Extra:Page Access Codes: Difference between revisions
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Revision as of 13:26, 17 July 2019
| Depends on | Memory Protection |
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This won’t make much sense until you’re read the memory protection article. (Hopefully it will, afterwards!)
These are the 32-bit ARM MMU Access Permission codes. Each page table entry has a 2-bit ‘AP’ code: the interpretation of one code can be varied globally by two other bits {S, R}.
| AP | S R | Supervisor | User |
|---|---|---|---|
| 00 | 0 0 | No access | No access |
| 00 | 1 0 | Read only | No access |
| 00 | 0 1 | Read only | Read only |
| 00 | 1 1 | <unused> | <unused> |
| 01 | - - | Read/write | No access |
| 10 | - - | Read/write | Read only |
| 11 | - - | Read/write | Read/write |
Note that this is just one way to code one chosen set of access permissions – but it serves to show the sort of settings which might be useful.
