[LLVMdev] Building sanitizers for Android (original) (raw)

Evgeniy Stepanov eugeni.stepanov at gmail.com
Fri Mar 28 00:39:15 PDT 2014

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 CMAKEINSTALLPREFIX. 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 .. _ _-DCMAKEINSTALLPREFIX=ship _ _-DCMAKECCOMPILER=arm-linux-androideabi-gcc _ _-DCMAKECXXCOMPILER=arm-linux-androideabi-g++ _ _-DCMAKEPREFIXPATH=pwd/../../llvm/out/ship _ _-DANDROID=1 _ _-DCMAKESYSTEMNAME=Linux _ _-DCMAKECFLAGS=--sysroot=$(ndkDir)/platforms/android-19/arch-arm _ -DCMAKECXXFLAGS=--sysroot=$(ndkDir)/platforms/android-19/arch-arm ... $ ninja install ... [68/68] -- Install configuration: "Release" -- Installing: ship/include/sanitizer/asaninterface.h -- Installing: ship/include/sanitizer/commoninterfacedefs.h -- Installing: ship/include/sanitizer/dfsaninterface.h -- Installing: ship/include/sanitizer/linuxsyscallhooks.h -- Installing: ship/include/sanitizer/lsaninterface.h -- Installing: ship/include/sanitizer/msaninterface.h -- Installing: ship/include/sanitizer/tsaninterfaceatomic.h -- Installing: ship/asanblacklist.txt -- Installing: ship/bin/asandevicesetup Thanks, Greg

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