RE: Kernel Mocking
From: kernelnewbies-boun...@kernelnewbies.org [mailto:kernelnewbies-boun...@kernelnewbies.org] On Behalf Of Kenneth Adam Miller Sent: Friday, February 20, 2015 12:49 PM To: kernelnewbies@kernelnewbies.org Subject: Re: Kernel Mocking Well I think that a function or system call semantics replacement facility would be useful to unit testers everywhere. It would be benign of course, requiring that the unit testing framework request of the kernel that it replace the kernel facilities specified prior to the test, and automatically replace them afterward. So, this isn't anything akin to doing anything malicious, it requires user cooperation in order to hook. It's not like something forcibly done. I'm thinking of an intel pin for kernel level code. Kenneth, Please refrain from top posting. 8^) I was just thinking you might be able to leverage that gcc profiling mcount() function trick that ftrace uses. I don’t understand that well enough to say whether it would be applicable for what you want to do, but it would be something you could look into. You should check out ftrace in any case if you are interested in this kind of thing. It’s a way cool facility and comes already enabled on many distros. Jeff Haran On Fri, Feb 20, 2015 at 3:45 PM, Greg KH mailto:g...@kroah.com>> wrote: On Fri, Feb 20, 2015 at 03:26:40PM -0500, Kenneth Adam Miller wrote: > Thanks for your expedient answer! > > So, I was discussing an alternative to mocking; function hooking. But in a > benign way. Is there any way to, at runtime replace the functionality of code > in order that you specify what it does for any given kernel function? Not really, but there are some hacks you can do if you _really_ know what you are doing. Hint, don't do this, just write "normal" tests for your kernel code, we have lots of them already in the source tree, look in tools/selftests/. Best of luck, greg k-h ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Kernel Mocking
Well I think that a function or system call semantics replacement facility would be useful to unit testers everywhere. It would be benign of course, requiring that the unit testing framework request of the kernel that it replace the kernel facilities specified prior to the test, and automatically replace them afterward. So, this isn't anything akin to doing anything malicious, it requires user cooperation in order to hook. It's not like something forcibly done. I'm thinking of an intel pin for kernel level code. On Fri, Feb 20, 2015 at 3:45 PM, Greg KH wrote: > On Fri, Feb 20, 2015 at 03:26:40PM -0500, Kenneth Adam Miller wrote: > > Thanks for your expedient answer! > > > > So, I was discussing an alternative to mocking; function hooking. But in > a > > benign way. Is there any way to, at runtime replace the functionality of > code > > in order that you specify what it does for any given kernel function? > > Not really, but there are some hacks you can do if you _really_ know > what you are doing. > > Hint, don't do this, just write "normal" tests for your kernel code, we > have lots of them already in the source tree, look in tools/selftests/. > > Best of luck, > > greg k-h > ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Kernel Mocking
On Fri, Feb 20, 2015 at 03:26:40PM -0500, Kenneth Adam Miller wrote: > Thanks for your expedient answer! > > So, I was discussing an alternative to mocking; function hooking. But in a > benign way. Is there any way to, at runtime replace the functionality of code > in order that you specify what it does for any given kernel function? Not really, but there are some hacks you can do if you _really_ know what you are doing. Hint, don't do this, just write "normal" tests for your kernel code, we have lots of them already in the source tree, look in tools/selftests/. Best of luck, greg k-h ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Kernel Mocking
Thanks for your expedient answer! So, I was discussing an alternative to mocking; function hooking. But in a benign way. Is there any way to, at runtime replace the functionality of code in order that you specify what it does for any given kernel function? On Fri, Feb 20, 2015 at 3:24 PM, Greg KH wrote: > On Fri, Feb 20, 2015 at 02:51:25PM -0500, Kenneth Adam Miller wrote: > > So, in userland development, the idea of mocking is used to isolate > context > > management and machine configuration into a single class or set of > functions > > that can be reused, and also facilitate testing much easier. Google mock > is a > > great example. > > > > Say I develop a kernel module, and I want that module to have some > result X > > after some returned result, whatever that might be. Is there anything > similar > > for kernel code? > > Not really, sorry. Running in the kernel means you don't have much room > for "simulation". But you can use qemu, or other virtual machines and a > debugger to test your code if you really want to. > > Good luck! > > greg k-h > ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Kernel Mocking
On Fri, Feb 20, 2015 at 02:51:25PM -0500, Kenneth Adam Miller wrote: > So, in userland development, the idea of mocking is used to isolate context > management and machine configuration into a single class or set of functions > that can be reused, and also facilitate testing much easier. Google mock is a > great example. > > Say I develop a kernel module, and I want that module to have some result X > after some returned result, whatever that might be. Is there anything similar > for kernel code? Not really, sorry. Running in the kernel means you don't have much room for "simulation". But you can use qemu, or other virtual machines and a debugger to test your code if you really want to. Good luck! greg k-h ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Kernel Mocking
So, in userland development, the idea of mocking is used to isolate context management and machine configuration into a single class or set of functions that can be reused, and also facilitate testing much easier. Google mock is a great example. Say I develop a kernel module, and I want that module to have some result X after some returned result, whatever that might be. Is there anything similar for kernel code? ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
