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Preventing a tapscript from accessing user space.
- From: David Wilder <dwilder at us dot ibm dot com>
- To: systemtap at sources dot redhat dot com
- Date: Mon, 05 Feb 2007 16:38:57 -0800
- Subject: Preventing a tapscript from accessing user space.
What prevents a tapscript from attempting to access user space
directly? For example:
if $arg is a pointer to a struct in user space (presumably passed to
the kernel via some system call).
What prevents me from doing i=$arg->j in the tapscript.
Also when I looked at the code generated by stap I was hoping to see
deref() used but that is not what I found.
I could have missed something...
On i386 the above example works ok because we can just access the user
space, it works but it is not correct.
On s390 I can't do that I must use something like get_user(), but I
cant do that ether because get_user() calls might_sleep() and the probe
is running with interrupts off.
--
David Wilder
IBM Linux Technology Center
Beaverton, Oregon, USA
dwilder@us.ibm.com
(503)578-3789