Add logic for patching calls to the x86-64 vsyscall page

tests/test_patching_input.S

Index: tests/test_patching_input.S
diff --git a/tests/test_patching_input.S b/tests/test_patching_input.S
index 3e7126d331b1611c792c1496728f0263c223b17b..e2406035d57c8f325c823a307e34c970851ec1b4 100644
--- a/tests/test_patching_input.S
+++ b/tests/test_patching_input.S
@@ -22,5 +22,43 @@ my_getpid:
         ret
 my_getpid_end:
 
+
+        // These routines call the vsyscall page, which is present on
+        // x86-64 only.
+
+#if defined(__x86_64__)
+
+        .global my_vgettimeofday
+        .global my_vgettimeofday_end
+my_vgettimeofday:
+        sub $8, %rsp  // Align the stack
+        mov $0xffffffffff600000, %rax
+        call *%rax
+        add $8, %rsp
+        ret
+my_vgettimeofday_end:
+
+        .global my_vtime
+        .global my_vtime_end
+my_vtime:
+        sub $8, %rsp  // Align the stack
+        mov $0xffffffffff600400, %rax
+        call *%rax
+        add $8, %rsp
+        ret
+my_vtime_end:
+
+        .global my_vgetcpu
+        .global my_vgetcpu_end
+my_vgetcpu:
+        sub $8, %rsp  // Align the stack
+        mov $0xffffffffff600800, %rax
+        call *%rax
+        add $8, %rsp
+        ret
+my_vgetcpu_end:
+
+#endif
+
         // Tell Linux not to disable no-execute protection for the process.
         .section .note.GNU-stack,"",@progbits