Messages in this thread | | | Date | Wed, 14 Feb 2007 17:01:04 -0800 (PST) | From | Davide Libenzi <> | Subject | Re: [patch 05/11] syslets: core code |
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On Wed, 14 Feb 2007, Ingo Molnar wrote:
> yeah, that's another key thing. I do plan to provide a sys_upcall() > syscall as well which calls a 5-parameter user-space function with a > special stack. (it's like a lightweight signal/event handler, without > any of the signal handler legacies and overhead - it's like a reverse > system call - a "user call". Obviously pure userspace would never use > sys_upcall(), unless as an act of sheer masochism.)
That is exactly what I described as clets. Instead of having complex jump and condition interpreters on the kernel (on top of new syscalls to modify/increment userspace variables), you just code it in C and you pass the clet pointer to the kernel. The upcall will setup a frame, execute the clet (where jump/conditions and userspace variable changes happen in machine code - gcc is pretty good in taking care of that for us) on its return, come back through a sys_async_return, and go back to userspace.
- Davide
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