runtime: test VDSO symbol hash values

In addition to verifying existing values, this makes it easier to add a
new one by adding an invalid entry and running the test.

Change-Id: I6a6a636c9c413add29884e4f6759196f4db34de7
Reviewed-on: https://go-review.googlesource.com/c/go/+/693276
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

src/runtime/export_vdso_linux_test.go

@@ -0,0 +1,29 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build linux && (386 || amd64 || arm || arm64 || loong64 || mips64 || mips64le || ppc64 || ppc64le || riscv64 || s390x)
+
+package runtime
+
+type VDSOSymbolKey vdsoSymbolKey
+
+func (v VDSOSymbolKey) Name() string {
+	return v.name
+}
+
+func (v VDSOSymbolKey) SymHash() uint32 {
+	return v.symHash
+}
+
+func (v VDSOSymbolKey) GNUHash() uint32 {
+	return v.gnuHash
+}
+
+func VDSOSymbolKeys() []VDSOSymbolKey {
+	keys := make([]VDSOSymbolKey, 0, len(vdsoSymbolKeys))
+	for _, k := range vdsoSymbolKeys {
+		keys = append(keys, VDSOSymbolKey(k))
+	}
+	return keys
+}

src/runtime/vdso_linux_test.go

@@ -0,0 +1,52 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build linux && (386 || amd64 || arm || arm64 || loong64 || mips64 || mips64le || ppc64 || ppc64le || riscv64 || s390x)
+
+package runtime_test
+
+import (
+	"runtime"
+	"testing"
+)
+
+// DT_GNU_HASH hash function.
+func gnuHash(s string) uint32 {
+	h := uint32(5381)
+	for _, r := range s {
+		h = (h << 5) + h + uint32(r)
+	}
+	return h
+}
+
+// DT_HASH hash function.
+func symHash(s string) uint32 {
+	var h, g uint32
+	for _, r := range s {
+		h = (h << 4) + uint32(r)
+		g = h & 0xf0000000
+		if g != 0 {
+			h ^= g >> 24
+		}
+		h &^= g
+	}
+	return h
+}
+
+func TestVDSOHash(t *testing.T) {
+	for _, sym := range runtime.VDSOSymbolKeys() {
+		name := sym.Name()
+		t.Run(name, func(t *testing.T) {
+			want := symHash(name)
+			if sym.SymHash() != want {
+				t.Errorf("SymHash got %#x want %#x", sym.SymHash(), want)
+			}
+
+			want = gnuHash(name)
+			if sym.GNUHash() != want {
+				t.Errorf("GNUHash got %#x want %#x", sym.GNUHash(), want)
+			}
+		})
+	}
+}