0100
                Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-28 11:51 +0200
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-28 13:08 +0100
                Re: FYSOS: The Graphical User Interface Rod Pemberton <NoHaveNotOne@zxdehrnyya.cam> - 2016-08-27 19:12 -0400
                Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-28 10:41 +0200
                Re: FYSOS: The Graphical User Interface Rod Pemberton <NoHaveNotOne@zxdehrnyya.cam> - 2016-08-28 08:48 -0400
                Re: FYSOS: The Graphical User Interface Rod Pemberton <NoHaveNotOne@zxdehrnyya.cam> - 2016-08-27 19:12 -0400
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-28 10:16 +0100
                Re: FYSOS: The Graphical User Interface Rod Pemberton <NoHaveNotOne@zxdehrnyya.cam> - 2016-08-28 08:46 -0400
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-28 18:45 +0100
                Re: FYSOS: The Graphical User Interface Rod Pemberton <NoHaveNotOne@zxdehrnyya.cam> - 2016-08-28 17:51 -0400
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-29 07:55 +0100
                Re: FYSOS: The Graphical User Interface Rod Pemberton <NoHaveNotOne@zxdehrnyya.cam> - 2016-08-29 06:40 -0400
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-31 06:43 +0100
                Re: FYSOS: The Graphical User Interface Rod Pemberton <NoHaveNotOne@zxdehrnyya.cam> - 2016-08-24 07:00 -0400
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-25 11:37 +0100
                Re: FYSOS: The Graphical User Interface Rod Pemberton <NoHaveNotOne@zxdehrnyya.cam> - 2016-08-25 18:45 -0400
                Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-26 10:00 +0200
                Re: FYSOS: The Graphical User Interface Rod Pemberton <NoHaveNotOne@zxdehrnyya.cam> - 2016-08-26 16:16 -0400
                Re: FYSOS: The Graphical User Interface "wolfgang kern" <nowhere@never.at> - 2016-08-27 15:10 +0200
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-27 17:59 +0100
                Re: FYSOS: The Graphical User Interface Rod Pemberton <NoHaveNotOne@zxdehrnyya.cam> - 2016-08-27 19:11 -0400
                Re: FYSOS: The Graphical User Interface James Harris <james.harris.1@gmail.com> - 2016-08-28 10:56 +0100
                Re: FYSOS: The Graphical User Interface Rod Pemberton <NoHaveNotOne@zxdehrnyya.cam> - 2016-08-28 08:45 -0400
        Re: FYSOS: The Graphical User Interface "Benjamin David Lunt" <zfysz@fysnet.net> - 2016-08-17 20:12 -0700

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