[dev.link] all: merge branch 'master' into dev.link

It has been a while we have not done this.

Merge conflict resolution:
- deleted/rewritten code modified on master
  - CL 214286, ported in CL 217317
    (cmd/internal/obj/objfile.go)
  - CL 210678, it already includes a fix to new code
    (cmd/link/internal/ld/deadcode.go)
  - CL 209317, applied in this CL
    (cmd/link/internal/loadelf/ldelf.go)

Change-Id: Ie927ea6a1d69ce49e8d03e56148cb2725e377876

3 files changed, 22 insertions, 3 deletions

diff --git a/src/cmd/dist/build.go b/src/cmd/dist/build.go
index 9eb9e8f241..62e00b0856 100644
--- a/src/cmd/dist/build.go
+++ b/src/cmd/dist/build.go
@@ -110,6 +110,9 @@ func xinit() {
 		fatalf("$GOROOT must be set")
 	}
 	goroot = filepath.Clean(b)
+	if modRoot := findModuleRoot(goroot); modRoot != "" {
+		fatalf("found go.mod file in %s: $GOROOT must not be inside a module", modRoot)
+	}
 
 	b = os.Getenv("GOROOT_FINAL")
 	if b == "" {
@@ -1532,7 +1535,7 @@ var cgoEnabled = map[string]bool{
 	"linux/mipsle":    true,
 	"linux/mips64":    true,
 	"linux/mips64le":  true,
-	"linux/riscv64":   true,
+	"linux/riscv64":   false, // Issue 36641
 	"linux/s390x":     true,
 	"linux/sparc64":   true,
 	"android/386":     true,
@@ -1560,7 +1563,6 @@ var cgoEnabled = map[string]bool{
 // List of platforms which are supported but not complete yet. These get
 // filtered out of cgoEnabled for 'dist list'. See golang.org/issue/28944
 var incomplete = map[string]bool{
-	"linux/riscv64": true,
 	"linux/sparc64": true,
 }
 
@@ -1590,6 +1592,20 @@ func checkCC() {
 	}
 }
 
+func findModuleRoot(dir string) (root string) {
+	for {
+		if fi, err := os.Stat(filepath.Join(dir, "go.mod")); err == nil && !fi.IsDir() {
+			return dir
+		}
+		d := filepath.Dir(dir)
+		if d == dir {
+			break
+		}
+		dir = d
+	}
+	return ""
+}
+
 func defaulttarg() string {
 	// xgetwd might return a path with symlinks fully resolved, and if
 	// there happens to be symlinks in goroot, then the hasprefix test
diff --git a/src/cmd/dist/buildtool.go b/src/cmd/dist/buildtool.go
index 12baccbc4f..118800e8da 100644
--- a/src/cmd/dist/buildtool.go
+++ b/src/cmd/dist/buildtool.go
@@ -45,10 +45,11 @@ var bootstrapDirs = []string{
 	"cmd/compile/internal/mips",
 	"cmd/compile/internal/mips64",
 	"cmd/compile/internal/ppc64",
-	"cmd/compile/internal/types",
+	"cmd/compile/internal/riscv64",
 	"cmd/compile/internal/s390x",
 	"cmd/compile/internal/ssa",
 	"cmd/compile/internal/syntax",
+	"cmd/compile/internal/types",
 	"cmd/compile/internal/x86",
 	"cmd/compile/internal/wasm",
 	"cmd/internal/bio",
diff --git a/src/cmd/dist/main.go b/src/cmd/dist/main.go
index 3e54915122..b8a8c5f2e6 100644
--- a/src/cmd/dist/main.go
+++ b/src/cmd/dist/main.go
@@ -122,6 +122,8 @@ func main() {
 			if elfIsLittleEndian(os.Args[0]) {
 				gohostarch = "mipsle"
 			}
+		case strings.Contains(out, "riscv64"):
+			gohostarch = "riscv64"
 		case strings.Contains(out, "s390x"):
 			gohostarch = "s390x"
 		case gohostos == "darwin":