create a kernel buffer from user-level

[Dave Jones]

On Thu, Dec 06, 2007 at 03:06:54PM -0600, Feng Xian wrote:
 > I am doing a project related to thread scheduling. This project needs
 > communication between kernel and user-level applications. Basically, the
 > user-level application sets or unset a bit in a bit vector, according to the
 > application's status (this part is not related to this question, so I skip
 > it). Then the kernel reads the bit vector everytime it schedules a thread.
 > My question is where to allocate the bit vector.
 > 1. If I allocate the bit vector in user-level, then everytime the kernel
 > wants to read the bit vector, I has to do a copy_from_user(). I tried this
 > solution, this incurs a lot of overhead and also crash the os. Since the
 > copy_from_user() needs to look up the virtual address which corresponds to
 > the starting address of bit-vector, it will cause paging in the middle of
 > scheduling. Is there any other way that the kernel can directly access
 > user-level space without doing copying and address translation?
 > 
 > 2. If I allocate the bit vector directly in the kernel space. How can I do
 > this? Is it possible to create an extra system call that allows user-level
 > program to allocate a kernel buffer?
 > 
 > Could anyone help me out on this? Thanks!

Try the kernelnewbies list at http://kernelnewbies.org/ML
or linux-kernel at vger.kernel.org.

Your problem isn't related specifically to the Fedora kernel, so is
off-topic here.

	Dave

-- 
http://www.codemonkey.org.uk