diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index 3377376f158d..59a6ca8839f6 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -156,6 +156,11 @@ static void get_fpcontext(struct thread *td, mcontext_t *mcp);
 static int  set_fpcontext(struct thread *td, const mcontext_t *mcp);
 SYSINIT(cpu, SI_SUB_CPU, SI_ORDER_FIRST, cpu_startup, NULL);
 
+/*
+ * The file "conf/ldscript.amd64" defines the symbol "kernphys".  Its value is
+ * the physical address at which the kernel is loaded.
+ */
+extern char kernphys[];
 #ifdef DDB
 extern vm_offset_t ksym_start, ksym_end;
 #endif
@@ -1417,7 +1422,7 @@ getmemsize(caddr_t kmdp, u_int64_t first)
 			/*
 			 * block out kernel memory as not available.
 			 */
-			if (pa >= 0x100000 && pa < first)
+			if (pa >= (vm_paddr_t)kernphys && pa < first)
 				goto do_dump_avail;
 
 			/*
diff --git a/sys/conf/ldscript.amd64 b/sys/conf/ldscript.amd64
index ce275ef6c365..9210a730c30e 100644
--- a/sys/conf/ldscript.amd64
+++ b/sys/conf/ldscript.amd64
@@ -6,7 +6,8 @@ SEARCH_DIR("/usr/lib");
 SECTIONS
 {
   /* Read-only sections, merged into text segment: */
-  . = kernbase + CONSTANT (MAXPAGESIZE) + SIZEOF_HEADERS;
+  kernphys = CONSTANT (MAXPAGESIZE);
+  . = kernbase + kernphys + SIZEOF_HEADERS;
   .interp         : { *(.interp) }
   .hash           : { *(.hash) }
   .gnu.hash       : { *(.gnu.hash) }