[uml-devel] Kernel access to user memory in SKAS

[Bryan P. <pa...@cm...>]

Hi,

	I'm interested in mediating accesses by the UML guest kernel to  
memory used by the UML guest processes.  At present, I'm looking at a  
scenario using SKAS3, so the kernel has an address space distinct  
from that of the user processes.  I guess I'm a bit confused as to  
how the guest kernel actually manages to touch guest process memory  
(e.g., for copying system call arguments).  Looking through /arch/um/ 
kernel/skas/uaccess.c, it appears that all of these accesses devolve  
to performing a strncpy or memcpy, but I don't see a translation from  
an address in the user's address space to one in the kernel's address  
space.  Does this happen somewhere else, or am I misunderstanding  
SKAS?  Looking through the documentation on the site, I was unable to  
find any diagrams or explanations for how the guest kernel actually  
lays out memory in its address space.  Any comments or suggestions  
would be greatly appreciated!


                        Bryan