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// 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 = (char*)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 = (char*)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
|
