[libcxx-commits] [PATCH] D102912: [libunwind] AARCH64 use inline assembly for pointer authentication

Fri Jun 3 02:29:22 PDT 2022

kitaisreal added a comment.
Herald added a project: All.

@danielkiss it seems that this patch fixes libunwind build for arm for old llvm versions, and also removes dependency on local register variables feature. Should not we apply it ?
Reproducible crash scenario for clang-11.

  cat /etc/os-release
  NAME="Ubuntu"
  VERSION="20.04.4 LTS (Focal Fossa)"
  ID=ubuntu
  ID_LIKE=debian
  PRETTY_NAME="Ubuntu 20.04.4 LTS"
  VERSION_ID="20.04"
  HOME_URL="https://www.ubuntu.com/"
  SUPPORT_URL="https://help.ubuntu.com/"
  BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
  PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
  VERSION_CODENAME=focal
  UBUNTU_CODENAME=focal

  uname -a
  Linux ip-172-31-37-142 5.13.0-1022-aws #24~20.04.1-Ubuntu SMP Thu Apr 7 22:14:11 UTC 2022 aarch64 aarch64 aarch64 GNU/Linux

  arch
  aarch64

Download clang-11 using llvm.sh

  wget https://apt.llvm.org/llvm.sh
  chmod +x llvm.sh
  sudo ./llvm.sh 11

clang version

  clang++-11 --version
  Ubuntu clang version 11.0.0-2~ubuntu20.04.1
  Target: aarch64-unknown-linux-gnu
  Thread model: posix
  InstalledDir: /usr/bin

  /usr/bin/clang-11 --version
  Ubuntu clang version 11.0.0-2~ubuntu20.04.1
  Target: aarch64-unknown-linux-gnu
  Thread model: posix
  InstalledDir: /usr/bin

Now lets reproduce bug

  #include <stdint.h>

  uintptr_t __attribute__ ((noinline)) authenticatePtrKeyB(uintptr_t pointer, uintptr_t modifier)
  {
      register unsigned long long x17 __asm("x17") = pointer;
      register unsigned long long x16 __asm("x16") = modifier;

      asm volatile("hint 0xe" : "+r"(x17) : "r"(x16)); // autib1716
      pointer = x17;

      return pointer;
  }

  int main(int argc, char **argv)
  {
      uintptr_t value_to_take = 5;
      uintptr_t ptr_to_value = reinterpret_cast<uintptr_t>(&value_to_take);
      authenticatePtrKeyB(ptr_to_value, 3);

      return 0;
  }

Compile with clang++-11

  /usr/bin/clang++-11 -O0 register_example.cpp -o register_example
  PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace, preprocessed source, and associated run script.
  Stack dump:
  0.	Program arguments: /usr/lib/llvm-11/bin/clang -cc1 -triple aarch64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name register_example.cpp -mrelocation-model static -mframe-pointer=non-leaf -fmath-errno -fno-rounding-math -mconstructor-aliases -target-cpu generic -target-feature +neon -target-abi aapcs -fallow-half-arguments-and-returns -fno-split-dwarf-inlining -debugger-tuning=gdb -resource-dir /usr/lib/llvm-11/lib/clang/11.0.0 -internal-isystem /usr/bin/../lib/gcc/aarch64-linux-gnu/9/../../../../include/c++/9 -internal-isystem /usr/bin/../lib/gcc/aarch64-linux-gnu/9/../../../../include/aarch64-linux-gnu/c++/9 -internal-isystem /usr/bin/../lib/gcc/aarch64-linux-gnu/9/../../../../include/aarch64-linux-gnu/c++/9 -internal-isystem /usr/bin/../lib/gcc/aarch64-linux-gnu/9/../../../../include/c++/9/backward -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-11/lib/clang/11.0.0/include -internal-externc-isystem /usr/include/aarch64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O0 -fdeprecated-macro -fdebug-compilation-dir /home/ubuntu -ferror-limit 19 -fno-signed-char -fgnuc-version=4.2.1 -fcxx-exceptions -fexceptions -fcolor-diagnostics -faddrsig -o /tmp/register_example-8aae67.o -x c++ register_example.cpp 
  1.	<eof> parser at end of file
  2.	Code generation
  3.	Running pass 'Function Pass Manager' on module 'register_example.cpp'.
  4.	Running pass 'RegBankSelect' on function '@_Z19authenticatePtrKeyBmm'
  #0 0x0000ffff9775a9fc llvm::sys::PrintStackTrace(llvm::raw_ostream&) (/lib/aarch64-linux-gnu/libLLVM-11.so.1+0xa5c9fc)
  clang: error: unable to execute command: Segmentation fault (core dumped)
  clang: error: clang frontend command failed due to signal (use -v to see invocation)
  Ubuntu clang version 11.0.0-2~ubuntu20.04.1
  Target: aarch64-unknown-linux-gnu
  Thread model: posix
  InstalledDir: /usr/bin
  clang: note: diagnostic msg: 
  ********************

  PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
  Preprocessed source(s) and associated run script(s) are located at:
  clang: note: diagnostic msg: /tmp/register_example-814e11.cpp
  clang: note: diagnostic msg: /tmp/register_example-814e11.sh
  clang: note: diagnostic msg: 

  ********************

Compile with clang-11

  /usr/bin/clang-11 -O0 register_example.cpp -o register_example
  PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace, preprocessed source, and associated run script.
  Stack dump:
  0.	Program arguments: /usr/lib/llvm-11/bin/clang -cc1 -triple aarch64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name register_example.cpp -mrelocation-model static -mframe-pointer=non-leaf -fmath-errno -fno-rounding-math -mconstructor-aliases -target-cpu generic -target-feature +neon -target-abi aapcs -fallow-half-arguments-and-returns -fno-split-dwarf-inlining -debugger-tuning=gdb -resource-dir /usr/lib/llvm-11/lib/clang/11.0.0 -internal-isystem /usr/bin/../lib/gcc/aarch64-linux-gnu/9/../../../../include/c++/9 -internal-isystem /usr/bin/../lib/gcc/aarch64-linux-gnu/9/../../../../include/aarch64-linux-gnu/c++/9 -internal-isystem /usr/bin/../lib/gcc/aarch64-linux-gnu/9/../../../../include/aarch64-linux-gnu/c++/9 -internal-isystem /usr/bin/../lib/gcc/aarch64-linux-gnu/9/../../../../include/c++/9/backward -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-11/lib/clang/11.0.0/include -internal-externc-isystem /usr/include/aarch64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O0 -fdeprecated-macro -fdebug-compilation-dir /home/ubuntu -ferror-limit 19 -fno-signed-char -fgnuc-version=4.2.1 -fcxx-exceptions -fexceptions -fcolor-diagnostics -faddrsig -o /tmp/register_example-035369.o -x c++ register_example.cpp 
  1.	<eof> parser at end of file
  2.	Code generation
  3.	Running pass 'Function Pass Manager' on module 'register_example.cpp'.
  4.	Running pass 'RegBankSelect' on function '@_Z19authenticatePtrKeyBmm'
  #0 0x0000ffffb54469fc llvm::sys::PrintStackTrace(llvm::raw_ostream&) (/lib/aarch64-linux-gnu/libLLVM-11.so.1+0xa5c9fc)
  clang: error: unable to execute command: Segmentation fault (core dumped)
  clang: error: clang frontend command failed due to signal (use -v to see invocation)
  Ubuntu clang version 11.0.0-2~ubuntu20.04.1
  Target: aarch64-unknown-linux-gnu
  Thread model: posix
  InstalledDir: /usr/bin
  clang: note: diagnostic msg: 
  ********************

  PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
  Preprocessed source(s) and associated run script(s) are located at:
  clang: note: diagnostic msg: /tmp/register_example-afe67d.cpp
  clang: note: diagnostic msg: /tmp/register_example-afe67d.sh
  clang: note: diagnostic msg: 

  ********************

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D102912/new/

https://reviews.llvm.org/D102912