154 lines
4 KiB
Go
154 lines
4 KiB
Go
// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:build (linux && cgo) || (darwin && cgo) || (freebsd && cgo) || (hurd & cgo)
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package plugin
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/*
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#cgo linux LDFLAGS: -ldl
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#include <dlfcn.h>
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#include <limits.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <stdio.h>
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static uintptr_t pluginOpen(const char* path, char** err) {
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void* h = dlopen(path, RTLD_NOW|RTLD_GLOBAL);
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if (h == NULL) {
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*err = (char*)dlerror();
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}
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return (uintptr_t)h;
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}
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static void* pluginLookup(uintptr_t h, const char* name, char** err) {
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void* r = dlsym((void*)h, name);
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if (r == NULL) {
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*err = (char*)dlerror();
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}
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return r;
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}
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*/
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import "C"
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import (
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"errors"
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"sync"
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"unsafe"
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)
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func open(name string) (*Plugin, error) {
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cPath := make([]byte, C.PATH_MAX+1)
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cRelName := make([]byte, len(name)+1)
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copy(cRelName, name)
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if C.realpath(
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(*C.char)(unsafe.Pointer(&cRelName[0])),
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(*C.char)(unsafe.Pointer(&cPath[0]))) == nil {
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return nil, errors.New(`plugin.Open("` + name + `"): realpath failed`)
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}
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filepath := C.GoString((*C.char)(unsafe.Pointer(&cPath[0])))
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pluginsMu.Lock()
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if p := plugins[filepath]; p != nil {
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pluginsMu.Unlock()
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if p.err != "" {
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return nil, errors.New(`plugin.Open("` + name + `"): ` + p.err + ` (previous failure)`)
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}
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<-p.loaded
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return p, nil
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}
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var cErr *C.char
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h := C.pluginOpen((*C.char)(unsafe.Pointer(&cPath[0])), &cErr)
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if h == 0 {
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pluginsMu.Unlock()
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return nil, errors.New(`plugin.Open("` + name + `"): ` + C.GoString(cErr))
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}
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// TODO(crawshaw): look for plugin note, confirm it is a Go plugin
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// and it was built with the correct toolchain.
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if len(name) > 3 && name[len(name)-3:] == ".so" {
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name = name[:len(name)-3]
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}
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if plugins == nil {
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plugins = make(map[string]*Plugin)
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}
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pluginpath, syms, errstr := lastmoduleinit()
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if errstr != "" {
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plugins[filepath] = &Plugin{
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pluginpath: pluginpath,
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err: errstr,
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}
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pluginsMu.Unlock()
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return nil, errors.New(`plugin.Open("` + name + `"): ` + errstr)
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}
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// This function can be called from the init function of a plugin.
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// Drop a placeholder in the map so subsequent opens can wait on it.
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p := &Plugin{
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pluginpath: pluginpath,
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loaded: make(chan struct{}),
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}
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plugins[filepath] = p
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pluginsMu.Unlock()
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initStr := make([]byte, len(pluginpath)+len("..inittask")+1) // +1 for terminating NUL
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copy(initStr, pluginpath)
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copy(initStr[len(pluginpath):], "..inittask")
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initTask := C.pluginLookup(h, (*C.char)(unsafe.Pointer(&initStr[0])), &cErr)
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if initTask != nil {
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doInit(initTask)
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}
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// Fill out the value of each plugin symbol.
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updatedSyms := map[string]any{}
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for symName, sym := range syms {
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isFunc := symName[0] == '.'
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if isFunc {
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delete(syms, symName)
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symName = symName[1:]
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}
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fullName := pluginpath + "." + symName
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cname := make([]byte, len(fullName)+1)
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copy(cname, fullName)
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p := C.pluginLookup(h, (*C.char)(unsafe.Pointer(&cname[0])), &cErr)
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if p == nil {
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return nil, errors.New(`plugin.Open("` + name + `"): could not find symbol ` + symName + `: ` + C.GoString(cErr))
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}
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valp := (*[2]unsafe.Pointer)(unsafe.Pointer(&sym))
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if isFunc {
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(*valp)[1] = unsafe.Pointer(&p)
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} else {
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(*valp)[1] = p
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}
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// we can't add to syms during iteration as we'll end up processing
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// some symbols twice with the inability to tell if the symbol is a function
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updatedSyms[symName] = sym
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}
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p.syms = updatedSyms
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close(p.loaded)
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return p, nil
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}
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func lookup(p *Plugin, symName string) (Symbol, error) {
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if s := p.syms[symName]; s != nil {
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return s, nil
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}
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return nil, errors.New("plugin: symbol " + symName + " not found in plugin " + p.pluginpath)
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}
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var (
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pluginsMu sync.Mutex
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plugins map[string]*Plugin
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)
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// lastmoduleinit is defined in package runtime
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func lastmoduleinit() (pluginpath string, syms map[string]any, errstr string)
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// doInit is defined in package runtime
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//go:linkname doInit runtime.doInit
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func doInit(t unsafe.Pointer) // t should be a *runtime.initTask
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