임베디드 포스트모템 분석 — Core Dump와 Field Crash

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#define DUMP_MAGIC 0xC0FFEE00
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typedef struct {
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    uint32_t magic;
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    uint32_t reset_reason;     /* RCC->CSR snapshot */
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    uint32_t pc, lr, psr;
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    uint32_t cfsr, hfsr, bfar, mmar;
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    uint32_t r0_r3[4];
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    uint32_t r12;
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    uint32_t stack[64];        /* fault 직전 stack top */
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    uint32_t log_tail;         /* log ring tail */
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    uint8_t  log[2048];        /* 최근 log */
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} __attribute__((packed)) mini_dump_t;
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void hardfault_save_dump(uint32_t *sp) {
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    mini_dump_t *d = (mini_dump_t*)BACKUP_SRAM;
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    d->magic = DUMP_MAGIC;
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    d->reset_reason = RCC->CSR;
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    d->r0_r3[0] = sp[0];
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    d->r0_r3[1] = sp[1];
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    d->r0_r3[2] = sp[2];
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    d->r0_r3[3] = sp[3];
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    d->r12 = sp[4];
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    d->lr  = sp[5];
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    d->pc  = sp[6];
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    d->psr = sp[7];
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    d->cfsr = *(volatile uint32_t*)0xE000ED28;
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    d->hfsr = *(volatile uint32_t*)0xE000ED2C;
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    d->bfar = *(volatile uint32_t*)0xE000ED38;
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    d->mmar = *(volatile uint32_t*)0xE000ED34;
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    memcpy(d->stack, sp, sizeof(d->stack));
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    memcpy(d->log, g_log_ring, sizeof(d->log));
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    d->log_tail = g_log_tail;
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    NVIC_SystemReset();
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}

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void boot_check_dump(void) {
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    mini_dump_t *d = (mini_dump_t*)BACKUP_SRAM;
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    if (d->magic == DUMP_MAGIC) {
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        printf("Previous crash detected:\n");
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        printf("PC=0x%08lx CFSR=0x%08lx BFAR=0x%08lx\n",
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               d->pc, d->cfsr, d->bfar);
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        if (network_available()) {
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            send_dump_to_cloud(d, sizeof(*d));
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        } else {
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            store_dump_to_flash(d);   /* 다음 connect 시 전송 */
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        }
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        d->magic = 0;
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    }
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}

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#define LAST_GASP_N 128
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typedef struct {
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    uint32_t ts;
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    uint16_t code;
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    uint16_t arg;
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} __attribute__((packed)) gasp_t;
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static volatile gasp_t g_gasp[LAST_GASP_N];
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static volatile uint16_t g_gasp_idx;
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static inline void gasp_log(uint16_t code, uint16_t arg) {
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    uint16_t i = g_gasp_idx++ & (LAST_GASP_N - 1);
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    g_gasp[i].ts   = DWT->CYCCNT;
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    g_gasp[i].code = code;
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    g_gasp[i].arg  = arg;
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}

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extern uint32_t _stack_bottom;
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*(uint32_t*)&_stack_bottom = 0xCAFEDEAD;
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void watch_stack(void) {
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    if (*(uint32_t*)&_stack_bottom != 0xCAFEDEAD) {
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        gasp_log(GASP_STACK_OVERFLOW, 0);
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        hardfault_save_dump(NULL);
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    }
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}

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typedef enum {
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    RESET_POWER   = 1 << 0,
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    RESET_PIN     = 1 << 1,
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    RESET_SW      = 1 << 2,
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    RESET_IWDG    = 1 << 3,
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    RESET_WWDG    = 1 << 4,
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    RESET_LOWPWR  = 1 << 5,
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    RESET_BOR     = 1 << 6,
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} reset_reason_t;
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reset_reason_t get_reset_reason(void) {
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    uint32_t csr = RCC->CSR;
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    reset_reason_t r = 0;
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    if (csr & RCC_CSR_PORRSTF)  r |= RESET_POWER;
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    if (csr & RCC_CSR_PINRSTF)  r |= RESET_PIN;
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    if (csr & RCC_CSR_SFTRSTF)  r |= RESET_SW;
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    if (csr & RCC_CSR_IWDGRSTF) r |= RESET_IWDG;
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    if (csr & RCC_CSR_WWDGRSTF) r |= RESET_WWDG;
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    if (csr & RCC_CSR_LPWRRSTF) r |= RESET_LOWPWR;
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    if (csr & RCC_CSR_BORRSTF)  r |= RESET_BOR;
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    RCC->CSR |= RCC_CSR_RMVF;    /* clear */
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    return r;
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}

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device-A: PC=0x08001234 CFSR=0x00008200 BFAR=0x00000004
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device-B: PC=0x08001234 CFSR=0x00008200 BFAR=0x00000004
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device-C: PC=0x08001236 CFSR=0x00008200 BFAR=0x00000004    ← PC가 약간 다름

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mini_dump_t dump;   /* .bss에 위치 → 부팅 시 0으로 clear */

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__attribute__((section(".noinit"))) mini_dump_t dump;

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__attribute__((naked))
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void HardFault_Handler(void) {
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    __asm volatile (
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        "ldr  sp, =_temp_dump_stack \n"   /* fault용 별도 stack */
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        "b    hardfault_save_dump   \n"
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    );
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}