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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What is the appropiate iommu kernel parameter for Ryzen5 1600 and multiple RX580 GPU?

Reserving all the PCIe slot for RX580 prevents my PC to boot, due to such errors AMD-VI IOTLB_INV_TIMEOUT, AER: Corrected error received or kernel panic. Adding the linux parameters with iommu=soft ...
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Reserved RAM: Determine the reason for reserved main memory?

On a server, the linux kernel at boot informs about the RAM setup. It indicates that of the physical 512GiB RAM (536409480kiB), only roughly 503GiB RAM (527942676kiB) are available. root@ada:~# dmesg |...
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unable to download grapical interface in fedora 5.8.15

I don't know how to explain it so here a screen shot. can anyone please help me I want to get this set up. and I tried using other method's but they don't work.
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Asus ROG GL553VW Keyboard Backlight, Fan Control and Keyboard Shortcuts not working

Does anyone know how to setup the keyboard backlight control, fan control and screen brightness keyboard shortcut on the Asus ROG GL553VW for Ubuntu 20.04LTS? I have searched everywhere and I could ...
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Running Xorg won't detect mouse in SUM

So I've been sort of experimenting with the linux kernel lately (with the end goal of making my own distro), and added rw init=/bin/sh to my boot params, to enter this extremely light Single User Mode....
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rfkill: input handler disabled

When I start my Linux system (Debian/stable), I see that the last line of dmesg states: [ 44.043657] rfkill: input handler disabled What does this means ?
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Raspberry Pi 4B - Is Device tree binary dependent on kernel version?

I am trying to get my own custom Linux on a Raspberry Pi 4B. My status is this: I built the Linux 5.9.1 version, and have my own version of U-Boot, RFS with which I am able to successfully load and ...
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Why the hdmi output doesn't work on orange pi one?

I made a small linux distro to use on my projects involving an orange pi one H3, but the HDMI output never works To know if the device was supported by the linux kernel, i tested another distro (...
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“FAILED: load BTF from vmlinux: Unknown error -2make: *** [Makefile:1162: vmlinux] Error 255”, while compiling kernel-5.9.1

I am trying to compile kernel-5.9.1 using make I got the following error while make-ing FAILED: load BTF from vmlinux: Unknown error -2make: *** [Makefile:1162: vmlinux] Error 255 I am using Ubuntu-...
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Should I use IS_ERR_OR_NULL on all kernel functions that return a pointer?

Some functions document that IS_ERR should be used to check for an error. Most functions do not document either way, nor if they can possibly return NULL. Is it appropriate to check all pointer return ...
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How to debug Linux kernel with JTAG + GDB?

I've successfully established a JTAG connection and serial port connection to my development board. I've followed the below diagram (with a little bit of difference). my GDB_client is on my Linux host ...
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Log specific command and send it to specific file with (r)syslog

Is it possible via /etc/syslog.conf to create a rule that log a specific command that user invoke and send it to a specified log file? For example, I want that when users types history -d syslogd ...
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Where to find the syscall_64.tbl in Linux?

I was following this guide to add my own custom system call inside the Linux kernel "Adding a Hello World System Call to Linux Kernel". In Step 5, it asks to modify the system call table by ...
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Unable to locate package linux-headers-5.9.1

I recently installed new Linux Kernel 5.9.1 following steps mentioned on website: https://www.cyberciti.biz/tips/compiling-linux-kernel-26.html Now when I try this command(after reboot): sudo apt-get ...
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NVIDIA 430.09 Not taking Header file for Linux

I have GTX 1650 and I am using Manjaro 64 bit and Kernel 58, but when i try to install Driver 430.09 with this command: sudo ./NVIDIA-Linux-x86_64-430.09.run --kernel-source-path /usr/include/linux/ ...
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Is there any way to force the Linux kernel to ignore O_DIRECT?

Without going into a lot of detail about why I want to do this ... is there any way to force modern Linux kernels to ignore the O_DIRECT flag when opening a file? Basically, I want O_DIRECT treated ...
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where to load vmlinux image on arm64? and how to set the load address?

For arm64, when we compile the kernel, we get vmlinux file. The entry point seems to be 0xffff800010080000 (virtual address ) but where should I load the vmlinux file (I mean physical address) and ...
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How to calculate packet microbursts on a server

I am trying to monitor the number of packets sent/received on 1,10,100ms intervals. This is to help gauging packet microbursts sent by certain high volume publishers. I have tried /proc/net/dev and /...
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Unified Kernel Image Buildroot

Is it possible to create Unified Kernel Image using Buildroot? I want to pack rootfs.cpio.xz and Kernel Image (EFI Stub) into a single file that can be loaded from EFI Shell.
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Can't install any linux flavor due to some firmware issue, [Firmware Bug]: No firmware reserved region can cover this, contact BIOS vendor for fixes

I've been a linux user for the past 5 years.So I don't shy from the cli and troubleshooting issue. It's been a week and when I had tested out a lot of permutation and combinations of what could work ...
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nvmem device tree naming pattern

In the nvmem.yml there is properties: $nodename: pattern: "^(eeprom|efuse|nvram)(@.*|-[0-9a-f])*$" I have a hard time finding the pattern in the source code itself. Where can I find ...
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debootstrap installation kernel mismatch

I tried to install a new Debian 10 system using debootstrap: mount /dev/sda5 /mnt/chroot debootstrap --variant=minbase buster /mnt/chroot ftp.au.debian.org The bootstrap looks good so far. Now ...
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“Invalid magic number, you need to load the kernel first” on an existent and previously working Ubuntu installation

I'm putting this in the general linux stackexchange because I believe it's an issue with grub/my kernel/initramfs. I installed Ubuntu 20.04 on a fresh SSD. This motherboard has other harddrives with, ...
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Linux kernel cannot execute any binary (error -12)

Problem: Memory Allocation Problem my platform: SOC = STM32H743 (ARMv7E-M | Cortex-M7) Board = Waveshare CoreH7XXI Linux Kernel = 5.8.10 (stable 2020-09-17) initial defconfig file = stm32_defconfig ...
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860 views

How many users can be member of a group in Linux Debian 10 x64?

I know Linux has some limitations for the number of groups a user can be part of. I found out that it is 16 groups for each user, and depends on the Linux kernel. However, is there any restriction for ...
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USB Device is going to corrupt state when SetConfiguration is called by application

I am trying to enumerate Android phone with kernel version 4.19 with my application in Ubuntu 18.04,when I call SelectConfiguration of device when in any mode(PTP,Charging ,MTP) results in device ...
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Implementing own system call linux

I got an assignment to implement my own system call and I have to use latest kernal v5.9. Downloaded linux-5.9-rc8(even stable version is giving same error) and extracted. Then cd into this directory. ...
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Custom User-Agent String for Meta-WPE

I am running meta-wpe in my custom Yocto image. I am trying to access Netflix through the browser. I can easily open the Netflix login page but when I try to enter my username and password, it gives &...
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Ethernet ports not working after re-applying AC power

I have a device which runs yocto embedded system. The device has Super Capacitors(supercap) to provide few mins backup when AC power supply is abruptly pulled off. Please note when device is on ...
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linux-5.8.13 kernel struck at Loading Initial Ramdisk screen

I have legion y540. I am using Ubuntu 20.04. Downloaded the latest stable release which was linux-5.8.13 and installed on my Laptop. When i tried to boot this Kernel, i only see two messages on screen ...
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How to access the I/O bits of PCI printer card?

How can I have a direct access to I/O pins of parallel port of the above PCI card from user context under Linux? Output of lspci: lspci -vvvxxxs 03:06.0 03:06.0 Serial controller: TXIC Device 5073 (...
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Read MAC using Buildroot 20.20 NVMEM_IMX_OCOTP on i.MX7s

We are migrating from Buildroot 2018.02.9 (linux-4.14.85) to Buildroot 2020.02.2 (linux-5.4.40), and have found that we can no longer read the MAC address on an I.MX7s SoC. The following indicates why:...
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General Protection Fault on Reboot

I see a General Protection Fault during a reboot after running H/W failure test followed by a reboot. There are no issues with the H/W and test case, coz the same works well the previous RHEL version. ...
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RAID call traces on RHEL8

I am seeing "Call Traces" on booting from Rhel * (4.18.0-235.el8.x86_64). The call traces appears after cold boot. I don't see any other issues. It is known issue I see a thread stuck at the ...
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How can an application compiled for a particular Linux version be run on any version, when there is no ABI compatibility guaranteed?

Let us say, an application - JDK, which is compiled against certain the linux version - say 4.18, available for the download. How can the same application can be run on different linux version - say 3....
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How does a new process executed in Bash always has the same environment variables?

A while ago I was exploring a simple C program's ELF binary using GDB. I saw that the environment variables that are printed when I run printenv in the terminal are also present at the top of the ...
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If I try to install any of 5.8.* new kernels, an error shows up: “ERROR (dkms apport): kernel package linux-headers-5.8.*-generic is not supported”

I'm in PopOS. If I try to install any of 5.8.* new kernels, an error shows up: "ERROR (dkms apport): kernel package linux-headers-5.8.-generic is not supported". I have this problem with ALL ...
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can read system call experience short count after it is interrupted by a signal?

Let's say I call read to read 1000 bytes, and when read is reading the 501th bytes then a signal interrupts it, so does read return 500?
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Ubuntu Core/Debian Compiling for MT2712

I want to build latest kernel of Ubuntu core or Debian for MT2712 but I cannot find any ways to compile the Debian or Ubuntu for this. Is MT2712 supported by Ubuntu or Debian? Can anyone guide me ...
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Is it safe to restart system calls?

I was reading a textbook which describes how to deal with system call when interrupted: System calls can be interrupted. System calls such as read, wait, and accept that can potentially block the ...
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Why does a 2-socket server show PCIe locations but the 4-socket server does not (how can I find the PCIe locations on the 4-socket server)?

I have two servers: 2 socket Supermicro X9DBL-3F 4 socket Supermicro X10QBI When I run hwloc-ls for the 2-socket server I see the PCIe topology with the HostBridges on each NUMANode, but the 4-...
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Is there a linux kernel config, which can detect kernel memory corruption

Looking for some tools for debugging kernel memory corruption by klm's in the linux. Any kernel config which can be enabled to detect stack and heap corruption in kernel space. Any open source ...
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How do I get the linux kernel to track io stats to a block device I create in a loadable module?

I've been looking and looking and everybody explains the /proc/diskstats file, but nobody seems to explain where that data comes from. I found this comment: Just remember that /proc/diskstats is ...
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How does simple segregated storage pre-allocate lists of fixed block sizes?

I'm learning dynamic memory allocation, and still a little bit confusing with some details. We know that s segregated storage, is to maintain multiple free lists, where each list holds blocks that are ...
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does using free() on a block always drop the mappings between its virtual memory and physical memory?

Let's say we want to allocate a block from the heap by using malloc. When allocating a a large size of memory, malloc calls mmap internally and for a small size allocation, malloc calls brk internally....
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malloc doesn't allocate contiguous virtual memory in the heap?

I realize that malloc calls mmap internally and pass NULL as the first argument to mmap so that the kernel will choose a suitable virtual address for the mapping, which means malloc will not ...
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1answer
39 views

how brk pointer grow after calling malloc

I'm new to Linux and C, just want to ask how brk pointer grow after calling malloc. We know that the kernel maintains a brk pointer that points to the top of the heap. let's say there is no available ...
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1answer
19 views

does vm_area_struct change when calling malloc?

I was reading a textbook which talks about Linux Virtual Memory Areas we can see that a vm_area_struct is related to an area in virtual memory, vm_start and vm_end points to the beginning and end of ...
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1answer
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mce: hardware error cpu 0 machine check 0 bank 0. System just freezes, everything just stops including mouse on Linux Mint XFCE 20

My system was working fine but after the changes in past two days I started getting this problem. ​ The Changes I made: I added a 2GB 800mgz RAM stick and replaced my old HDD with a new SSD two days ...
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/sys/class/net/ and ConditionPathExists in Linux service file

I am working on a requirement where the SNORT should run as a daemon on Wi-Fi wlan0 interface. This is taken care as a system file. The snort command is written in a script file and the Snort service ...

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