On Mon, Sep 09, 2002 at 03:09:51PM -0600, Joseph A. Knapka wrote: > > > [kernel stack protection using redpages] > > Iterate over $n processes .. where $n is disturbingly large on some > > systems. > Hmm... Why not just look at the stack for "current"? It isn't exactly that easy -- adding a red page at the end of the stack space would need to be implemented in one of two fashions: either allocate a new redpage in the kernel address space on context switch or allocate a redpage at task creation time. The first method, allocating a redpage on every context switch, is likely to be hideously expensive, though it would be more conservative with memory usage. The second method, allocating a redpage at task creation time, is cheaper, but it would throw away a whole page of storage for every task on the system. On my piddly desktop, that would be throwing away 512k of memory. (That is a _lot_ of dentries and inodes! :) Some people are building machines designed to handle 10000 tasks, and more, without problems.. asking those people to dedicate 40 megabytes to empty pages isn't going to go over well. :) -- http://immunix.org/
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