Mmu Features; Inviolable Memory Protection; Os Is Inviolable And Protected; The Os Ensures The Inter-Violability Of Software Application - Ingenico IWL220 Technical Manual

2.3.5.2.

MMU features

Hardware protection
Total inter-software protection (read/write)
Code protection
2.3.5.3.

Inviolable memory protection

The controller checks each access to the memory.
2.3.5.4.

OS is inviolable and protected

The processor distinguishes two execution environments:
USER environment: software domain
SUPERVISOR environment: OS domain
No software running in the USER environment can access the SUPERVISOR environment.
This exclusion mechanism is ensured by the processor itself. Therefore the operating
system (OS) is tamper-proof, even in the case of an application software bug. This system
tamper protection ensures that the isolation mechanism monitoring by the OS
remains.
2.3.5.5.

The OS ensures the inter-violability of software application

The OS can decide the access rights of the USER environment at any time.
The MMU used by the processor enables the software application's addressable space to
be defined. A software application can only write to the memory space corresponding to
the extent of its data field. Any attempt to write or read in another space is immediately
"trapped" by the controller, generating an exception. Thus the operating system keeps a
track of this incident for future use with remote diagnostics. The other software application
remain tamper-proofed and operational. Furthermore, the software in question cannot
even self destruct, because its write access to code is denied.
2.3.6.

Card readers

2.3.6.1.

Main smart card reader

The smart card reader is located at the front of the
terminal.
It allows easy introduction and removal of the card,
and leaving the card visible to the user.
Technical manual _iWL220/250
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