runtime: check plugin-loaded moduledata addresses

Inspired by difficulties with plugin support on darwin.

Change-Id: I2cef8410837946454e75d00e94e46791f03f2267
Reviewed-on: https://go-review.googlesource.com/29391Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/plugin.go

@@ -19,6 +19,22 @@ func plugin_lastmoduleinit() map[string]interface{} {
 		throw("runtime: plugin already initialized")
 	}
 
+	if fmd := &firstmoduledata; inRange(fmd.text, fmd.etext, md.text, md.etext) ||
+		inRange(fmd.bss, fmd.ebss, md.bss, md.ebss) ||
+		inRange(fmd.data, fmd.edata, md.data, md.edata) ||
+		inRange(fmd.types, fmd.etypes, md.types, md.etypes) {
+		println("plugin: new module data overlaps with firstmoduledata")
+		println("\tfirstmoduledata.text-etext=", hex(fmd.text), "-", hex(fmd.etext))
+		println("\tfirstmoduledata.bss-ebss=", hex(fmd.bss), "-", hex(fmd.ebss))
+		println("\tfirstmoduledata.data-edata=", hex(fmd.data), "-", hex(fmd.edata))
+		println("\tfirstmoduledata.types-etypes=", hex(fmd.types), "-", hex(fmd.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 firstmoduledata")
+	}
+
 	// Initialize the freshly loaded module.
 	typelinksinit()
 	md.gcdatamask = progToPointerMask((*byte)(unsafe.Pointer(md.gcdata)), md.edata-md.data)
@@ -55,6 +71,11 @@ func plugin_lastmoduleinit() map[string]interface{} {
 	return syms
 }
 
+// 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.