1.
Thomas Moulard tmoulard@amazon.com
Raising the Bar on Robotics
Code Quality
08/01/2019
Tooling and Methodology for Robotics Software Teams
building critical ROS 2 Applications

2.
Table of contents
• Raising the bar on open-source code quality?
• Code Instrumentation: ASAN/TSAN
• ClangThread Safety Extensions
• Fuzzing ROS 2

3.
What is AWS RoboMaker?
• AWS Cloud9 simplify ROS development
• Cloud Simulation accelerate robot validation
• Fleet Management provide over the air update
capabilities to a robotic fleet.
• Cloud Extensions easily interface ROS with AWS
services such as Amazon Lex, Amazon Polly,
Amazon Kinesis Video Streams, Amazon
Rekognition, and Amazon CloudWatch.
aws.amazon.com/robomaker
Hello world
Navigation and person recognition
Voice commands
Robot monitoring
Sample Applications

4.
Testing Robots is hard
• Errors are critical: a single bug can break a robot.
• Software input is uncontrolled.
• Experimenting with hardware is slow.
• Software is tightly coupled to hardware.
• System behavior depends on a large number of
parameters which need to be tuned.
Finding bugs in a robotic system is time consuming and
bugs have a high impact.
…
(Any) Server
One robot serves a few users, deploying
software is hard.
One server serves a lots of users,
deploying software is easier.

5.
Raising the Bar on Open-Source Code Quality
Ensuring Code Quality for OSS is challenging:
• Shared Ownership
• Decision Making slower/harder
• Stakeholders are hard to identify
• End-to-End Testing?
Which strategy for your robotic team?
1. Fork?
2. Contribute back?
3. Both?
Are you facing difficulties running ROS 1/2 in production
→ Talk to us!

6.
Solution: better developer infrastructure!
1. We cannot review all PRs,
2. We cannot maintain all the packages
…but we can build tooling!
Automatic Code Analysis and CI running it automatically
is crucial to code quality.
Enable the community to work together on eliminating
defects:
• Memory Issues
• Concurrency Issues
• Performance
AWS CodeBuild

7.
Compiler Instrumentation

8.
Automating C++ Code Defect Discovery
ASAN/MSAN Valgrind Dr. Memory Mudflap Guard Page gperftools
Technology CTI DBI DBI CTI Library Library
ARCH x86, ARM, PPC
x86, ARM, PPC,
MIPS, …
x86 All (?) All (?) All (?)
OS
Linux, OS X,
Windows, …
Linux, OS X, Solaris,
…
Windows,
Linux
Linux, Mac (?) All (?)
Linux,
Windows
Slowdown 2x 20x 10x 2x-40x ? ?
Heap OOB yes yes yes yes some some
Stack OOB yes no no some no no
Global
OOB
yes no no ? no no
UAF yes yes yes yes yes yes
UAR yes no no no no no
UMR yes (MSAN) yes yes ? no no
Leaks yes yes yes ? no yes
Source: https://github.com/google/sanitizers/wiki/AddressSanitizerComparisonOfMemoryTools

9.
AdressSanitizer (ASan) Overview
Detect a large variety of memory defects:
• Out-of-bounds accesses to heap, stack and globals
• Use-after-free
• Use-after-return
• Use-after-scope
• Double-free, invalid free
Integrated with recent version of Clang and GCC:
-fsanitize=address
Only find bugs in executed code paths.
New! On ARM64, HWASAN is even more efficient.
Source: https://android-developers.googleblog.com/2017/08/android-bug-swatting-with-sanitizers.html

10.
ThreadSanitizer (TSan) Overview
Detect concurrency-related defects:
• Potential deadlocks
• Race conditions
• Unsafe signal callback - see man signal-safety(7)
Integrated with recent version of Clang and GCC:
-fsanitize=thread
void signal_handler() {
// Will fail and set errno to ABCD
my_function_modifying_errno();
if (errno == ABCD) { /* do something */ }
}
int main() {
install_signal_handler(&signal_handler);
// Will fail and set errno to EFGH:
my_other_function_modifying_errno();
// A signal is received!
// signal_handler() gets executed here.
// This gets executed:
if (errno == ABCD) {
/* do something */ }
// ...but this should have been executed:
else if (errno == EFGH) {
/* do something else */ }
}

11.
Compiling ROS 2 with ASAN / TSAN
# Initial Setup
sudo apt-get install python3-colcon-mixin
colcon mixin add default
https://raw.githubusercontent.com/colcon/colcon-mixin-repository/master/index.yaml
colcon mixin update default
# Workspace Compilation (ASAN)
cd ~/ros2_asan_ws
colcon build --build-base=build-asan --install-base=install-asan
--cmake-args
-DOSRF_TESTING_TOOLS_CPP_DISABLE_MEMORY_TOOLS=ON
-DINSTALL_EXAMPLES=OFF -DSECURITY=ON --no-warn-unused-cli
-DCMAKE_BUILD_TYPE=Debug
--mixin asan-gcc
--packages-up-to test_communication
--symlink-install
# Workspace Compilation (TSAN)
cd ~/ros2_tsan_ws
colcon build --build-base=build-tsan --install-base=install-tsan
--cmake-args -DOSRF_TESTING_TOOLS_CPP_DISABLE_MEMORY_TOOLS=ON
-DINSTALL_EXAMPLES=OFF -DSECURITY=ON --no-warn-unused-cli
-DCMAKE_BUILD_TYPE=Debug
--mixin tsan
--packages-up-to test_communication
--symlink-install

12.
ROS 2 CI Integration
ci.ros2.org > Nightly > *_sanitizer
Catch regressions early!
Only run rcpputils and rcutils unit tests.
Will expend the scope of those jobs as more
and more packages get fixed!
We are looking for volunteers to help us fix
those bugs!

13.
Thread Safety Annotations

14.
Thread Safety Annotation
• Clang + libclangcxx required.
• Detect concurrency issues at compile time.
• Need to annotate classes attributes and functions.
• But does not require full instrumentation (can be
migrated progressively!)
• Need to pass specific flag: -Wthread-safety
Race conditions are hard to find during code reviews.
It can take very long before the bug is triggered on a
production platform.
Start annotating your code today!
Real life ROS 2 example:
rmw_fastrtps_shared_cpp/topic_cache.hpp
#include "mutex.h"
class BankAccount {
private:
Mutex mu;
int balance GUARDED_BY(mu);
void depositImpl(int amount) {
balance += amount; // WARNING! Cannot write balance
without locking mu.
}
void withdrawImpl(int amount) REQUIRES(mu) {
balance -= amount; // OK. Caller must have locked mu.
}
public:
void withdraw(int amount) {
mu.Lock();
withdrawImpl(amount); // OK. We've locked mu.
} // WARNING! Failed to unlock mu.
void transferFrom(BankAccount& b, int amount) {
mu.Lock();
b.withdrawImpl(amount); // WARNING! Calling withdrawImpl()
requires locking b.mu.
depositImpl(amount); // OK. depositImpl() has no
requirements.
mu.Unlock();
}
};
Source: https://clang.llvm.org/docs/ThreadSafetyAnalysis.html

15.
Fuzzing ROS 2

16.
ROS 2 Fuzzing
ROS 2 is writing and loading lots of data:
• Config files: YAML, XML
• ROS bags
• URDFs
• Messages (serialization/unserialization)
• Etc.
Fuzzing is essential (and easy!).
This naive script relies on radamsa to generate ROS 2
messages was able to crash the ros2 cli!
#!/usr/bin/env bash
i=0
for word in $(aspell -d en dump master | aspell -l en
expand | head -n 5); do
echo "{data: "${word}"}" > "/tmp/sample-${i}"
i=$((i+1))
done
pgrep listener || exit 0
while true; do
STR=$($HOME/radamsa/bin/radamsa /tmp/sample-*)
echo "$STR"
(ros2 topic pub --once /chatter
std_msgs/String "${STR}" 2>&1) > /dev/null
test $? -gt 127 && break # break on segfaults
pgrep listener || break
done
echo "SEGV"

17.
What’s next?
UndefinedBehaviorSanitizer (UBSan) integration:
• bool
• integer-divide-by-zero
• return
• returns-nonnull-attribute
• shift-exponent
• unreachable
• vla-bound
Integrate Clang Control–Flow Integrity?
Annotate ROS 2 code with the Thread Safety Annotations.
Need ot fix ROS 2 Linux clang build with libclangcxx!
Expend testing to more than core packages!

18.
Thank you!