捕捉訊號SIGSEGV並回溯棧幀
阿新 • • 發佈：2019-01-06
引出問題
在嵌入式應用程式開發過程中，除錯一直是個老大難問題 -- 由於環境的限制，當程式發生段錯誤時不能很好的定位到底是哪裡出現了錯誤，如果在程式發生段錯誤時能夠清晰明瞭地看到程式的棧幀鏈，那無疑是雪中送炭。本文就捕捉訊號SIGSEGV並在該訊號的處理函式中打印出函式棧幀鏈來幫助我們除錯程式。
本文的程式適合ARM和X86平臺。
回溯棧幀原理
理解函式棧幀的佈局後，那麼自然明白回溯棧幀的原理了，這裡不多解釋了，直接上圖（來自網路）：
x86函式棧幀結構
ARM函式棧幀結構
程式碼sigsegv.c
[cpp] view plain copy print?
- #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>
- /* 純C環境下，不定義巨集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"
- #endif
- staticvoid 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
- }
- staticvoid print_call_link(ucontext_t *uc)
- {
- int i = 0;
- void **frame_pointer = (void **)NULL;
- void *return_address = NULL;
- Dl_info dl_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;
- #endif
- sigsegv_outp("\nStack trace:");
- while (frame_pointer && return_address) {
- if (!dladdr(return_address, &dl_info)) break;
- constchar *sname = dl_info.dli_sname;
- #ifndef NO_CPP_DEMANGLE
- int 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_DEMANGLE
- if (tmp) free(tmp);
- #endif
- if (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.");
- }
- staticvoid 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)
- staticvoid __attribute((constructor)) setup_sigsegv(void)
- {
- struct sigaction sa;
- SETSIG(sa, SIGSEGV, sigsegv_handler, SA_SIGINFO);
- #if 0
- memset(&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 1
- void func3(void)
- {
- char *p = (char *)0x12345678;
- *p = 10;
- }
- void func2(void)
- {
- func3();
- }
- void func1(void)
- {
- func2();
- }
- int main(int argc, constchar *argv[])
- {
- func1();
- exit(EXIT_SUCCESS);
- }
- #endif
2016-1-17 18:29:33補充知識如下：
今天無意中發現原來gcc
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