How to get list of deprecated kernel functions for different kernel versions?
While compiling an external linux kernel module for a 5.0 kernel version (x64 module on native x64 system) with deprecated function 'timespec_sub' (was compileable at least until kernel version 4.15)...
View Articleuserfaultfd seems slow - is it expected?
When I first learned about usefaultfd my initial reaction was - wow, finally! - this is a very useful feature, I can see some interesting applications of it outside of QEMU/KVM kind of scenarios.So, I...
View ArticleHow does the page table of the page fault handler is loaded into the MMU?
Can someone please explain to me how does the page fault handler's page table is loaded into the MMU ?Lets consider that a process A is being executed which page table has currently been loaded into...
View ArticlePermission denied on Nova Server
I am using a Linux based server as portal for my assignments at UMUC called Nova. In order to access this portal, i am prompted to enter my UMUC credentials. After my password is entered, I receive...
View ArticleHow to write dummy ALSA compliant device driver?
I want to write dummy ALSA compliant driver as a loadable kernel module. When accessing it by aplay/arecord throught the ALSA-lib, let's say, it must behave as normal 7.1 channel audio device providing...
View ArticleHow to know which core that send the inter-processor interrupt?
I am working on ARM64. I add an inter-processor interrupt (IPI) handler in void handle_IPI(int ipinr, struct pt_regs *regs) in linux/arch/arm64/kernel/smp.c.When I get an IPI, I want to know which core...
View ArticleWhen will getsockname() set ENOBUFS？
When will getsockname() set ENOBUFS？The manual says getsockname() can set errno to ENOBUFS, but I have checked the related source code inside kernel(3.10, 4.9,...
View ArticleWhat are the most common busmaster operations, and how are they better than...
Can someone list the most common operations that use the bus mastering provision of the host bus? I can list a few..1) The GPU transfers the overall framebuffer to the video card using bus-mastering...
View Article'Bad page state' kernel error appearing randomly on azure vm when SAS is running
Since a few months, we start seeing Bad page state errors appearing in /var/log/message.Here is the exact stack traceSep 27 15:14:11 az-prod-sas1 kernel: BUG: Bad page state in process sas pfn:1a49ff...
View ArticleHow to know linux scheduler time slice?
I'm looking for the value of the time slice (or quantum) of my Linux kernel. Is there a /proc file which expose such an information ?(Or) Is it well-defined in the Linux header of my distributions...
View ArticleInconsistent values of ARM PMU cycles counter
I'm trying to measure performance of my code in linux kernel with pmu. First of all I want to test pmu therefore created simple loop of couple operations in kernel. I placed it under spin lock with...
View ArticleWhy can moving the mutex_unlock() after dev_kfree_skb() eliminate the...
Recently, I find a paper named "Effective Static Analysis of Concurrency Use-After-Free Bugs in Linux Device Drivers". It uses a motivating example (it is also a kernel patch:...
View ArticleIf I do not acquire a spinlock in a softirq, is it then alright to sleep?
If I do not acquire a spinlock in softirq context, is it then alright to sleep?I understand that it is incorrect to sleep after acquiring a spinlock. The process put to sleep might wake up on another...
View ArticleLinux kernel thread address space
I read that linux kernel threads don't have their own address space, their mm field is set to NULL. I know that all kernel threads share address space, but still, they have their own stack right? They...
View ArticleWhat is TCP socket status 8A, as shown in /proc/net/tcp?
I'm trying to interpret the status ('st') column of output from /proc/net/tcp, and I'm seeing unexpected values.I've seen previous questions like List of possible internal socket statuses from /proc....
View ArticleWhich process runs first when a fork() is called
I wrote this programmain() { int pid; pid=fork(); if(pid==0) printf("\nI am child\n"); else printf("\nI am parent\n"); return 0; } Whose output when executed is ./a.out I am parent I am child When I...
View Articlecurrent->mm gives NULL in linux kernel
I would like to walk the page table, so I have accessed the current->mm, but it gives NULL value.I'm working on linux kernel 3.9 and I don't understand how could current->mm is zero.Is there...
View ArticleCalling user-space program functions from kernel modules [duplicate]
This question is an exact duplicate of:How can I Execute/Call a user-space defined function from Linux kernel space module? 2 answersFirst of all, I am working on an embedded board which I want to take...
View ArticleWhat is "the kernel address space"?
From Understanding The Linux Kernel, here is some discussion about kernel thread vs user process i.e. regular process:Besides user processes, Unix systems include a few privileged processes called...
View Articlewhat's the execution order of multiple child processes
use the follwing code to fork four chile processes#define _GNU_SOURCE #include <stdio.h> #include <unistd.h> #include <sys/wait.h> #include <stdlib.h> pid_t pid; int child(int...
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