cmd/internal/ld, runtime: abort on shared library ABI mismatch

This:

1) Defines the ABI hash of a package (as the SHA1 of the __.PKGDEF)
2) Defines the ABI hash of a shared library (sort the packages by import
   path, concatenate the hashes of the packages and SHA1 that)
3) When building a shared library, compute the above value and define a
   global symbol that points to a go string that has the hash as its value.
4) When linking against a shared library, read the abi hash from the
   library and put both the value seen at link time and a reference
   to the global symbol into the moduledata.
5) During runtime initialization, check that the hash seen at link time
   still matches the hash the global symbol points to.

Change-Id: Iaa54c783790e6dde3057a2feadc35473d49614a5
Reviewed-on: https://go-review.googlesource.com/8773
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Michael Hudson-Doyle <michael.hudson@canonical.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/src/runtime/symtab.go b/src/runtime/symtab.go
index bbf00bf134..9afa954259 100644
--- a/src/runtime/symtab.go
+++ b/src/runtime/symtab.go
@@ -48,11 +48,24 @@ type moduledata struct {
 
 	typelinks []*_type
 
+	modulename   string
+	modulehashes []modulehash
+
 	gcdatamask, gcbssmask bitvector
 
 	next *moduledata
 }
 
+// For each shared library a module links against, the linker creates an entry in the
+// moduledata.modulehashes slice containing the name of the module, the abi hash seen
+// at link time and a pointer to the runtime abi hash. These are checked in
+// moduledataverify1 below.
+type modulehash struct {
+	modulename   string
+	linktimehash string
+	runtimehash  *string
+}
+
 var firstmoduledata moduledata  // linker symbol
 var lastmoduledatap *moduledata // linker symbol
 
@@ -117,6 +130,13 @@ func moduledataverify1(datap *moduledata) {
 		datap.maxpc != datap.ftab[nftab].entry {
 		throw("minpc or maxpc invalid")
 	}
+
+	for _, modulehash := range datap.modulehashes {
+		if modulehash.linktimehash != *modulehash.runtimehash {
+			println("abi mismatch detected between", datap.modulename, "and", modulehash.modulename)
+			throw("abi mismatch")
+		}
+	}
 }
 
 // FuncForPC returns a *Func describing the function that contains the