possible regression of ptrace on 2.6.26-rc1

[wenji huang]

Hi,

When I tried the test case (ptrace-syscall-ret) on 2.6.26-rc1 kernel, 
found it always fails, but could pass on previous ones.

Here is the result (both in x86 and x86_64 box):

[wjhuang@10-182-121-27 single-test]$ ./ptrace-syscall-ret
./ptrace-syscall-ret: PTRACE_CONT, pid 17315, retvalue -1: No such process

In the case, a child is created and kept in syscall loop. The parent 
will trace the syscall and kill the child at last. It seems the child
is early exited, but should stay in infinite loop. Is this my 
misunderstanding or actual regression of kernel?

The test case is attached to the mail.

Thanks,
Wenji

#include <signal.h>
#include <sys/wait.h>
#include <sys/ptrace.h>
#include <sys/user.h>
#include <unistd.h>
#include <sched.h>
#include <assert.h>
#include <asm/unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <error.h>
#include <errno.h>
	      
#if defined __x86_64__ || defined __i386__
#define LOOP 10

static pid_t child;      

static void
cleanup (void)
{
  if (child != 0)
    kill (child, SIGKILL);
}

static void
handler_fail (int signo)
{
  cleanup ();

  signal (SIGABRT, SIG_DFL);
  assert (0);
}


int main(int argc, char **argv) {
     int status, j;
     long l;	      
     pid_t pid;

     setbuf (stdout, NULL);
     atexit (cleanup);
     signal (SIGABRT, handler_fail);

     child = fork();
     switch (child) 
     {
	case -1:
		assert(0);
	case 0:  
	  {  l = ptrace(PTRACE_TRACEME, 0, 0, 0);
	     assert(l==0);
	     raise(SIGSTOP);
	     while (1) { 
		l = access(".",R_OK);
		assert(l==0);
	     }	
	     assert(0); //not reached
	   } //end child
	default:
	    break;
         }
    	
 	pid = waitpid(child, &status, 0); 
	assert(pid==child);

        assert(WIFSTOPPED(status));
        assert(WSTOPSIG(status) == SIGSTOP);

	l = ptrace(PTRACE_SYSCALL,child, 0, 0);
	assert(l==0);

       	j = 0;
	while (j < LOOP){

	      pid = waitpid(child, &status, 0);
	      assert(child==pid);
		
	      assert(WIFSTOPPED(status));
	      assert(WSTOPSIG(status) == SIGTRAP);

       	      l = ptrace(PTRACE_SYSCALL, child, 0, 0);
	      assert(l==0);
	      j++;
         } //end loop

	l = ptrace(PTRACE_CONT, child, 0, SIGKILL);
	//if the following statement, always successful
	//l = ptrace(PTRACE_KILL, child, 0,0); 
	if (l < 0) {
   	    error (0, errno,"PTRACE_CONT, pid %ld, retvalue %ld",(long)child,l);
  	    return 1;
	}	
	else
	    assert(l==0);

	pid = waitpid(child, &status, 0);
	assert(child==pid);

	if (WIFEXITED(status) && WTERMSIG(status)!=SIGKILL) 
	      return 1;
	return 0;
} //end main
	      
#else
int main(int argc, char **argv) {
	return 77;
}
#endif