转自：

内核版本：2.6.14

glibc版本：2.3.6

CPU平台：arm

glic中其实有这些函数,当时用的uclib版本较低,没有这些函数,但又需要,只能自己实现了(较高的版本应该有这些函数,换版本很麻烦),而且可以加深自己对这方面的理解.原理性的东西就不深入讲解了,直接上例子!

 

#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <assert.h>
#include <ucontext.h>

void A(int a);
void B(int b);
void C(int c);
void DebugBacktrace(unsigned int sn , siginfo_t  *si , void *ptr);

typedef struct
{
    const char *dli_fname;  /* File name of defining object.  */
    void *dli_fbase;        /* Load address of that object.  */
    const char *dli_sname;  /* Name of nearest symbol.比如函数名*/
    void *dli_saddr;        /* Exact value of nearest symbol.比如函数的起始地址*/
} Dl_info;

struct ucontext_ce123 {
    unsigned long     uc_flags;
    struct ucontext  *uc_link;
    stack_t       uc_stack;
    struct sigcontext uc_mcontext;
    sigset_t      uc_sigmask;   /* mask last for extensibility */
}ucontext_ce123_;

struct sigframe_ce123 {
    struct sigcontext sc;//保存一组寄存器上下文
    unsigned long extramask[1];
    unsigned long retcode;//保存返回地址
    //struct aux_sigframe aux __attribute__((aligned(8)));
}sigframe_ce123;

int backtrace_ce123 (void **array, int size);
char ** backtrace_symbols_ce123 (void *const *array, int size);


int backtrace_ce123 (void **array, int size)
{
    if (size <= 0)
        return 0;

    int *fp = 0, *next_fp = 0;
    int cnt = 0;
    int ret = 0;

    __asm__(
        "mov %0, fp\n"
        : "=r"(fp)
    );


    array[cnt++] = (void *)(*(fp-1));

    next_fp = (int *)(*(fp-3));
    while((cnt <= size) && (next_fp != 0))
    {
        array[cnt++] = (void *)*(next_fp - 1);
        next_fp = (int *)(*(next_fp-3));
    }


    ret = ((cnt <= size)?cnt:size);
    printf("Backstrace (%d deep)\n", ret);

    return ret;
}

char ** backtrace_symbols_ce123 (void *const *array, int size)
{
# define WORD_WIDTH 8
    Dl_info info[size];
    int status[size];
    int cnt;
    size_t total = 0;
    char **result;

    /* Fill in the information we can get from `dladdr'.  */
    for (cnt = 0; cnt < size; ++cnt)
    {
        status[cnt] = _dl_addr (array[cnt], &info[cnt]);
        if (status[cnt] && info[cnt].dli_fname && info[cnt].dli_fname[0] != '\0')
        /* We have some info, compute the length of the string which will be
        "<file-name>(<sym-name>) [+offset].  */
        total += (strlen (info[cnt].dli_fname ?: "")
            + (info[cnt].dli_sname ? strlen (info[cnt].dli_sname) + 3 + WORD_WIDTH + 3 : 1)
            + WORD_WIDTH + 5);
        else
            total += 5 + WORD_WIDTH;
    }


    /* Allocate memory for the result.  */
    result = (char **) malloc (size * sizeof (char *) + total);
    if (result != NULL)
    {
        char *last = (char *) (result + size);

        for (cnt = 0; cnt < size; ++cnt)
        {
            result[cnt] = last;

            if (status[cnt] && info[cnt].dli_fname && info[cnt].dli_fname[0] != '\0')
            {
                char buf[20];

                if (array[cnt] >= (void *) info[cnt].dli_saddr)
                    sprintf (buf, "+%#lx", \
                        (unsigned long)(array[cnt] - info[cnt].dli_saddr));
                else
                    sprintf (buf, "-%#lx", \
                        (unsigned long)(info[cnt].dli_saddr - array[cnt]));

                last += 1 + sprintf (last, "%s%s%s%s%s[%p]",
                    info[cnt].dli_fname ?: "",
                    info[cnt].dli_sname ? "(" : "",
                    info[cnt].dli_sname ?: "",
                    info[cnt].dli_sname ? buf : "",
                    info[cnt].dli_sname ? ") " : " ",
                    array[cnt]);
            }
            else
                last += 1 + sprintf (last, "[%p]", array[cnt]);
        }
        assert (last <= (char *) result + size * sizeof (char *) + total);
    }

    return result;
}


void A(int a)
{
    printf("%d: A call B\n", a);
    B(2);
}

void B(int b)
{
    printf("%d: B call C\n", b);
    C(3);       /* 这个函数调用将导致段错误*/
}

void C(int c)
{
    char *p = (char *)c;
    *p = 'A';   /* 如果参数c不是一个可用的地址值，则这条语句导致段错误 */
    printf("%d: function C\n", c);
}

/* SIGSEGV信号的处理函数，回溯栈，打印函数的调用关系*/
void DebugBacktrace(unsigned int sn , siginfo_t  *si , void *ptr)
{
    /*int *ip = 0;
    __asm__(
        "mov %0, ip\n"
        : "=r"(ip)
    );
    printf("sp = 0x%x\n", ip);
    struct sigframe_ce123 * sigframe = (struct sigframe_ce123 * )ip;*/

    if(NULL != ptr)
    {
        printf("\n\nunhandled page fault (%d) at: 0x%08x\n", si->si_signo,si->si_addr);

        struct ucontext_ce123 *ucontext = (struct ucontext_ce123 *)ptr;
        int pc = ucontext->uc_mcontext.arm_pc;

        void *pc_array[1];
        pc_array[0] = pc;
        char **pc_name = backtrace_symbols_ce123(pc_array, 1);
        printf("%d: %s\n", 0, *pc_name);

#define SIZE 100
        void *array[SIZE];
        int size, i;
        char **strings;
        size = backtrace_ce123(array, SIZE);
        strings = backtrace_symbols_ce123(array, size);

        for(i=0;i<size;i++)
            printf("%d: %s\n", i+1, strings[i]);
        free(strings);
    }
    else
        printf("error!\n");
    exit(-1);
}

int main(int argc, char **argv)
{
    char a;

    struct sigaction s;
    s.sa_flags = SA_SIGINFO;
    s.sa_sigaction = (void *)DebugBacktrace;

    sigaction (SIGSEGV,&s,NULL);

    A(1);
    C(&a);

    return 0;

}

代码的下载地址：http://download.csdn.net/detail/ce123/5063160

编译命令：arm-linux-gcc -rdynamic -o segfault segfault.c

_dl_addr链接不通过时，使用-ldl。如果没有该函数，可用dladdr函数代替。