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Diffstat (limited to 'arch/x86/include/asm/lguest_hcall.h')
-rw-r--r--arch/x86/include/asm/lguest_hcall.h29
1 files changed, 23 insertions, 6 deletions
diff --git a/arch/x86/include/asm/lguest_hcall.h b/arch/x86/include/asm/lguest_hcall.h
index ba0eed8aa1a6..b60f2924c413 100644
--- a/arch/x86/include/asm/lguest_hcall.h
+++ b/arch/x86/include/asm/lguest_hcall.h
@@ -28,22 +28,39 @@
#ifndef __ASSEMBLY__
#include <asm/hw_irq.h>
-#include <asm/kvm_para.h>
/*G:030
* But first, how does our Guest contact the Host to ask for privileged
* operations? There are two ways: the direct way is to make a "hypercall",
* to make requests of the Host Itself.
*
- * We use the KVM hypercall mechanism, though completely different hypercall
- * numbers. Seventeen hypercalls are available: the hypercall number is put in
- * the %eax register, and the arguments (when required) are placed in %ebx,
- * %ecx, %edx and %esi. If a return value makes sense, it's returned in %eax.
+ * Our hypercall mechanism uses the highest unused trap code (traps 32 and
+ * above are used by real hardware interrupts). Seventeen hypercalls are
+ * available: the hypercall number is put in the %eax register, and the
+ * arguments (when required) are placed in %ebx, %ecx, %edx and %esi.
+ * If a return value makes sense, it's returned in %eax.
*
* Grossly invalid calls result in Sudden Death at the hands of the vengeful
* Host, rather than returning failure. This reflects Winston Churchill's
* definition of a gentleman: "someone who is only rude intentionally".
-:*/
+ */
+static inline unsigned long
+hcall(unsigned long call,
+ unsigned long arg1, unsigned long arg2, unsigned long arg3,
+ unsigned long arg4)
+{
+ /* "int" is the Intel instruction to trigger a trap. */
+ asm volatile("int $" __stringify(LGUEST_TRAP_ENTRY)
+ /* The call in %eax (aka "a") might be overwritten */
+ : "=a"(call)
+ /* The arguments are in %eax, %ebx, %ecx, %edx & %esi */
+ : "a"(call), "b"(arg1), "c"(arg2), "d"(arg3), "S"(arg4)
+ /* "memory" means this might write somewhere in memory.
+ * This isn't true for all calls, but it's safe to tell
+ * gcc that it might happen so it doesn't get clever. */
+ : "memory");
+ return call;
+}
/* Can't use our min() macro here: needs to be a constant */
#define LGUEST_IRQS (NR_IRQS < 32 ? NR_IRQS: 32)
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