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System Management Mode: Difference between revisions

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System Management Mode (view source)

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VisualWikitext
(SMM area information)
m (Reverted edits by Atie (talk) to last revision by Superleaf1995)
 
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== Transparency ==
TODO - write a bit about how SMM implements its transparent behavior, SMRAM, the lock bits in the MMU, etc.
The System Management Mode handler is usually located at physical address 0xA0000-0xBFFFF. However, it is shadowed and the code is visible only when the CPU entered SMM. To unlock that area, you must use chipset specific methods. For example, in Q35 machines you need to manipulate a register in the DRAM controller, located at PCI bus/slot/function 0/0/0.
 
To avoid the OS from creating a custom SMM handler, the firmware must lock the SMM register in the DRAM controller, so it cannot be modified anymore, unless the computer reboots.
 
== What can I do with system management mode? ==
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