Demo capture API use for later replay

Demo API capture for replay

Summary

The project builds two libraries

• libxrt_coreutil.so
• libxrt_capture.so

Application code (sample in capture/test/main.cpp) links with libxrt_coreutil as normal. To capture API calls use LD_PRELOAD with libxrt_capture

Code organization

Mirrors code from https://github.com/Xilinx/XRT.

capture
├── CMakeLists.txt
├── LICENSE
├── README.md
├── core
│   ├── capture
│   │   ├── CMakeLists.txt
│   │   └── capture.cpp
│   ├── common
│   │   ├── CMakeLists.txt
│   │   └── api
│   │       ├── capture.h
│   │       └── xrt_device.cpp
│   └── include
│       └── xrt
│           ├── CMakeLists.txt
│           └── xrt_device.h
└── test
    ├── CMakeLists.txt
    └── main.cpp

The capture library is built from core/capture into libxrt_capture and linked with libxrt_coreutil.

The capture implementation redefines the XRT API symbols defined in libxrt_coreutil which needs to be captured into a time line, for example xrt::device APIs are defined in libxrt_capture.

The idea is that if libxrt_capture is loaded before libxrt_coreutil then the defintion of exported APIs will come from libxrt_capture. The implementation of the APIs in libxrt_capture will do what it needs to do in terms of capturing the API calls and then call into libxrt_coreutil for the actual implementation of the APIs.

To avoid recursive calls into libxrt_capture, the calls from this library into libxrt_coreutil must be into wrapper functions that immediately calls the public API implementation. These wrappers are implemented in the same compilation units that define the actual public APIs (e.g. xrt_device.cpp).

Since all public XRT objects are implemented in an opaque pimpl, the wrappers can create a real XRT object and just steal the opaque impl. So any XRT object created from libxrt_capture will be a valid object that can be used with our without going through the capture library.

The library libxrt_coreutil is built with -Bdynamic link option which ensure that symbols referenced in libxrt_coreutil are resolved within this library and wont recurse to libxrt_capture.

Building

Build using CMake from root directory.

% mkdir build
% cd build
% cmake ..
% cmake --build . --config Debug --verbose --target install

This builds libxrt_coreutil, libxrt_capture, and main test executuble.

Run

Run the test making sure LD_LIBRARY_PATH can find libxrt_coreutil then run as

% ldd main
	linux-vdso.so.1 (0x00007fff353e9000)
	libxrt_coreutil.so => /mnt/c/Users/stsoe/git/stsoe/capture/build/lib/libxrt_coreutil.so (0x00007fe8411c4000)
	libstdc++.so.6 => /lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007fe840fd0000)
	libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007fe840fb5000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fe840dc3000)
	libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fe840c74000)
% main
xrt::device_impl::device_impl(0)
xrt::device::device(0)
xrt::device::load_xclbin(foo.xclbin)
xrt::device::~device()
xrt::device_impl::~device_impl()

Capture

Use LD_PRELOAD to preload libxrt_capture.

% env LD_PRELOAD=$PWD/lib/libxrt_capture.so bin/main
xrt::device_impl::device_impl(0)
xrt::device::device(0)
xrt::device::~device()
capture|xrt::device::device(0)
capture|xrt::device::load_xclbin(foo.xclbin)
xrt::device::load_xclbin(foo.xclbin)
capture|xrt::device::~device()
xrt::device_impl::~device_impl()

% env LD_PRELOAD=$PWD/lib/libxrt_capture.so bin/main |grep capture
capture|xrt::device::device(0)
capture|xrt::device::load_xclbin(foo.xclbin)
capture|xrt::device::~device()