[Xen-devel][Xense-devel][PATCH][XSM][1/4] Xen Security Modules Patch

["George S. Coker, II" <gscoker@xxxxxxxxxxxxxx>]

This patch provides the basic XSM framework for x86_32/x86/64.  It
includes a dummy module that implements call/return for each security
function. 

The hooks implemented by this patch provide a framework for security
modules to interpose and complement the existing privileged hypercall 
operationsin xen as well as interpose on the discretionary operations 
between domains.

I have done very casual performance testing of the XSM in comparison to
native xen.  The XSM (with or without the dummy module) has negligible
impact as measured by lmbench and kbench from either dom0 or domU.  The
tests were conducted on xen running idle dom0's and idle domU's.  The
micro-benchmarks can/do especially vary when a security module (other
than the dummy module) is in place.  This is to be expected.  The macro-
benchmarks for a specific security module tend to average out the micro-
benchmark variations but may not be representative of a real platform
workload.

The framework is configured as default-enable in this patch set.
Configuration of XSM is made in Config.mk.  The only configuration
option is XSM_ENABLE = y/n.  XSM_ENABLE must be y to compile an XSM
module.  

XSM provides a generalized hook infrastructure allowing third-party
security modules to interpose on the Xen code path.  A default or dummy
module provides basic call/return functionality for hooks not
implemented by a given module.  During module initialization, a module
registers its security hooks and the equivalent dummy hooks are
unregistered.  If a module does not implement a hook, the equivalent
dummy hook remains in place.  Modules also may define and register at
boot time a module specific hypercall through the XSM hook
infrastructure.

Modules may also define at Xen compile time a magic number XSM_MAGIC to
indicate that a policy should be discovered from the images loaded at
boot.  The policy file should then be listed in grub as one of the
multi-boot modules after the dom0 kernel.

Signed-off-by: George Coker <gscoker@xxxxxxxxxxxxxx>

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