Programming :: Calling Kernel Functions From Userspace?
Feb 5, 2010
I'm trying to call some kernel functions from userspace, but I'm not sure if I'm doing it right. The functions control a pulse width modulator on an embedded platform. To pick one at random, the function:
Code:
struct pwm_device *pwm_request(int pwm_id, const char *label);
is defined in linux/pwm.h, and the implementation uses the macro EXPORT_SYMBOL(pwm_request), so I should be able to call this from user-space... right?
Anyway, I've got linux/pwm.h to #include in my source so the compiler knows what it's doing, but what do I link against? The only place in by kernel build tree where I can see a symbol pwm_request defined is in object files like vmlinux.o, built-in.o in the directory, etc. which I don't think I should be linking against.
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Apr 11, 2011
I feel like there should be a cleaner way of doing this. I have one file, for example "a.cpp", calling a function from another file, "b.cpp". Currently I have it set up so that header for "b", "b.h", has the declaration of its functions. And then I'm just including "b.h" in "a.cpp". Do I have to include the "b" header file in "a" to be able to call a function from "b"? Or is there a better way I could be doing this? Like doing something different at compile?
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Mar 1, 2011
How does a C program start in linux? Is main() the first function called in the a c application by kernel. I understand it is the first called function written by the application programmer, but the question is to understand the what all kernel does and what all functions it calls before calling main()
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Aug 2, 2010
My distribution is Fedora 12. When I want to get the infos of kernel functions such as printk, i type man printk, failed. I look up some articles and learn that in some distributions the kernel functions is in section 9 of man page. Then i type man 9 printk also no reply. How can i get man pages of kernel functions ?
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Jun 27, 2009
I am dealing with some Linux kernel code, which define most its functions with Macros.The trouble I am having is to use those code in user space in Windows.
For example, I have a function defined like this:
#define list_for_each_entry_safe(pos, n, head, member)
for (pos = list_entry((head)->next, typeid(*pos), member),
n = list_entry(pos->member.next, typeid(*pos), member);
&pos->member != (head);
pos = n, n = list_entry(n->member.next, typeid(*n), member))
And in user space code, I call it in this way:
list_for_each_entry_safe( pcre_item, tmp,
&(((pcre_list_head_t *)(hr.value))->head), list)
{
// My code to handle each element in the list
}
This is working like a charm in Linux, but I got errors in Windows:
It reminds me missing ';' after 'list_for_each_entry_safe( pcre_item, tmp,
&(((pcre_list_head_t *)(hr.value))->head), list)'.
Does this kind of linux code not working in Windows at all? (Linux is in GCC C stand and VC is ANSI C) I prefer not to convert them to normal functions but keep it the way if it could be working under windows by some tricks.
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Jul 9, 2010
I used the Netlink mechanism before but it seems that it is not High-Efficiency.Is there another way or other ways better?
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Jun 7, 2010
I am trying to access a generic netlink family to send messages from user-space to the kernel. I am using libnl example here [URL].. The problem is that I keep getting
Code:
error: netlink/genl/genl.h: No such file or directory
error: netlink/genl/ctrl.h: No such file or directory
You would think I have not installed libnl and libnl-devel but I have.
[Code]...
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Aug 27, 2010
Is there an interface whereby a userspace program can retrieve the raw keycodes/scancodes from a keyboard? I'm trying to make something in the way of a piano keyboard, and I need to know when keys are pressed (possibly simultaneously), and when they are released.
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Jan 20, 2011
I wrote the following script to organize my music files and to learn a bit more about bash.
My problem is, now that I'm almost over the first version, that functions which are surely spelled correctly and were recognized in the past, are giving me the "command not found" error!
Code:
#!/bin/bash
# This is a script for moving tagged files into organized directory trees.
##### Variables
filenum=0
[Code]....
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Mar 11, 2010
Is it possible to define functions within other functions in C++? I know it is the case in other languages.
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Apr 11, 2011
I need help as I am not proficient with Linux C++ Programming. There are two parts which I need to do in the coding provided below.
1. Produce the program so it can output the word "Hey there!" and wait two minute and print the word "See you later!".
2. Produce the program that will output the text "Cool" every 20 seconds by setting a periodic task.
Quote:
#include <linux/kernel.h>
#include <linux/module.h>
MODULE_LICENSE("GPL");
int init_module(void)
{
printk("Hey there!
[Code]...
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Apr 4, 2011
I am the new child of the linux world. What is the difference and working functions between kernel and shell..
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Jan 12, 2010
what kernel file holds the functions for the hardware configuration. I'm interested in finding the hardware timer of the linux and the DMA configuration file. I assume there is a single file that holds configuration data for the platform.This probably is executed before the kernel is started. As is see it this must be some hardware abstraction layer file because the actual kernel code is not platform dependent.
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Jun 4, 2010
I have a question about calling an asm function from C....It doesn't work unless I create an asm variable to hold the value of the function in....Why?Here's the code that doesn't work...
asmfile.s - version one Code: .section .data
mydata: .ascii "this is the message!
.equ mylen, . - mydata
[code]...
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Feb 7, 2011
I am doing a web site program and what I need is to call a C program in the PHP cloud.Do u think it would be possible? The web site would get the user input from PHP UI and pass to the C program , the C program would process the function with the user input and output the a PHP page.
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Mar 19, 2011
None of my daemon scripts work now, and the startup process displayed errors. Should I reinstall the OS and start from scratch, or is there a way to recover these files? Is there a way to rebuild the files I deleted?
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Aug 13, 2010
I want to call c exe from java source code and i want to interact with the c program during it's execution, i am able to send the parameters to c program but i am not able to interact with it.
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Feb 17, 2011
I have found a weird behaviour on a linux application. A tty seems to get closed without calling close. The program is (very simplified) as follows:
Process 1:
configure_signals()
read_config_files()
create_threads()
wait(forever)
Thread 1:
fd=open(/dev/ttyXX)
usleep(a while)
config(fd)
I have spent quite a lot of time on this problem. It seems like the file is sometimes closed when reaching config(fd), but removing the usleep(a while) seems to remove the problem.
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Jul 17, 2010
I have a bash script that changes the iptables.Now i call this bash script in my php code.When this bash script is running the part of code that contains iptables instruction is not running because we need to be in superuser mode(root)
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Apr 15, 2009
I'm trying to call some Fortran 95 code in C, but I'm having problems with integers not having the same value in C as in Fortran, and changing values upon each run of the program. I think it has to do with the integer type, but I don't know how to fix it. I'm running Gentoo x86. Here are the files I've got:
foo.c:
Code:
#include <stdio.h>
extern int qux_();
main() {
[code]....
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Aug 19, 2010
What is the difference in perl between:
'function();'
and
'&function();'
with and without ampersand.
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Jul 30, 2011
i use the sockaddr_in like this before calling bind(), it works good.
Code:
sockaddr_in serveraddr;
serveraddr.sin_port=htons(5000);
serveraddr.sin_addr.s_addr=htonl(INADDR_ANY);
serveraddr.sin_family=AF_INET;
[Code]....
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Mar 26, 2011
could you please explain few questions about systemtap.
1st
===
seems gettimeofday_s() always returns 0 Code: stap -ve 'probe timer.s(4){ printf("%d ",
[code]....
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May 20, 2010
I'm trying to call a system command in perl and am having an issue with it.
Here's an example of a command i'd like to call: Code: sed -i '4 c192.168.1.4 www.something.com' hosts this is the section in my perl script where I create the variable and call it: Code: $doit = `sed -i '$line c$ip $host hosts'`system($doit); The $line, $ip, and $host variables are working fine becasue I can replace that section with "prints" and they come out fine. I imagine the problem is where I am creating the $doit variable.
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Jan 21, 2011
I want to call a subroutine in Fortran 90 from a c++ code. I can do it, when the fortran code have no module. But i need to call the subroutine in a fortran code that have an module. I have a simple program that shows my problem. The Fortran code is:
Code: !add2.f90
Module add2
Implicit none
Contains
[code]....
collect2: ld returned 1 exit status I Dont know where is the problem. Maybe it is in the call of the function. I found that the syntax have this form: extern void __namemodule__NMOD_namesubrutine(arg)
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Oct 4, 2010
I am trying to use a software package written in ANSI C. It has a makefile which has to be executed first.
As soon as I execute it I get messages like: line i: command not found.
Commands for which I am getting errors :
CC = /usr/bin/gcc
GCCFLAGS = -c -Wall
ROOTDIR = .
My gcc compiler is located in the above directory only. In ROOTDIR also I tried giving the path in which all the required files & folders are present but still I get the command not found error in all the lines.
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Oct 29, 2010
I have written FORTRAN code to calculate density profile. This code will open two files ( topology and x,y,z trajectory). The trajectory file contains XYZ data coordinates for multiple frames (about 20 or 100 frames for instance). One frame contains 20736 data.
Previously this code was written to open ONLY one input XYZ data file and do the calculation and would dump the results in separate file and it was running without problem. Recently my data file get bigger in size, so I decided to break the single XYZ data file into few small parts.
Now I have modified the code so that it calls the parts of the XYZ data files ( eg: maltoTHERMO_10Frames.traj, maltoTHERMO_20Frames.traj,... and so on) and do the calculation and dump the results in the same result output file. I have tested this code just with openning the XYZ coordinates and printing into another file to see wheather it collecting the data sequently and it was working fine.
This code supposedly read the x coordinate data and calculate distance and put a count accoding the criteria in the approperiate bins. But when I let the code to do the calculation it stop and shows error. (I have indicated as !** in the code). If I enable this line, it shows error but if I disable this line, than the code do collect only the XYZ coordinates.
The code is as below:
Code:
module all_parameter
integer,parameter :: MAXATOM=20736!CHANGE
integer,parameter :: midwater=1500
integer,parameter :: TOTALFRAMES=20
[Code]....
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Mar 2, 2011
I have typed the following code:
Code:
<html>
<form enctype="multipart/form-data" action="upload.php" method="POST">
[code]...
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Oct 17, 2010
lets look at code in C
Code:
#include <stdio.h>
#include <stdlib.h>
[code]...
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May 5, 2010
I am trying to play with calling text files in C. What I have is a text file with 4 columns of numbers I need to average 2 of them. I have started and hit a wall. I have the following so far:
[Code]....
I still need to figure out how to read the data in. I have been reading on this for a few hours and its not clicking. How does the program know which columns with names to call. the data is organized: ID, Day, Speed, Temp.
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