Building/Running Android Goldfish kernel

Among the tasks for build an Android kernel development, building the Android Goldfish kernel is the easiest :-) (I mean, no compiling errors...)

First, you need to have access to the cross-compiling tools. The Android source code provides them in folder /prebuilt/linux-x86/toolchain/. 

Steps


1. Set the path to include the pre-build toolchain
   # export PATH=/prebuilt/linux-x86/toolchain/arm-eabi-4.4.3/bin/:$PATH
2. Set the Kernel config file. In this case, we are compiling for the ARM emulator (armv7).
   # make ARCH=arm goldfish_armv7_defconfig
3. Run make
   # CROSS_COMPILE=/prebuilt/linux-x86/toolchain/arm-eabi-4.4.3/bin/arm-eabi- ARCH=arm make
4. Change var ANDROID_PRODUCT_OUT
   # export ANDROID_PRODUCT_OUT=/out/target/product/generic/
5. Run the emulator
   # /out/host/linux-x86/bin/emulator-arm -system /out/target/product/generic/system.img -kernel /goldfish/arch/arm/boot/zImage -data /out/target/product/generic/userdata.img -ramdisk /out/target/product/generic/ramdisk.img -skindir /sdk/emulator/skins/ -skin HVGA -verbose -show-kernel

Issues

• The option CONFIG_MODULES is NOT enabled by default. If you want to insert modules into the kernel, make sure to set CONFIG_MODULES;
• Android emulator does NOT work with Kernels > 2.6.X So, make sure to use the proper Kernel. For devices, any support Kernel will work.

Building Android ICS

To compile ICS (and probably any new version of Android platform >= 4.0), you
might have some problems with the compilation tools.

• Follow the instructions described on http://source.android.com/source/building.html
• It also provides information about Android Kernel building.
• Check which compiler best fits into the version of Android platform you are using.
• Usually, due to new features (for example, C++11 support on GCC/++ 4.7), it is a bit more complicated to build it with new compilers... you will see several compiling errors. For example, for the ICS, GCC/++ 4.6 works better than GCC/++ 4.7.
• You may need some changes in order to compile it properly (mostly on Makefile). Again, depending on your compiler, you may apply more or less changes on your code.
• For ICS, GCC/++ 4.6 works better.

This link provides a good discussion about it (and solutions!). In my case, for compiling ICS, I made only a few changes (see below) and I also used GCC/++ 4.6.

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

project build/

diff --git a/core/combo/HOST_linux-x86.mk b/core/combo/HOST_linux-x86.mk

index 5ae4972..7df2893 100644

--- a/core/combo/HOST_linux-x86.mk

+++ b/core/combo/HOST_linux-x86.mk

@@ -53,6 +53,6 @@ HOST_GLOBAL_CFLAGS += \

  -include $(call select-android-config-h,linux-x86)

 # Disable new longjmp in glibc 2.11 and later. See bug 2967937.

-HOST_GLOBAL_CFLAGS += -D_FORTIFY_SOURCE=0

+HOST_GLOBAL_CFLAGS += -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=0

 HOST_NO_UNDEFINED_LDFLAGS := -Wl,--no-undefined

project dalvik/

diff --git a/vm/native/dalvik_system_Zygote.cpp b/vm/native/dalvik_system_Zygote.cpp

index 31fecfd..b3b745a 100644

--- a/vm/native/dalvik_system_Zygote.cpp

+++ b/vm/native/dalvik_system_Zygote.cpp

@@ -19,6 +19,7 @@

  */

 #include "Dalvik.h"

 #include "native/InternalNativePriv.h"

+#include "sys/resource.h"

 #include

 #include

project development/

diff --git a/tools/emulator/opengl/host/renderer/Android.mk b/tools/emulator/opengl/host/renderer/Android.mk

index 55fcb80..613179c 100644

--- a/tools/emulator/opengl/host/renderer/Android.mk

+++ b/tools/emulator/opengl/host/renderer/Android.mk

@@ -6,6 +6,8 @@ $(call emugl-import,libOpenglRender)

 LOCAL_SRC_FILES := main.cpp

 LOCAL_CFLAGS    += -O0 -g

+LOCAL_LDLIBS += -lX11

+

 #ifeq ($(HOST_OS),windows)

 #LOCAL_LDLIBS += -lws2_32

 #endif

project external/gtest/

diff --git a/include/gtest/internal/gtest-param-util.h b/include/gtest/internal/gtest-param-util.h

index 5559ab4..0af13b0 100644

--- a/include/gtest/internal/gtest-param-util.h

+++ b/include/gtest/internal/gtest-param-util.h

@@ -39,6 +39,7 @@

 #include

 #include

+#include

 #if GTEST_HAS_PARAM_TEST

diff --git a/src/Android.mk b/src/Android.mk

index 2465e16..1d93ac8 100644

--- a/src/Android.mk

+++ b/src/Android.mk

@@ -49,7 +49,7 @@ LOCAL_SRC_FILES := gtest-all.cc

 LOCAL_C_INCLUDES := $(libgtest_host_includes)

-LOCAL_CFLAGS += -O0

+LOCAL_CFLAGS += -O0 -fpermissive

 LOCAL_MODULE := libgtest_host

 LOCAL_MODULE_TAGS := eng

@@ -67,7 +67,7 @@ LOCAL_SRC_FILES := gtest_main.cc

 LOCAL_C_INCLUDES := $(libgtest_host_includes)

-LOCAL_CFLAGS += -O0

+LOCAL_CFLAGS += -O0 -fpermissive

 LOCAL_STATIC_LIBRARIES := libgtest

project external/llvm/

diff --git a/llvm-host-build.mk b/llvm-host-build.mk

index 5219efd..cc91ee0 100644

--- a/llvm-host-build.mk

+++ b/llvm-host-build.mk

@@ -44,6 +44,8 @@ LOCAL_C_INCLUDES := \

 LOCAL_IS_HOST_MODULE := true

+LOCAL_LDLIBS := -lpthread -ldl

+

 ###########################################################

 ## Commands for running tblgen to compile a td file

 ###########################################################

project external/oprofile/

diff --git a/libpp/format_output.h b/libpp/format_output.h

index b6c4592..8e527d5 100644

--- a/libpp/format_output.h

+++ b/libpp/format_output.h

@@ -91,7 +91,7 @@ protected:

  symbol_entry const & symbol;

  sample_entry const & sample;

  size_t pclass;

- mutable counts_t & counts;

+ counts_t & counts;

  extra_images const & extra;

  double diff;

  };

project frameworks/base/

diff --git a/libs/utils/Android.mk b/libs/utils/Android.mk

index 638f72f..127cad9 100644

--- a/libs/utils/Android.mk

+++ b/libs/utils/Android.mk

@@ -61,7 +61,7 @@ LOCAL_SRC_FILES:= $(commonSources)

 LOCAL_MODULE:= libutils

-LOCAL_CFLAGS += -DLIBUTILS_NATIVE=1 $(TOOL_CFLAGS)

+LOCAL_CFLAGS += -DLIBUTILS_NATIVE=1 $(TOOL_CFLAGS) -fpermissive

 LOCAL_C_INCLUDES += external/zlib

 ifeq ($(HOST_OS),windows)

diff --git a/tools/aapt/Android.mk b/tools/aapt/Android.mk

index a3e5d9a..4c415d6 100644

--- a/tools/aapt/Android.mk

+++ b/tools/aapt/Android.mk

@@ -28,7 +28,7 @@ LOCAL_SRC_FILES := \

     ZipFile.cpp

-LOCAL_CFLAGS += -Wno-format-y2k

+LOCAL_CFLAGS += -Wno-format-y2k -fpermissive

 LOCAL_C_INCLUDES += external/expat/lib

 LOCAL_C_INCLUDES += external/libpng

project frameworks/compile/slang/

diff --git a/Android.mk b/Android.mk

index fce3637..8ffe68f 100644

--- a/Android.mk

+++ b/Android.mk

@@ -19,7 +19,7 @@ ifeq ($(TARGET_BUILD_APPS),)

 LOCAL_PATH := $(call my-dir)

-local_cflags_for_slang := -Wno-sign-promo -Wall -Wno-unused-parameter -Werror

+local_cflags_for_slang := -Wno-sign-promo -Wall -Wno-unused-parameter

 ifneq ($(TARGET_BUILD_VARIANT),eng)

 local_cflags_for_slang += -D__DISABLE_ASSERTS

 endif

Android (Goldfish) kernel development

Finally, back to this :-)

Lately, I have being developing a new project which basically needs some kernel changes on Android Goldfish kernel. Initially, I thought that this would be something like "traditional" kernel development, but NOT. Android kernel is, of course, a Linux kernel but it has some peculiarities that impact on the development phase.

[NOTE] I'd rather provide a link to the source that I used than replicating the same information.

So, I split my experience into the following topics:

1. Building Android ICS
2. Building/Running Android Goldfish kernel 
3. Creating a Goldfish kernel module
4. Adding new syscalls into the Goldfish kernel