pthread中如何追踪stack over flow

pthread中如何追踪stack over flow

通常在程序挂掉的时候我们会catch 他们挂掉的signal，然后在signal中打印出当时的一个stack，来方便问题调查, 但是在stack overflow的情况发生时，会没有拿到stack。signal的stack也是建立在thread的调用栈上的，在overflow的情况下，stack没有足够的空间来执行signal处理函数，signal处理函数就会被忽略。

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示例代码：
main 主程序

#include <signal.h> #include <pthread.h> #include <stdio.h> #include <string.h> #include <stdlib.h> #include <sys/types.h> #include "mybacktrace.h"void recursiondeath() {char buffer[1024];recursiondeath();memset(buffer, 0xeb, sizeof(buffer));printf("%d", buffer[0]); }void* threadloop(void* args) {// using sginal stackchar altstack[SIGSTKSZ];addsignalstack(altstack, SIGSTKSZ);recursiondeath();return NULL; }int main(int argc, char const *argv[]) {char altstack[SIGSTKSZ];registersignal();addsignalstack(altstack, SIGSTKSZ);pthread_t t;pthread_create(&t, NULL, threadloop, NULL);pthread_join(t, NULL);return 0; }

mybacktrace.h 头文件

#include <execinfo.h> #include <signal.h> #include <assert.h>void signalhandler(int sig) {printf("signal revived [%d]\n", sig);// get the back traceenum {MAX_STACK = 32,};void *stack[MAX_STACK];int size = backtrace(stack, MAX_STACK);if(size == 0) {printf("fail to get backtrace\n");} char** strs = backtrace_symbols(stack, size);int i = 0;for (i = 0; i < size; ++i) {printf("%s\n", strs[i]);}free(strs);signal(sig, SIG_DFL); }void addsignalstack(char *stack, int size) {assert(stack!=NULL);// using sginal stack stack_t sigstack;sigstack.ss_sp = stack;sigstack.ss_size = SIGSTKSZ;sigstack.ss_flags = 0;if (sigaltstack(&sigstack, 0) < 0) {perror("sig stack setting failed");} }void registersignal() {struct sigaction act;act.sa_handler = signalhandler;act.sa_flags = SA_ONSTACK|SA_RESTART;int ret = sigaction(SIGSEGV, &act, NULL);if (ret < 0) {perror("sigaction failed\n");}ret = sigaction(SIGBUS, &act, NULL);if (ret < 0) {perror("sigaction failed\n");}ret = sigaction(SIGILL, &act, NULL);if (ret < 0) {perror("sigaction failed\n");}}

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说明：
添加signal alt stack

void addsignalstack(char *stack, int size) {assert(stack!=NULL);// using sginal stack stack_t sigstack;sigstack.ss_sp = stack;sigstack.ss_size = SIGSTKSZ;sigstack.ss_flags = 0;if (sigaltstack(&sigstack, 0) < 0) {perror("sig stack setting failed");} }

这边由外部传进来的数组作为signal 处理函数执行用的stack
注册signal函数：
```

void registersignal() {struct sigaction act;act.sa_handler = signalhandler;act.sa_flags = SA_ONSTACK|SA_RESTART;int ret = sigaction(SIGSEGV, &act, NULL);if (ret < 0) {perror("sigaction failed\n");}ret = sigaction(SIGBUS, &act, NULL);if (ret < 0) {perror("sigaction failed\n");}ret = sigaction(SIGILL, &act, NULL);if (ret < 0) {perror("sigaction failed\n");} }

注册了signal
SIGSEGV
SIGBUS
SIGILL
另外sigaction flag添加了SA_ONSTACK，确保当signal发生的时候，
signal处理函数会将sig atl stack作为函数frame

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主函数：

int main(int argc, char const *argv[]) {char altstack[SIGSTKSZ];registersignal();addsignalstack(altstack, SIGSTKSZ);pthread_t t;pthread_create(&t, NULL, threadloop, NULL);pthread_join(t, NULL);return 0; }

执行前添加下signal的altstak，这里使用栈上的数组来作为signal处理函数的函数栈，可以通过malloc或者mmap分配.

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线程的主函数

void* threadloop(void* args) {// using sginal stackchar altstack[SIGSTKSZ];addsignalstack(altstack, SIGSTKSZ);recursiondeath();return NULL; }

执行前再添加下sig alt stack
注意：sig alt stack时每个线程自己单独的属性，所以每个线程都需要添加自己的sig alt stack

 

 

posted on 2014-06-22 17:52 secularbird 阅读(...) 评论(...) 编辑 收藏

转载于:https://www.cnblogs.com/zelos/p/3802792.html

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