Includes a linux implementation.
Change-Id: Iacc2ed7da760ae9deebc928adf2b334b043b07ec
Reviewed-on: https://go-review.googlesource.com/27823
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
"mime/quotedprintable": {"L4"},
"net/internal/socktest": {"L4", "OS", "syscall"},
"net/url": {"L4"},
+ "plugin": {"L0", "OS", "CGO"},
"text/scanner": {"L4", "OS"},
"text/template/parse": {"L4"},
--- /dev/null
+// Copyright 2016 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 plugin implements loading and symbol resolution of Go plugins.
+//
+// Currently plugins only work on Linux.
+//
+// A plugin is a Go main package with exported functions and variables that
+// has been built with:
+//
+// go build -buildmode=plugin
+//
+// When a plugin is first opened, the init functions of all packages not
+// already part of the program are called. The main function is not run.
+// A plugin is only initialized once, and cannot be closed.
+package plugin
+
+// Plugin is a loaded Go plugin.
+type Plugin struct {
+ name string
+ loaded chan struct{} // closed when loaded
+ syms map[string]interface{}
+}
+
+// Open opens a Go plugin.
+func Open(path string) (*Plugin, error) {
+ return open(path)
+}
+
+// Lookup searches for a symbol named symName in plugin p.
+// A symbol is any exported variable or function.
+// It reports an error if the symbol is not found.
+func (p *Plugin) Lookup(symName string) (Symbol, error) {
+ return lookup(p, symName)
+}
+
+// A Symbol is a pointer to a variable or function.
+//
+// For example, a plugin defined as
+//
+// package main
+//
+// // // No C code needed.
+// import "C"
+//
+// import "fmt"
+//
+// var V int
+//
+// func F() { fmt.Println("Hello, number %d", V) }
+//
+// may be loaded with the Open function and then the exported package
+// symbols V and F can be accessed
+//
+// p, err := plugin.Open("plugin_name.so")
+// if err != nil {
+// panic(err)
+// }
+// v, err := p.Lookup("V")
+// if err != nil {
+// panic(err)
+// }
+// f, err := p.Lookup("F")
+// if err != nil {
+// panic(err)
+// }
+// *v.(*int) = 7
+// f.(func())() // prints "Hello, number 7"
+type Symbol interface{}
--- /dev/null
+// Copyright 2016 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 linux,cgo
+
+package plugin
+
+/*
+#cgo linux LDFLAGS: -ldl
+#include <dlfcn.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <stdint.h>
+
+static uintptr_t pluginOpen(const char* path, char** err) {
+ void* h = dlopen(path, RTLD_NOW|RTLD_GLOBAL);
+ if (h == NULL) {
+ *err = dlerror();
+ }
+ return (uintptr_t)h;
+}
+
+static void* pluginLookup(uintptr_t h, const char* name, char** err) {
+ void* r = dlsym((void*)h, name);
+ if (r == NULL) {
+ *err = dlerror();
+ }
+ return r;
+}
+*/
+import "C"
+
+import (
+ "errors"
+ "sync"
+ "unsafe"
+)
+
+func open(name string) (*Plugin, error) {
+ pluginsMu.Lock()
+ cRelName := C.CString(name)
+ cPath := C.realpath(cRelName, nil)
+ C.free(unsafe.Pointer(cRelName))
+ defer C.free(unsafe.Pointer(cPath))
+ path := C.GoString(cPath)
+ if p := plugins[path]; p != nil {
+ pluginsMu.Unlock()
+ <-p.loaded
+ return p, nil
+ }
+ var cErr *C.char
+ h := C.pluginOpen(cPath, &cErr)
+ if h == 0 {
+ pluginsMu.Unlock()
+ return nil, errors.New("plugin.Open: " + C.GoString(cErr))
+ }
+ // TODO(crawshaw): look for plugin note, confirm it is a Go plugin
+ // and it was built with the correct toolchain.
+ // TODO(crawshaw): get full plugin name from note.
+ if len(name) > 3 && name[len(name)-3:] == ".so" {
+ name = name[:len(name)-3]
+ }
+ syms := lastmoduleinit()
+ if plugins == nil {
+ plugins = make(map[string]*Plugin)
+ }
+ // This function can be called from the init function of a plugin.
+ // Drop a placeholder in the map so subsequent opens can wait on it.
+ p := &Plugin{
+ name: name,
+ loaded: make(chan struct{}),
+ syms: syms,
+ }
+ plugins[path] = p
+ pluginsMu.Unlock()
+
+ initStr := C.CString(name + ".init")
+ initFuncPC := C.pluginLookup(h, initStr, &cErr)
+ C.free(unsafe.Pointer(initStr))
+ if initFuncPC != nil {
+ initFuncP := &initFuncPC
+ initFunc := *(*func())(unsafe.Pointer(&initFuncP))
+ initFunc()
+ }
+
+ // Fill out the value of each plugin symbol.
+ for symName, sym := range syms {
+ isFunc := symName[0] == '.'
+ if isFunc {
+ delete(syms, symName)
+ symName = symName[1:]
+ }
+
+ cname := C.CString(name + "." + symName)
+ p := C.pluginLookup(h, cname, &cErr)
+ C.free(unsafe.Pointer(cname))
+ if p == nil {
+ return nil, errors.New("plugin.Open: could not find symbol " + symName + ": " + C.GoString(cErr))
+ }
+ valp := (*[2]unsafe.Pointer)(unsafe.Pointer(&sym))
+ if isFunc {
+ (*valp)[1] = unsafe.Pointer(&p)
+ } else {
+ (*valp)[1] = p
+ }
+ syms[symName] = sym
+ }
+ close(p.loaded)
+ return p, nil
+}
+
+func lookup(p *Plugin, symName string) (Symbol, error) {
+ if s := p.syms[symName]; s != nil {
+ return s, nil
+ }
+ return nil, errors.New("plugin: symbol " + symName + " not found in plugin " + p.name)
+}
+
+var (
+ pluginsMu sync.Mutex
+ plugins map[string]*Plugin
+)
+
+func lastmoduleinit() map[string]interface{} // in package runtime
--- /dev/null
+// Copyright 2016 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 !linux !cgo
+
+package plugin
+
+import "errors"
+
+func lookup(p *Plugin, symName string) (interface{}, error) {
+ return nil, errors.New("plugin: not implemented")
+}
+
+func open(name string) (*Plugin, error) {
+ return nil, errors.New("plugin: not implemented")
+}
package runtime
+import "unsafe"
+
+//go:linkname plugin_lastmoduleinit plugin.lastmoduleinit
+func plugin_lastmoduleinit() map[string]interface{} {
+ md := firstmoduledata.next
+ if md == nil {
+ throw("runtime: no plugin module data")
+ }
+ for md.next != nil {
+ md = md.next
+ }
+ if md.typemap != nil {
+ throw("runtime: plugin already initialized")
+ }
+
+ // Initialize the freshly loaded module.
+ typelinksinit()
+ md.gcdatamask = progToPointerMask((*byte)(unsafe.Pointer(md.gcdata)), md.edata-md.data)
+ md.gcbssmask = progToPointerMask((*byte)(unsafe.Pointer(md.gcbss)), md.ebss-md.bss)
+
+ lock(&ifaceLock)
+ for _, i := range md.itablinks {
+ additab(i, true, false)
+ }
+ unlock(&ifaceLock)
+
+ // Build a map of symbol names to symbols. Here in the runtime
+ // we fill out the first word of the interface, the type. We
+ // pass these zero value interfaces to the plugin package,
+ // where the symbol value is filled in (usually via cgo).
+ //
+ // Because functions are handled specially in the plugin package,
+ // function symbol names are prefixed here with '.' to avoid
+ // a dependency on the reflect package.
+ syms := make(map[string]interface{}, len(md.ptab))
+ for _, ptab := range md.ptab {
+ symName := resolveNameOff(unsafe.Pointer(md.types), ptab.name)
+ t := (*_type)(unsafe.Pointer(md.types)).typeOff(ptab.typ)
+ var val interface{}
+ valp := (*[2]unsafe.Pointer)(unsafe.Pointer(&val))
+ (*valp)[0] = unsafe.Pointer(t)
+
+ name := symName.name()
+ if t.kind&kindMask == kindFunc {
+ name = "." + name
+ }
+ syms[name] = val
+ }
+ return syms
+}
+
// A ptabEntry is generated by the compiler for each exported function
// and global variable in the main package of a plugin. It is used to
// initialize the plugin module's symbol map.