On Oct 16, 2006, at 15:19:03, mfbaustx wrote:
So you're absolutely obligated to DO the copy at the time the
kernel is executing on behalf of that process. Once your process/
thread is context swapped, you've lost the [correct] information on
the address mapping.
Yes, this is correct.
So, IF you MUST copy_from/to_user when in the context of the
process, AND IF you have no virtual memory/swapping, THEN must it
not be true that you can ALWAYS dereferences your user space pointers?
I'm not sure I entirely understand what you're asking here; perhaps
you could rephrase or explain what you're trying to do? From what I
can pick up from your description; you may be missing that program
text pages and memory-mapped files may be "swapped-out" even
*without* a swap device. As an example, when I first start /bin/bash
(ignoring readahead for the moment), very little of the binary and
shared libraries are actually in memory (the rest is left on disk).
When I use data or call a function that hasn't been loaded from disk
yet, a major fault occurs, the kernel loads data from the bash
executable file or a shared library, and then maps it into the
process address space.
Cheers,
Kyle Moffett
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