diff --git a/tools/libs/foreignmemory/compat.c b/tools/libs/foreignmemory/compat.c
index 039297cb0c..b79ec1a9e7 100644
--- a/tools/libs/foreignmemory/compat.c
+++ b/tools/libs/foreignmemory/compat.c
@@ -22,8 +22,8 @@
 #include "private.h"
 
 void *osdep_xenforeignmemory_map(xenforeignmemory_handle *fmem,
-                                 uint32_t dom, int prot,
-                                 const xen_pfn_t *arr, int *err, size_t num)
+                                 uint32_t dom, int prot, size_t num,
+                                 const xen_pfn_t arr[/*num*/], int err[/*num*/])
 {
     xen_pfn_t *pfn;
     unsigned int i;
diff --git a/tools/libs/foreignmemory/core.c b/tools/libs/foreignmemory/core.c
index 4e0541f7cd..cfb0a7373d 100644
--- a/tools/libs/foreignmemory/core.c
+++ b/tools/libs/foreignmemory/core.c
@@ -64,7 +64,8 @@ int xenforeignmemory_close(xenforeignmemory_handle *fmem)
 
 void *xenforeignmemory_map(xenforeignmemory_handle *fmem,
                            uint32_t dom, int prot,
-                           const xen_pfn_t *arr, int *err, size_t num)
+                           size_t num,
+                           const xen_pfn_t arr[/*num*/], int err[/*num*/])
 {
     void *ret;
     int *err_to_free = NULL;
@@ -75,7 +76,7 @@ void *xenforeignmemory_map(xenforeignmemory_handle *fmem,
     if ( err == NULL )
         return NULL;
 
-    ret = osdep_xenforeignmemory_map(fmem, dom, prot, arr, err, num);
+    ret = osdep_xenforeignmemory_map(fmem, dom, prot, num, arr, err);
 
     if ( ret == 0 && err_to_free )
     {
diff --git a/tools/libs/foreignmemory/freebsd.c b/tools/libs/foreignmemory/freebsd.c
index ed26ebb8fe..703754f598 100644
--- a/tools/libs/foreignmemory/freebsd.c
+++ b/tools/libs/foreignmemory/freebsd.c
@@ -84,8 +84,8 @@ int osdep_xenforeignmemory_close(xenforeignmemory_handle *fmem)
 
 void *osdep_xenforeignmemory_map(xenforeignmemory_handle *fmem,
                                  uint32_t dom, int prot,
-                                 const xen_pfn_t *arr, int *err,
-                                 size_t num)
+                                 size_t num,
+                                 const xen_pfn_t arr[/*num*/], int err[/*num*/])
 {
     int fd = fmem->fd;
     privcmd_mmapbatch_t ioctlx;
diff --git a/tools/libs/foreignmemory/include/xenforeignmemory.h b/tools/libs/foreignmemory/include/xenforeignmemory.h
index 0ec6325f9b..3724c63b26 100644
--- a/tools/libs/foreignmemory/include/xenforeignmemory.h
+++ b/tools/libs/foreignmemory/include/xenforeignmemory.h
@@ -104,8 +104,8 @@ int xenforeignmemory_close(xenforeignmemory_handle *fmem);
  * of @err indicating failure to map every page.
  */
 void *xenforeignmemory_map(xenforeignmemory_handle *fmem, uint32_t dom,
-                           int prot, const xen_pfn_t *arr, int *err,
-                           size_t pages);
+                           int prot, size_t pages,
+                           const xen_pfn_t arr[/*pages*/], int err[/*pages*/]);
 
 /*
  * Unmap a mapping previous created with xenforeignmemory_map().
diff --git a/tools/libs/foreignmemory/linux.c b/tools/libs/foreignmemory/linux.c
index 66203911ed..32b6defa1b 100644
--- a/tools/libs/foreignmemory/linux.c
+++ b/tools/libs/foreignmemory/linux.c
@@ -161,7 +161,8 @@ out:
 
 void *osdep_xenforeignmemory_map(xenforeignmemory_handle *fmem,
                                  uint32_t dom, int prot,
-                                 const xen_pfn_t *arr, int *err, size_t num)
+                                 size_t num,
+                                 const xen_pfn_t arr[/*num*/], int err[/*num*/])
 {
     int fd = fmem->fd;
     privcmd_mmapbatch_v2_t ioctlx;
diff --git a/tools/libs/foreignmemory/minios.c b/tools/libs/foreignmemory/minios.c
index bdc1239461..ca5ba7181e 100644
--- a/tools/libs/foreignmemory/minios.c
+++ b/tools/libs/foreignmemory/minios.c
@@ -41,7 +41,8 @@ int osdep_xenforeignmemory_close(xenforeignmemory_handle *fmem)
 
 void *osdep_xenforeignmemory_map(xenforeignmemory_handle *fmem,
                                  uint32_t dom, int prot,
-                                 const xen_pfn_t *arr, int *err, size_t num)
+                                 size_t num,
+                                 const xen_pfn_t arr[/*num*/], int err[/*num*/])
 {
     unsigned long pt_prot = 0;
     if (prot & PROT_READ)
diff --git a/tools/libs/foreignmemory/private.h b/tools/libs/foreignmemory/private.h
index 36a71ecc84..cd732fdf48 100644
--- a/tools/libs/foreignmemory/private.h
+++ b/tools/libs/foreignmemory/private.h
@@ -27,7 +27,8 @@ int osdep_xenforeignmemory_close(xenforeignmemory_handle *fmem);
 
 void *osdep_xenforeignmemory_map(xenforeignmemory_handle *fmem,
                                  uint32_t dom, int prot,
-                                 const xen_pfn_t *arr, int *err, size_t num);
+                                 size_t num,
+                                 const xen_pfn_t arr[num], int err[num]);
 int osdep_xenforeignmemory_unmap(xenforeignmemory_handle *fmem,
                                  void *addr, size_t num);
 
diff --git a/tools/libxc/xc_foreign_memory.c b/tools/libxc/xc_foreign_memory.c
index 4b24388980..4053d26851 100644
--- a/tools/libxc/xc_foreign_memory.c
+++ b/tools/libxc/xc_foreign_memory.c
@@ -28,7 +28,7 @@ void *xc_map_foreign_pages(xc_interface *xch, uint32_t dom, int prot,
         return NULL;
     }
 
-    return xenforeignmemory_map(xch->fmem, dom, prot, arr, NULL, num);
+    return xenforeignmemory_map(xch->fmem, dom, prot, num, arr, NULL);
 }
 
 void *xc_map_foreign_range(xc_interface *xch,
@@ -84,7 +84,7 @@ void *xc_map_foreign_ranges(xc_interface *xch,
 void *xc_map_foreign_bulk(xc_interface *xch, uint32_t dom, int prot,
                           const xen_pfn_t *arr, int *err, unsigned int num)
 {
-    return xenforeignmemory_map(xch->fmem, dom, prot, arr, err, num);
+    return xenforeignmemory_map(xch->fmem, dom, prot, num, arr, err);
 }
 
 /*
diff --git a/tools/libxc/xc_sr_restore.c b/tools/libxc/xc_sr_restore.c
index 5a51f262bc..d4d33fda76 100644
--- a/tools/libxc/xc_sr_restore.c
+++ b/tools/libxc/xc_sr_restore.c
@@ -318,7 +318,7 @@ static int process_page_data(struct xc_sr_context *ctx, unsigned count,
 
     mapping = guest_page = xenforeignmemory_map(xch->fmem,
         ctx->domid, PROT_READ | PROT_WRITE,
-        mfns, map_errs, nr_pages);
+        nr_pages, mfns, map_errs);
     if ( !mapping )
     {
         rc = -1;
diff --git a/tools/libxc/xc_sr_save.c b/tools/libxc/xc_sr_save.c
index fba4e40eb0..ccb000e74c 100644
--- a/tools/libxc/xc_sr_save.c
+++ b/tools/libxc/xc_sr_save.c
@@ -154,7 +154,7 @@ static int write_batch(struct xc_sr_context *ctx)
     if ( nr_pages > 0 )
     {
         guest_mapping = xenforeignmemory_map(xch->fmem,
-            ctx->domid, PROT_READ, mfns, errors, nr_pages);
+            ctx->domid, PROT_READ, nr_pages, mfns, errors);
         if ( !guest_mapping )
         {
             PERROR("Failed to map guest pages");