| // 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. |
| // |
| // 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. |
| // |
| // # Warnings |
| // |
| // The ability to dynamically load parts of an application during |
| // execution, perhaps based on user-defined configuration, may be a |
| // useful building block in some designs. In particular, because |
| // applications and dynamically loaded functions can share data |
| // structures directly, plugins may enable very high-performance |
| // integration of separate parts. |
| // |
| // However, the plugin mechanism has many significant drawbacks that |
| // should be considered carefully during the design. For example: |
| // |
| // - Plugins are currently supported only on Linux, FreeBSD, and |
| // macOS, making them unsuitable for applications intended to be |
| // portable. |
| // |
| // - Applications that use plugins may require careful configuration |
| // to ensure that the various parts of the program be made available |
| // in the correct location in the file system (or container image). |
| // By contrast, deploying an application consisting of a single static |
| // executable is straightforward. |
| // |
| // - Reasoning about program initialization is more difficult when |
| // some packages may not be initialized until long after the |
| // application has started running. |
| // |
| // - Bugs in applications that load plugins could be exploited by an |
| // an attacker to load dangerous or untrusted libraries. |
| // |
| // - Runtime crashes are likely to occur unless all parts of the |
| // program (the application and all its plugins) are compiled |
| // using exactly the same version of the toolchain, the same build |
| // tags, and the same values of certain flags and environment |
| // variables. |
| // |
| // - Similar crashing problems are likely to arise unless all common |
| // dependencies of the application and its plugins are built from |
| // exactly the same source code. |
| // |
| // - Together, these restrictions mean that, in practice, the |
| // application and its plugins must all be built together by a |
| // single person or component of a system. In that case, it may |
| // be simpler for that person or component to generate Go source |
| // files that blank-import the desired set of plugins and then |
| // compile a static executable in the usual way. |
| // |
| // For these reasons, many users decide that traditional interprocess |
| // communication (IPC) mechanisms such as sockets, pipes, remote |
| // procedure call (RPC), shared memory mappings, or file system |
| // operations may be more suitable despite the performance overheads. |
| package plugin |
| |
| // Plugin is a loaded Go plugin. |
| type Plugin struct { |
| pluginpath string |
| err string // set if plugin failed to load |
| loaded chan struct{} // closed when loaded |
| syms map[string]any |
| } |
| |
| // Open opens a Go plugin. |
| // If a path has already been opened, then the existing *Plugin is returned. |
| // It is safe for concurrent use by multiple goroutines. |
| 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. |
| // It is safe for concurrent use by multiple goroutines. |
| 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 |
| // |
| // import "fmt" |
| // |
| // var V int |
| // |
| // func F() { fmt.Printf("Hello, number %d\n", 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 any |
