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jojojoris
Joined: 30 Mar 2008
Posts: 261
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 Posted: Thu Apr 22, 2010 6:47 am Post subject: Clean ram and load firmware from ms |
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Hi,
It seems i can't find any clear documentation about this:
Why can't we just run a small ASM application from a exploit which clears all the ram (user and kernel space) and then imitates the behaviour of the IPL and load a firmware from the MS like timemachine?
I tought the psp uses Cooperative multitasking so when it is running a asm application which doesn't call any PSPSDK functions it would just keep running the ASM and the firmware doesn't interfere.
Do i misunderstand some facts because the consept seems so easy but it has not been made yet.
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coyotebean
Joined: 05 Dec 2009
Posts: 26
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| Posted: Thu Apr 22, 2010 2:29 pm Post subject: |
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You cannot do anything with a user mode exploit. You have no access to kernel space, kernel functions and hardware I/O
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jojojoris
Joined: 30 Mar 2008
Posts: 261
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| Posted: Thu Apr 22, 2010 5:58 pm Post subject: |
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Yes i know.
I'm used to be a programmer for psp apps.
But why shoeldn't you have that access? How does that access meganism work? What is the difference between usermode ASM and kernelmode ASM? You are just running plain ASM without the inteference of the firmware. So you should be able to do everything you want.
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| Code: | int main(){
SetupCallbacks();
makeNiceGame();
sceKernelExitGame();
} |
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m0skit0
Joined: 02 Jun 2009
Posts: 226
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| Posted: Thu Apr 22, 2010 7:17 pm Post subject: |
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Did you read a MIPS reference before starting talk? I guess you don't. I strongly suggest you doing so.
The protection is hardware based, there's nothing you can do by software to fool it. The CPU distinguishes between 2 big types of memory: user (low 2 GB) and kernel (high 2 GB). If for example a user mode code tries to load a word from kernel space, the CPU will just raise an exception about invalid address. Also RAM interface in PSP is programmable to allow/deny read/write permissions to RAM by pages.
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jojojoris
Joined: 30 Mar 2008
Posts: 261
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| Posted: Fri Apr 23, 2010 8:03 am Post subject: |
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So if i get it right... this could only be done from kernel space.
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| Code: | int main(){
SetupCallbacks();
makeNiceGame();
sceKernelExitGame();
} |
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arnie
Joined: 11 Apr 2009
Posts: 16
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| Posted: Mon Apr 26, 2010 8:53 am Post subject: |
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Yes. Also, some firmware modules loaded can't be unloaded, and the only firmware you can load it the one you have on flash. If you want to load from ms, that's another story. MS Fat Flash driver. D:
-Arnie |
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Jim
Joined: 02 Jul 2005
Posts: 487
Location: Sydney
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| Posted: Mon Apr 26, 2010 10:47 pm Post subject: |
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You'd have to make sure you'd disabled all hardware interrupts too.
Jim
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