cmd/link, runtime, plugin: versioning

In plugins and every program that opens a plugin, include a hash of
every imported package.

There are two versions of each hash: one local and one exported.
As the program starts and plugins are loaded, the first exported
symbol for each package becomes the canonical version.

Any subsequent plugin's local package hash symbol has to match the
canonical version.

Fixes #17832

Change-Id: I4e62c8e1729d322e14b1673bada40fa7a74ea8bc
Reviewed-on: https://go-review.googlesource.com/33161
Reviewed-by: Ian Lance Taylor <iant@golang.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/src/runtime/plugin.go b/src/runtime/plugin.go
index 7907936e14..845bf76e92 100644
--- a/src/runtime/plugin.go
+++ b/src/runtime/plugin.go
@@ -7,7 +7,7 @@ package runtime
 import "unsafe"
 
 //go:linkname plugin_lastmoduleinit plugin.lastmoduleinit
-func plugin_lastmoduleinit() (path string, syms map[string]interface{}) {
+func plugin_lastmoduleinit() (path string, syms map[string]interface{}, mismatchpkg string) {
 	md := firstmoduledata.next
 	if md == nil {
 		throw("runtime: no plugin module data")
@@ -41,6 +41,11 @@ func plugin_lastmoduleinit() (path string, syms map[string]interface{}) {
 			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()
@@ -74,7 +79,7 @@ func plugin_lastmoduleinit() (path string, syms map[string]interface{}) {
 		}
 		syms[name] = val
 	}
-	return md.pluginpath, syms
+	return md.pluginpath, syms, ""
 }
 
 // inRange reports whether v0 or v1 are in the range [r0, r1].