1 files changed, 155 insertions, 0 deletions
diff --git a/src/plugin/plugin_dlopen.go b/src/plugin/plugin_dlopen.go
new file mode 100644
index 0000000..6ba0f78
--- /dev/null
+++ b/src/plugin/plugin_dlopen.go
@@ -0,0 +1,155 @@
+// 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, 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()
+
+	initStr := make([]byte, len(pluginpath)+len("..inittask")+1) // +1 for terminating NUL
+	copy(initStr, pluginpath)
+	copy(initStr[len(pluginpath):], "..inittask")
+
+	initTask := C.pluginLookup(h, (*C.char)(unsafe.Pointer(&initStr[0])), &cErr)
+	if initTask != nil {
+		doInit(initTask)
+	}
+
+	// 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, errstr string)
+
+// doInit is defined in package runtime
+//
+//go:linkname doInit runtime.doInit
+func doInit(t unsafe.Pointer) // t should be a *runtime.initTask