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 Post subject: Re: When your OS goes crazy - Screenshots
PostPosted: Mon Nov 28, 2011 10:58 am 
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Finally, I also have something to show.
In the last 2 days, I finished paging in my kernel and tried to 1:1 map the first GB of RAM.
And this is how it looks like if your PMM gives away the video-memory:
Image
It was a FreeBASIC-specific rounding issue in my mark_used function, which lead to a wrong array index to my bitmap. Without that happening, finding that bug would have been really nasty ;)


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 Post subject: Re: When your OS goes crazy - Screenshots
PostPosted: Mon Nov 28, 2011 12:21 pm 
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That looks very simular to jrepan's visual bug on page 5.

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 Post subject: Re: When your OS goes crazy - Screenshots
PostPosted: Tue Nov 29, 2011 2:06 pm 
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Yeah, it does. Maybe his paging code also had overwritten the video memory ;)
However, my problem was that I used "/" for a division. In FreeBASIC, this gives me a float, and when I put a float into an integer, FreeBASIC rounds the value. So I got 5.75 rounded up to 6, which resulted in wrong array access. Using "\" performs an integer division and the output is 5. I was very confused when I compared the behavior of FreeBASIC and C when using "/" at first ;)

death2all's screenshot also looks very similar, his code also put page tables in the video RAM ^^


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 Post subject: Re: When your OS goes crazy - Screenshots
PostPosted: Tue Nov 29, 2011 3:40 pm 
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haha common error on here, as it seems ;) perhaps a mention in the wiki:
Quote:
DON'T PUT PAGE TABLES IN GMEM!!!!

One time, I even managed it in 1024*768*32 mode, back when I was in my old (borked up) kernel, but I lost the screeny :'( not to worry. I might break my kernel when i go to GMode just to see what happens :) (on a backup copy, ofc)


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 Post subject: Re: When your OS goes crazy - Screenshots
PostPosted: Wed Dec 21, 2011 12:22 pm 
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Attachment:
crash.GIF
crash.GIF [ 5.74 KiB | Viewed 4008 times ]

Also works as an error handler!

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 Post subject: Re: When your OS goes crazy - Screenshots
PostPosted: Mon Jan 02, 2012 12:18 pm 
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don't know why... I was just reminded of the thread by this c error!
i must need to switch modes somehow,but forgot to because i wrote text-bode bits instead!

:D :D

(i haven't been working on it for a while,actually. got back a day or 2 and now i'm doing relativly good.except this!)
Attachment:
File comment: lol,c-based kernel is feelin' happy about my code!
lol.png
lol.png [ 124.65 KiB | Viewed 3825 times ]


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 Post subject: Re: When your OS goes crazy - Screenshots
PostPosted: Fri Jan 13, 2012 12:47 pm 
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darkinsanity wrote:
However, my problem was that I used "/" for a division. In FreeBASIC, this gives me a float, and when I put a float into an integer, FreeBASIC rounds the value. So I got 5.75 rounded up to 6, which resulted in wrong array access. Using "\" performs an integer division and the output is 5. I was very confused when I compared the behavior of FreeBASIC and C when using "/" at first ;)

This reminded me of a European Space Agency rocket called the Ariane 5, which had some code to correct the rocket's angle of trajectory. 40 seconds into the flight that code decides to convert a 64-bit float into a 16-bit signed integer, which, as integers are wont to do when you try to put too much data in them, overflowed. The rocket decided it was facing the wrong direction, so it aimed itself at the ground. Thankfully it was unmanned, and they had had the forethought to put a self-destruct system onboard, so they just blew it up. But if that had actually reached the ground it could have been catastrophic -- I read somewhere that if a fully-fuelled Saturn V rocket had exploded it would have been like a small nuclear bomb. Obviously the Ariane 5 is not the same size as a Saturn V but it's still basically a big tube filled with explosive chemicals.


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 Post subject: Re: When your OS goes crazy - Screenshots
PostPosted: Fri Jan 13, 2012 2:59 pm 
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Synon wrote:
This reminded me of a European Space Agency rocket called the Ariane 5, which had some code to correct the rocket's angle of trajectory. 40 seconds into the flight that code decides to convert a 64-bit float into a 16-bit signed integer, which, as integers are wont to do when you try to put too much data in them, overflowed. The rocket decided it was facing the wrong direction, so it aimed itself at the ground. Thankfully it was unmanned, and they had had the forethought to put a self-destruct system onboard, so they just blew it up. But if that had actually reached the ground it could have been catastrophic -- I read somewhere that if a fully-fuelled Saturn V rocket had exploded it would have been like a small nuclear bomb. Obviously the Ariane 5 is not the same size as a Saturn V but it's still basically a big tube filled with explosive chemicals.

Not exactly, nobody wanted to blew the rocket up. What truly happened is this: after the overflow, on board system core dumped the memory and sent it back to the main control centre on the ground. The computer there examined the input and said, hey what's that? the confirmation code for self-destruct? fine...


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 Post subject: Re: When your OS goes crazy - Screenshots
PostPosted: Sun Jan 15, 2012 1:15 am 
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My OS has had "support" for swapping back to B8000 text mode when it kernel panics for a while... but I never really debugged it (no real need), so it causes some interesting effects when the OS crashes. However, this one really took the cake :)

It's from it crashing while running the GUI, blowing the GUI pixels up and treating them as characters it seems.


Attachments:
20120115-AcessCrash-GUIv2.png
20120115-AcessCrash-GUIv2.png [ 14.18 KiB | Viewed 3611 times ]

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 Post subject: Re: When your OS goes crazy - Screenshots
PostPosted: Fri Jan 20, 2012 6:40 am 
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turdus wrote:
What truly happened is this


Not sure if you're trying to be funny. Read the full account here (pdf).


JAL


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 Post subject: Re: When your OS goes crazy - Screenshots
PostPosted: Fri Jan 20, 2012 8:40 am 
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jal wrote:
Read the full account here (pdf).


Really recommended reading. No-one really royally screwed up. In the end and at the core of it, the fault was re-using Ariane 4 parts without re-testing them to Ariane 5 specs. Plus a couple of bogus decisions on error handling.

Teaches you to think further than just fulfilling the contract. Oh, and document, document, document your assumptions.

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 Post subject: Re: When your OS goes crazy - Screenshots
PostPosted: Tue Feb 07, 2012 10:02 pm 
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Error occurred in GUI:
Attachment:
windErr.GIF
windErr.GIF [ 10.29 KiB | Viewed 3218 times ]

Shouldn't of swapped display pages...

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 Post subject: Re: When your OS goes crazy - Screenshots
PostPosted: Tue Feb 14, 2012 7:51 am 
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GAT wrote:
Error occurred in GUI:


Looks neat, do you have screenshots of the GUI in normal operation?


JAL


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 Post subject: Re: When your OS goes crazy - Screenshots
PostPosted: Thu Feb 16, 2012 6:42 pm 
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Yeah!
Here is what is should look like:
Attachment:
wind2.GIF
wind2.GIF [ 10.77 KiB | Viewed 3840 times ]

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 Post subject: Re: When your OS goes crazy - Screenshots
PostPosted: Fri Feb 17, 2012 3:55 am 
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GAT wrote:
Here is what is should look like


Deliciously old-skool!


JAL


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