3 files changed, 84 insertions, 26 deletions

diff --git a/pkg/osutil/osutil_unix.go b/pkg/osutil/osutil_unix.go
index 0ab5dfd05..33cb09e40 100644
--- a/pkg/osutil/osutil_unix.go
+++ b/pkg/osutil/osutil_unix.go
@@ -96,33 +96,28 @@ func LongPipe() (io.ReadCloser, io.WriteCloser, error) {
 	return r, w, err
 }
 
+// ProcessExitStatus returns process exit status.
+// This is here only because of fuchsia that does not implement WaitStatus.
+func ProcessExitStatus(ps *os.ProcessState) int {
+	return ps.Sys().(syscall.WaitStatus).ExitStatus()
+}
+
 // CreateMemMappedFile creates a temp file with the requested size and maps it into memory.
 func CreateMemMappedFile(size int) (f *os.File, mem []byte, err error) {
-	f, err = ioutil.TempFile("./", "syzkaller-shm")
+	f, err = CreateSharedMemFile(size)
 	if err != nil {
-		err = fmt.Errorf("failed to create temp file: %v", err)
 		return
 	}
 	if err = f.Truncate(int64(size)); err != nil {
-		err = fmt.Errorf("failed to truncate shm file: %v", err)
-		f.Close()
-		os.Remove(f.Name())
-		return
-	}
-	f.Close()
-	fname := f.Name()
-	f, err = os.OpenFile(f.Name(), os.O_RDWR, DefaultFilePerm)
-	if err != nil {
-		err = fmt.Errorf("failed to open shm file: %v", err)
-		os.Remove(fname)
+		err = fmt.Errorf("failed to truncate shared mem file: %v", err)
+		CloseSharedMemFile(f)
 		return
 	}
+
 	mem, err = syscall.Mmap(int(f.Fd()), 0, size, syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED)
 	if err != nil {
 		err = fmt.Errorf("failed to mmap shm file: %v", err)
-		f.Close()
-		os.Remove(f.Name())
-		return
+		CloseSharedMemFile(f)
 	}
 	return
 }
@@ -130,22 +125,13 @@ func CreateMemMappedFile(size int) (f *os.File, mem []byte, err error) {
 // CloseMemMappedFile destroys memory mapping created by CreateMemMappedFile.
 func CloseMemMappedFile(f *os.File, mem []byte) error {
 	err1 := syscall.Munmap(mem)
-	err2 := f.Close()
-	err3 := os.Remove(f.Name())
+	err2 := CloseSharedMemFile(f)
 	switch {
 	case err1 != nil:
 		return err1
 	case err2 != nil:
 		return err2
-	case err3 != nil:
-		return err3
 	default:
 		return nil
 	}
 }
-
-// ProcessExitStatus returns process exit status.
-// This is here only because of fuchsia that does not implement WaitStatus.
-func ProcessExitStatus(ps *os.ProcessState) int {
-	return ps.Sys().(syscall.WaitStatus).ExitStatus()
-}
diff --git a/pkg/osutil/sharedmem_file.go b/pkg/osutil/sharedmem_file.go
new file mode 100644
index 000000000..1e969cdba
--- /dev/null
+++ b/pkg/osutil/sharedmem_file.go
@@ -0,0 +1,42 @@
+// Copyright 2021 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+//go:build freebsd || netbsd || openbsd || darwin
+// +build freebsd netbsd openbsd darwin
+
+package osutil
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+)
+
+func CreateSharedMemFile(size int) (f *os.File, err error) {
+	f, err = ioutil.TempFile("./", "syzkaller-shm")
+	if err != nil {
+		err = fmt.Errorf("failed to create temp file: %v", err)
+		return
+	}
+	f.Close()
+	fname := f.Name()
+	f, err = os.OpenFile(f.Name(), os.O_RDWR, DefaultFilePerm)
+	if err != nil {
+		err = fmt.Errorf("failed to open shm file: %v", err)
+		os.Remove(fname)
+	}
+	return
+}
+
+func CloseSharedMemFile(f *os.File) error {
+	err1 := f.Close()
+	err2 := os.Remove(f.Name())
+	switch {
+	case err1 != nil:
+		return err1
+	case err2 != nil:
+		return err2
+	default:
+		return nil
+	}
+}
diff --git a/pkg/osutil/sharedmem_memfd.go b/pkg/osutil/sharedmem_memfd.go
new file mode 100644
index 000000000..bdcea486f
--- /dev/null
+++ b/pkg/osutil/sharedmem_memfd.go
@@ -0,0 +1,30 @@
+// Copyright 2021 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+//go:build linux
+// +build linux
+
+package osutil
+
+import (
+	"fmt"
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+// In the case of Linux, we can just use the memfd_create syscall.
+func CreateSharedMemFile(size int) (f *os.File, err error) {
+	// The name is actually irrelevant and can even be the same for all such files.
+	fd, err := unix.MemfdCreate("syz-shared-mem", 0)
+	if err != nil {
+		err = fmt.Errorf("failed to do memfd_create: %v", err)
+		return
+	}
+	f = os.NewFile(uintptr(fd), fmt.Sprintf("/proc/self/fd/%d", fd))
+	return
+}
+
+func CloseSharedMemFile(f *os.File) error {
+	return f.Close()
+}