1. TEE-Perf A Profiler for Trusted Execution Environments
Maurice Bailleu, Pramod Bhatotia
Donald Dragoti, Christof Fetzer
Thanks for the introduction!
In this talk, I will present Speicher: a secure storage system for untrusted hosts.
Speicher exports a persistent KV interface based on the LSM data structure.
To provide strong security properties, Speicher leverages shielded execution based on Intel SGX.
  This is a joint work with Joerg Thalheim and Pramod Bha to tia from the University of Edinburgh.
And we collaborated with Christof Fetzer from TU Dresden, MH from NEC Labs, and KV from MSR Cambridge.
Transition: Let me start with the motivation of our project!
Code available:

2. Trusted Execution Environments
Address space
Secure memory
region (or enclave)
Trusted
Execution
Environment
Security in untrusted infrastructure: 
How to establish trust in the untrusted computing infrastructure?
Trusted Execution Environment (TEE):
Hardware extension to provide secure memory region
Protects application code and data against a powerful adversary (e.g. malicious OS/VMs)
Trusted
application
Security in untrusted environment

3. Trusted Execution Environments
Different implementations:
Different ISAs
Different OSs
Architectures: Intel SGX, ARM TrrustZone, Keystone
Wide range of TEE available, with different
A wide range of TEEs available that are supported by different platforms

4. Performance problems inside TEEs
TEE implementation details:
Memory encryption overhead
Switches between un-/trusted environments
Syscalls (I/O operations) are prohibited 
Different characteristics for different TEEs 
Take away point at the end not the beginning
Code running inside an TEE has surprisingly different performance characteristics

5. Research gap: Profiling for TEEs
TEE environment:
No HW counter
No I/O
OS cannot inspect processor state
Architecture or platform dependent
Describe laundry
Makes it hard to adapt existing profiling tools

6. Our contribution Properties:
TEE-perf: An architecture and platform-independent tool to measure performance on function level for application running inside a TEE
Properties:
Generality
Architecture- and platform-independent
Transparency
Unmodified multi-threaded application
Easy-to-use interface
Accuracy
Accurate method-level profiling
No instruction sampling
Full stop

7. Outline Design Motivation Challenges Evaluation
- In the last part, I presented …
- Next,  I will talk about ...

8. Challenge #1: HW counter unavailability
Hardware counters
Not available inside TEEs
Architecture dependent
Acquire from the untrusted host
Requires switch between un-/trusted environments
Mapping a counter into the secure memory

9. Challenge #2: Application inspection
Sampling by interrupting periodically
Interrupts are expensive
TEEs prevent observing the CPU
Use function instrumentation to measure the code while executing

10. Challenge #3: Getting measurements data
Communication over channels
Channels require to leave TEEs
TEE exit operations are expensive since they  require TLB flushing, security checks, etc.
Trusted enclave
I/O call
Exit enclave to issue the syscall
Introducing a shared-memory log in the host memory

11. Challenge #4: Log format
Measurement information are not human readable
Tools do not understand the format
Designed an offline analyzer that allows queries on the measurements and export data to other tools

12. Outline
Motivation
Challenges
Design
Evaluation

13. System overview #1
Compiler #2
Recorder #3
Analyzer #4
Visualizer

14. Compiler takes unmodified code and produces a binary for measurements
Stage 1: Compiler
Compiler takes unmodified code and produces a binary for measurements
Inject code
Function instrumentation
Call/Ret
Map code
Communication
Recorder

15. Stage 2: Recorder Host memory Enclave
Recorder uses the instrumented binary to measure the execution and writes the profiled info to the shared-memory log
Host memory
Enclave
Fn(A)
Fn(B)
Recorder
Call B
Write log
Software Counter
Call B
Write log
Ret
Ret
Log Header
Record 1
Record 2 …

16. Stage 2: Log format Log header Log entry #1 Log entry #2
Append-only log allows lock-free appends, and small entries reduce log size 
Log header
Log entry #1
Log entry #2
Call/Ret
Counter value
Call/Ret
Counter value
Instruction address
Instruction address
Thread ID
Thread ID

17. Analyzer takes the log and presents retrieved information to the user
Stage 3: Analyzer
Analyzer takes the log and presents retrieved information to the user
Call stack for each thread
Calculates time spent per method
Human readable
Declarative query interface

18. Takes an Analyzer run and produces a Flamegraph
Stage 4: Visualizer
Takes an Analyzer run and produces a Flamegraph
Add a flamegraph
An example flame graph produced by TEE-perf

19. Outline
Motivation
Challenges
Design
Evaluation

20. Evaluation Questions: Experimental setup:
What are the profiling overheads of TEE-Perf?
Does TEE-Perf detect performance optimization
opportunities?
Experimental setup:
Intel Xeon E v5 (3.60 GHz, 4 cores, 8 hyper-threads) -- Skylake w/ SGX
64GiB RAM 
See the paper
for more results
Explain the questions – Say more evaluation in the paper
Experimental setup – Say for completeness
(Skylake CPU with SGX support and Intel SSD with SPDK support)

21. Q1 : Overhead of TEE-perf
Say the evaluation question
Say the X-axis: On x-axis
 Say the Y-axis: On x-axis
 Say how to interpret the plot: Higher the better
Say the  variants: Speicher and Native
Explain the results. You tell the average and then explain the corner cases, e.g. min and max.
Summarize: The evaluation question with answer – Takeaway
The Takeaway: 
TEE-Perf has an mean overhead of 1.9x compared to perf

22. Q2: Detecting optimization opportunities
Case study porting SPDK to Intel SGX:
14.4x slowdown of naively ported version
TEE-perf showed that:
72% of the time was spent in getpid syscall
20% of the time was spent in getting a timestamp
After optimization SPDK performance is on par with native
Explain the questions – Say more evaluation in the paper
Experimental setup – Say for completeness
(Skylake CPU with SGX support and Intel SSD with SPDK support)
TEE-perf is able to detect performance critical sections 

23. Summary
TEE-perf: An architecture and platform independent profiling tool for trusted execution environments (TEEs)
Our tool is
General: architecture and platform independent
Transparent: supports unmodified multi-threaded applications 
Accurate: provides method-level profile w/o instruction sampling
Code available: