3 files changed, 120 insertions, 1 deletions
diff --git a/pkg/gohacks/BUILD b/pkg/gohacks/BUILD
index 35683fe98..b4e05f922 100644
--- a/pkg/gohacks/BUILD
+++ b/pkg/gohacks/BUILD
@@ -1,4 +1,4 @@
-load("//tools:defs.bzl", "go_library")
+load("//tools:defs.bzl", "go_library", "go_test")
 
 package(licenses = ["notice"])
 
@@ -10,3 +10,11 @@ go_library(
     stateify = False,
     visibility = ["//:sandbox"],
 )
+
+go_test(
+    name = "gohacks_test",
+    size = "small",
+    srcs = ["gohacks_test.go"],
+    library = ":gohacks",
+    deps = ["@org_golang_x_sys//unix:go_default_library"],
+)
diff --git a/pkg/gohacks/gohacks_test.go b/pkg/gohacks/gohacks_test.go
new file mode 100644
index 000000000..e18c8abc7
--- /dev/null
+++ b/pkg/gohacks/gohacks_test.go
@@ -0,0 +1,97 @@
+// Copyright 2021 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package gohacks
+
+import (
+	"io/ioutil"
+	"math/rand"
+	"os"
+	"runtime/debug"
+	"testing"
+
+	"golang.org/x/sys/unix"
+)
+
+func randBuf(size int) []byte {
+	b := make([]byte, size)
+	for i := range b {
+		b[i] = byte(rand.Intn(256))
+	}
+	return b
+}
+
+// Size of a page in bytes. Cloned from hostarch.PageSize to avoid a circular
+// dependency.
+const pageSize = 4096
+
+func testCopy(dst, src []byte) (panicked bool) {
+	defer func() {
+		if r := recover(); r != nil {
+			panicked = true
+		}
+	}()
+	debug.SetPanicOnFault(true)
+	copy(dst, src)
+	return panicked
+}
+
+func TestSegVOnMemmove(t *testing.T) {
+	// Test that SIGSEGVs received by runtime.memmove when *not* doing
+	// CopyIn or CopyOut work gets propagated to the runtime.
+	const bufLen = pageSize
+	a, err := unix.Mmap(-1, 0, bufLen, unix.PROT_NONE, unix.MAP_ANON|unix.MAP_PRIVATE)
+	if err != nil {
+		t.Fatalf("Mmap failed: %v", err)
+
+	}
+	defer unix.Munmap(a)
+	b := randBuf(bufLen)
+
+	if !testCopy(b, a) {
+		t.Fatalf("testCopy didn't panic when it should have")
+	}
+
+	if !testCopy(a, b) {
+		t.Fatalf("testCopy didn't panic when it should have")
+	}
+}
+
+func TestSigbusOnMemmove(t *testing.T) {
+	// Test that SIGBUS received by runtime.memmove when *not* doing
+	// CopyIn or CopyOut work gets propagated to the runtime.
+	const bufLen = pageSize
+	f, err := ioutil.TempFile("", "sigbus_test")
+	if err != nil {
+		t.Fatalf("TempFile failed: %v", err)
+	}
+	os.Remove(f.Name())
+	defer f.Close()
+
+	a, err := unix.Mmap(int(f.Fd()), 0, bufLen, unix.PROT_READ|unix.PROT_WRITE, unix.MAP_SHARED)
+	if err != nil {
+		t.Fatalf("Mmap failed: %v", err)
+
+	}
+	defer unix.Munmap(a)
+	b := randBuf(bufLen)
+
+	if !testCopy(b, a) {
+		t.Fatalf("testCopy didn't panic when it should have")
+	}
+
+	if !testCopy(a, b) {
+		t.Fatalf("testCopy didn't panic when it should have")
+	}
+}
diff --git a/pkg/gohacks/gohacks_unsafe.go b/pkg/gohacks/gohacks_unsafe.go
index 10bbb1f58..374aac2b4 100644
--- a/pkg/gohacks/gohacks_unsafe.go
+++ b/pkg/gohacks/gohacks_unsafe.go
@@ -75,3 +75,17 @@ func StringFromImmutableBytes(bs []byte) string {
 	// strings.Builder.String().
 	return *(*string)(unsafe.Pointer(&bs))
 }
+
+// Note that go:linkname silently doesn't work if the local name is exported,
+// necessitating an indirection for exported functions.
+
+// Memmove is runtime.memmove, exported for SeqAtomicLoad/SeqAtomicTryLoad<T>.
+//
+//go:nosplit
+func Memmove(to, from unsafe.Pointer, n uintptr) {
+	memmove(to, from, n)
+}
+
+//go:linkname memmove runtime.memmove
+//go:noescape
+func memmove(to, from unsafe.Pointer, n uintptr)