April 2004 - Darwin-kernel - lists.apple.com

Re: Creating a mountable pseudo device
by Matthijs van Duin 05 Apr '04

05 Apr '04

On Mon, Apr 05, 2004 at 12:03:28PM +0100, Tim Hewett wrote: I am trying to find out how to create a device which can be mounted and ejected in the same kind of way as a disk image. I.e. a disk image isn't a real physical device as such, but it can be mounted and presumably there is a process which acts as a translator between the contents of the disk image and the kernel's wish to reference it as a filesystem. Also would it be necessary to write this, or part of it, in kernel space, or is it possible to do it entirely in user space? How about making a custom WebDAV server that "hosts" the virtual filesystem, and then just use mount_webdav ? Just a random idea.. at least it would work entirely in user space. - xmath -- Matthijs van Duin -- May the Forth be with you! _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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Creating a mountable pseudo device
by Tim Hewett 05 Apr '04

05 Apr '04

Hello, I am trying to find out how to create a device which can be mounted and ejected in the same kind of way as a disk image. I.e. a disk image isn't a real physical device as such, but it can be mounted and presumably there is a process which acts as a translator between the contents of the disk image and the kernel's wish to reference it as a filesystem. I would like to do something very similar but cannot find any documentation describing an API or any examples demonstrating this. Any suggestions on where to find this info would be much appreciated. Also would it be necessary to write this, or part of it, in kernel space, or is it possible to do it entirely in user space? Regards, Tim. _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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VFS componentname modification
by Brian Bergstrand 02 Apr '04

02 Apr '04

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 I have a VFS plug-in that does not allow certain characters in filenames. The biggest annoyance seems to be custom directory icons, which are stored in the parent directory as a file named "Icon\n" -- yes that's an embedded newline. So I had this novel idea to translate all illegal characters into '_' (special case the "Icon\n" case so they still work). Problem is, that in order for the kernel to know about the name change, I'm going to have to modify the incoming componentname.cn_nameptr field. My question is, is this safe to do? I won't be changing the length of the name, but if the name has been cached the hash will be invalid. So am I nuts, or is this possible? Here's the current list of chars that would be translated to '_': "\n\r\\:*?\"><b+B)B.b"" Thanks. Brian Bergstrand <http://www.bergstrand.org/brian/>, AIM: triryche206 PGP Key: <http://www.bergstrand.org/brian/misc/public_key.txt> From there to here, from here to there, funny things are everywhere. - Dr. Seuss As of 03:05:38 PM, iTunes is playing "Intro" from "14 Shades Of Grey" by "Staind" -----BEGIN PGP SIGNATURE----- Version: PGP 8.0.3 iQA/AwUBQG3JmXnR2Fu2x7aiEQLIKQCg6EoamTc62uFLcCAM8lj6sHfobLIAoPMz fxNr404crk5hs9d4NHk2yxjb =TGwn -----END PGP SIGNATURE----- _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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Re: terminating a socket read from inside the kernel
by Rob McKeever 02 Apr '04

02 Apr '04

Justin, That's exactly what's going on... and I do have a fair bit of synchronization logic in place to handle the thread sync issues. The problem is that the sorwakeup (same might be true for the matching sowwakeup) call doesn't reliably exit the state machine for the socket recv call. ...Part of my problem here has been tracing the calls internally to try to figure out what goes where, given the dynamic nature of the TCP stack, but I now have sorted out. Just trying to figure out the best/most reliable way to abort the state machine for that socket without corrupting too much of it's state in the process... -Rob On 1-Apr-04, at 10:00 PM, Justin Walker wrote: > On Apr 1, 2004, at 10:44, Rob McKeever wrote: > >> Hi Justin, >> >> By abort I mean abandon the pending read or recv call on the socket >> without closing the connection. The receive runs on a separate thread >> and I can send that thread a signal via pthread_kill() to kick it back >> out of the system call. What I was trying to accomplish via the >> sorwakeup() call was to roust the kernel thread out of the read/recv >> call in much the same fashion - I'm probably missing some small but >> important bit about setting the state of the socket state machine, >> etc. > > I'm not entirely sure I understand what you are doing, so forgive me if > this sounds overly simplistic. > > You have several (>= 1) threads running in the kernel, one of which is > awaiting incoming bits. You want to tell that thread to knock it off > and get on with other work. > > The way this is normally done is with something like a semaphore. The > simplest approach is to have a "KnockItOff" variable that is normally > zero. Your read thread checks it before it goes off in a read, to see > whether the read should be avoided. Another mechanism can set this to > 1, and then call sorwakeup(). On awakening, your original thread goes > through its normal "getting ready to read" logic, discovers that a > higher authority wants it to belay that, and does as requested. > > In a kernel environment, you are running in a preemptive threading > world, of course, so you will need some additional baggage to assure > that the "check variable; sleep" sequence is atomic (so that the > variable doesn't get set and the wakeup sent prior to the sleep > occuring). > > Under the current regime, given that you are in NetworkWorld, the > Network Funnel is your friend. The thread that sets the bit will have > to hold the funnel while it sets. Your read thread will automatically > have the thread (when it runs) since it is readING a socket. > > In the TomorrowLand, when the KPI and other changes arise, you will > need to revisit the mechanism you use for synchronization. > > Hope that helps. Let us know if I missed the point. > > Regards, > > Justin > > -- > Justin C. Walker, Curmudgeon-At-Large * > Institute for General Semantics | It's not whether you win or > lose... > | It's whether *I* win or > lose. > *-------------------------------------- > *-------------------------------* > > > --__--__-- > > _______________________________________________ > darwin-kernel mailing list | darwin-kernel(a)lists.apple.com > Help/Unsubscribe/Archives: > http://www.lists.apple.com/mailman/listinfo/darwin-kernel > Do not post admin requests to the list. They will be ignored. > > > > End of darwin-kernel Digest [demime 0.98b removed an attachment of type application/pkcs7-signature which had a name of smime.p7s] _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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Re: terminating a socket read from inside the kernel
by Justin Walker 01 Apr '04

01 Apr '04

On Apr 1, 2004, at 10:44, Rob McKeever wrote: Hi Justin, By abort I mean abandon the pending read or recv call on the socket without closing the connection. The receive runs on a separate thread and I can send that thread a signal via pthread_kill() to kick it back out of the system call. What I was trying to accomplish via the sorwakeup() call was to roust the kernel thread out of the read/recv call in much the same fashion - I'm probably missing some small but important bit about setting the state of the socket state machine, etc. I'm not entirely sure I understand what you are doing, so forgive me if this sounds overly simplistic. You have several (>= 1) threads running in the kernel, one of which is awaiting incoming bits. You want to tell that thread to knock it off and get on with other work. The way this is normally done is with something like a semaphore. The simplest approach is to have a "KnockItOff" variable that is normally zero. Your read thread checks it before it goes off in a read, to see whether the read should be avoided. Another mechanism can set this to 1, and then call sorwakeup(). On awakening, your original thread goes through its normal "getting ready to read" logic, discovers that a higher authority wants it to belay that, and does as requested. In a kernel environment, you are running in a preemptive threading world, of course, so you will need some additional baggage to assure that the "check variable; sleep" sequence is atomic (so that the variable doesn't get set and the wakeup sent prior to the sleep occuring). Under the current regime, given that you are in NetworkWorld, the Network Funnel is your friend. The thread that sets the bit will have to hold the funnel while it sets. Your read thread will automatically have the thread (when it runs) since it is readING a socket. In the TomorrowLand, when the KPI and other changes arise, you will need to revisit the mechanism you use for synchronization. Hope that helps. Let us know if I missed the point. Regards, Justin -- Justin C. Walker, Curmudgeon-At-Large * Institute for General Semantics | It's not whether you win or lose... | It's whether *I* win or lose. *--------------------------------------*-------------------------------* _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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Re: terminating a socket read from inside the kernel
by Rob McKeever 01 Apr '04

01 Apr '04

Hi Justin, By abort I mean abandon the pending read or recv call on the socket without closing the connection. The receive runs on a separate thread and I can send that thread a signal via pthread_kill() to kick it back out of the system call. What I was trying to accomplish via the sorwakeup() call was to roust the kernel thread out of the read/recv call in much the same fashion - I'm probably missing some small but important bit about setting the state of the socket state machine, etc. Ideas? -Rob On 1-Apr-04, at 8:36 AM, Justin Walker wrote: > > On Mar 31, 2004, at 21:26, Rob McKeever wrote: > >> Hi, >> >> I'm stumped with a problem... >> >> I've got a BSD socket connection from inside a kext on another thread >> and I'm trying to find a way to cause it to abort without using a >> timeout or closing the connection. From userland, I've done the same >> thing by using a signal to abort the syscall, but haven't been able to >> figure out how to do the same thing from kernelspace. >> >> I've tried issuing sorwakeup() on my socket, but it seems to have no >> effect. I've tried a few other bit too, but this is the one that >> seemed to make the most sense. Anyone have any ideas? > > What do you mean by "abort"? If you do this in user mode, you kill > the process, causing the kernel to shut down (close) all open file > descriptors. 'sorwakeup' just wakes up those processes waiting for > the receive side of the socket to get data. > > What are you trying to achieve? > > Regards, > > Justin > > -- > Justin C. Walker, Curmudgeon-At-Large * > Institute for General Semantics | "Weaseling out of things is > what > | separates us from the > animals. > | Well, except the weasel." > | - Homer J Simpson > *-------------------------------------- > *-------------------------------* [demime 0.98b removed an attachment of type application/pkcs7-signature which had a name of smime.p7s] _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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Re: terminating a socket read from inside the kernel
by Justin Walker 01 Apr '04

01 Apr '04

On Mar 31, 2004, at 21:26, Rob McKeever wrote: Hi, I'm stumped with a problem... I've got a BSD socket connection from inside a kext on another thread and I'm trying to find a way to cause it to abort without using a timeout or closing the connection. From userland, I've done the same thing by using a signal to abort the syscall, but haven't been able to figure out how to do the same thing from kernelspace. I've tried issuing sorwakeup() on my socket, but it seems to have no effect. I've tried a few other bit too, but this is the one that seemed to make the most sense. Anyone have any ideas? What do you mean by "abort"? If you do this in user mode, you kill the process, causing the kernel to shut down (close) all open file descriptors. 'sorwakeup' just wakes up those processes waiting for the receive side of the socket to get data. What are you trying to achieve? Regards, Justin -- Justin C. Walker, Curmudgeon-At-Large * Institute for General Semantics | "Weaseling out of things is what | separates us from the animals. | Well, except the weasel." | - Homer J Simpson *--------------------------------------*-------------------------------* _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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terminating a socket read from inside the kernel
by Rob McKeever 01 Apr '04

01 Apr '04

Hi, I'm stumped with a problem... I've got a BSD socket connection from inside a kext on another thread and I'm trying to find a way to cause it to abort without using a timeout or closing the connection. From userland, I've done the same thing by using a signal to abort the syscall, but haven't been able to figure out how to do the same thing from kernelspace. I've tried issuing sorwakeup() on my socket, but it seems to have no effect. I've tried a few other bit too, but this is the one that seemed to make the most sense. Anyone have any ideas? -Rob -- "Quidquid latine dictum sit, altum viditur." [demime 0.98b removed an attachment of type application/pkcs7-signature which had a name of smime.p7s] _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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