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Questions tagged [kernel]

Everything about Unix kernels: development, configuration, compilation, design, etc.

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Highly suspicious System.Map (5.14.21-150500.55.68) - Linux compromised?

I'm running the 5.14.21-150500.55.68 x86_64 kernel on OpenSuSe Leap 15.5. I have over 20 years of experience with many different distros, but I always come back to OpenSuSe for several reasons. I have ...
new_sec_from_scratch's user avatar
0 votes
1 answer
29 views

How to create a page aligned variable in a kernel module?

So I want to have a buffer in my kernel module that I created like that: static char buf[BUF_LEN]; My problem is that the start address of this buffer is not necessarily page aligned. To give a bit ...
Pinko's user avatar
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-2 votes
1 answer
38 views

What important side effects causes on a RHEL system to disable user namespaces?

In order to mitigate a CVE issue I have on a list of servers, I came across this link from RHEL. Under the mitigation steps, there are two options, one is to blacklist a nfs_tables kernel module which ...
VaTo's user avatar
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2 votes
1 answer
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Oracle Linux Kernel cannot be set after OS upgrade

we have two physical machines running Oracle Linux and I was tasked to upgrade them from OL 7.9 to 8.10. I already did this on the 5 OL VMs we have and it worked fine. The upgrade on the first ...
Jonas's user avatar
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Does linux/drivers/hid/hid-roccat-lua.c control the lights of the mouse?

If you look linux/drivers/hid/hid-roccat-lua.c, it has a comment towards the beginning, /* * Roccat Lua is a gamer mouse which cpi, button and light settings can be * configured. */ from which I'd ...
Enlico's user avatar
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1 vote
0 answers
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I am following a video on setting up Qemu/KVM. Setting up of tuned, I am having a problem with missing parameters. How can I correct these errors?

In setting up Qemu and KVM: I received the following notification.  I have seen several others with this same problem, but I have not been able to find a post with a resolution to implement. $ sudo ...
fb0034's user avatar
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6 votes
1 answer
469 views

How can I confirm for sure that a CVE has been mitigated on a RHEL system?

I have this problem, I'm trying to see if a group of servers are vulnerable to the CVE CVE-2024-1086 so what I do in the server is rpm -qa --changelog kernel | grep 2024-1086, and I get this as output:...
VaTo's user avatar
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-1 votes
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Embedded kernel hit OOM. It's a storage offload card running storage software. Need RCA fro OOM with below logs

Apr 4 07:24:04 captain user.warn kernel: ncd invoked oom-killer: gfp_mask=0x200da, order=0, oom_score_adj=0 ... Apr 4 07:24:05 captain user.warn kernel: active_anon:16415 inactive_anon:108 ...
nisarga lolage's user avatar
3 votes
0 answers
44 views

Linux clock source from FPGA

I'm trying to get the Linux kernel (and system as a whole) to sync to a monotonically incrementing clock from a FPGA register in memory. The clock is 64-bits wide and divided into two 32-bit sections: ...
Ryan Sherlock's user avatar
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Has the log added by SYSCALL_DEFINE4 not been printed to the debug serial port?

The Linux system I customized sometimes cannot be restarted when using the reboot command, so I added printing to both the busybox and kernel. When I use the serial port to check the logs of the ...
just a student's user avatar
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52 views

Why it takes 7 seconds to reserve ~200GB of huge pages at boot?

I have a server with 300G of RAM and I'm preallocating ~192G of it as huge pages by passing hugepagesz=1G hugepages=192 args to kernel command line. As a result, I see these lines in dmesg: [ 1....
Sergei Dyshel's user avatar
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0 answers
43 views

Linux Redhat9: kernel warnings: user: probe of wq1.0 failed with error -95

I have linux Redhat 9 on intel x64 machine and I see following warnings during boot in dmesg: user: probe of wq1.0 failed with error -95 user: probe of wq1.1 failed with error -95 user: probe of wq1....
Cedric's user avatar
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1 answer
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Why the access to /proc/[pid]/ns needs to generate symlinks?

The directories of the form /proc/[pid]/ns get populated each time they are accessed. That is, each time they are accessed the kernel produces a symlink to somewhere in the namespace filesystem (not ...
caciquekampeon's user avatar
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0 answers
41 views

Linux From Scratch 12.1 GCC testsuite failing and timing out

I'm currently building Linux From Scratch 12.1 with the book, I've followed the instructions line by line. I'm struggling with the GCC testsuite, I have lots of FAIL and timeout. In addition to that, ...
noxen's user avatar
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Hang after S3 resume - Bluetooth: hci0: Opcode 0xfc1e failed: -16

I have an MSI board with built in Intel AX200 BT and Wifi. This is on kernel: iwlwifi 0000:29:00.0: loaded firmware version 77.ad46c98b.0 cc-a0-77.ucode op_mode iwlmvm After successfully booting ...
densub's user avatar
  • 1
0 votes
1 answer
47 views

since page table is needed to translate virtual address, how could linux kernel access and manipulate page table itself with virtual address?

According to my current understanding: there's kernel code that access or manipulate page table In kernel code, it's also virtual address used to access any struct or object, including page table ...
Qiu Yangfan's user avatar
0 votes
1 answer
31 views

New added android kernel bpf helpers are not detected

I'm trying to patch an android kernel 4.9 to support probe_read_{user, kernel} and probe_read_{user, kernel} helpers. For the backporting I took example from another patch that adds bpf_probe_read_str ...
Marcel's user avatar
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0 answers
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Problem adding onnxruntime python package to a yocto build

I'm trying to add the meta-st-x-linux-ai to my yocto build setup so that I can have the onnxruntime python package available on my linux, but I get the following errors : Notice that all my layers ...
SADALI Mohand's user avatar
1 vote
0 answers
76 views

How to isolate cpu cores, even from kernel space, at boot?

I have a faulty Ryzen 5900X desktop CPU. Previously, I somewhat tamed its faulty cores via isolcpus=2,3,14,15 kernel parameter in GRUB2 (see https://blog.cbugk.com/post/ryzen-5850x/). However, on ...
cbugk's user avatar
  • 446
0 votes
1 answer
126 views

AH00141: Could not initialize random number generator

I tried to upgrade my debian system from buster to bullseye and messed up everything. I cant start apache2 and proftpd. When I do apachectl configtest I get the following error message: (38)Function ...
Anarkie's user avatar
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1 answer
33 views

How does the kernel understand that a specific module file belongs to a certain type and should be in a certain directory?

Kernel module files are located in directories such as /lib/modules/drivers/ /lib/modules/storage/ /lib/modules/fs/ they all have the extension .ko but how does the kernel understand that a specific ...
Besha's user avatar
  • 135
0 votes
0 answers
30 views

Redirecting traffic from one usb port to another?

Is it possible to use a linux machine as some sort of usb passthrough? In the sense that the linux machine would act as host on one port and gadget on the other. What I am trying to achieve is to ...
Dennis Solomon's user avatar
2 votes
1 answer
63 views

What is the difference between driver name and kernel module name for lshw?

Using lshw to query my WiFi USB adapter shows the following: $ lshw -C network *-network description: Wireless interface physical id: 12 bus info: usb@3:7 ...
jII's user avatar
  • 381
0 votes
0 answers
46 views

Centos 7 Increase CMA Size

I have a SBC module and it has Centos 7 with 3.10.0-1160.114.2.el7.x86_64 kernel version. I have to increase CMA size to 128MB which is default 4MB. I check my kernel menuconfig and DMA Contiguous ...
Alp Er's user avatar
  • 1
0 votes
1 answer
39 views

nixos live usb boot stuck at Probing EDD (edd=off to disable)... ok

When trying to boot from a NixOS live usb with 23.11, gnome for x86_64: On a Asus C236 WSI Motherboard with this BIOS: $ ls -l /sys/class/dmi/id/bios* ...
fschn's user avatar
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0 votes
1 answer
66 views

Resolution stuck at 800x600 after installing Nvidia Drivers

Wanted to install Nvidia Drivers on Fedora 40 so I could write CUDA code. I'm actually going to reference this question because it's very similar; only it was asked 7 years ago but received no answers....
Lobster Roast's user avatar
1 vote
0 answers
257 views

boot issues on kernel 6.5.0.34 in ubuntu 22.04

the most recent kernel version, I have got from canonical is 6.5.0.34. I'm running Ubuntu 22.04.4 LTS on an AMD A6-9225 RADEON R4 laptop. My problem: my machine does not boot any more. it stucks at ...
demonshunter's user avatar
0 votes
0 answers
41 views

OS detects less memory than BIOS

I have OpenBSD 7.5 installed on a Beelink SER5 MAX Mini PC. The product has 16 GiB memory, and the BIOS detects Total Memory: 16384 MB (DDR4). However, OpenBSD top only reports Memory: Real: 169M/...
nalzok's user avatar
  • 401
0 votes
1 answer
65 views

cgroups v2 : io.latency not exists

When I create a cgroup using sudo mkdir /sys/fs/cgroup/my-cgroup, io.latency is not created. Other io files are created, like io.max, io.stat, io.pressure... The content of cgroup.subtree_control ...
Xeway's user avatar
  • 1
1 vote
0 answers
48 views

AM335X setting of RNG

I kindly request any advice regarding the configuration of the HW RNG of TI AM335X. I'm aiming to achieve security certification for our device, which is based on the PLC Wago PFC200 750-8217. One of ...
bpob's user avatar
  • 11
1 vote
2 answers
222 views

Building custom kernel on Ubuntu Jammy

Someone on Reddit showed me this yesterday https://git.kernel.org/pub/scm/linux/kernel/git/westeri/thunderbolt.git/commit/?h=next&id=9a966517a83090ee3e26e9a93a92523e2358c5b3 Looks like I should be ...
NickK's user avatar
  • 11
0 votes
1 answer
54 views

Boot a kernel of debian installer with expert mode

I want to reinstall my VPS with the debian's official repository, instead of with the image provided by the VPS operator(I don't trust the VPS operator). On original system I installed debian-...
Leon's user avatar
  • 163
0 votes
0 answers
22 views

kdump won't save dmesg in CentOS stream 8

I created a CentOS 8 stream machine on aws, and configured crashkernel in grub $ cat /proc/cmdline BOOT_IMAGE=(hd0,msdos1)/boot/vmlinuz-4.18.0-552.el8.x86_64 root=UUID=e52ef623-609b-4202-9b2c-...
daisy's user avatar
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0 votes
0 answers
29 views

Is it possible to read page table in Linux with unprivileged mode?

this is my very first question in Unix & Linux, I'm currently learning about virtual memory. I am appreciating this awesome paper drammer (CCS'16). Where it fools the buddy allocator to allocate a ...
Y.H.Qian's user avatar
-2 votes
2 answers
66 views

Where is 512M RAM from?

In Virtual machine, Kali, I assigned the memory 4G, like this; But there is a problem. I installed self-build kernel at the guest to hack the memory. # uname -a Linux 15ud490-gx76k 6.8.4+ #8 SMP ...
pico's user avatar
  • 93
0 votes
1 answer
37 views

Is it possible to set larger buffers for file access on linux

I have a process thats reading the whole filesystem and hashing files. It slows down (by 4x or so) because the reads are causing a lot of seeking. Small chunks of each file are being read by each of 4 ...
Pete's user avatar
  • 133
6 votes
1 answer
725 views

Does mmap() update the page table after every page fault?

Based on my research on mmap(), I understand that mmap uses demand paging to copy in data to the kernel page cache only when the virtual memory address is touched, through page fault. If we are ...
prajasek's user avatar
0 votes
0 answers
53 views

How to "wake-up" user space threads from kernel?

Suppose you have a kernel device driver receiving data and a user space threads waiting for the data. You want to avoid wasted cycles by having the user space thread block and wake-up once the kernel ...
FourierFlux's user avatar
4 votes
3 answers
6k views

VMware vmmon & vmnet 17.5.1 and Linux kernel 6.8.0 won't compile

After upgrading to kernel 6.8.0, VMware's vmmon and vmnet couldn't compile, giving the following error: ... ... /tmp/vmware-host-modules-w17.5.1/vmmon-only/common/task.c:548:1: warning: no ...
lucasart's user avatar
  • 201
1 vote
1 answer
322 views

cgroup virtual file system is read only for root, when root has write privileges?

As the title of my question suggests, I am trying to edit the properties of my cgroup virtual file system - create new directories, edit the resource limits in certain files, etc - but any write ...
user10709800's user avatar
21 votes
1 answer
3k views

How could March 30th 2024 be followed by the 1st?

I am in the EU zone +1 or when DST is on, +2. Now is Sunday 31.3.2024. This Sunday morning, we changed into DST, at 2→3 (CET → CEST). I have Linux servers in separate networks reporting monthly energy ...
Pila's user avatar
  • 465
2 votes
0 answers
56 views

High resolution sleep in kernel thread?

What is the correct way to sleep to us resolution in a thread? I'm trying to write a device driver and I need to keep a pin high for a certain number of us after a GPIO interrupt. My plan is to create ...
FourierFlux's user avatar
0 votes
1 answer
216 views

What does the "segfault at X" kernel log message mean if X is very large?

I've got a device with bad RAM. Running memtest overnight shows all faulting addresses to be in the 0x7d0000000 - 0x7f0000000 range. I plan to replace the RAM, but until then, I've disabled a 2GB ...
thariqfahry's user avatar
4 votes
1 answer
130 views

When (and how) are file permission/access decisions made in kernel space?

(I think) I have a relatively good understanding of how Linux permissions work - traditional Unix DAC permissions, and how they're represented, security context in relation to processes (i.e. cred ...
genericuser99's user avatar
1 vote
0 answers
53 views

Is there a known linux kernel bug with two threads incorrectly getting back the same file descriptor number?

I've got a multithreaded program in which a sem_open with O_CREAT occasionally fails with EBADF. This is on an ARM linux 4.9.88, from NXP, on an embedded device. It is very difficult to reproduce, ...
Matt DiMeo's user avatar
3 votes
2 answers
122 views

How does the Linux Kernel store hardware TX and RX filter modes?

I am working on a C program which gets the timestamping information for a given network interface, like my own version of ethtool. My goal is to get the information printed by $ ethtool -T myNetIf. ...
Robbie's user avatar
  • 63
1 vote
1 answer
135 views

Where do i trace NVME IO within the Linux driver?

I want to write a small Linux driver extension. More specific: I want to write all the communication between the host and a M.2-nvme-ssd into a userspace file. The nvme driver is pretty big though and ...
led's user avatar
  • 13
0 votes
0 answers
50 views

How to disable kernel_lockdown (MSR) without BIOS or console access

I have a laptop with a damaged screen. I use it by connecting a screen via HDMI. I'm running some cryto mining software that requires MSR access to run efficiently. I cannot access the BIOS to disable ...
Nadim Ghaznavi's user avatar
1 vote
0 answers
102 views

Home Server/NAS Plagued by random crashes

I'm here to get help for an issue which has been plaguing me for a year. I'm using HP Elitedesk 800 G3 i5-7500 as my Home Server/NAS. I have the latest Debian 12 (Bookworm) on it. I'm running my ...
Aciel's user avatar
  • 11
-1 votes
1 answer
421 views

"Error! Installation aborted" - dkms problem when installing or upgrading

When I tried to install something from GitHub or even update and upgrade the system, the error message shown below is displayed. This is on the Kali distribution. The problem is related to the Realtek ...
SuperMassive's user avatar

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