From: Cherry Zhang <cherryyz@google.com>
Date: Mon, 21 Nov 2016 23:23:12 +0000 (-0500)
Subject: runtime/internal/atomic: crash on unaligned 64-bit ops on 32-bit MIPS
X-Git-Tag: go1.8beta1~82
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=526b2f85ce8e4b1b16f3122e0a5700c04b6de199;p=gostls13.git

runtime/internal/atomic: crash on unaligned 64-bit ops on 32-bit MIPS

This check was originally implemented by Vladimir in
https://go-review.googlesource.com/c/31489/1/src/runtime/internal/atomic/atomic_mipsx.go#30
but removed due to my comment (Sorry!). This CL adds it back.

Fixes #17786.

Change-Id: I7ff4c2539fc9e2afd8199964b587a8ccf093b896
Reviewed-on: https://go-review.googlesource.com/33431
Run-TryBot: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
---

diff --git a/src/runtime/internal/atomic/atomic_mipsx.go b/src/runtime/internal/atomic/atomic_mipsx.go
index 20b000c7a0..93a1f1a9dd 100644
--- a/src/runtime/internal/atomic/atomic_mipsx.go
+++ b/src/runtime/internal/atomic/atomic_mipsx.go
@@ -25,7 +25,11 @@ func spinUnlock(state *uint32)
 
 //go:nosplit
 func lockAndCheck(addr *uint64) {
-	//  force dereference before taking lock
+	// ensure 8-byte alignement
+	if uintptr(unsafe.Pointer(addr))&7 != 0 {
+		addr = nil
+	}
+	// force dereference before taking lock
 	_ = *addr
 
 	spinLock(&lock.state)
diff --git a/src/runtime/internal/atomic/atomic_test.go b/src/runtime/internal/atomic/atomic_test.go
index f7ba90a073..879a82f9c8 100644
--- a/src/runtime/internal/atomic/atomic_test.go
+++ b/src/runtime/internal/atomic/atomic_test.go
@@ -87,8 +87,8 @@ func TestUnaligned64(t *testing.T) {
 		if unsafe.Sizeof(int(0)) != 4 {
 			t.Skip("test only runs on 32-bit systems")
 		}
-	case "amd64p32", "mips", "mipsle":
-		// amd64p32 and mips can handle unaligned atomics.
+	case "amd64p32":
+		// amd64p32 can handle unaligned atomics.
 		t.Skipf("test not needed on %v", runtime.GOARCH)
 	}
 
diff --git a/src/sync/atomic/atomic_test.go b/src/sync/atomic/atomic_test.go
index c151f46fa9..6d0831c3f9 100644
--- a/src/sync/atomic/atomic_test.go
+++ b/src/sync/atomic/atomic_test.go
@@ -1401,8 +1401,8 @@ func TestUnaligned64(t *testing.T) {
 		if unsafe.Sizeof(int(0)) != 4 {
 			t.Skip("test only runs on 32-bit systems")
 		}
-	case "amd64p32", "mips", "mipsle":
-		// amd64p32 and mips can handle unaligned atomics.
+	case "amd64p32":
+		// amd64p32 can handle unaligned atomics.
 		t.Skipf("test not needed on %v", runtime.GOARCH)
 	}