pthread中如何追蹤stack over flow

通常在程序掛掉的時候我們會catch 他們掛掉的signal，然后在signal中打印出當時的一個stack，來方便問題調查,?但是在stack overflow的情況發生時，會沒有拿到stack。signal的stack也是建立在thread的調用棧上的，在overflow的情況下，stack沒有足夠的空間來執行signal處理函數，signal處理函數就會被忽略。

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示例代碼：
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 頭文件

#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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說明：
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");} }

這邊由外部傳進來的數組作為signal 處理函數執行用的stack
注冊signal函數：
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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");} }

注冊了signal
SIGSEGV
SIGBUS
SIGILL
另外sigaction flag添加了SA_ONSTACK，確保當signal發生的時候，
signal處理函數會將sig atl stack作為函數frame

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主函數：

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; }

執行前添加下signal的altstak，這里使用棧上的數組來作為signal處理函數的函數棧，可以通過malloc或者mmap分配.

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線程的主函數

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

執行前再添加下sig alt stack
注意：sig alt stack時每個線程自己單獨的屬性，所以每個線程都需要添加自己的sig alt stack

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posted on 2014-06-22 17:52 secularbird 閱讀(...) 評論(...) 編輯 收藏

轉載于:https://www.cnblogs.com/zelos/p/3802792.html

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