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Source file src/runtime/plugin.go

  // 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 runtime
  
  import "unsafe"
  
  //go:linkname plugin_lastmoduleinit plugin.lastmoduleinit
  func plugin_lastmoduleinit() (path string, syms map[string]interface{}, mismatchpkg string) {
  	md := firstmoduledata.next
  	if md == nil {
  		throw("runtime: no plugin module data")
  	}
  	for md.next != nil {
  		md = md.next
  	}
  	if md.typemap != nil {
  		throw("runtime: plugin already initialized")
  	}
  
  	for _, pmd := range activeModules() {
  		if pmd.pluginpath == md.pluginpath {
  			println("plugin: plugin", md.pluginpath, "already loaded")
  			throw("plugin: plugin already loaded")
  		}
  
  		if inRange(pmd.text, pmd.etext, md.text, md.etext) ||
  			inRange(pmd.bss, pmd.ebss, md.bss, md.ebss) ||
  			inRange(pmd.data, pmd.edata, md.data, md.edata) ||
  			inRange(pmd.types, pmd.etypes, md.types, md.etypes) {
  			println("plugin: new module data overlaps with previous moduledata")
  			println("\tpmd.text-etext=", hex(pmd.text), "-", hex(pmd.etext))
  			println("\tpmd.bss-ebss=", hex(pmd.bss), "-", hex(pmd.ebss))
  			println("\tpmd.data-edata=", hex(pmd.data), "-", hex(pmd.edata))
  			println("\tpmd.types-etypes=", hex(pmd.types), "-", hex(pmd.etypes))
  			println("\tmd.text-etext=", hex(md.text), "-", hex(md.etext))
  			println("\tmd.bss-ebss=", hex(md.bss), "-", hex(md.ebss))
  			println("\tmd.data-edata=", hex(md.data), "-", hex(md.edata))
  			println("\tmd.types-etypes=", hex(md.types), "-", hex(md.etypes))
  			throw("plugin: new module data overlaps with previous moduledata")
  		}
  	}
  	for _, pkghash := range md.pkghashes {
  		if pkghash.linktimehash != *pkghash.runtimehash {
  			return "", nil, pkghash.modulename
  		}
  	}
  
  	// Initialize the freshly loaded module.
  	modulesinit()
  	typelinksinit()
  
  	pluginftabverify(md)
  	moduledataverify1(md)
  
  	lock(&ifaceLock)
  	for _, i := range md.itablinks {
  		if i.inhash == 0 {
  			additab(i, true, false)
  		}
  	}
  	unlock(&ifaceLock)
  
  	// Build a map of symbol names to symbols. Here in the runtime
  	// we fill out the first word of the interface, the type. We
  	// pass these zero value interfaces to the plugin package,
  	// where the symbol value is filled in (usually via cgo).
  	//
  	// Because functions are handled specially in the plugin package,
  	// function symbol names are prefixed here with '.' to avoid
  	// a dependency on the reflect package.
  	syms = make(map[string]interface{}, len(md.ptab))
  	for _, ptab := range md.ptab {
  		symName := resolveNameOff(unsafe.Pointer(md.types), ptab.name)
  		t := (*_type)(unsafe.Pointer(md.types)).typeOff(ptab.typ)
  		var val interface{}
  		valp := (*[2]unsafe.Pointer)(unsafe.Pointer(&val))
  		(*valp)[0] = unsafe.Pointer(t)
  
  		name := symName.name()
  		if t.kind&kindMask == kindFunc {
  			name = "." + name
  		}
  		syms[name] = val
  	}
  	return md.pluginpath, syms, ""
  }
  
  func pluginftabverify(md *moduledata) {
  	badtable := false
  	for i := 0; i < len(md.ftab); i++ {
  		entry := md.ftab[i].entry
  		if md.minpc <= entry && entry <= md.maxpc {
  			continue
  		}
  
  		f := (*_func)(unsafe.Pointer(&md.pclntable[md.ftab[i].funcoff]))
  		name := funcname(f)
  
  		// A common bug is f.entry has a relocation to a duplicate
  		// function symbol, meaning if we search for its PC we get
  		// a valid entry with a name that is useful for debugging.
  		name2 := "none"
  		entry2 := uintptr(0)
  		f2 := findfunc(entry)
  		if f2 != nil {
  			name2 = funcname(f2)
  			entry2 = f2.entry
  		}
  		badtable = true
  		println("ftab entry outside pc range: ", hex(entry), "/", hex(entry2), ": ", name, "/", name2)
  	}
  	if badtable {
  		throw("runtime: plugin has bad symbol table")
  	}
  }
  
  // inRange reports whether v0 or v1 are in the range [r0, r1].
  func inRange(r0, r1, v0, v1 uintptr) bool {
  	return (v0 >= r0 && v0 <= r1) || (v1 >= r0 && v1 <= r1)
  }
  
  // A ptabEntry is generated by the compiler for each exported function
  // and global variable in the main package of a plugin. It is used to
  // initialize the plugin module's symbol map.
  type ptabEntry struct {
  	name nameOff
  	typ  typeOff
  }
  

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