自定义CMake构建STM32应用遇Reset_Handler警告，方法是否正确？

问题描述 #

我尝试用自定义CMake文件构建STM32应用，已完成静态库的编译链接并生成可执行文件，但出现如下警告：

warning: cannot find entry symbol Reset_Handler; defaulting to 0000000008000000

以下是我使用的链接脚本、启动汇编文件及CMake配置，请问当前构建方法是否正确？

链接脚本内容 #

/* Entry Point */
ENTRY(Reset_Handler)

/* Highest address of the user mode stack */
_estack = ORIGIN(RAM_D1) + LENGTH(RAM_D1);    /* 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
{
  ITCMRAM (xrw)    : ORIGIN = 0x00000000,   LENGTH = 64K
  DTCMRAM (xrw)    : ORIGIN = 0x20000000,   LENGTH = 128K
  FLASH    (rx)    : ORIGIN = 0x08000000,   LENGTH = 1024K
  RAM_D1  (xrw)    : ORIGIN = 0x24000000,   LENGTH = 320K
  RAM_D2  (xrw)    : ORIGIN = 0x30000000,   LENGTH = 32K
  RAM_D3  (xrw)    : ORIGIN = 0x38000000,   LENGTH = 16K
}

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

  /* 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

  /* 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 */
    *(.RamFunc)        /* .RamFunc sections */
    *(.RamFunc*)       /* .RamFunc* sections */

    . = ALIGN(4);
    _edata = .;        /* define a global symbol at data end */
  } >RAM_D1 AT> FLASH

  /* Uninitialized data section */
  . = ALIGN(4);
  .bss :
  {
    /* This is used by the startup in order to initialize the .bss section */
    _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_D1

  /* 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_D1

 .lwip_sec (NOLOAD) :
  {
    . = ABSOLUTE(0x30000000);
    *(.RxDecripSection) 
    
    . = ABSOLUTE(0x30000060);
    *(.TxDecripSection)
    
    . = ABSOLUTE(0x30000200);
    *(.Rx_PoolSection) 
  } >RAM_D2

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

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

启动汇编文件内容 #

.syntax unified
  .cpu cortex-m7
  .fpu softvfp
  .thumb

.global  g_pfnVectors
.global  Default_Handler

/* start address for the initialization values of the .data section.
defined in linker script */
.word  _sidata
/* start address for the .data section. defined in linker script */
.word  _sdata
/* end address for the .data section. defined in linker script */
.word  _edata
/* start address for the .bss section. defined in linker script */
.word  _sbss
/* end address for the .bss section. defined in linker script */
.word  _ebss
/* stack used for SystemInit_ExtMemCtl; always internal RAM used */

    .section  .text.Reset_Handler
  .weak  Reset_Handler
  .type  Reset_Handler, %function
Reset_Handler:
  ldr   sp, =_estack      /* set stack pointer */

/* Call the clock system initialization function.*/
  bl  SystemInit

/* Copy the data segment initializers from flash to SRAM */
  ldr r0, =_sdata
  ldr r1, =_edata
  ldr r2, =_sidata
  movs r3, #0
  b LoopCopyDataInit

CopyDataInit:
  ldr r4, [r2, r3]
  str r4, [r0, r3]
  adds r3, r3, #4

LoopCopyDataInit:
  adds r4, r0, r3
  cmp r4, r1
  bcc CopyDataInit
/* Zero fill the bss segment. */
  ldr r2, =_sbss
  ldr r4, =_ebss
  movs r3, #0
  b LoopFillZerobss

FillZerobss:
  str  r3, [r2]
  adds r2, r2, #4

LoopFillZerobss:
  cmp r2, r4
  bcc FillZerobss

/* Call static constructors */
    bl __libc_init_array
/* Call the application's entry point.*/
  bl  main
  bx  lr
.size  Reset_Handler, .-Reset_Handler

... some code

CMake配置内容 #

...

add_subdirectory(${STLIB_DIR} ${STLIB_DIR}/build)
add_executable(${EXECUTABLE} 
  ${CMAKE_SOURCE_DIR}/Core/Src/main.cpp 
  ${CMAKE_SOURCE_DIR}/Core/Src/syscalls.c 
  ${CMAKE_SOURCE_DIR}/Core/Src/stm32h7xx_hal_msp.c
  ${CMAKE_SOURCE_DIR}/Core/Src/stm32h7xx_it.c
  ${CMAKE_SOURCE_DIR}/Core/Src/sysmem.c
  ${CMAKE_SOURCE_DIR}/Core/Src/system_stm32h7xx.c
  ${CMAKE_SOURCE_DIR}/Core/Startup/startup_stm32h723zgtx.s
  )
target_link_libraries(${EXECUTABLE} ${STLIB_DIR}/build/libst-lib.a)

...

target_link_options(${EXECUTABLE} PUBLIC 
        -T${CMAKE_SOURCE_DIR}/STM32H723ZGTX_FLASH.ld
        -mcpu=cortex-m7
        -mthumb
        -mfpu=fpv5-d16
        -mfloat-abi=hard
        -specs=nosys.specs
        -lc
        -lm
        -lnosys
        -Wl,-Map=${PROJECT_NAME}.map,--cref
        -Wl,--gc-sections
        )

问题分析与修复方案 #

当前构建思路整体正确，但存在几个细节问题导致链接器无法找到Reset_Handler符号：

1. 启动汇编文件中Reset_Handler的弱符号属性 #

启动汇编里将Reset_Handler标记为.weak，这意味着如果没有其他强符号定义该名称，链接器可能无法将其识别为有效入口。修复方法：将.weak Reset_Handler改为.global Reset_Handler，确保符号为全局强符号：

.section  .text.Reset_Handler
.global  Reset_Handler
.type  Reset_Handler, %function
Reset_Handler:

2. 链接脚本中不必要的库丢弃操作 #

链接脚本的/DISCARD/段丢弃了libgcc.a，但Cortex-M7架构依赖该库提供的底层指令支持（如Thumb/ARM指令切换、浮点运算辅助等），这可能间接导致符号解析异常。修复方法：注释掉对libgcc.a的丢弃：

/DISCARD/ :
{
  libc.a ( * )
  libm.a ( * )
  # libgcc.a ( * )  // 保留libgcc.a以支持底层指令
}

3. 确认启动文件的编译与链接顺序 #

CMake的add_executable已包含启动汇编文件，这是正确的；静态库放在target_link_libraries的末尾也符合链接顺序规则（目标文件在前，依赖库在后）。可通过查看编译日志确认startup_stm32h723zgtx.s是否被正常编译为目标文件并参与链接。

4. 验证链接脚本路径准确性 #

确保-T${CMAKE_SOURCE_DIR}/STM32H723ZGTX_FLASH.ld指向的链接脚本路径正确，避免因文件缺失导致链接器无法读取ENTRY(Reset_Handler)配置。

总结 #

调整上述细节后，链接器应该能正确识别Reset_Handler入口符号，消除警告。整体构建流程的方向是正确的，只需修正符号属性、库依赖等细节问题。

内容的提问来源于stack exchange，提问作者dahko37