Jan Kiszka wrote:
> [Let's discuss this without bothering users :)]
> Philippe Gerum wrote:
> > Author: rpm
> > Date: Sun Nov 4 18:18:39 2007
> > New Revision: 3147
> > URL: http://svn.gna.org/viewcvs/xenomai?rev=3147&view=rev
> > Log:
> > Make __xn_access_ok() return false for addresses lower than the natural
> > page size.
> > Modified:
> > trunk/ChangeLog
> > trunk/include/asm-x86/syscall_32.h
> > trunk/include/asm-x86/syscall_64.h
> Could it be that you meant "PAGE_SIZE" instead of "PAGE_OFFSET"? Because
> the current version is "slightly" broken, tagging any address in user
> land as invalid.
> And if this test was meant to catch NULL page accesses early, is the
> intention to cope with all those current i-pipe patches that do not yet
> include the discussed domain switch on non-root faults? If yes, this
> test would be a workaround for legacy code and should not become default
> (pure overhead for later versions).
We can reduce the overhead of the two tests by testing
(unsigned long) (addr - PAGE_SIZE) < (PAGE_OFFSET - PAGE_SIZE)
> Last question: We need this for the other archs as well, don't we?
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