On Mon, 1 Nov 2004 09:00:42 -0500 (EST), Rik van Riel <riel@xxxxxxxxxxx> wrote: > On Mon, 1 Nov 2004, Vishal Soni wrote: > > 3. As we know that the user space process can't access kernel address space and when shmat system call is > > used the shared memory is mapped to the Process's Virtual Address space, > > Now the question is from where in the memory does shared memory come from... i mean does it come from > > User Space or Kernel Space.........or from process's Data Segment.... ?????? > > Shared memory areas are virtual memory. Kernel address space > is virtual memory. > > It is common for the same page of physical memory to be mapped > both by userspace processes and by the kernel. Rik, I think he was more asking ``where does the memory come from?'' and, excepting the points you mention above, it's most important to displace any notions that userspace is somehow different from a process' data segment (from the mail above) - userspace only deals in one kind of memory, virtual memory, but it's mapped in different vmas. Cheers, Jon. -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
