Questions tagged [kernel]
In computing, the kernel is a computer program that manages input/output requests from software, and translates them into data processing instructions for the central processing unit and other electronic components of a computer. The kernel is a fundamental part of a modern computer's operating system. This tag is for general questions regarding code that runs in the context of an operating system kernel.
kernel
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What are some resources for getting started in operating system development? [closed]
One thing I've always wanted to do is develop my very own operating system (not necessarily fancy like Linux or Windows, but better than a simple boot loader which I've already done).
I'm having a ...
221
votes
10
answers
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What is the difference between Trap and Interrupt?
What is the difference between Trap and Interrupt?
If the terminology is different for different systems, then what do they mean on x86?
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answers
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How do I convert dmesg timestamp to custom date format?
I am trying to understand the dmesg timestamp and find it hard to convert that to change it to a Java date or custom date format.
Sample dmesg log entry:
[14614.647880] airo(eth1): link lost (missed ...
- 2,828
166
votes
16
answers
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What is the difference between the kernel space and the user space?
What is the difference between the kernel space and the user space? Do kernel space, kernel threads, kernel processes and kernel stack mean the same thing? Also, why do we need this differentiation?
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What is an OS kernel ? How does it differ from an operating system? [closed]
I am not able to understand the difference between a kernel and an operating system. I do not see any difference between them. Is the kernel an operating system?
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148
votes
4
answers
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cscope or ctags why choose one over the other? [closed]
I primarily use vim / gvim as an editor and am looking at using a combination of lxr (the Linux Cross Reference) and either cscope or ctags for exploring the kernel source. However, I haven't ever ...
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142
votes
6
answers
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What is difference between monolithic and micro kernel?
Could anyone please explain with examples difference between monolithic and micro kernel? Also other classifications of the kernel?
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140
votes
3
answers
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kernel stack and user space stack
What's the difference between kernel stack and user stack? Why kernel stack is used? If a local variable is declared in an ISR, where it will be stored? Does each process has its own kernel stack? ...
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133
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3
answers
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What is the difference between the operating system and the kernel? [closed]
I do not understand the difference between operating system and kernel. Can someone please explain it?
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6
answers
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What is __gxx_personality_v0 for?
This is a second-hand question from an OS development site, but it made me curious since I couldn't find a decent explanation anywhere.
When compiling and linking a free-standing C++ program using ...
- 8,544
109
votes
2
answers
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What are vdso and vsyscall?
I did sudo cat /proc/1/maps -vv
I am attempting to make sense of the output.I can see a lot of shared libraries being mapped to the memory mapping segment as expected.
7f3c00137000-7f3c00179000 r-xp ...
- 14.7k
102
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4
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The difference between initrd and initramfs
As far as I know, initrd acts as a block device, thus requiring a filesystem driver (such as ext2). The kernel must have at least one built-in module for detecting filesystem of initrd. In this ...
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102
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3
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Context switches much slower in new linux kernels
We are looking to upgrade the OS on our servers from Ubuntu 10.04 LTS to Ubuntu 12.04 LTS. Unfortunately, it seems that the latency to run a thread that has become runnable has significantly increased ...
102
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1
answer
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What does [ N ... M ] mean in C aggregate initializers?
From sys.c line 123:
void *sys_call_table[__NR_syscalls] =
{
[0 ... __NR_syscalls-1] = sys_ni_syscall,
#include <asm/unistd.h>
};
sys_call_table is a generic pointer to arrays, I can see ...
- 18.3k
95
votes
8
answers
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Linux Process States
In Linux, what happens to the state of a process when it needs to read blocks from a disk? Is it blocked? If so, how is another process chosen to execute?
- 3,701
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Interpreting segfault messages
What is the correct interpretation of the following segfault messages?
segfault at 10 ip 00007f9bebcca90d sp 00007fffb62705f0 error 4 in libQtWebKit.so.4.5.2[7f9beb83a000+f6f000]
segfault at 10 ip ...
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Context switch internals
I want to learn and fill gaps in my knowledge with the help of this question.
So, a user is running a thread (kernel-level) and it now calls yield (a system call I presume).
The scheduler must now ...
- 34.5k
82
votes
7
answers
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Is there a way to figure out what is using a Linux kernel module?
If I load a kernel module and list the loaded modules with lsmod, I can get the "use count" of the module (number of other modules with a reference to the module). Is there a way to figure out what is ...
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80
votes
3
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What are the implications of the linux __user macro?
I was hoping someone could explain the nuances of the __user macro used in the linux kernel source.
First of all, the macro:
# define __user __attribute__((noderef, address_space(1)))
Now, ...
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72
votes
6
answers
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How closely are Mac OS X and BSD related?
I read that Mac OS X and bsd are related. How closely are they related. Can Mac OS X software be tweaked and installed on BSD?
- 14.5k
71
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2
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What does a dot before the variable name in struct mean?
looking at the linux kernel source, I found this:
static struct tty_operations serial_ops = {
.open = tiny_open,
.close = tiny_close,
.write = tiny_write,
.write_room = tiny_write_room,
....
- 1,152
67
votes
5
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What is preemption / What is a preemtible kernel? What is it good for?
Explained in your own words, what is preemption and what does it mean to a (linux) kernel?
What are advantages and disadvantages in having a preemptible kernel?
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4
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Linux kernel "historical" git repository with full history
I think many developers like to investigate sources with the help of git gui blame. As explained in the commit for Linux-2.6.12-rc2 (also mirrored at Github), it needs to have special historical Linux ...
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62
votes
8
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BTF: .tmp_vmlinux.btf: pahole (pahole) is not available
Getting this error while compiling the kernel version :5.7-rc4
BTF: .tmp_vmlinux.btf: pahole (pahole) is not available
Failed to generate BTF for vmlinux
Try to disable CONFIG_DEBUG_INFO_BTF
make: ***...
- 621
62
votes
6
answers
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Is Pthread library actually a user thread solution?
The title might not be clear enough because I don't know how to define my questions actually.
I understand Pthread is a thread library meeting POSIX standard (about POSIX, see wikipedia: http://en....
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votes
11
answers
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How is Linux kernel live debugging done and what tools are used?
What are the most common and why are uncommon methods and tools used not to do live debugging on the Linux kernel?
I know that Linus, for example, is against this kind of debugging for the Linux ...
- 6,329
61
votes
3
answers
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Android Kernel Debugging
I have been experimenting with getting kgdb to work the Nexus One.
I have pulled the kernel from https://android.googlesource.com and enabled everything to do with kgdb including kgdbts testing using ...
60
votes
6
answers
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Cannot boot Windows guest in VirtualBox without kernel module error
I'm running Vagrant (1.8.1) + VirtualBox (5.0.12) on Windows 7 and trying to boot up a Windows 7 image (modernIE/w7-ie8). However, I get this error:
---------------------------
VirtualBox - Error In ...
- 22.1k
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what is the use of SPL (secondary program loader)
I am confused in clearing my concepts regarding these three questions
why do we need a secondary program loader ?
in which memory it gets loaded and relocated ?
what is the difference between ...
- 1,594
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votes
7
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Learning Kernel Programming [closed]
I want to learn lLinux Kernel programming.
What would be the starting points for that? What could be some of the simpler problems to target?
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How do I configure modprobe to find my module?
I'm trying to get a kernel module to load at boot.
If I run insmod /path/to/module.ko, it works fine. But this has to be repeated every time I reboot.
If I run modprobe /path/to/module.ko, it can't ...
- 1,049
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How does Linux determine the next PID?
How does Linux determine the next PID it will use for a process? The purpose of this question is to better understand the Linux kernel. Don't be afraid to post kernel source code. If PIDs are ...
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votes
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How does the linux kernel manage less than 1GB physical memory?
I'm learning the linux kernel internals and while reading "Understanding Linux Kernel", quite a few memory related questions struck me. One of them is, how the Linux kernel handles the memory mapping ...
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Getting iOS system uptime, that doesn't pause when asleep
I'm looking for a way to get an absolute, always-incrementing system uptime on iOS.
It should return the time since the device was last rebooted, and not be affected by changes to the system date.
...
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votes
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What's in include/uapi of kernel source project
Can someone please give me a document to describe the kernel source folders about their structure, functionality and how they are organized?
Specifically, what's the use of of the folder include/uapi/...
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How does Docker for Windows run Linux containers?
In the old versions of Docker for Windows, I remember it explicitly said it used a linux VM for the kernel.
But since the new stable version (released in July 2016 I think), it says
Docker for ...
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votes
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What is kthreadd process and children and how it is different from init and children
I wanted to know what is kthread and why it does not take any memory and has no open files. I wrote some code which will simply print the PID of the currently running processes in a parent child tree ...
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votes
5
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Relationship between a kernel and a user thread
Is there a relationship between a kernel and a user thread?
Some operating system textbooks said that "maps one (many) user thread to one (many) kernel thread". What does map means here?
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What kind of C is an operating system written in?
It makes sense that something like an operating system would be written in C. But how much of it, and what kind of C? I mean, in C, if you needed some heap memory, you would call malloc. But, does an ...
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How can I programmatically manage iptables rules on the fly?
I need to query existing rules, as well as being able to easily add and delete rules. I haven't found any API's for doing this. Is there something that I'm missing?
The closest I've come to a ...
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What does "proto kernel" means in Unix Routing Table?
I've been searching this in linux-ip.net and the whole internet but does appears nothing.
What does the "proto kernel" part means in a Routing Table?
Just an example:
[root@tristan]# ip route show ...
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Install Python 3.8 kernel in Google Colaboratory
I try to install a new Python version (3.8) using conda.
!wget -O mini.sh https://repo.anaconda.com/miniconda/Miniconda3-py38_4.8.2-Linux-x86_64.sh
!chmod +x mini.sh
!bash ./mini.sh -b -f -p /usr/...
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How do I programmatically disable hardware prefetching?
I would like to programmatically disable hardware prefetching.
From Optimizing Application Performance on Intel® Core™ Microarchitecture Using Hardware-Implemented Prefetchers and
How to Choose ...
- 1,485
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votes
7
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Reset ipython kernel
I was wondering if there is a way to restart the ipython kernel without closing it, like the kernel restart function that exists in the notebook. I tried %reset but that doesn't seem to clear the ...
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Mac OS X virtual audio driver
I want to create a virtual audio device that gets audio data from the default output (which is an output IOAudioStream) and converts it to an input IOAudioStream.
I went through most of the examples ...
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How can I display the version of my Jupyter notebook and run cells in Jupyter notebooks? I get an error: bad interpreter
I have installed Anaconda and I use the conda environments and the conda command to install software.
When I type:
jupyter notebook --version
I get the following error:
zsh: /Users/cr517/.local/bin/...
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What parts of Linux kernel can I read for fun? [closed]
Programming isn't my main job, though I enjoy it and sometimes get paid for it. For many years now I've been hearing about Linux and my friends have shown to me many *nixes (or *nici?), though I stick ...
39
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3
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why is u8 u16 u32 u64 used instead of unsigned int in kernel programming
I see u8 u16 u32 u64 data types being used in kernel code. And I am wondering why is there need to use u8 or u16 or u32 or u64 and not unsigned int?
user966588
39
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1
answer
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How / Where to find Linux Kernel Bugs to Fix?
I'm trying to find bugs that needs to be fixed in the Linux Kernel but I don't know where to look. I watched the video "How to Submit Your First Linux Kernel Patch" by Greg Kroah-Hartman on Youtube, ...
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Does linux schedule a process or a thread?
After reading this SO question I got a few doubts. Please help in understanding.
Scheduling involves deciding when to run a process and for what quantum of time.
Does linux kernel schedule a thread ...
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