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How to build Helloword in android custom kernel

insmod: failed to load hello.ko: Function not implemented
during kernel build to logout message like 'hello world', I've got such an error, following steps will reproduce the bug:
1)I downloaded goldfish kernel from git clone https://android.googlesource.com/kernel/goldfish/ -b android-goldfish-3.18
2)also downloaded the toolchain coming with the above repo using git clone https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/x86/x86_64-linux-android-4.9
3)I changed directory to goldfish and created the paths mentioned in the documentation (github)
4)then i attempted to build the kernel using this sudo make ARCH=x86_64 CROSS_COMPILE=/home/ana/x86_64-linux-android-4.9-nougat-dev/bin/x86_64-linux-android- in the kernel directory (goldfish) and set LOADABLE_MODULES=y
5)In the next step, I created hello.c file and the Makefile related to it in helloKernel directory.
hello.c
#include<linux/module.h>
#include<linux/init.h>
#include<linux/kernel.h>
MODULE_AUTHOR("Robert P. J. Day");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_VERSION("2:1.0") ;
MODULE_DESCRIPTION("You have to start somewhere.");
static int hello_init(void){
printk(KERN_ALERT "Hello TheLittleNaruto it’s your first driver.\n");
return 0;
}
static void hello_exit(void){
printk(KERN_INFO "Goodbye TheLittleNaruto No point in keeping this driv er running.\n");
}
module_init(hello_init);
module_exit(hello_exit);
Makefile
obj-m := hello.o
KERNELDIR := /home/ana/goldfish/
PWD :=$(shell pwd)
ARCH=x86_64
CROSS_COMPILE=/home/ana/x86_64-linux-android-4.9-nougat-dev/bin/x86_64-linux-android-
CC=$(CROSS_COMPILE)gcc
LD=$(CROSS_COMPILE)ld
CFLAGS_MODULE=-fno-pic
modules:
make -C $(KERNELDIR) ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE) M=$(PWD) modules
clean:
rm *.o *.ko *.mod.c *.order *.symvers
in the same directory I created hello.ko with this sudo make ARCH=x86_64 CROSS_COMPILE=/home/ana/x86_64-linux-android-4.9-nougat-dev/bin/x86_64-linux-android-
7)and then i copied hello.ko to android emulator using sudo adb push hello.ko /data/local
8)and then i attempt insmod hello.ko in /data/local
and I get the above-mentioned error, please help me solve this problem. thanks in advance

two things to add in your code
function entry and exit routine
module_init(init_module);
module_exit(cleanup_module);
Let init_module function return 0 rather 1 because 0 means we are good.

How to fix cp issue during build with ninja?

I am currently compiling a custom recovery for an android phone. Sources are synced, device tree etc. all set up correctly. Now I am facing a rather banal-looking error during build. cp refuses to copy a directory, because -r is not specified in the build file.
I obviously tried to find the build file (rw_recovery/out/build_omni_daisy.ninja) and add the -r argument, but it seems to be regenerated at the beginning of every build process, as the process still fails and the previously changed line appears unchanged when opening the file after the attempted build.
These are the build steps:
. build/envsetup.sh
lunch omni_daisy-eng #config for the device
mka bootimage #device uses boot.img as recovery
This command leaves me with the following error:
[ 99% 6883/6884] Prebuilt (rw_recovery/out/target/product/daisy/kernel)
FAILED: rw_recovery/out/target/product/daisy/kernel
/bin/bash -c "(rm -f /home/luca/rw_recovery/out/target/product/daisy/kernel) && (cp rw_recovery/out/target/product/daisy/obj/KERNEL_OBJ/arch/arm64/boot/ rw_recovery/out/target/product/daisy/kernel )"
cp: -r not specified; omitting directory 'rw_recovery/out/target/product/daisy/obj/KERNEL_OBJ/arch/arm64/boot/'
ninja: build stopped: subcommand failed.
17:13:06 ninja failed with: exit status 1
I would love to hear any suggestions about how to force ninja to execute the command with -r. Alternatively, suggestions about where to find the file from which the above mentioned build file is recreated after executing mka command are much welcomed as well.

Native Code coverage with android soong build system

I'm trying to generate code coverage report for my native components with AOSP source code using soong build system.
I have extended aosp vhal but unit test cases are same as in below link.
http://androidxref.com/8.1.0_r33/xref/hardware/interfaces/automotive/vehicle/2.0/default/tests/
Tried adding below to cc_test, cc_binary in Android.bp
native_coverage : true,
cflags: [
"-g",
"-O0",
"-fprofile-arcs",
"-ftest-coverage",
],
ldflags : [
"-fprofile-arcs",
"-ftest-coverage",
],
Native binary unit-tests-coverage is generated in out/target/product but I can't find gcno intermediates for this.
Running below command gives me *.gcda files for each test files.
adb shell \
GCOV_PREFIX=/data/local/tmp \
GCOV_PREFIX_STRIP=`echo $ANDROID_BUILD_TOP | grep -o / | wc -l` \
/data/local/tmp/unit-tests-coverage
I have tried below links but not sure how to proceed :(
http://logan.tw/posts/2015/04/28/check-code-coverage-with-clang-and-lcov/
https://android.googlesource.com/platform/bionic.git/+/master-soong
https://android.googlesource.com/platform/build/soong/+/581341d%5E%21/
https://android.googlesource.com/platform/external/e2fsprogs/+/fedfb27%5E%21/
https://android.googlesource.com/platform/development/+/master/scripts/acov#23
http://androidxref.com/9.0.0_r3/xref/bionic/README.md#293
I'm not sure if google's vts framework can be used here to generate native code coverage.
https://codelabs.developers.google.com/codelabs/android-vts-8/#6
"gcnodir" is generated but not sure how to make use of it.
/coverage/data/nativetest64/vehicle-unit-tests-coverage/unit-tests-coverage.gcnodir

Posting answer to my question for other users on SO.
Install coverage tool :
sudo apt-get install lcov (This should install lcov-1.12)
sudo apt-get install gcc-4.6 (Clang generates .gcno approximately equal to gcc 4.2 that aren't compatible
with gcov-4.8. Installing gcc-4.6 to get gcov-4.6 and invoking lcov with '--gcov-tool /usr/bin/gcov-4.6')
Download LLVM 3.8 for llvm-cov to work : http://releases.llvm.org/download.html
All native unit test cases i.e instrumented binary needs to be executed on target. To build and emit clang's instrumentation based profiling. Example: http://androidxref.com/9.0.0_r3/xref/hardware/interfaces/automotive/vehicle/2.0/default/Android.bp#82 (Renamed to vehicle-manager-unit-test for shorter name)
export NATIVE_COVERAGE=true
Add native_coverage: true to test module in Android.bp
Go to: module-name/test
Use mm or make command to build native binary
Ex: For hardware/interfaces/automotive/vehicle/2.0/default/tests/ :
mma or make vehicle-manager-unit-test -j32
Copy coverage enabled instrumented binary to target
adb push out/target/product/product_name/data/nativetest64/vendor/vehicle-manager-unit-test /data/nativetest64/vehicle-manager-unit-test
adb shell chmod +x /data/nativetest64/vehicle-manager-unit-test
Run test cases and generate .gcda files
adb shell \
GCOV_PREFIX=/data/local/tmp \
GCOV_PREFIX_STRIP=echo $ANDROID_BUILD_TOP | grep -o / | wc -l \
/data/nativetest64/vehicle-manager-unit-test
adb shell find -iname *.gcda
adb pull /data/local/tmp/proc/self/cwd/out/soong/.intermediates/hardware/interfaces/automotive/vehicle/2.0/default/vehicle-manager-unit-test/android_x86_64_silvermont_vendor_cov/obj/hardware/interfaces/automotive/vehicle/2.0/default/tests/ .(Destination folder)
Extract GCNO files from GCNODIR (archive file generated at
out/overage/data/nativetest64/vendor/vehicle-manager-unit-test ) to
same folder with GCDA files
llvm-cov gcov -f -b *.gcda (https://llvm.org/docs/CommandGuide/llvm-cov.html )
lcov --directory . --base-directory . --gcov-tool /usr/bin/gcov-4.6 --capture -o cov.info (http://ltp.sourceforge.net/coverage/lcov.php)
genhtml cov.info -o output
Here's the script which wraps all these commands:
https://gist.github.com/pankajgangwar/f070b8b54e83543f8e3638dcd2cae1b8

here it is explaned how to generate coverage reports, which do require GTest:
these flags enable the generation of test coverage: -fprofile-arcs -ftest-coverage
then one has to use gcov: gcov main_test.cpp
which's output then can be passed on to lcov (for reference):
$ lcov --coverage --directory . --output-file main_coverage.info
from which one can generate an lcov coverage report in HTML format:
$ genhtml main_coverage.info --output-directory out
these .gcda files in .gcnodir are gcov data files. gcov also has an output option --json-format, which might come handy when wanting to consume the coverage data with a web-service.
one of the examples from the links you've provided can be used to generate it for a whole project:
Collect the code coverage results:
$ lcov --directory . \
--base-directory . \
--gcov-tool gcov.sh \
--capture -o cov.info
Generate HTML files:
$ genhtml cov.info -o output
where the only difference is, that the wrapper script would need to be adjusted to call gcov. probably one could even omit the wrapper passed with option --gcov-tool, since it should be directly called.
since one can only prepare the coverage report by adding the compiler flags, the gcov and lcov commands should be setup as post-build script, so that they would automatically generate the report.

How to setup Facebook Redex in order to optimize Android Bytecodes?

There is a very good instruction in Redex page at http://fbredex.com/.
I follow the instruction but I have problem in two steps.
1.I have no problem with run of first command (my OS is Ubuntu)
sudo apt-get install \
g++ \
automake \
autoconf \
autoconf-archive \
libtool \
libboost-all-dev \
libevent-dev \
libdouble-conversion-dev \
libgoogle-glog-dev \
libgflags-dev \
liblz4-dev \
liblzma-dev \
libsnappy-dev \
make \
zlib1g-dev \
binutils-dev \
libjemalloc-dev \
libssl-dev \
libiberty-dev
I clone folly repo somewhere on my laptop
I go to the directory by $ cd android/projects/folly/folly/
I run git submodule update --init but nothing happens. I even run this command in $ cd android/projects/folly/ but nothing happens either.
I run autoreconf -ivf && ./configure && make && make install. Seems works as I see process takes around a minute or two and there are a lot og messages print out.
I copy/paste a sample .apk file to my Desktop and run redex ~/Desktop/my_android_app.apk -o ~/Desktop/my_android_app-redexed.apk. However, I'm getting this message on terminal.
No command 'redex' found, did you mean: Command 'redet' from package
'redet' (universe) redex: command not found
I ran above command when I am in /home/hesam/android/projects/folly/folly or /home/hesam/android/projects/folly/. But I get same output.
Update
I cloned Redex repo and followed Bert's Instruction. It works and I could see something is happening by running git submodule update --init. So thanks to Bert. However, I got error at the end of autoreconf -ivf && ./configure && make && make install command.
Please have a look at following output:
Making all in unit
make[3]: Entering directory `/home/hesam/android/projects/redex/test/unit'
make[3]: Nothing to be done for `all'.
make[3]: Leaving directory `/home/hesam/android/projects/redex/test/unit'
make[2]: Leaving directory `/home/hesam/android/projects/redex/test'
make[1]: Leaving directory `/home/hesam/android/projects/redex'
Making install in third-party/folly/folly
make[1]: Entering directory `/home/hesam/android/projects/redex/third-party/folly/folly'
Making install in .
make[2]: Entering directory `/home/hesam/android/projects/redex/third-party/folly/folly'
make[3]: Entering directory `/home/hesam/android/projects/redex/third-party/folly/folly'
/bin/mkdir -p '/usr/local/lib'
/bin/bash ./libtool --mode=install /usr/bin/install -c libfolly.la libfollybenchmark.la '/usr/local/lib'
libtool: install: /usr/bin/install -c .libs/libfolly.so.57.0.0 /usr/local/lib/libfolly.so.57.0.0
/usr/bin/install: cannot create regular file '/usr/local/lib/libfolly.so.57.0.0': Permission denied
make[3]: *** [install-libLTLIBRARIES] Error 1
make[3]: Leaving directory `/home/hesam/android/projects/redex/third-party/folly/folly'
make[2]: *** [install-am] Error 2
make[2]: Leaving directory `/home/hesam/android/projects/redex/third-party/folly/folly'
make[1]: *** [install-recursive] Error 1
make[1]: Leaving directory `/home/hesam/android/projects/redex/third-party/folly/folly'
make: *** [install-recursive] Error 1
hesam: redex (master) $ redex ~/Desktop/my_android_app.apk -o ~/Desktop/my_android_app-redexed.apk
No command 'redex' found, did you mean:
Command 'redet' from package 'redet' (universe)
redex: command not found
hesam: redex (master) $

You don't need to separately clone folly; it's included as a submodule of redex. Just do:
git clone https://github.com/facebook/redex.git
cd redex
git submodule update --init
and then configure/make according to the instructions.

there is a difference regard instructions you see in fbredex and what you see in Github redex page. Please follow what Github page says for make and install.
autoreconf -ivf && ./configure && make
sudo make install
Regard my above problem, A developer from Redex team called me and after few minutes he found and solved the problem. He has updated FAQ section on Redex page that you can see at here. Since there is no explanation there I copy/paste what he said on chat.
So, as an optimization, the runtime linker doesn't actually go
trawling through everything to look for libs anymore It uses the cache
file, which is generated by ldconfig
Update
I forgot to mention that you must have ANDROID_SDK in your PATH. I have following paths in my .profile. Don't forget to source it after making change in it. ~/android/sdk is path to my Android SDK directory.
export ANDROID_HOME=~/android/sdk
export ANDROID_SDK=${ANDROID_HOME}
export PATH=${PATH}:$ANDROID_HOME/tools:$ANDROID_HOME/platform-tools

Buildozer error : Command failed: ./distribute.sh -m "kivy" -d "randomapp"

I have a simple project written in python (kivy) and i am using buildozer to make .apk file for Android platform. But for some reason the compiling it's not sucessufull. I think it's a problem with the pythoh-for-android module because it gives me the error:
# Command failed: ./distribute.sh -m "kivy" -d "randomapp"
#
# Buildozer failed to execute the last command
# The error might be hidden in the log above this error
# Please read the full log, and search for it before
# raising an issue with buildozer itself.
# In case of a bug report, please add a full log with log_level = 2
But when i added log_level = 2 , i see that it says that lpng is missing:
/home/shakle17/shakle/rand0m/.buildozer/android/platform/python-for-android/bui/home/shakle17/.buildozer/android/platform/android-ndk-r9c/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.8/../../../../arm-linux-androideabi/bin/ld: error: cannot find -lpng
collect2: error: ld returned 1 exit status
I am using Fedora23 and i've installed all libraries (libpng , libpng-devel for x64 and i686 platform) in the dnf package manager but still the problem remains .

I've fixed it . I've installed libpng from the official site, than run : buildozer android clean and after that it was fixed