WWW.ML.ORG is history!

I don't how many of you this effect, but www.ml.org just announced it's history! They provide URL redirection for a lot of small web servers such as my own, so I was pretty upset personally.


Read all about it at:

http://www.ml.org


This means that all the freakin' links to my page will be dead shortly. :(


Anyway, if you're interested, my server happens to be going down at the same time, so my page is temporarily at:


http://members.tripod.com/~acheronx/


As of January 20th, My server will be back at:

http://acheronx.resnet.tamu.edu


This sucks... :(


Matthew Gross


Comments

  • : I don't how many of you this effect, but www.ml.org just announced it's history! They provide URL redirection for a lot of small web servers such as my own, so I was pretty upset personally.


    : Read all about it at:

    : http://www.ml.org


    : This means that all the freakin' links to my page will be dead shortly. :(


    : Anyway, if you're interested, my server happens to be going down at the same time, so my page is temporarily at:


    : http://members.tripod.com/~acheronx/


    : As of January 20th, My server will be back at:

    : http://acheronx.resnet.tamu.edu


    : This sucks... :(


    : Matthew Gross


    I've read your Comp Sci project.

    The reason why Windows does this is IOPL (input/output privilege level, bits 12-13 of flags) and the bit map of I/O devices in current TSS (task state segment) - all this stuff is just a way to protect I/O devices in protected mode.

    In protected mode instructions in, insb, insw, insd, out, outsb, outsw, outsd, cli and sti are privileged. If your task's RPL (requestor's privilege level) is lower than IOPL (in Win, your program has privilege level 3, i.e. the lowest), then CPU looks at the bit map of I/O devices in TSS. If the bit corresponding to that port is zero, the I/O operation is allowed (even though IOPL doesn't allow it). If neither IOPL nor I/O bit map allows the operation, you simply can't read/write to those ports.

    Windows masks a lot of ports in this way. What is funny, Windows doesn't protect DMA 0 port (it takes care of memory refresh). I've made a program that changes DMA 0 frequency and the memory just fades out after a while. In Windows it causes a lot of exception interrupts and blue screens.

    This is the code to change DMA 0 frequency (I'm not sure if it works on new computers with DIMMs, but you can try it):


    mov al,74h

    out 43h,al

    mov al,0c3h

    out 41h,al

    mov al,50h

    out 41h,al


    Have fun!


  • I had to write that project with the assumption that the reader knew nothing about Protected Mode (My teacher didn't), so that's the reason for the whole deductive approach instead of just stating the facts.

    How odd that DMA 0 isn't protected... of all the things to lock, you'd think something that disrupts system operation would be fairly important...


    URL:http://members.tripod.com/~acheronx/

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