xen: implement the privcmd user-space device

This device is only attached to priviledged domains, and allows the
toolstack to interact with Xen. The two functions of the privcmd
interface is to allow the execution of hypercalls from user-space, and
the mapping of foreign domain memory.

Sponsored by: Citrix Systems R&D

i386/include/xen/hypercall.h:
amd64/include/xen/hypercall.h:
 - Introduce a function to make generic hypercalls into Xen.

xen/interface/xen.h:
xen/interface/memory.h:
 - Import the new hypercall XENMEM_add_to_physmap_range used by
   auto-translated guests to map memory from foreign domains.

dev/xen/privcmd/privcmd.c:
 - This device has the following functions:
   - Allow user-space applications to make hypercalls into Xen.
   - Allow user-space applications to map memory from foreign domains,
     this is accomplished using the newly introduced hypercall
     (XENMEM_add_to_physmap_range).

xen/privcmd.h:
 - Public ioctl interface for the privcmd device.

x86/xen/hvm.c:
 - Remove declaration of hypercall_page, now it's declared in
   hypercall.h.

conf/files:
 - Add the privcmd device to the build process.

1 files changed, 22 insertions, 0 deletions

diff --git a/sys/amd64/include/xen/hypercall.h b/sys/amd64/include/xen/hypercall.h
index 499fb4d..594ffd2 100644
--- a/sys/amd64/include/xen/hypercall.h
+++ b/sys/amd64/include/xen/hypercall.h
@@ -45,6 +45,8 @@
 # error "please don't include this file directly"
 #endif
 
+extern char *hypercall_page;
+
 #define __STR(x) #x
 #define STR(x) __STR(x)
 #define	ENOXENSYS	38
@@ -134,6 +136,26 @@
 	__res;							\
 })
 
+static inline int
+privcmd_hypercall(long op, long a1, long a2, long a3, long a4, long a5)
+{
+	int __res;
+	long __ign1, __ign2, __ign3;
+	register long __arg4 __asm__("r10") = (long)(a4);
+	register long __arg5 __asm__("r8") = (long)(a5);
+	long __call = (long)&hypercall_page + (op * 32);
+
+	__asm__ volatile (
+		"call *%[call]"
+		: "=a" (__res), "=D" (__ign1), "=S" (__ign2),
+		  "=d" (__ign3), "+r" (__arg4), "+r" (__arg5)
+		: "1" ((long)(a1)), "2" ((long)(a2)),
+		  "3" ((long)(a3)), [call] "a" (__call)
+		: "memory" );
+
+	return (__res);
+}
+
 static inline int __must_check
 HYPERVISOR_set_trap_table(
 	const trap_info_t *table)