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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.
//go:build (linux && cgo) || (darwin && cgo) || (freebsd && cgo)
package plugin
/*
#cgo linux LDFLAGS: -ldl
#include <dlfcn.h>
#include <limits.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdio.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) {
cPath := make([]byte, C.PATH_MAX+1)
cRelName := make([]byte, len(name)+1)
copy(cRelName, name)
if C.realpath(
(*C.char)(unsafe.Pointer(&cRelName[0])),
(*C.char)(unsafe.Pointer(&cPath[0]))) == nil {
return nil, errors.New(`plugin.Open("` + name + `"): realpath failed`)
}
filepath := C.GoString((*C.char)(unsafe.Pointer(&cPath[0])))
pluginsMu.Lock()
if p := plugins[filepath]; p != nil {
pluginsMu.Unlock()
if p.err != "" {
return nil, errors.New(`plugin.Open("` + name + `"): ` + p.err + ` (previous failure)`)
}
<-p.loaded
return p, nil
}
var cErr *C.char
h := C.pluginOpen((*C.char)(unsafe.Pointer(&cPath[0])), &cErr)
if h == 0 {
pluginsMu.Unlock()
return nil, errors.New(`plugin.Open("` + name + `"): ` + C.GoString(cErr))
}
// TODO(crawshaw): look for plugin note, confirm it is a Go plugin
// and it was built with the correct toolchain.
if len(name) > 3 && name[len(name)-3:] == ".so" {
name = name[:len(name)-3]
}
if plugins == nil {
plugins = make(map[string]*Plugin)
}
pluginpath, syms, initTasks, errstr := lastmoduleinit()
if errstr != "" {
plugins[filepath] = &Plugin{
pluginpath: pluginpath,
err: errstr,
}
pluginsMu.Unlock()
return nil, errors.New(`plugin.Open("` + name + `"): ` + errstr)
}
// 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{
pluginpath: pluginpath,
loaded: make(chan struct{}),
}
plugins[filepath] = p
pluginsMu.Unlock()
doInit(initTasks)
// Fill out the value of each plugin symbol.
updatedSyms := map[string]any{}
for symName, sym := range syms {
isFunc := symName[0] == '.'
if isFunc {
delete(syms, symName)
symName = symName[1:]
}
fullName := pluginpath + "." + symName
cname := make([]byte, len(fullName)+1)
copy(cname, fullName)
p := C.pluginLookup(h, (*C.char)(unsafe.Pointer(&cname[0])), &cErr)
if p == nil {
return nil, errors.New(`plugin.Open("` + name + `"): 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
}
// we can't add to syms during iteration as we'll end up processing
// some symbols twice with the inability to tell if the symbol is a function
updatedSyms[symName] = sym
}
p.syms = updatedSyms
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.pluginpath)
}
var (
pluginsMu sync.Mutex
plugins map[string]*Plugin
)
// lastmoduleinit is defined in package runtime.
func lastmoduleinit() (pluginpath string, syms map[string]any, inittasks []*initTask, errstr string)
// doInit is defined in package runtime.
//
//go:linkname doInit runtime.doInit
func doInit(t []*initTask)
type initTask struct {
// fields defined in runtime.initTask. We only handle pointers to an initTask
// in this package, so the contents are irrelevant.
}
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