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!

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#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。