May 2016 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

how to properly "export" a new header file to user space?
by Robert P. J. Day May 18, 2016

May 18, 2016

just want to make i'm using the new UAPI infrastructure properly, since i remember the old days of stuffing "header-y" all over the place in Kbuild files. say i want to add a new driver to the kernel, so i create the directory /drivers/rday, and add some code and i create a header file, "rday1.h", that will be used by both my kernel code *and* needs to be included by user space code as well. normally, i could just leave that header file in that directory, and let the source file use: #include "rday1.h" but if i want that header file visible in user space, as i read it, i can create a new directory at the top level of the kernel source: include/uapi/rday/ inside of which i can place the file "rday1.h", which has the following consequences. first, given this code in the top-level Makefile: # Use USERINCLUDE when you must reference the UAPI directories only. USERINCLUDE := \ -I$(srctree)/arch/$(hdr-arch)/include/uapi \ -Iarch/$(hdr-arch)/include/generated/uapi \ -I$(srctree)/include/uapi \ -Iinclude/generated/uapi \ -include $(srctree)/include/linux/kconfig.h # Use LINUXINCLUDE when you must reference the include/ directory. # Needed to be compatible with the O= option LINUXINCLUDE := \ -I$(srctree)/arch/$(hdr-arch)/include \ -Iarch/$(hdr-arch)/include/generated/uapi \ -Iarch/$(hdr-arch)/include/generated \ $(if $(KBUILD_SRC), -I$(srctree)/include) \ -Iinclude \ $(USERINCLUDE) my own kernel code should now use the include directive: #include <rday/rday1.h> which should properly locate that header file. and, second, user space code can use the same directive as long as i extend the user space header file search path to include "<kernel-source-tree/include/uapi", correct? am i thinking about this the right way? i'm using the model under drivers/mtd, where one sees examples like: nand/fsmc_nand.c:#include <mtd/mtd-abi.h> ubi/cdev.c:#include <mtd/ubi-user.h> with directory contents: $ tree include/uapi/mtd include/uapi/mtd ├── inftl-user.h ├── Kbuild ├── mtd-abi.h ├── mtd-user.h ├── nftl-user.h └── ubi-user.h $ i also note that include/uapi/mtd includes header files meant to be included *only* from user space, such as mtd-user.h, which is fine. so is this the correct approach? or am i missing something easier? rday p.s. i also note the Kbuild file "include/uapi/mtd/Kbuild", for use if i want to export those headers with: $ make headers_install but if i don't want to export my own header files that way, i see no need to add a Kbuild file, at least not for the moment. thoughts? -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================

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Run queue corruption issue
by Jerrin Shaji George May 18, 2016

May 18, 2016

Hi All, I wanted help with a piece of code that I have been working on. Please see - https://gist.github.com/jerrinsg/333e584d1f65dc95b9f13b61dcebdaa7 I have written two function, migrate_to and migrate_back. migrate_to is used to remove a process from the run queue, and migrate_back is used to insert this process back into the run queue. The gist is from a taken from a larger project, where we are working on building a mechanism to support thread migration across heterogeneous processors. migrate_to_call() will be called by a thread which wants to remove itself from the run queue (hence, it will pass the current task struct as the migration argument). Once the other processor completes execution of the assigned task, it will interrupt the main processor, which runs an interrupt handler, which in turn calls the migrate_back_call() function. It passes the task struct of the process that was removed from the run queue earlier to this function. This mechanism works fine the first few times, but when this process is repeated many times in a loop, I am seeing a run queue corruption: https://gist.github.com/jerrinsg/0ab09cd435d8d2cb6ae692c7e6f4f26b Is there anything wrong in the process dequeue or enqueue function that I have written? Please help! Kernel used: Linux 3.13 Thanks, Jerrin

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Re: can anyone tell me which function to call to pause the kernel
by Mulyadi Santosa May 18, 2016

May 18, 2016

On Mon, May 16, 2016 at 7:36 AM, walkerlala <ablacktshirt(a)gmail.com> wrote: > On 2016年05月16日 01:36, Mulyadi Santosa wrote: > >> >> >> On Thu, May 12, 2016 at 9:55 PM, walkerlala <ablacktshirt(a)gmail.com >> <mailto:ablacktshirt@gmail.com>> wrote: >> >> I successfully insert some function into the kernel code and make it >> execute when the kernel start up, but I just can't make the kernel >> stop >> executing. Are there any functions which can pause the kernel so that >> I >> prompt the user, and let the user input a command(maybe a comment to >> display the current time. Something like a shell would do) and >> interact ? >> (I had checked the "sys_***" functions in this page: >> http://docs.cs.up.ac.za/programming/asm/derick_tut/syscalls.html >> but just can't find a proper one ) >> >> _______________________________________________ >> Kernelnewbies mailing list >> Kernelnewbies(a)kernelnewbies.org <mailto: >> Kernelnewbies(a)kernelnewbies.org> >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >> >> >> Hi... >> >> sounds like what kgdb does. But not sure if it is still maintained or not. >> >> btw, kernel can not be paused, actually. if you really need that, you >> need to run linux kernel inside virtual machine and pause the virtual >> machine. But doing that, you will also pause user space too :) >> >> -- >> regards, >> >> Mulyadi Santosa >> Freelance Linux trainer and consultant >> >> blog: the-hydra.blogspot.com <http://the-hydra.blogspot.com> >> training: mulyaditraining.blogspot.com < >> http://mulyaditraining.blogspot.com> >> > > Hi, thanks for reply. > > I know using a debugger or virtual machine would help a little bit, but > that's not interactive any more. What I want is just a shell-like > "interactive" kernel (may be I am a little naive to think that ?) > > Why the kernel cannot be stopped ? I think, now that if the kernel can be > interrupted, then why can't it be stopped by some mechanisms ? > > Regards, > > Hi... please add kernelnewbies to cc: list too next time :) Kernel can't be stopped, because it's actually servicing event mostly generated by hardware (interrupts etc) or user space (syscall etc). So unless you stop these two aspects to raise events, basically kernel will still do its works. -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com

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How to locally maintain an end-of-life kernel branch?
by Michael Harless May 17, 2016

May 17, 2016

Hi, Sorry if this is covered somewhere, I haven't been able to find much yet in my searches. I'm working on a project using the LTS 3.14 kernel, but I'll need to be supporting it long after official support ends on kernel.org for the branch. Are there any pointers or suggestions on how to monitor for security and bug fixes that I'll need to pull in and merge myself? I'm watching the lkml for patches and trying to follow the latest changes via git, but I'm sure that I'll miss things in all of the traffic. Thanks! --Mike

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Kernel memory
by Ronit Halder May 17, 2016

May 17, 2016

Hi, Where in the memory kernel is located in the boot time? regards, Ronit

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LINKS PLEASE
by Gnoleba GNOGBO May 17, 2016

May 17, 2016

Hi ! I am beginning my learn of Linux ! Can you show (give) me the good link for : 1. the management of the all memory in Linux ( Rom, Ram, cache, Registers, swap and fs) 2. the management of the all process (initialization, user process, kernel process ) 3. the all tables in memory to manage the data and process Regards Gnoleba -- *Gnoleba GNOGBO* *Mobile : * *+225 02 60 17 66**Skype* : *gnognoleba*

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Kernel segment
by Ronit Halder May 17, 2016

May 17, 2016

Hi, What are segments in kernel image? In kimage structure there is a member called entry. What does it represents? regards

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USB hub device
by tech learner May 17, 2016

May 17, 2016

Hi, I have a custom hub device which has control endpoints. On sending certain control messages the device in the downstream is enabled. Now, my approach as i think : Register a driver as hub class driver with appropriate match flags. In my probe i send vendor specific commands on control endpoint to the hub which enables the device. Here, my question is : Will the device enumeration end up in my driver or will the kernel hub driver still do the enumeration ? If the enumeration ends up in my driver, how can i let the kernel hub driver do that ? Thanks, learner

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How to initialize the new attributes in process control block.
by Youcun Liu May 16, 2016

May 16, 2016

Dear all, I am now working on building my own linux kernel and I want to add a new attribute into the process control block. Then I will feed some data to the new attribute from a user application. Finally I want to use the date to improve the some original kernel algorithm(e.g process schduling). I tried to initialize the new attribute directly in the 'task_struct', obviously, it failed. So I decide to initialize the new attribute at the very beginning, but I do not know how. Besides, I have trouble in finding out which function can help me feed data to the new attribute. Could you please give me some suggestions and help? Thanks a lot. Best regards, Youcun Liu

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can anyone tell me which function to call to pause the kernel
by walkerlala May 15, 2016

May 15, 2016

I successfully insert some function into the kernel code and make it execute when the kernel start up, but I just can't make the kernel stop executing. Are there any functions which can pause the kernel so that I prompt the user, and let the user input a command(maybe a comment to display the current time. Something like a shell would do) and interact ? (I had checked the "sys_***" functions in this page: http://docs.cs.up.ac.za/programming/asm/derick_tut/syscalls.html but just can't find a proper one )

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