MemoryMte.cpp arm64 linux build failure

[omnium21]

I'm having a problem building perfetto for linux on arm64.
I've tried building on my x86_64 Ubuntu 20.04 host machine and from inside both Ubuntu 18.04 and 20.04 docker containers with the same results.

I'm currently at this commit:
2724a3642 (HEAD -> master, origin/master, origin/HEAD) Merge "Avoid busy empty loop"

Here are the steps I've distilled from the docs:

git clone https://android.googlesource.com/platform/external/perfetto/
cd perfetto/
tools/install-build-deps --linux-arm
tools/gn gen --args="target_os = \"linux\" target_cpu=\"arm64\" is_debug=false is_clang=true" out/linux
tools/ninja -C out/linux

The failure is here:

$ tools/ninja -C out/linux
ninja: Entering directory `out/linux'
[226/3131] compile ../../buildtools/android-unwinding/libunwindstack/MemoryMte.cpp
FAILED: obj/buildtools/android-unwinding/libunwindstack/libunwindstack.MemoryMte.o 
../../buildtools/linux64/clang/bin/clang++ --target=aarch64-linux-gnu --sysroot=../../buildtools/debian_sid_arm64-sysroot -MMD -MF obj/buildtools/android-unwinding/libunwindstack/libunwindstack.MemoryMte.o.d -D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS -D_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS -DNDEBUG -DNO_LIBDEXFILE_SUPPORT -DPERFETTO_IMPLEMENTATION -I../../buildtools/android-unwinding/libunwindstack/include -I../../buildtools/android-unwinding/libunwindstack -I../../buildtools/android-libbase/include -I../../buildtools/android-logging/liblog/include -I../../buildtools/android-libprocinfo/include -I../../buildtools/android-core/include -I../../buildtools/android-core/libcutils/include -I../../buildtools/bionic/libc/async_safe/include -I../../buildtools/bionic/libc/platform -I../../buildtools/lzma/C -I../.. -I../../src/profiling/memory/include -I../../include -Igen/build_config -Igen -DFAKE_LOG_DEVICE=1 -fstrict-aliasing -Wformat -g -fPIC -fstack-protector-strong -Werror -fcolor-diagnostics -fdiagnostics-show-template-tree -Wno-c99-designator -fno-omit-frame-pointer -O3 -fdata-sections -ffunction-sections -isystem ../../buildtools/android-unwinding/libunwindstack/include -isystem ../../buildtools/android-libprocinfo/include -isystem ../../buildtools/android-libbase/include -isystem ../../buildtools/android-core/demangle/include -fno-exceptions -fno-rtti -nostdinc++ -isystem../../buildtools/libcxx/include -isystem../../buildtools/libcxxabi/include -std=c++17      -c ../../buildtools/android-unwinding/libunwindstack/MemoryMte.cpp -o obj/buildtools/android-unwinding/libunwindstack/libunwindstack.MemoryMte.o
../../buildtools/android-unwinding/libunwindstack/MemoryMte.cpp:33:14: error: use of undeclared identifier 'PTRACE_PEEKMTETAGS'
  if (ptrace(PTRACE_PEEKMTETAGS, pid_, reinterpret_cast<void*>(addr), &iov) != 0 ||
             ^
../../buildtools/android-unwinding/libunwindstack/MemoryMte.cpp:49:8: error: use of undeclared identifier 'mte_supported'
  if (!mte_supported() || !Read(addr, &data, 1)) {
       ^
2 errors generated.
[235/3131] compile ../../buildtools/googletest/googletest/src/gtest-all.cc
ninja: build stopped: subcommand failed.

A more complete log can be found here: https://pastebin.com/yivwmaN7

If I hack around the PTRACE_PEEKMTETAGS error, then next error is about ptrace:

../../buildtools/android-unwinding/libunwindstack/MemoryMte.cpp:33:7: error: no matching function for call to 'ptrace'
  if (ptrace(0, pid_, reinterpret_cast<void*>(addr), &iov) != 0 ||
      ^~~~~~
../../buildtools/debian_sid_arm64-sysroot/usr/include/aarch64-linux-gnu/bits/ptrace-shared.h:132:17: note: candidate function not viable: no known conversion from 'int' to 'enum __ptrace_request' for 1st argument
extern long int ptrace (enum __ptrace_request __request, ...) __THROW;
                ^

Any help would be appreciated.

[primiano]

Hmm weird. mte_supported is defined in buildtools/bionic/libc/platform/bionic/mte.h

These errors are relative to the unwinder, which is only for callstack sampling and heap profiling.

As a workaround, can you try passing enable_perfetto_traced_perf=false enable_perfetto_heapprofd=false ? That should stop building the unwinding library.

@rsavitski @ddiproietto in case they have more thoughts. Not sure why this would fail only when targeting arm64 (likely something sysroot related)

[primiano]

okay I can repro as well.
I think the real issue is that MemoryMte.cpp in libunwindstack does:

#ifdef __BIONIC__
#include <bionic/mte.h>
#endif
...
#if defined(__aarch64__)
...
  if (!mte_supported()

Those ifdefs should really be

#if __BIONIC__ && defined(__aarch64__)

@ddiproietto can you send a patch upstream to libunwindstack (and roll it in perfetto?) when you have some spare time?

[omnium21]

Thanks for investigating so quickly.
I can confirm that your suggestion fixes the build.
Your fix sounds about right too.

[ddiproietto]

https://r.android.com/1918189 and https://r.android.com/1926318 have been submitted. This should be fixed now.