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Commit a8b9aa63 authored by Jack He's avatar Jack He
Browse files

GD-HCI: Flush snoop log to kernel buffer on every write 

* std::ofstream::flush() pushes user data into kernel memory. The data
  will be written even if this process crashes. However, data will be lost
  if there is a kernel panic, which is out of scope of BT snoop log.
* std::ofstream::write() followed by std::ofstream::flush() has similar
  effect as UNIX write(fd, data, len) as write() syscall dumps data into
  kernel memory directly
* Before this change, btsnoop log data might be partially stored in
  memory when bluetooth stack crashes, causing broken log entries
  or missing packets

Bug: 164973960
Test: make, flash phone, and test pairing
Tag: #gd-refactor
Change-Id: I611e0b9480511b569dadbb023775b0db8159f39d
parent d0ab2373

system/gd/hal/snoop_logger.cc

+9 −4
Original line number Diff line number Diff line
@@ -166,6 +166,9 @@ void SnoopLogger::OpenNextSnoopLogFile() { 
  if (!btsnoop_ostream_.write(reinterpret_cast<const char*>(&kBtSnoopFileHeader), sizeof(FileHeaderType))) {

    LOG_ALWAYS_FATAL("Unable to write file header to \"%s\", error: \"%s\"", file_path_.c_str(), strerror(errno));

  }

  if (!btsnoop_ostream_.flush()) {

    LOG_ERROR("Failed to flush, error: \"%s\"", strerror(errno));

  }

}



void SnoopLogger::SetFilePath(std::string filename) {
@@ -219,13 +222,15 @@ void SnoopLogger::Capture(const HciPacket& packet, Direction direction, PacketTy 
    if (!btsnoop_ostream_.write(reinterpret_cast<const char*>(packet.data()), packet.size())) {

      LOG_ERROR("Failed to write packet payload, error: \"%s\"", strerror(errno));

    }

    if (os::ParameterProvider::SnoopLogAlwaysFlush()) {

    // std::ofstream::flush() pushes user data into kernel memory. The data will be written even if this process

    // crashes. However, data will be lost if there is a kernel panic, which is out of scope of BT snoop log.

    // NOTE: std::ofstream::write() followed by std::ofstream::flush() has similar effect as UNIX write(fd, data, len)

    //       as write() syscall dumps data into kernel memory directly

    if (!btsnoop_ostream_.flush()) {

      LOG_ERROR("Failed to flush, error: \"%s\"", strerror(errno));

    }

  }

}

}



void SnoopLogger::ListDependencies(ModuleList* list) {

  // We have no dependencies

system/gd/os/android/parameter_provider.cc

+0 −4
Original line number Diff line number Diff line
@@ -28,9 +28,5 @@ std::string ParameterProvider::SnoopLogFilePath() { 
  return "/data/misc/bluetooth/logs/btsnoop_hci.log";

}



bool ParameterProvider::SnoopLogAlwaysFlush() {

  return false;

}



}  // namespace os

}  // namespace bluetooth
 
 No newline at end of file

system/gd/os/host/parameter_provider.cc

+0 −4
Original line number Diff line number Diff line
@@ -44,9 +44,5 @@ std::string ParameterProvider::SnoopLogFilePath() { 
  return std::string(cwd) + "/btsnoop_hci.log";

}



bool ParameterProvider::SnoopLogAlwaysFlush() {

  return true;

}



}  // namespace os

}  // namespace bluetooth
 
 No newline at end of file

system/gd/os/parameter_provider.h

+0 −3
Original line number Diff line number Diff line
@@ -28,9 +28,6 @@ class ParameterProvider { 


  // Return the path to the default snoop log file location

  static std::string SnoopLogFilePath();



  // Flag to allow flush into persistent memory on every packet captured. This is enabled on host for debugging

  static bool SnoopLogAlwaysFlush();

};



}  // namespace os