How to make sparse image file from original firmware?

Question

I accidently erased /system partition and now have my Gionee S10C phone bricked.

I downloaded original firmware, but I can see series of system image files.(This firmware is to be used by Qualcomm Flash Image Loader)

system_1.img, system_2.img, ..., system_53.img

When I'm trying to install the original firmware using QFIL by putting the phone in EDL mode, I get sahara fail error. (Same error in here and I tried most of the fixes I can find, but nothing works)

Now, is there any way to use the above 53 system images to restore my phone using fastboot flash command?

I'm sure only system partition is needed to be restored to get my phone working again, because I haven't modified any other partitions.

— Ming Soon | Sources

Answer

concatenate files with dd seek=$offset from xml and then sparse with img2simg

rawprogram0.xml contains

- partition name:
 filename="system.img"

- partition size:
 num_partition_sectors="8388608"

- partition offset:  start_sector="1312768"

rawprogram_unsparse.xml contains system_1.img - system_53.img

- file name:

filename="system_1.img"

- file size:

num_partition_sectors="262160"

- file offset:

 start_sector="1312768"

Note: we don't want the offset so we will subtract from start_sector

1312768 - 1312768 = 0

- file name:

filename="system_1.img"

- file size:

num_partition_sectors="262160"

- file offset:

 start_sector="0"

1576968 - 1312768 = 264200

- file name:

filename="system_2.img"

- file size:

num_partition_sectors="16"

- file offset:

 start_sector="264200"

1581024 - 1312768 = 268256

- file name:

filename="system_3.img"

- file size:

num_partition_sectors="256048"

- file offset:

 start_sector="268256"

Now use the dd seek parameter to paste junks into proper offsets

(sparse is filled with zeros)

bs=$SECTOR_SIZE_IN_BYTES

seek=$start_sector

count=$num_partition_sectors

dd if=system_1.img count=262160 seek=0

 bs=512 of=system_ext4.img

dd if=system_2.img count=16
  seek=264200  bs=512 of=system_ext4.img

dd if=system_3.img count=256048 seek=268256  bs=512 of=system_ext4.img

...

dd if=/dev/zero
 count=0

seek=8388608 bs=512 of=system_ext4.img

the result is mountable ext4 partition image

mkdir system

sudo mount -t ext4 -o loop system_ext4.img system

ls system

finally this file can be sparsed with img2simg

sudo apt install -y f2fs-tools android-tools-fsutils android-sdk-platform-tools-common

img2simg system_ext4.img system.img

GNU bash script with sed

#/bin/bash



shopt -s extglob



bs=512

label=system

input=rawprogram0.xml

output=rawprogram_unsparse.xml



source <(sed -nr "s,.*\s(filename=.${
label
}
\.img.)\s.*\s(num_partition_sectors=.[0-9]+.)\s.*\s(start_sector=.[0-9]+.).*,\1; \2; \3;,p" "$input" | head -n1)



out=$filename

off=${
start_sector:-0
}


end=${
num_partition_sectors:-0
}




printf '%s\n' "${
label
}
"_+([0-9]).img | cut -d. -f1 | sort -t_ -k2n | xargs -n1 -I_ echo _.img | \

while read -r file

  do


 source <(sed -nr "s,.*\s(filename=.${
file
}
.)\s.*\s(num_partition_sectors=.[0-9]+.)\s.*\s(start_sector=.[0-9]+.).*,\1; \2; \3;,p" "$output" | head -n1)


 dd if="$filename" of="$out" bs=${
bs:-512
}
 count=${
num_partition_sectors:-0
}
 seek=$((start_sector-off)) status=none || exit 1


 echo "filename=$filename num_partition_sectors=$num_partition_sectors start_sector=$((start_sector-off))"

done



dd if=/dev/zero of="$out" bs=${
bs:-512
}
 count=0 seek=$end status=none || exit 1

echo "filename=$out num_partition_sectors=$end start_sector=$off"



file "$out"

e2fsck -n "$out" | grep clean || exit 1

mv "$out" "${
out%.*
}
.raw"

img2simg "${
out%.*
}
.raw" "$out" || exit 1

file "$out"

echo "Done."



exit 0

— alecxs | Sources

How to make sparse image file from original firmware?

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