Specifications

Intel
®
Quark SoC X1000 Core
October 2013 Developer’s Manual
Order Number: 329679-001US 81
Protected Mode Architecture—Intel
®
Quark Core
6.3 Protection
6.3.1 Protection Concepts
The Intel
®
Quark SoC X1000 Core has four levels of protection that support multi-
tasking by isolating and protecting user programs from each other and the operating
system. The privilege levels control the use of privileged instructions, I/O instructions,
and access to segments and segment descriptors. Unlike traditional processor-based
systems, in which this protection is achieved only through the use of complex external
hardware and software, the Intel
®
Quark SoC X1000 Core provides the protection as
part of its integrated Memory Management Unit. The Intel
®
Quark SoC X1000 Core
offers an additional type of protection on a page basis, when paging is enabled. See
Section 6.4.6.
The four-level hierarchical privilege system is illustrated in Figure 35. It is an extension
of the user/supervisor privilege mode commonly used by minicomputers. The
user/supervisor mode is fully supported by the Intel
®
Quark SoC X1000 Core paging
mechanism. The privilege levels (PLs) are numbered 0 through 3. Level 0 is the most
privileged or trusted level.
Figure 34. Segment Descriptor Caches for Virtual 8086 Mode within Protected Mode
(Segment Limit and Attributes are Fixed)
Key:
Y = yes D = expand down
N = no B = byte granularity
0 = privilege level 0 P = page granularity
1 = privilege level 1 W = push/pop 16-bit words
2 = privilege level 2 F = push/pop 32-bit dwords
3 = privilege level 3 – = does not apply to that segment cache register
U = expand up