Hi! On 10:55 Wed 25 May , Mulyadi Santosa wrote:
Hi...
On Tue, May 24, 2011 at 17:15, Ashok Babu <ashok3d@gmail.com> wrote:
So here my questions/doubts : 1) Is'nt it the kernel itself is self modifying code with lots of function pointers ?
AFAIK, yes there are many.. however, some of them, even in the form of pointer assignment, are rarely changing.
But if it is changing, for sure cache needs to be flushed/invalidated. This is especially true in SMP environment ( and don't forget memory barrier....)
This sounds like a very interesting arch to me. I would very much like to see any code which does cache flushing when changing a function pointer. In the mean time, let us assume that function pointers are data, not code. ;-) Then, you still have to think about concurrency, but not about cache flushing. What could cause trouble: - http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html - This requires an executeable stack - never tested whether kernel stacks are executable. No idea if something makes them executable. - Assembly code in arch/ , like the tracing framework. - ??? -Michi -- programing a layer 3+4 network protocol for mesh networks see http://michaelblizek.twilightparadox.com