From d8730416ed4056b69d4a016bef7af1f1344f3331 Mon Sep 17 00:00:00 2001
From: Artem Chernyshev <artem.chernyshev@talos-systems.com>
Date: Fri, 19 Nov 2021 18:19:22 +0300
Subject: [PATCH] fix: return partition table not exist when trying to read an
 empty dev

Fixes: https://github.com/talos-systems/go-blockdevice/issues/51

Signed-off-by: Artem Chernyshev <artem.chernyshev@talos-systems.com>
---
 blockdevice/blockdevice_linux.go      |  4 ++++
 blockdevice/options.go                |  9 +++++++++
 blockdevice/partition/gpt/gpt.go      | 10 +++++++---
 blockdevice/partition/gpt/gpt_test.go | 24 +++++++++++++++++++++++-
 4 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/blockdevice/blockdevice_linux.go b/blockdevice/blockdevice_linux.go
index d8b771a..d761f31 100644
--- a/blockdevice/blockdevice_linux.go
+++ b/blockdevice/blockdevice_linux.go
@@ -74,6 +74,10 @@ func Open(devname string, setters ...Option) (bd *BlockDevice, err error) {
 		}
 	}
 
+	if opts.IgnoreGPT {
+		return bd, nil
+	}
+
 	if opts.CreateGPT {
 		var g *gpt.GPT
 
diff --git a/blockdevice/options.go b/blockdevice/options.go
index 9ef5509..e7ec3aa 100644
--- a/blockdevice/options.go
+++ b/blockdevice/options.go
@@ -7,6 +7,7 @@ package blockdevice
 // Options is the functional options struct.
 type Options struct {
 	CreateGPT     bool
+	IgnoreGPT     bool
 	ExclusiveLock bool
 	Mode          int
 }
@@ -35,10 +36,18 @@ func WithMode(value int) Option {
 	}
 }
 
+// WithoutGPT opens blockdevice ignoring GPT.
+func WithoutGPT(value bool) Option {
+	return func(args *Options) {
+		args.IgnoreGPT = value
+	}
+}
+
 // NewDefaultOptions initializes a Options struct with default values.
 func NewDefaultOptions(setters ...Option) *Options {
 	opts := &Options{
 		CreateGPT: false,
+		IgnoreGPT: false,
 		Mode:      DefaultMode,
 	}
 
diff --git a/blockdevice/partition/gpt/gpt.go b/blockdevice/partition/gpt/gpt.go
index c9cf452..640d055 100644
--- a/blockdevice/partition/gpt/gpt.go
+++ b/blockdevice/partition/gpt/gpt.go
@@ -26,11 +26,11 @@ const (
 
 var (
 	// ErrPartitionTableDoesNotExist indicates that the partition table does not exist.
-	ErrPartitionTableDoesNotExist = errors.New("does not exist")
+	ErrPartitionTableDoesNotExist = errors.New("block device partition table does not exist")
 	// ErrHeaderCRCMismatch indicates that the header CRC does not match what is on disk.
-	ErrHeaderCRCMismatch = errors.New("header CRC mismatch")
+	ErrHeaderCRCMismatch = errors.New("block device partition table header CRC mismatch")
 	// ErrEntriesCRCMismatch indicates that the partitions array CRC does not match what is on disk.
-	ErrEntriesCRCMismatch = errors.New("entries CRC mismatch")
+	ErrEntriesCRCMismatch = errors.New("block device partition table entries CRC mismatch")
 )
 
 type outOfSpaceError struct {
@@ -84,6 +84,10 @@ func Open(f *os.File) (g *GPT, err error) {
 			markMBRBootable: buf[0] == 0x80,
 		}
 
+		if err = h.DeserializeSignature(); err != nil {
+			return nil, ErrPartitionTableDoesNotExist
+		}
+
 		return g, nil
 	}
 
diff --git a/blockdevice/partition/gpt/gpt_test.go b/blockdevice/partition/gpt/gpt_test.go
index 7e73db6..21f1844 100644
--- a/blockdevice/partition/gpt/gpt_test.go
+++ b/blockdevice/partition/gpt/gpt_test.go
@@ -7,6 +7,7 @@ package gpt_test
 import (
 	"encoding/binary"
 	"os"
+	"os/exec"
 	"testing"
 
 	"github.com/stretchr/testify/suite"
@@ -35,7 +36,28 @@ func (suite *GPTSuite) SetupTest() {
 
 func (suite *GPTSuite) TestEmpty() {
 	_, err := gpt.Open(suite.Dev)
-	suite.Require().Error(err)
+	suite.Require().EqualError(err, gpt.ErrPartitionTableDoesNotExist.Error())
+}
+
+func (suite *GPTSuite) TestWiped() {
+	g, err := gpt.New(suite.Dev)
+	suite.Require().NoError(err)
+
+	_, err = g.Add(1048576, gpt.WithPartitionName("boot"))
+	suite.Require().NoError(err)
+
+	_, err = g.Add(1048576, gpt.WithPartitionName("efi"))
+	suite.Require().NoError(err)
+
+	suite.Require().NoError(g.Write())
+
+	suite.validatePMBR(0x00)
+
+	cmd := exec.Command("wipefs", "-a", suite.Dev.Name())
+	suite.Require().NoError(cmd.Run())
+
+	g, err = gpt.Open(suite.Dev)
+	suite.Require().EqualError(err, gpt.ErrPartitionTableDoesNotExist.Error())
 }
 
 func (suite *GPTSuite) TestReset() {