ptrace(PTRACE_ATTACH, ...) failing with error code one while attaching a thread from another thread

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C++

C

Linux

threads

kernel

I want to trace a specific thread from another thread.(Both are created from same parent)
1) Is it possible?


I wrote following code here; But from "thread_func_tracer" I got error no : 1, that is insufficient permission; i.e ptrace(PTRACE_ATTACH...) is failing with error code 1.

Can any one help?

  1 #include <stdio.h>
  2 #include <pthread.h>
  3 #include <sys/ptrace.h>
  4 #include <sys/types.h>
  5 #include <sys/wait.h>
  6 #include <unistd.h>
  7 #include <sys/signal.h>
  8 #include <syscall.h>
  9 #include <unistd.h>
 10 #include <sys/user.h>
 11 #include <stddef.h>
 12 #include <errno.h>
 13 
 14 void *thread_func_one(void *);
 15 void* thread_func_tracer(void *);
 16 
 17 int g_iVar_one = 0;
 18 
 19 typedef struct {
 20      pid_t childProcess;
 21      pid_t child_tid1;
 22 }parent_action_args;
 23 
 24 parent_action_args parent_arg_params = {0};
 25 
 26 int main(int argc, char* argv[])
 27 {
 28         pthread_t threadOne, thread_tracer;
 29         int iRet = -1, iRet2 = -1;
 30
31         iRet = pthread_create(&threadOne, NULL, thread_func_one, NULL);
 32         sleep(1);
 33         iRet2 = pthread_create(&thread_tracer, NULL, thread_func_tracer, NULL);
 34 
 35         pthread_join(threadOne, NULL);
 36         pthread_join(thread_tracer, NULL);
 37 
 38         return 0;
 39 }
 40 
 41 void *thread_func_one(void *pParam)
 42 {
 43     int iFlag = 0;
 44     parent_arg_params.childProcess = syscall (SYS_gettid);
 45     printf("<tid> = %d\n", parent_arg_params.childProcess);
 46     while(10 > iFlag)
 47     {
 48         g_iVar_one++;
 49         iFlag++;
 50         printf("g_iVar_one = %d\n", iFlag);
 51         sleep(1);
 52     }
 53 
 54 }
 55 
 56 void *thread_func_tracer(void *pParam)
 57 {
 58 
 59     printf("thread_func_tracer<tid> = %d\n", parent_arg_params.childProcess);
 60     if(ptrace(PTRACE_ATTACH, parent_arg_params.childProcess, NULL, NULL))
 61     {
 62          printf("MKH _ ATTACH-FAIL err =%d\n",errno);
 63     }
 64     wait(NULL);
 65 }