[LLVMdev] Building sanitizers for Android

[Evgeniy Stepanov]

On Thu, Mar 27, 2014 at 10:18 PM, Greg Fitzgerald <garious at gmail.com> wrote:
>> Alexey's approach with CMake sub-projects.
>
> I prefer that direction as well, but what I've proposed is a solution
> that works today.  To support cross-compilation, we'll need to loop
> over each supported arch (llvm-config --targets-built), then loop over
> each supported triple for each arch (hard-coded map?), and then pair
> up each triple with a sysroot (system paths provided by the user).
>
>
>> I think it already copies
>> compiler-rt build products to the parent build directory, right?
>
> The Android compiler-rt build does this, but in an unnecessarily
> complex way.  My proposal is a simplification of that process.  What
> is described in "llvm/cmake/platforms/Android.cmake" is to build
> llvm+clang for the host architecture and then run a second build to
> cross-compile llvm+compiler-rt to get a the ASan shared object and
> test suite.  Instead, I propose building only llvm for the host
> architecture (for the purpose of building llvm-config) and then only
> compile compiler-rt for Android.  No need to build clang or to
> cross-compile llvm.
>
>
>> Requiring that llvm is installed complicates things.
>
> Sorry for the confusion.  By "llvm install directory", I don't mean to
> install llvm to the root directory.  I'm referring to the intermediary
> directory pointed to by CMAKE_INSTALL_PREFIX.  When you run "ninja
> install", the build populates this directory with only the libs,
> headers, docs, and executables that the LLVM build intends customers
> to use directly.  In the case of compiler-rt, we need LLVM's
> "bin/llvm-config" to determine the build mode, flags, and targets
> available.

Yes, so "ninja install" is optional. This should work with LLVM build
directory just as well.

>
>
>> This should not be too hard to fix.
>
> Porting the LLVM build to Android?  That seems like a more challenging
> solution than to cut out the unused cross-compiled llvm build.

Note that ASan tests on Android require llvm-symbolizer binary.
Building just compiler-rt for the target would not be enough.

>
> -Greg
>
> On Thu, Mar 27, 2014 at 1:14 AM, Evgeniy Stepanov
> <eugeni.stepanov at gmail.com> wrote:
>> I'd prefer something based on Alexey's approach with CMake
>> sub-projects. I think it already copies compiler-rt build products to
>> the parent build directory, right?
>>
>> Requiring that llvm is installed complicates things.
>>
>> On Thu, Mar 27, 2014 at 5:00 AM, Greg Fitzgerald <garious at gmail.com> wrote:
>>> The build for the Android sanitizers is unique in that it needs to
>>> link against the Android system libraries to create a shared object
>>> and its test suites.  The current solution to build ASan is to drop
>>> the compiler-rt repo into the llvm source tree and cross-compile the
>>> llvm build for Android.  This is a bit awkward for few reasons:
>>>
>>> 1) Not all of llvm can be cross-compiled for Android.  "ninja all"
>>> causes expected build errors.
>>
>> This should not be too hard to fix.
>>
>>> 2) The sanitizers don't depend on any LLVM libraries, only llvm-config
>>> for its build configuration.
>>> 3) No "install" rule.  Instead, you cherry-pick files from the build directory.
>>>
>>> Building against the LLVM install directory cleans this up nicely and
>>> as it turns out, this mostly works today (see CMake configuration
>>> below).  The only missing pieces are that the shared object is not
>>> added to the install directory and the test suites are not built.  Is
>>> this a build configuration you'd consider using?
>>>
>>> $ cmake -G Ninja .. \
>>>     -DCMAKE_INSTALL_PREFIX=ship \
>>>     -DCMAKE_C_COMPILER=arm-linux-androideabi-gcc \
>>>     -DCMAKE_CXX_COMPILER=arm-linux-androideabi-g++ \
>>>     -DCMAKE_PREFIX_PATH=`pwd`/../../llvm/out/ship \
>>>     -DANDROID=1 \
>>>     -DCMAKE_SYSTEM_NAME=Linux \
>>>     -DCMAKE_C_FLAGS=--sysroot=$(ndkDir)/platforms/android-19/arch-arm \
>>>     -DCMAKE_CXX_FLAGS=--sysroot=$(ndkDir)/platforms/android-19/arch-arm
>>> ...
>>> $ ninja install
>>> ...
>>> [68/68]
>>> -- Install configuration: "Release"
>>> -- Installing: ship/include/sanitizer/asan_interface.h
>>> -- Installing: ship/include/sanitizer/common_interface_defs.h
>>> -- Installing: ship/include/sanitizer/dfsan_interface.h
>>> -- Installing: ship/include/sanitizer/linux_syscall_hooks.h
>>> -- Installing: ship/include/sanitizer/lsan_interface.h
>>> -- Installing: ship/include/sanitizer/msan_interface.h
>>> -- Installing: ship/include/sanitizer/tsan_interface_atomic.h
>>> -- Installing: ship/asan_blacklist.txt
>>> -- Installing: ship/bin/asan_device_setup
>>>
>>> Thanks,
>>> Greg