exit.c: Truncate exit status to uint8_t
The valid range for an exit status is 0 - 255, so we need to truncate
the value passed to _exit().
I noticed this when a module was doing _exit(-1), and ended up calling
longjmp(.., 0xffffffff + 1)
which meant that setjmp() in spawn_load() returned 0. Obviously, we
wanted the setjmp() to return 256 (0xff + 1), because the code in
spawn_load() handles the return value like so,
ret_val = setjmp(module->u.x.process_exit);
if (ret_val)
ret_val--; /* Valid range is 0-255 */
else if (!module->main_func)
ret_val = -1;
else
exit((module->main_func)(argc, argv)); /* Actually run! */
There actually is code in spawn_load() to properly truncate 'ret_val',
but it is applied too late. The truncation needs to happen when we
pass the exit status to longjmp().
Suggested-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Matt Fleming <matt.fleming@linux.intel.com>