Hi,
I made two rather small and (as I thought) straight forward changes to
gnumach to keep track of a tasks father task and to make this
information available. Now I know handing out task ports right and
left is not a wise thing to do, but I wanted to do it this way as a
first step.
Unfortunately it does not work as I expected it to work. Here is a
little test program to get the information:
~~~ snip ~~~
#define _GNU_SOURCE
#include <stdio.h>
#include <hurd.h>
#include <hurd/process.h>
#include <sys/types.h>
#include <unistd.h>
#include <error.h>
struct my_task_basic_info {
integer_t suspend_count; /* suspend count for task */
integer_t base_priority; /* base scheduling priority */
vm_size_t virtual_size; /* number of virtual pages */
vm_size_t resident_size; /* number of resident pages */
time_value_t user_time; /* total user run time for
terminated threads */
time_value_t system_time; /* total system run time for
terminated threads */
time_value_t creation_time; /* creation time stamp */
mach_port_t parent_task; /* parent of the task */
};
int
main ()
{
error_t err;
task_t t;
err = proc_pid2task (getproc (), getpid (), &t);
if (err)
error (1, err, "proc_pid2task");
task_t p;
err = proc_pid2task (getproc (), getppid (), &p);
if (err)
error (1, err, "proc_pid2task");
struct my_task_basic_info info = {};
mach_msg_type_number_t info_count;
err = task_info (t, TASK_BASIC_INFO, &info, &info_count);
if (err)
error (1, err, "task_info");
printf ("my task port is %i(pid %i) created by task %i; my parent task is
%i(pid %i)\n",
t, getpid (), info.parent_task, p, getppid ());
return p == info.parent_task? EXIT_SUCCESS: EXIT_FAILURE;
}
~~~ snap ~~~
On an unpatched gnumach kernel it prints
my task port is 1(pid 18) created by task 0; my parent task is 31(pid 6)
on a patched kernel it says something like
my task port is 1(pid 13) created by task -527895648; my parent task is
31(pid 1)
which (ignoring the signedness) looks a lot more like a pointer than
like a port. Richard suggested to hardcode a value to test whether the
value is actually handed across, and that works (i.e. a 3 came across
just fine).
Any thoughts?
To dig deeper into this I compiled in the kdb, but unfortunately it
does not translate from symbols to addresses and vice versa, that
makes debugging using it rather difficult. Is this a known problem or
am I holding it wrong?
I also tried to attach gdb to qemus gdb stub, and it has the same
issue, but at least I can set breakpoints using symbolic names.
The binary was compiled using -ggdb and was not stripped.
A little help?
Thanks,
Justus
