Re: allocate memory in userspace

[Andi Kleen <ak@suse.de>]

Timo Benk <t_benk@web.de> writes:

> I am a kernel newbie and i am writing a module. I 
> need to allocate some memory in userspace because
> i want to access syscalls like open(), lstat() etc.
> I need to call these methods in the kernel, and in
> my special case there is no other way, but i 
> do not want to reimplement all the syscalls.
> 
> I read that it should be possible, but i cannot
> find any example or recipe on how to do it.

mm_segment_t oldfs = get_fs(); 
set_fs(KERNEL_DS); 
ret = sys_yoursyscall(kernelargs ...) 
set_fs(oldfs); 

Do not even think about using mmap or accessing sys_call_table for this.
Your other post was so tasteless that it would be good if you retracted
it with a followup because it would be very bad to have such an bad example 
in the l-k archives open to innocent search machine users uncommented.

-Andi