1 files changed, 136 insertions, 0 deletions
diff --git a/src/runtime/plugin.go b/src/runtime/plugin.go
new file mode 100644
index 0000000..5e05be7
--- /dev/null
+++ b/src/runtime/plugin.go
@@ -0,0 +1,136 @@
+// 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{}, errstr string) {
+	var md *moduledata
+	for pmd := firstmoduledata.next; pmd != nil; pmd = pmd.next {
+		if pmd.bad {
+			md = nil // we only want the last module
+			continue
+		}
+		md = pmd
+	}
+	if md == nil {
+		throw("runtime: no plugin module data")
+	}
+	if md.pluginpath == "" {
+		throw("runtime: plugin has empty pluginpath")
+	}
+	if md.typemap != nil {
+		return "", nil, "plugin already loaded"
+	}
+
+	for _, pmd := range activeModules() {
+		if pmd.pluginpath == md.pluginpath {
+			md.bad = true
+			return "", nil, "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 {
+			md.bad = true
+			return "", nil, "plugin was built with a different version of package " + pkghash.modulename
+		}
+	}
+
+	// Initialize the freshly loaded module.
+	modulesinit()
+	typelinksinit()
+
+	pluginftabverify(md)
+	moduledataverify1(md)
+
+	lock(&itabLock)
+	for _, i := range md.itablinks {
+		itabAdd(i)
+	}
+	unlock(&itabLock)
+
+	// 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 := funcInfo{(*_func)(unsafe.Pointer(&md.pclntable[md.ftab[i].funcoff])), md}
+		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.valid() {
+			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
+}