Re: [rtl] Shared memory, again...

[Fred Proctor <proctor@cme.nist.gov>]

Christian,

You wrote:

>         I'm using a RH 5.2 (2.0.36),RTL 1.1 on a P133 64MB Ram
> (Dell OptiPlex GXi) machine. I tried the following code , but it's not
> working:
...
> I tried this following the documentation of Frederick M. Proctor.
> The shared mem is initialized to 1M in the lilo.conf (append="mem=63m")).
> mmap always returns MAP_FAILED.

The permissions on /dev/mem need to allow RW access to you. The default
permissions are rw for root, read for members of the kmem group, and
nothing for anything else. If you haven't changed the permissions, you
need to be root to use /dev/mem.

I changed the permissions on /dev/mem to be RW for everyone, and setuid
root on /sbin/insmod and /sbin/rmmod. These are hideous security holes,
but they let normal users develop RT code without being root and
inadvertently damaging Linux. Anyone know of a better way?

--Fred
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