CmBacktrace / 四六文摘

Foreword

CmBacktrace （Cortex Microcontroller Backtrace）是一款针对 ARM Cortex-M 系列 MCU 的错误代码自动追踪、定位，错误原因自动分析的开源库。主要特性如下：

支持的错误包括：断言（assert）故障（Hard Fault, Memory Management Fault, Bus Fault, Usage Fault, Debug Fault）故障原因自动诊断：可在故障发生时，自动分析出故障的原因，定位发生故障的代码位置，而无需再手动分析繁杂的故障寄存器；输出错误现场的函数调用栈（需配合 addr2line 工具进行精确定位），还原发生错误时的现场信息，定位问题代码位置、逻辑更加快捷、精准。也可以在正常状态下使用该库，获取当前的函数调用栈；支持裸机及以下操作系统平台： RT-Thread UCOS FreeRTOS（需修改源码）根据错误现场状态，输出对应的线程栈或 C 主栈；故障诊断信息支持多国语言（目前：简体中文、英文）；适配 Cortex-M0/M3/M4/M7 MCU；支持 IAR、KEIL、GCC 编译器；

https://github.com/armink/CmBacktrace

从介绍上来说，非常友好，发生断言，Hard Fault 等情况可以帮忙记录故障原因，打印输出寄存器状态，堆栈等内容，实际使用时配合 Flash 保存这些信息也非常容易，从而在一个复杂系统中可以找到某些隐藏的BUG，进而提升产品的稳定性，非常不错

详细的介绍在 github 上也有，当然直接看源码更合适。

Source Code

cmb_cfg.h

#ifndef _CMB_CFG_H_
#define _CMB_CFG_H_

/* print line, must config by user */
#define cmb_println(...)     /* e.g., printf(__VA_ARGS__);printf("\r\n") */

    首先 ... 表示给入的参数是一个不定长度的参数， __VA_ARGS__ 则是把这个参数列表给传入
    对应使用的函数中，需要注意的是 ... 只能代替最后面的宏参数

/* enable bare metal(no OS) platform */
/* #define CMB_USING_BARE_METAL_PLATFORM */
/* enable OS platform */
#define CMB_USING_OS_PLATFORM

/* OS platform type, must config when CMB_USING_OS_PLATFORM is enable */
/* #define CMB_OS_PLATFORM_TYPE           CMB_OS_PLATFORM_RTT or CMB_OS_PLATFORM_UCOSII or CMB_OS_PLATFORM_UCOSIII or CMB_OS_PLATFORM_FREERTOS */
#define CMB_OS_PLATFORM_TYPE           CMB_OS_PLATFORM_FREERTOS

/* cpu platform type, must config by user */
/* #define CMB_CPU_PLATFORM_TYPE           CMB_CPU_ARM_CORTEX_M0 or CMB_CPU_ARM_CORTEX_M3 or CMB_CPU_ARM_CORTEX_M4 or CMB_CPU_ARM_CORTEX_M7 */
#define CMB_CPU_PLATFORM_TYPE          CMB_CPU_ARM_CORTEX_M7

/* enable dump stack information */
#define CMB_USING_DUMP_STACK_INFO

/* language of print information */
/* #define CMB_PRINT_LANGUAGE             CMB_PRINT_LANGUAGE_ENGLISH(default) or CMB_PRINT_LANUUAGE_CHINESE */

#endif /* _CMB_CFG_H_ */

cmb_fault.S

AREA |.text|, CODE, READONLY, ALIGN=2
THUMB
REQUIRE8
PRESERVE8

; NOTE: If use this file's HardFault_Handler, please comments the HardFault_Handler code on other file.
IMPORT cm_backtrace_fault
EXPORT HardFault_Handler

HardFault_Handler    PROC
MOV     r0, lr                  ; get lr
MOV     r1, sp                  ; get stack pointer (current is MSP)
BL      cm_backtrace_fault

Fault_Loop
BL      Fault_Loop              ;while(1)
ENDP

END

这里是重写了 HardFault 的中断处理函数，通过把 lr 和 sp 存入 r0 r1 （他们作为参数）调用 cm_backtrace_fault 进行错误追踪处理，处理结束后程序死在这里。

由于这里重构了 HardFault 中断，那么原本的中断函数就需要注释掉了，当然也可以自己重写Hard Fault ，不用他这里的 HardFault 。

cmb_def.h

定义了许多会使用到的寄存器结构体，以及和 OS、编译器、平台相关的宏定义

cm_backtrace.h

#ifndef _CORTEXM_BACKTRACE_H_
#define _CORTEXM_BACKTRACE_H_

#include "cmb_def.h"

void cm_backtrace_init(const char *firmware_name, const char *hardware_ver, const char *software_ver);
void cm_backtrace_firmware_info(void);
size_t cm_backtrace_call_stack(uint32_t *buffer, size_t size, uint32_t sp);
void cm_backtrace_assert(uint32_t sp);
void cm_backtrace_fault(uint32_t fault_handler_lr, uint32_t fault_handler_sp);

#endif /* _CORTEXM_BACKTRACE_H_ */

这里定义了几个会被调用的函数

其中 cm_backtrace_init 需要在系统启动之后立马进行初始化，保证可以在出错之前完成

cm_backtrace_fault 就是 HardFault 调用的处理函数

cm_backtrace_assert 是系统断言中必须要加入的函数

cm_backtrace_call_stack 和 cm_backtrace_firmware_info 则是断言和 HardFault 调用的子函数

cm_backtrace.c

void cm_backtrace_init(const char *firmware_name, const char *hardware_ver, const char *software_ver) {
    strncpy(fw_name, firmware_name, CMB_NAME_MAX);
    strncpy(hw_ver, hardware_ver, CMB_NAME_MAX);
    strncpy(sw_ver, software_ver, CMB_NAME_MAX);
    设定好对应的固件名 硬件版本 软件版本（这里的软件版本其实可以对应git commit号）

#if defined(__CC_ARM)
    main_stack_start_addr = (uint32_t)&CSTACK_BLOCK_START(CMB_CSTACK_BLOCK_NAME);
    main_stack_size = (uint32_t)&CSTACK_BLOCK_END(CMB_CSTACK_BLOCK_NAME) - main_stack_start_addr;
    code_start_addr = (uint32_t)&CODE_SECTION_START(CMB_CODE_SECTION_NAME);
    code_size = (uint32_t)&CODE_SECTION_END(CMB_CODE_SECTION_NAME) - code_start_addr;
#elif defined(__ICCARM__)
    main_stack_start_addr = (uint32_t)__section_begin(CMB_CSTACK_BLOCK_NAME);
    main_stack_size = (uint32_t)__section_end(CMB_CSTACK_BLOCK_NAME) - main_stack_start_addr;
    code_start_addr = (uint32_t)__section_begin(CMB_CODE_SECTION_NAME);
    code_size = (uint32_t)__section_end(CMB_CODE_SECTION_NAME) - code_start_addr;
#elif defined(__GNUC__)
    main_stack_start_addr = (uint32_t)(&CMB_CSTACK_BLOCK_START);
    main_stack_size = (uint32_t)(&CMB_CSTACK_BLOCK_END) - main_stack_start_addr;
    code_start_addr = (uint32_t)(&CMB_CODE_SECTION_START);
    code_size = (uint32_t)(&CMB_CODE_SECTION_END) - code_start_addr;
#else
    #error "not supported compiler"
#endif
    根据编译器决定具体的栈地址 栈大小，代码区地址，代码大小

    init_ok = true;
}

打印硬件信息

void cm_backtrace_firmware_info(void) {
    cmb_println(print_info[PRINT_FIRMWARE_INFO], fw_name, hw_ver, sw_ver);
}

如果是在用户态发生的问题，也就是 thread 中出现的问题，根据 OS 获取对应的线程栈地址和大小

static void get_cur_thread_stack_info(uint32_t sp, uint32_t *start_addr, size_t *size) {
    CMB_ASSERT(start_addr);
    CMB_ASSERT(size);

#if (CMB_OS_PLATFORM_TYPE == CMB_OS_PLATFORM_RTT)
    *start_addr = (uint32_t) rt_thread_self()->stack_addr;
    *size = rt_thread_self()->stack_size;
#elif (CMB_OS_PLATFORM_TYPE == CMB_OS_PLATFORM_UCOSII)
    extern OS_TCB *OSTCBCur;

    *start_addr = (uint32_t) OSTCBCur->OSTCBStkBottom;
    *size = OSTCBCur->OSTCBStkSize * sizeof(OS_STK);
#elif (CMB_OS_PLATFORM_TYPE == CMB_OS_PLATFORM_UCOSIII)
    #error "not implemented, I hope you can do this"
    //TODO 待实现
#elif (CMB_OS_PLATFORM_TYPE == CMB_OS_PLATFORM_FREERTOS)
    *start_addr = (uint32_t)vTaskStackAddr();
    *size = vTaskStackSize() * sizeof( StackType_t );
#endif
}

获取出错任务的任务名

static const char *get_cur_thread_name(void) {
#if (CMB_OS_PLATFORM_TYPE == CMB_OS_PLATFORM_RTT)
    return rt_thread_self()->name;
#elif (CMB_OS_PLATFORM_TYPE == CMB_OS_PLATFORM_UCOSII)
    extern OS_TCB *OSTCBCur;

#if OS_TASK_NAME_SIZE > 0 || OS_TASK_NAME_EN > 0
        return (const char *)OSTCBCur->OSTCBTaskName;
#else
        return NULL;
#endif /* OS_TASK_NAME_SIZE > 0 || OS_TASK_NAME_EN > 0 */

#elif (CMB_OS_PLATFORM_TYPE == CMB_OS_PLATFORM_UCOSIII)
    #error "not implemented, I hope you can do this"
    //TODO 待实现
#elif (CMB_OS_PLATFORM_TYPE == CMB_OS_PLATFORM_FREERTOS)
    return vTaskName();
#endif
}

打印出错任务的所有栈内容

static void dump_cur_thread_stack(uint32_t stack_start_addr, size_t stack_size, uint32_t *stack_pointer) {
    cmb_println(print_info[PRINT_THREAD_STACK_INFO]);
    for (; (uint32_t) stack_pointer < stack_start_addr + stack_size; stack_pointer++) {
        cmb_println("  addr: %08x    data: %08x", stack_pointer, *stack_pointer);
    }
    cmb_println("====================================");
}

打印当前系统的栈内容

static void dump_main_stack(uint32_t stack_start_addr, size_t stack_size, uint32_t *stack_pointer) {
    cmb_println(print_info[PRINT_MAIN_STACK_INFO]);
    for (; (uint32_t) stack_pointer < stack_start_addr + stack_size; stack_pointer++) {
        cmb_println("  addr: %08x    data: %08x", stack_pointer, *stack_pointer);
    }
    cmb_println("====================================");
}

通过这里获取对应的栈中调用的所有函数信息

size_t cm_backtrace_call_stack(uint32_t *buffer, size_t size, uint32_t sp) {
    uint32_t stack_start_addr = main_stack_start_addr, pc;
    size_t depth = 0, stack_size = main_stack_size;
    bool regs_saved_lr_is_valid = false;

    if (on_fault) {
        /* first depth is PC */
        buffer[depth++] = regs.saved.pc;
        /* second depth is from LR, so need decrease a word to PC */
        pc = regs.saved.lr - sizeof(size_t);
        if ((pc >= code_start_addr) && (pc <= code_start_addr + code_size) && (depth < CMB_CALL_STACK_MAX_DEPTH)
                && (depth < size)) {
            buffer[depth++] = pc;
            regs_saved_lr_is_valid = true;
        }

#ifdef CMB_USING_OS_PLATFORM
        /* program is running on thread before fault */
        if (on_thread_before_fault) {
            get_cur_thread_stack_info(sp, &stack_start_addr, &stack_size);
        }
    } else {
        /* OS environment */
        if (cmb_get_sp() == cmb_get_psp()) {
            get_cur_thread_stack_info(sp, &stack_start_addr, &stack_size);
        }
#endif /* CMB_USING_OS_PLATFORM */

    }

    /* copy called function address */
    for (; sp < stack_start_addr + stack_size; sp += sizeof(size_t)) {
        /* the *sp value may be LR, so need decrease a word to PC */
        pc = *((uint32_t *) sp) - sizeof(size_t);
        if ((pc >= code_start_addr) && (pc <= code_start_addr + code_size) && (depth < CMB_CALL_STACK_MAX_DEPTH)
                && (depth < size)) {
            /* the second depth function may be already saved, so need ignore repeat */
            if ((depth == 2) && regs_saved_lr_is_valid && (pc == buffer[1])) {
                continue;
            }
            buffer[depth++] = pc;
        }
    }

    return depth;
}

这里则是通过调用上面的函数，打印出来所有的调用栈信息

static void print_call_stack(uint32_t sp) {
    size_t i, cur_depth = 0;
    uint32_t call_stack_buf[CMB_CALL_STACK_MAX_DEPTH] = {0};

    cur_depth = cm_backtrace_call_stack(call_stack_buf, CMB_CALL_STACK_MAX_DEPTH, sp);

    for (i = 0; i < cur_depth; i++) {
        sprintf(call_stack_info + i * (8 + 1), "%08lx", call_stack_buf[i]);
        call_stack_info[i * (8 + 1) + 8] = ' ';
    }

    if (cur_depth) {
        cmb_println(print_info[PRINT_CALL_STACK_INFO], fw_name, CMB_ELF_FILE_EXTENSION_NAME, cur_depth * (8 + 1),
                call_stack_info);
    } else {
        cmb_println(print_info[PRINT_CALL_STACK_ERR]);
    }
}

断言函数

void cm_backtrace_assert(uint32_t sp) {
    CMB_ASSERT(init_ok);

#ifdef CMB_USING_OS_PLATFORM
    uint32_t cur_stack_pointer = cmb_get_sp();
#endif

    cmb_println("");
    cm_backtrace_firmware_info();

#ifdef CMB_USING_OS_PLATFORM
    /* OS environment */
    这里是根据是中断中发生 ASSERT 还是线程中发生 ASSERT 来决定输出内容
    if (cur_stack_pointer == cmb_get_msp()) {
        cmb_println(print_info[PRINT_ASSERT_ON_HANDLER]);

#ifdef CMB_USING_DUMP_STACK_INFO
        dump_main_stack(main_stack_start_addr, main_stack_size, (uint32_t *) sp);
#endif /* CMB_USING_DUMP_STACK_INFO */

    } else if (cur_stack_pointer == cmb_get_psp()) {
        cmb_println(print_info[PRINT_ASSERT_ON_THREAD], get_cur_thread_name());

#ifdef CMB_USING_DUMP_STACK_INFO
        uint32_t stack_start_addr;
        size_t stack_size;
        get_cur_thread_stack_info(sp, &stack_start_addr, &stack_size);
        dump_cur_thread_stack(stack_start_addr, stack_size, (uint32_t *) sp);
#endif /* CMB_USING_DUMP_STACK_INFO */

    }

#else

    /* bare metal(no OS) environment */
#ifdef CMB_USING_DUMP_STACK_INFO
    dump_main_stack(main_stack_start_addr, main_stack_size, (uint32_t *) sp);
#endif /* CMB_USING_DUMP_STACK_INFO */

#endif /* CMB_USING_OS_PLATFORM */

    print_call_stack(sp);
}

根据获取到的状态寄存器等判断具体是什么出错

static void fault_diagnosis(void) {
    if (regs.hfsr.bits.VECTBL) {
        cmb_println(print_info[PRINT_HFSR_VECTBL]);
    }
    if (regs.hfsr.bits.FORCED) {
        /* Memory Management Fault */
        if (regs.mfsr.value) {
            if (regs.mfsr.bits.IACCVIOL) {
                cmb_println(print_info[PRINT_MFSR_IACCVIOL]);
            }
            if (regs.mfsr.bits.DACCVIOL) {
                cmb_println(print_info[PRINT_MFSR_DACCVIOL]);
            }
            if (regs.mfsr.bits.MUNSTKERR) {
                cmb_println(print_info[PRINT_MFSR_MUNSTKERR]);
            }
            if (regs.mfsr.bits.MSTKERR) {
                cmb_println(print_info[PRINT_MFSR_MSTKERR]);
            }

    ...

    /* Debug Fault */
    if (regs.hfsr.bits.DEBUGEVT) {
        if (regs.dfsr.value) {
            if (regs.dfsr.bits.HALTED) {
                cmb_println(print_info[PRINT_DFSR_HALTED]);
            }
            if (regs.dfsr.bits.BKPT) {
                cmb_println(print_info[PRINT_DFSR_BKPT]);
            }
            if (regs.dfsr.bits.DWTTRAP) {
                cmb_println(print_info[PRINT_DFSR_DWTTRAP]);
            }
            if (regs.dfsr.bits.VCATCH) {
                cmb_println(print_info[PRINT_DFSR_VCATCH]);
            }
            if (regs.dfsr.bits.EXTERNAL) {
                cmb_println(print_info[PRINT_DFSR_EXTERNAL]);
            }
        }
    }
}

如果是 M4 或者是 M7 由于自带了 FPU ，出错时如果开启了 FPU sp 中存的内容有很大一部分是与 FPU 有关的，所以需要排除这一部分

#if (CMB_CPU_PLATFORM_TYPE == CMB_CPU_ARM_CORTEX_M4) || (CMB_CPU_PLATFORM_TYPE == CMB_CPU_ARM_CORTEX_M7)
static uint32_t statck_del_fpu_regs(uint32_t fault_handler_lr, uint32_t sp) {
    statck_has_fpu_regs = (fault_handler_lr & (1UL << 4)) == 0 ? true : false;

    /* the stack has S0~S15 and FPSCR registers when statck_has_fpu_regs is true, double word align */
    return statck_has_fpu_regs == true ? sp + sizeof(size_t) * 18 : sp;
}
#endif

最重要的追踪函数主体

void cm_backtrace_fault(uint32_t fault_handler_lr, uint32_t fault_handler_sp) {

    获取到栈指针
    uint32_t stack_pointer = fault_handler_sp, saved_regs_addr = stack_pointer;
    const char *regs_name[] = { "R0 ", "R1 ", "R2 ", "R3 ", "R12", "LR ", "PC ", "PSR" };

#ifdef CMB_USING_DUMP_STACK_INFO
    拿到系统堆栈信息
    uint32_t stack_start_addr = main_stack_start_addr;
    size_t stack_size = main_stack_size;
#endif

    确保被初始化过，否则系统堆栈信息等都可能是错的
    CMB_ASSERT(init_ok);
    /* only call once */
    CMB_ASSERT(!on_fault);

    on_fault = true;

    cmb_println("");
    cm_backtrace_firmware_info();

#ifdef CMB_USING_OS_PLATFORM
    有操作系统下，判断出问题点是在中断还是线程部分，打印相关信息
    on_thread_before_fault = fault_handler_lr & (1UL << 2);
    /* check which stack was used before (MSP or PSP) */
    if (on_thread_before_fault) {
        cmb_println(print_info[PRINT_FAULT_ON_THREAD], get_cur_thread_name() != NULL ? get_cur_thread_name() : "NO_NAME");
        saved_regs_addr = stack_pointer = cmb_get_psp();

#ifdef CMB_USING_DUMP_STACK_INFO
        get_cur_thread_stack_info(stack_pointer, &stack_start_addr, &stack_size);
#endif /* CMB_USING_DUMP_STACK_INFO */

    } else {
        cmb_println(print_info[PRINT_FAULT_ON_HANDLER]);
    }
#else
    /* bare metal(no OS) environment */
    cmb_println(print_info[PRINT_FAULT_ON_HANDLER]);
#endif /* CMB_USING_OS_PLATFORM */

    /* delete saved R0~R3, R12, LR,PC,xPSR registers space */
    stack_pointer += sizeof(size_t) * 8;

#if (CMB_CPU_PLATFORM_TYPE == CMB_CPU_ARM_CORTEX_M4) || (CMB_CPU_PLATFORM_TYPE == CMB_CPU_ARM_CORTEX_M7)
    stack_pointer = statck_del_fpu_regs(fault_handler_lr, stack_pointer);
#endif /* (CMB_CPU_PLATFORM_TYPE == CMB_CPU_ARM_CORTEX_M4) || (CMB_CPU_PLATFORM_TYPE == CMB_CPU_ARM_CORTEX_M7) */

    输出栈中所有内容
    /* dump stack information */
#ifdef CMB_USING_DUMP_STACK_INFO
#ifdef CMB_USING_OS_PLATFORM
    if (on_thread_before_fault) {
        dump_cur_thread_stack(stack_start_addr, stack_size, (uint32_t *) stack_pointer);
    } else {
        dump_main_stack(stack_start_addr, stack_size, (uint32_t *) stack_pointer);
    }
#else
    /* bare metal(no OS) environment */
    dump_main_stack(stack_start_addr, stack_size, (uint32_t *) stack_pointer);
#endif /* CMB_USING_OS_PLATFORM */
#endif /* CMB_USING_DUMP_STACK_INFO */

    输出寄存器中的信息
    /* dump register */
    cmb_println(print_info[PRINT_REGS_TITLE]);

    regs.saved.r0        = ((uint32_t *)saved_regs_addr)[0];  // Register R0
    regs.saved.r1        = ((uint32_t *)saved_regs_addr)[1];  // Register R1
    regs.saved.r2        = ((uint32_t *)saved_regs_addr)[2];  // Register R2
    regs.saved.r3        = ((uint32_t *)saved_regs_addr)[3];  // Register R3
    regs.saved.r12       = ((uint32_t *)saved_regs_addr)[4];  // Register R12
    regs.saved.lr        = ((uint32_t *)saved_regs_addr)[5];  // Link register LR
    regs.saved.pc        = ((uint32_t *)saved_regs_addr)[6];  // Program counter PC
    regs.saved.psr.value = ((uint32_t *)saved_regs_addr)[7];  // Program status word PSR

    cmb_println("  %s: %08x  %s: %08x  %s: %08x  %s: %08x", regs_name[0], regs.saved.r0,
                                                            regs_name[1], regs.saved.r1,
                                                            regs_name[2], regs.saved.r2,
                                                            regs_name[3], regs.saved.r3);
    cmb_println("  %s: %08x  %s: %08x  %s: %08x  %s: %08x", regs_name[4], regs.saved.r12,
                                                            regs_name[5], regs.saved.lr,
                                                            regs_name[6], regs.saved.pc,
                                                            regs_name[7], regs.saved.psr.value);
    cmb_println("==============================================================");

    /* the Cortex-M0 is not support fault diagnosis */
#if (CMB_CPU_PLATFORM_TYPE != CMB_CPU_ARM_CORTEX_M0)
    regs.syshndctrl.value = CMB_SYSHND_CTRL;  // System Handler Control and State Register
    regs.mfsr.value       = CMB_NVIC_MFSR;    // Memory Fault Status Register
    regs.mmar             = CMB_NVIC_MMAR;    // Memory Management Fault Address Register
    regs.bfsr.value       = CMB_NVIC_BFSR;    // Bus Fault Status Register
    regs.bfar             = CMB_NVIC_BFAR;    // Bus Fault Manage Address Register
    regs.ufsr.value       = CMB_NVIC_UFSR;    // Usage Fault Status Register
    regs.hfsr.value       = CMB_NVIC_HFSR;    // Hard Fault Status Register
    regs.dfsr.value       = CMB_NVIC_DFSR;    // Debug Fault Status Register
    regs.afsr             = CMB_NVIC_AFSR;    // Auxiliary Fault Status Register

    fault_diagnosis();
#endif

    print_call_stack(stack_pointer);
}

查错

当发生错误以后，使用 addr2line 命令，查看函数调用栈详细信息，并定位错误代码

Addr2line 工具（它是标准的 GNU Binutils 中的一部分）是一个可以将指令的地址和可执行映像转换成文件名、函数名和源代码行数的工具。这种功能对于将跟踪地址转换成更有意义的内容来说简直是太棒了。

通过上面的函数，会在串口或者什么其他输出地方，输出栈的函数指针的具体地址，进而就可以定位出来具体是哪行出错了，当然调用 addr2line 命令应该在程序的 bin/mot/elf 文件目录下

如下，只需要到对应的目录下执行下面的代码即可

Firmware name: xxxxx, hardware version: xxxxx, software version: xxxxx
Fault on thread God
=================== Registers information ====================
  R0 : 2000ba2c  R1 : 2000903c  R2 : 00140006  R3 : 00140006
  R12: 2000a594  LR : 0807a5ad  PC : 08076ea8  PSR: 01070000
==============================================================
Bus fault is caused by precise data access violation
The bus fault occurred address is 0014000e
Show more call stack info by run: addr2line -e xxxx.elf -a -f 08076ea8 0807a5a9 0807d9dc 080769bf 0807d9d9 0807d517 0807d32b 080563bd 0804c207 0804c357 0804e65b 0804f89d 0804f6c7 080742af 080742c1 08077005

Summary

总的来说大部分和寄存器以及出错相关的信息基本都来自于

Cortex M3 Technical Reference Manual
Cortex M4 Technical Reference Manual
Cortex M7 Technical Reference Manual

如果只用 trace 还不够完美，需要有一个用来长时间保存出错信息的记录功能。

比如把所有出错信息写到 flash 中去，或者是 log 记录中去。

CmBacktrace 的作者也提供了对应的功能，不过其中用 flash 来做数据库，有点没意义。 flash 烧写次数有限，而且刷写新内容时需要 sector 式的擦除，对于每条数据存储也需要定义严格的格式不是很推荐吧，会上数据库的应用，也不会差一个 SD 的。

当然你也可以在 CmBacktrace 中增加一些其他信息的代码，比如当发生错误以后，如果能获取到电池电量的话，尽量获取到，然后输出，因为很有可能是因为低电触发了什么异常情况，而这种情况很可能并不一定，什么都有，所以用低电排除一些没必要追究的异常，是有意义的

Quote

http://blog.csdn.net/jean_bai/article/details/45952247

https://github.com/armink/CmBacktrace

https://github.com/armink/EasyLogger

https://github.com/armink/EasyFlash

http://blog.csdn.net/lhf_tiger/article/details/9088609

https://www.ibm.com/developerworks/cn/linux/l-graphvis/

http://blog.csdn.net/whz_zb/article/details/7604760

CmBacktrace

Foreword

Source Code

cmb_cfg.h

cmb_fault.S

cmb_def.h

cm_backtrace.h

cm_backtrace.c

查错

Summary

Quote

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