Building my own Recovery ROM for a Samsung J5 2017 (j5y17lte, TWRP)

After several hours of sideloading a custom ROM and flashing a TWRP recovery image i thought the next step is to build a TWRP recovery image on my own.

What is a TWRP recovery image?

So how to do that?

My startpoint was

https://github.com/Doge-Jxy17lte/twrp-jxy17lte

(just search github for your device with TWRP)

But this is not the way to begin.

First you have to follow this page:

https://github.com/minimal-manifest-twrp/platform_manifest_twrp_omni

and do

repo init -u git://github.com/minimal-manifest-twrp/platform_manifest_twrp_omni.git -b twrp-7.1

and

repo sync

Then add the j5y17lte.xml to .repo/local_manifests. After that the repo sync works but the

$ lunch omni_j5y17lte-eng

ends up with a warning:

WARNING: device/samsung/j5y17lte/omni.dependencies file not found

============================================

PLATFORM_VERSION_CODENAME=REL

PLATFORM_VERSION=7.1.2

TARGET_PRODUCT=omni_j5y17lte

TARGET_BUILD_VARIANT=eng

TARGET_BUILD_TYPE=release

TARGET_BUILD_APPS=

TARGET_ARCH=arm64

TARGET_ARCH_VARIANT=armv8-a

TARGET_CPU_VARIANT=cortex-a53

TARGET_2ND_ARCH=arm

TARGET_2ND_ARCH_VARIANT=armv7-a-neon

TARGET_2ND_CPU_VARIANT=cortex-a53

HOST_ARCH=x86_64

HOST_2ND_ARCH=x86

HOST_OS=linux

HOST_OS_EXTRA=Linux-4.15.0-88-generic-x86_64-with-Ubuntu-18.04-bionic

HOST_CROSS_OS=windows

HOST_CROSS_ARCH=x86

HOST_CROSS_2ND_ARCH=x86_64

HOST_BUILD_TYPE=release

BUILD_ID=NJH47F

OUT_DIR=/media/schroff/895337b7-c4eb-44a4-9063-00f629e5149f/omni/out

============================================

The good point: just ignore this warning and do the mka recoveryimage.

Here i got two errors:

/bin/bash -c "prebuilts/misc/linux-x86/flex/flex-2.5.39 -oout/target/product/generic/obj/STATIC_LIBRARIES/libedify_intermediates/lexer.cpp bootable/recovery/edify/lexer.ll"
flex-2.5.39: loadlocale.c:130: _nl_intern_locale_data: Assertion `cnt < (sizeof (_nl_value_type_LC_TIME) / sizeof (_nl_value_type_LC_TIME[0]))' failed.
Aborted (core dumped)

Here i followed this hint:
https://groups.google.com/forum/?hl=tr#!topic/android-building/0kzPnw3akxg
and copied the provided flex to "prebuilts/misc/linux-x86"
   cp ~/Downloads/build/flex flex-2.5.39

You have to change the name from flex to flex-2.5.39 and you have to rerun source build/envsetup.sh again.

Then i got the following errors:

bootable/recovery/gui/../twrp-functions.hpp:24:10: fatal error: 'ext4_utils/ext4_crypt.h' file not found

bootable/recovery/gui/../twrp-functions.hpp:24:10: error: 'ext4_utils/ext4_crypt.h' file not found with <angled> include; use "quotes" instead

bootable/recovery/twrp.cpp:49:10: fatal error: 'base/strings.h' file not found

This i could resolve with:

cd bootable/recovery

ln -s ../../system/extras/ext4_utils

vi twrp-functions.hpp # add the quotes!

ln -s ../../system/core/base/include/android-base base

After that the build went through and i got a TWRP image:

-rw-rw-r--  1 schroff schroff 26937344 Mai 17 23:40 recovery.img

This ran without a problem on my J5 after a

heimdall flash --RECOVERY recovery.img