ELF와 MAP 파일 분석 — 베어메탈 메모리 레이아웃 추적

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int counter = 42;     // .data — flash에 42가 굽힘, SRAM에 0x20000000부터 변수 위치
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static int g_buf[256]; // .bss — SRAM에 0 초기화
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const int kMax = 100;  // .rodata — flash만 (수정 안 함)
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void worker() {...}    // .text — flash만

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// startup_stm32f4xx.s (단순화 C 버전)
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extern int __etext;      // .data의 LMA 끝 = flash 안의 .data 값들
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extern int __data_start__, __data_end__;  // .data의 VMA (SRAM)
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extern int __bss_start__, __bss_end__;
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extern int main(void);
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void Reset_Handler(void) {
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    // 1. .data 초기화 (flash → SRAM 복사)
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    int *src = &__etext;
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    int *dst = &__data_start__;
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    while (dst < &__data_end__) *dst++ = *src++;
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    // 2. .bss 영초기화
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    dst = &__bss_start__;
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    while (dst < &__bss_end__) *dst++ = 0;
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    // 3. 클럭 설정 (옵션)
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    SystemInit();
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    // 4. C++ static initializer (있다면)
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    __libc_init_array();
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    // 5. main 진입
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    main();
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    // 6. main이 return하면 무한 루프
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    while (1) {}
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}

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/* memory map */
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MEMORY {
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    FLASH (rx)  : ORIGIN = 0x08000000, LENGTH = 1024K
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    RAM   (rwx) : ORIGIN = 0x20000000, LENGTH = 128K
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}
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ENTRY(Reset_Handler)
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SECTIONS {
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    .isr_vector : {
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        KEEP(*(.isr_vector))     /* GC가 못 지우게 */
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    } > FLASH
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    .text : {
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        *(.text*)
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        *(.rodata*)
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        *(.glue_7*)              /* ARM/Thumb interworking */
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        *(.eh_frame)             /* C++ exception unwind */
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        KEEP(*(.init))
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        KEEP(*(.fini))
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    } > FLASH
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    /* C++ ctor/dtor 배열 */
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    .init_array : {
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        PROVIDE_HIDDEN (__init_array_start = .);
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        KEEP(*(SORT(.init_array.*)))
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        KEEP(*(.init_array))
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        PROVIDE_HIDDEN (__init_array_end = .);
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    } > FLASH
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    /* .data: LMA=flash, VMA=RAM */
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    _sidata = LOADADDR(.data);    /* flash 안의 시작 */
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    .data : {
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        _sdata = .;
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        *(.data*)
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        _edata = .;
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    } > RAM AT > FLASH
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    .bss : {
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        _sbss = .;
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        *(.bss*)
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        *(COMMON)
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        _ebss = .;
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    } > RAM
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    /* 스택 — 보통 .bss 뒤에 */
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    .stack (NOLOAD) : ALIGN(8) {
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        _sstack = .;
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        . = . + 0x1000;            /* 4KB 스택 */
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        _estack = .;
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    } > RAM
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    /DISCARD/ : {
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        *(.comment)
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        *(.note.*)
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    }
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}

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extern int _sdata, _edata, _sidata;
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extern int _sbss, _ebss;
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extern int _estack;

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Linker script and memory map
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Memory Configuration
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Name             Origin             Length             Attributes
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FLASH            0x08000000         0x00100000         xr
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RAM              0x20000000         0x00020000         xrw
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*default*        0x00000000         0xffffffff
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Linker script: stm32f4_flash.ld
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LOAD /opt/cross/arm-none-eabi/lib/thumb/v7e-m+dp/hard/crti.o
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LOAD /opt/cross/arm-none-eabi/lib/gcc/arm-none-eabi/13.2.0/thumb/v7e-m+dp/hard/crtbegin.o
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LOAD ./build/main.o
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LOAD ./build/sensor.o
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...
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                0x0800a3a8                __init_array_start = .
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.init_array     0x0800a3a8        0x4
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 *(SORT_BY_INIT_PRIORITY(.init_array.*) ...)
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 *(.init_array)
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 .init_array    0x0800a3a8        0x4 ./build/main.o
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                0x0800a3ac                __init_array_end = .
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.data           0x20000000      0x140 load address 0x0800a3ac
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                0x20000000                _sdata = .
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 *(.data*)
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 .data          0x20000000       0xe4 ./build/main.o
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                0x20000004                g_config
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                0x20000040                g_state
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                0x200000c0                g_calibration
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 .data          0x200000e4       0x5c ./build/sensor.o
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                0x200000e4                last_reading
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                0x20000100                buffer
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                0x20000140                _edata = .
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.bss            0x20000140      0x800
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                0x20000140                _sbss = .
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 *(.bss*)
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 .bss           0x20000140      0x4c0 ./build/main.o
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                0x20000140                g_buffer
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                0x20000800                state_table
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 .bss           0x20000600      0x340 ./build/sensor.o
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                0x20000940                _ebss = .
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.stack          0x20000940      0x400
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                0x20000940                _sstack = .
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                0x20000d40                _estack = .
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Cross Reference Table
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Symbol                                            File
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HAL_Init                                          ./build/main.o
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                                                  ./build/sensor.o (HAL_Init)
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                                                  ./build/uart.o (HAL_Init)
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g_buffer                                          ./build/main.o
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                                                  ./build/sensor.o (g_buffer)
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...

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arm-none-eabi-ld: firmware.elf section `.bss' will not fit in region `RAM'
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arm-none-eabi-ld: region `RAM' overflowed by 4096 bytes

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__attribute__((section(".ccmram"))) static char buf[4096];

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Symbol                                            File
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my_function                                       ./build/main.o
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                                                  ./build/util.o
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                                                  ./build/sensor.o

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.isr_vector : {
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    KEEP(*(.isr_vector))
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}

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MEMORY {
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    FLASH (rx)  : ORIGIN = 0x08000000, LENGTH = 1024K
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    RAM   (rwx) : ORIGIN = 0x20000000, LENGTH = 128K
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    CCRAM (rwx) : ORIGIN = 0x10000000, LENGTH = 64K
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    SDRAM (rwx) : ORIGIN = 0xC0000000, LENGTH = 8M
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}
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SECTIONS {
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    ...
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    /* DMA 버퍼는 일반 SRAM에 (CCRAM은 DMA 불가) */
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    .dma_buf (NOLOAD) : {
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        *(.dma_buffers)
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    } > RAM
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    /* 핫 데이터는 CCRAM에 (DMA 접근 안 함) */
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    .ccram_data (NOLOAD) : {
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        *(.ccram*)
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    } > CCRAM
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    /* 큰 버퍼는 외부 SDRAM에 */
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    .sdram (NOLOAD) : {
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        *(.sdram*)
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    } > SDRAM
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}

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__attribute__((section(".ccram"))) static int g_hot_data[1024];
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__attribute__((section(".dma_buffers"))) static uint8_t dma_buf[4096];
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__attribute__((section(".sdram"))) static uint8_t image_buf[1024*1024];

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

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.stack (NOLOAD) : ALIGN(8) {
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    _sstack = .;
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    . = . + 0x1000;        /* 4KB */
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    _estack = .;
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} > RAM

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extern uint32_t _sstack, _estack;
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void check_stack() {
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    register uint32_t sp asm("sp");
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    if (sp < (uint32_t)&_sstack + 64) {
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        // 스택이 거의 다 찼다 — fault
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        while (1);
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    }
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}

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// PSPLIM 또는 MSPLIM 레지스터 설정 (CMSIS 매크로)
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__set_MSPLIM((uint32_t)&_sstack);