Re: using mprotect to write to .text

[David Daney <david.daney@cavium.com>]

On 10/10/2011 01:02 PM, Joe Buehler wrote:
> I intend to use mprotect in a running binary to allow it to modify its .text
> section.  The detailed behavior of mprotect for a multithreaded program on SMP
> hardware is not documented as far as I can tell.
It is well documented.  What is not well defined is what happens if you 
modify the code and then try to execute it.
> Can I depend on the LINUX mprotect call to take care of icache flushing,
> handling of hazards, etc.?
No, it does nothing of the sort.  You need cacheflush() for that.

>  I am using Octeon CN5650 on 2.6.21.7 and 2.6.27.7 if
> it matters.
It doesn't really matter.

What you need is something like:

#include <sys/cachectl.h>
.
.
.


cacheflush(location, size, ICACHE);
.
.
.

David Daney