自己动手实现arm函数栈帧回溯

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。