diff --git a/tools/apriori/prelinkmap.c b/tools/apriori/prelinkmap.c
new file mode 100644
index 0000000..739c181
--- /dev/null
+++ b/tools/apriori/prelinkmap.c
@@ -0,0 +1,139 @@
+#include <prelinkmap.h>
+#include <debug.h>
+#include <errno.h>
+#include <string.h>
+#include <libgen.h>
+#include <ctype.h>
+
+typedef struct mapentry mapentry;
+
+struct mapentry
+{
+    mapentry *next;
+    unsigned base;
+    char name[0];
+};
+
+static mapentry *maplist = 0;
+
+/* These values limit the address range within which we prelinked libraries
+   reside.  The limit is not set in stone, but should be observed in the 
+   prelink map, or the prelink step will fail.
+*/
+
+#define PRELINK_MIN 0x90000000
+#define PRELINK_MAX 0xB0000000
+
+void pm_init(const char *file)
+{
+    unsigned line = 0;
+    char buf[256];
+    char *x;
+    unsigned n;
+    FILE *fp;
+    mapentry *me;
+    unsigned last = -1UL;
+    
+    fp = fopen(file, "r");
+    FAILIF(fp == NULL, "Error opening file %s: %s (%d)\n", 
+           file, strerror(errno), errno);
+
+    while(fgets(buf, 256, fp)){
+        x = buf;
+        line++;
+        
+        /* eat leading whitespace */
+        while(isspace(*x)) x++;
+
+        /* comment or blank line? skip! */
+        if(*x == '#') continue;
+        if(*x == 0) continue;
+
+        /* skip name */
+        while(*x && !isspace(*x)) x++;
+
+        if(*x) {
+            *x++ = 0;
+            /* skip space before address */
+            while(*x && isspace(*x)) x++;
+        }
+
+        /* no address? complain. */
+        if(*x == 0) {
+            fprintf(stderr,"warning: %s:%d no base address specified\n",
+                    file, line);
+            continue;
+        }
+        
+        n = strtoul(x, 0, 16);
+        /* Note that this is not the only bounds check.  If a library's size
+           exceeds its slot as defined in the prelink map, the prelinker will
+           exit with an error.  See pm_report_library_size_in_memory().
+        */
+        FAILIF((n < PRELINK_MIN) || (n > PRELINK_MAX),
+               "%s:%d base 0x%08x out of range.\n",
+               file, line, n);
+        
+        me = malloc(sizeof(mapentry) + strlen(buf) + 1);
+        FAILIF(me == NULL, "Out of memory parsing %s\n", file);
+
+        FAILIF(last <= n, "The prelink map is not in descending order "
+               "at entry %s (%08x)!\n", buf, n);
+        last = n;
+        
+        me->base = n;
+        strcpy(me->name, buf);
+        me->next = maplist;
+        maplist = me;        
+    }
+
+    fclose(fp);
+}
+
+/* apriori() calls this function when it determine the size of a library 
+   in memory.  pm_report_library_size_in_memory() makes sure that the library
+   fits in the slot provided by the prelink map.
+*/
+void pm_report_library_size_in_memory(const char *name,
+                                      off_t fsize)
+{
+    char *x;
+    mapentry *me;
+    
+    x = strrchr(name,'/');
+    if(x) name = x+1;
+
+    for(me = maplist; me; me = me->next){
+        if(!strcmp(name, me->name)) {
+            off_t slot = me->next ? me->next->base : PRELINK_MAX;
+            slot -= me->base;
+            FAILIF(fsize > slot,
+                   "prelink map error: library %s@0x%08x is too big "
+                   "at %lld bytes, it runs %lld bytes into "
+                   "library %s@0x%08x!\n",
+                   me->name, me->base, fsize, fsize - slot,
+                   me->next->name, me->next->base);
+            break;
+        }
+    }
+    
+    FAILIF(!me,"library '%s' not in prelink map\n", name);
+}
+
+unsigned pm_get_next_link_address(const char *lookup_name)
+{
+    char *x;
+    mapentry *me;
+    
+    x = strrchr(lookup_name,'/');
+    if(x) lookup_name = x+1;
+    
+    for(me = maplist; me; me = me->next){
+        if(!strcmp(lookup_name, me->name)) {
+            return me->base;
+        }
+    }
+    
+    FAILIF(1==1,"library '%s' not in prelink map\n", lookup_name);
+    return 0;
+}