Re: [uml-devel] Segmentation fault with kernel thread in UML-2.6.7 TT mode

[Jeff Dike <jdike@addtoit.com>]

On Sun, Jul 17, 2005 at 03:52:46PM +0800, Alex LIU wrote:
> In fact I want to port Bproc to UML. Now Bproc is based on i386. And
> a part of the main work Bproc does is about the kernel thread...Bproc
> create a new kernel thread function with the name bproc_kernel_thread
> in i386 and let the Bproc kernel thread go to the user space rather
> than exit. 

What does it run when it enters userspace?  The only other thing I can
think of which does this is the kernel thread that turns into init,
which it does by calling exec.

> In UML,I found in finish_fork_handler, set_user_mode is called at
> last. I think it's purpose is to let the new forked process go to
> the user space like ret_from_fork in i386. 

If you look at its implementation, you'll see that it is very tt-mode 
specific, and thus can't do something as basic as re-entering
userspace in a generic way.

If you are entering userspace, you need for there to be something
there to enter.

				Jeff


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