libstapsdt is a library which allows creating and firing Systemtap's USDT
probes at runtime. It's inspired on
chrisa/libusdt. The goal of this
library is to add USDT probes functionality to dynamic languages.
Table of Contents
- Table of Contents
- How it works
- Run tests
- Write your own wrapper
How it works
Systemtap's USDT implementation allows only statically defined probes because
they are set as ELF notes by the compiler. To create probes at runtime,
libstapsdt takes advantage of shared libraries: it creates a small library
with an ELF note and links it at runtime. This way, most existing tools will
keep working as expected.
libstapsdt currently requires the following dependencies:
- libelf (from elfutils)
sudo apt install libelf1 libelf-dev
sudo dnf install elfutils-libelf-devel
To build and install libstapsdt, just run:
make sudo make install sudo ldconfig
There's a demo program available. To build it, run:
make demo # Executable will be available at ./demo
./demo PROVIDER_NAME PROBE_NAME
After running the demo program, it can be instrumented with proper tools.
Here's an example using eBPF/bcc trace tool (built from source):
sudo /usr/share/bcc/tools/trace -p $(pgrep demo) 'u::PROBE_NAME'
To run tests, just run the command below. Please be aware that there are only a few tests for now, but more will be added in the future.
Here is a list of wrappers for other languages:
Write your own wrapper
libstapsdt is written in C, which makes it very portable to almost any
language. Most dynamic languages provide a way to wrap C code. Feel free to
develop a wrapper in your language of choice. If you do, please let us know to
update our wrappers list!