QNX RTOS v4 Knowledge Base
QNX RTOS v4 Knowledge Base
| Title |
Description of privity levels |
| Ref. No. |
QNX.000009784 |
| Category(ies) |
Kernel |
| Issue |
We are wondering what exactly "privity level" is. We have only seen the term in a QNX context but have a feeling it has something to do with the Intel processor and protected mode
What exectly is "privity level 1"?
|
| Solution |
It is related to Intel "ring" levels.
Intel defines three access levels:
ring 3 -- no hardware access (user level processes)
ring 1 -- hardware access -- I/O port, dual-ported memory, etc (+ring3)
ring 0 -- CPU+bus configuration, cache configuration, NMI handling (+ring1)
QNX4 defines 3 privity levels:
privity 3 -- only ring 3 access (normal programs)
privity 1 -- ring1 access (must be run by root)
privity 0 -- privity 1 if run by root, privity 3 otherwise
Only the kernel, and anything called by the kernel (for example IRQ handlers) have ring 0 access. |
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