On Thu, Apr 20, 2006 at 06:11:41PM +0000, Talib Alim wrote:
> My module pass back pointer to user application when device is opened. From that point, user application request different services from my module.
>
> In order to avoid any lookup overhead, kernel virtual pointer is passed back to user application.
>
> Talib
>
> >On 4/20/06, Talib Alim <talibalm@xxxxxxxxxxx> wrote:
> >> A kernel virtual address is passed to my module. In order to avoid any
> >> chances of a crash, how can I verify this pointer is pointing to a mapped
> >> memory location.
> >
> >Can you elaborate more on this ?
Hi,
I don't know if I have understood : you want to implement a service in
ther kernel and then call it from user space ?
If you want to do that you have 2 main solutions :
_ through system call (you should avoid it, it's recommended
to add new system calls)
_ through a 'device driver'
You should use the second solution.
Traditionnaly, a device driver provides :
_ a read operation
_ a write operation
_ a seek operation
_ ...
_ ioctl
You can then write, read , call other operations of the device.
Here is a good link to learn more about device drivers :
http://lwn.net/Kernel/LDD3/
But you can't use your solution : a kernel pointer is not valid in user
mode. You should read some doc on the virtual memory management and
paging in Linux :
http://www.phptr.com/content/images/0131453483/downloads/gorman_book.pdf
--
tyler
tyler@xxxxxxxx
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