Hello Ian,
On 07/11/2018 07:26, Ian Caddy wrote:
Hi All,
We are migrating a product from RTEMS4.10 to RTEMS5, and I have come
up with a problem that we have not experienced previously.
We have some code that works before RTEMS mulit-tasking has been started.
yes, unfortunately some Newlib functions need now a valid executing
thread. These are functions which use errno or ctype.h methods for
example. If you use these functions before a executing thread exists,
then you end up in a NULL pointer access.
This code uses some string functions which are causing the system to
crash (bus error out), and I have worked it out to a call to:
_REENT
One example function is:
snprintf
using the newlib 3.0.0 the first few lines of the function are:
int
snprintf (char *__restrict str,
size_t size,
const char *__restrict fmt, ...)
{
int ret;
va_list ap;
FILE f;
struct _reent *ptr = _REENT;
The _REENT macro ends up calling:
cpukit/include/rtems/confdefs.h:2273 __getreent
which ends up returning the thread executing structure:
return _Thread_Get_executing()->libc_reent;
Since this is before multi-tasking, _Thread_Get_executing() returns
NULL, and this is not valid memory.
So, if I want to support this, do I need to configure:
#define CONFIGURE_DISABLE_NEWLIB_REENTRANCY
If I do this will it effect things later?
Yes, this is probably not what you want. The
CONFIGURE_DISABLE_NEWLIB_REENTRANCY disables the per-thread reentrancy
structure entirely. This is one of the configuration options which
should be used with special care.
Or should this be fixed to check whether multi-tasking is running
before checking the currently running thread, we do this in some of
our other code?
Code which runs before the idle threads are created should not use
complex Newlib functions. Unfortunately snprintf() is a complex Newlib
function. I think we need a low level replacement for snprintf() which
could be used during BSP initialization for example. This could be a
simple wrapper for _IO_Printf().
I had a similar issue here:
https://lists.rtems.org/pipermail/devel/2018-September/023013.html
--
Sebastian Huber, embedded brains GmbH
Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone : +49 89 189 47 41-16
Fax : +49 89 189 47 41-09
E-Mail : sebastian.hu...@embedded-brains.de
PGP : Public key available on request.
Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.
_______________________________________________
users mailing list
users@rtems.org
http://lists.rtems.org/mailman/listinfo/users
