mirror of
https://github.com/intel/linux-sgx
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Li, Xun
35 lines
1.9 KiB
Markdown
35 lines
1.9 KiB
Markdown
# sgx_switchless
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sgx_switchless is a collection of *switchless features*, which can eliminate *enclave transitions* from SGX applications. This branch of the codebase only includes **Fast ECalls/OCalls**.
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## Motivation
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In a running SGX application, enclave transitions occur whenever the CPU switches between enclave and non-enclave mode (e.g., user mode or privileged mode). Enclave transitions are *extremely expensive*: on the current hardware platform, the overhead of an enclave transition is measured to be *60X more expensive* than that of switching between user and privileged mode (typically, when making system calls).
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From the perspective of SGX developers, the only way to trigger enclave transitions from inside enclaves is via OCalls. And it is this OCall mechanism that--- behind the scene--- enables the users to synchronize between SGX threads (see `sgx_threads.h`), request application-specific services from outside the enclave and perform I/O operations with the untrusted environment. Therefore, SGX applications that heavily depend on OCalls may suffer a considerable performance degradation due to enclave transitions.
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## How to Use
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sgx_switchless has been built and tested on Ubuntu 16.04. For now, it does not support 32-bit CPUs or SGX simulation mode.
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### Build
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Run the following command in directory `/sdk/switchless`
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$ make
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to build two libraries of sgx_switchless: the trusted library `libsgx_tswitchless.a` and the untrusted library `libsgx_uswitchless.so`. Users should link the two libraries to the object files for trusted and untrusted components, respectively.
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### Test
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Run the following command at `/sdk/switchless/test`
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$ make && make test
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to compile and run the test cases.
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### Sample Code
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See the sample project at `/SampleCode/FastOCalls`. To compile and run the sample project correctly, SGX SDK and PSW with Switchless SGX should be compiled and installed.
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