runtime: precisely scan globals on all platforms

src/runtime/gc_globals_boehm.go

@@ -0,0 +1,20 @@
+//go:build gc.boehm
+
+package runtime
+
+import "unsafe"
+
+func markGlobals() {
+	for i := uintptr(0); i < gcGlobalRootCount(); i++ {
+		addr := gcGlobalRoot(uintptr(i))
+		// GC_push_all queues one range per call and overflows Boehm's mark
+		// stack for programs with thousands of roots. Scan each range now.
+		libgc_push_all_eager(uintptr(addr), uintptr(addr)+gcGlobalRootSize(i))
+	}
+}
+
+// These functions are generated by the compiler from the pointer layouts of
+// mutable globals. Each range contains only pointer slots.
+func gcGlobalRootCount() uintptr
+func gcGlobalRoot(index uintptr) unsafe.Pointer
+func gcGlobalRootSize(index uintptr) uintptr