March 2008 - Darwin-kernel - lists.apple.com

Re: Hotswap support?
by Michael Smith 04 Mar '08

04 Mar '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com On Mar 3, 2008, at 11:33 AM, Régis Duchesne wrote: Folks, What is the current Leopard support for hot-add/hot-remove of the following devices? o CPU (Mac OS does not seem to like ejectable CPUs in the ACPI tables) o Memory o PCI device o PCI Express device = Mike _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… Apple does not ship hardware with any of the above features, so support would seem to be moot. This email sent to site_archiver(a)lists.apple.com

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Re: Memory Mapping examples/documentation?
by mm w 04 Mar '08

04 Mar '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; bh=cDj92RHsmkETp1RFixrO28bhRb49ZSKXqV+RxxDrpGs=; b=Dg4HDEW2q+2iX+4dM6YGL652m1iG2m9d1NU5cbaVAU93nrZQ+aUrJOWjy+CJCsGIYePx2AqfsmM+jPL5aixFpLEJX2Fq+xWOwWVVOR6s+h4yrIK2CUAkuLGwPx5eoqCC3DY3ytj1SC35J0jHHrhcuFZgNqVicSXdPfEqBj0Xsjk= Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=pP2dwftSNLfzihUwe78piGzwllM1UxwSibVLegXDptq+exVUXR9MOPUg+oz0qvpOS4C+FEBrG98ySDmDxEFyWRxRp5EyRA1AJ588c6LwJuSq8NQVFbr1Uet9dCES4ZNVU3GL9nBBG+sq3BVz/zR2YZgf5HVT+jvi2kW4ClcF+eo= Hi Greg, this is a basic question, I'm going to try to give you some leads, imagine, we are in two rooms separated by a cupboard with two entries (double access), my room is called the Forgotten City :) now I'm going open a drawer and put something inside for you (and sure I can lock some drawers (keymaster)), you have several options to find what I gave: try to open every drawer or I can send you somewhere the "address" of this drawer (IPC), one more constraint you can't use a device file :) >$ cc wire.c -o test >$ ./test On Mon, Mar 3, 2008 at 2:27 PM, Greg <greg(a)kinostudios.com> wrote: > Thanks for the example mousse, but I'm not really sure that this > does... I compiled it and ran it like so: > > $ cc example.c > $ sudo ./a.out > > And got a lot of output along these lines: > > > addr = 800000 > > error = 268435459 > > addr = 802000 > > error = 268435459 > > addr = 802000 > > error = 268435459 > > addr = 803000 > > error = 268435459 > > addr = 803000 > > Am I correct in my understanding that task_wire(self,true) tells OS X > not to page the program out from memory? What then is vm_wire() used > for? > > Also, how do I use this for my purposes (which is to share memory > between my kext and the user-land program)? > > Thanks, and sorry for the lack of knowledge on my part, in my defense > I would read the documentation if I knew what documentation to read! :-p > > - Greg > > > > On Mar 3, 2008, at 2:37 PM, mm w wrote: > > > #include <stdio.h> > > #include <stdlib.h> > > #include <stdbool.h> > > #include <mach/vm_map.h> > > > > int main(int argc, char *argv[]) { > > vm_map_t self; > > kern_return_t kret; > > > > self = mach_task_self(); > > kret = task_wire(self, true); > > > > if (kret == KERN_INVALID_HOST) > > fprintf(stderr, "vm_wire KERN_INVALID_HOST.\n"); > > else if (kret) > > fprintf(stderr,"error = %d\n", kret); > > > > > > vm_size_t size; > > host_priv_t host; > > > > host = mach_host_self(); > > void *ptr; > > int i = 0; > > host_page_size(host, &size); > > > > do { > > fork(); > > ptr = malloc(size); > > printf("addr = %X\n" , ptr); > > kret = vm_wire(host, self, (vm_address_t) ptr, size, VM_PROT_READ > > | VM_PROT_WRITE); > > > > if (kret == KERN_INVALID_HOST) > > fprintf(stderr, "vm_wire KERN_PROTECTION_FAILURE.\n"); > > else if (kret == KERN_INVALID_HOST) > > fprintf(stderr, "vm_wire KERN_INVALID_HOST.\n"); > > else if (kret) > > fprintf(stderr,"error = %d\n", kret); > > > > } while(++i < 5); > > > > return 0; > > } > > > > On Mon, Mar 3, 2008 at 11:06 AM, Greg <greg(a)kinostudios.com> wrote: > >> > >> On Mar 3, 2008, at 11:23 AM, mm w wrote: > >> > >>> Hi Greg, > >>> > >>> In the doc there is a small chapter regarding Memory wiring called: > >>> Memory Mapping and Block Copying, I guess it's exactly what you > >>> asked, > >>> as Michael said most people think that not using IOKit is more > >>> efficient, for the most of cases, it's really wrong, as you have may > >>> be noticed IOKit is not a full C++, it's based on Embedded C++, > >>> Iokit > >>> provides many facilities and kern controls, > >> > >> The only reason that I don't want to make an IOKit kext is that I > >> feel > >> it would over-complicate my code. I don't have much time to learn > >> all > >> the paradigms of creating a driver and then a userclient when all I > >> need is one function to start the kernel extension (kextname_start) > >> and one function to stop it (kextname_stop). > >> > >> > >> > >>> and sure it depends on what you want to accomplish, if it's to learn > >>> or implement something that doesn't exist, your are on the way, if > >>> it's for implementing something that already exists not sure :), and > >>> sure the xnu source is always your best doc: osfmk/vm/vm_user.c > >> > >> Are the functions in vm_user.c the only functions available to do > >> what > >> I want? And are you saying that no actual documentation on how to use > >> those functions to do memory mapping exists? > >> > >> Because if that's the case then converting my extension to IOKit > >> stuff > >> might be easier than wading through kernel code. > >> > >> Thanks, > >> > >> - Greg > >> > > > > > > > > -- > > -mmw > > > _______________________________________________ > > Do not post admin requests to the list. They will be ignored. > > Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) > > Help/Unsubscribe/Update your Subscription: > > http://lists.apple.com/mailman/options/darwin-kernel/greg%40kinostudios.com > > > > This email sent to greg(a)kinostudios.com > > -- -mmw _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com

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Re: Memory Mapping examples/documentation?
by Greg 03 Mar '08

03 Mar '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com $ cc example.c $ sudo ./a.out And got a lot of output along these lines: addr = 800000 error = 268435459 addr = 802000 error = 268435459 addr = 802000 error = 268435459 addr = 803000 error = 268435459 addr = 803000 - Greg On Mar 3, 2008, at 2:37 PM, mm w wrote: #include <stdio.h> #include <stdlib.h> #include <stdbool.h> #include <mach/vm_map.h> int main(int argc, char *argv[]) { vm_map_t self; kern_return_t kret; self = mach_task_self(); kret = task_wire(self, true); if (kret == KERN_INVALID_HOST) fprintf(stderr, "vm_wire KERN_INVALID_HOST.\n"); else if (kret) fprintf(stderr,"error = %d\n", kret); vm_size_t size; host_priv_t host; host = mach_host_self(); void *ptr; int i = 0; host_page_size(host, &size); do { fork(); ptr = malloc(size); printf("addr = %X\n" , ptr); kret = vm_wire(host, self, (vm_address_t) ptr, size, VM_PROT_READ | VM_PROT_WRITE); if (kret == KERN_INVALID_HOST) fprintf(stderr, "vm_wire KERN_PROTECTION_FAILURE.\n"); else if (kret == KERN_INVALID_HOST) fprintf(stderr, "vm_wire KERN_INVALID_HOST.\n"); else if (kret) fprintf(stderr,"error = %d\n", kret); } while(++i < 5); return 0; } On Mar 3, 2008, at 11:23 AM, mm w wrote: Hi Greg, and sure it depends on what you want to accomplish, if it's to learn or implement something that doesn't exist, your are on the way, if it's for implementing something that already exists not sure :), and sure the xnu source is always your best doc: osfmk/vm/vm_user.c Thanks, - Greg -- -mmw _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/greg%40kinostudios.com _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… Thanks for the example mousse, but I'm not really sure that this does... I compiled it and ran it like so: Am I correct in my understanding that task_wire(self,true) tells OS X not to page the program out from memory? What then is vm_wire() used for? Also, how do I use this for my purposes (which is to share memory between my kext and the user-land program)? Thanks, and sorry for the lack of knowledge on my part, in my defense I would read the documentation if I knew what documentation to read! :-p On Mon, Mar 3, 2008 at 11:06 AM, Greg <greg(a)kinostudios.com> wrote: In the doc there is a small chapter regarding Memory wiring called: Memory Mapping and Block Copying, I guess it's exactly what you asked, as Michael said most people think that not using IOKit is more efficient, for the most of cases, it's really wrong, as you have may be noticed IOKit is not a full C++, it's based on Embedded C++, Iokit provides many facilities and kern controls, The only reason that I don't want to make an IOKit kext is that I feel it would over-complicate my code. I don't have much time to learn all the paradigms of creating a driver and then a userclient when all I need is one function to start the kernel extension (kextname_start) and one function to stop it (kextname_stop). Are the functions in vm_user.c the only functions available to do what I want? And are you saying that no actual documentation on how to use those functions to do memory mapping exists? Because if that's the case then converting my extension to IOKit stuff might be easier than wading through kernel code. This email sent to greg(a)kinostudios.com This email sent to site_archiver(a)lists.apple.com

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Re: Memory Mapping examples/documentation?
by mm w 03 Mar '08

03 Mar '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; bh=fknlB1JGcY9T/T87K9PKxGvtaUiq6XIq6B2i8UQf2aU=; b=uUZtdNj4AdruMotg+3g357tG0eMTCgU+iVpZ8Bh8l45VxRvtQt8bpIpF/9Zjn+9IiZtuVkxsmc3wZpsALex+5/62sW6/BAeZwhyik1HCRIE99zy9ywUGShrvHcT+7KkCDv0tud3IwLI64Tz8eNr4kbs8bgQTlUKMVzozyG6J1/0= Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=UA2vbqViRmDBENLZTffJaprEnErcqW5qLv1XUMSyqSaWKOEO11p6hPnRwTv3UN73oonavXMv4brX2rYudzU1Z5iJNCNB+jhNLR5RavEzUPbcvLgcnm4sDlS+fQkZHxMs53Cs7pnp5Pi4utlVe7YCujUI9RS783TCWMUNLd+VZZI= #include <stdio.h> #include <stdlib.h> #include <stdbool.h> #include <mach/vm_map.h> int main(int argc, char *argv[]) { vm_map_t self; kern_return_t kret; self = mach_task_self(); kret = task_wire(self, true); if (kret == KERN_INVALID_HOST) fprintf(stderr, "vm_wire KERN_INVALID_HOST.\n"); else if (kret) fprintf(stderr,"error = %d\n", kret); vm_size_t size; host_priv_t host; host = mach_host_self(); void *ptr; int i = 0; host_page_size(host, &size); do { fork(); ptr = malloc(size); printf("addr = %X\n" , ptr); kret = vm_wire(host, self, (vm_address_t) ptr, size, VM_PROT_READ | VM_PROT_WRITE); if (kret == KERN_INVALID_HOST) fprintf(stderr, "vm_wire KERN_PROTECTION_FAILURE.\n"); else if (kret == KERN_INVALID_HOST) fprintf(stderr, "vm_wire KERN_INVALID_HOST.\n"); else if (kret) fprintf(stderr,"error = %d\n", kret); } while(++i < 5); return 0; } On Mon, Mar 3, 2008 at 11:06 AM, Greg <greg(a)kinostudios.com> wrote: > > On Mar 3, 2008, at 11:23 AM, mm w wrote: > > > Hi Greg, > > > > In the doc there is a small chapter regarding Memory wiring called: > > Memory Mapping and Block Copying, I guess it's exactly what you asked, > > as Michael said most people think that not using IOKit is more > > efficient, for the most of cases, it's really wrong, as you have may > > be noticed IOKit is not a full C++, it's based on Embedded C++, Iokit > > provides many facilities and kern controls, > > The only reason that I don't want to make an IOKit kext is that I feel > it would over-complicate my code. I don't have much time to learn all > the paradigms of creating a driver and then a userclient when all I > need is one function to start the kernel extension (kextname_start) > and one function to stop it (kextname_stop). > > > > > and sure it depends on what you want to accomplish, if it's to learn > > or implement something that doesn't exist, your are on the way, if > > it's for implementing something that already exists not sure :), and > > sure the xnu source is always your best doc: osfmk/vm/vm_user.c > > Are the functions in vm_user.c the only functions available to do what > I want? And are you saying that no actual documentation on how to use > those functions to do memory mapping exists? > > Because if that's the case then converting my extension to IOKit stuff > might be easier than wading through kernel code. > > Thanks, > > - Greg > -- -mmw _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com

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Hotswap support?
by Régis Duchesne 03 Mar '08

03 Mar '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com User-agent: Icedove 1.5.0.9 (X11/20061220) Folks, What is the current Leopard support for hot-add/hot-remove of the following devices? o CPU (Mac OS does not seem to like ejectable CPUs in the ACPI tables) o Memory o PCI device o PCI Express device Thanks, -- hpreg _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com

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Re: Memory Mapping examples/documentation?
by Greg 03 Mar '08

03 Mar '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com On Mar 3, 2008, at 11:23 AM, mm w wrote: Hi Greg, In the doc there is a small chapter regarding Memory wiring called: Memory Mapping and Block Copying, I guess it's exactly what you asked, as Michael said most people think that not using IOKit is more efficient, for the most of cases, it's really wrong, as you have may be noticed IOKit is not a full C++, it's based on Embedded C++, Iokit provides many facilities and kern controls, and sure it depends on what you want to accomplish, if it's to learn or implement something that doesn't exist, your are on the way, if it's for implementing something that already exists not sure :), and sure the xnu source is always your best doc: osfmk/vm/vm_user.c Thanks, - Greg _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… The only reason that I don't want to make an IOKit kext is that I feel it would over-complicate my code. I don't have much time to learn all the paradigms of creating a driver and then a userclient when all I need is one function to start the kernel extension (kextname_start) and one function to stop it (kextname_stop). Are the functions in vm_user.c the only functions available to do what I want? And are you saying that no actual documentation on how to use those functions to do memory mapping exists? Because if that's the case then converting my extension to IOKit stuff might be easier than wading through kernel code. This email sent to site_archiver(a)lists.apple.com

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Re: Memory Mapping examples/documentation?
by Greg 03 Mar '08

03 Mar '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com On Mar 3, 2008, at 4:15 AM, Michael Smith wrote: Thanks, - Greg _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… Can you explain why you think it would be more efficient, or that it would simplify your code? I ask because it's possible that it might, but without seeing your reasoning I can't comment on whether it might actually be, and it's common for folks to think that mapping would be cheaper when in fact it's not. I can only say that I need to be able to move relatively small chunks of data (around 90 bytes per chunk) in potentially large quantities as fast as is possible across the kernel/user boundary. You have to become an I/O Kit extension to use the IODataQueue. There are other ways to share mapped memory between the kernel and user space however. ... What would those ways be specifically? All I'd like is some example code on how to do this in C. Then at least I'd be able to experiment with both approaches and see which one yields the best results. Unless your data is large, you'll tend to find that copying it along with the notification (as you are currently doing) will be easier and more efficient than trying to manage a shared memory buffer. Again, it would help to be able to put this in perspective with your current workload. So yeah, like I said above, the data chunks are not large (I don't think), but I need to be able to move large quantities of them as quickly as is possible to the user-land program. This email sent to site_archiver(a)lists.apple.com

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Re: Memory Mapping examples/documentation?
by mm w 03 Mar '08

03 Mar '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; bh=X9mXpV/SveoYN+vKgFduC2zeedamk3gKr7q9nKPN0N4=; b=nSCXzlCacsSFHww8ju/y6+M/nsV02N5Wrq2cDJYdrrXZBKXmcUm5iD+qmlhrWASXq8jmeLWdhMbmHt1+5SRAdjwpYRMGlW8BeuvijG6l7uAIRjZtYpkTihDFiWDK9935BNpEs4uU7GDf2Kg2Szb8odDmd/ecOW4Y8f1BiraSfjQ= Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=LwdDecWK1laxy/fcg6+ZSZbKPSeHPtOZU4w2YJO9Oeblg2Xv4cHbgX/8H0kb3STL6QH2lCYXVR20x2VKTIDmyUPd3sReiR6LwCVRnCPT/5wL7xDYi5QTdZsGFgWjm5RTUO2l8hHV92Vg0XwHOZ3uLeC7rG/526u0WGz7Tz4KYRw= Hi Greg 2, :) and sure it depends on what you want to accomplish, if it's to learn or implement something that doesn't exist, your are on the way, if it's for implementing something that already exists not sure :), and sure the xnu source is always your best doc: osfmk/vm/vm_user.c Cheers! _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com

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Re: Memory Mapping examples/documentation?
by mm w 03 Mar '08

03 Mar '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; bh=NfntJmtJh14zi64M7JYqzJ4W9F47XNWMnveVFOYi9J4=; b=bwU/AlNQAe6gQ06qgXXxajQrrToNxln7+yYJMwljTGvYhiGMe8l9lsx9LAOeZwHI0VUU9wECopMb7D6MPrrITVdhl05QirFdOC/Of33WssI0RhtyUjR8lLKnJT9ix+DwXh25Q8FVEtgetMJKTWdCu0tWApkuvJhPEAIpEvndS+w= Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=XI641EcKkeXqPrCeCg8bGUTNMIt0vrGeP064WNzjQ2JhEMUjO3goKoumVazV2GgzsyJzj9G006eIhJ2x4UoPrVstXYuZFG5HMWV4Zax/tCbXtvs2r5dL01P+4AVbcLuinbxZeugcPCXU+/DsJ7P7gHKAbIFlD6784bts9yh4ed0= Hi Greg, In the doc there is a small chapter regarding Memory wiring called: Memory Mapping and Block Copying, I guess it's exactly what you asked, as Michael said most people think that not using IOKit is more efficient, for the most of cases, it's really wrong, as you have may be noticed IOKit is not a full C++, it's based on Embedded C++, Iokit provides many facilities and kern controls, If you want re/over/write many of them it's not a problem, some people do it for special devels (and also, for your code "perenity") you can see the evolution of xnu, sometimes there are strong gaps betwen versions especially at kpi level, but, as you want, you can develop a la BSD (your kmod in C) using sysctl, vm APIs ecetera... Cheers! -mmw On Mon, Mar 3, 2008 at 1:15 AM, Michael Smith <drivers(a)mu.org> wrote: > > On Mar 2, 2008, at 11:30 PM, Greg wrote: > > > Hi, I'm searching for documentation or examples on how to transfer > > data from a kernel extension written in C to a user-space program. > > Currently I am using kernel controls to do this, but I would prefer > > to do this using memory mapping as I feel it would be more > > efficient, and I think would also simplify my code. > > Can you explain why you think it would be more efficient, or that it > would simplify your code? > > I ask because it's possible that it might, but without seeing your > reasoning I can't comment on whether it might actually be, and it's > common for folks to think that mapping would be cheaper when in fact > it's not. > > > > I've seen one example that uses IOConnectMapMemory in a user-space C > > program to connect to an IOKit kernel extension written (obviously) > > in C++. That kernel extension creates an IODataQueue and uses it as > > shared memory. > > > > Based on this I have two questions: > > > > 1) Can I convert my C kernel extension (of the Name_start/Name_stop > > kind) directly to C++ (by simply changing its file-extension) so > > that I can use the IODataQueue? > > No; you would need to refactor your extension to some degree to do > this. It's possible to be a mostly-C extension but participate in the > I/O Kit world, but it takes more than just a file renaming. > > > > 2) Since I'm guessing the answer to #1 is probably "no", then are > > there any examples of how to do something like this in a C-based > > kernel extension? Or any documentation? I do not want to make my > > kernel extension an IOKit extension. > > You have to become an I/O Kit extension to use the IODataQueue. There > are other ways to share mapped memory between the kernel and user > space however. > > > > I'd like to put/copy data into this shared memory, and upon doing so > > have the user-space program be notified of the new data so that it > > can be immediately used/copied. > > Unless your data is large, you'll tend to find that copying it along > with the notification (as you are currently doing) will be easier and > more efficient than trying to manage a shared memory buffer. Again, > it would help to be able to put this in perspective with your current > workload. > > = Mike > > > > _______________________________________________ > Do not post admin requests to the list. They will be ignored. > Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) > Help/Unsubscribe/Update your Subscription: > http://lists.apple.com/mailman/options/darwin-kernel/openspecies%40gmail.com > > This email sent to openspecies(a)gmail.com > -- -mmw _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com

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Re: Memory Mapping examples/documentation?
by Michael Smith 03 Mar '08

03 Mar '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com On Mar 2, 2008, at 11:30 PM, Greg wrote: Based on this I have two questions: = Mike _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… Hi, I'm searching for documentation or examples on how to transfer data from a kernel extension written in C to a user-space program. Currently I am using kernel controls to do this, but I would prefer to do this using memory mapping as I feel it would be more efficient, and I think would also simplify my code. Can you explain why you think it would be more efficient, or that it would simplify your code? I ask because it's possible that it might, but without seeing your reasoning I can't comment on whether it might actually be, and it's common for folks to think that mapping would be cheaper when in fact it's not. I've seen one example that uses IOConnectMapMemory in a user-space C program to connect to an IOKit kernel extension written (obviously) in C++. That kernel extension creates an IODataQueue and uses it as shared memory. 1) Can I convert my C kernel extension (of the Name_start/Name_stop kind) directly to C++ (by simply changing its file-extension) so that I can use the IODataQueue? No; you would need to refactor your extension to some degree to do this. It's possible to be a mostly-C extension but participate in the I/O Kit world, but it takes more than just a file renaming. 2) Since I'm guessing the answer to #1 is probably "no", then are there any examples of how to do something like this in a C-based kernel extension? Or any documentation? I do not want to make my kernel extension an IOKit extension. You have to become an I/O Kit extension to use the IODataQueue. There are other ways to share mapped memory between the kernel and user space however. I'd like to put/copy data into this shared memory, and upon doing so have the user-space program be notified of the new data so that it can be immediately used/copied. Unless your data is large, you'll tend to find that copying it along with the notification (as you are currently doing) will be easier and more efficient than trying to manage a shared memory buffer. Again, it would help to be able to put this in perspective with your current workload. This email sent to site_archiver(a)lists.apple.com

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