Messages in this thread Patch in this message | | | Date | Mon, 29 Sep 2003 12:06:30 +0300 | From | Muli Ben-Yehuda <> | Subject | [PATCH] document optimizing macro for translating PROT_ to VM_ bits |
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In continuation to the thread at http://marc.theaimsgroup.com/?l=linux-kernel&m=3D106270456516176&w=2 wrt translating PROT_(censored) bits to VM_(censored) bits, here's a small comment only patch to document the optimizing macro Jamie's patch used. Against 2.6.0-t6, but should apply to anything recent. Compiles.
Cheers, Muli
--- linux-2.5/include/linux/mman.h Sun Sep 7 10:05:18 2003 +++ optimizing-macro-2.6.0-t6/include/linux/mman.h Mon Sep 29 11:53:12 2003 @@ -28,7 +28,10 @@ vm_acct_memory(-pages); } -/* Optimisation macro. */ +/* Optimisation macro, used to be defined as: */ +/* ((bit1 == bit2) ? (x & bit1) : (x & bit1) ? bit2 : 0) */ +/* but this version is faster */ +/* "check if bit1 is on in 'x'. If it is, return bit2" */ #define _calc_vm_trans(x,bit1,bit2) \ ((bit1) <= (bit2) ? ((x) & (bit1)) * ((bit2) / (bit1)) \ : ((x) & (bit1)) / ((bit1) / (bit2))) -- Muli Ben-Yehuda http://www.mulix.org
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