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Re: [Xen-devel] Hypercall privilege check
> I'm wondering where Xen actually checks whether a hypercall is made
> from ring 1 or ring 3. Could anyone point me out to the code? Any
> pointer would be much appreciated. Thanks!
Hypercalls are made from ring 1. The userspace tools do make hypercalls
sometimes, but they do it by calling a special kernel driver, which then does
the actual hypercall. *actually* what that does is to jump into the
hypercall transfer page at the right location. This page contains the actual
implementation of the hypercall (using this indirection allows future
versions of Xen to supply different implementations of the calls, if
Take a look at:
drivers/xen/privcmd/privcmd.c in the XenLinux tree. This is used by the dom0
tools to do control plane operations.
Also, take a look at: include/asm-i386/mach-xen/asm/hypercall.h which contains
implementations of some other hypercalls.
Dave: Just a question. What use is a unicyle with no seat? And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!
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