runtime: source patch crypto internal constanttime

Author: cpunion

internal/build/source_patch_go126_test.go

@@ -58,3 +58,36 @@ func TestInternalSyncUsesSourcePatchInsteadOfAltPkg(t *testing.T) {
 		t.Fatal("internal/sync should not remain an alt package")
 	}
 }
+
+func TestBuildSourcePatchOverlayForCryptoInternalConstanttime(t *testing.T) {
+	overlay, err := buildSourcePatchOverlayForGOROOT(nil, env.LLGoRuntimeDir(), runtime.GOROOT(), sourcePatchBuildContext{
+		goos:      runtime.GOOS,
+		goarch:    runtime.GOARCH,
+		goversion: "go1.26.0",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	pkgDir := filepath.Join(runtime.GOROOT(), "src", "crypto", "internal", "constanttime")
+	patchFile := filepath.Join(pkgDir, "z_llgo_patch_constant_time.go")
+	patchSrc, ok := overlay[patchFile]
+	if !ok {
+		t.Fatalf("missing source patch file %s", patchFile)
+	}
+	if !strings.Contains(string(patchSrc), "//go:linkname boolToUint8 llgo.boolToUint8") {
+		t.Fatalf("source patch file %s does not contain boolToUint8 linkname", patchFile)
+	}
+	if !strings.HasPrefix(string(patchSrc), sourcePatchLineDirective(filepath.Join(env.LLGoRuntimeDir(), "_patch", "crypto", "internal", "constanttime", "constant_time.go"))) {
+		t.Fatalf("source patch file %s is missing line directive, got:\n%s", patchFile, patchSrc)
+	}
+}
+
+func TestCryptoInternalConstanttimeUsesSourcePatchInsteadOfAltPkg(t *testing.T) {
+	if !llruntime.HasSourcePatchPkg("crypto/internal/constanttime") {
+		t.Fatal("crypto/internal/constanttime should be registered as a source patch package")
+	}
+	if llruntime.HasAltPkg("crypto/internal/constanttime") {
+		t.Fatal("crypto/internal/constanttime should not remain an alt package")
+	}
+}

runtime/_patch/crypto/internal/constanttime/constant_time.go

@@ -0,0 +1,12 @@
+// 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 go1.26
+
+package constanttime
+
+import _ "unsafe"
+
+//go:linkname boolToUint8 llgo.boolToUint8
+func boolToUint8(b bool) uint8

runtime/build.go

@@ -40,19 +40,19 @@ func SourcePatchPkgPaths() []string {
 }
 
 var altPkgs = map[string]altPkgMode{
-	"crypto/internal/constanttime": altPkgReplace,
-	"internal/abi":                 altPkgReplace,
-	"internal/reflectlite":         altPkgReplace,
-	"internal/runtime/maps":        altPkgReplace,
-	"internal/runtime/sys":         altPkgAdditive,
-	"reflect":                      altPkgReplace,
-	"runtime":                      altPkgReplace,
-	"sync/atomic":                  altPkgReplace,
-	"syscall/js":                   altPkgReplace,
-	"unique":                       altPkgReplace,
+	"internal/abi":          altPkgReplace,
+	"internal/reflectlite":  altPkgReplace,
+	"internal/runtime/maps": altPkgReplace,
+	"internal/runtime/sys":  altPkgAdditive,
+	"reflect":               altPkgReplace,
+	"runtime":               altPkgReplace,
+	"sync/atomic":           altPkgReplace,
+	"syscall/js":            altPkgReplace,
+	"unique":                altPkgReplace,
 }
 
 var sourcePatchPkgs = map[string]struct{}{
-	"internal/sync": {},
-	"iter":          {},
+	"crypto/internal/constanttime": {},
+	"internal/sync":                {},
+	"iter":                         {},
 }