Re: [LIP] Kernel blues

[Supreet S. <supreet@SDF.LONESTAR.ORG>]

I do'nt know if its of any interset or not but there is a package 
syscalltrack which would probably help in this case.

EIP is IP that is Instruction pointer AFAIK and E in front means Extended 
that is extension to original x86 instruction set.

looking for asbestos undies quickly
etc and supreet





On Tue, Jan 28, 2003 at 09:52:57PM +0530, Dhruv Gami wrote:
> Hi all,
> 
> ive recently ventured into kernel programming, and that too coz i was 
> required to write a module for catching data coming from one program and 
> inserting it in my running module to perform certain checks.
> 
> The idea i used:
> 
> I tried to create a character device (as explained in The Linux Kernel 
> Module Programming Guide from TLDP), by using get_user() and put_user() to 
> interact with the user space. I created a character device (/dev/char_dev) 
> by mknod, providing it with a major number as returned by my module.
> 
> I wrote code for device_open(), device_release(), device_read(), 
> device_write() and device_ioctl(). Now the program compiles and the module 
> gets inserted by insmod. The problem is that im unable to interact with 
> the module. 
> 
> I donot know how to write to the device so as to get data into my module. 
> 
> Also, by tracing the program using printk's ... i discovered that 
> device_open() is NOT being called when a reference is made to it. i wrote 
> a tiny perl script to open() the device, so as to create a reference to 
> it. but 'lsmod' shows a reference count of -1 upon doing so.
> 
> apparently, device_open() is not being called(that increments the 
> reference count), but device_release() is being called TWICE ! thus after 
> every time i run my tiny perl script, the reference count decreases by two 
> and goes deeper into negative numbers.
> 
> Can somebody explain to me how a kernel module works. what is the flow of 
> control in a module ? how can i debug/trace it ?
> 
> Im running kernel 2.4.18-14, on an intel p4 machine.
> 
> i used register_chrdev() to register my device and unregister_chrdev() to 
> unregister it. could there be a problem with this ?
> 
> Also, the dump as shown by the program upon running the perl script says 
> that it has some Null Pointer reference (EIP has a NULL value).... does 
> that mean something ?
> 
> a quick reply with some help or pointers to relevent text would be greatly 
> appreciated. If someone wants a look at the code and error messages, i 
> shall do so in my next mail, as the code is in office and i can send it 
> from there tommorrow.
> 
> thanks,
> 
> regards,
> Gami
> 
> 
> 
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