8287686: Add assertion to ensure that disarm value offset < 128

zhengyu123 · zhengyu123 · commit a75299c3ab95 · 2022-06-03T12:18:36.000Z
Reviewed-by: tschatzl, shade
diff --git a/src/hotspot/share/runtime/thread.hpp b/src/hotspot/share/runtime/thread.hpp
@@ -158,7 +158,11 @@ class Thread: public ThreadShadow {
   }
 
   static ByteSize nmethod_disarmed_offset() {
-    return byte_offset_of(Thread, _nmethod_disarm_value);
+    ByteSize offset = byte_offset_of(Thread, _nmethod_disarm_value);
+    // At least on x86_64, nmethod entry barrier encodes disarmed value offset
+    // in instruction as disp8 immed
+    assert(in_bytes(offset) < 128, "Offset >= 128");
+    return offset;
   }
 
  private:

Original file line number	Diff line number	Diff line change
`@@ -158,7 +158,11 @@ class Thread: public ThreadShadow {`
`158`	`158`	`}`
`159`	`159`
`160`	`160`	`static ByteSize nmethod_disarmed_offset() {`
`161`		`- return byte_offset_of(Thread, _nmethod_disarm_value);`
	`161`	`+ ByteSize offset = byte_offset_of(Thread, _nmethod_disarm_value);`
	`162`	`+ // At least on x86_64, nmethod entry barrier encodes disarmed value offset`
	`163`	`+ // in instruction as disp8 immed`
	`164`	`+ assert(in_bytes(offset) < 128, "Offset >= 128");`
	`165`	`+ return offset;`
`162`	`166`	`}`
`163`	`167`
`164`	`168`	`private:`