Index: sys/amd64/amd64/elf_machdep.c
===================================================================
--- sys/amd64/amd64/elf_machdep.c	(revision 320570)
+++ sys/amd64/amd64/elf_machdep.c	(working copy)
@@ -77,7 +77,7 @@
 	.sv_fetch_syscall_args = cpu_fetch_syscall_args,
 	.sv_syscallnames = syscallnames,
 	.sv_shared_page_base = SHAREDPAGE,
-	.sv_shared_page_len = PAGE_SIZE,
+	.sv_shared_page_len = 2*PAGE_SIZE,
 	.sv_schedtail	= NULL,
 	.sv_thread_detach = NULL,
 	.sv_trap	= NULL,
Index: sys/amd64/include/vmparam.h
===================================================================
--- sys/amd64/include/vmparam.h	(revision 320570)
+++ sys/amd64/include/vmparam.h	(working copy)
@@ -176,7 +176,7 @@
 
 #define	VM_MAXUSER_ADDRESS	UVADDR(NUPML4E, 0, 0, 0)
 
-#define	SHAREDPAGE		(VM_MAXUSER_ADDRESS - PAGE_SIZE)
+#define	SHAREDPAGE		(VM_MAXUSER_ADDRESS - 2*PAGE_SIZE)
 #define	USRSTACK		SHAREDPAGE
 
 #define	VM_MAX_ADDRESS		UPT_MAX_ADDRESS
Index: sys/amd64/linux/linux_sysvec.c
===================================================================
--- sys/amd64/linux/linux_sysvec.c	(revision 320570)
+++ sys/amd64/linux/linux_sysvec.c	(working copy)
@@ -823,7 +823,7 @@
 	.sv_fetch_syscall_args = linux_fetch_syscall_args,
 	.sv_syscallnames = NULL,
 	.sv_shared_page_base = SHAREDPAGE,
-	.sv_shared_page_len = PAGE_SIZE,
+	.sv_shared_page_len = 2*PAGE_SIZE,
 	.sv_schedtail	= linux_schedtail,
 	.sv_thread_detach = linux_thread_detach,
 	.sv_trap	= linux_vsyscall,