cmd/link, plugin: always encode path

Both the linker and the plugin package were inconsistent
about when they applied the path encoding defined in
objabi.PathToPrefix. As a result, only some symbols from
a package path that required encoding were being found.

So always encoding the path.

Fixes #22295

Change-Id: Ife86c79ca20b2e9307008ed83885e193d32b7dc4
Reviewed-on: https://go-review.googlesource.com/72390
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

misc/cgo/testplugin/src/issue22295.pkg/main.go

@@ -0,0 +1,28 @@
+// Copyright 2017 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.
+
+// +build ignore
+
+package main
+
+import (
+	"log"
+	"plugin"
+)
+
+func main() {
+	p, err := plugin.Open("issue.22295.so")
+	if err != nil {
+		log.Fatal(err)
+	}
+	f, err := p.Lookup("F")
+	if err != nil {
+		log.Fatal(err)
+	}
+	const want = 2503
+	got := f.(func() int)()
+	if got != want {
+		log.Fatalf("got %d, want %d", got, want)
+	}
+}

misc/cgo/testplugin/src/issue22295.pkg/plugin.go

@@ -0,0 +1,16 @@
+// Copyright 2017 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.
+
+package main
+
+var f *int
+
+func init() {
+	f = new(int)
+	*f = 2503
+}
+
+func F() int { return *f }
+
+func main() {}

misc/cgo/testplugin/test.bash

@@ -80,3 +80,8 @@ GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -buildmode=plugin -o issue22175_pl
 GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -buildmode=plugin -o issue22175_plugin2.so src/issue22175/plugin2.go
 GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -o issue22175 src/issue22175/main.go
 ./issue22175
+
+# Test for issue 22295
+GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -buildmode=plugin -o issue.22295.so issue22295.pkg
+GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -o issue22295 src/issue22295.pkg/main.go
+./issue22295

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

@@ -782,10 +782,11 @@ func addstrdata1(ctxt *Link, arg string) {
 	if eq < 0 || dot < 0 {
 		Exitf("-X flag requires argument of the form importpath.name=value")
 	}
-	pkg := objabi.PathToPrefix(arg[:dot])
+	pkg := arg[:dot]
 	if ctxt.BuildMode == BuildModePlugin && pkg == "main" {
 		pkg = *flagPluginPath
 	}
+	pkg = objabi.PathToPrefix(pkg)
 	addstrdata(ctxt, pkg+arg[dot:eq], arg[eq+1:])
 }
 

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

@@ -230,7 +230,7 @@ func (d *deadcodepass) init() {
 			}
 			names = append(names, *flagEntrySymbol)
 			if d.ctxt.BuildMode == BuildModePlugin {
-				names = append(names, *flagPluginPath+".init", *flagPluginPath+".main", "go.plugin.tabs")
+				names = append(names, objabi.PathToPrefix(*flagPluginPath)+".init", objabi.PathToPrefix(*flagPluginPath)+".main", "go.plugin.tabs")
 
 				// We don't keep the go.plugin.exports symbol,
 				// but we do keep the symbols it refers to.

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

@@ -586,7 +586,7 @@ func (ctxt *Link) symtab() {
 		moduledata.AddUint(ctxt.Arch, 0)
 	}
 	if ctxt.BuildMode == BuildModePlugin {
-		addgostring(ctxt, moduledata, "go.link.thispluginpath", *flagPluginPath)
+		addgostring(ctxt, moduledata, "go.link.thispluginpath", objabi.PathToPrefix(*flagPluginPath))
 
 		pkghashes := ctxt.Syms.Lookup("go.link.pkghashes", 0)
 		pkghashes.Attr |= sym.AttrReachable

src/plugin/plugin_dlopen.go

@@ -49,37 +49,6 @@ func lastIndexByte(s string, c byte) int {
 	return -1
 }
 
-// pathToPrefix converts raw string to the prefix that will be used in the symbol
-// table. If modifying, modify the version in internal/obj/sym.go as well.
-func pathToPrefix(s string) string {
-	slash := lastIndexByte(s, '/')
-	// check for chars that need escaping
-	n := 0
-	for r := 0; r < len(s); r++ {
-		if c := s[r]; c <= ' ' || (c == '.' && r > slash) || c == '%' || c == '"' || c >= 0x7F {
-			n++
-		}
-	}
-
-	// quick exit
-	if n == 0 {
-		return s
-	}
-
-	// escape
-	const hex = "0123456789abcdef"
-	p := make([]byte, 0, len(s)+2*n)
-	for r := 0; r < len(s); r++ {
-		if c := s[r]; c <= ' ' || (c == '.' && r > slash) || c == '%' || c == '"' || c >= 0x7F {
-			p = append(p, '%', hex[c>>4], hex[c&0xF])
-		} else {
-			p = append(p, c)
-		}
-	}
-
-	return string(p)
-}
-
 func open(name string) (*Plugin, error) {
 	cPath := make([]byte, C.PATH_MAX+1)
 	cRelName := make([]byte, len(name)+1)
@@ -153,7 +122,7 @@ func open(name string) (*Plugin, error) {
 			symName = symName[1:]
 		}
 
-		fullName := pathToPrefix(pluginpath) + "." + symName
+		fullName := pluginpath + "." + symName
 		cname := make([]byte, len(fullName)+1)
 		copy(cname, fullName)