sgx-perf: A Performance Analysis Tool for Intel SGX Enclaves

1. Summary

Motivation of this paper

• Motivation

  • understanding the performance implications of SGX and the offered programming support is still in its infancy.

    • time-consuming trial-and-error testing and poses the risk of poor performance.
    • current methods (e.g., VTune) cannot support empowering users to implement well-performing applications.

SGX-Perf

• SGX architecture

  • Trusted Runtime System (TRST) and Untrusted Runtime System (URTS) handle the enclave transitions and call dispatching.

  • Enclave performance considerations

    • enclave transitions: 8,600 and 14,000 cycles

      • need to reduce the number of enclave transitions

    • in-enclave synchronization

      • as sleeping is not possible inside enclave,

        • in-enclave synchronization primitives provided by the SGX SDK implement additional ocalls to sleep outside the enclave.

    • enclave paging

      • EPC: one metadata page, its code, the heap and a thread-data page (TCS), stack and state-save-area (SSA) pages for each configured enclave thread.
      • added enclave transitions to handle page faults
      • extra computation needed for cryptographic operations

• SGX problems and solutions

  • The overhead of using enclaves

    • the number of enclave transitions during execution and their duration
    • the number of paging events: page fault + encryption

  • Reducing the number of enclave transitions should be prioritized.

  • Design trade-offs

    • TCB size and security issue
    • reordering should be first considered in the performance optimization.

• sgx-perf design

  • tracing ecalls and ocalls: change the symbols of wrapper codes.

    • logger
    • tracing in-enclave synchronization

Implementation and Evaluation

• Evaluation

  • Key question:

    • what is the overhead of running an application with sgx-perf?

      • the overhead of logger

    • can sgx-perf detect optimization opportunities in systems that use Intel SGX?

  • evaluation application

    • TaLos: crypto library

    • SecureKeeper: a key-value store

    • SQLite

    • LibreSSL partitioned with Glamdring

      • automated partition code

1. performance overhead of logging
2. optimization of enclaves

2. Strength (Contributions of the paper)

1. summary identified performance critical factors of SGX
2. present sgx-perf, a collection of tools for high-level dynamic performance analysis of SGX-based application.

perform fine-grained profiling of performance critical events in enclave also provide recommendations on how to improve enclave performance

3. show how to use sgx-perf to improve the SGX-based application performance.

3. Weakness (Limitations of the paper)

4. Some Insights (Future work)

1. how to optimize the enclave performance?

asynchronous calls extended memory management support

2. EPC protection All enclave memory is fully and transparently encrypted as well as integrity protected.
3. Security enhancements It is necessary to reduce the attack surface of their interfaces.

public ecall: can always be called private ecall: can only be called during an ocall

the attacker may change the control path of the execution of the program and gain access to enclave secrets.