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diff --git a/sys/xen/interface/kexec.h b/sys/xen/interface/kexec.h
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+++ b/sys/xen/interface/kexec.h
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+/******************************************************************************
+ * kexec.h - Public portion
+ * 
+ * Xen port written by:
+ * - Simon 'Horms' Horman <horms@verge.net.au>
+ * - Magnus Damm <magnus@valinux.co.jp>
+ */
+
+#ifndef _XEN_PUBLIC_KEXEC_H
+#define _XEN_PUBLIC_KEXEC_H
+
+
+/* This file describes the Kexec / Kdump hypercall interface for Xen.
+ *
+ * Kexec under vanilla Linux allows a user to reboot the physical machine 
+ * into a new user-specified kernel. The Xen port extends this idea
+ * to allow rebooting of the machine from dom0. When kexec for dom0
+ * is used to reboot,  both the hypervisor and the domains get replaced
+ * with some other kernel. It is possible to kexec between vanilla
+ * Linux and Xen and back again. Xen to Xen works well too.
+ *
+ * The hypercall interface for kexec can be divided into three main
+ * types of hypercall operations:
+ *
+ * 1) Range information:
+ *    This is used by the dom0 kernel to ask the hypervisor about various 
+ *    address information. This information is needed to allow kexec-tools 
+ *    to fill in the ELF headers for /proc/vmcore properly.
+ *
+ * 2) Load and unload of images:
+ *    There are no big surprises here, the kexec binary from kexec-tools
+ *    runs in userspace in dom0. The tool loads/unloads data into the
+ *    dom0 kernel such as new kernel, initramfs and hypervisor. When
+ *    loaded the dom0 kernel performs a load hypercall operation, and
+ *    before releasing all page references the dom0 kernel calls unload.
+ *
+ * 3) Kexec operation:
+ *    This is used to start a previously loaded kernel.
+ */
+
+#include "xen.h"
+
+#if defined(__i386__) || defined(__x86_64__)
+#define KEXEC_XEN_NO_PAGES 17
+#endif
+
+/*
+ * Prototype for this hypercall is:
+ *  int kexec_op(int cmd, void *args)
+ * @cmd  == KEXEC_CMD_... 
+ *          KEXEC operation to perform
+ * @args == Operation-specific extra arguments (NULL if none).
+ */
+
+/*
+ * Kexec supports two types of operation:
+ * - kexec into a regular kernel, very similar to a standard reboot
+ *   - KEXEC_TYPE_DEFAULT is used to specify this type
+ * - kexec into a special "crash kernel", aka kexec-on-panic
+ *   - KEXEC_TYPE_CRASH is used to specify this type
+ *   - parts of our system may be broken at kexec-on-panic time
+ *     - the code should be kept as simple and self-contained as possible
+ */
+
+#define KEXEC_TYPE_DEFAULT 0
+#define KEXEC_TYPE_CRASH   1
+
+
+/* The kexec implementation for Xen allows the user to load two
+ * types of kernels, KEXEC_TYPE_DEFAULT and KEXEC_TYPE_CRASH.
+ * All data needed for a kexec reboot is kept in one xen_kexec_image_t
+ * per "instance". The data mainly consists of machine address lists to pages
+ * together with destination addresses. The data in xen_kexec_image_t
+ * is passed to the "code page" which is one page of code that performs
+ * the final relocations before jumping to the new kernel.
+ */
+ 
+typedef struct xen_kexec_image {
+#if defined(__i386__) || defined(__x86_64__)
+    unsigned long page_list[KEXEC_XEN_NO_PAGES];
+#endif
+    unsigned long indirection_page;
+    unsigned long start_address;
+} xen_kexec_image_t;
+
+/*
+ * Perform kexec having previously loaded a kexec or kdump kernel
+ * as appropriate.
+ * type == KEXEC_TYPE_DEFAULT or KEXEC_TYPE_CRASH [in]
+ */
+#define KEXEC_CMD_kexec                 0
+typedef struct xen_kexec_exec {
+    int type;
+} xen_kexec_exec_t;
+
+/*
+ * Load/Unload kernel image for kexec or kdump.
+ * type  == KEXEC_TYPE_DEFAULT or KEXEC_TYPE_CRASH [in]
+ * image == relocation information for kexec (ignored for unload) [in]
+ */
+#define KEXEC_CMD_kexec_load            1
+#define KEXEC_CMD_kexec_unload          2
+typedef struct xen_kexec_load {
+    int type;
+    xen_kexec_image_t image;
+} xen_kexec_load_t;
+
+#define KEXEC_RANGE_MA_CRASH 0   /* machine address and size of crash area */
+#define KEXEC_RANGE_MA_XEN   1   /* machine address and size of Xen itself */
+#define KEXEC_RANGE_MA_CPU   2   /* machine address and size of a CPU note */
+
+/*
+ * Find the address and size of certain memory areas
+ * range == KEXEC_RANGE_... [in]
+ * nr    == physical CPU number (starting from 0) if KEXEC_RANGE_MA_CPU [in]
+ * size  == number of bytes reserved in window [out]
+ * start == address of the first byte in the window [out]
+ */
+#define KEXEC_CMD_kexec_get_range       3
+typedef struct xen_kexec_range {
+    int range;
+    int nr;
+    unsigned long size;
+    unsigned long start;
+} xen_kexec_range_t;
+
+#endif /* _XEN_PUBLIC_KEXEC_H */
+
+/*
+ * Local variables:
+ * mode: C
+ * c-set-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */