Questions tagged [linux-kernel]

Questions about Linux kernel and Linux kernel related topics eg. implementation details such as system calls, kernel customization, etc. For Linux user space topics which do not involve kernel details, [linux] or distribution tag are more suitable.

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658 views

Battery drains while powered off after upgrade to kernel 4.13

After upgrading to kernel 4.13, the battery of my laptop started to drain while powered off (about 30% in one day). This didn't happen if I booted the laptop from kernel 4.12 or Windows 8.1, so the ...
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1answer
5k views

NVMe PCIe disk power cycling

I want to test a NVMe SSD that is connected to a PCIe slot of my motherboard. The test procedure is a specific algorithm that writes workloads to the SSD, while the SSD is exposed to radiations (e.g. ...
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509 views

What network connections are not seen by netstat/lsof/ss?

Network monitoring tools ss, lsof -i, netstat -ltupw and similar have limitations like namespace and thus they don't show the whole machine connections. (for namespace created with ip we can see other ...
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How to read the output of the show-memory-usage SysRq?

I couldn’t find any (recent) documentation on reading the output of the show-memory-usage SysRq (Alt+SysRq+m). So what can one learn from looking at it? Here is an example output form my box (Kernel ...
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Why are block sizes limited by page size in Linux?

In many (all?) file systems that Linux uses, including ext2/3/4, the maximum block size is the page size of the architecture Linux is running on, ie. 4KiB on x86. Why is there this limit? Might this ...
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518 views

How to combine linux kernel and initrd without compiling?

I know that it's possible to extract from a linux kernel the embedded initramfs cpio. I want to know if the reverse operation is possible; i.e., given both a compiled kernel and initramfs archive, how ...
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2k views

Can't run any snap using linux 4.12 : snap-confine has elevated permissions and is not confined but should be

I am using Ubuntu 17.04 with linux kernel 4.12.2 which I installed using the software ukuu (Ubuntu Update Kernel Utility). Every time I try to run a snap in my system when I am using this linux ...
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136 views

Kernel config for keyboard special LEDs

I'm building a 4.9 linux kernel (which is working great) for my T460s. The F1 key has a led that shows if sound is muted. I can't get this LED to work even when enabling all kinds of LED-relevant ...
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4k views

Linux 3.x fails assigning PCI BAR memory

I got an IBM x3850 type 8864 machine, I can successfully boot using a 2.6.32 kernel but when I try to use a 3.10 kernel or newer the kernel fails to initialize all PCI slots (I can fix this (manually),...
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896 views

Print kernel memory layout

Userland memory layout can be inspected by looking into /proc/self/maps. I am wondering if there is a similar facility allowing to inspect runtime kernel memory layout?
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123 views

Kernel config diffs - better way to maintain

I maintain one Linux distro (LEAF) with multiple kernel targets, so it needs to have multiple kernel configs (one reference config + usual patch files for other targets). But this adds headache on ...
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6k views

How to create Linux Kernel Headers from Linux Kernel Source?

I'm working with Tiny Core Linux and attempting to install Vmware Tools, which of course needs the Kernel Headers :-). It does not appear they have the Kernel Headers readily available in a package, ...
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How to prevent kernel or any broadcast messages from flooding the TTYs?

Because of some hot-plugging issue, similar to what talked of here, the TTY displays show a continuous stream of messages (which are also logged in the /var/log directory). Every text I key in flows ...
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2answers
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Problem when trying to cross-compile an ethernet driver on an old Linux kernel

I'm currently trying to cross-compile a network driver against an old Linux kernel, in version 2.6.27.7 but the compilation fails and prints: make[1]: entering directory « /home/johann/Desktop/linux-...
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1answer
801 views

How are Linux kernel bugs being tracked?

What an hour of Googling bring out that mainstream Linux kernel bugs are being logged in two distinct systems: Mailing list This is the Linux kernel development discussion and bug reporting ...
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1answer
62 views

Kernel Panic not showing up?

I'm writing a kernel module and I was hoping to get the beautiful Kernel Panic screen with all the details when I call panic(), but my machine just freezes without displaying anything. I know kpanic ...
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1k views

Kernel compiling - Error during sync of the configuration

I am trying to compile the 4.19 kernel on my Linux Mint machine. I copied my current config (which is from 4.15), opened make menuconfig in order to append a local version string, saved it and then ...
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0answers
126 views

What is the modern way to develop a Linux auditing kernel module?

I'm new to Linux Kernel development, and I am now assigned a task to develop a Linux kernel module, which can monitor the network, filesystem, USB and serial ports. I am aware of the things like ...
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0answers
616 views

CPU high load native_queued_spin_lock

I'm using Debian 9(stretch edition) kernel 4.9., hp dl385 g7 server with 32 cpu cores. NIC queues are tied to processor cores. Server is shaping traffic (iproute2 and htb discipline + skbinfo + ipset +...
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1answer
1k views

How can I detect whether an “NMI watchdog: BUG: soft lockup” is a hardware or a software issue?

Soft Lockup dmesg reports in my laptop, since quite some time now, NMI watchdog: BUG: soft lockup every time I try to use updatedb or firefox. Samples of what is reported posted at https://github.com/...
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0answers
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Dell XPS 13 9350 wifi dying with Broadcom BCM4350 and 4.8 kernel

Launchpad report: for all those with the same problem, please subscribe to this report I opened in Launchpad so that it can gain some traction. I've been using Ubuntu 16.04 with kernel 4.7 for some ...
4
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1answer
201 views

Are devices with kernels below 3.6 vulnerable to CVE-2016-5696?

Today I was reading about the potential impact of CVE-2016-5696 in Android phones running Linux 3.6+ and though my phone has 3.4 I checked the value of net.ipv4.tcp_challenge_ack_limit and it is also ...
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Centos 7 boot up with custom kernel problem

I have installed centos 7 on virtualbox machine which has kernel-3.10.0-123.20.1.el7.x86_64. I am trying to build Linux kernel from kernel sources. I downloaded the kernel source files from: http://...
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2k views

update kernel without restart

Recently Linux got a new feature called Live Kernel Patching, which you means you don't have to restart your system to update kernel. Is there any other kernel which has this feature already or Linux ...
4
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1answer
287 views

kernel: nf_conntrack: table full, dropping packet; Underlying Reason

I have a modified linux on an ARM9 processor. It was working OK, but yesterday I got this error repeatedly: kernel: nf_conntrack: table full, dropping packet I have 2 questions: How can I find out ...
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0answers
4k views

How to create the framebuffer file node?

I'm working with a limited embedded device - Linux environment - that uses a custom DirectFB implementation to draw a user interface in its video output. I would like to exchange this method by a raw ...
4
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1answer
3k views

DisplayPort and Intel HD cause GPU hangs

My system has problems with the displayport connection. This is indicated by several problems that, at the first glance, do not have anything in common. The reason why I claim DP for being the cause, ...
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0answers
900 views

EDID Invalid on USB DisplayLink Device

I have a Sabrent USB to HDMI adapter which is a DisplayLink device. It's recognized by udl as being a DisplayLink device, yet seems to be rejected/disabled due to having an invalid EDID: [32780....
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1answer
370 views

what is the linux boot param “memmap” equivalent in freebsd

In linux kernel, there is an option to reserve a portion of system ram i.e memmap=512M$2G (boot param) Here 512M starting from 2G would be reserved and not available to OS What is the equivalent in ...
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2k views

Kernel does not detect Hardware / Software or Hardware fault

My Linux kernel (I tried several here from stock 2.6, 3.2 and 3.5 as well as a custom 3.7.3 one) does not detect my synaptics touchpad - or I am too dumb to find it. I looked into: dmesg, lsusb -v, ...
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1answer
3k views

CentOS 7 unable to cleanly umount a bind mount using rbind and rslave

The following sequence of commands will fail on CentOS 7 (kernel version: 3.10.0-327.10.1.el7.x86_64): [hidden]$ mkdir -p A B/a C/b [hidden]$ sudo mount --bind A B/a [hidden]$ sudo mount --rbind B C/...
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0answers
46 views

udev rule not worknig as expected with PROGRAM key

My system is Debian Buster with Kernel 4.19. I have a simple udev rule as below that was working fine with Debian Jessie. Now same rule seems to be not working in newer distribution. KERNEL=="sd[a-z]...
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0answers
121 views

How can I display graphics on the screen from the kernel over the top of my X11/Wayland session?

I want to draw simple (2D bitmapped) graphics onto my screen (in response to (simple) external inputs) with the lowest latency possible (the order of tens of milliseconds) so I can empirically test ...
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0answers
348 views

Docker service causes 100% CPU usage

Recently, my CPU has been adopting a very strange behavior. I noticed a strong slowdown when running my typical setup, which includes around 20 docker services. It feels like my laptop became unable ...
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0answers
199 views

Is there any tool to generate kernel .config file?

I watched a clip on customizing kernel, rebuilding, installing, etc. where the gentleman suggested to use an existing .config file with make menuconfig or make xconfig. I wanted to use one that comes ...
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121 views

How does linux decide the load address and entry point when execve an ELF?

When linux execve() an ELF, it will mmap that ELF into the process's memory space and start to run code from the entry point. But how does the kernel decide the load address and entry point of the ELF?...
3
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1answer
466 views

How to check if If i2c-hid and hid-rmi are not used for touchpad?

I'm seeing the following warning in dmesg: [ 2.631179] psmouse serio2: synaptics: Your touchpad (PNP: SYN1218 PNP0f13) says it can support a different bus. If i2c-hid and hid-rmi are not used, you ...
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0answers
362 views

overall HIGH CPU utilization, but top is not showing process which is contributing to that spike

Below is the output of a top command, which is showing "57.6%us, 24.0%sy" overall cpu utilization at a particular moment, but there is no process which is contributing to this spike of cpu usage. ...
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0answers
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Is linux mount propagation asynchronous to the mount call?

I have two processes in different mount namespaces. They have a shared directory bind mounted to /mnt/share. The "master" uses MS_SHARED propagation for the mount, while the "slave" uses MS_SLAVE. ...
3
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1answer
280 views

How are cpu.cfs_ period_us defined in cgroups and kernel.sched_cfs_bandwidth_slice_us related?

I've been trying to understand how the Completely Fair Scheduler in the Linux kernel does CPU bandwidth control. After many readings, I still cannot understand how the CFS allows for each cgroup to ...
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0answers
97 views

kernel 2.6.35.3 - how to convert .config to defconfig

If you have newer kernel (i.e. > 2.6.35.3) you can create a 'defconfig' from a '.config' by using make savedefconfig But in kernel 2.6.35.3 - does not provide you with 'savedefconfig' target. How ...
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0answers
195 views

kexec: relocate_kernel fails

I am not able to get kexec to work. For x86_64 relocate_kernel fails to store information for jumping back. Kexec stops in movq %r9, CP_PA_TABLE_PAGE(%r11). works fine for kernel 4.4.162, doesn't ...
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0answers
2k views

Kernel BUG: unable to handle kernel paging request

So I'm trying to run this kernel module on my laptop, and every time I do so, I get a stack trace that looks like this (all the messages might not be relevant to the module). [17539.035247] EBBChar: ...
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0answers
114 views

How do I upstream a patch into the Linux kernel developed by someone else?

I've recently been trying to upstream part of the Nintendo Switch-on-Linux patchset, but it appears that the original developer must sign off on each commit. Do I need to ask the original developers ...
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0answers
352 views

Time measurment in Linux kernel: how are clock_gettime, gettimeofday and getrusage related?

I am trying to understand how time is measured by the Linux kernel. I tried to go through the kernel code, but I miss the big picture to understand the code that I'm reading, even if this article ...
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52 views

What is the maximum processor frequency that Linux could run on?

Theoretically, if an extremely fast computer could be built (100s of GHz or even terahertz), what is the maximum frequency that could be expressed in the variable used by the scheduler allocate cycles?...
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0answers
55 views

Which Linux kernels include a particular bug fix?

How do I know which Linux kernels have merged a particular bug fix? For example, as mentioned in this question: Kernel Bug 198357 - iwlwifi: failed to remove key (1, ff:ff:ff:ff:ff:ff) from hardware ...
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0answers
469 views

Loading a kernel module at run time using “compatible” property of device node in device-tree

If I know the "compatible" property string of a device(from the device tree), can I use it at runtime to load the corresponding kernel driver module? I do not have access to the driver source. I am ...
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0answers
702 views

Hooking sys_execve on Linux kernel 4.6 or higher

Kernels lower than 4.6 use assembly stubs to harden the hooking of critical system calls like fork, clone, exec etc. Particularly speaking for execve, the following snippet from Kernel-4.5 shows entry ...
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0answers
1k views

Finding which specific Python process was killed by Linux OOM killer

I'm trying to figure out which specific Python process or executable was killed by the Linux OOM killer. In /var/log/messages I get this: Aug 18 03:19:11 169 kernel: [ 7747] 0 7748 3226957 ...

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