在STM32F412上的FreeRTOS-MPU用户模式（非特权）任务中使用“ HAL_UART_Transmit”的问题

Question

我正在将FreeRTOS-MPU端口与STM32F412配合使用以实现内存保护。我已经成功完成了两个任务UserMode（非特权）和PrivilegeMode。但是我无法在UserMode中运行“ HAL_UART_Transmit” API（或类似的HAL API），这会导致内存故障。但是，相同的API在Privilege模式任务中可以正常工作。

有人知道我想念什么吗？

我的项目链接器摘要如下，取自STM32F4 SDK FreeRTOS_MPU项目示例：

/*
******************************************************************************
**
**  File        : LinkerScript.ld
**
**  Author      : Auto-generated by Ac6 System Workbench
**
**  Abstract    : Linker script for STM32F412CGUx series
**                1024Kbytes FLASH and 256Kbytes RAM
**
**                Set heap size, stack size and stack location according
**                to application requirements.
**
**                Set memory bank area and size if external memory is used.
**
**  Target      : STMicroelectronics STM32
**
**  Distribution: The file is distributed “as is,” without any warranty
**                of any kind.
**
*****************************************************************************

/* Entry Point */
ENTRY(Reset_Handler)

/* Highest address of the user mode stack */
_estack = 0x20040000;    /* end of RAM */
/* Generate a link error if heap and stack don't fit into RAM */
_Min_Heap_Size = 0x200;      /* required amount of heap  */
_Min_Stack_Size = 0x400; /* required amount of stack */

/* Specify the memory areas */
MEMORY
{
FLASH_priv (rx)    : ORIGIN = 0x08000000, LENGTH = 16K
FLASH (rx)         : ORIGIN = 0x08004000, LENGTH = 1008K
RAM_priv (xrw)     : ORIGIN = 0x20000000, LENGTH = 2048
RAM (xrw)          : ORIGIN = 0x20000800, LENGTH = 254K
}

/* Variables used by FreeRTOS-MPU. */
_Privileged_Functions_Region_Size = 16K;
_Privileged_Data_Region_Size     = 2048;

__FLASH_segment_start__        = ORIGIN( FLASH_priv );
__FLASH_segment_end__          = __FLASH_segment_start__ + LENGTH( FLASH_priv ) + LENGTH( FLASH );

__privileged_functions_start__ = ORIGIN( FLASH_priv );
__privileged_functions_end__   = __privileged_functions_start__ + _Privileged_Functions_Region_Size;

__SRAM_segment_start__         = ORIGIN( RAM_priv );
__SRAM_segment_end__           = __SRAM_segment_start__ + LENGTH( RAM_priv ) + LENGTH( RAM );

__privileged_data_start__      = ORIGIN( RAM_priv );
__privileged_data_end__        = __privileged_data_start__ + _Privileged_Data_Region_Size;

/* Define output sections */
SECTIONS
{
  /* The startup code goes first into FLASH */
  .isr_vector :
  {
    . = ALIGN(4);
    KEEP(*(.isr_vector)) /* Startup code */
    . = ALIGN(4);
  } >FLASH_priv
  .privileged_functions : 
  {
    . = ALIGN(4);
    *(privileged_functions)
    *(privileged_functions*)
    . = ALIGN(4);
  } >FLASH_priv

  /* The program code and other data goes into FLASH */
  .text :
  {
    . = ALIGN(4);
    *(.text)           /* .text sections (code) */
    *(.text*)          /* .text* sections (code) */
    *(.glue_7)         /* glue arm to thumb code */
    *(.glue_7t)        /* glue thumb to arm code */
    *(.eh_frame)

    KEEP (*(.init))
    KEEP (*(.fini))

    . = ALIGN(4);
    _etext = .;        /* define a global symbols at end of code */
  } >FLASH

  /* Constant data goes into FLASH */
  .rodata :
  {
    . = ALIGN(4);
    *(.rodata)         /* .rodata sections (constants, strings, etc.) */
    *(.rodata*)        /* .rodata* sections (constants, strings, etc.) */
    . = ALIGN(4);
  } >FLASH

  .ARM.extab   : { *(.ARM.extab* .gnu.linkonce.armextab.*) } >FLASH
  .ARM : {
    __exidx_start = .;
    *(.ARM.exidx*)
    __exidx_end = .;
  } >FLASH

  .preinit_array     :
  {
    PROVIDE_HIDDEN (__preinit_array_start = .);
    KEEP (*(.preinit_array*))
    PROVIDE_HIDDEN (__preinit_array_end = .);
  } >FLASH
  .init_array :
  {
    PROVIDE_HIDDEN (__init_array_start = .);
    KEEP (*(SORT(.init_array.*)))
    KEEP (*(.init_array*))
    PROVIDE_HIDDEN (__init_array_end = .);
  } >FLASH
  .fini_array :
  {
    PROVIDE_HIDDEN (__fini_array_start = .);
    KEEP (*(SORT(.fini_array.*)))
    KEEP (*(.fini_array*))
    PROVIDE_HIDDEN (__fini_array_end = .);
  } >FLASH

  .pbss : 
  {
    . = ALIGN(4);
    _spbss = .;
    *(privileged_data)
    *(privileged_data*)
    . = ALIGN(4);
    _epbss = .;
  } >RAM_priv 
  /* used by the startup to initialize data */
  _sipdata = LOADADDR(.pdata);
  .pdata : 
  {
    . = ALIGN(4);
    _spdata = .;
    *(privileged_initialized_data)
    *(privileged_initialized_data*)
    . = ALIGN(4);
    _epdata = .;
  } >RAM_priv AT> FLASH_priv
  /* used by the startup to initialize data */
  _sidata = LOADADDR(.data);

  /* Initialized data sections goes into RAM, load LMA copy after code */
  .data : 
  {
    . = ALIGN(4);
    _sdata = .;        /* create a global symbol at data start */
    *(.data)           /* .data sections */
    *(.data*)          /* .data* sections */

    . = ALIGN(4);
    _edata = .;        /* define a global symbol at data end */
  } >RAM AT> FLASH


  /* Uninitialized data section */
  . = ALIGN(4);
  .bss :
  {
    /* This is used by the startup in order to initialize the .bss secion */
    _sbss = .;         /* define a global symbol at bss start */
    __bss_start__ = _sbss;
    *(.bss)
    *(.bss*)
    *(COMMON)

    . = ALIGN(4);
    _ebss = .;         /* define a global symbol at bss end */
    __bss_end__ = _ebss;
  } >RAM

  /* User_heap_stack section, used to check that there is enough RAM left */
  ._user_heap_stack :
  {
    . = ALIGN(8);
    PROVIDE ( end = . );
    PROVIDE ( _end = . );
    . = . + _Min_Heap_Size;
    . = . + _Min_Stack_Size;
    . = ALIGN(8);
  } >RAM



  /* Remove information from the standard libraries */
  /DISCARD/ :
  {
    libc.a ( * )
    libm.a ( * )
    libgcc.a ( * )
  }

  .ARM.attributes 0 : { *(.ARM.attributes) }
}

Answer 1

您需要设置MPU以允许用户模式访问UART外围设备（以及UART驱动程序库使用的任何其他外围设备。

首先以用户模式读写权限创建从地址0x40000000到0x60000000（大小：0x20000000）的MPU区域。

我建议在向量表中添加MPU故障处理程序，以便在出现错误时知道。