General :: Difference Between User And Kernel Space?
Jul 12, 2010what difference between user and kernel space.
View 2 Replieswhat difference between user and kernel space.
View 2 RepliesLogical 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 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 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?
measure kernel space time and user space time?
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 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.
How 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.
I 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 RelatedI 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 RelatedIf the calling process passes me the virtual address of an its array for example, how can I access it without using copy_from_user?
View 2 Replies View RelatedWhat is the difference between creating a "regular" user and creating a "system" user on Linux?
For example:
Code:
adduser john
Code:
adduser --system john
Similarly it seems there are normal groups and system groups. Doing an internet search and reading man pages does not give much information on the whole concept of system and regular user/group.
I am writing a program which i dont want the kernel scheduler to preempt before certain time duration. I am using the system call sched_get_priority_max to set the maximum priority. However it is not producing results.
View 3 Replies View RelatedIn a 32-bit system, max memory addressable is 4GB. Now Linux kernel does memory mapping division of 1GB for kernel address space and 3GB for user address space. That means 4GB of virtual address space is divided between kernel (1GB) and user (3GB).
Q1. All virtual mapping utilizes the available physical RAM without any division? I mean to say that if RAM is 512MB then a page in kernel space can lie any where RAM (leave aside old PCI dma accesses)? (How this fits to fact that kernel memory is non-pageble)
Q2. If a process is created in user space, it has visibility 4GB address space or 3GB address space?
I have a big partition ext3 and System Monitor show me that there are 14Gb of Free space but only 4Gb of Available space.
View 4 Replies View RelatedCan a sudo user do everything what a root user can do? I read sometimes expert say "You should run it as root rather than sudo user".
View 14 Replies View RelatedWhat's the difference between user permissions & users rights in linux.
View 1 Replies View RelatedI am the new child of the linux world. What is the difference and working functions between kernel and shell..
View 5 Replies View RelatedWhat is the difference between kernel-source.x.x.x.x.rpm and kernel.x.x.x.src.rpm?
View 2 Replies View RelatedIt sounds like he's making a difference between the kernel "source code" and the kernel itself(as in the downloaded file/ files) but the way he talks about both is the same.So then, if one had already "installed" the "kernel sources code," why would he need the "tarball with the newest Linux kernel?" He's already "installed" a kernel, right?
View 3 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
I hope this is the right place to post to because I haven't found any other related forums.I'm working on an AMD opteron running Linux 2.6.28.6 I want to preload a hardware performance counter (register) with a value to have it overflow after a number of a specific event counts. As I understand, when the counter in the register overflows, an interrupt will be generated and handled by the appropriate interrupt handler. How can my user-level application get notified whenever the interrupt occurs? I want to obtain information on the instruction that caused the overflow. Is this possible? I think this is different than responding to signals with sigaction().
View 1 Replies View RelatedI 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 Replies View Relatedaccording to the system manager of my machine, one of my ext4 partitions (home folder) reads 7.6GB free but only 574MB available and the disks "fills" when the 574MB are used, and i'm really needing those 7G right now, so:
why does this happen? are those 7G used in anything? any way to allow the system use that free space?
cusexmp, the example of CUSE program, works. Is there real programs that makes use of it? For example, a thing that just mirrors other character device or thing that allows networked character devices.
View 1 Replies View RelatedI've been looking to get some torrent downloads running on school servers, but I obviously can't install a torrent client because I don't have root (and by extent, can't run anything requiring root privileges). Servers are running various versions of Red Hat (at least the x86_64 ones are, I don't want to recompile if I don't have to). Google has failed me thus far.
View 13 Replies View RelatedI have installed CentOS 5.4 & am trying to install VirtualBox on it. To install VirtualBox I run the command:
yum localinstall path/Virtualbox.rpm
It runs through the dependency check & says everything is fine. It installs the rpm & then says that compiling of the kernel module failed & that VirtualBox will not start until this is fixed, & that the most like cause is that the kernel sources are not installed.
I have installed the kernel-devel package & have the kernel source tree located at /usr/src/kernel/2.6....
I have written a programme in gcc
#include <time.h>
#include <stdio.h>
int main(void)
[code]...
There are some user-space based NFS clients (e.g. NFS Client library). Can I bypass file permissions by using such client? code...
Client1 uses usual NFS client (kernel-mode based) and user1@client1 can read only file1, but not file2.
As I understand, client1 sends uid in nfs request, server1 do a permissions check based on the request data. So, I suggest this is possible to have a client2:
Client2 uses user-space client, and hacker@client2 knows uids of user1 and user2; If he wants to read file1 he can send uid of user1; if he wants to read file2, he sends uid of user2.
Is the scheme possible?