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Most chips have different privilege levels... ARM processors have 'modes' like User, FIQ, IRQ and Supervisor (sort of the equivalent to ring 0). Different modes
by joosters 9y ago
Most chips have different privilege levels... ARM processors have 'modes' like User, FIQ, IRQ and Supervisor (sort of the equivalent to ring 0). Different modes can have different access controls, e.g. varying access to memory.
Edit: See http://www.heyrick.co.uk/armwiki/Processor_modes http://www.heyrick.co.uk/armwiki/Processor_modes
- ramzyo 9y agoRight - out of curiosity do you know if the Linux kernel uses the term "ring", or some other terminology to map to the underlying hardware implementation, be they rings for x86 or modes for ARM? Maybe it's just "privilege level" or something similar?
- JoshTriplett 9y agoThe Linux kernel just talks about "kernel mode" and "user mode" (or "userspace"). Those then map to ring 0 and ring 3 on x86, or other mechanisms on other platforms.
- ramzyo 9y agoCool, thanks!
- carussell 9y agoGustavo Duartes has a really great blog[1] about kernels and low-level development, with Linux on x86/amd64 being the reference. Here[2] is the one where he goes into CPU rings and kernel- versus user-mode. 1. http://duartes.org/gustavo/blog/archives/ http://duartes.org/gustavo/blog/archives/ 2. http://duartes.org/gustavo/blog/post/cpu-rings-privilege-and-protection/ http://duartes.org/gustavo/blog/post/cpu-rings-privilege-and...