Apple

Hey guys,

I'm trying to get started with basic ptrace functionality with the following:

#include <sys/types.h>
#include <sys/ptrace.h>
#include <sys/wait.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
int main(int argc, char **argv)
{
    int pid, status, ret;

    if((pid = fork()) == 0)
    {
        ptrace(PT_TRACE_ME,0,0,0);
        execl(argv[1],argv[1],0);
        printf("exec failed\n");
    }
    else{
        wait(&status);
        if(WIFSTOPPED(status))
            printf("child has stopped. child pid: %d\n", pid);
        errno = 0;
        ret = ptrace(PT_CONTINUE, pid, (caddr_t)1, 0);
        printf("ret: %d\n", ret);
        printf("errno: %s\n", strerror(errno));
    }

}

>From my basic understanding, what the above should do is fork a child process which will stop at exec and cause the parent-tracing process to exit wait(). The parent process should then have the child process continue execution normally by calling ptrace() with PT_CONTINUE.

When I run the code, The child process is created, however, ptrace() with PT_CONTINUE seems to fail as the child process does not continue normal execution. ptrace's return value is 0 and errno is "Unknown error: 0".

Running output:

aronzvis-macbook:ptrace_test aronzvi$ ./ptrace ../voidinc
child has stopped. child pid: 37959
ret: 0
errno: Unknown error: 0

I'm running OS X 10.5.7 and building the code with the 10.5 SDK.

Your help is much appreciated,

Aron-Zvi

References:
	>ptrace PT_CONTINUE (From: Aron-Zvi <email@hidden>)