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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Cumulative linux kernel changelogs?

You know how it goes when you build your own kernels but not as your main occupation... By the time you realise some new quirk could be due to a kernel regression, there have already been more than a ...
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What is rootfs and how to create it from scratch?

I'm new to embedded linux and recently I compiled u-boot and linux kernel for stm32H7 (32bit cortex m7 without MMU/Virtual-memory) and successfully started the kernel but the kernel panics and says ...
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Is it possible to add component to an installed kernel?

I am trying to troubleshoot kernel panics on my HummingBoard, Debian machine, running the manufacturer supplied image. I have found what seems to be an appropriate tutorial (https://www.linuxjournal....
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How to read session history currently in memory (the history that eventually gets written to “.bash_history” upon logout

I've encountered this issue several times where I need to access the history of a currently active session. Unless there is an easier way, I'm about to write a C program to read this from a target ...
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Can a mprotect() call lead to priority inheritance in Linux scheduling?

Is it possible, that a call of mprotect() in Linux can lead to priority inheritance? When analyzing an ftrace file, I see a call of mprotect() by Task 1 followed by a priority inheritance. Task 2 gets ...
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Intel wireless card AX200 5g AP mode worked then failed

I have two intel wireless card, one of them is AX200. I didn't know intel disabled all 5g ap mode before buying it. The reason I want to use a wireless card for ap is I want to test how many ...
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104 views

Keyboard Not Working With Recent Kernels?

The issue is pretty well summarised by the title; one day my computer crashed and when it came back the built-in keyboard and mouse didn't work until I used the grub menu to change to an older Kernel. ...
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Why does disabling Kernel Page Table Isolation decrease MemTotal?

Iso kernel (Linux 5.4.60), Iso hardware, Iso config apart from case A: CONFIG_PAGE_TABLE_ISOLATION=y and, case B: CONFIG_PAGE_TABLE_ISOLATION=n iomem reports an identical map (apart from Kernel code ...
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System too busy for magic SysRq [duplicate]

Sometimes (perhaps once a month) my system stops responding so bad that it won't react to magic SysRq combinations (which are allowed and do work properly at all other times). I'm quite sure this is ...
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274 views

u-boot stuck at Starting Kernel

My Target Setup: SOC: STM32H743 (Cortex m7 single core) Internal Flash: 2MB Board: Waveshare CoreH7XXI On-board DRAM: 8MB, Start_Address: 0xd0000000, Size_in_bytes: 0x7A1200 SDCARD: 1GB Bootloader: ...
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Linux Security Best practice: CAP_SETFCAP vs sudoer file

I am new to linux securities and tried to understand what's the best practice for linux capabilities. Here is my scenario: I have an executable file (let's call it foo) which needs to grant ...
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How do I create a compressed buildroot system image that expands to fill the available storage of the media it is flashed to?

I need to make a Buildroot system for various x86_64 EFI systems with varying storage sizes, but unfortunately, the pc_x86_64_efi config creates an img file with a fixed partition size, not one that ...
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Fluke Etherscope stuck at loading kernel, Have JTAG Pins, and bootloader access

I had purchased two Fluke Etherscopes, these are stuck with the message 'Loading Kernel' on the screen. I was able to get a serial console, and access the bootloader using the serial port on the side ...
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How is overflow_stack variable included in entry.S in arm64 architecture?

The overflow_stack variable is used in the kernel_ventry macro in arch/arm64/kernel/entry.S /* Switch to the overflow stack */ adr_this_cpu sp, overflow_stack + OVERFLOW_STACK_SIZE, x0 It ...
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198 views

Fedora 32 stuck at boot screen with kernel 5.8.4

There is 3 kernel version in my Fedora 32 based desktop: 5.7.15, 5.7.16 and 5.8.4 At the time when I was using 5.7.16, I've installed and configured to work with docker, virtualbox and nvidia driver. ...
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137 views

Error! Your kernel headers for kernel 5.8.0-rc3-microsoft-standard cannot be found while trying to install usb_network_gate on WSL2

I'm trying to install usb network gate on ubuntu 20.04 on WSL2 with this kernel version installed on : root@DESKTOP-N9UN2H3:~/Desktop# uname -a Linux DESKTOP-N9UN2H3 5.8.0-rc3-microsoft-standard #2 ...
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67 views

Why does make oldconfig not work with a bash function?

I have the following function in my bashrc: make() { nice -n 19 /usr/bin/make -j $(nproc) --output-sync "$@" echo -e "\a" } export -f make The purpose is to run make on ...
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Problems creating a socket with NUMA

Add a command in QEMU v5.1.0 from the console to create a socket, I make it and even in properties it says it is a socket, without size, without problems, but now I am trying to do the same but, with ...
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1k views

Ubuntu 20.04.01 not booting after kernel update

I just updated my PC that is running the latest version of Ubuntu (20.04.01). I made a system update and that update included also a kernel update (from kernel 5.4.0-42-generic to 5.4.0-45-generic). ...
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How to get reports from kswapd, like, why it was triggered, what it did with what results?

Is there a way to obtain information about kswapd operation, that is: a) what was the reason it was triggered, b) what did it actually do and c) what were the results of its operation? Background: ...
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35 views

Filesystem for exposing all registers for linux subsystems

I want to implement the filesystem similar to sysfs or use the sysfs filesystem and add more entries with values of registers which are sub-system protocol specific, for this, I want the opinion of ...
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Configure LCD in Linux kernel to load specific LCD on boot

I have an LCD with its module board connected to my core4418 friendlyARM(embedded). This LCD is connected via a flat (ribbon) cable and not HDMI. When my Linux boots, dmeasg | grep lcd shows this: ...
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169 views

“ERROR: device UUID=”xxx“ not found” on boot after switchg to linux-lts kernel on Arch Linux

ERROR: device UUID="xxx" not found. Skipping fsck. mount: /new_chroot: can't find UUID="xxx". This issue happened after I tried to switch from linux to linux-lts kernel. I did ...
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gpio pins state does not persist on reboot

I am trying to set gpio pins 33 and 116 to low but on reboot it switches back to high. Can someone suggest how I can make the pin values to persist after reboot? Here is how I tried to make gpio pins ...
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Open Network Linux (ONL): change version busybox

I have a question that needs your help: Why when I add busybox to all-base-packages.yml file and build ONL, it only downloads and builds each version 1.22.0-9+deb8u1, and how can I change it to other ...
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1answer
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KSM / MADVISE : Init & usage in standard desktop environment

Running a 4.19 linux kernel + couple of patches RT oriented + occasionally running a couple of processes SCHED_RR (for "pro"-audio purposes) CONFIG_KSM set in the kernel and ksmd running, I ...
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130 views

Build the Linux kernel without gcc optimization

I follow one of many tutorials found on Google results to build and debug the Linux kernel with gcc and kgdb/gdb. And I end up by discovering that is all waste of time. Since I can't compile the ...
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321 views

arch linux systemd boot: missing /vmzlinuz-linux and /initramfs-linux.img

I am arch linux. One day it stopped showing in systemd boot menu. So I booted live arch via usb, mounted bootloader partition and ran bootctl list --esp-path="/mnt". This is output: title: ...
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68 views

Is kernel.keys.maxkeys per user or per key?

The Linux kernel's documentation on its Key Retention Service states that: /proc/sys/kernel/keys/maxkeys /proc/sys/kernel/keys/maxbytes These files hold the maximum number of keys that each non-root ...
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Are kernels on the individual machines also in action when multiple users are logged into a common system via a server

In a book on Unix, I read the following lines: Even though there's only one kernel running on the system, there could be several shells in action - one for each user who is logged in. My question is - ...
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Murata WiFi- BT Module porting in imx6 running ubuntu

I have done porting for Quectel 4G Module on my linux kernal. Now, I am trying to do the porting for murata wifi-bt module using cypress brcmfmac driver. I am using linux kernal 4.1.15 I am booting ...
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1answer
48 views

In 64-bit linux kernel, how much memory is contiguously mapped by the kernel?

I have gone through Robert Love's Linux Kernel Development, and other sources. And everywhere it mentions that on a 32 bit x86 system the kernel owns the top 1 GB of the virtual address space, out of ...
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37 views

IOMMU support confusion / confirmation

this is kinda tech newbie formatted question but i hope someone understands me. so i'm following along https://wiki.archlinux.org/index.php/PCI_passthrough_via_OVMF#Setting_up_IOMMU for protection and ...
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51 views

Is there any way to make older Linux kernel modules work?

I have a wireless adapter that needs a proprietary driver. But the manufacturer has discontinued this device for about 7 years ago. As the code is very old and was written for Linux 2.6.0.0, it doesn'...
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1answer
53 views

Multicast route not linking to userspace

Ok So I have a user space application that needs to get data from multicast traffic, however I cannot seem to get the traffic out of kernel space and into userspace where the application can utilize ...
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2answers
180 views

Why Linux module API isn't backward compatible?

Why isn't the Linux module API backward compatible? I'm frustrated to find updated drivers after updating the Linux kernel. I have a wireless adapter that needs a proprietary driver, but the ...
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2answers
138 views

Is it possible for a kernel space thread or process to be child of a userspace process?

I am kind of a newbie when it comes to the Linux Kernel, but I was reading this article about fibrils where it mentions that they are (or were? not sure if they were ultimately kept in the Kernel) ...
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1answer
35 views

multiple target patterns” Makefile error in Ubuntu 16.04

I am trying to build the linux kernel for arm based i.mx6 board. I have following these steps for building linux kernel 1.export ARCH=arm 2.export CROSS_COMPILE=/media/cascademic-101/D:/alam/...
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1answer
84 views

Compiling kernel from source got a fatal error: too few arguments to function 'part_round_stats'

I'm trying to compile the kernel from source on the system CentOS 7. The output of uname -a is: Linux dbn03 3.10.0-957.el7.x86_64 #1 SMP Thu Oct 4 20:48:51 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux Here ...
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Black screen with only cursor AFTER LOGIN on braswell and cherrytrail with Linux 5.7 (i915)

I've built the current 5.7.14 kernel and am running into an issue on my Brasswel (N3150) and CherryTrail (Atom x5-Z8350) systems. The former runs an old Ubuntu 14.04.6LTS system, the latter runs ...
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Does Linux kernel allocate free TCP port based on IP address?

This is a hypothetical question, just to help me understand more about how TCP ports work. Suppose I have multiple Ethernet cards on my machine and they are attached to different subnets. Now if I ...
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1answer
219 views

iptables -p with protocols other than tcp/udp

As per my understanding iptables work on transport layer (layer 4) and any packet filtering that happens is based on the ip protocols for layer 4 like tcp and udp. So if we enter protocols like esp, ...
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230 views

Building a custom kernel in Debian

I am not a Debian user, but I need a Debian environment to test this kernel patch I've written, needless to say I've spent the last couple days trying to figure out how to build a custom kernel on ...
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1answer
47 views

Why is there kernel stack for each process in linux?

Recently, I started learning about linux and there is a series of question, I am going to ask. While reading, I encountered a term 'kernel stack' and I am not able to understand why does the linux ...
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2answers
69 views

Linux almost stock 4.19.133 suspend fails, works fine with Devuan's 4.19.0-9 kernel

I have a long habit of building my own kernels (from time to time), using the stock sources with just the ConKolivas patches, -O3 instead of -O2 optimisation where I can set it, and targetting the ...
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80 views

Touchpad not working after kernel upgrade

I am on Gentoo currently. I decided today to give the 5.8rc-7 kernel a go. I configured and compiled it. After reboot, however, my touchpad was not working. So I configured and compiled again, this ...
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1answer
824 views

What is the Zen kernel?

I recently stumbled upon the zen kernel on the Arch wiki, but neither the wiki nor the Github page says anything more. What is it? Is its performance really better?
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1answer
72 views

How does the i2c subsystem match devices against drivers?

My understanding of this is fairly minimal so bear with me. From what I gather so far, the i2c subsystem on Linux identifies devices that are attached, and then matches them against loaded driver ...
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23 views

Kernel module compile against overwritten dependencies

So, I have installed a driver/kernel module for a wifi module from Laird. It works well but I noticed that it also install a kernel module named cfg80211 which is overwrite the existing kernel module. ...
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51 views

Submitting Linux kernel code

As a semester project I have modified a file of Linux kernel source code (related to memory management), to improve the existing structure. It includes addition of some new functions. But I couldn't ...

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