cmd/link, plugin: use full plugin path for symbols

Plumb the import path of a plugin package through to the linker, and
use it as the prefix on the exported symbol names.

Before this we used the basename of the plugin file as the prefix,
which could conflict and result in multiple loaded plugins sharing
symbols that are distinct.

Fixes #17155
Fixes #17579

Change-Id: I7ce966ca82d04e8507c0bcb8ea4ad946809b1ef5
Reviewed-on: https://go-review.googlesource.com/32355
Reviewed-by: Ian Lance Taylor <iant@golang.org>

1 files changed, 24 insertions, 17 deletions

diff --git a/src/runtime/plugin.go b/src/runtime/plugin.go
index 4a85a1f500..91fc275a65 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() map[string]interface{} {
+func plugin_lastmoduleinit() (path string, syms map[string]interface{}) {
 	md := firstmoduledata.next
 	if md == nil {
 		throw("runtime: no plugin module data")
@@ -19,20 +19,27 @@ 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")
+	for pmd := &firstmoduledata; pmd != md; pmd = pmd.next {
+		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")
+		}
 	}
 
 	// Initialize the freshly loaded module.
@@ -54,7 +61,7 @@ func plugin_lastmoduleinit() map[string]interface{} {
 	// 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))
+	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)
@@ -68,7 +75,7 @@ func plugin_lastmoduleinit() map[string]interface{} {
 		}
 		syms[name] = val
 	}
-	return syms
+	return md.pluginpath, syms
 }
 
 // inRange reports whether v0 or v1 are in the range [r0, r1].