Implemented running executables in memory

src/memfile/Exec_linux.go

@@ -0,0 +1,47 @@
+//go:build linux
+
+package memfile
+
+import (
+	"os"
+	"strconv"
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+// Exec executes an in-memory file.
+func Exec(file *os.File) error {
+	empty, err := syscall.BytePtrFromString("")
+
+	if err != nil {
+		return err
+	}
+
+	argv := []string{"/proc/self/fd/" + strconv.Itoa(int(file.Fd()))}
+	argvp, err := syscall.SlicePtrFromStrings(argv)
+
+	if err != nil {
+		return err
+	}
+
+	envv := os.Environ()
+	envvp, err := syscall.SlicePtrFromStrings(envv)
+
+	if err != nil {
+		return err
+	}
+
+	_, _, errno := syscall.Syscall6(
+		unix.SYS_EXECVEAT,
+		uintptr(file.Fd()),
+		uintptr(unsafe.Pointer(empty)),
+		uintptr(unsafe.Pointer(&argvp[0])),
+		uintptr(unsafe.Pointer(&envvp[0])),
+		uintptr(unix.AT_EMPTY_PATH),
+		0,
+	)
+
+	return errno
+}

src/memfile/Exec_other.go

@@ -0,0 +1,29 @@
+//go:build !linux
+
+package memfile
+
+import (
+	"os"
+	"os/exec"
+)
+
+// Exec executes an in-memory file.
+func Exec(file *os.File) error {
+	err := file.Chmod(0o700)
+
+	if err != nil {
+		return err
+	}
+
+	err = file.Close()
+
+	if err != nil {
+		return err
+	}
+
+	cmd := exec.Command(file.Name())
+	cmd.Stdout = os.Stdout
+	cmd.Stdin = os.Stdin
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}

src/memfile/New_linux.go

@@ -0,0 +1,21 @@
+//go:build linux
+
+package memfile
+
+import (
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+// New creates a new anonymous in-memory file.
+func New(name string) (*os.File, error) {
+	fd, err := unix.MemfdCreate(name, unix.MFD_CLOEXEC)
+
+	if err != nil {
+		return nil, err
+	}
+
+	memFile := os.NewFile(uintptr(fd), name)
+	return memFile, nil
+}

src/memfile/New_other.go

@@ -0,0 +1,12 @@
+//go:build !linux
+
+package memfile
+
+import (
+	"os"
+)
+
+// New creates a new anonymous in-memory file.
+func New(name string) (*os.File, error) {
+	return os.CreateTemp("", "")
+}

src/memfile/memfile_test.go

@@ -0,0 +1,15 @@
+package memfile_test
+
+import (
+	"testing"
+
+	"git.urbach.dev/cli/q/src/memfile"
+	"git.urbach.dev/go/assert"
+)
+
+func TestNew(t *testing.T) {
+	file, err := memfile.New("")
+	assert.Nil(t, err)
+	assert.NotNil(t, file)
+	// memfile.Exec can't be tested because it would replace the test executable
+}