A program can only be traced by one process, so if it is being traced (before anyone else) by itself, it will not allow any other tracer to trace it (lots of workarounds here...). Additionally, when a trace is initiated a SIGSTOP is sent. Try installing a handler for SIGSTOP. It worked for me but I don't know why.

/* bliako modified https://reverseengineering.stackexchange.com/a/1931
   for https://perlmonks.org/?node_id=3333;parent=1229102
   KILL it with SIGKILL (kill -9)
   29/01/2019
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ptrace.h>
#include <unistd.h>
#include <signal.h>

void intHandler(int sig) { printf("got signal %d\n", sig); }

int main(void){
    printf("my pid: %d\n", getpid());

    char *e;
    if( (e=getenv("TRACEME")) != NULL && (strcmp(e,"0")==0) ){
        printf("Will not be traced...\n");
        signal(SIGSTOP, intHandler);
        if (ptrace(PTRACE_TRACEME, 0, 1, 0) == -1) 
        {
            printf("don't trace me !!\n");
            return 1;
        }
    }
    // normal execution
    for(int i=0;;i++){
        printf("i=%d\n", i);
        sleep(1);
    }
    return 0;
}

[download]
gcc tracee.c -o tracee && TRACEME=0 tracee

strace -p <PID-from-traceed>

strace: attach: ptrace(PTRACE_SEIZE, 11091): Operation not permitted

[download]

while tracee continues counting on

or

TRACEME=1 tracee

strace -p <PID-from-tracee>

[download]

bw, bliako

ps. Please share your findings. Most answers are in the manual and let's keep to Perl less the reaper traces us. brrrrr

In reply to Re^3: Embed perl problem by bliako
in thread Embed perl problem by Noves Castro

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