Date: Tue, 16 Nov 2010 02:48:17 +0100 From: Luigi Rizzo <rizzo@iet.unipi.it> To: Ivan Voras <ivoras@freebsd.org> Cc: svn-src-head@freebsd.org, Luigi Rizzo <luigi@freebsd.org>, src-committers@freebsd.org, svn-src-all@freebsd.org Subject: Re: svn commit: r215178 - in head: lib/libc/sys sys/kern sys/sys Message-ID: <20101116014817.GA25713@onelab2.iet.unipi.it> In-Reply-To: <AANLkTimbF45rHrP9FXc0Fr7j%2Bq_NYa8haXpjYSWWiYc-@mail.gmail.com> References: <201011121302.oACD2Qjt009385@svn.freebsd.org> <AANLkTinpfy-V79k0mgezJV6QpuUWMG3uOZ0hTY2tN4Rf@mail.gmail.com> <20101115171016.GB20524@onelab2.iet.unipi.it> <AANLkTimbF45rHrP9FXc0Fr7j%2Bq_NYa8haXpjYSWWiYc-@mail.gmail.com>
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On Tue, Nov 16, 2010 at 01:33:53AM +0100, Ivan Voras wrote: > On 15 November 2010 18:10, Luigi Rizzo <rizzo@iet.unipi.it> wrote: > > > 2. [generic] passing pointers between userland and kernel > > requires remapping the pointer when going up or down. > > As the mapping would be application specific, i don't > > see much use in allowing room for a pointer without kernel code > > to map userland <-> kernel pointers. > > I'm not thinking of passing a *working* pointer into the kernel but > used as a cookie, similar to how it's used in kqueue: the intention > being the application can send and get a pointer which means something > to the application, not something usable to the kernel. oh, but then you are thinking of something completely different. The SO_USER_COOKIE is never returned to the application; it is only passed to another kernel subsystem, so it must be significant there, not for the application. cheers luigi
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