/ sigsegv.c / /* * This source file is used to print out a stack-trace when your program * segfaults. It is relatively reliable and spot-on accurate. * * This code is in the public domain. Use it as you see fit, some credit * would be appreciated, but is not a prerequisite for usage. Feedback * on it’s use would encourage further development and maintenance. * * Due to a bug in gcc-4.x.x you currently have to compile as C++ if you want * demangling to work. * * Please note that it’s been ported into my ULS library, thus the check for * HAS_ULSLIB and the use of the sigsegv_outp macro based on that define. * * Author: Jaco Kroon jaco@kroon.co.za * * Copyright (C) 2005 - 2010 Jaco Kroon/ #ifndef _GNU_SOURCE #define _GNU_SOURCE #endif
/* Bug in gcc prevents from using CPP_DEMANGLE in pure "C" */
#if !defined(__cplusplus) && !defined(NO_CPP_DEMANGLE)
#define NO_CPP_DEMANGLE
#endif
#include <memory.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <ucontext.h>
#include <dlfcn.h>
#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(REG_RIP)
# define SIGSEGV_STACK_IA64
# define REGFORMAT "%016lx"
#elif defined(REG_EIP)
# define SIGSEGV_STACK_X86
# define REGFORMAT "%08x"
#else
# define SIGSEGV_STACK_GENERIC
# define REGFORMAT "%x"
#endif
static void signal_segv(int signum, siginfo_t* info, void*ptr) {
static const char *si_codes[3] = {"", "SEGV_MAPERR", "SEGV_ACCERR"};
int i, f = 0;
ucontext_t *ucontext = (ucontext_t*)ptr;
Dl_info dlinfo;
void **bp = 0;
void *ip = 0;
sigsegv_outp("Segmentation Fault!");
sigsegv_outp("info.si_signo = %d", signum);
sigsegv_outp("info.si_errno = %d", info->si_errno);
sigsegv_outp("info.si_code = %d (%s)", info->si_code, si_codes[info->si_code]);
sigsegv_outp("info.si_addr = %p", info->si_addr);
for(i = 0; i < NGREG; i++)
sigsegv_outp("reg[%02d] = 0x" REGFORMAT, i, ucontext->uc_mcontext.gregs[i]);
#ifndef SIGSEGV_NOSTACK
#if defined(SIGSEGV_STACK_IA64) || defined(SIGSEGV_STACK_X86)
#if defined(SIGSEGV_STACK_IA64)
ip = (void*)ucontext->uc_mcontext.gregs[REG_RIP];
bp = (void**)ucontext->uc_mcontext.gregs[REG_RBP];
#elif defined(SIGSEGV_STACK_X86)
ip = (void*)ucontext->uc_mcontext.gregs[REG_EIP];
bp = (void**)ucontext->uc_mcontext.gregs[REG_EBP];
#endif
sigsegv_outp("Stack trace:");
while(bp && ip) {
if(!dladdr(ip, &dlinfo))
break;
const char *symname = dlinfo.dli_sname;
#ifndef NO_CPP_DEMANGLE
int status;
char * tmp = __cxa_demangle(symname, NULL, 0, &status);
if (status == 0 && tmp)
symname = tmp;
#endif
sigsegv_outp("% 2d: %p <%s+%lu> (%s)",
++f,
ip,
symname,
(unsigned long)ip - (unsigned long)dlinfo.dli_saddr,
dlinfo.dli_fname);
#ifndef NO_CPP_DEMANGLE
if (tmp)
free(tmp);
#endif
if(dlinfo.dli_sname && !strcmp(dlinfo.dli_sname, "main"))
break;
ip = bp[1];
bp = (void**)bp[0];
}
#else
sigsegv_outp("Stack trace (non-dedicated):");
sz = backtrace(bt, 20);
strings = backtrace_symbols(bt, sz);
for(i = 0; i < sz; ++i)
sigsegv_outp("%s", strings[i]);
#endif
sigsegv_outp("End of stack trace.");
#else
sigsegv_outp("Not printing stack strace.");
#endif
_exit (-1);
}
static void __attribute__((constructor)) setup_sigsegv() {
struct sigaction action;
memset(&action, 0, sizeof(action));
action.sa_sigaction = signal_segv;
action.sa_flags = SA_SIGINFO;
if(sigaction(SIGSEGV, &action, NULL) < 0)
perror("sigaction");
}
$ g++ -fPIC -shared -o libsigsegv.so -ldl sigsegv
$ export LD_PRELOAD=/path/to/libsigsegv.so
我在一个LUG上找到了此代码。无法进入页面将URL指向此处，因此粘贴了整个代码。发生SIGSEGV时，此代码将打印一条小的堆栈跟踪。不知道是否还有其他不使用ucontext_t的方式。
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