From 904ce2993978f6cfbec986e051e55e34ad5d7292 Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Nikola=20Forr=C3=B3?= <nforro@redhat.com>

Date: Wed, 29 Sep 2021 15:33:33 +0200

Subject: [PATCH] Fix incorrect byte order of partition names on big-endian

 systems

---

 gdisk.8    |  8 ++++++++

 gptcl.cc   | 11 +++++++++++

 gptpart.cc | 13 +++++++------

 gptpart.h  |  1 +

 gpttext.cc | 20 ++++++++++++++++++++

 gpttext.h  |  1 +

 sgdisk.8   |  8 ++++++++

 7 files changed, 56 insertions(+), 6 deletions(-)

diff --git a/gdisk.8 b/gdisk.8

index c2cf83d..071756c 100644

--- a/gdisk.8

+++ b/gdisk.8

@@ -416,6 +416,14 @@ set features for each partition. \fBgdisk\fR supports four attributes:

 aren't translated into anything useful. In practice, most OSes seem to

 ignore these attributes.

+.TP 

+.B b

+Swap the byte order for the name of the specified partition. Some

+partitioning tools, including GPT fdisk 1.0.7 and earlier, can write the

+partition name in the wrong byte order on big-endian computers, such as the

+IBM s390 mainframes and PowerPC-based Macs. This feature corrects this

+problem.

+

 .TP 

 .B c

 Change partition GUID. You can enter a custom unique GUID for a partition

diff --git a/gptcl.cc b/gptcl.cc

index 6c36738..58afc8a 100644

--- a/gptcl.cc

+++ b/gptcl.cc

@@ -64,6 +64,7 @@ int GPTDataCL::DoOptions(int argc, char* argv[]) {

    GPTData secondDevice;

    int opt, numOptions = 0, saveData = 0, neverSaveData = 0;

    int partNum = 0, newPartNum = -1, saveNonGPT = 1, retval = 0, pretend = 0;

+   int byteSwapPartNum = 0;

    uint64_t low, high, startSector, endSector, sSize, mainTableLBA;

    uint64_t temp; // temporary variable; free to use in any case

    char *device;

@@ -76,6 +77,7 @@ int GPTDataCL::DoOptions(int argc, char* argv[]) {

           "list|[partnum:show|or|nand|xor|=|set|clear|toggle|get[:bitnum|hexbitmask]]"},

       {"set-alignment", 'a', POPT_ARG_INT, &alignment, 'a', "set sector alignment", "value"},

       {"backup", 'b', POPT_ARG_STRING, &backupFile, 'b', "backup GPT to file", "file"},

+      {"byte-swap-name", 'B',  POPT_ARG_INT, &byteSwapPartNum, 'B', "byte-swap partition's name", "partnum"},

       {"change-name", 'c', POPT_ARG_STRING, &partName, 'c', "change partition's name", "partnum:name"},

       {"recompute-chs", 'C', POPT_ARG_NONE, NULL, 'C', "recompute CHS values in protective/hybrid MBR", ""},

       {"delete", 'd', POPT_ARG_INT, &deletePartNum, 'd', "delete a partition", "partnum"},

@@ -191,6 +193,15 @@ int GPTDataCL::DoOptions(int argc, char* argv[]) {

                case 'a':

                   SetAlignment(alignment);

                   break;

+               case 'B':

+                  if (IsUsedPartNum(byteSwapPartNum - 1)) {

+                     partitions[byteSwapPartNum - 1].ReverseNameBytes();

+                     cout << "Changed partition " << byteSwapPartNum << "'s name to "

+                          << partitions[byteSwapPartNum - 1].GetDescription() << "\n";

+                     JustLooking(0);

+                     saveData = 1;

+                  }

+                  break;

                case 'b':

                   SaveGPTBackup(backupFile);

                   free(backupFile);

diff --git a/gptpart.cc b/gptpart.cc

index 17d6f15..c2b6500 100644

--- a/gptpart.cc

+++ b/gptpart.cc

@@ -234,7 +234,6 @@ void GPTPart::SetName(const string & theName) {

       // then to utf16le

       if ( uni < 0x10000 ) {

          name[ pos ] = (uint16_t) uni ;

-         if ( ! IsLittleEndian() ) ReverseBytes( name + pos , 2 ) ;

          pos ++ ;

       } // if

       else {

@@ -244,10 +243,8 @@ void GPTPart::SetName(const string & theName) {

          } // if

          uni -= 0x10000 ;

          name[ pos ] = (uint16_t)( uni >> 10 ) | 0xd800 ;

-         if ( ! IsLittleEndian() ) ReverseBytes( name + pos , 2 ) ;

          pos ++ ;

          name[ pos ] = (uint16_t)( uni & 0x3ff ) | 0xdc00 ;

-         if ( ! IsLittleEndian() ) ReverseBytes( name + pos , 2 ) ;

          pos ++ ;

       }

    } // for

@@ -407,14 +404,18 @@ int GPTPart::DoTheyOverlap(const GPTPart & other) {

 // Reverse the bytes of integral data types and of the UTF-16LE name;

 // used on big-endian systems.

 void GPTPart::ReversePartBytes(void) {

-   int i;

-

    ReverseBytes(&firstLBA, 8);

    ReverseBytes(&lastLBA, 8);

    ReverseBytes(&attributes, 8);

+   ReverseNameBytes();

+} // GPTPart::ReversePartBytes()

+

+void GPTPart::ReverseNameBytes(void) {

+   int i;

+

    for (i = 0; i < NAME_SIZE; i ++ )

       ReverseBytes(name + i, 2);

-} // GPTPart::ReverseBytes()

+} // GPTPart::ReverseNameBytes()

 /****************************************

  * Functions requiring user interaction *

diff --git a/gptpart.h b/gptpart.h

index 657b3f9..ac8a725 100644

--- a/gptpart.h

+++ b/gptpart.h

@@ -93,6 +93,7 @@ class GPTPart {

       void BlankPartition(void); // empty partition of data

       int DoTheyOverlap(const GPTPart & other); // returns 1 if there's overlap

       void ReversePartBytes(void); // reverse byte order of all integer fields

+      void ReverseNameBytes(void); // reverse byte order of partition's name field

       // Functions requiring user interaction

       void ChangeType(void); // Change the type code

diff --git a/gpttext.cc b/gpttext.cc

index 732d861..6de7121 100644

--- a/gpttext.cc

+++ b/gpttext.cc

@@ -341,6 +341,22 @@ int GPTDataTextUI::SetName(uint32_t partNum) {

    return retval;

 } // GPTDataTextUI::SetName()

+// Enable the user to byte-swap the name of the partition. Used to correct

+// partition names damaged by incorrect byte order, as could be created by

+// GPT fdisk 1.0.7 and earlier on big-endian systems, and perhaps other tools.

+void GPTDataTextUI::ReverseName(uint32_t partNum) {

+   int swapBytes;

+

+   cout << "Current name is: " << partitions[partNum].GetDescription() << "\n";

+   partitions[partNum].ReverseNameBytes();

+   cout << "Byte-swapped name is: " << partitions[partNum].GetDescription() << "\n";

+   cout << "Do you want to byte-swap the name? ";

+   swapBytes = (GetYN() == 'Y');

+   // Already swapped for display, so undo if necessary....

+   if (!swapBytes)

+      partitions[partNum].ReverseNameBytes();

+} // GPTDataTextUI::ReverseName()

+

 // Ask user for two partition numbers and swap them in the table. Note that

 // this just reorders table entries; it doesn't adjust partition layout on

 // the disk.

@@ -799,6 +815,9 @@ void GPTDataTextUI::ExpertsMenu(string filename) {

             else

                cout << "No partitions\n";

             break;

+         case 'b': case 'B':

+            ReverseName(GetPartNum());

+            break;

          case 'c': case 'C':

             ChangeUniqueGuid();

             break;

@@ -896,6 +915,7 @@ void GPTDataTextUI::ExpertsMenu(string filename) {

 void GPTDataTextUI::ShowExpertCommands(void) {

    cout << "a\tset attributes\n";

+   cout << "b\tbyte-swap a partition's name\n";

    cout << "c\tchange partition GUID\n";

    cout << "d\tdisplay the sector alignment value\n";

    cout << "e\trelocate backup data structures to the end of the disk\n";

diff --git a/gpttext.h b/gpttext.h

index 98e59af..db27246 100644

--- a/gpttext.h

+++ b/gpttext.h

@@ -49,6 +49,7 @@ class GPTDataTextUI : public GPTData {

       void ChangeUniqueGuid(void);

       void SetAttributes(uint32_t partNum);

       int SetName(uint32_t partNum);

+      void ReverseName(uint32_t partNum);

       int SwapPartitions(void);

       int DestroyGPTwPrompt(void); // Returns 1 if user proceeds

       void ShowDetails(void);

diff --git a/sgdisk.8 b/sgdisk.8

index 2cb18b9..3bc51f2 100644

--- a/sgdisk.8

+++ b/sgdisk.8

@@ -182,6 +182,14 @@ backup will reflect your changes. If the GPT data structures are damaged,

 the backup may not accurately reflect the damaged state; instead, they

 will reflect GPT fdisk's first\-pass interpretation of the GPT.

+.TP 

+.B \-B, \-\-byte\-swap\-name=partnum

+Swap the byte order for the name of the specified partition. Some

+partitioning tools, including GPT fdisk 1.0.7 and earlier, can write the

+partition name in the wrong byte order on big-endian computers, such as the

+IBM s390 mainframes and PowerPC-based Macs. This feature corrects this

+problem.

+

 .TP 

 .B \-c, \-\-change\-name=partnum:name

 Change the GPT name of a partition. This name is encoded as a UTF\-16

-- 

2.32.0