Why I'm not receiving my messages from kernel?
I'm trying to send a message from kernel to user space using generic netlink and libnl, the part of my code which does this is implemented as follow:int struct my_callback(struct sk_buff *skb, struct...
View ArticleWho calls the probe() of driver
How does probe() call gets called? Who calls it? As per my understanding, __init() registers driver and then somehow probe() is called to register the device data and irq etc. How exactly it happens? I...
View ArticleNetlink: sending from kernel to user - EAGAIN and ENOBUFS
I'm having a lot of trouble sending netlink messages from kernel module to userspace-daemon. They randomly fail. On the kernel side, the genlmsg_unicast fails with EAGAIN while on the user-side,...
View ArticleWhat is the correct way to send and receive messages from kernel to user...
I've read a lot about how to send messages from kernel to user space, including this article on lwn, the documentation on infrared and a lot of questions related to this subject here on StackOverflow,...
View ArticleContext switch in the middle of a system call
Assume we have 2 threads in the process.now we run the following code:read(fd, buf, 10);where fd is some file descriptor which is shared among the threads (say static), and buf is an array which is not...
View ArticleHow does the AF_PACKET socket work in linux?
I am trying to write a C sniffer for linux, and understand the actions happening in the kernel while sniffing.I am having troubles finding an answer for the following question:If I initialize my socket...
View ArticleEdit/Modify extlinux.conf on a Linux Failed to Boot [closed]
My system experienced an error in extlinux.conf due to a recent update.The root parameter was messed up. As a result, my Linux system cannot be booted. The system will show the manufacturer logo, a...
View ArticleCan Linux kernel support RSTP (802.1w)?
Last week, I ran Spanning Tree Protocol (STP) in Linux kernel successfully.Now, I am trying to support Rapid Spanning Tree Protocol (RSTP) in Linux kernel.I also found out some solutions in user space...
View ArticleWhere is linux-vdso.so.1 present on the file system
I am learning about VDSO, wrote a simple application which calls gettimeofday()#define _GNU_SOURCE#include <sys/syscall.h>#include <sys/time.h>#include <stdio.h>#include...
View ArticleWhere are the sockets saved in the kernel?
I am having troubles finding answer to this question:When the kernel receives a packet and processes it, how does it knows which sockets are available? I have seen that there is some kind of a socket...
View ArticleWhy am I not receiving my messages from kernel?
I'm trying to send a message from kernel to user space using generic netlink and libnl, the part of my code which does this is implemented as follow:int struct my_callback(struct sk_buff *skb, struct...
View ArticleMeasuring syscall overhead in Linux
I have been searching for an appropriate method to measure cost of various syscalls in the Linux OS. There have been many questions raised related to this topic in the past, none provide a detailed...
View ArticleHow does Linux uprobe handle breakpoint?
From what I understand, on x86, uprobe places an int3 instruction at the user specified location, and handles that exception when it is hit, somewhat similar to kprobe in that regard.What I do not...
View ArticleWait queue and race condition
I'm reading "Linux Kernel Development" by Rovert Love and found the code below to wait for an event.DEFINE_WAIT(wait);add_wait_queue(q, &wait); while (!condition) { // What happens if condition is...
View ArticleSwitch Boot SDCard Linux
I have an embedded system which running custom debian in it, the hardware contains a SDCard built-in, and another SDCard slots for external SDCard. The built-in SDCard already contained a system image...
View Articlegetting internet using networkmanager in linux based yocto
I installed modemmanager and networkmanager in linux based yocto . but i am not able to connect internet follow commands a below :- 1) systemctl start Networkmanager. 2) systemctl enable...
View ArticleWhy do we need to call local_bh_disabled() before calling the function...
I can't understand what is the role of the function local_bh_disable() which is called before the function conn_request()here. Does that mean that only one process can access this section at this point...
View ArticleHow to extract the config from a kernel image file when CONFIG_IKCONFIG is...
How do I extract the kernel configuration from a kernel image file?The kernel image file type is:/boot/kernel7.img: Linux kernel ARM boot executable zImage (little-endian)The kernel has been compiled...
View ArticleKernel panic with exitcode=0x00000004 after /init
I have an embedded ARM system with processor AT91SAM9G45. I try to build linux kernel with initramfs for this system. Kernel version is 4.14.79.After loading kernel and initramfs image at device I have...
View ArticleHow does the Linux kernel choose the virtual net interface when receiving a...
I have two Linux servers and create a macvlan interface from physical NIC eth0 on each server. And I also config the macvlan IP and set them up, so they can ping each other.Under the kernel TCP/IP...
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