Sector 2-18 zeroed in first partition of msdoshd

[Junjus]

Description

Following xml results in a problem:

Problem

The first partition of msdos partition table is defined to start at sector 2.
The partition-table starts the first partition at sector 2.

• If a binary is defined inside the partition, then the binary should start from sector 2 onward.
  However sector 2-18 will be zeroed. The binary is overwritten / never-written in those sectors, while continuing correctly from sector 19 onward.
• If a ext4 partition is defined, the first superblock with 1024 byte offset (start sector 4), is zeroed. And all following sectors till sector 19.

Test Versions:

• used debian package: v14.8.1
• used git main: commit b6d36d3 Fix badly rendered ELBE sphinx docs

XML

<msdoshd>
    ...
    <first_partition_sector>2</first_partition_sector>
    <partition>
         ...
    </partition>
    ...
</msdoshd>

Trace Binary

Partition in partition-table

File attached: msdoshd.zip
losetup -P /dev/loop0 <image>

$ fdisk /dev/loop0

Welcome to fdisk (util-linux 2.36.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): p
Disk /dev/loop0: 550 MiB, 576716800 bytes, 1126400 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x874709fa

Device       Boot Start     End Sectors  Size Id Type
/dev/loop0p1          2    8193    8192    4M 83 Linux
...

Content of partition

hexdump -Cn 9296 --skip 512 <image>

00000200  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00002600  10 bd 2d e9 f7 45 14 46  0f 46 40 6a 1e 46 ff f7  |..-..E.F.F@j.F..|
00002610  9b ff 23 0a 7a 00 8d f8  04 40 8d f8 05 30 08 21  |..#.z....@...0.!|
00002620  23 0c 02 f0 fe 02 24 0e  8d f8 07 40 05 46 8d f8  |#.....$....@.F..|
00002630  06 30 ff f7 6c ff 4f f0  40 0a 04 46 0d f1 04 08  |.0..l.O.@..F....|
00002640  5c b9 00 2e 06 f1 ff 37  10 dc 4f f0 40 08 dd e9  |\......7..O.@...|
00002650

Trace ext4

msdoshd-ext4.zip

losetup -P /dev/loop0 <image>
hexdump -Cn 2048 /dev/loop0p1

00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000800

The result should have looked like, if defined outside sectors 2-18:

00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000400  90 88 00 00 ff 21 02 00  4c 1b 00 00 ad 58 00 00  |.....!..L....X..|
00000410  3f 4b 00 00 00 00 00 00  02 00 00 00 02 00 00 00  |?K..............|
00000420  00 80 00 00 00 80 00 00  50 1b 00 00 57 05 76 64  |........P...W.vd|
00000430  65 05 76 64 01 00 ff ff  53 ef 01 00 01 00 00 00  |e.vd....S.......|
00000440  57 05 76 64 00 00 00 00  00 00 00 00 01 00 00 00  |W.vd............|
00000450  00 00 00 00 0b 00 00 00  00 01 00 00 3c 00 00 00  |............<...|
00000460  c2 02 00 00 6b 04 00 00  a3 fd bd 36 fd d5 4a ce  |....k......6..J.|
00000470  ae ce 51 54 bc b8 d8 f8  72 6f 6f 74 66 73 00 00  |..QT....rootfs..|
00000480  00 00 00 00 00 00 00 00  2f 76 61 72 2f 63 61 63  |......../var/cac|
00000490  68 65 2f 65 6c 62 65 2f  66 63 63 37 36 32 38 62  |he/elbe/fcc7628b|
000004a0  2d 65 34 63 66 2d 34 38  63 61 2d 62 32 66 39 2d  |-e4cf-48ca-b2f9-|
000004b0  32 36 64 35 31 33 61 61  61 38 31 35 2f 69 6d 61  |26d513aaa815/ima|
000004c0  67 65 6d 6e 74 00 00 00  00 00 00 00 00 00 44 00  |gemnt.........D.|
000004d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000004e0  08 00 00 00 00 00 00 00  00 00 00 00 4d db 2d 3b  |............M.-;|
000004f0  96 4b 46 3c bb b7 7c 50  d0 f8 d4 c6 01 01 40 00  |.KF<..|P......@.|
00000500  0c 00 00 00 00 00 00 00  57 05 76 64 0a f3 01 00  |........W.vd....|
00000510  04 00 00 00 00 00 00 00  00 00 00 00 00 10 00 00  |................|
00000520  00 00 01 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000530  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000540  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 01  |................|
00000550  00 00 00 00 00 00 00 00  00 00 00 00 20 00 20 00  |............ . .|
00000560  01 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000570  00 00 00 00 04 01 00 00  fd 27 07 00 00 00 00 00  |.........'......|
00000580  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000640  00 00 00 00 00 00 00 00  65 19 00 00 00 00 00 00  |........e.......|
00000650  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000007f0  00 00 00 00 00 00 00 00  00 00 00 00 b8 a9 2d 52  |..............-R|
00000800