cmd/go: use -buildmode=pie as default on window

This change adjusts go command to pass -buildmode=pie to cmd/link,
if -buildmode is not explicitly provided.

Fixes #35192

Change-Id: Iec020131e676eb3e9a2df9eea1929b2af2b6df04
Reviewed-on: https://go-review.googlesource.com/c/go/+/230217
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

doc/go1.15.html

@@ -31,6 +31,12 @@ TODO
 
 <h2 id="ports">Ports</h2>
 
+<p> <!-- CL 214397 and CL 230217 -->
+  Go 1.15 now generates Windows ASLR executables when -buildmode=pie
+  cmd/link flag is provided. Go command uses -buildmode=pie by default
+  on Windows.
+</p>
+
 <p>
 TODO
 </p>

src/cmd/go/go_test.go

@@ -2082,19 +2082,38 @@ func TestBuildmodePIE(t *testing.T) {
 		t.Skipf("skipping test because buildmode=pie is not supported on %s", platform)
 	}
 	t.Run("non-cgo", func(t *testing.T) {
-		testBuildmodePIE(t, false)
+		testBuildmodePIE(t, false, true)
 	})
 	if canCgo {
 		switch runtime.GOOS {
 		case "darwin", "freebsd", "linux", "windows":
 			t.Run("cgo", func(t *testing.T) {
-				testBuildmodePIE(t, true)
+				testBuildmodePIE(t, true, true)
 			})
 		}
 	}
 }
 
-func testBuildmodePIE(t *testing.T, useCgo bool) {
+func TestWindowsDefaultBuildmodIsPIE(t *testing.T) {
+	if testing.Short() && testenv.Builder() == "" {
+		t.Skipf("skipping in -short mode on non-builder")
+	}
+
+	if runtime.GOOS != "windows" {
+		t.Skip("skipping windows only test")
+	}
+
+	t.Run("non-cgo", func(t *testing.T) {
+		testBuildmodePIE(t, false, false)
+	})
+	if canCgo {
+		t.Run("cgo", func(t *testing.T) {
+			testBuildmodePIE(t, true, false)
+		})
+	}
+}
+
+func testBuildmodePIE(t *testing.T, useCgo, setBuildmodeToPIE bool) {
 	tg := testgo(t)
 	defer tg.cleanup()
 	tg.parallel()
@@ -2106,7 +2125,12 @@ func testBuildmodePIE(t *testing.T, useCgo bool) {
 	tg.tempFile("main.go", fmt.Sprintf(`package main;%s func main() { print("hello") }`, s))
 	src := tg.path("main.go")
 	obj := tg.path("main.exe")
-	tg.run("build", "-buildmode=pie", "-o", obj, src)
+	args := []string{"build"}
+	if setBuildmodeToPIE {
+		args = append(args, "-buildmode=pie")
+	}
+	args = append(args, "-o", obj, src)
+	tg.run(args...)
 
 	switch runtime.GOOS {
 	case "linux", "android", "freebsd":

src/cmd/go/internal/work/init.go

@@ -155,6 +155,8 @@ func buildModeInit() {
 		case "android":
 			codegenArg = "-shared"
 			ldBuildmode = "pie"
+		case "windows":
+			ldBuildmode = "pie"
 		case "darwin":
 			switch cfg.Goarch {
 			case "arm64":

src/cmd/link/internal/ld/dwarf_test.go

@@ -924,8 +924,8 @@ func TestRuntimeTypeAttrInternal(t *testing.T) {
 		t.Skip("skipping on plan9; no DWARF symbol table in executables")
 	}
 
-	if runtime.GOOS == "windows" && runtime.GOARCH == "arm" {
+	if runtime.GOOS == "windows" {
-		t.Skip("skipping on windows/arm; test is incompatible with relocatable binaries")
+		t.Skip("skipping on windows; test is incompatible with relocatable binaries")
 	}
 
 	testRuntimeTypeAttr(t, "-ldflags=-linkmode=internal")
@@ -944,6 +944,11 @@ func TestRuntimeTypeAttrExternal(t *testing.T) {
 	if runtime.GOARCH == "ppc64" {
 		t.Skip("-linkmode=external not supported on ppc64")
 	}
+
+	if runtime.GOOS == "windows" {
+		t.Skip("skipping on windows; test is incompatible with relocatable binaries")
+	}
+
 	testRuntimeTypeAttr(t, "-ldflags=-linkmode=external")
 }
 

src/cmd/nm/nm_test.go

@@ -170,7 +170,7 @@ func testGoExec(t *testing.T, iscgo, isexternallinker bool) {
 				return true
 			}
 		}
-		if runtime.GOOS == "windows" && runtime.GOARCH == "arm" {
+		if runtime.GOOS == "windows" {
 			return true
 		}
 		return false