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Jason Zaman
5c790678f1
The original P2ROUNDUP and P2ROUNDUP_TYPED macros contain -x which triggers PaX's integer overflow detection for unsigned integers. Replace the macros with an equivalent version that does not trigger the overflow. Axioms: A. (-(x)) === (~((x) - 1)) === (~(x) + 1) under two's complement. B. ~(x & y) === ((~(x)) | (~(y))) under De Morgan's law. C. ~(~x) === x under the law of excluded middle. Proof: 0. (-(-(x) & -(align))) original 1. (~(-(x) & -(align)) + 1) by A 2. (((~(-(x))) | (~(-(align)))) + 1) by B 3. (((~(~((x) - 1))) | (~(~((align) - 1)))) + 1) by A 4. (((((x) - 1)) | (((align) - 1))) + 1) by C Q.E.D. Signed-off-by: Jason Zaman <jason@perfinion.com> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Reviewed-by: Richard Yao <ryao@gentoo.org> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3949