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[mprotect][kconfig] Add safe defaults for MPU region count options #11766

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[mprotect][kconfig] Add safe defaults for MPU region count options #11766

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8 changes: 8 additions & 0 deletions components/mprotect/Kconfig
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Expand Up @@ -17,12 +17,20 @@ if RT_USING_MEM_PROTECTION

config NUM_MEM_REGIONS
int "Total number of memory protection regions supported by hardware"
default 8
help
The number of MPU regions supported by the target MCU. The common value
for Cortex-M4/M7/M33 is 8, but some MCUs expose 4, 12, or 16 regions.
Set this to the actual value reported by the hardware, otherwise the MPU
initialization will reject the configuration at runtime.

config NUM_EXCLUSIVE_REGIONS
int "Total number of exclusive memory regions added using rt_mprotect_add_exclusive_region API"
default 0

config NUM_CONFIGURABLE_REGIONS
int "Maximum number of configurable memory regions for each thread, excluding stack guard and exclusive regions added using rt_mprotect_add_exclusive_region API"
default 0
endif

endmenu
12 changes: 12 additions & 0 deletions components/mprotect/README.md
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Expand Up @@ -83,6 +83,18 @@ rt_mem_region_t static_regions[NUM_STATIC_REGIONS] = {
- 如果开启了`RT_USING_HW_STACK_GUARD`：`NUM_STATIC_REGIONS` + `NUM_CONFIGURABLE_REGIONS` + `NUM_EXCLUSIVE_REGIONS` + 2 <= `NUM_MEM_REGIONS`
- 如果没有开启`RT_USING_HW_STACK_GUARD`：`NUM_STATIC_REGIONS` + `NUM_CONFIGURABLE_REGIONS` + `NUM_EXCLUSIVE_REGIONS` <= `NUM_MEM_REGIONS`

`NUM_MEM_REGIONS` / `NUM_CONFIGURABLE_REGIONS` / `NUM_EXCLUSIVE_REGIONS` 在 Kconfig 中均已提供默认值（分别为 `8` / `0` / `0`），即使不显式配置也不会生成空宏导致编译失败。其中 `NUM_MEM_REGIONS` 取决于具体 MCU，请务必按目标芯片实际的 MPU region 数量修改，否则 MPU 初始化时会因配置值与硬件不符而报错。

## STM32 CubeMX 集成注意事项
如果从 STM32 CubeMX 生成的工程集成，需要注意 `stm32f4xx_it.c`（或对应型号的 `stm32xxx_it.c`）中由 CubeMX 默认生成的 `MemManage_Handler` 会与本组件冲突：

- `libcpu/arm/cortex-m4/mpu.c`（以及 `cortex-m7`、`cortex-m33` 的 `mpu.c`）已经提供了 `MemManage_Handler`，用于读取 `CFSR`/`MMFAR`、定位 MPU region 并调用异常钩子；
- CubeMX 生成的 `stm32f4xx_it.c` 同样包含一个强符号的 `MemManage_Handler`（默认为 `while(1)` 死循环），两者同时参与链接会报 `multiple definition of 'MemManage_Handler'`。

解决方法（任选其一）：
1. 确保 `stm32f4xx_it.c` 不参与编译（RT-Thread 官方 STM32 BSP 默认如此）；
2. 若确需编译 `stm32f4xx_it.c`，删除其中 CubeMX 生成的 `MemManage_Handler` 函数定义。

## 异常检测
程序可以注册钩子函数，用来检测内存异常：
```
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