捕捉信号SIGSEGV并回溯栈帧

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引出问题

在嵌入式应用程序开发过程中，调试一直是个老大难问题 -- 由于环境的限制，当程序发生段错误时不能很好的定位到底是哪里出现了错误，如果在程序发生段错误时能够清晰明了地看到程序的栈帧链，那无疑是雪中送炭。本文就捕捉信号SIGSEGV并在该信号的处理函数中打印出函数栈帧链来帮助我们调试程序。

本文的程序适合ARM和X86平台。

回溯栈帧原理

理解函数栈帧的布局后，那么自然明白回溯栈帧的原理了，这里不多解释了，直接上图（来自网络）：

x86函数栈帧结构

ARM函数栈帧结构

代码sigsegv.c

#ifndef _GNU_SOURCE#define _GNU_SOURCE#endif#include <stdio.h>#include <dlfcn.h>#include <stdlib.h>#include <signal.h>#include <unistd.h>#include <string.h>#include <ucontext.h>/* 纯C环境下，不定义宏NO_CPP_DEMANGLE */#if (!defined(__cplusplus)) && (!defined(NO_CPP_DEMANGLE))#define NO_CPP_DEMANGLE#endif#ifndef NO_CPP_DEMANGLE    #include <cxxabi.h>    #ifdef __cplusplus    using __cxxabiv1::__cxa_demangle;    #endif#endif#ifdef HAS_ULSLIB#include <uls/logger.h>#define sigsegv_outp(x)sigsegv_outp(, gx)#else#define sigsegv_outp(x, ...) fprintf(stderr, x"\n", ##__VA_ARGS__)#endif#if (defined __x86_64__)#define REGFORMAT   "%016lx"#elif (defined __i386__)#define REGFORMAT   "%08x"#elif (defined __arm__)#define REGFORMAT   "%lx"#endifstatic void print_reg(ucontext_t *uc) {#if (defined __x86_64__) || (defined __i386__)int i;for (i = 0; i < NGREG; i++) {sigsegv_outp("reg[%02d]: 0x"REGFORMAT, i, uc->uc_mcontext.gregs[i]);}#elif (defined __arm__)sigsegv_outp("reg[%02d]= 0x"REGFORMAT, 0, uc->uc_mcontext.arm_r0);sigsegv_outp("reg[%02d]= 0x"REGFORMAT, 1, uc->uc_mcontext.arm_r1);sigsegv_outp("reg[%02d]= 0x"REGFORMAT, 2, uc->uc_mcontext.arm_r2);sigsegv_outp("reg[%02d]= 0x"REGFORMAT, 3, uc->uc_mcontext.arm_r3);sigsegv_outp("reg[%02d]= 0x"REGFORMAT, 4, uc->uc_mcontext.arm_r4);sigsegv_outp("reg[%02d]= 0x"REGFORMAT, 5, uc->uc_mcontext.arm_r5);sigsegv_outp("reg[%02d]= 0x"REGFORMAT, 6, uc->uc_mcontext.arm_r6);sigsegv_outp("reg[%02d]= 0x"REGFORMAT, 7, uc->uc_mcontext.arm_r7);sigsegv_outp("reg[%02d]= 0x"REGFORMAT, 8, uc->uc_mcontext.arm_r8);sigsegv_outp("reg[%02d]= 0x"REGFORMAT, 9, uc->uc_mcontext.arm_r9);sigsegv_outp("reg[%02d]= 0x"REGFORMAT, 10, uc->uc_mcontext.arm_r10);sigsegv_outp("FP= 0x"REGFORMAT, uc->uc_mcontext.arm_fp);sigsegv_outp("IP= 0x"REGFORMAT, uc->uc_mcontext.arm_ip);sigsegv_outp("SP= 0x"REGFORMAT, uc->uc_mcontext.arm_sp);sigsegv_outp("LR= 0x"REGFORMAT, uc->uc_mcontext.arm_lr);sigsegv_outp("PC= 0x"REGFORMAT, uc->uc_mcontext.arm_pc);sigsegv_outp("CPSR= 0x"REGFORMAT, uc->uc_mcontext.arm_cpsr);sigsegv_outp("Fault Address= 0x"REGFORMAT, uc->uc_mcontext.fault_address);sigsegv_outp("Trap no= 0x"REGFORMAT, uc->uc_mcontext.trap_no);sigsegv_outp("Err Code= 0x"REGFORMAT, uc->uc_mcontext.error_code);sigsegv_outp("Old Mask= 0x"REGFORMAT, uc->uc_mcontext.oldmask);#endif}static void print_call_link(ucontext_t *uc) {int i = 0;void **frame_pointer = (void **)NULL;void *return_address = NULL;Dl_infodl_info = { 0 };#if (defined __i386__)frame_pointer = (void **)uc->uc_mcontext.gregs[REG_EBP];return_address = (void *)uc->uc_mcontext.gregs[REG_EIP];#elif (defined __x86_64__)frame_pointer = (void **)uc->uc_mcontext.gregs[REG_RBP];return_address = (void *)uc->uc_mcontext.gregs[REG_RIP];#elif (defined __arm__)/* sigcontext_t on ARM:        unsigned long trap_no;        unsigned long error_code;        unsigned long oldmask;        unsigned long arm_r0;        ...        unsigned long arm_r10;        unsigned long arm_fp;        unsigned long arm_ip;        unsigned long arm_sp;        unsigned long arm_lr;        unsigned long arm_pc;        unsigned long arm_cpsr;        unsigned long fault_address;*/frame_pointer = (void **)uc->uc_mcontext.arm_fp;return_address = (void *)uc->uc_mcontext.arm_pc;#endifsigsegv_outp("\nStack trace:");while (frame_pointer && return_address) {if (!dladdr(return_address, &dl_info))break;const char *sname = dl_info.dli_sname;#ifndef NO_CPP_DEMANGLEint status;char *tmp = __cxa_demangle(sname, NULL, 0, &status);if (status == 0 && tmp) {sname = tmp;}#endif/* No: return address <sym-name + offset> (filename) */sigsegv_outp("%02d: %p <%s + %lu> (%s)", ++i, return_address, sname, (unsigned long)return_address - (unsigned long)dl_info.dli_saddr, dl_info.dli_fname);#ifndef NO_CPP_DEMANGLEif (tmp)free(tmp);#endifif (dl_info.dli_sname && !strcmp(dl_info.dli_sname, "main")) {break;}#if (defined __x86_64__) || (defined __i386__)return_address = frame_pointer[1];frame_pointer = frame_pointer[0];#elif (defined __arm__)return_address = frame_pointer[-1];frame_pointer = (void **)frame_pointer[-3];#endif}sigsegv_outp("Stack trace end.");}static void sigsegv_handler(int signo, siginfo_t *info, void *context){if (context) {ucontext_t *uc = (ucontext_t *)context;   sigsegv_outp("Segmentation Fault!");    sigsegv_outp("info.si_signo = %d", signo);    sigsegv_outp("info.si_errno = %d", info->si_errno);    sigsegv_outp("info.si_code  = %d (%s)", info->si_code, (info->si_code == SEGV_MAPERR) ? "SEGV_MAPERR" : "SEGV_ACCERR");    sigsegv_outp("info.si_addr  = %p\n", info->si_addr);print_reg(uc);print_call_link(uc);}_exit(0);}#define SETSIG(sa, sig, fun, flags)     \        do {                            \            sa.sa_sigaction = fun;      \            sa.sa_flags = flags;        \            sigemptyset(&sa.sa_mask);   \            sigaction(sig, &sa, NULL);  \        } while(0)static void __attribute((constructor)) setup_sigsegv(void) {struct sigaction sa;SETSIG(sa, SIGSEGV, sigsegv_handler, SA_SIGINFO); #if 0memset(&sa, 0, sizeof(struct sigaction));sa.sa_sigaction = sigsegv_handler;sa.sa_flags = SA_SIGINFO;if (sigaction(SIGSEGV, &sa, NULL) < 0) {perror("sigaction: ");}#endif}#if 1void func3(void){char *p = (char *)0x12345678;*p = 10;}void func2(void){func3();}void func1(void){func2();}int main(int argc, const char *argv[]){func1();exit(EXIT_SUCCESS);}#endif

编译时请加上-rdynamic -ldl选项！

代码地址：https://github.com/astrotycoon/sigsegv/blob/master/sigsegv.c

2016-1-17 18:29:33补充知识如下：

今天无意中发现原来gcc