I manage to use the function "time" and "localtime" in gcc.But while I used it in a module in kernel space the above 2 functions are giving error.Even in kernel space time.h header file is not identified. tell the similar time function which can be used in kernel space
View 1 RepliesI am writing device driver in which i have to call callback function from kernel space, which are saving my data. But the callback functions are in userspace. While accessing them i am getting segmentation fault.
View 1 Replies View Relatedmeasure kernel space time and user space time?
View 1 Replies View RelatedI wanna write a file in kernel space but from my searching I can to know that instead of writeing file in kernel space ,I can write data to user space by copy_to_user space.
But link is missing ...I dont know how will my user space will access kernel space means my function in kernel space which will do copy_to_user /....How my user space function will call my kernel level function ..
Can any one of you provide me with some example file which are doing this .I know every char driver is using it ...but i could not trace back how user level function is accessing it ...i m confused between user space and kernel space.
I have written a programme in gcc
#include <time.h>
#include <stdio.h>
int main(void)
[code]...
Logical Memory Space of 4GB is divided in to 3GB User Space and 1GB Kernel Space. Always. Correct?
1. How can we change it? (just changing value of PAGE_OFFSET is okay?)
2. If system have only 256MB of memory (embedded system) and suppose Kernel Modules eat away all the memory during boot. User space will be left will no memory. Is this case possible?
I am using Debian linux. I have 100 timers running. If a timer expired which will generate a signal and it was mapped to a same function handler. All the timers are mapped to one function handler. The problem is if the timer expires one at a time, the function handler called at a time. But if the 2 timers expires at a time, the function handler is called one time only instead 2 times. Is it possible to invoke the function handler as many times based on timer expirary happens simultaneoulsy?
View 14 Replies View RelatedI am developing a function say my_abc() which does the same thing as kernel function abc(). Now I want that instead of using predefined kernel function kernel starts using my function. It might be possible that the kernel function has been used so many places.
View 7 Replies View RelatedI have read a couple of articles on how dynamic linking works (those stuff about got, plt and lazy binding), and I am still not sure why you need to do dynamic linking in such a complicated way.Suppose your program uses a function in a shared library that needs to be linked dynamically at run time (like a printf). Why can't you statically decide the virtual address of the function at compile time? After all, all you need to do is to enter the page table entry corresponding to the address of the function if the library has been already loaded to a physical page frame.
View 3 Replies View RelatedKernel driver function was called via ioctl and returned success, but when I checked the kernel display buffer with dmesg the printk message was not there. Then when you do lsmod, the driver you were calling showed "used by zero". So it seems like the kernel driver was not accessed. In the kernel driver, I had many printk statements, but nothing printed in the buffer. if the driver get accessed and what could cause this?
View 1 Replies View RelatedI am developing a I2C CDROM client driver. The CDROM firmware supports TOC information read through a I2C command. It sends the TOC information in burst ( Interrupts a GPIO pin when it is ready ) and my CPU does a I2C read to read the TOC. When the CDROM firmware finishes sending the last data burst , it informs my CPU that it is done with the TOC, by a flag in the last data burst. I would like to know, which is the most efficinet way I can send these TOC information to userspace?
View 4 Replies View RelatedHow to use execv from kernel space to call a user space program writtenfor socket prog.
I tried to write code for socket in kernel but its not working.
Socket code in kernel is also needed.
While booting Linux it takes ages for 'enabling swap space'
I have allocated swap space twice that of the RAM.
Is there a way to fix it? What should I do to avoid this in the future installs?
I have the following requirement in my module. The driver gets some data from the external device. After getting 1MB of data it has to send it to the user space application. What is the best thing to implement for this in driver.? Is it ok to implement like, after getting data, the driver will send a signal to the user space application. Then the user space application sends an ioctl to read the data. Is there any alternate, that the driver directly sends the data without the user space application asks for it.?
View 4 Replies View RelatedI have 40gb of hd and I want Xp and fedora on it. I installed Xp first and now I want to install Fedora 12, every time I chose the space to iinstalll it, it says that there is no enough space to install it, although the xp just took less than 2gb of the disk. How can I resize it so that there is enough space?
View 8 Replies View RelatedHow do you interface with the Linux I2C driver from kernel space? For example, if I had LEDs connected to a GPIO expander on the I2C bus, how would I blink them twice before going down for reset from machine_reset()?
Essentially, I believe I need to call the functions i2c_smbus_write_byte(), i2c_smbus_read_byte(), etc. But these functions require I2C client data that I do not understand how to supply.
I am trying to build linux kernel I am getting out of space after a while. I unpacked it in /usr/src directory. It seems I have plenty of space. How much space does it need to compile & build kernel. I am using VirtualBox.
root@vinay-VirtualBox:/usr/src/linux-2.6.39.3# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 6.9G 3.2G 3.4G 49% /
none 669M 640K 668M 1% /dev
none 675M 24K 675M 1% /dev/shm
none 675M 96K 675M 1% /var/run
none 675M 0 675M 0% /var/lock
/dev/sr0 39M 39M 0 100% /media/VBOXADDITIONS_4.0.10_72479
Is there any inbuilt function other than strncmp which can evaluate a string.my requirement is " if all 10 values are spaces print 1 else if it contains some values print 2 else print 3.if i use strlen, even space is counted.I know that i can evaluate using for loop by checking 1 by 1 char, and using strcmp function, is there any other way?
View 2 Replies View RelatedI'm pretty new to this whole (micro)kernel architecture story.
Im wondering if a kernel module is running in kernel or in user space?
Is a driver running as kernel module slower than a driver build into kernel?
If so, are there some current articles, benchmarks?
what difference between user and kernel space.
View 2 Replies View RelatedI need a shared buffer between user and kernel space. I read that one way is to allocated buffer in kernel and then call mmap from the user space. I searched for an example but couldn't find something useful. If you know, could you please send me any links or sample code that does this..
View 1 Replies View RelatedCode:
#!/bin/ksh
(...)
# FILL UP PARTITION
diskfillerfunction () {
[Code]....
Test 15: fill up partition /usr/bin/time: cannot run diskfillerfunction: No such file or directory
I am obviously omitting (...) a lot of the code, but the relevant part is all there. How do I 'time' a function?
As i undertsand - out of 1GB of the virtual Address space for Kernel from 3GB to 4GB of the process address space, Kernel image (code, data, bss, stack, heap) resides staring @0x0 address. Vmalloc area starts either at the end of Physical ram size or at 896M. This 896M cap is mandated to ensure that minimum of 128MB is reserved as vmalloc_reserve for vmalloc,kmap etc.
Is the understanding correct? Now trying to map Physical Zones into this 1GB address space
Initial 16MB is mapped to ZONE_DMA
16MB - 896MB is mapped to ZONE_NORMAL
896MB - 1024MB is mapped to ZONE_HIGHMEM
Does this mean that Kernel image is residing in ZONE_DMA area? Any call to vmalloc() in kernel code will return address beyond 896M? insmod of any LKM will internally invoke vmalloc() to obtain contiguous area - where will this code physically located along with rest of kernel code in ZONE_DMA or in ZONE_HIGHMEM?
the function terminates if no key is pressed for 10 consecutive seconds. I tried using the -t option as suggested in some forums, but my version of showkey doesn't have the option of changing the timeout. The options I get are:
-h --helpdisplay this help text
-a --asciidisplay the decimal/octal/hex values of the keys
-s --scancodesdisplay only the raw scan-codes
-k --keycodesdisplay only the interpreted keycodes (default).
Is it possible to write a script to use this function and still keep the function active until an interrupt is recieved?
I am using FC9, I want to write a module that will always show current time after booting.But for that I need not only to load module using insmod/modprobe, but also to compile that module during boot time.How can I perform this 2 steps correctly.
View 11 Replies View RelatedWe are doing a project related to clock synchronisation. We have two laptops: Compaq and IBM Thinkpad. If we adjust the clocks of two laptops to same time in HH:MM:SS using datefunction, in about half an hour, both the clock drift by about 10-15 min We are wondering how this is possible???We have compiled kernel 2.6.36.2 on both laptops and set the value of HZ to 1000. Then what is the reason for such a significant drift in short interval of time??Is this related to crystal oscillator or anything else?
View 5 Replies View RelatedI have Ubuntu running as a Virtualbox, and every time it upgrades the kernel, the Guest Additions stop working.The install process in Linux requires using a virtual CD, running scripts from the command line, etc.Is there any way to keep the guest additions constantly working even when the kernel is upgraded? Can they be installed as Ubuntu packages instead of installing off the virtual CD?
View 2 Replies View Relatedinstall Xenomai on real-time kernel (With PREEMPT_RT)?
View 1 Replies View RelatedI have a system running openSUSE 11.2 with Desktop and XEN kernel, as well as Windows 7 (not by choice though...). I have noticed a strange time issue, with Windows 7 and the desktop kernel the time is correct (like for example now: 1:32 PM) but in the XEN kernel it is ahead several hours (6:32 PM). If it was an issue between openSUSE and windows then I would think that it is a problem with the system clock but I don't know what would cause a time issue between kernels like that.
View 6 Replies View RelatedI am trying to get the time of my wall clock from my wireless driver in form of "hh:mm:ss", so I used the function get_rtc_time() inside my driver to get that and it was done. My question: Is it possible to increase the accuracy of this function, for example if I want to get the milliseconds and the Microseconds in additional to the first output? If not, Is there any other function can do that?
View 3 Replies View Related