Date: Wed, 19 Nov 2014 13:00:43 +0400 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: Ian Lepore <ian@FreeBSD.org> Cc: re <re@freebsd.org>, kyliel@microsoft.com, "weh@microsoft.com >> Wei Hu" <weh@microsoft.com>, John-Mark Gurney <jmg@funkthat.com>, huishao@microsoft.com, "Jun Fang \(Wicresoft\)" <v-jufang@microsoft.com>, "freebsd-arch@FreeBSD.org Arch" <freebsd-arch@freebsd.org>, d@delphij.net Subject: Re: kernel linker: Overriding a driver shipped with kernel via module? Message-ID: <20141119090043.GB68953@zxy.spb.ru> In-Reply-To: <1416359781.1147.74.camel@revolution.hippie.lan> References: <546A8191.3090208@delphij.net> <20141118124544.GA95731@zxy.spb.ru> <20141119001510.GM24601@funkthat.com> <20141119002718.GP9763@zxy.spb.ru> <20141119003632.GN24601@funkthat.com> <1416359781.1147.74.camel@revolution.hippie.lan>
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On Tue, Nov 18, 2014 at 06:16:21PM -0700, Ian Lepore wrote: > On Tue, 2014-11-18 at 16:36 -0800, John-Mark Gurney wrote: > > Slawa Olhovchenkov wrote this message on Wed, Nov 19, 2014 at 04:27 +0400: > > > On Tue, Nov 18, 2014 at 04:15:10PM -0800, John-Mark Gurney wrote: > > > > > > > Slawa Olhovchenkov wrote this message on Tue, Nov 18, 2014 at 16:45 +0400: > > > > > On Mon, Nov 17, 2014 at 03:15:29PM -0800, Xin Li wrote: > > > > > > > > > > > Right now one can declare version for a module by doing something like: > > > > > > > > > > > > MODULE_VERSION(module_name, module_version); > > > > > > > > > > > > Sometimes, it may be desirable for a vendor to release a new driver > > > > > > that overrides the driver shipped with the kernel itself. However, it > > > > > > seems that the MODULE_VERSION facility would just refuse the module > > > > > > when preloaded with kernel. > > > > > > > > > > > > Looking at some other vendor drivers, they are using a slightly > > > > > > different module name to overcome this limitation. Is that the only > > > > > > way to do it? > > > > > > > > > > I think now time to move to modulated kernel and load all drivers > > > > > currently present in GENERIC as modules (via loader.conf). > > > > > > > > This becomes slightly more difficult for storage drivers which must > > > > be loaded at boot time so the you can mount root from it... But yes, > > > > we are interested in methods to make it easier/more automatic for > > > > modules to be loaded to support the hardware that is present in a > > > > system... > > > > > > When loader can load kernel -- loader can load driver module, this is > > > not Linux (but yes, loader need plugable and stackable framework for > > > access FS -- currenly booting from ZFS over gstripe not allowed). > > > > That isn't the only issue.. another issue is identifing the correct > > kernel module(s) to load at boot... iirc, you cannot unload a kernel > > module loaded at boot time... > > > > You can do a kldunload on a module that was loaded by loader(8) and it > will be unlinked from the kernel in terms of symbol resolution, but the > memory cannot be freed. You can then load and unload the same module > again as much as you want, it just won't re-occupy the original address, > and the original memory is lost forever (but considering the size of > most modules, that's not such a big deal). Some modules can't be unloaded anyway: netgraph, for example.
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