March 2018 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

Hang in FUTEX_WAKE_PRIVATE after clock_gettime
by Jeffrey Walton March 24, 2018

March 24, 2018

Hi Everyone, I'm working with Botan (https://botan.randombit.net/) It is a TLS security library written in C++11. On an old Pentium III machine the self tests are hanging. Other platforms are OK. The strace tail is shown below. I am not that familiar with this type of debugging, and I am looking for a direction to go. I've seen some similar problems on the web, including an indictment of clock_gettime, but the problems lack a good analysis of the problem. My question is, is a futex with a 2147483647 or -1 expected? Where should I be looking to begin to narrow the problem down? Thanks in advance. ************************************************** $ sudo strace ./botan-test block execve("./botan-test", ["./botan-test", "block"], [/* 14 vars */]) = 0 brk(NULL) = 0x9af9000 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) readlink("/proc/self/exe", "/home/jwalton/botan/botan-test", 4096) = 30 mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f4e000 ... stat64("src/tests/data/block/noekeon.vec", {st_mode=S_IFREG|0664, st_size=121320, ...}) = 0 stat64("src/tests/data/block/aria.vec", {st_mode=S_IFREG|0664, st_size=2663, ...}) = 0 stat64("src/tests/data/block/des.vec", {st_mode=S_IFREG|0664, st_size=28722, ...}) = 0 getdents(3, /* 0 entries */, 32768) = 0 close(3) = 0 open("src/tests/data/block/aes.vec", O_RDONLY|O_LARGEFILE) = 3 read(3, "# Test vectors from NIST CAVP AE"..., 8191) = 8191 clock_gettime(CLOCK_REALTIME, {1521879372, 559396333}) = 0 futex(0xb78b6a34, FUTEX_WAKE_PRIVATE, 2147483647) = 0 <hang here> ************************* This old machine runs Peppermint, which is a Ubuntu derivative. $ lsb_release -a No LSB modules are available. Distributor ID: Peppermint Description: Peppermint 8 Eight Release: 8 Codename: xenial $ uname -a Linux coppermine 4.13.0-37-generic #42~16.04.1-Ubuntu SMP Wed Mar 7 16:02:25 UTC 2018 i686 i686 i686 GNU/Linux

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probe gets called without i2c device
by MUHAMMED ASAD P T March 23, 2018

March 23, 2018

Hi all, We didn't connect our i2c device with our board. But kernel driver subsystem calls the probe function from driver code. How to debug the issue. our observation is as follows, In driver, if we comment out the .id_table in driver struct, then it is not loaded. When the device is connected or not, both the time, the driver is not loaded.

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probe gets called without i2c device
by MUHAMMED ASAD P T March 23, 2018

March 23, 2018

Hi all, We didn't connect our i2c device with our board. But kernel driver subsystem calls the probe function from driver code. How to debug the issue. Thanks & Regards - Asad IQ Root Technologies

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LKCAMP - Linux Kernel study group - volunteers
by Helen Fornazier March 22, 2018

March 22, 2018

Hello, We are starting a study group in Brazil called LKCAMP at the University of Campinas (Unicamp) to help students to get started in kernel development. Our guides are strongly based on the tutorials from kernelnewbies.org (thank you for maintaining those). We are starting meetings every Tuesday night (starting on 20th March at 3pm PST) and we will probably have lots of questions in the #kernelnewbies IRC channel coming from the students during the workshops. It would be really nice to have some people online on the IRC channel between 4pm PST to 6pm PST to help us answer their questions, I would really appreciate if I could get some help and also to keep the students motivated, at least for the ramp up phase. Would any of you be interested in volunteering? More information about the group: https://goo.gl/Y4zVUZ (feedbacks are welcome). I really appreciate kernelnewbies efforts and we hope to contribute back to the community with this project :) Thanks Helen Koike

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sysfs unbind, miscdev
by Martin Kaiser March 21, 2018

March 21, 2018

Dear all, I have a driver that is an spi device on one side and a miscdevice on the other. By default, it has the sysfs bind and unbind nodes (I know that I can deactiate them). Surprisingly to me, I can unbind the driver from the spi device on the bus while there's a user space client that has an open connection to the miscdev. (If the driver was a module, I don't think I could unload it at this point.) During the unbind, the driver's remove function is called and all devres resources are freed. Amongst them is a struct that is used as file->prvate_data for the miscdev. The client can still continue to write to the miscdev and crash the driver because file->private_data points to invalid data now. What is the correct way to handle this? Is there a way to "disconnect" all clients of the miscdev during remove? Thanks, Martin

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Why do some config options return limited info from a search?
by John Whitmore March 20, 2018

March 20, 2018

I'm trying to build the required options for my Laptop into the kernel, so not modules. When you search, in make menuconfig, for a config option you usually get very useful info about where it is, in the menus, and what its prompt is. This makes them easier to find. Sometimes however you get a module which don't give this information. Is this intentional, signify something, or just an oversight for that config option? For example SND_HDA_CORE: Symbol: SND_HDA_CORE [=m] Type : tristate Defined at sound/hda/Kconfig:1 Depends on: SOUND [=y] && !UML && SND [=y] Selects: REGMAP [=y] Selected by: - SND_HDA_EXT_CORE [=m] && SOUND [=y] && !UML && SND [=y] - SND_HDA [=m] && SOUND [=y] && !UML && SND [=y]

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Re: Problem installing kernel due to virtualbox?
by Alex Arvelaez March 17, 2018

March 17, 2018

> I've been AWOL working on other things for an age, so just getting back up to speed and building a kernel. Everything built successfully but when I try to install the kernel (64bit laptop) it fails due to a virtualbox error. > > ERROR (dkms apport): kernel package linux-headers-4.16.0-rc5 is not supported > Error! Bad return status for module build on kernel: 4.16.0-rc5 (x86_64) > Consult /var/lib/dkms/virtualbox/5.0.40/build/make.log for more information. > > I've had a look at that log file but it doesn't say a whole lot more: > > ...linux/scripts/Makefile.build:583: recipe for target '/var/lib/dkms/virtualbox/5.0.40/build/vboxdrv' failed > make[5]: *** [/var/lib/dkms/virtualbox/5.0.40/build/vboxdrv] Error 2 > Makefile:1552: recipe for target '_module_/var/lib/dkms/virtualbox/5.0.40/build' failed > make[4]: *** [_module_/var/lib/dkms/virtualbox/5.0.40/build] Error 2 > Makefile:24: recipe for target '__sub-make' failed > make[3]: *** [__sub-make] Error 2 > > An Internet search did throw up a few pages about a virtualbox error [1] but I'm not sure the relevance to installing a Linux Kernel. Unless 'sudo make install' is running an Ubuntu script which tries to mess with virtual box. I have removed virtualbox from this machine and tried again but I've still got the same error message in the install process. Maybe I have to reboot after removing virtualbox but it still seems a bit tightly coupled? you probably want to remove virtualbox-dkms. Your system is trying to recompile the vbox driver for your newly compiled kernel and failing because it's not supported. I'm not sure what triggers dkms specifically so I'm not sure how to avoid it. Regards, Alex

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Driver as built-in instead of module
by MUHAMMED ASAD P T March 16, 2018

March 16, 2018

Hi, We need to add the driver as 'built in' in kernel. We had changed in kernel configuration for our custom driver. But, when the kernel is booted up, it is not calling the driver. what are the necessary steps to do this built-in to Kernel? Thanks & Regards - Asad IQ Root Technologies

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Out-of-tree module build in a dedicated build directory.
by Aleksei Fedotov March 15, 2018

March 15, 2018

Hello, I have a question regarding building of out-of-tree kernel modules in separate build directory. I have a source tree containing two out-of-tree kernel modules which is spread in two directories, module1 and module2. The build produces two independent modules: module1.ko and module2.ko. $ tree --charset=ascii . |-- Kbuild |-- module1 | |-- Kbuild | `-- task1.c `-- module2 |-- Kbuild `-- task2.c The root Kbuild points on sub-directories where the actual modules are located: $ cat Kbuild obj-y += module1/ obj-y += module2/ I want to use a dedicated build directory, so I could build the same set of sources for different platforms (ARM and x86). It looks like passing O= or KBUILD_OUTPUT= doesn't work for out of tree modules. So, I've tried passing 'src' directory directly to the make command, but that seems to cause a run-away recursion in the Kbuild: make V=1 -C $(KDIR) M=`pwd`/build_x86 src=`pwd` make: Entering directory '/home/lexa/linux_build' make -C /home/lexa/linux O=/home/lexa/linux_build/. make -C /home/lexa/linux_build KBUILD_SRC=/home/lexa/linux \ -f /home/lexa/linux/Makefile test -e include/generated/autoconf.h -a -e include/config/auto.conf || ( \ echo >&2; \ echo >&2 " ERROR: Kernel configuration is invalid."; \ echo >&2 " include/generated/autoconf.h or include/config/auto.conf are missing.";\ echo >&2 " Run 'make oldconfig && make prepare' on kernel src to fix it."; \ echo >&2 ; \ /bin/false) mkdir -p /home/lexa/module/build_arm/.tmp_versions ; rm -f /home/lexa/module/build_arm/.tmp_versions/* make -f /home/lexa/linux/scripts/Makefile.build obj=/home/lexa/module/build_arm make -f /home/lexa/linux/scripts/Makefile.build obj=/home/lexa/module/build_arm/module1 make -f /home/lexa/linux/scripts/Makefile.build obj=/home/lexa/module/build_arm/module1/module1 make -f /home/lexa/linux/scripts/Makefile.build obj=/home/lexa/module/build_arm/module1/module1/module1 make -f /home/lexa/linux/scripts/Makefile.build obj=/home/lexa/module/build_arm/module1/module1/module1/module1 make -f /home/lexa/linux/scripts/Makefile.build obj=/home/lexa/module/build_arm/module1/module1/module1/module1/module1 make -f /home/lexa/linux/scripts/Makefile.build obj=/home/lexa/module/build_arm/module1/module1/module1/module1/module1/module1 make -f /home/lexa/linux/scripts/Makefile.build obj=/home/lexa/module/build_arm/module1/module1/module1/module1/module1/module1/module1 make -f /home/lexa/linux/scripts/Makefile.build obj=/home/lexa/module/build_arm/module1/module1/module1/module1/module1/module1/module1/module1 make -f /home/lexa/linux/scripts/Makefile.build obj=/home/lexa/module/build_arm/module1/module1/module1/module1/module1/module1/module1/module1/module1 make -f /home/lexa/linux/scripts/Makefile.build obj=/home/lexa/module/build_arm/module1/module1/module1/module1/module1/module1/module1/module1/module1/module1 ... and this goes on ... It looks like this happen because in 'src' from command line overrides the 'src' assignment in scripts/Makefile.modbuiltin:5 and then it is not handled when descending the source tree in scripts/Makefile.modbuiltin:53 I was wondering, what is the right way to build the module with separate build directory? -- Kind Regards, Aleksei

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Eudyptual Challenge website and email service down?
by Alexander Kapshuk March 15, 2018

March 15, 2018

Both the Eudyptula Challenge website[1] and the email service[2] seem to be down. [1] http://eudyptula-challenge.org/ [2] little(a)eudyptula-challenge.org The delayed email delivery report I got from Gmail says: Final-Recipient: rfc822; little(a)eudyptula-challenge.org Action: delayed Status: 4.4.1 Diagnostic-Code: smtp; The recipient server did not accept our requests to connect. Learn more at https://support.google.com/mail/answer/7720 [mail.eudyptula-challenge.org. 2600:3c01::f03c:91ff:fe6e:f4bf: timed out] [mail.eudyptula-challenge.org. 23.239.3.192: timed out] Last-Attempt-Date: Wed, 14 Mar 2018 15:24:21 -0700 (PDT) Will-Retry-Until: Fri, 16 Mar 2018 13:18:11 -0700 (PDT) Not sure where else to lodge this report. If the people behind the challenge are subscribed to this mailing list, their response would be much appreciated. Alexander Kapshuk

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