From: Ian Lance Taylor <ian@gcc.gnu.org>
Date: Thu, 25 Oct 2018 22:18:08 +0000 (+0000)
Subject: compiler: improve name mangling for packpaths
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=34489eb2af3bbb7be101bc838615cf4a4dc6828d;p=gcc.git

compiler: improve name mangling for packpaths

    The current implementation of Gogo::pkgpath_for_symbol was written in
    a way that allowed two distinct package paths to map to the same
    symbol, which could cause collisions at link- time or compile-time.

    Switch to a better mangling scheme to insure that we get a unique
    packagepath symbol for each package. In the new scheme instead of having
    separate mangling schemes for identifiers and package paths, the
    main identifier mangler ("go_encode_id") now handles mangling of
    both packagepath characters and identifier characters.

    The new mangling scheme is more intrusive: "foo/bar.Baz" is mangled as
    "foo..z2fbar.Baz" instead of "foo_bar.Baz". To mitigate this, this
    patch also adds a demangling capability so that function names
    returned from runtime.CallersFrames are converted back to their
    original unmangled form.

    Changing the pkgpath_for_symbol scheme requires updating a number of
    //go:linkname directives and C "__asm__" directives to match the new
    scheme, as well as updating the 'gotest' driver (which makes
    assumptions about the correct mapping from pkgpath symbol to package
    name).

    Fixes golang/go#27534.

    Reviewed-on: https://go-review.googlesource.com/c/135455

From-SVN: r265510
---

diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index a42d0b9961c..188ada01a3c 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-771668f7137e560b2ef32c8799e5f8b4c4ee14a9
+407a59831ea4fbfe03f0887c40497b73939e7c44
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
diff --git a/gcc/go/gofrontend/go-encode-id.cc b/gcc/go/gofrontend/go-encode-id.cc
index e130ba1a08e..7c7aa13ea1c 100644
--- a/gcc/go/gofrontend/go-encode-id.cc
+++ b/gcc/go/gofrontend/go-encode-id.cc
@@ -1,4 +1,4 @@
-// go-encode-id.cc -- Go identifier encoding hooks
+// go-encode-id.cc -- Go identifier and packagepath encoding/decoding hooks
 
 // Copyright 2016 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -82,10 +82,10 @@ fetch_utf8_char(const char* p, unsigned int* pc)
   return len;
 }
 
-// Encode an identifier using ASCII characters.  The encoding is
-// described in detail near the end of the long comment at the start
-// of names.cc.  Short version: translate all non-ASCII-alphanumeric
-// characters into ..uXXXX or ..UXXXXXXXX.
+// Encode an identifier using assembler-friendly characters. The encoding is
+// described in detail near the end of the long comment at the start of
+// names.cc. Short version: translate all non-ASCII-alphanumeric characters into
+// ..uXXXX or ..UXXXXXXXX, translate ASCII non-alphanumerics into ".zXX".
 
 std::string
 go_encode_id(const std::string &id)
@@ -97,7 +97,8 @@ go_encode_id(const std::string &id)
     }
 
   // The encoding is only unambiguous if the input string does not
-  // contain ..u or ..U.
+  // contain ..z, ..u or ..U.
+  go_assert(id.find("..z") == std::string::npos);
   go_assert(id.find("..u") == std::string::npos);
   go_assert(id.find("..U") == std::string::npos);
 
@@ -116,17 +117,16 @@ go_encode_id(const std::string &id)
     {
       unsigned int c;
       size_t len = fetch_utf8_char(p, &c);
-      if (len == 1)
+      if (len == 1 && !char_needs_encoding(c))
 	{
-	  // At this point we should only be seeing alphanumerics or
-	  // underscore or dot.
-	  go_assert(!char_needs_encoding(c));
 	  ret += c;
 	}
       else
 	{
 	  char buf[16];
-	  if (c < 0x10000)
+          if (len == 1)
+            snprintf(buf, sizeof buf, "..z%02x", c);
+	  else if (c < 0x10000)
 	    snprintf(buf, sizeof buf, "..u%04x", c);
 	  else
 	    snprintf(buf, sizeof buf, "..U%08x", c);
@@ -143,6 +143,77 @@ go_encode_id(const std::string &id)
   return ret;
 }
 
+// Convert a hex digit string to a unicode codepoint. No checking
+// to insure that the hex digit is meaningful.
+
+static unsigned
+hex_digits_to_unicode_codepoint(const char *digits, unsigned ndig)
+{
+  unsigned result = 0;
+  for (unsigned i = 0; i < ndig; ++i) {
+    result <<= 4;
+    result |= Lex::hex_val(digits[i]);
+  }
+  return result;
+}
+
+// Decode/demangle a mangled string produced by go_encode_id(). Returns
+// empty string if demangling process fails in some way.  At the moment
+// this routine is unused; there is an equivalent routine in the runtime
+// used for demangling symbols appearing in stack traces.
+
+std::string
+go_decode_id(const std::string &encoded)
+{
+  std::string ret;
+  const char* p = encoded.c_str();
+  const char* pend = p + encoded.length();
+  const Location loc = Linemap::predeclared_location();
+
+  // Special case for initial "_", in case it was introduced
+  // as a way to prevent encoded symbol starting with ".".
+  if (*p == '_' && (strncmp(p+1, "..u", 3) == 0 || strncmp(p+1, "..U", 3) == 0))
+    p++;
+
+  while (p < pend)
+    {
+      if (strncmp(p, "..z", 3) == 0)
+        {
+          const char* digits = p+3;
+          if (strlen(digits) < 2)
+            return "";
+          unsigned rune = hex_digits_to_unicode_codepoint(digits, 2);
+          Lex::append_char(rune, true, &ret, loc);
+          p += 5;
+        }
+      else if (strncmp(p, "..u", 3) == 0)
+        {
+          const char* digits = p+3;
+          if (strlen(digits) < 4)
+            return "";
+          unsigned rune = hex_digits_to_unicode_codepoint(digits, 4);
+          Lex::append_char(rune, true, &ret, loc);
+          p += 7;
+        }
+      else if (strncmp(p, "..U", 3) == 0)
+        {
+          const char* digits = p+3;
+          if (strlen(digits) < 8)
+            return "";
+          unsigned rune = hex_digits_to_unicode_codepoint(digits, 8);
+          Lex::append_char(rune, true, &ret, loc);
+          p += 11;
+        }
+      else
+        {
+          ret += *p;
+          p += 1;
+        }
+    }
+
+  return ret;
+}
+
 std::string
 go_selectively_encode_id(const std::string &id)
 {
diff --git a/gcc/go/gofrontend/go-encode-id.h b/gcc/go/gofrontend/go-encode-id.h
index ec81b63a182..70126bae9d1 100644
--- a/gcc/go/gofrontend/go-encode-id.h
+++ b/gcc/go/gofrontend/go-encode-id.h
@@ -20,6 +20,11 @@ go_id_needs_encoding(const std::string& str);
 extern std::string
 go_encode_id(const std::string &id);
 
+// Decodes an encoded ID, returning the original string handed off to
+// go_encode_id().
+extern std::string
+go_decode_id(const std::string &id);
+
 // Returns the empty string if the specified name needs encoding,
 // otherwise invokes go_encode_id on the name and returns the result.
 extern std::string
diff --git a/gcc/go/gofrontend/gogo.cc b/gcc/go/gofrontend/gogo.cc
index 2472245ebe9..70af6273b01 100644
--- a/gcc/go/gofrontend/gogo.cc
+++ b/gcc/go/gofrontend/gogo.cc
@@ -256,26 +256,11 @@ Gogo::Gogo(Backend* backend, Linemap* linemap, int, int pointer_size)
   this->globals_->add_function_declaration("delete", NULL, delete_type, loc);
 }
 
-// Convert a pkgpath into a string suitable for a symbol.  Note that
-// this transformation is convenient but imperfect.  A -fgo-pkgpath
-// option of a/b_c will conflict with a -fgo-pkgpath option of a_b/c,
-// possibly leading to link time errors.
-
 std::string
 Gogo::pkgpath_for_symbol(const std::string& pkgpath)
 {
-  std::string s = pkgpath;
-  for (size_t i = 0; i < s.length(); ++i)
-    {
-      char c = s[i];
-      if ((c >= 'a' && c <= 'z')
-	  || (c >= 'A' && c <= 'Z')
-	  || (c >= '0' && c <= '9'))
-	;
-      else
-	s[i] = '_';
-    }
-  return s;
+  go_assert(!pkgpath.empty());
+  return go_encode_id(pkgpath);
 }
 
 // Get the package path to use for type reflection data.  This should
@@ -319,6 +304,32 @@ Gogo::set_prefix(const std::string& arg)
   this->prefix_from_option_ = true;
 }
 
+// Given a name which may or may not have been hidden, append the
+// appropriate version of the name to the result string. Take care
+// to avoid creating a sequence that will be rejected by go_encode_id
+// (avoid ..u, ..U, ..z).
+void
+Gogo::append_possibly_hidden_name(std::string *result, const std::string& name)
+{
+  // FIXME: This adds in pkgpath twice for hidden symbols, which is
+  // less than ideal.
+  if (!Gogo::is_hidden_name(name))
+    (*result) += name;
+  else
+    {
+      std::string n = ".";
+      std::string pkgpath = Gogo::hidden_name_pkgpath(name);
+      char lastR = result->at(result->length() - 1);
+      char firstP = pkgpath.at(0);
+      if (lastR == '.' && (firstP == 'u' || firstP == 'U' || firstP == 'z'))
+        n = "_.";
+      n.append(pkgpath);
+      n.append(1, '.');
+      n.append(Gogo::unpack_hidden_name(name));
+      (*result) += n;
+    }
+}
+
 // Munge name for use in an error message.
 
 std::string
diff --git a/gcc/go/gofrontend/gogo.h b/gcc/go/gofrontend/gogo.h
index 9c469ca32b5..48359ebe560 100644
--- a/gcc/go/gofrontend/gogo.h
+++ b/gcc/go/gofrontend/gogo.h
@@ -199,26 +199,10 @@ class Gogo
     return name.substr(1, name.rfind('.') - 1);
   }
 
-  // Given a name which may or may not have been hidden, return the
-  // name to use within a mangled symbol name.
-  static std::string
-  mangle_possibly_hidden_name(const std::string& name)
-  { 
-    // FIXME: This adds in pkgpath twice for hidden symbols, which is
-    // less than ideal.
-    std::string n;
-    if (!Gogo::is_hidden_name(name))
-      n = name;
-    else
-      {
-        n = ".";
-        std::string pkgpath = Gogo::hidden_name_pkgpath(name);
-        n.append(Gogo::pkgpath_for_symbol(pkgpath));
-        n.append(1, '.');
-        n.append(Gogo::unpack_hidden_name(name));
-      }
-    return n;
-  }
+  // Given a name which may or may not have been hidden, append the
+  // appropriate version of the name to the result string.
+  static void
+  append_possibly_hidden_name(std::string *result, const std::string& name);
 
   // Given a name which may or may not have been hidden, return the
   // name to use in an error message.
diff --git a/gcc/go/gofrontend/lex.h b/gcc/go/gofrontend/lex.h
index cf3de8d5575..75e37f84bdc 100644
--- a/gcc/go/gofrontend/lex.h
+++ b/gcc/go/gofrontend/lex.h
@@ -440,6 +440,10 @@ class Lex
   static bool
   is_unicode_space(unsigned int c);
 
+  // Convert the specified hex char into an unsigned integer value.
+  static unsigned
+  hex_val(char c);
+
  private:
   ssize_t
   get_line();
@@ -462,9 +466,6 @@ class Lex
   octal_value(char c)
   { return c - '0'; }
 
-  static unsigned
-  hex_val(char c);
-
   Token
   make_invalid_token()
   { return Token::make_invalid_token(this->location()); }
diff --git a/gcc/go/gofrontend/names.cc b/gcc/go/gofrontend/names.cc
index 2e36a1d3262..d9ae59105df 100644
--- a/gcc/go/gofrontend/names.cc
+++ b/gcc/go/gofrontend/names.cc
@@ -33,7 +33,7 @@
 // variable, is simply "PKGPATH.NAME".  Note that NAME is not the
 // packed form used for the "hidden" name internally in the compiler;
 // it is the name that appears in the source code.  PKGPATH is the
-// -fgo-pkgpath option as adjusted by Gogo::pkgpath_for_symbol.  Note
+// -fgo-pkgpath option as adjusted by Gogo::pkgpath_for_symbol. Note
 // that PKGPATH can not contain a dot and neither can NAME.  Also,
 // NAME may not begin with a digit.  NAME may require further encoding
 // for non-ASCII characters as described below, but until that
@@ -188,12 +188,17 @@
 // encoding unambiguous, we introduce it with two consecutive dots.
 // This is followed by the letter u and four hex digits or the letter
 // U and eight digits, just as in the language only using ..u and ..U
-// instead of \u and \U.  Since before this encoding names can never
-// contain consecutive dots followed by 'u' or 'U', and after this
-// encoding "..u" and "..U" are followed by a known number of
+// instead of \u and \U.  The compiler also produces identifiers that
+// are qualified by package path, which means that there may also be ASCII
+// characters that are not assembler-friendly (ex: '=', '/'). The encoding
+// scheme translates such characters into the "..zNN" where NN is the
+// hex value for the character. Since before this encoding names can never
+// contain consecutive dots followed by 'z', 'u' or 'U', and after this
+// encoding "..z", "..u" and "..U" are followed by a known number of
 // characters, this is unambiguous.
 //
 // Demangling these names is straightforward:
+//  - replace ..zXX with an ASCII character
 //  - replace ..uXXXX with a unicode character
 //  - replace ..UXXXXXXXX with a unicode character
 //  - replace .D, where D is a digit, with the character from the above
@@ -215,9 +220,9 @@ Gogo::function_asm_name(const std::string& go_name, const Package* package,
   if (rtype != NULL)
     ret = rtype->deref()->mangled_name(this);
   else if (package == NULL)
-    ret = this->pkgpath_symbol();
+    ret = this->pkgpath();
   else
-    ret = package->pkgpath_symbol();
+    ret = package->pkgpath();
   ret.push_back('.');
   // Check for special names that will break if we use
   // Gogo::unpack_hidden_name.
@@ -268,7 +273,7 @@ Gogo::stub_method_name(const Package* package, const std::string& mname)
 
   // We are creating a stub method for an unexported method of an
   // imported embedded type.  We need to disambiguate the method name.
-  std::string ret = this->pkgpath_symbol_for_package(mpkgpath);
+  std::string ret = mpkgpath;
   ret.push_back('.');
   ret.append(Gogo::unpack_hidden_name(mname));
   ret.append("..stub");
@@ -302,9 +307,9 @@ Gogo::global_var_asm_name(const std::string& go_name, const Package* package)
 {
   std::string ret;
   if (package == NULL)
-    ret = this->pkgpath_symbol();
+    ret = this->pkgpath();
   else
-    ret = package->pkgpath_symbol();
+    ret = package->pkgpath();
   ret.append(1, '.');
   ret.append(Gogo::unpack_hidden_name(go_name));
   return go_encode_id(ret);
@@ -341,7 +346,7 @@ Gogo::thunk_name()
   char thunk_name[50];
   snprintf(thunk_name, sizeof thunk_name, "..thunk%d", thunk_count);
   ++thunk_count;
-  std::string ret = this->pkgpath_symbol();
+  std::string ret = this->pkgpath();
   return ret + thunk_name;
 }
 
@@ -370,7 +375,7 @@ Gogo::init_function_name()
   char buf[30];
   snprintf(buf, sizeof buf, "..init%d", init_count);
   ++init_count;
-  std::string ret = this->pkgpath_symbol();
+  std::string ret = this->pkgpath();
   return ret + buf;
 }
 
@@ -726,7 +731,7 @@ Struct_type::do_mangled_name(Gogo* gogo, std::string* ret) const
 
 	  if (!p->is_anonymous())
 	    {
-	      ret->append(Gogo::mangle_possibly_hidden_name(p->field_name()));
+              Gogo::append_possibly_hidden_name(ret, p->field_name());
 	      ret->push_back(' ');
 	    }
 
@@ -827,7 +832,7 @@ Interface_type::do_mangled_name(Gogo* gogo, std::string* ret) const
 
 	  if (!p->name().empty())
 	    {
-	      ret->append(Gogo::mangle_possibly_hidden_name(p->name()));
+              Gogo::append_possibly_hidden_name(ret, p->name());
 	      ret->push_back(' ');
 	    }
 
@@ -854,9 +859,9 @@ Forward_declaration_type::do_mangled_name(Gogo* gogo, std::string* ret) const
     {
       const Named_object* no = this->named_object();
       if (no->package() == NULL)
-	ret->append(gogo->pkgpath_symbol());
+	ret->append(gogo->pkgpath());
       else
-	ret->append(no->package()->pkgpath_symbol());
+	ret->append(no->package()->pkgpath());
       ret->push_back('.');
       ret->append(Gogo::unpack_hidden_name(no->name()));
     }
@@ -894,18 +899,18 @@ Named_type::append_mangled_type_name(Gogo* gogo, bool use_alias,
 	  if (rcvr != NULL)
 	    ret->append(rcvr->type()->deref()->mangled_name(gogo));
 	  else if (this->in_function_->package() == NULL)
-	    ret->append(gogo->pkgpath_symbol());
+	    ret->append(gogo->pkgpath());
 	  else
-	    ret->append(this->in_function_->package()->pkgpath_symbol());
+	    ret->append(this->in_function_->package()->pkgpath());
 	  ret->push_back('.');
 	  ret->append(Gogo::unpack_hidden_name(this->in_function_->name()));
 	}
       else
 	{
 	  if (no->package() == NULL)
-	    ret->append(gogo->pkgpath_symbol());
+	    ret->append(gogo->pkgpath());
 	  else
-	    ret->append(no->package()->pkgpath_symbol());
+	    ret->append(no->package()->pkgpath());
 	}
       ret->push_back('.');
     }
@@ -951,22 +956,22 @@ Gogo::type_descriptor_name(Type* type, Named_type* nt)
 	  if (rcvr != NULL)
 	    ret.append(rcvr->type()->deref()->mangled_name(this));
 	  else if (in_function->package() == NULL)
-	    ret.append(this->pkgpath_symbol());
+	    ret.append(this->pkgpath());
 	  else
-	    ret.append(in_function->package()->pkgpath_symbol());
+	    ret.append(in_function->package()->pkgpath());
 	  ret.push_back('.');
 	  ret.append(Gogo::unpack_hidden_name(in_function->name()));
 	  ret.push_back('.');
 	}
 
       if (no->package() == NULL)
-	ret.append(this->pkgpath_symbol());
+	ret.append(this->pkgpath());
       else
-	ret.append(no->package()->pkgpath_symbol());
+	ret.append(no->package()->pkgpath());
       ret.push_back('.');
     }
 
-  ret.append(Gogo::mangle_possibly_hidden_name(no->name()));
+  Gogo::append_possibly_hidden_name(&ret, no->name());
 
   if (in_function != NULL && index > 0)
     {
diff --git a/libgo/go/cmd/cgo/main.go b/libgo/go/cmd/cgo/main.go
index 1238016418e..8e7567b5b0e 100644
--- a/libgo/go/cmd/cgo/main.go
+++ b/libgo/go/cmd/cgo/main.go
@@ -229,6 +229,8 @@ var exportHeader = flag.String("exportheader", "", "where to write export header
 var gccgo = flag.Bool("gccgo", false, "generate files for use with gccgo")
 var gccgoprefix = flag.String("gccgoprefix", "", "-fgo-prefix option used with gccgo")
 var gccgopkgpath = flag.String("gccgopkgpath", "", "-fgo-pkgpath option used with gccgo")
+var gccgoMangleCheckDone bool
+var gccgoNewmanglingInEffect bool
 var importRuntimeCgo = flag.Bool("import_runtime_cgo", true, "import runtime/cgo in generated code")
 var importSyscall = flag.Bool("import_syscall", true, "import syscall in generated code")
 var goarch, goos string
diff --git a/libgo/go/cmd/cgo/out.go b/libgo/go/cmd/cgo/out.go
index 10d4b74b6ee..60b2c116ba5 100644
--- a/libgo/go/cmd/cgo/out.go
+++ b/libgo/go/cmd/cgo/out.go
@@ -15,7 +15,9 @@ import (
 	"go/printer"
 	"go/token"
 	"io"
+	"io/ioutil"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"regexp"
 	"sort"
@@ -1191,12 +1193,91 @@ func (p *Package) writeExportHeader(fgcch io.Writer) {
 	fmt.Fprintf(fgcch, "%s\n", p.gccExportHeaderProlog())
 }
 
-// Return the package prefix when using gccgo.
-func (p *Package) gccgoSymbolPrefix() string {
-	if !*gccgo {
-		return ""
+// gccgoUsesNewMangling returns whether gccgo uses the new collision-free
+// packagepath mangling scheme (see determineGccgoManglingScheme for more
+// info).
+func gccgoUsesNewMangling() bool {
+	if !gccgoMangleCheckDone {
+		gccgoNewmanglingInEffect = determineGccgoManglingScheme()
+		gccgoMangleCheckDone = true
+	}
+	return gccgoNewmanglingInEffect
+}
+
+const mangleCheckCode = `
+package läufer
+func Run(x int) int {
+  return 1
+}
+`
+
+// determineGccgoManglingScheme performs a runtime test to see which
+// flavor of packagepath mangling gccgo is using. Older versions of
+// gccgo use a simple mangling scheme where there can be collisions
+// between packages whose paths are different but mangle to the same
+// string. More recent versions of gccgo use a new mangler that avoids
+// these collisions. Return value is whether gccgo uses the new mangling.
+func determineGccgoManglingScheme() bool {
+
+	// Emit a small Go file for gccgo to compile.
+	filepat := "*_gccgo_manglecheck.go"
+	var f *os.File
+	var err error
+	if f, err = ioutil.TempFile(*objDir, filepat); err != nil {
+		fatalf("%v", err)
+	}
+	gofilename := f.Name()
+	defer os.Remove(gofilename)
+
+	if err = ioutil.WriteFile(gofilename, []byte(mangleCheckCode), 0666); err != nil {
+		fatalf("%v", err)
+	}
+
+	// Compile with gccgo, capturing generated assembly.
+	gccgocmd := os.Getenv("GCCGO")
+	if gccgocmd == "" {
+		gpath, gerr := exec.LookPath("gccgo")
+		if gerr != nil {
+			fatalf("unable to locate gccgo: %v", gerr)
+		}
+		gccgocmd = gpath
+	}
+	cmd := exec.Command(gccgocmd, "-S", "-o", "-", gofilename)
+	buf, cerr := cmd.CombinedOutput()
+	if cerr != nil {
+		fatalf("%s", err)
+	}
+
+	// New mangling: expect go.l..u00e4ufer.Run
+	// Old mangling: expect go.l__ufer.Run
+	return regexp.MustCompile(`go\.l\.\.u00e4ufer\.Run`).Match(buf)
+}
+
+// gccgoPkgpathToSymbolNew converts a package path to a gccgo-style
+// package symbol.
+func gccgoPkgpathToSymbolNew(ppath string) string {
+	bsl := []byte{}
+	changed := false
+	for _, c := range []byte(ppath) {
+		switch {
+		case 'A' <= c && c <= 'Z', 'a' <= c && c <= 'z',
+			'0' <= c && c <= '9', '_' == c:
+			bsl = append(bsl, c)
+		default:
+			changed = true
+			encbytes := []byte(fmt.Sprintf("..z%02x", c))
+			bsl = append(bsl, encbytes...)
+		}
+	}
+	if !changed {
+		return ppath
 	}
+	return string(bsl)
+}
 
+// gccgoPkgpathToSymbolOld converts a package path to a gccgo-style
+// package symbol using the older mangling scheme.
+func gccgoPkgpathToSymbolOld(ppath string) string {
 	clean := func(r rune) rune {
 		switch {
 		case 'A' <= r && r <= 'Z', 'a' <= r && r <= 'z',
@@ -1205,14 +1286,32 @@ func (p *Package) gccgoSymbolPrefix() string {
 		}
 		return '_'
 	}
+	return strings.Map(clean, ppath)
+}
+
+// gccgoPkgpathToSymbol converts a package path to a mangled packagepath
+// symbol.
+func gccgoPkgpathToSymbol(ppath string) string {
+	if gccgoUsesNewMangling() {
+		return gccgoPkgpathToSymbolNew(ppath)
+	} else {
+		return gccgoPkgpathToSymbolOld(ppath)
+	}
+}
+
+// Return the package prefix when using gccgo.
+func (p *Package) gccgoSymbolPrefix() string {
+	if !*gccgo {
+		return ""
+	}
 
 	if *gccgopkgpath != "" {
-		return strings.Map(clean, *gccgopkgpath)
+		return gccgoPkgpathToSymbol(*gccgopkgpath)
 	}
 	if *gccgoprefix == "" && p.PackageName == "main" {
 		return "main"
 	}
-	prefix := strings.Map(clean, *gccgoprefix)
+	prefix := gccgoPkgpathToSymbol(*gccgoprefix)
 	if prefix == "" {
 		prefix = "go"
 	}
diff --git a/libgo/go/internal/bytealg/bytealg.c b/libgo/go/internal/bytealg/bytealg.c
index 988dfaacf0c..1ee1ff61a06 100644
--- a/libgo/go/internal/bytealg/bytealg.c
+++ b/libgo/go/internal/bytealg/bytealg.c
@@ -38,7 +38,7 @@ static const void *goMemmem(const void *in, size_t inl, const void *s, size_t sl
 #endif
 
 intgo Compare(struct __go_open_array, struct __go_open_array)
-  __asm__(GOSYM_PREFIX "internal_bytealg.Compare")
+  __asm__(GOSYM_PREFIX "internal..z2fbytealg.Compare")
   __attribute__((no_split_stack));
 
 intgo Compare(struct __go_open_array a, struct __go_open_array b)
@@ -67,7 +67,7 @@ intgo Compare(struct __go_open_array a, struct __go_open_array b)
 }
 
 _Bool Equal(struct __go_open_array, struct __go_open_array)
-  __asm__(GOSYM_PREFIX "internal_bytealg.Equal")
+  __asm__(GOSYM_PREFIX "internal..z2fbytealg.Equal")
   __attribute__((no_split_stack));
 
 _Bool Equal(struct __go_open_array a, struct __go_open_array b)
@@ -82,7 +82,7 @@ _Bool Equal(struct __go_open_array a, struct __go_open_array b)
 }
 
 intgo IndexByte(struct __go_open_array, byte)
-  __asm__(GOSYM_PREFIX "internal_bytealg.IndexByte")
+  __asm__(GOSYM_PREFIX "internal..z2fbytealg.IndexByte")
   __attribute__((no_split_stack));
 
 intgo IndexByte(struct __go_open_array b, byte c)
@@ -98,7 +98,7 @@ intgo IndexByte(struct __go_open_array b, byte c)
 
 
 intgo IndexByteString(String, byte)
-  __asm__(GOSYM_PREFIX "internal_bytealg.IndexByteString")
+  __asm__(GOSYM_PREFIX "internal..z2fbytealg.IndexByteString")
   __attribute__((no_split_stack));
 
 intgo IndexByteString(String s, byte c)
@@ -113,7 +113,7 @@ intgo IndexByteString(String s, byte c)
 }
 
 intgo Index(struct __go_open_array, struct __go_open_array)
-  __asm__(GOSYM_PREFIX "internal_bytealg.Index")
+  __asm__(GOSYM_PREFIX "internal..z2fbytealg.Index")
   __attribute__((no_split_stack));
 
 intgo Index(struct __go_open_array a, struct __go_open_array b)
@@ -128,7 +128,7 @@ intgo Index(struct __go_open_array a, struct __go_open_array b)
 }
 
 intgo IndexString(String, String)
-  __asm__(GOSYM_PREFIX "internal_bytealg.IndexString")
+  __asm__(GOSYM_PREFIX "internal..z2fbytealg.IndexString")
   __attribute__((no_split_stack));
 
 intgo IndexString(String a, String b)
diff --git a/libgo/go/internal/cpu/cpu_gccgo.c b/libgo/go/internal/cpu/cpu_gccgo.c
index 1d5b492a787..f9ebd8be45d 100644
--- a/libgo/go/internal/cpu/cpu_gccgo.c
+++ b/libgo/go/internal/cpu/cpu_gccgo.c
@@ -21,7 +21,7 @@ struct cpuid_ret {
 };
 
 struct cpuid_ret cpuid(uint32_t, uint32_t)
-  __asm__(GOSYM_PREFIX "internal_cpu.cpuid")
+  __asm__(GOSYM_PREFIX "internal..z2fcpu.cpuid")
   __attribute__((no_split_stack));
 
 struct cpuid_ret cpuid(uint32_t eaxArg, uint32_t ecxArg) {
@@ -45,7 +45,7 @@ struct xgetbv_ret {
 };
 
 struct xgetbv_ret xgetbv(void)
-  __asm__(GOSYM_PREFIX "internal_cpu.xgetbv")
+  __asm__(GOSYM_PREFIX "internal..z2fcpu.xgetbv")
   __attribute__((no_split_stack));
 
 #pragma GCC push_options
diff --git a/libgo/go/runtime/atomic_pointer.go b/libgo/go/runtime/atomic_pointer.go
index 2d023d3935c..03d8d6a48d5 100644
--- a/libgo/go/runtime/atomic_pointer.go
+++ b/libgo/go/runtime/atomic_pointer.go
@@ -52,10 +52,10 @@ func casp(ptr *unsafe.Pointer, old, new unsafe.Pointer) bool {
 // We cannot just call the runtime routines, because the race detector expects
 // to be able to intercept the sync/atomic forms but not the runtime forms.
 
-//go:linkname sync_atomic_StoreUintptr sync_atomic.StoreUintptr
+//go:linkname sync_atomic_StoreUintptr sync..z2fatomic.StoreUintptr
 func sync_atomic_StoreUintptr(ptr *uintptr, new uintptr)
 
-//go:linkname sync_atomic_StorePointer sync_atomic.StorePointer
+//go:linkname sync_atomic_StorePointer sync..z2fatomic.StorePointer
 //go:nosplit
 func sync_atomic_StorePointer(ptr *unsafe.Pointer, new unsafe.Pointer) {
 	if writeBarrier.enabled {
@@ -64,10 +64,10 @@ func sync_atomic_StorePointer(ptr *unsafe.Pointer, new unsafe.Pointer) {
 	sync_atomic_StoreUintptr((*uintptr)(unsafe.Pointer(ptr)), uintptr(new))
 }
 
-//go:linkname sync_atomic_SwapUintptr sync_atomic.SwapUintptr
+//go:linkname sync_atomic_SwapUintptr sync..z2fatomic.SwapUintptr
 func sync_atomic_SwapUintptr(ptr *uintptr, new uintptr) uintptr
 
-//go:linkname sync_atomic_SwapPointer sync_atomic.SwapPointer
+//go:linkname sync_atomic_SwapPointer sync..z2fatomic.SwapPointer
 //go:nosplit
 func sync_atomic_SwapPointer(ptr *unsafe.Pointer, new unsafe.Pointer) unsafe.Pointer {
 	if writeBarrier.enabled {
@@ -77,10 +77,10 @@ func sync_atomic_SwapPointer(ptr *unsafe.Pointer, new unsafe.Pointer) unsafe.Poi
 	return old
 }
 
-//go:linkname sync_atomic_CompareAndSwapUintptr sync_atomic.CompareAndSwapUintptr
+//go:linkname sync_atomic_CompareAndSwapUintptr sync..z2fatomic.CompareAndSwapUintptr
 func sync_atomic_CompareAndSwapUintptr(ptr *uintptr, old, new uintptr) bool
 
-//go:linkname sync_atomic_CompareAndSwapPointer sync_atomic.CompareAndSwapPointer
+//go:linkname sync_atomic_CompareAndSwapPointer sync..z2fatomic.CompareAndSwapPointer
 //go:nosplit
 func sync_atomic_CompareAndSwapPointer(ptr *unsafe.Pointer, old, new unsafe.Pointer) bool {
 	if writeBarrier.enabled {
diff --git a/libgo/go/runtime/cpuprof.go b/libgo/go/runtime/cpuprof.go
index b1a7c3bcd1b..e7cf1b4102d 100644
--- a/libgo/go/runtime/cpuprof.go
+++ b/libgo/go/runtime/cpuprof.go
@@ -186,7 +186,7 @@ func CPUProfile() []byte {
 	panic("CPUProfile no longer available")
 }
 
-//go:linkname runtime_pprof_runtime_cyclesPerSecond runtime_pprof.runtime_cyclesPerSecond
+//go:linkname runtime_pprof_runtime_cyclesPerSecond runtime..z2fpprof.runtime_cyclesPerSecond
 func runtime_pprof_runtime_cyclesPerSecond() int64 {
 	return tickspersecond()
 }
@@ -197,7 +197,7 @@ func runtime_pprof_runtime_cyclesPerSecond() int64 {
 // on has been returned, readProfile returns eof=true.
 // The caller must save the returned data and tags before calling readProfile again.
 //
-//go:linkname runtime_pprof_readProfile runtime_pprof.readProfile
+//go:linkname runtime_pprof_readProfile runtime..z2fpprof.readProfile
 func runtime_pprof_readProfile() ([]uint64, []unsafe.Pointer, bool) {
 	lock(&cpuprof.lock)
 	log := cpuprof.log
diff --git a/libgo/go/runtime/debug/stack_test.go b/libgo/go/runtime/debug/stack_test.go
index 67931d17f6b..309eddd818d 100644
--- a/libgo/go/runtime/debug/stack_test.go
+++ b/libgo/go/runtime/debug/stack_test.go
@@ -51,10 +51,10 @@ func TestStack(t *testing.T) {
 		n++
 	}
 	n++
-	frame("stack.go", "runtime_debug.Stack")
+	frame("stack.go", "debug.Stack")
 	frame("stack_test.go", "ptrmethod")
 	frame("stack_test.go", "method")
-	frame("stack_test.go", "runtime_debug_test.TestStack")
+	frame("stack_test.go", "test.TestStack")
 	frame("testing.go", "")
 }
 
diff --git a/libgo/go/runtime/heapdump.go b/libgo/go/runtime/heapdump.go
index e92ea39be21..5ebebf69474 100644
--- a/libgo/go/runtime/heapdump.go
+++ b/libgo/go/runtime/heapdump.go
@@ -16,7 +16,7 @@ import (
 	"unsafe"
 )
 
-//go:linkname runtime_debug_WriteHeapDump runtime_debug.WriteHeapDump
+//go:linkname runtime_debug_WriteHeapDump runtime..z2fdebug.WriteHeapDump
 func runtime_debug_WriteHeapDump(fd uintptr) {
 	stopTheWorld("write heap dump")
 
diff --git a/libgo/go/runtime/internal/atomic/atomic.c b/libgo/go/runtime/internal/atomic/atomic.c
index 24820f22a42..b87fae96bd3 100644
--- a/libgo/go/runtime/internal/atomic/atomic.c
+++ b/libgo/go/runtime/internal/atomic/atomic.c
@@ -7,7 +7,7 @@
 #include "runtime.h"
 
 uint32_t Load (uint32_t *ptr)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Load")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Load")
   __attribute__ ((no_split_stack));
 
 uint32_t
@@ -17,7 +17,7 @@ Load (uint32_t *ptr)
 }
 
 void *Loadp (void *ptr)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Loadp")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Loadp")
   __attribute__ ((no_split_stack));
 
 void *
@@ -27,7 +27,7 @@ Loadp (void *ptr)
 }
 
 uint64_t Load64 (uint64_t *ptr)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Load64")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Load64")
   __attribute__ ((no_split_stack));
 
 uint64_t
@@ -39,7 +39,7 @@ Load64 (uint64_t *ptr)
 }
 
 uintptr_t Loaduintptr (uintptr_t *ptr)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Loaduintptr")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Loaduintptr")
   __attribute__ ((no_split_stack));
 
 uintptr_t
@@ -49,7 +49,7 @@ Loaduintptr (uintptr_t *ptr)
 }
 
 uintgo Loaduint (uintgo *ptr)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Loaduint")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Loaduint")
   __attribute__ ((no_split_stack));
 
 uintgo
@@ -59,7 +59,7 @@ Loaduint (uintgo *ptr)
 }
 
 int64_t Loadint64 (int64_t *ptr)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Loadint64")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Loadint64")
   __attribute__ ((no_split_stack));
 
 int64_t
@@ -71,7 +71,7 @@ Loadint64 (int64_t *ptr)
 }
 
 uint32_t Xadd (uint32_t *ptr, int32_t delta)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Xadd")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Xadd")
   __attribute__ ((no_split_stack));
 
 uint32_t
@@ -81,7 +81,7 @@ Xadd (uint32_t *ptr, int32_t delta)
 }
 
 uint64_t Xadd64 (uint64_t *ptr, int64_t delta)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Xadd64")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Xadd64")
   __attribute__ ((no_split_stack));
 
 uint64_t
@@ -93,7 +93,7 @@ Xadd64 (uint64_t *ptr, int64_t delta)
 }
 
 uintptr_t Xadduintptr (uintptr_t *ptr, uintptr_t delta)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Xadduintptr")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Xadduintptr")
   __attribute__ ((no_split_stack));
 
 uintptr_t
@@ -103,7 +103,7 @@ Xadduintptr (uintptr_t *ptr, uintptr_t delta)
 }
 
 int64_t Xaddint64 (int64_t *ptr, int64_t delta)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Xaddint64")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Xaddint64")
   __attribute__ ((no_split_stack));
 
 int64_t
@@ -115,7 +115,7 @@ Xaddint64 (int64_t *ptr, int64_t delta)
 }
 
 uint32_t Xchg (uint32_t *ptr, uint32_t new)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Xchg")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Xchg")
   __attribute__ ((no_split_stack));
 
 uint32_t
@@ -125,7 +125,7 @@ Xchg (uint32_t *ptr, uint32_t new)
 }
 
 uint64_t Xchg64 (uint64_t *ptr, uint64_t new)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Xchg64")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Xchg64")
   __attribute__ ((no_split_stack));
 
 uint64_t
@@ -137,7 +137,7 @@ Xchg64 (uint64_t *ptr, uint64_t new)
 }
 
 uintptr_t Xchguintptr (uintptr_t *ptr, uintptr_t new)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Xchguintptr")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Xchguintptr")
   __attribute__ ((no_split_stack));
 
 uintptr_t
@@ -147,7 +147,7 @@ Xchguintptr (uintptr_t *ptr, uintptr_t new)
 }
 
 void And8 (uint8_t *ptr, uint8_t val)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.And8")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.And8")
   __attribute__ ((no_split_stack));
 
 void
@@ -157,7 +157,7 @@ And8 (uint8_t *ptr, uint8_t val)
 }
 
 void Or8 (uint8_t *ptr, uint8_t val)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Or8")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Or8")
   __attribute__ ((no_split_stack));
 
 void
@@ -167,7 +167,7 @@ Or8 (uint8_t *ptr, uint8_t val)
 }
 
 _Bool Cas (uint32_t *ptr, uint32_t old, uint32_t new)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Cas")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Cas")
   __attribute__ ((no_split_stack));
 
 _Bool
@@ -177,7 +177,7 @@ Cas (uint32_t *ptr, uint32_t old, uint32_t new)
 }
 
 _Bool Cas64 (uint64_t *ptr, uint64_t old, uint64_t new)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Cas64")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Cas64")
   __attribute__ ((no_split_stack));
 
 _Bool
@@ -189,7 +189,7 @@ Cas64 (uint64_t *ptr, uint64_t old, uint64_t new)
 }
 
 _Bool Casp1 (void **ptr, void *old, void *new)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Casp1")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Casp1")
   __attribute__ ((no_split_stack));
 
 _Bool
@@ -199,7 +199,7 @@ Casp1 (void **ptr, void *old, void *new)
 }
 
 _Bool Casuintptr (uintptr_t *ptr, uintptr_t old, uintptr_t new)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Casuintptr")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Casuintptr")
   __attribute__ ((no_split_stack));
 
 _Bool
@@ -209,7 +209,7 @@ Casuintptr (uintptr_t *ptr, uintptr_t old, uintptr_t new)
 }
 
 void Store (uint32_t *ptr, uint32_t val)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Store")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Store")
   __attribute__ ((no_split_stack));
 
 void
@@ -219,7 +219,7 @@ Store (uint32_t *ptr, uint32_t val)
 }
 
 void Store64 (uint64_t *ptr, uint64_t val)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Store64")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Store64")
   __attribute__ ((no_split_stack));
 
 void
@@ -231,7 +231,7 @@ Store64 (uint64_t *ptr, uint64_t val)
 }
 
 void Storeuintptr (uintptr_t *ptr, uintptr_t val)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.Storeuintptr")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.Storeuintptr")
   __attribute__ ((no_split_stack));
 
 void
@@ -241,7 +241,7 @@ Storeuintptr (uintptr_t *ptr, uintptr_t val)
 }
 
 void StorepNoWB (void *ptr, void *val)
-  __asm__ (GOSYM_PREFIX "runtime_internal_atomic.StorepNoWB")
+  __asm__ (GOSYM_PREFIX "runtime..z2finternal..z2fatomic.StorepNoWB")
   __attribute__ ((no_split_stack));
 
 void
diff --git a/libgo/go/runtime/mgc.go b/libgo/go/runtime/mgc.go
index 4ef982d9775..de84084b391 100644
--- a/libgo/go/runtime/mgc.go
+++ b/libgo/go/runtime/mgc.go
@@ -219,7 +219,7 @@ func gcenable() {
 	memstats.enablegc = true // now that runtime is initialized, GC is okay
 }
 
-//go:linkname setGCPercent runtime_debug.setGCPercent
+//go:linkname setGCPercent runtime..z2fdebug.setGCPercent
 func setGCPercent(in int32) (out int32) {
 	lock(&mheap_.lock)
 	out = gcpercent
diff --git a/libgo/go/runtime/mheap.go b/libgo/go/runtime/mheap.go
index 65622f4f967..eb98083fecc 100644
--- a/libgo/go/runtime/mheap.go
+++ b/libgo/go/runtime/mheap.go
@@ -1165,7 +1165,7 @@ func (h *mheap) scavenge(k int32, now, limit uint64) {
 	}
 }
 
-//go:linkname runtime_debug_freeOSMemory runtime_debug.freeOSMemory
+//go:linkname runtime_debug_freeOSMemory runtime..z2fdebug.freeOSMemory
 func runtime_debug_freeOSMemory() {
 	GC()
 	systemstack(func() { mheap_.scavenge(-1, ^uint64(0), 0) })
diff --git a/libgo/go/runtime/mstats.go b/libgo/go/runtime/mstats.go
index f54ce9ddb58..8aac8502e0b 100644
--- a/libgo/go/runtime/mstats.go
+++ b/libgo/go/runtime/mstats.go
@@ -477,7 +477,7 @@ func readmemstats_m(stats *MemStats) {
 	stats.StackSys += stats.StackInuse
 }
 
-//go:linkname readGCStats runtime_debug.readGCStats
+//go:linkname readGCStats runtime..z2fdebug.readGCStats
 func readGCStats(pauses *[]uint64) {
 	systemstack(func() {
 		readGCStats_m(pauses)
diff --git a/libgo/go/runtime/net_plan9.go b/libgo/go/runtime/net_plan9.go
index 77ae8c612d7..907c31975c7 100644
--- a/libgo/go/runtime/net_plan9.go
+++ b/libgo/go/runtime/net_plan9.go
@@ -8,12 +8,12 @@ import (
 	_ "unsafe"
 )
 
-//go:linkname runtime_ignoreHangup internal_poll.runtime_ignoreHangup
+//go:linkname runtime_ignoreHangup internal..z2fpoll.runtime_ignoreHangup
 func runtime_ignoreHangup() {
 	getg().m.ignoreHangup = true
 }
 
-//go:linkname runtime_unignoreHangup internal_poll.runtime_unignoreHangup
+//go:linkname runtime_unignoreHangup internal..z2fpoll.runtime_unignoreHangup
 func runtime_unignoreHangup(sig string) {
 	getg().m.ignoreHangup = false
 }
diff --git a/libgo/go/runtime/netpoll.go b/libgo/go/runtime/netpoll.go
index ab3d14d0dfd..6016b7d64f5 100644
--- a/libgo/go/runtime/netpoll.go
+++ b/libgo/go/runtime/netpoll.go
@@ -85,7 +85,7 @@ var (
 	netpollWaiters uint32
 )
 
-//go:linkname poll_runtime_pollServerInit internal_poll.runtime_pollServerInit
+//go:linkname poll_runtime_pollServerInit internal..z2fpoll.runtime_pollServerInit
 func poll_runtime_pollServerInit() {
 	netpollinit()
 	atomic.Store(&netpollInited, 1)
@@ -95,7 +95,7 @@ func netpollinited() bool {
 	return atomic.Load(&netpollInited) != 0
 }
 
-//go:linkname poll_runtime_pollServerDescriptor internal_poll.runtime_pollServerDescriptor
+//go:linkname poll_runtime_pollServerDescriptor internal..z2fpoll.runtime_pollServerDescriptor
 
 // poll_runtime_pollServerDescriptor returns the descriptor being used,
 // or ^uintptr(0) if the system does not use a poll descriptor.
@@ -103,7 +103,7 @@ func poll_runtime_pollServerDescriptor() uintptr {
 	return netpolldescriptor()
 }
 
-//go:linkname poll_runtime_pollOpen internal_poll.runtime_pollOpen
+//go:linkname poll_runtime_pollOpen internal..z2fpoll.runtime_pollOpen
 func poll_runtime_pollOpen(fd uintptr) (*pollDesc, int) {
 	pd := pollcache.alloc()
 	lock(&pd.lock)
@@ -127,7 +127,7 @@ func poll_runtime_pollOpen(fd uintptr) (*pollDesc, int) {
 	return pd, int(errno)
 }
 
-//go:linkname poll_runtime_pollClose internal_poll.runtime_pollClose
+//go:linkname poll_runtime_pollClose internal..z2fpoll.runtime_pollClose
 func poll_runtime_pollClose(pd *pollDesc) {
 	if !pd.closing {
 		throw("runtime: close polldesc w/o unblock")
@@ -149,7 +149,7 @@ func (c *pollCache) free(pd *pollDesc) {
 	unlock(&c.lock)
 }
 
-//go:linkname poll_runtime_pollReset internal_poll.runtime_pollReset
+//go:linkname poll_runtime_pollReset internal..z2fpoll.runtime_pollReset
 func poll_runtime_pollReset(pd *pollDesc, mode int) int {
 	err := netpollcheckerr(pd, int32(mode))
 	if err != 0 {
@@ -163,7 +163,7 @@ func poll_runtime_pollReset(pd *pollDesc, mode int) int {
 	return 0
 }
 
-//go:linkname poll_runtime_pollWait internal_poll.runtime_pollWait
+//go:linkname poll_runtime_pollWait internal..z2fpoll.runtime_pollWait
 func poll_runtime_pollWait(pd *pollDesc, mode int) int {
 	err := netpollcheckerr(pd, int32(mode))
 	if err != 0 {
@@ -185,7 +185,7 @@ func poll_runtime_pollWait(pd *pollDesc, mode int) int {
 	return 0
 }
 
-//go:linkname poll_runtime_pollWaitCanceled internal_poll.runtime_pollWaitCanceled
+//go:linkname poll_runtime_pollWaitCanceled internal..z2fpoll.runtime_pollWaitCanceled
 func poll_runtime_pollWaitCanceled(pd *pollDesc, mode int) {
 	// This function is used only on windows after a failed attempt to cancel
 	// a pending async IO operation. Wait for ioready, ignore closing or timeouts.
@@ -193,7 +193,7 @@ func poll_runtime_pollWaitCanceled(pd *pollDesc, mode int) {
 	}
 }
 
-//go:linkname poll_runtime_pollSetDeadline internal_poll.runtime_pollSetDeadline
+//go:linkname poll_runtime_pollSetDeadline internal..z2fpoll.runtime_pollSetDeadline
 func poll_runtime_pollSetDeadline(pd *pollDesc, d int64, mode int) {
 	lock(&pd.lock)
 	if pd.closing {
@@ -263,7 +263,7 @@ func poll_runtime_pollSetDeadline(pd *pollDesc, d int64, mode int) {
 	}
 }
 
-//go:linkname poll_runtime_pollUnblock internal_poll.runtime_pollUnblock
+//go:linkname poll_runtime_pollUnblock internal..z2fpoll.runtime_pollUnblock
 func poll_runtime_pollUnblock(pd *pollDesc) {
 	lock(&pd.lock)
 	if pd.closing {
diff --git a/libgo/go/runtime/pprof/mprof_test.go b/libgo/go/runtime/pprof/mprof_test.go
index 5d77a1d8986..f428827232a 100644
--- a/libgo/go/runtime/pprof/mprof_test.go
+++ b/libgo/go/runtime/pprof/mprof_test.go
@@ -87,19 +87,19 @@ func TestMemoryProfiler(t *testing.T) {
 
 		fmt.Sprintf(`%v: %v \[%v: %v\] @ 0x[0-9,a-f x]+
 #	0x[0-9,a-f]+	pprof\.allocatePersistent1K\+0x[0-9,a-f]+	.*/mprof_test\.go:40
-#	0x[0-9,a-f]+	runtime_pprof\.TestMemoryProfiler\+0x[0-9,a-f]+	.*/mprof_test\.go:74
+#	0x[0-9,a-f]+	runtime/pprof\.TestMemoryProfiler\+0x[0-9,a-f]+	.*/mprof_test\.go:74
 `, 32*memoryProfilerRun, 1024*memoryProfilerRun, 32*memoryProfilerRun, 1024*memoryProfilerRun),
 
 		fmt.Sprintf(`0: 0 \[%v: %v\] @ 0x[0-9,a-f x]+
 #	0x[0-9,a-f]+	pprof\.allocateTransient1M\+0x[0-9,a-f]+	.*/mprof_test.go:21
-#	0x[0-9,a-f]+	runtime_pprof\.TestMemoryProfiler\+0x[0-9,a-f]+	.*/mprof_test.go:72
+#	0x[0-9,a-f]+	runtime/pprof\.TestMemoryProfiler\+0x[0-9,a-f]+	.*/mprof_test.go:72
 `, (1<<10)*memoryProfilerRun, (1<<20)*memoryProfilerRun),
 
 		// This should start with "0: 0" but gccgo's imprecise
 		// GC means that sometimes the value is not collected.
 		fmt.Sprintf(`(0|%v): (0|%v) \[%v: %v\] @ 0x[0-9,a-f x]+
 #	0x[0-9,a-f]+	pprof\.allocateTransient2M\+0x[0-9,a-f]+	.*/mprof_test.go:27
-#	0x[0-9,a-f]+	runtime_pprof\.TestMemoryProfiler\+0x[0-9,a-f]+	.*/mprof_test.go:73
+#	0x[0-9,a-f]+	runtime/pprof\.TestMemoryProfiler\+0x[0-9,a-f]+	.*/mprof_test.go:73
 `, memoryProfilerRun, (2<<20)*memoryProfilerRun, memoryProfilerRun, (2<<20)*memoryProfilerRun),
 
 		// This should start with "0: 0" but gccgo's imprecise
diff --git a/libgo/go/runtime/proc.go b/libgo/go/runtime/proc.go
index 77d379be8f1..bb16924e01c 100644
--- a/libgo/go/runtime/proc.go
+++ b/libgo/go/runtime/proc.go
@@ -4670,7 +4670,7 @@ func runqsteal(_p_, p2 *p, stealRunNextG bool) *g {
 	return gp
 }
 
-//go:linkname setMaxThreads runtime_debug.setMaxThreads
+//go:linkname setMaxThreads runtime..z2fdebug.setMaxThreads
 func setMaxThreads(in int) (out int) {
 	lock(&sched.lock)
 	out = int(sched.maxmcount)
@@ -4716,13 +4716,13 @@ func sync_runtime_procUnpin() {
 	procUnpin()
 }
 
-//go:linkname sync_atomic_runtime_procPin sync_atomic.runtime_procPin
+//go:linkname sync_atomic_runtime_procPin sync..z2fatomic.runtime_procPin
 //go:nosplit
 func sync_atomic_runtime_procPin() int {
 	return procPin()
 }
 
-//go:linkname sync_atomic_runtime_procUnpin sync_atomic.runtime_procUnpin
+//go:linkname sync_atomic_runtime_procUnpin sync..z2fatomic.runtime_procUnpin
 //go:nosplit
 func sync_atomic_runtime_procUnpin() {
 	procUnpin()
diff --git a/libgo/go/runtime/proflabel.go b/libgo/go/runtime/proflabel.go
index ff73fe4856f..fc655cc8019 100644
--- a/libgo/go/runtime/proflabel.go
+++ b/libgo/go/runtime/proflabel.go
@@ -8,7 +8,7 @@ import "unsafe"
 
 var labelSync uintptr
 
-//go:linkname runtime_setProfLabel runtime_pprof.runtime_setProfLabel
+//go:linkname runtime_setProfLabel runtime..z2fpprof.runtime_setProfLabel
 func runtime_setProfLabel(labels unsafe.Pointer) {
 	// Introduce race edge for read-back via profile.
 	// This would more properly use &getg().labels as the sync address,
@@ -34,7 +34,7 @@ func runtime_setProfLabel(labels unsafe.Pointer) {
 	getg().labels = labels
 }
 
-//go:linkname runtime_getProfLabel runtime_pprof.runtime_getProfLabel
+//go:linkname runtime_getProfLabel runtime..z2fpprof.runtime_getProfLabel
 func runtime_getProfLabel() unsafe.Pointer {
 	return getg().labels
 }
diff --git a/libgo/go/runtime/rdebug.go b/libgo/go/runtime/rdebug.go
index 76535a905ac..358df111b55 100644
--- a/libgo/go/runtime/rdebug.go
+++ b/libgo/go/runtime/rdebug.go
@@ -11,14 +11,14 @@ import _ "unsafe" // for go:linkname
 // maxstacksize.
 var maxstacksize uintptr = 1 << 20 // enough until runtime.main sets it for real
 
-//go:linkname setMaxStack runtime_debug.setMaxStack
+//go:linkname setMaxStack runtime..z2fdebug.setMaxStack
 func setMaxStack(in int) (out int) {
 	out = int(maxstacksize)
 	maxstacksize = uintptr(in)
 	return out
 }
 
-//go:linkname setPanicOnFault runtime_debug.setPanicOnFault
+//go:linkname setPanicOnFault runtime..z2fdebug.setPanicOnFault
 func setPanicOnFault(new bool) (old bool) {
 	_g_ := getg()
 	old = _g_.paniconfault
diff --git a/libgo/go/runtime/runtime1.go b/libgo/go/runtime/runtime1.go
index 8b1b0a0b3b9..050f180c407 100644
--- a/libgo/go/runtime/runtime1.go
+++ b/libgo/go/runtime/runtime1.go
@@ -413,7 +413,7 @@ func parsedebugvars() {
 	traceback_env = traceback_cache
 }
 
-//go:linkname setTraceback runtime_debug.SetTraceback
+//go:linkname setTraceback runtime..z2fdebug.SetTraceback
 func setTraceback(level string) {
 	var t uint32
 	switch level {
diff --git a/libgo/go/runtime/sema.go b/libgo/go/runtime/sema.go
index cb7d3cdf8e1..273e8aa54d9 100644
--- a/libgo/go/runtime/sema.go
+++ b/libgo/go/runtime/sema.go
@@ -56,7 +56,7 @@ func sync_runtime_Semacquire(addr *uint32) {
 	semacquire1(addr, false, semaBlockProfile)
 }
 
-//go:linkname poll_runtime_Semacquire internal_poll.runtime_Semacquire
+//go:linkname poll_runtime_Semacquire internal..z2fpoll.runtime_Semacquire
 func poll_runtime_Semacquire(addr *uint32) {
 	semacquire1(addr, false, semaBlockProfile)
 }
@@ -71,7 +71,7 @@ func sync_runtime_SemacquireMutex(addr *uint32, lifo bool) {
 	semacquire1(addr, lifo, semaBlockProfile|semaMutexProfile)
 }
 
-//go:linkname poll_runtime_Semrelease internal_poll.runtime_Semrelease
+//go:linkname poll_runtime_Semrelease internal..z2fpoll.runtime_Semrelease
 func poll_runtime_Semrelease(addr *uint32) {
 	semrelease(addr)
 }
diff --git a/libgo/go/runtime/sigqueue.go b/libgo/go/runtime/sigqueue.go
index cf926a95689..1a29b207f81 100644
--- a/libgo/go/runtime/sigqueue.go
+++ b/libgo/go/runtime/sigqueue.go
@@ -117,7 +117,7 @@ Send:
 
 // Called to receive the next queued signal.
 // Must only be called from a single goroutine at a time.
-//go:linkname signal_recv os_signal.signal_recv
+//go:linkname signal_recv os..z2fsignal.signal_recv
 func signal_recv() uint32 {
 	for {
 		// Serve any signals from local copy.
@@ -161,7 +161,7 @@ func signal_recv() uint32 {
 // the signal(s) in question, and here we are just waiting to make sure
 // that all the signals have been delivered to the user channels
 // by the os/signal package.
-//go:linkname signalWaitUntilIdle os_signal.signalWaitUntilIdle
+//go:linkname signalWaitUntilIdle os..z2fsignal.signalWaitUntilIdle
 func signalWaitUntilIdle() {
 	// Although the signals we care about have been removed from
 	// sig.wanted, it is possible that another thread has received
@@ -181,7 +181,7 @@ func signalWaitUntilIdle() {
 }
 
 // Must only be called from a single goroutine at a time.
-//go:linkname signal_enable os_signal.signal_enable
+//go:linkname signal_enable os..z2fsignal.signal_enable
 func signal_enable(s uint32) {
 	if !sig.inuse {
 		// The first call to signal_enable is for us
@@ -208,7 +208,7 @@ func signal_enable(s uint32) {
 }
 
 // Must only be called from a single goroutine at a time.
-//go:linkname signal_disable os_signal.signal_disable
+//go:linkname signal_disable os..z2fsignal.signal_disable
 func signal_disable(s uint32) {
 	if s >= uint32(len(sig.wanted)*32) {
 		return
@@ -221,7 +221,7 @@ func signal_disable(s uint32) {
 }
 
 // Must only be called from a single goroutine at a time.
-//go:linkname signal_ignore os_signal.signal_ignore
+//go:linkname signal_ignore os..z2fsignal.signal_ignore
 func signal_ignore(s uint32) {
 	if s >= uint32(len(sig.wanted)*32) {
 		return
@@ -248,7 +248,7 @@ func sigInitIgnored(s uint32) {
 }
 
 // Checked by signal handlers.
-//go:linkname signal_ignored os_signal.signal_ignored
+//go:linkname signal_ignored os..z2fsignal.signal_ignored
 func signal_ignored(s uint32) bool {
 	i := atomic.Load(&sig.ignored[s/32])
 	return i&(1<<(s&31)) != 0
diff --git a/libgo/go/runtime/symtab.go b/libgo/go/runtime/symtab.go
index 861921c6f48..d137122137c 100644
--- a/libgo/go/runtime/symtab.go
+++ b/libgo/go/runtime/symtab.go
@@ -83,6 +83,11 @@ func (ci *Frames) Next() (frame Frame, more bool) {
 	if function == "" && file == "" {
 		return Frame{}, more
 	}
+
+	// Demangle function name if needed.
+	function = demangleSymbol(function)
+
+	// Create entry.
 	entry := funcentry(pc - 1)
 	f := &Func{name: function, entry: entry}
 
@@ -182,6 +187,75 @@ func (f *Func) FileLine(pc uintptr) (file string, line int) {
 	return file, line
 }
 
+func hexval(b byte) uint {
+	if b >= '0' && b <= '9' {
+		return uint(b - '0')
+	}
+	if b >= 'a' && b <= 'f' {
+		return uint(b-'a') + 10
+	}
+	return 0
+}
+
+func hexDigitsToRune(digits []byte, ndig int) rune {
+	result := uint(0)
+	for i := 0; i < ndig; i++ {
+		result <<= uint(4)
+		result |= hexval(digits[i])
+	}
+	return rune(result)
+}
+
+// Perform an in-place decoding on the input byte slice. This looks
+// for "..z<hex 2 >", "..u<hex x 4>" and "..U<hex x 8>" and overwrites
+// with the encoded bytes corresponding to the unicode in question.
+// Return value is the number of bytes taken by the result.
+
+func decodeIdentifier(bsl []byte) int {
+	j := 0
+	for i := 0; i < len(bsl); i++ {
+		b := bsl[i]
+
+		if i+1 < len(bsl) && bsl[i] == '.' && bsl[i+1] == '.' {
+			if i+4 < len(bsl) && bsl[i+2] == 'z' {
+				digits := bsl[i+3:]
+				r := hexDigitsToRune(digits, 2)
+				nc := encoderune(bsl[j:], r)
+				j += nc
+				i += 4
+				continue
+			} else if i+6 < len(bsl) && bsl[i+2] == 'u' {
+				digits := bsl[i+3:]
+				r := hexDigitsToRune(digits, 4)
+				nc := encoderune(bsl[j:], r)
+				j += nc
+				i += 6
+				continue
+			} else if i+10 < len(bsl) && bsl[i+2] == 'U' {
+				digits := bsl[i+3:]
+				r := hexDigitsToRune(digits, 8)
+				nc := encoderune(bsl[j:], r)
+				j += nc
+				i += 10
+				continue
+			}
+		}
+		bsl[j] = b
+		j += 1
+	}
+	return j
+}
+
+// Demangle a function symbol. Applies the reverse of go_encode_id()
+// as used in the compiler.
+
+func demangleSymbol(s string) string {
+	bsl := []byte(s)
+	nchars := decodeIdentifier(bsl)
+	bsl = bsl[:nchars]
+	return string(bsl)
+}
+
 // implemented in go-caller.c
 func funcfileline(uintptr, int32) (string, string, int)
 func funcentry(uintptr) uintptr
diff --git a/libgo/go/runtime/time.go b/libgo/go/runtime/time.go
index a95d95b87a6..ea61baa9195 100644
--- a/libgo/go/runtime/time.go
+++ b/libgo/go/runtime/time.go
@@ -441,7 +441,7 @@ func badTimer() {
 
 // Entry points for net, time to call nanotime.
 
-//go:linkname poll_runtimeNano internal_poll.runtimeNano
+//go:linkname poll_runtimeNano internal..z2fpoll.runtimeNano
 func poll_runtimeNano() int64 {
 	return nanotime()
 }
diff --git a/libgo/go/runtime/trace.go b/libgo/go/runtime/trace.go
index 7aed9a9b911..530d5e4c86e 100644
--- a/libgo/go/runtime/trace.go
+++ b/libgo/go/runtime/trace.go
@@ -1143,7 +1143,7 @@ func traceNextGC() {
 // To access runtime functions from runtime/trace.
 // See runtime/trace/annotation.go
 
-//go:linkname trace_userTaskCreate runtime_trace.userTaskCreate
+//go:linkname trace_userTaskCreate runtime..z2ftrace.userTaskCreate
 func trace_userTaskCreate(id, parentID uint64, taskType string) {
 	if !trace.enabled {
 		return
@@ -1161,12 +1161,12 @@ func trace_userTaskCreate(id, parentID uint64, taskType string) {
 	traceReleaseBuffer(pid)
 }
 
-//go:linkname trace_userTaskEnd runtime_trace.userTaskEnd
+//go:linkname trace_userTaskEnd runtime..z2ftrace.userTaskEnd
 func trace_userTaskEnd(id uint64) {
 	traceEvent(traceEvUserTaskEnd, 2, id)
 }
 
-//go:linkname trace_userRegion runtime_trace.userRegion
+//go:linkname trace_userRegion runtime..z2ftrace.userRegion
 func trace_userRegion(id, mode uint64, name string) {
 	if !trace.enabled {
 		return
@@ -1183,7 +1183,7 @@ func trace_userRegion(id, mode uint64, name string) {
 	traceReleaseBuffer(pid)
 }
 
-//go:linkname trace_userLog runtime_trace.userLog
+//go:linkname trace_userLog runtime..z2ftrace.userLog
 func trace_userLog(id uint64, category, message string) {
 	if !trace.enabled {
 		return
diff --git a/libgo/go/runtime/traceback_gccgo.go b/libgo/go/runtime/traceback_gccgo.go
index e97071e5ed0..7347cea71b2 100644
--- a/libgo/go/runtime/traceback_gccgo.go
+++ b/libgo/go/runtime/traceback_gccgo.go
@@ -110,9 +110,14 @@ func showframe(name string, gp *g) bool {
 }
 
 // isExportedRuntime reports whether name is an exported runtime function.
-// It is only for runtime functions, so ASCII A-Z is fine.
+// It is only for runtime functions, so ASCII A-Z is fine. Here also check
+// for mangled functions from runtime/<...>, which will be prefixed with
+// "runtime..z2f".
 func isExportedRuntime(name string) bool {
 	const n = len("runtime.")
+	if hasprefix(name, "runtime..z2f") {
+		return true
+	}
 	return len(name) > n && name[:n] == "runtime." && 'A' <= name[n] && name[n] <= 'Z'
 }
 
diff --git a/libgo/go/sync/atomic/atomic.c b/libgo/go/sync/atomic/atomic.c
index 07a43063b7c..6cc730ffe55 100644
--- a/libgo/go/sync/atomic/atomic.c
+++ b/libgo/go/sync/atomic/atomic.c
@@ -9,7 +9,7 @@
 #include "runtime.h"
 
 int32_t SwapInt32 (int32_t *, int32_t)
-  __asm__ (GOSYM_PREFIX "sync_atomic.SwapInt32")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.SwapInt32")
   __attribute__ ((no_split_stack));
 
 int32_t
@@ -19,7 +19,7 @@ SwapInt32 (int32_t *addr, int32_t new)
 }
 
 int64_t SwapInt64 (int64_t *, int64_t)
-  __asm__ (GOSYM_PREFIX "sync_atomic.SwapInt64")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.SwapInt64")
   __attribute__ ((no_split_stack));
 
 int64_t
@@ -31,7 +31,7 @@ SwapInt64 (int64_t *addr, int64_t new)
 }
 
 uint32_t SwapUint32 (uint32_t *, uint32_t)
-  __asm__ (GOSYM_PREFIX "sync_atomic.SwapUint32")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.SwapUint32")
   __attribute__ ((no_split_stack));
 
 uint32_t
@@ -41,7 +41,7 @@ SwapUint32 (uint32_t *addr, uint32_t new)
 }
 
 uint64_t SwapUint64 (uint64_t *, uint64_t)
-  __asm__ (GOSYM_PREFIX "sync_atomic.SwapUint64")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.SwapUint64")
   __attribute__ ((no_split_stack));
 
 uint64_t
@@ -53,7 +53,7 @@ SwapUint64 (uint64_t *addr, uint64_t new)
 }
 
 uintptr_t SwapUintptr (uintptr_t *, uintptr_t)
-  __asm__ (GOSYM_PREFIX "sync_atomic.SwapUintptr")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.SwapUintptr")
   __attribute__ ((no_split_stack));
 
 uintptr_t
@@ -63,7 +63,7 @@ SwapUintptr (uintptr_t *addr, uintptr_t new)
 }
 
 _Bool CompareAndSwapInt32 (int32_t *, int32_t, int32_t)
-  __asm__ (GOSYM_PREFIX "sync_atomic.CompareAndSwapInt32")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.CompareAndSwapInt32")
   __attribute__ ((no_split_stack));
 
 _Bool
@@ -73,7 +73,7 @@ CompareAndSwapInt32 (int32_t *val, int32_t old, int32_t new)
 }
 
 _Bool CompareAndSwapInt64 (int64_t *, int64_t, int64_t)
-  __asm__ (GOSYM_PREFIX "sync_atomic.CompareAndSwapInt64")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.CompareAndSwapInt64")
   __attribute__ ((no_split_stack));
 
 _Bool
@@ -85,7 +85,7 @@ CompareAndSwapInt64 (int64_t *val, int64_t old, int64_t new)
 }
 
 _Bool CompareAndSwapUint32 (uint32_t *, uint32_t, uint32_t)
-  __asm__ (GOSYM_PREFIX "sync_atomic.CompareAndSwapUint32")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.CompareAndSwapUint32")
   __attribute__ ((no_split_stack));
 
 _Bool
@@ -95,7 +95,7 @@ CompareAndSwapUint32 (uint32_t *val, uint32_t old, uint32_t new)
 }
 
 _Bool CompareAndSwapUint64 (uint64_t *, uint64_t, uint64_t)
-  __asm__ (GOSYM_PREFIX "sync_atomic.CompareAndSwapUint64")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.CompareAndSwapUint64")
   __attribute__ ((no_split_stack));
 
 _Bool
@@ -107,7 +107,7 @@ CompareAndSwapUint64 (uint64_t *val, uint64_t old, uint64_t new)
 }
 
 _Bool CompareAndSwapUintptr (uintptr_t *, uintptr_t, uintptr_t)
-  __asm__ (GOSYM_PREFIX "sync_atomic.CompareAndSwapUintptr")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.CompareAndSwapUintptr")
   __attribute__ ((no_split_stack));
 
 _Bool
@@ -117,7 +117,7 @@ CompareAndSwapUintptr (uintptr_t *val, uintptr_t old, uintptr_t new)
 }
 
 int32_t AddInt32 (int32_t *, int32_t)
-  __asm__ (GOSYM_PREFIX "sync_atomic.AddInt32")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.AddInt32")
   __attribute__ ((no_split_stack));
 
 int32_t
@@ -127,7 +127,7 @@ AddInt32 (int32_t *val, int32_t delta)
 }
 
 uint32_t AddUint32 (uint32_t *, uint32_t)
-  __asm__ (GOSYM_PREFIX "sync_atomic.AddUint32")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.AddUint32")
   __attribute__ ((no_split_stack));
 
 uint32_t
@@ -137,7 +137,7 @@ AddUint32 (uint32_t *val, uint32_t delta)
 }
 
 int64_t AddInt64 (int64_t *, int64_t)
-  __asm__ (GOSYM_PREFIX "sync_atomic.AddInt64")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.AddInt64")
   __attribute__ ((no_split_stack));
 
 int64_t
@@ -149,7 +149,7 @@ AddInt64 (int64_t *val, int64_t delta)
 }
 
 uint64_t AddUint64 (uint64_t *, uint64_t)
-  __asm__ (GOSYM_PREFIX "sync_atomic.AddUint64")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.AddUint64")
   __attribute__ ((no_split_stack));
 
 uint64_t
@@ -161,7 +161,7 @@ AddUint64 (uint64_t *val, uint64_t delta)
 }
 
 uintptr_t AddUintptr (uintptr_t *, uintptr_t)
-  __asm__ (GOSYM_PREFIX "sync_atomic.AddUintptr")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.AddUintptr")
   __attribute__ ((no_split_stack));
 
 uintptr_t
@@ -171,7 +171,7 @@ AddUintptr (uintptr_t *val, uintptr_t delta)
 }
 
 int32_t LoadInt32 (int32_t *addr)
-  __asm__ (GOSYM_PREFIX "sync_atomic.LoadInt32")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.LoadInt32")
   __attribute__ ((no_split_stack));
 
 int32_t
@@ -186,7 +186,7 @@ LoadInt32 (int32_t *addr)
 }
 
 int64_t LoadInt64 (int64_t *addr)
-  __asm__ (GOSYM_PREFIX "sync_atomic.LoadInt64")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.LoadInt64")
   __attribute__ ((no_split_stack));
 
 int64_t
@@ -203,7 +203,7 @@ LoadInt64 (int64_t *addr)
 }
 
 uint32_t LoadUint32 (uint32_t *addr)
-  __asm__ (GOSYM_PREFIX "sync_atomic.LoadUint32")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.LoadUint32")
   __attribute__ ((no_split_stack));
 
 uint32_t
@@ -218,7 +218,7 @@ LoadUint32 (uint32_t *addr)
 }
 
 uint64_t LoadUint64 (uint64_t *addr)
-  __asm__ (GOSYM_PREFIX "sync_atomic.LoadUint64")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.LoadUint64")
   __attribute__ ((no_split_stack));
 
 uint64_t
@@ -235,7 +235,7 @@ LoadUint64 (uint64_t *addr)
 }
 
 uintptr_t LoadUintptr (uintptr_t *addr)
-  __asm__ (GOSYM_PREFIX "sync_atomic.LoadUintptr")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.LoadUintptr")
   __attribute__ ((no_split_stack));
 
 uintptr_t
@@ -250,7 +250,7 @@ LoadUintptr (uintptr_t *addr)
 }
 
 void *LoadPointer (void **addr)
-  __asm__ (GOSYM_PREFIX "sync_atomic.LoadPointer")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.LoadPointer")
   __attribute__ ((no_split_stack));
 
 void *
@@ -265,7 +265,7 @@ LoadPointer (void **addr)
 }
 
 void StoreInt32 (int32_t *addr, int32_t val)
-  __asm__ (GOSYM_PREFIX "sync_atomic.StoreInt32")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.StoreInt32")
   __attribute__ ((no_split_stack));
 
 void
@@ -279,7 +279,7 @@ StoreInt32 (int32_t *addr, int32_t val)
 }
 
 void StoreInt64 (int64_t *addr, int64_t val)
-  __asm__ (GOSYM_PREFIX "sync_atomic.StoreInt64")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.StoreInt64")
   __attribute__ ((no_split_stack));
 
 void
@@ -295,7 +295,7 @@ StoreInt64 (int64_t *addr, int64_t val)
 }
 
 void StoreUint32 (uint32_t *addr, uint32_t val)
-  __asm__ (GOSYM_PREFIX "sync_atomic.StoreUint32")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.StoreUint32")
   __attribute__ ((no_split_stack));
 
 void
@@ -309,7 +309,7 @@ StoreUint32 (uint32_t *addr, uint32_t val)
 }
 
 void StoreUint64 (uint64_t *addr, uint64_t val)
-  __asm__ (GOSYM_PREFIX "sync_atomic.StoreUint64")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.StoreUint64")
   __attribute__ ((no_split_stack));
 
 void
@@ -325,7 +325,7 @@ StoreUint64 (uint64_t *addr, uint64_t val)
 }
 
 void StoreUintptr (uintptr_t *addr, uintptr_t val)
-  __asm__ (GOSYM_PREFIX "sync_atomic.StoreUintptr")
+  __asm__ (GOSYM_PREFIX "sync..z2fatomic.StoreUintptr")
   __attribute__ ((no_split_stack));
 
 void
diff --git a/libgo/testsuite/gotest b/libgo/testsuite/gotest
index 5631930d160..f1309aba39a 100755
--- a/libgo/testsuite/gotest
+++ b/libgo/testsuite/gotest
@@ -504,6 +504,35 @@ localname() {
 	echo $1 | sed 's/^main\./__main__./'
 }
 
+# Takes a list of tests derived from 'nm' output (whose symbols are mangled)
+# and emits a demangled list of tests, using only the terminal package.
+# Example:
+#
+#    Original symbol:   foo/bar/leaf.Mumble
+#    Mangled symbol:    foo..z2fbar..z2fleaf.Mumble
+#    Returned:          leaf.Mumble
+#
+symtogo() {
+  local s=""
+  local result=""
+  local ndots=""
+  for tp in $*
+  do
+    s=$(echo $tp | sed -e 's/\.\.z2f/%/g' | sed -e 's/.*%//')
+    # screen out methods (X.Y.Z)
+    ndots=$(echo $s | sed -e 's/\./ /g' | wc -w)
+    if [ $ndots -ne 2 ]; then
+      continue
+    fi
+    if [ -z "${result}" ]; then
+      result="${s}"
+    else
+      result="${result} ${s}"
+    fi
+  done
+  echo "$result" | sed -e 's/ /\n/g'
+}
+
 {
 	text="T"
 
@@ -514,26 +543,27 @@ localname() {
 	    text="[TD]"
 	fi
 
-	symtogo='sed -e s/_test\([^A-Za-z0-9]\)/XXXtest\1/ -e s/.*_\([^_]*\.\)/\1/ -e s/XXXtest/_test/'
-
 	# test functions are named TestFoo
 	# the grep -v eliminates methods and other special names
 	# that have multiple dots.
 	pattern='Test([^a-z].*)?'
 	# The -p option tells GNU nm not to sort.
 	# The -v option tells Solaris nm to sort by value.
-	tests=$($NM -p -v _gotest_.o $xofile | egrep " $text .*\."$pattern'$' | grep -v '[^ ]\..*\.' | fgrep -v ' __go_' | sed 's/.* //' | $symtogo)
+        testsyms=$($NM -p -v _gotest_.o $xofile | egrep " $text .*\."$pattern'$' | fgrep -v ' __go_' | egrep -v '\.\.\w+$' | sed 's/.* //')
+        tests=$(symtogo "$testsyms")
 	if [ "x$tests" = x ]; then
 		echo 'gotest: warning: no tests matching '$pattern in _gotest_.o $xofile 1>&2
 		exit 2
 	fi
 	# benchmarks are named BenchmarkFoo.
 	pattern='Benchmark([^a-z].*)?'
-	benchmarks=$($NM -p -v _gotest_.o $xofile | egrep " $text .*\."$pattern'$' | grep -v '[^ ]\..*\.' | fgrep -v ' __go_' | sed 's/.* //' | $symtogo)
+	benchmarksyms=$($NM -p -v _gotest_.o $xofile | egrep " $text .*\."$pattern'$' | fgrep -v ' __go_' | egrep -v '\.\.\w+$' | sed 's/.* //')
+        benchmarks=$(symtogo "$benchmarksyms")
 
 	# examples are named ExampleFoo
 	pattern='Example([^a-z].*)?'
-	examples=$($NM -p -v _gotest_.o $xofile | egrep " $text .*\."$pattern'$' | grep -v '[^ ]\..*\.' | fgrep -v ' __go_' | sed 's/.* //' | $symtogo)
+	examplesyms=$($NM -p -v _gotest_.o $xofile | egrep " $text .*\."$pattern'$' | fgrep -v ' __go_' | egrep -v '\.\.\w+$' | sed 's/.* //')
+	examples=$(symtogo "$examplesyms")
 
 	# package spec
 	echo 'package main'