[dtrace-discuss] userland data

[Ashok Nair]

Hi,

  Have a question about  one of the example  I came across:

syscall::open*:entry
{
  self->path = arg0;
}

syscall::open*:return
/self->path != NULL && (int)arg0 == -1 && errno == EACCES/
{
printf("UID %d perm denied to open %s\n", uid, copyinstr(self->path));
self->path =0;
}

the reasoning for using copyinstr is to copy userland data to kernel space, but the data is referenced in the predicate without using copyinstr (or is that check for some pointer to the data)?

How to generally know if some piece of data lies in userland or not? Is the understanding that data for pointers to all system calls lies in userland space?

Thanks
Ashok
 
 
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