Split off sys_umap_remote from sys_umap

sys_umap now supports only:
- looking up the physical address of a virtual address in the address space
  of the caller;
- looking up the physical address of a grant for which the caller is the
  grantee.

This is enough for nearly all umap users. The new sys_umap_remote supports
lookups in arbitrary address spaces and grants for arbitrary grantees.

lib/libsys/Makefile

@@ -97,6 +97,7 @@ SRCS=  \
 	sys_times.c \
 	sys_trace.c \
 	sys_umap.c \
+	sys_umap_remote.c \
 	sys_update.c \
 	sys_vinb.c \
 	sys_vinl.c \

lib/libsys/sys_umap_remote.c

@@ -0,0 +1,35 @@
+#include "syslib.h"
+
+/*===========================================================================*
+ *                                sys_umap_remote			     *
+ *===========================================================================*/
+PUBLIC int sys_umap_remote(proc_ep, grantee, seg, vir_addr, bytes, phys_addr)
+endpoint_t proc_ep;			/* process number to do umap for */
+endpoint_t grantee;			/* process nr to check as grantee */
+int seg;				/* T, D, or S segment */
+vir_bytes vir_addr;			/* address in bytes with segment*/
+vir_bytes bytes;			/* number of bytes to be copied */
+phys_bytes *phys_addr;			/* placeholder for result */
+{
+    message m;
+    int result;
+
+    /* Note about the grantee parameter:
+     * - Is ignored for non-grant umap calls, but should be SELF to
+     *   pass the sanity check in that case;
+     * - May be SELF to get the same behaviour as sys_umap, namely that the
+     *   caller must be the grantee;
+     * - In all other cases, should be a valid endpoint (neither ANY nor NONE).
+     */
+
+    m.CP_SRC_ENDPT = proc_ep;
+    m.CP_DST_ENDPT = grantee;
+    m.CP_SRC_SPACE = seg;
+    m.CP_SRC_ADDR = vir_addr;
+    m.CP_NR_BYTES = bytes;
+
+    result = _kernel_call(SYS_UMAP_REMOTE, &m);
+    *phys_addr = m.CP_DST_ADDR;
+    return(result);
+}
+