BTW, let us delved deeper and learn more. As Srinivas has questioned on mm_struct, the answer is therefore pertaining to per process. We may also also similarly question about the kernel - stack space starting from where, its size etc. I found some expert answer: http://kerneltrap.org/node/5416 Not sure how relevant it is to 2.6, but I guessed it should be the same: (correct me if wrong, as I may be entirely wrong - just making a guess) The kernel and the user processes are sharing the same virtual memory space, and therefore same pagetable for memory mapping, and therefore whenever any of the kernel module get executed, it uses the same stack space as the process context. Access control to the memory (eg, userspace cannot see kernelspace memory) is via DPL labelling of the memory: http://en.wikipedia.org/wiki/Privilege_level for intel x86 chip. Related: http://kerneltrap.org/node/6399 http://en.wikipedia.org/wiki/Physical_address - -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ