[LLVMdev] Building sanitizers for Android

[Greg Fitzgerald]

> 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.


> 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.

-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