[TAG] Talkback:123/jesslyn.html

[Robin Getz]

In http://linuxgazette.net/123/jesslyn.html Jesslyn Abdul Salam wrote:

>The Blackfin processor does not have an MMU, and does not provide any 
>memory protection for programs. This can be demonstrated with a simple program:

This is only true if you leave this feature turned off.

The Blackfin processor does include hardware memory protection, which the 
uClinux kernel supports - but since it effects performance, and most 
embedded developers only turn this on when doing development, and it is 
turned off by default.

http://docs.blackfin.uclinux.org/doku.php?id=operating_systems#introduction_to_uclinux

When you take:

int main ()
{
         int *i;

         i=0;
         *i=0xDEAD;
         <http://www.opengroup.org/onlinepubs/009695399/functions/printf.html>printf("%i 
: %x\n", i, *i);
}

and run it on the Blackfin/uClinux, you get:

root:~> uname -a
Linux blackfin 2.6.16.11.ADI-2006R1blackfin #4 Sat May 6 11:38:53 EDT 2006 
blackfin unknown
root:~> ./test
SIGSEGV

Which is pretty close to my desktop...
rgetz at test:~/test> uname -a
Linux test 2.6.8-24.18-smp #1 SMP Fri Aug 19 11:56:28 UTC 2005 i686 i686 
i386 GNU/Linux
rgetz at test:~/test> ./test
Segmentation fault


-Robin