[release/v0.5] embedbin: implement fallback for missing memfd

internal/embedbin/embedbin.go

@@ -2,3 +2,11 @@
 //
 // The Install function creates a temporary file and writes the contents to it.
 package embedbin
+
+// Installed is a handle to an installed binary.
+// Users must call Uninstall to clean it up.
+type Installed interface {
+ Path() string
+ IsRegular() bool
+ Uninstall() error
+}

internal/embedbin/install_linux.go

@@ -3,20 +3,37 @@ package embedbin
 import (
  "fmt"
 
+ "github.com/spf13/afero"
  "golang.org/x/sys/unix"
 )
 
 // MemfdInstaller installs embedded binaries.
-type MemfdInstaller struct{}
+type MemfdInstaller struct {
+ fallback *RegularInstaller
+}
 
 // New returns a new installer.
 func New() *MemfdInstaller {
- return &MemfdInstaller{}
+ return &MemfdInstaller{
+ fallback: &RegularInstaller{fs: afero.NewOsFs()},
+ }
 }
 
 // Install creates a memfd and writes the contents to it.
 // the first argument is ignored on Linux (would be the prefix on other implementations).
-func (*MemfdInstaller) Install(_ string, contents []byte) (*MemfdInstall, error) {
+func (i *MemfdInstaller) Install(_ string, contents []byte) (Installed, error) {
+ // Try to install using memfd.
+ install, err := New().installMemfd(contents)
+ if err == nil {
+ return install, nil
+ }
+
+ // Fallback to regular installer.
+ return i.fallback.Install("", contents)
+}
+
+// installMemfd creates a memfd and writes the contents to it.
+func (*MemfdInstaller) installMemfd(contents []byte) (*MemfdInstall, error) {
  // Create a memfd.
  fd, err := unix.MemfdCreate("embedded-binary", 0)
  if err != nil {

internal/embedbin/regular.go

@@ -14,7 +14,7 @@ type RegularInstaller struct {
 // Install creates a regular file and writes the contents to it.
 // prefix is an optional prefix for the temporary file.
 // If prefix is empty, a temporary directory will be used.
-func (r *RegularInstaller) Install(prefix string, contents []byte) (*RegularInstall, error) {
+func (r *RegularInstaller) Install(prefix string, contents []byte) (Installed, error) {
  if prefix != "" {
  if err := r.fs.MkdirAll(prefix, os.ModePerm); err != nil {
  return nil, err