hujun260 opened a new pull request, #18157:
URL: https://github.com/apache/nuttx/pull/18157
## Summary
This pull request series improves the ARM64 Memory Protection Unit (MPU)
implementation across three incremental commits:
1. **Explicit naming**: Rename MPU attribute macros to clearly indicate
access permissions (REGION_RAM_ATTR → REGION_RW_NA_ATTR, etc.)
2. **Unified interface**: Refactor MPU configuration functions to use
consistent parameters across all architectures
3. **Code simplification**: Consolidate macro definitions to eliminate
duplication while preserving functionality
These changes improve code clarity, ensure consistency across ARM64 variants
(including Cortex-R82), and reduce maintenance burden.
## Changes
**Commit 1: Rename MPU attribute macros (61 lines)**
- Rename `REGION_RAM_ATTR` → `REGION_RW_NA_ATTR` (Kernel Read/Write, User No
Access)
- Rename `REGION_URAM_ATTR` → `REGION_RW_RW_ATTR` (Kernel & User Read/Write)
- Rename `REGION_RAM_TEXT_ATTR` → `REGION_KTEXT_ATTR` (Kernel Text)
- Rename `REGION_RAM_UTEXT_ATTR` → `REGION_UTEXT_ATTR` (User Text)
- Add `REGION_RO_RO_ATTR` for read-only regions accessible to all
- Add `REGION_RO_NA_ATTR` for kernel read-only, user no access regions
- Update boot code to use new macro names
**Commit 2: Unify MPU interface (73 lines)**
- Change `mpu_modify_region(region, table)` → `mpu_modify_region(region,
base, size, flags1, flags2)`
- Change `mpu_configure_region(table)` → `mpu_configure_region(base, size,
flags1, flags2)`
- Direct parameter interface eliminates struct dependency
- Ensures consistency across all ARM64 MPU variants
- Update all callers in boot code
**Commit 3: Simplify macro definitions (125 lines)**
- Introduce unified `SHAREABLE_MSK` macro:
- CONFIG_SMP: `SHAREABLE_MSK = INNER_SHAREABLE_MSK`
- CONFIG_UP: `SHAREABLE_MSK = NON_SHAREABLE_MSK`
- Consolidate duplicated CONFIG_SMP/CONFIG_UP macro blocks
- Replace individual REGION_*_ATTR definitions with unified versions
- Result: 83 lines removed, 42 lines added (net -41 lines)
**Total Changes**: ~150 net lines simplified, improved consistency and
clarity
## Impact
- **Clarity**: Explicit permission semantics in macro names (RW_NA, RO_RO,
etc.)
- **Consistency**: Same interface across Cortex-A72, Cortex-R82, and other
ARM64 variants
- **Maintainability**: Reduced macro duplication and configuration complexity
- **Code reduction**: 41 net lines removed through consolidation
- **Extensibility**: Easier to add new attribute combinations
## Technical Details
**Naming convention improvements:**
| Old Name | New Name | Meaning |
|----------|----------|---------|
| REGION_RAM_ATTR | REGION_RW_NA_ATTR | Kernel RW, User NA |
| REGION_URAM_ATTR | REGION_RW_RW_ATTR | Kernel RW, User RW |
| REGION_RAM_TEXT_ATTR | REGION_KTEXT_ATTR | Kernel Text (Read-Only) |
| REGION_RAM_UTEXT_ATTR | REGION_UTEXT_ATTR | User Text (Read-Only) |
| NEW | REGION_RO_RO_ATTR | Kernel RO, User RO |
| NEW | REGION_RO_NA_ATTR | Kernel RO, User NA |
**Interface unification:**
```c
// Before: Struct-based (inconsistent across architectures)
struct arm64_mpu_region table = { ... };
mpu_modify_region(region, &table);
// After: Direct parameters (consistent everywhere)
mpu_modify_region(region, base, size, flags1, flags2);
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