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open file in kernel space????

Posted on 2002-05-03
Medium Priority
Last Modified: 2008-01-09
Please help me! Can i open file or create socket in kernel space????
Question by:minhtuanq7
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Accepted Solution

bryanh earned 400 total points
ID: 6990680
Yes.  This is a common enough question that I keep an example of it in ftp://giraffe-data.com/pub/filewrite.c .

The example is C source code for a loadable kernel module that writes stuff into a regular file when you attempt to load it.  The load always fails.

It's usually bad design to have the kernel access a regular file, and in fact in Linux the only place I have ever seen it is in the NFS server, and that's pretty much an acknowledged performance hack (i.e. it was meant to be in user space).  But it works.

The key to understanding it is that you can't issue a system call (e.g. write()) from inside the kernel, but you can call the same subroutine that the system call handler does when a user program issues the system call.

Creating sockets is a whole separate question, but the overall strategy is similar.

Expert Comment

ID: 7020299
Have also a look at khttpd, it's in /usr/src/linux/net/khttpd.
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Expert Comment

ID: 9915669
No comment has been added lately, so it's time to clean up this TA.
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