임베디드 C++ 링커 스크립트 — vtable·정적 객체 배치 추적

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MEMORY {
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    FLASH (rx)  : ORIGIN = 0x08000000, LENGTH = 1024K
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    RAM   (rwx) : ORIGIN = 0x20000000, LENGTH = 192K
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    CCM   (rwx) : ORIGIN = 0x10000000, LENGTH = 64K
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}

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SECTIONS {
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    .isr_vector : {
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        KEEP(*(.isr_vector))
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    } >FLASH
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    .text : {
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        *(.text*)
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        *(.rodata*)
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    } >FLASH
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    .data : {
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        *(.data*)
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    } >RAM AT >FLASH
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    .bss : {
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        *(.bss*)
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        *(COMMON)
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    } >RAM
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}

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int counter = 42;   // 초기값 42가 Flash, 런타임 사용은 RAM

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.data : {
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    _sdata = .;           /* RAM 시작 주소 */
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    *(.data*)
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    _edata = .;           /* RAM 끝 주소 */
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} >RAM AT >FLASH         /* VMA=RAM, LMA=FLASH */
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_sidata = LOADADDR(.data); /* Flash 위치 */

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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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.fini_array : {
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    PROVIDE_HIDDEN(__fini_array_start = .);
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    KEEP(*(SORT(.fini_array.*)))
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    KEEP(*(.fini_array))
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    PROVIDE_HIDDEN(__fini_array_end = .);
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} >FLASH

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/DISCARD/ : {
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    *(.eh_frame*)
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    *(.ARM.extab*)
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    *(.ARM.exidx*)
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}

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/* STM32F407 1MB Flash, 192KB RAM */
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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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    CCM   (rwx) : ORIGIN = 0x10000000, LENGTH = 64K
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}
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/* stack은 RAM 끝에서 시작 (downward 성장) */
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_estack = ORIGIN(RAM) + LENGTH(RAM);
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ENTRY(Reset_Handler)
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SECTIONS {
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    /* 0. Vector table — Flash 시작 */
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    .isr_vector : {
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        KEEP(*(.isr_vector))
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        . = ALIGN(4);
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    } >FLASH
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    /* 1. Code — Flash */
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    .text : {
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        . = ALIGN(4);
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        *(.text)
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        *(.text*)
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        *(.rodata)
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        *(.rodata*)
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        *(.glue_7)         /* ARM/Thumb interworking */
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        *(.glue_7t)
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        KEEP(*(.eh_frame))  /* keep if exceptions; else /DISCARD/ */
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        . = ALIGN(4);
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        _etext = .;
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    } >FLASH
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    /* 2. ARM exception index (예외 끄면 DISCARD) */
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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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    /* 3. C++ static 생성자 — Flash */
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    .preinit_array : {
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        PROVIDE_HIDDEN(__preinit_array_start = .);
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        KEEP(*(.preinit_array*))
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        PROVIDE_HIDDEN(__preinit_array_end = .);
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    } >FLASH
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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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    .fini_array : {
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        PROVIDE_HIDDEN(__fini_array_start = .);
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        KEEP(*(SORT(.fini_array.*)))
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        KEEP(*(.fini_array))
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        PROVIDE_HIDDEN(__fini_array_end = .);
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    } >FLASH
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    /* 4. .data — VMA=RAM, LMA=FLASH */
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    _sidata = LOADADDR(.data);
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    .data : {
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        . = ALIGN(4);
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        _sdata = .;
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        *(.data)
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        *(.data*)
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        . = ALIGN(4);
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        _edata = .;
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    } >RAM AT >FLASH
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    /* 5. .bss — RAM */
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    .bss : {
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        . = ALIGN(4);
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        _sbss = .;
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        __bss_start__ = _sbss;
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        *(.bss)
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        *(.bss*)
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        *(COMMON)
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        . = ALIGN(4);
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        _ebss = .;
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        __bss_end__ = _ebss;
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    } >RAM
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    /* 6. heap (newlib sbrk가 _end 사용) */
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    ._user_heap_stack : {
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        . = ALIGN(8);
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        PROVIDE(end = .);
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        PROVIDE(_end = .);
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        . = . + _Min_Heap_Size;
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        . = . + _Min_Stack_Size;
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        . = ALIGN(8);
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    } >RAM
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    /* 7. CCM RAM에 임의 데이터 배치 (선택) */
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    .ccmram : {
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        . = ALIGN(4);
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        _siccmram = LOADADDR(.ccmram);
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        _sccmram = .;
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        *(.ccmram)
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        *(.ccmram*)
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        . = ALIGN(4);
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        _eccmram = .;
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    } >CCM AT >FLASH
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    /* 8. 불필요 섹션 제거 */
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    /DISCARD/ : {
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        libc.a (*)
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        libm.a (*)
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        libgcc.a (*)
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    }
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}
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_Min_Heap_Size  = 0x200;   /* 512 bytes */
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_Min_Stack_Size = 0x400;   /* 1 KB */

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// 큰 DMA buffer를 CCM RAM에
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__attribute__((section(".ccmram")))
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uint8_t dma_buffer[4096];
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// 부트 시점에 .text 옆 const table
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__attribute__((section(".text.const_lut")))
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const uint8_t lookup_table[256] = { /* ... */ };

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// 큰 lookup 객체를 Flash에 직접
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__attribute__((section(".rodata.lookups")))
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const std::array<uint16_t, 1024> sin_table = { /* compile-time computed */ };
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// CCM에 두는 buffer pool
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__attribute__((section(".ccmram")))
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alignas(8) uint8_t packet_pool[8192];

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/* 링커 스크립트 */
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_sdata = .;
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*(.data*)
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_edata = .;

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// C++에서 사용
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extern "C" {
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    extern uint32_t _sdata;
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    extern uint32_t _edata;
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    extern uint32_t _sidata;
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}
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void copy_data() {
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    uint32_t* src = &_sidata;
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    uint32_t* dst = &_sdata;
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    while (dst < &_edata) *dst++ = *src++;
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}

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Memory Configuration
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Name             Origin             Length             Attributes
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FLASH            0x08000000         0x100000           rx
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RAM              0x20000000         0x20000            rwx
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CCM              0x10000000         0x10000            rwx
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Linker script and memory map
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...
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.text           0x08000000      0x4a3c
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                0x08000000        _stext = .
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 *(.text*)
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 .text          0x08000000      0x0034 build/startup.o
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                0x08000000                Reset_Handler
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 .text          0x08000034      0x0080 build/main.o
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                0x08000034                main
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 ...
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.init_array     0x08004b40       0x20
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                0x08004b40                PROVIDE_HIDDEN (__init_array_start = .)
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 *(.init_array)
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 .init_array    0x08004b40       0x18 build/main.o
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 .init_array    0x08004b58       0x04 build/logger.o
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 .init_array    0x08004b5c       0x04 build/timer.o
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                0x08004b60                PROVIDE_HIDDEN (__init_array_end = .)

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# Before: 일반 RAM
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.bss            32 KB  (4KB DMA buffer 포함)
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# After: DMA buffer를 CCM에
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.bss            28 KB
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.ccmram          4 KB